Asiomorpha

While current literature lists this genus as being synonymized under Orthomorpha, it has been suggested (2) that molecular data shows there is strong evidence for this genus being valid distinct from Orthomorpha; coarctata, the only species in the genus that is kept in captivity (information on Millibase conflicts with what is suggested in the above article) is also only known under the name A. coarctata amongst enthusiasts, so for the purposes of this article it will be listed under the genus Asiomorpha. A. coarctata is a common pantropical pest species, and is commonly confused with another, similar species, O. gracilis.

A. coarctata is very easy to care for; one contributor reports specimens reproducing in a 64 ounce enclosure with Better Nature brand potting soil for substrate and no ventilation. Being such a wide-spread pest it can handle a variety of temperature, moisture, and habitat changes, and aside from ensuring the specimens do not dessicate or crash their numbers through rapidly consuming food nothing special is needed to keep this species alive and thriving in captivity.

A. coarctata reaches to about 0.8"/2cm, and has a variable black-to-brown body color with yellow-to-tan paranota and tan-brown legs.

Asiomorpha coarctata courting behavior, male on top of the female. Photo compliments of Connor Smotzer (3)

Asiomorpha coarctata wild observation, by Connor Smotzer (4)

These Asiomorpha coarctata were found in Boerne, Texas in a local park, last weekend of August when the temperature was 95F/35C. The area has received more rain than perhaps typical. A small colony was located under, and in, rotting wood of an unknown species on the soil level that retained moisture underneath its surface, mostly shaded by the tree cover. This location had the majority of individuals, about 30 A. coarctata. The area had a loose proximity to a very small stream, but in an area that is overall drier than the rest of the park and other identified A. coarctata locales. There was usually less than expected arthropod life (such as Isopoda, Chilopoda, and Collembola) under rotting wood occupied by A. coarctata.

Other individuals were found in smaller quantities under fallen Quercus virginiana (live oak) bark where it had sloughed off and fallen on the soil surface, and under cut logs of Taxodium disticum (bald cypress). Throughout the park all individuals were the same size and all appeared to be adults, no smaller/younger individuals were observed.

The ID of Asiomopha coarctata was not confirmed until finding and comparing images of the two very similar species, Oxidus gracilis and A. coarctata, which I will discuss later.

Comparison between Asiomorpha coarctata and Oxidus gracilis, by Connor Smotzer (5)

For me at first glance the differences between these two species as far as identification with the naked eye is concerned are quite cryptic, and I can see why they are easily confused. But upon reviewing macro photography of the two there is a clear difference in the morphology of the paranota, or the extending lateral metatergite margins, in particular the size and shape, between the two species. With the specimens I photographed differences were visible in nearly all segments after the first two but other observations say it is clearest after segments 8-9. On Asiomorpha coarctata the metatergite paranota are wider, winged, and pointed posteriorly, some extending past the segments themselves. On Oxidus gracilis the paranota are smaller, rectangular in general shape, and rounded both anteriorly and posteriorly. Note the differences in the below photo.

  1. Likhitrakarn et al. (2019). Review of the millipede genus Orthomorpha Bollman, 1893 (Diplopoda, Polydesmida, Paradoxosomatidae) in Vietman, with several new records and descriptions of two new species. Zookeys, 898(1), 121-158. http://dx.doi.org/10.3897/zookeys.898.39265

  2. Smotzer, C. (2021). Asiomorpha coarctata courting behavior. Photograph. Permission granted.

  3. Smotzer, C. (2021). Asiomorpha coarctata wild observation. Via Email.

  4. Smotzer, C. (2021). Identification Comparison: Asiomorpha coarctata and Oxidus gracilus, With Photograph. The Millipede Enthusiasts Database.

  5. Sierwald, P.; Spelda, J. (2021). MilliBase. Asiomorpha Verhoeff, 1939. Accessed at: http://millibase.org/aphia.php?p=taxdetails&id=891041 on 2021-11-11