Index


Notes from Author (Warning:) This is a work in progress that, in large parts, is (still) loosely based on rather old literature such as "The Spiders and Allied Orders of the British Isles" (Theodore H. Savory, 1945). Please be aware that some of the names, taxonomy and even characters that are given for identification may not reflect the most up to date standard of knowledge (yet)!
Over time, all information will be checked against modern literature and corrected if need be. Soon, the colour red will be used to mark passages that are in need of further investigation.


Order OPILIONES.

STRUCTURE and HABITAT. - The body of a harvestman is not only so characteristic that the animals are easy to recognize; it is also unique, or at least it is unlike the body of any other Arachnid. The cephalothorax is composed of six somites and it bears the six pairs of appendages common to the whole Class. In the abdomen ten somites may with difficulty be recognized. There are no appendages; moreover, the tergite, above, and the sternite, below, of the same segment are not always placed vertically opposite to each other.

This is the unique peculiarity. It may be described by saying that the fore-edge of the first sternite has been dragged forward until it has reached the line of the coxae of the second pair of legs. This has dragged forward the sternites behind it, has brought the anus from from its primitive terminal position to a ventral one, and has bent downwards some of the posterior tergites. In consequence, the tergite primitively above the anus now lies behind it, and the sternite primitively below the anus lies in front of it. There is no other Arachnid like this. It is a fundamental reason why most Opiliones have short round bodies, while most of their allies are long and narrow.

On the upper surface of the cephalothorax the most conspicuous feature is the ocular tubercle, placed not far from the fore-edge. It carries two simple eyes, placed back to back so they stare sideways with the unblinking gaze of a fish. At the sides, close to the coxae of the second pair of legs, the openings of a pair of odoriferous glands are visible. These glands, which secrete an irritating or nauseous liquid, are characteristic of the Harvestmen and are found in no other Arachnida. The glands themselves can be seen in some species, showing through the carapace as dark spherical objects, and more than once they have been mistakingly described as a second pair of eyes.
Rilaena triangularis with parasitic nymphs of predatory Mites
The region between the ocular tubercle and the fore-edge, which may be called the clypeus, is generally covered with pointed spines. These may be scattered over the area; but in sub-family Oligolophinae three of them are placed conspicuously in front, forming a trident which is characteristic of the group. The relative lengths and positions of the trident spines is often helpful in determining the species [Fig. 2.].

Trident shapes of various species
Fewer features are noticeable on the upper surface of the abdomen, where transverse grooves or rows of spicules indicate segmentation. In the families Trogulidae and Nemastomatidae it is covered by a single chitinous shield composed of the fused tergites of the cephalothorax and first five or six abdominal segments. As a result one finds that the whole dorsal surface can be removed, and mounted for examination, whereas nothing of the sort is possible with the softer species.

There is in many harvestmen a central dark band which forms a good example of that kind of pattern which provides it with a degree of inconspicuousness against its natural background, by breaking up the outline or obvious appearance of the animal`s shape.
As in spiders, the lower surface of the body shows much more detail than the upper. In front it is composed of the eight coxae, the gnathobases of the pedipalpi and anterior legs and the genital operculum, projecting forwards from the abdomen. This is really composed of the fused sternites of the second and third abdominal segments. The first sternite is represented by a pair of chitinous plates lying in front of or outside of the operculum and called the arculi genitales. They are the most easily distinguishable in Homalenotus. Four sternites follow the operculum, numbering 4, 5, 6 and 7. The arrangement of the eighth and ninth is different in the different families; the tenth is absent.
The chelicerae are composed of three strongly chitinized segments, the third of which works against a prolongation of the second to form a pair of sharply pointed forceps. There are no poisonous-glands within; the limbs themselves move freely in a longitudinal direction with the forceps, working transversely, to tear to pieces the harvestman`s food.
The pedipalpi are like short legs. They have six segments - coxa, trochanter, femur, patella, tibia and tarsus. They are used in manipulating the food and their setae are probably organs of touch. The coxa bears a gnathobase which works against its fellow and helps to crush the food.

Pedipalp
By the systematist the pedipalpi are used in characterizing the families accordingly to the relative length of the tibia and tarsus and the character of the tarsal claw when present.
Thus :
  1. No claw ----------------- Trogulidae and Nemastomatidae
  2. Toothed claw ---------- Sclerosomatinae and Leiobunidae
  3. Smooth claw ----------- Oligolophinae and Phalangiinae
Harvestmen, unlike spiders, do not have the complex sex-organs in the male pedipalpi, but a hitherto undescribed sex difference is found in nearly all the British species. This is a group of short spicules on the outer side of the male tarsus.
The legs are composed of seven segments, the same as the pedipalpi plus a metatarsus. The coxae of the first legs carry gnathobases which assist in mashing the food; the coxae of the second pair also carry gnathobases in some genera, but they do not appear to be normally used in feeding. The other segments sometimes show false articulations and this is especially true of the tarsus which, in the longest legs, may consist of more than a hundred pieces. The legs all end in a plain claw. The tarsi may be quickly twisted around grass-stems as the animal runs; to assist the cylinders of chitin which make up the tarsus are longer above than below and a muscle running from the claw to the metatarsus coils up the segment.

False articulation

In some harvestmen the tibiae of the legs have accessory breathing spiracles, leading to the tracheal system. Very little is known, however, about the respiration of these animals.

The bodies and limbs of all harvestmen are more or less covered with spines or setae of different appearances, and probably of different functions. As far as outward appearance goes, these dermal structures can be divided into four groups, which may well be named as follows :
  1. Teeth (denticulae or spicules) are more or less sharp conical projections of the exoskeleton, such as occur on the abdominal tergites of Nemastoma.
  2. Spines are hollow cylindrical outgrowths, usually sharply-pointed, such as occur on the hood of Trogulidae, the pedipalpi of Rilaena, and which form the trident of Oligolophinae.
  3. Setae are the solid bristle-like objects such as occur on the legs and generally more familiar on the legs of spiders, where they are supposed to have a tactile function.
  4. Trichobothria (or hairs) are much finer than setae and are found on the tarsi and other leg segments of some species; they may be erect or may lie flat like the true hairs of a mammal. In spiders, long erect trichobothria are supposed to have an acoustic function.
The sexes of harvestmen are not very different from each other. Males as a rule have longer legs and smaller bodies. The sex organs are not normally visible but they may easily be made to protrude by gently squeezing the body, when they appear at the tip of the genital operculum. The ovipositor is a broad tube, the penis is finely pointed.

It is as a rule only by careful searching that one can find harvestmen in England in the Spring. In March and April captures are of three kinds - Mitostoma chrysomelas and Homalenotus quadridentatus, which can be found at all seasons; aged specimens of Phalangium opilio or Opilio parietinus, which have had the rare fortune to survive winter; and juvenile specimens of Rilaena triangularis or Megabunus diadema. The Phalangiumand the Opilio, if brought into the laboratory, prove to be very inactive and soon die of old age. Rilaena and Megabunus hatch form their eggs in fall and pass the winter as small juveniles. In spring they moult and grow rapidly and are mature in May. By the end of June Rilaena is hardly to be found out of doors, but in captivity they are known to last until August.

Their place is taken by Leiobunum, young specimens of which begin to be seen in early June. They mature by the end of July and are very plentiful in hedgerows during August and September. In the laboratory they survive until January or later.
Phalangium appears soon after Leiobunum and is usually the most conspicuous of all British species in the late summer. It seems generally to disappear, often rather suddenly, during October.
It is closely followed by Oligolophus, Paroligolophus, Odiellus and Mitopus.
These species are constantly moulting throughout June and August. They are mature in September and October and are the dominant genera of the latter month, but the lower temperatures of November bring them to an end out of doors. In cages I have known Odiellus to survive until 26th January. Last of the British species is Opilio parietinus, which lingers on into November when the rest have disappeared.

The hibernation of a few species is interesting : Harvestmen are much more resistant to cold than heat. More than once, I have suffered the loss of captive specimens when by inadvertence there cage has been left where the sun could shine on it. The result is the death of all specimens in a comparatively short time. On the other hand records show that Nelima aurantica has been found under snow. Some of these were put out over-night in a box, the temperature of which fell to -20c. The animals became torpid, with there legs stretched vertically upwards in a close bundle, but when placed on a warm hand, they recovered in a few moments.
I have found similar torpid specimens of Mitostoma chrysomelas in January, which could be instantly re-awakened by breathing gently upon them. Taken indoors they became quite lively and mated with each other as if it had been early spring.

The general behaviour of all harvestmen is a pattern of reflexes and tropisms with scarcely a suggestion that any consciousness determines there actions. They seem to be even more mechanistic than spiders, for a spider catching a fly or courting a mate does present an outward appearance of purposiveness, which many biologists have liberally interpreted, while a harvestman never seems to respond to anything save obviously external stimuli.

For example, they are strongly photogenic and collect in the darkest corners of there cage. This is particularly true of young specimens. Direct light checks movement, so that many species are not active during the day; but Mitopus, Phalangium and Megabunus are less nocturnal than others.
Harvestmen also react quickly to the movement of an image across the retina of the eye. If one`s two hands are moved up and down at the sides of a harvestman, the animal rises and falls on its long legs in a remarkable and rather ludicrous manner. A cage full of Leiobunum is particularly sensitive in this respect and will react to the movement of one`s head if one stoops to look at them. The formally quiescent creatures are suddenly galvanized into activity : they race round and round the cage, their bodies rising and falling and striking the box, tap-tap-tap as they go, until after a few seconds they all settle down again into there usual somnolence.

Harvestmen respond keenly to moisture. They are very dependent on water, and in houses are often found in baths and wash-basins, just as spiders are, attracted there during there nightly wanderings and discovered, unable to escape, in the morning. Moisture also guides them to a spot suitable for egg laying, as will appear later.

Harvestmen share with many other animals the tendency to creep into contact with solid surfaces, called stereo tropism and generally rest in the corners of the cage. The species Odiellus spinosus in particular shows this behaviour, and if there are five or six specimens in a box together will rest during the daytime all pressed together in a corner.
The response to chemical compounds is also well developed and occasionally brings harvestmen to the notice of entomologists, for they may be among visitors to the patches of sugar spread out at night to attract moths.

The study of harvestmen is a study of legs. Of the eight characteristically long legs, the first, third and fourth are habitually used for walking, while the legs of the second pair, which in all British species are the longest, are generally stretched out in front, tapping the ground and clearly acting as organs of touch. A moving harvestman often stops and touches the ground ahead with its second legs before proceeding; and a resting harvestmen may be seen moving its second legs about as if they were constant sentinels against the approach of danger. I have seen a quiescent harvestman respond to the banging of my laboratory door by raising its second legs with a sudden jerk. I have seen a thirsty harvestman put its fourth leg into water, turn and touch the water with its second leg before moving forward to drink.

A harvestman that has lost one of these longest legs does not appear to be seriously handicapped, but if both legs are lost its behaviour is very different. There are no rapid movements, no hastening to eat, drink or mate. A harvestman so mutilated among a number of others resembles nothing so much as a blind man feeling his way among a crowd of headless companions.

It is a remarkable fact that limbs so vital to the animals well-being should be so easily lost, and when lost should never be restored. yet such is the case. A harvestman sheds its legs on the least provocation, so that it is hardly an exaggeration to say that at the end of the autumn one finds fewer harvestmen with a full compliment of eight legs than with any other. Specimens with only two legs can run quite rapidly.

As has long been known, a leg forcibly removed or automized continues for some while to jerk spasmodically at the tibial-metatarsal joint. This curious detail has received a delightfully teleological explanation. It is imagined that the foe grips the hunted harvestman by the leg, the limb is thus detached, and by its repeated jerkings so occupies the attention of the predator that the harvestman has time to escape. This is therefore the "purpose" of the jerks!

Like spiders, harvestmen carefully clean their legs. A leg is held in the chelicerae, which open and shut as the long joints are pulled through them. By the time the tarsus is reached the leg is almost bent into a circle, and it finally shoots out like a bent spring. The pedipalpi are cleaned in the same way. The chelicerae themselves are largely cleansed by washing in the drinking water, and in a cage food-particules and other debris collect in the vessal, which must be scoured at intervals.

The food of harvestmen is varied, nor need it be living at the time of capture, in nature it would seem probable that harvestmen could scarcely rely on finding sufficient dead materials to supply their needs, for the dead bodies of small animals are uncommon in the undergrowth where harvestmen live, and no doubt exists that much of a harvestman's food is caught and killed by itself. The strength of the cheliceral muscles is considerable; they have been known to easily lift half a gram.
When the food is obtained the pedipalpi rest upon it, the chelicerae are sunk into it and slowly move up and down, detaching small fragments. Unlike spiders, harvestmen are more inclined to feed little and often, though one meets occasional exceptions to this. I have know a young Mitopus, which was evidently hungry when captured, to eat almost a whole Clubionid spider at one sitting and as a result to swell up exactly as a spider would have done in similar circumstances. Another, a male Rilaena, to which I gave a dead Lycosa lugubris, spent four hours eating the spider. At the end of this time there was only a scrap of skin left of the abdomen, the legs, chelicerae and pedipalpi were detached and in part sucked dry, and the carapace was polished clean inside. This particular harvestman ate a second spider six hours later.

Though they appear to be ill-provided with weapons of attack, harvestmen have a remarkable and efficient method of defense. The existence of odoriferous glands in the cephalothorax has already been mentioned, but the fact that their secretion is not very noticeable to the human nose prevented for many years a general recognition of there function. Recently the glands and their function have been the subject of a paper by Lawrence. He has observed that some species can either expel the mixture rapidly in the form of a fine jet, or more slowly as a large drop accumulating at the orifice of the gland. He makes it quite clear that secretion is a defense action, a response to irritation of the animal either by pressure on its body or by seizing its limbs. Among European species recorded instances of the use of this gland are few. Stripperger writes that of the many hundreds of harvestmen captured by her, only one, a male Gyas, was seen to secrete a small drop of liquid from one gland while she held it. An offensive odour lasted for two minutes.

It is possible, but not certain, that the secretion produced may be responsible for the anaesthesia which overcomes a crowd of harvestmen in some conditions. It is my custom when working in the garden to keep to hand an empty jam-pot and to drop into it all harvestmen that I meet. When these are brought indoors to the laboratory they seem to be aneasthetized, intoxicated or narcotized by each other. While they remain close together at the bottom of the vessel the state of insensibility persists, but very soon after they're thrown out on to the floor of the cage they recover and move away.

One of the commonest methods of protection in spiders, the habit often spoken of as "shamming dead", seems to be very rare among harvestmen. I have, however, been told by Dr. R. F. Lawrence that some African species will show this cataleptic state. When grasped by the hand or forceps they become completely rigid. There legs may often be bent so as to assume the most extravagant positions, which they will maintain for several minutes at a time. For example, the legs may all be turned upwards and the animal inverted and stood with its ventral surface uppermost, its body resting on its legs as on a "tripod" of eight parts.

At all times harvestmen are subject to attacks of parasite and to the adherence of of passengers that use them as a means of transport. Commonest among the parasites is the small red mite, Belaustium (Ritteria) nemorum, which often occurs on other animals as well. These mites hold on by there probosces to the body or legs, and often three, four or five mites maybe found on the same harvestman. Internal parasite, such as nematode worms and gregarines, also occur.

The phenomenon known as phorecy or the use of other animals as a means of transport is illustrated by the little false-scorpion Chernes nodosus, which may sometimes be found holding to the legs of flies. It does not very often make use of the harvestman in this way, but in September 1936 I caught on successive days two specimens of Opilio each carrying one of these small passengers.
Rilaena juvenile freshly moulted, still carrying old skin around

Like spiders and other Arthropoda, harvestmen grow by a periodic casting of "skin" or exoskeleton. The harvestman hands itself up by its fourth legs and begins a series of convulsive wriggles which split the skin. The chelicerae and the femora of the legs immediately spring out of the gap, followed by the rest of the body, which draws the legs after it. The final freeing of the legs is done is done by the palpi and chelicerae. The former hold the bundle of legs together under the mouth and support the out-drawn limbs; the chelicerae grasp the legs and pull them out, so that the leg-bundle bows out into a circle and all the limbs are preened and kneaded by the jaws as they pass. This preening continues for some hours after the moult is accomplished.
Setae of Mitostoma
With a long series of young harvestmen that arrived in a colleague's bathroom during the spring of 1937, I noticed the interval between the moults averaged ten days. Once the animal was seen to be eating its cast skin, but this appears to be exceptional, and is certainly not the custom of harvestmen that are otherwise well fed.

Spiders and other Arthropoda often show at the time of moulting the power of regenerating limbs which have been lost. Harvestmen appear to be unique among the Arachnida in being unable to recover lost limbs in this way. Even the short pedipalpi are not reproduced in two or three moults. The wound left by the lost limb is closed and the animal remains short for the rest of its life. Stripperger observes that if a limb is lost at the trochanter in early youth, the growth of the coxa ceases and remains "like a thin sausage among its neighbours". If only the tarsal joints are lost, the rest remains in use.
It is curious that animals which lose the legs so readily should be unable to regenerate them in the same way as their relatives can. If a spider's leg is crushed or cut, the stump is seized by the chelicerae and pulled off; but harvestmen do not do this. I have met individuals with injured legs that dragged helplessly and hampered the animals movements, but which were never amputated.

One of the most striking differences between spiders and harvestmen lies in the relation between the sexes. Spiders mate rarely and give us the impression of a serious process, not without risks, to be undertaken only after elaborate courtship. Harvestmen mate freely and frequently, even in captivity; there is no courtship either visual or tactile, and the sexes unite almost as soon as they meet. Their union only occupies a few moments, and both partners, wandering on, are unlikely(likely?) to mate again, either with each other or other inhabitants of the cage. The species of (Par)Oligolophus are particularly insatiable, and when well fed spend the evening in no other occupation.

It has been reported that at the breeding season the males fight "bloodless battles" with each other, and this has been witnessed many time. I have never witnessed anything of the kind in my laboratory, even when the number of harvestmen in a cage gave opportunity and encouragement for such a display. On the contrary I have seen two Paroligolophus agrestis approach a female simultaneously, and while one of them mated with her the other stood by and awaited the opportunity of which he availed himself as soon as his rival had moved.

Harvestmen are known to lay their eggs underground. Early in August 1935 a harvestman in one of my cages laid her eggs in the water provided for drinking, and this fact led me to believe that oviposition is stimulated by moisture in much the same way as several malodorous compounds stimulate egg-laying in blow-flies. Accordingly, I placed in a cage a shallow tray of moist sand and by the end of the month found that three batches of eggs had been laid under the sand. The females usually die very soon after they have laid their eggs, but the males survive them.

The eggs are pale-green spheres, rather less than half a millimeter in diameter, not adhering to each other and not covered or protected in any way. I have found that eggs of Odiellus spinosus laid in November hatch early in the following February, producing tiny harvestmen, their bodies smaller than a pin`s head. I have fed them on moist bread-crumbs and mutton fat, which they ate, but they seem to be difficult to rear.

Classification.
The two thousand known species of harvestmen are divided into three sub-orders, only one of which, known as Palpatores, is represented in the British fauna. It has been divided into two tribes, Dyspnoi and Eupnoi, the former of which contains four families, two only of which are British, and the latter one. The separation of our harvestmen into families is therefore an easy task, accomplished thus :-

1 (2) Tarsus or pedipalp longer than tibia; pedipalpal claw well developed, second legs with gnathobases; legs with stigmata on tibiae - Tribe Eupnoi => One family (?!): Phalangiidae.
2 (1) Tarsus of pedipalp shorter than tibia; pedipalpal claw absent; second legs without gnathobases; legs without stigmata - Tribe Dyspnoi => 3.
3 (4) Cephalothorax produced forwards into a bifurcated hood covering chelicerae; eyes level with carapace => Family Trogulidae.
4 (3) Cephalothorax with no such hood; eyes on ocular tubercle => Family Nemastomatidae.
Needs key-out for family Sabaconidae!

Overview of British Species
The following is a list of the British species (based on Savory (1945) and partially updated to current status:-
  • Tribe Dyspnoi
    • Family Nemastomatidae: Centetostoma bacilliferum, Mitostoma chrysomelas, Nemastoma bimaculatum and possibly Nemastoma lugubre(??).
    • Family Sabaconidae: Sabacon viscayanum ramblaianum.
    • Family Trogulidae: Anelasmocephalus cambridgei, Trogulus tricarinatus (T. rostratus).
  • Tribe Eupnoi
    • Family Phalangiidae
      • Sub-family Dicranopalpinae: Dicranopalpus ramosus.
      • Sub-family Leiobuninae: Leiobunum blackwalli, Leiobunum rotundum, Nelima gothica.
      • Sub-family Oligolophinae: Lacinius ephippiatus, Mitopus morio (+M. morio var. ericaeus), Odiellus spinosus, Oligolophus hanseni, Oligolophus tridens, Paroligolophus agrestis, Paroligolophus meadii.
      • Sub-family Opilioninae: Opilio canestrinii Opilio parietinus Opilio saxatilis.
      • Sub-family Phalangiinae: Phalangium opilio.
      • Sub-family Platybuninae: Lophopilio palpinalis, Megabunus diadema, Rilaena triangularis.
      • Sub-family Sclerosomatinae: Homalenotus quadridentatus.
Note to self: This 'taxonomy' may need checking - many times additional families are defined - probably best to present two or three popular schemes side by side.

Dyspnoi.

Nemastomatidae.
The Nemastomatidae are more closely related to the Trogulidae than to the Phalangiidae, a fact which is expressed by uniting them in the tribe Dyspnoi. Nevertheless the British species bear superficially a closer resemblance to the common Phalangiidae than they do to the rarer Trogulidae, for they lack the forwardly directed hood, they have longer legs and their eyes are borne on an ocular tubercle. Moreover, the second segment of the chelicerae is vertical and not horizontal. Their abdomens, however, retain nine tergites and ten sternites; the last three tergites are free, while the rest are united with those of the cephalothorax to form a continuous dorsal shield, and the corona analis consists consists of four sclerites, as in the Trogulidae. Also, as in that family the pedipalpal tarsus is shorter than the tibia and has no terminal claw; while the genitalia show the shorter ovipositor and immovable glans penis.

The structural features which are characteristic of the family are the large size of the genital operculum, the existence of false articulations on the femora and the absence of the gnathites from the coxae of the second legs. The most remarkable feature is the form of the setae on the pedipalpi. These setae end in minute spherical knobs, giving them a drumstick appearance which is found in no other British harvestmen. The terminal sphere is produced by a secretion : immediately after casting of a skin the new setae are of ordinary appearance, and the spherical tip only appears after the lapse of some time. Incidentally, too, the knob is invisible on limbs mounted in Canada balsam - evidently the substance of which they are composed has the same refractive index.
Nemastoma bimaculatum under rotten log in dense woodland, in an extremely damp area (2006/2/25)

The genus Mitostoma was previously contained in Nemastoma, but the latter are black and rather short-legged, whereas in Mitostoma the legs are longer and the colour is the more usual brownish.

Nemastoma bimaculatum and Nemastoma lugubre have caused some confusion about their occurrence on the British Isles over the years. Savory (1945) lists and describes N. lugubre, but in reality only N. bimaculatum is/was recorded. His description however seems to be mostly correct for N. lugubre (?!) More recent publications (Ors01) suggest that N. lugubre might possibly be present in the east nevertheless, but overlooked. So, although to our present knowledge N. lugubre is not recorded for Britain the species is added here for reference.

The general appearance and colouring of both species makes them immediately recognizable and distinct from other genera. The small rotund body, 2.5mms. long, with rather short legs, and its prevailing black colour with two large white patches on the cephalothorax, are quite distinctive. In some specimens the patches are pale yellow, sometimes they are cream-coloured and sometimes silvery. Although somewhat variable the shape of the patches is a good indication for the species: Indented for N. bimaculatum, continous/rounded (but with a jagged edge) for N. lugubre. Both species are said to also occur, very rarely without the patches (hence totally black), which on the continent could lead to confusion with other european species such as N. dentigerum, N. bidentatum or N. triste.
Left: N. bimaculatum; Right: N. lugubre.

The abdomen is very hard above and bears transverse rows of small blunt denticulae or granulations, marking the hind edges of the tergites (but notably more so in N. lugubre than in N. bimaculatum. The legs are strong; in colour they are dark with paler metatarsi and tarsi. The dorsal side of the femora of the 4th pair of legs bears strong denticulations on N. bimaculatum females and only very few denticles on N. lugubre.

The sexes can be fairly easily distinguished by a close look at the chelicerae, as on the males these carry extra characters. On N. bimaculatum the top of the first segment of the male chelicerae has two apophyses, a bluntish process on the outside and a little teeth sticking out on the inside, on N. lugubre it's a single slightly bigger blunt process.

Double apophysis on chelicerae of male N. bimaculatum

Nemastoma bimaculatum is found everywhere in the British Isles, including the Channel Islands and Orkney and several other small islands. It also occurs on the tops of mountains at heights above 2,500 feet; and abroad it extends over the whole of Europe from the Arctic to the Mediterranean.
Grid map of records on the NBN Gateway for Nemastoma bimaculatum

Mitostoma chrysomelas
does not seem to resemble the last very closely, but like it, it is easy to recognize. Its body is 3 mms. long, but its pedipalpi are twice this length, a peculiarity that makes it at once identifiable. The peculiar knobbed setae on the pedipalpi have been mentioned above. The dorsal sclerites of the abdomen are a rich yellow-brown colour, dotted with small silvery or golden spots and carrying denticulae on the hinder edges. The legs are relatively longer than those of the last species.

Mitostoma chrysomelas may be found at all times of the year, even in midwinter. It occurs all over Britain, has been recorded from Inverness and in Wales accompanies Nemastoma to the tops of the mountains of Snowdonia. There is only one record from Ireland. Abroad, it extends all over Europe.

Group of M. chrysomelas. Inset: 2 stages of juveniles (not to scale) found at the same time.
Grid map of records on the NBN Gateway for Mitostoma chrysomelas

Sabaconidae (Ischyropsalidae?).
Although there is some discussion on the validity of the family Sabaconidae as it is argued, by Martens and others that when Dresco (1970) removed the genus Sabacon from the family Ischyropsalidae and created the family, he did not consider the whole ranges of known Sabacon nor Ischyropsalidae and the variability within the whole ranges would not render enough distinctiveness. Nevertheless many recent references such as Fauna Europaea and Pinto-da-Rocha et all, 2007 still use the family, so we'll follow that for now.

Sabacon viscayanum ramblaianum is the only species found in Britain and it was only discovered relatively recently, in the 1980's. Yet, like the continental Ischyropsalis-species, it is believed to be a relict of the "Tertiary" geologic period rather than a new introduction. Since it's discovery it has been found scattered over various sites, mostly in the south of Wales. Abbot (1981) qualifies the habitat as follows: "The species of Sabacon are found in moist, cool habitats, high altitudes or temperate climates. They prefer woodland, especially wet, shaded dingles, and can be found under decaying logs and in leaf litter. They are sometimes found in caves.".


Photograph courtesy of Roger.S.Key : Sabacon viscayanum ramblaianum
More descriptive characters to be added ...
Grid map of records on the NBN Gateway for Sabacon viscayanum subsp. ramblaianum

Trogulidae.
The Trogulidae are the most primitive harvestmen found in this country. They have always been described as very rare, but they lead inconspicuous lives generally in chalky places. A sufficiently careful search among fallen beach leaves would almost certainly reveal them in many localities in the south of England.

The chief outward character of the family is, as mentioned above, the existence of a hood extending forward from the cephalothorax and covering the chelicerae and palpi. There is no ocular tubercle, the eyes lying flat on the surface of the carapace. The body is protected above by a shield formed from the fused tergites of the cephalothorax and the first six segments of the abdomen, the posterior edge of the sixth forming the apparent end of the body as seen from above. The seventh tergite is a narrow transverse strip forming the posterior surface; the eighth and ninth lie at the sides of the anus, forming with the small oval tenth part of the corona analis.

On the ventral side the first abdominal sternite is a small vestige dorsal to the genital operculum, which is composed of the second and third sternites. This is followed by four normal and separate sternites, numbers 4 to 7. The eighth and ninth form a narrow plate in front of the anus. The tenth is missing.

The chelicerae are smaller than in other families; the second segment is directed almost horizontally instead of vertically, as is normal; and the pedipalpi show characteristic of the tribe Dyspnoi in having a short tarsus without a claw. The legs are much shorter than is usual among the Opiliones and the tarsi are composed of 2, 2, 3 and 3 pieces only. The coxae are immovable and all are fused together, forming a strong nearly semicircular piece on each side of the lower surface. Those of the first legs carry gnathobases separated from the fixed part by a strip of softer membrane which gives them some mobility. The second pair of coxae have no such gnathobases.

The reproduction are also different in this family. The ovipositor is a short broad tube, without the rings that characterize it in the Phalangiidae, and terminating in a pair of very short forceps. The penis has not the so-called "glandular" part at the end.

There are two British genera, easily distinguishable.
1 (2) Hood of large semicircular plates, with small spines on outer edge - Trogulus.
2 (1) Hood of small projections, with long cylindrical spines - Anelasmocephalus.

Trogulus tricarinatus is 6mm long, its body narrow and flattened, with short rather robust legs. Its general colour is brown, but the tarsi are darker. the single shield over its dorsal surface and the concealment of the chelicerae and pedipalpi under the hood makes this and the next unlike the other British harvestmen in general appearance. In addition it moves slowly and is habitually covered with pieces of dirt. The younger stages are a striking violet colour. It occurs only in the south of England, save for a single record in Buxton. It is commoner in Europe.


A typical Trogulus - probably nepaeformis (not a British species)
Grid map of records on the NBN Gateway for Trogulus tricarinatus

Anelasmocephalus cambridgei
is a smaller animal, 3.5mms. long, darker in colour and not so flattened in appearance. It has the same general appearance of Trogulus and is just as dirty. Both the species are probably to be found in an adult state at all seasons. Records of Anelasmocephalus have come from the south-coast as well as Surrey, Warwick and Derby, and from North and South Wales.
Image copyright Steve (Gerel)
Grid map of records on the NBN Gateway for Anelasmocephalus cambridgei


Eupnoi.

Phalangiidae
The remaining sixteen British harvestmen belong to the tribe Eupnoi. Some systemists place all British species of the tribe in one co-extensive family Phalangiidae, but in other views more families are recognized such as maybe Leiobunidae and Sclerosomatidae.

The most obvious feature which distinguishes the group are the length of the legs. The legs of the second pair, which are always the longest, are at least five times as long as the body, sometimes seven or eight times as long, and in a few species even longer than this. In addition as well as those of the first pair the second pair also carry gnathobases which are rudimentary or absent in the Dyspnoi.

More careful examination shows a further reduction in the number of somites. On the dorsal surface of the abdomen eight tergites are only present, followed by the anal operculum : on the ventral surface there are five sternites behind the genital plates. These are numbers 3 to 7, and the edge of the seventh borders the anus, which is terminal and not ventral. The first tergites are more or less closely united; the last three are free and can often be seen to be distinct and to form as it were a short triangular "tail." This however, depends on the sex of the animal, the state of repletion or hunger, and of the development of the eggs in the ovary.

In addition to these, the claw on the palpal tarsus, the teeth or setae on the palpal femur and the spur on the firs segment of the chelicerae are features which are important because they are used in separating the sub-families which the group contains.

The following table separates the Phalangiidae into its four British sub-families (needs extension!) :-

  1. (2) Pedipalpal claw toothed => 3
  2. (1) Pedipalpal claw smooth => 5
  3. (4) Abdomen with four teeth on posterior margin; openings of odoriferous glands hidden by first coxae; anus visible; gnathobases of second legs far apart => Sclerosomatinae.
  4. (3) Abdomen smooth posteriorly; opening of odoriferous glands visible; anus hidden; gnathobases of second legs in straight line; very long legs => Leiobuninae.
  5. (6) First segment of chelicerae with ventral tooth or spur; ante-ocular region with a trident of three conspicuous spines; gnathobases of seconds legs forming an obtuse angle => Oligolophinae.
  6. (5) First segment of chelicerae without spur; ante-ocular region without trident => Phalangiinae.

Sclerosomatinae.
This sub-family, though rightly place among the Phalangiidae, resembles in certain ways the families of the Dyspnoi. For example, the cephalothorax and first five abdominal segments are covered by a single shield and the segments behind the fifth are sharply bent down to form the posterior and part of the ventral surface. The true first sternite is clearly to be seen in this group, where it is represented by two plates of chitin in front of the genital operculum. The curious row of four blunt tubercles on the posterior edge of the fifth tergite make the sub-family unmistakable.

Homalenotus quadridentatus is our only species of the sub-family and is recognizable by the characteristic pattern, composed of four rows of dark squarish spots each with a lighter tubercle in the middle. The two central longitudinal rows, each of four spots, are generally more clearly marked than the row on each side, which also consists of four spots. Besides the four posterior tubercles, there is a central beak-like tooth on the fore-edge of the cephalothorax : in some some specimens it bears small lateral spines. The setae on the legs are broad and blunt, rather more like blades than spikes.
Homalenotus quadridentatus


Homalenotus quadridentatus

A variety, formerly described as a separate species, Sclerosoma romanum, has sharper tubercles on the abdomen, spines on the tibiae, and a second tooth, directed downwards, below the beak of the cephalothorax.

Homalenotus quadridentatus is a southern species, on record for ten English counties of which Worcestershire is the most northerly. It has not been found in Ireland or Scotland. Its also occurs in South Europe and North Africa.

Grid map of records on the NBN Gateway for Homalenotus quadridentatus

In this sub-family the length of the legs is at a maximum; for example, the body of a male Leiobunum rotundum is 3 or 4 mms. long and the second leg is about 60mms. long, or nearly twenty times the length of the body. The segmentation of the abdomen is almost indistinguishable, as the exoskeleton is smooth and devoid of all but the smallest denticulae. The ocular tubercle is smooth and spineless. The claw of the pedipalp, as in Homalenotus, is toothed.

The two British species of Leiobunum are very common in long grass in early autumn, and a striking feature is the speed with which they move. A harvestman when once seen does not often evade capture, but with Leiobunum closer attention than most other is called for. No harvestmen live communal lives, but Leiobunum in particular is liable to congregate in numbers where the conditions are favourable. In Devon I have found clumps of thirty or forty individuals, none of them paying much attention to the others.

Leiobuninae

Leiobunum rotundum
is at once betrayed by the length of its black legs. The body of the female, 5 to 7 mms. long, is a smooth oval shape, brown in colour, with a dark median dorsal band which is broadest posteriorly. The ocular tubercle is smooth and each eye is surrounded by a black ring.


Leiobunum rotundum, male.

Leiobunum rotundum, female.

The body of the male is smaller and more rounded, and its uniform red-brown colouring is unrelieved by an median or other marking. This species occurs all over England, Wales and Ireland, as well as the Channel islands; and extends to the canaries and to Africa.

More info and images in the Leiobunum rotundum species account.

Leiobunum blackwalli is closely allied to the foregoing, but the body of the female is usually a little smaller. It is easily distinguished by a white line or band which runs forward from the ocular tubercle to the edge of the cephalothorax, and, more conspicuously, by a white band circling each eye. The abdominal markings of the female are like those of L. rotundum, but the ground colour is often brighter.
There are no spines on the ocular tubercle, no trident is present, and a claw can be seen on the pedipalp.


Leiobunum blackwalli, female



The underside of Leiobunum blackwalli (female)



Leiobunum blackwalli, male
Leiobunum blackwalli, female.

I have known specimens so bright so that at a little distance they were at first mistaken for ladybirds.
The species almost as widespread as L. rotundum, but its actual records are not so numerous. It is found in Western Europe, but not in Africa.

Nelima gothica
This is a rare species which resembles Leiobunum closely enough to make it at once obvious that it belongs to the sub-family Leiobuninae, The genus Nelima is separated from Leiobunum by rows of little denticles on the coaxa, present in the latter and missing in Nelima. It can further be distinguished from the two foregoing species by a dark spot at the distal end of each coxa, by its pale trochanters without lateral teeth, the shorter leggs (pale brownish with yellow annulations) and by the two rows of small denticulae on the ocular tubercle.
The species wasn't recognized and described until 1945 (by Lohmander) and earlier (and some later) records of Nelima silvatica (Bristowe, 1935; Brown & Sankey, 1949) are misidentifications. So, while the two names are not synonymous, early British references of Nelima silvatica are all presumed to be in fact Nelima gothica.

Nelima gothica, adult male, December 2008. Note that the whole animal is quite dark, including the ocularium that would usually be more silvery.
Female and male, the male is in the background, this is a more typical colour for N. gothica.

Sankey (1988) has the species in Britain only on a number of 10km squares, with maybe a slight preference for coastal areas. There are no records from Northern Ireland, but some from the Republic. It seems to be recorded from quite diverse habitats, but often in grassy situations and on walls. Outside of Britain the species is known from northern Spain and France to Denmark and Sweden, but rare and scattered mostly everywhere.

Adults can be expected from July onward, but probably won't make it through the winter - their eggs will hatch in the following spring.

Dicranopalpinae
This "subfamily" is used here for just one species - Dicranopalpus ramosus which is a relatively new species of harvestman for Britain.

The systematic place seems to be somewhat 'open for discussion'. The species is also often placed in the subfamily Gyantinae within either the family Leiobunidae, or the Sclerosomatidae if either one is recognized as separate from the Phalangiidae to begin with, suggesting a close relation to Leiobunum and Nelima described above. The latest trend however seems to be to assign them to their own subfamily Dicranopalpinae, which is subsequently placed in the family Phalangiidae (?!), suggesting less of such a relationship.

Whichever 'system' may prevail, Dicranopalpus ramosus is a quite long legged species, with especially the second pair reaching up to 5 cm, stretched out sideways in a peculiar manner when resting. The bodies of the males has a length of up to 4 mm long and females up to 6 mm. The patellae of the pedipalpi carry a distinct elongated apophysis that reaches almost to the end of the tibia. This makes the pedipalpi look forked. Their body is brownish with dark markings, the females being lighter colored.


Dicranopalpus ramosus, male

The forked pedipalps and the resting posture, with the legs stretched to the sides, makes this species easy to identify, although the traditional method of collecting invertebrates does not prove adequate: of 103 individuals captured in Belgium, only one was found in a pitfall; all others were collected by hand.
Adults can be found from August to November, mostly in gardens and on outer walls, but sometimes also inside.


Dicranopalpus ramosus, female

Oligolophinae.
This group, characterized by a small ventral tooth on the basal segment of the chelicerae and a trident of spines near the front of the cephalothorax, is the largest of the British sub-families. Its eight species include some of the commonest of our harvestmen, as well as the only ones which require fairly minute examination to determine the identity of the species. Moreover, some of the specific features are developed only when the animal is mature so that, as is usually the case with spiders, immature specimens may be difficult to name.

The genera of the sub-family can be separated by the following table :-

1 (2) Femora of pedipalp with ventral spines or teeth => 3
2 (1) Femora of pedipalp ventrally only hairy => 5
3 (4) Femora and tibiae of legs strongly toothed => Lacinius.
4 (3) Femora of tibiae of legs only hairy => Odiellus.
5 (6) trident of small blunt tubercles => Mitopus.
6 (5) Trident of large sharp spines => (Par)Oligolophus.
This needs updating to include the separation of Oligolophus and Paroligolophus!!

Mitopus morio is a very distinctive animal. The female, which is 8 mms. long, is a creamy yellow colour and the median dorsal band is deep brown or black. The band is produced forwards along the center of the cephalothorax, where it is wider in front. The two portions of the band thus produce an hour-glass like pattern which is not difficult to recognize. It often has a pale median longitudinal stripe. The legs and pedipalp are a dull yellow with brown marks. The femur of the pedipalp bears a short blunt apophysis, covered with setae. The ocular tubercle slopes slightly backwards and the spines of the trident are very small and wide apart.

The male is 5 mms. long and squarer in appearance. Its legs and pedipalpi are much darker than those of the female and the whole creature is more nearly black in colour, save for its transverse rows of white denticulae. In fact the sexes differ more in this harvestman than in any other British species.

Two varieties of Mitopus morio have been described under different names. The earlier of these, alpinus, is an upland variety in which the first tibiae are more strongly armed with spines and the third metatarsi in the male are thickened in the middle. The other, cinerascens, has no spines on its legs and the dorsal band is longitudinally divided by a pale strip.

Mitopus morio is found all over the British Isles as far as the Orkney's. It reaches the summit of our highest mountains, is the only harvestman recorded from Greenland, and also exists in Iceland and Spitzbergen. It crosses the whole of Europe to Siberia and on to China and Persia(Iran), and is also found in North America.
Grid map of records on the NBN Gateway for Mitopus morio

Paroligolophus agrestis
is an extremely abundant species and easy to identify. Its abdominal pattern is based on a greyish silvery background, with brown and often reddish markings. The medial dorsal band is usually well-defined and has yellow, brown or red edges. It is this tendency to a red colour that provides the first means of identification. On the ventral side the genital operculum supplies the second : a small semicircular notch on its anterior margin, as if a bite had been taken out of it.
Paroligolophus agrestis



Paroligolophus agrestis females (various animals)

The legs are not long and their femora are rounded, a fact the helps to distinguish this species from the next. The trident of spines, a feature of this sub-family which is a great help in distinguishing the species, is as described in a comparative note below. The species is widespread all over Britain, and in Europe generally.


Male and female.
Grid map of records on the NBN Gateway for Paroligolophus agrestis

Oligolophus tridens is as abundant as the last species, to which it is closely allied : the two are often found in company, but in wet conditions O. tridens is more frequent. It is very slightly larger than P. agrestis, is duller in colour without the red tinge in its markings, and the genital operculum is smoothly rounded in front. The femora of its legs are angular. This species is as widespread as the above.


Oligolophus tridens male

Oligolphus tridens female.

Grid map of records on the NBN Gateway for Oligolophus tridens

Oligolophus hanseni the third member of the sister-genera, is not so commonly found nor so widely distributed. It is about the same size as the other two, the female being 6 mms. long, and the make 4 mms. long. It has the rounded genital operculum of O. tridens and the rounded femora of P. agrestis, and is lighter in colour than either.
Grid map of records on the NBN Gateway for Oligolophus hanseni

Odiellus spinosus is a most interesting species, recognizable at a glance. Its body is large, 9.5 mms. long in the female, 7 mms. in the male, and broader in proportion than is customary, so that the animal has a flattened appearance, similar to that of crab spiders, as if it were accustomed to hide itself in crevices. The three spines of the trident are broad, bluntly pointed and lie almost horizontally, projecting forwards over the edge of the cephalothorax from a small area of chitin, which is readily separable from the rest of the carapace. The denticulae on the ocular tubercle are very small. The median band on the abdomen is sharply and squarely terminated behind.
This is a southern species, its most northerly record so far being Lancashire. It is a peculiar creature, more often found in gardens and cultivated places than in wilder surroundings. It extends to Spain, Italy and Algeria.

Image Courtesy of Martin Brown.
Grid map of records on the NBN Gateway for Odiellus spinosus

Lophopilio palpinalis is much smaller, the female being only 5 mms. long, and the male 3.5mms. The median dorsal band is broad and has almost parallel sides - it is obsolete in some specimens - and the abdomen on which it lies is quite smooth. The short legs are of a pale-brown colour, ringed with dark bands - an obvious recognition mark. The pedipalpi also help to identify this species, for the patella has a short apophysis covered with setae. The denticulae on the ocular tubercle are long and pointed.
Grid map of records on the NBN Gateway for Lophopilio palpinalis

Paroligolophus meadii, the smallest of the sub-family, is 3.7 mms. long in the female and 2 mms. long in the male. The medial dorsal band is often composed of a number of confluent spots and the abdomen, in contrast to that of L. palpinalis, has a conspicuous rows of strong white teeth on the edge of each segment. The trident has a very long central spine. It is the only harvestman peculiar to Britain.
Grid map of records on the NBN Gateway for Paroligolophus meadii

Lacinius ephippiatus
is between 5 and 6 mms. long. It bears a more distinct pattern than most, for its abdomen is a creamy yellow, bearing a strongly marked median band of dark brown or black with parallel sides. The band is sharply and squarely truncated behind, as in Odiellus spinosus; and in fact the two species bear a distinct general resemblance, as if one were a smaller version of the other. This species may be further identified by the small size of the denticulae on the ocular tubercle, and, in addition, the femora, patellae and tibiae are darkened at there distal ends.
Lacinius has a widespread distribution in England, Scotland, Wales and Ireland. In Europe it reaches Austria and Italy.
Grid map of records on the NBN Gateway for Lacinius ephippiatus

Note on the tridents of of the Oligolophinae:

As stated above, the differences in the form of the trident provide valuable help in characterizing the species of this group. In two species, Mitopus morio, with its trident of small widely separated spines, and Odiellus spinosus, with its broad spines, the distinctive character is obvious under a hand lens. For the other species a microscope is helpful.

The central spine is situated slightly in advance of the two lateral spines in Paroligolophus agrestis and Lacinius ephippiatus. In the former species the central spine is slightly the longest; in Lacinius they are equal in length. In the four remaining species the three spines are set in a straight line. In Paroligolophus meadi the central spine is twice as long as its neighbours; in the rest it is but slightly longer; Oligolophus hanseni has a spine on each side of the trident as well as a sixth just behind it. To distinguish Oligolophus tridens from Lophopilio palpinalis the branched pedipalp and smaller ocular tubercle spines of the latter are helpful. In addition the setae on the pedipalpal tibia of L. palpinalis arise from small protuberances of the exoskeleton.

Phalangiinae.
This sub-family contains the largest and best known species in our fauna. Its distinguishing features include a smooth claw on the pedipalpal tarsus, an absence of a trident, and the absence of a ventral tooth on the first segment of the chelicerae. The four British species all belong to different genera, which may be separated thus :-
1 (4) Tibial segment of pedipalp with apophysis. => 2
2 (3) Ocular tubercle with two rows of very fine spines => Megabunus.
3 (2) Ocular tubercle with normal spines =>Rilaena.
4 (1) Tibial segment of pedipalp unbranched. => 5
5 (6) With median dorsal band; male chelicerae with horn on second segment => Phalangium.
6 (5) With median dorsal spots; dark spots on underside of coxae => Opilio.

Megabunus diadema is a small species, 4 mms. long, with two features that make it unmistakable. Its abdominal pattern lacks the normal central mark and bears instead a pleasing mixture of silver, black and green which, though not easy to describe, is quite distinctive. But more conspicuous is the ocular tubercle in the center of the cephalothorax, for it is armed with two rows of very long sharp spines. It appears that in some specimens the fourth of these spines is clearly shorter than the rest, and this variety was first described as a different species under the name Megabunus insignis.


Megabunus diadema; spined ocularium

This species, like the following, is to be found mature in the spring.
Grid map of records on the NBN Gateway for Megabunus diadema

Its foreign records come from France and Norway.


Megabunus diadema ( (c) Andrew Robertson )

Rilaena triangularis was formerly known as Platybunus triangularis; the genus Rilaena has been separated from Platybubus by Šilhavý as recent as 1965. Even apart from it being the only large harvestman to be found in the spring and early summer, it is easy to recognize. Its abdomen is a dull yellow colour with a dark brown median band, on each side of which there are two or more white spots in each segment. It is quite smooth and even the denticulae on cephalothorax are few and small. The underside is pale yellow. The legs are moderately long and are pale brown with black tarsi. Its most characteristic feature is the form of the pedipalp. Both the patella and tibia are prolonged into bluntly-pointed apophysis and these two projections at once determine the species.


Rilaena triangularis (inset: juvenile)
Rilaena triangularis (Female)
R. triangularis (Female)
A variety originally described as Platybunus corniger is rather larger, smoother and with a less defined band on the abdomen. The denticulae on the ocularium are sharper and more numerous and the pedipalpal apophysis are shorter.
Grid map of records on the NBN Gateway for Rilaena triangularis

Phalangium opilio
is the large common species so conspicuous in the autumn, and is often encountered running across lanes or fields or in gardens. The female may reach 9 mms. in length, the male varies from 4 to 7 mms. The colour of this species is greyish, yellowish or brownish, generally with a well-marked dark brown median band with angular margins. very often this band is broken by a pale median stripe. The underside is white or grey. The legs, which are yellow-brown, have angular femora armed with rows of sharp teeth.


Phalangium opilio (various). Left: females; Right: males.

The male is a very distinct animal with a smaller abdomen and usually with no trace of a median band. Its pedipalpi are much longer than those of the female. Its conspicuous feature is the large dorsal horn on the second segment of the chelicerae. This curious projection varies somewhat in size and shape in different individuals, but is a possession shared by no other British harvestman.

Phalangium opilio; male chelicerae
Grid map of records on the NBN Gateway for Phalangium opilio
 
Opilio parietinus is a large species, the female 7.5 mms., the male 6.0 mms. in length. It has a grey-brown mottled appearance due to a mixture of yellow, white and brown spots. There is no dark median band but a longitudinal row of brown dots sometimes take its place. The legs are long and spotted and the distinguishing feature of the species is an elongated black or brown spot on the underside of the coxa. The ovipositor of the female is unlike that of the other British species : it is conspicuously marked with a number of dark angular rings. Opilio parietinus is currently thought to be (almost) extinct in most parts of western Europe, where it has been replaced by the invasive and fairly similar Opilio canestrinii. (The status of parietinus on the British Isles needs checking?! - It may still be around in Britain as canestrinii arrived there later)

Female Opilio parietinus
Female Opilio parietinus.
Image courtesy of James Clay

I found this O. parietinus in my garden (Aug 08) - and i have heard of three other conformed sighting this year.
Grid map of records on the NBN Gateway for Opilio parietinus


Opilio saxatilis is smaller and carries a row of white on the middle of the abdomen. It has previously been described as a variety of O. parietinus and some have regarded it as a immature form of that species, but adults certainly exist. Its habits are not quite the same as those of parietinus either. It has not, however, been possible to find any constant distinguishing feature between the two. The species is widely distributed in Britain and Europe and is also recorded from North America. (Check characters and see if the distribution remark refers to saxatilis or parietinus!!)


Opilio saxatilis (collage of two individuals)
Grid map of records on the NBN Gateway for Opilio saxatilis

Opilio canestrinii
is an invasive species that originates from the Apennines, but has expanded over large parts of Europe in the past decades and, as it seems, has for the most part replaced Opilio parietinus and probably reduced some other species. Although colour can be quite variable and leg colouring notably less developed in juveniles and sub-adults the adults usually have a orangy-reddish coulouring of the body, normally with a few rows of small white stripes and very dark, almost black legs.

Opilio canestrinii (various individuals).


Opilio canestrinii.


Glossary.
Apophysis - A projecting outgrowth or process.
Chelicerae - The jaws of an "Arachnid".
Chitin - A complex nitrogen compound of which hard parts on many invertebrates are made.
Coxa - The first segment of an arachnids leg or palp, attaching it to the body.
Distal - The end of a limb or segment farthest from the body.
Epigyne - The external genitalia of the female arachnid.
Femur - The third segment of an arachnids leg or palp.
Gnathobase - A projection from the coxa of a limb used to crush food.
Metatarsus - The penultimate segment of an arachnids leg.
Palp, Palpus (pl. palpi) - The leg-like tactile organ in front of the spiders legs, bearing the maxillae and the male organs.
Pedipalp - A more exact term for the palpus.
Setae - A hair-like sensory organ on of an arachnids body and limbs.
Spines - The stoutest setae.
Tarsus - The last segment of an arachnids leg or palp.
Tibia - The middle segment of an arachnids leg or palp.

Checklist of UK Recorded Opiliones

Leiobunidae
Dicranopalpus ramosus
Leiobunum blackwalli  ✓
Leiobunum rotundum
Leiobunum tiscae (Unconfirmed)
Nelima gothica

Nemastomatidae
Centetostoma bacilliferum
Mitostoma chrysomelas  ✓
Nemastoma bimaculatum  ✓
Nemastoma bacillifera (Unconfirmed)

Phalangiidae
Lacinius ephippiatus
Lophopilio palpinalis
Megabunus diadema  ✓
Mitopus morio / Mitopus morio var. ericaeus  ✓
Odiellus spinosus
Oligolophus hanseni
Oligolophus tridens
Opilio canestrinii
Opilio parietinus
Opilio saxatilis  ✓
Paroligolophus agrestis
Paroligolophus meadii
Phalangium opilio  ✓
Rilaena triangularis  ✓
Platybunus pinetorum (Unconfirmed)

Sabaconidae
Sabacon viscayanum ramblaianum  ✓

Sclerosomatidae
Homalenotus quadridentatus

Trogulidae
Anelasmocephalus cambridgei
Trogulus tricarinatus

Total = 28

ą
Dr Feelgood,
24 Sep 2010, 15:14
ą
Dr Feelgood,
24 Sep 2010, 15:09
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