Orchard Spider


Leucauge venusta
By Brandt Hart

Description   

Imagine the inherent honor in being named by the first creature in Earth's history to recognize that the incredible diversity of life surrounding us can be explained by a phenomena known as Evolution by Natural Selection. The Orchard Spider, also known as the "Orchard Orb-weaver," and the "Venusta Orchard Spider," is the only spider species that received its nomenclature directly from Charles Darwin himself. Now, imagine the inherent horror in being the host of a strange parasite that, slowly and steadily, sucks the life fluids out of you until all that remains is your skeleton. Even Darwin couldn't foresee that nightmare awaiting the Orchard Spider in the forest. 

Leucauge venusta is a vibrantly colored long-jawed orb-weaver spider. The Orchard Spider is abundant in the spring and early summer when mating is occurring, ranging from southern Canada, throughout the United States, and into Colombia. Easily identifiable by its green legs and brightly spotted abdomen, as seen in the photos captured in North Carolina's Carolina Beach State Park, this spider is often observed hanging upside-down from the center of its horizontally-woven web.  Only the female creates webs, but both genders display the characteristic neon orange and yellow coloration on their thorax and abdomen. The female body is typically 5.5-7.5 mm in length, while the smaller male averages between 3.5-4 mm. 


The Orchard Spider's abdomen is an elliptical oval at least twice as long as it is wide- a feature that stands in contrast from the more orbital abdomens of other species of orb-weavers. The vividly green legs of Leucauge venusta (always green in females, and various colors in males) are covered in spines and hairs. In fact, the femurs of the 4th pair of legs are wrapped in trichobrothia, special sensory hairs that resemble fake eye lashes. Although there are some species of spiders that have a reduced number of eyes, the majority possess eight. This is the case for Leucauge venusta, bearing eight eyes arranged in a trapezoid arrangement

The Orchard spider is adaptable to a variety of habitats, but seems to prefer moisture-rich forested environments- such as can be found in Carolina Beach State Park. Leucauge venusta weaves its orbital web before dawn in the low branches and bushes of the forest, and may reinforce or rebuild the web multiple times throughout a day. Anything caught in these horizontal webs becomes food for this spider- often a variety of flying or jumping insects. 

Left and Above-Right Images: Brandt Hart

Taxonomy

Kingdom: Animalia
Phylum: Arthropoda
Class: Arachnida
Order: Araenae
Family: Tetragnathidae

Leucauge venusta belongs to the Kingdom Animalia and the Phylum Arthropoda- invertebrates that possess an exoskeleton, a segmented body, and appendages with joints. The Class Arachnida, of which the Orchard Spider is a member, are classified as joint-legged invertebrates with eight legs. Arachnida is derived from the Greek word "arachne," meaning "spider." The detail added in the Order Araenae are the possession of fangs that inject venom, found in all true spiders. The Family Tetragnathidae is home to all true spiders with elongated legs and chelicerae (the "jaws" of the spider). It is within this Family that Leucauge venusta is organized.    

The Orchard Spider was given the Genus species nomenclature directly from Charles Darwin, who selected Leucauge, from the Greek for "with a bright gleam," and venusta, Latin for "charming, elegant or beautiful." 

Above Image: Brandt Hart

Niche and Habitat 

Leucauge venusta boasts an extensive range, spanning from Canada, throughout the United States and Mexico, and even thrives in South American locations. The Orchard Spider is most easily spotted in spring and early summer when mating occurs and eggs are laid. 

This fragile-looking, but resilient spider can adapt to a plethora of diverse habitats, but optimally lives in forested areas that retain moisture. An example of ideal locale for this spider is the habitat provided by Carolina Beach State Park in North Carolina. Leucauge venusta weaves its web in the low branches of trees or low-lying shrubbery- areas frequented by flying and jumping insects, which the spider feeds on. Even with its display of neon colors, the Orchard Spider is easily missed, as it will rapidly descend from its web when disturbed or threatened. 


Life Cycle / Evolutionary Traits

As do the majority of spiders, Leucauge venusta reproduces sexually- fertilization is internal, but takes place indirectly. The male begins the mating process by transferring the sperm to needle-like structures attached to the ends of their pedipalps. When a female is spotted, the male ensures that it is of the same species through chemical recognition "smelling." In order for the much smaller male not to be immediately eaten by the female, the male must partake in specifically coordinated courtship rituals, that often include inducing exact vibrations on the female's web that will allow him safe passage. If successful, the male eventually injects the sperm from his pedipalps into the female. 

Once fertilized, the female Orchard Spider will create an egg sac of loose, orange and white silk in late spring or early summer. These egg sacs can be made inside a rolled up leaf or attached to twigs near the web. Egg sacs of Leucauge venusta can reach up to 9 mm or more in diameter, and contain several hundred eggs. The female Orchard Spider can continue laying eggs as long as its metabolism is maintained through feeding and the temperatures of its habitat permit. The Orchard Spider usually lives shy of one year, as the cooling temperatures slow its metabolism and the frosts eventually kill the organism. The spiderlings within the egg sac overwinter and then disperse the following spring.  

Above Image: Brandt Har

The Orchard Spider possesses numerous incredible evolutionary traits, including a central nervous system, lungs, and sensory organs. But, of course, the distinctive adaptation of spiders is the ability to create architecturally brilliant webs. Web-building spiders tend to be visually weak, but ultra-sensitive to vibrations. And the types and purposes for a spider's web are as numerous and diverse as the Arachnida Class itself.                 

Leucauge Venusta is categorized as an orb-weaver, meaning it creates spiral, wheel-shaped webs. Webs must achieve three critical functions: catching prey, absorbing the prey's momentum without destroying the web, and retaining the prey permanently. With these factors in mind, certain web designs are targeted to certain types of prey- thus the fact that approximately 50% of the potential prey that contacts an orb web escapes, is not surprising. The Orchard Spider weaves horizontal orb webs, which serves several purposes. Although horizontal webs are more susceptible to damage from heavy rains and falling canopy debris, they maintain integrity in strong winds, and most importantly, are much less visible to prey ascending from the forest floor, such as insects. Orchard Spiders repel through an opening in the center of their orb web, keeping their backs to the ground, allowing them to monitor the web above them for any prey that becomes captured. 

If these orb webs weren't impressive enough in a terrestrial environment, they are just as effective in space. Skylab 3, the second manned mission to the first American Space Station in 1973, brought along 2 orb-weaver spiders to observe their web building capacity in zero-gravity. Initially, the webs were somewhat lackluster, but the spiders quickly adapted to the new environment and produced exceptional webs. 


Friends and Foes

It may come as no surprise to hear that spiders, in general, have more foes than friends. But you may not realize why you and spiders should be buddies. First, the bad guys.

variety of species consider Leucauge venusta prey worthy of pursuit. A multitude of birds eat the Orchard Spider, easily decipherable in the undergrowth by its bright coloration. Hummingbirds are notorious for stealing spider webs as nest construction material. Many species of reptiles, such as the Carolina Anole, a lizard that frequents Carolina Beach State Park, eat the Orchard Spider. Also on the list of predator suitors are mammals like bats, shrews, and small rodents.

By far the most peculiar incidence of threat to Orchard Spiders is one that Leucauge venusta seems not to mind- until the spider is dead.  On occasion, a wasp will paralyze an Orchard Spider, and once the spider is immobilized, lay its eggs on the spider. Eventually, a larva will become visible on the abdomen of the spider. In a terrifying display of parasitism, the wasp larva continually extracts nourishment from the spider by sucking fluids directly out of the spider's abdomen. This may continue for days, all the while Leucauge venusta continues normal routines and patterns. Once the larva has reached a certain size, it injects the spider with a hormone that essentially causes derangement. The spider can no longer weave organized webs, or properly move- it will be dead in an hour. In the meantime, the wasp larva sucks the remaining fluids from the Orchard Spider, until the hollow husk falls to the ground. The larva then uses the deceased spider's web to attach its cocoon. Metamorphosis transpires, and away flies a healthy wasp.




In quite the one-sided relationship, a semblance of friendship actually exists between spiders and humans- though this usually isn't enough for most to cease repaying them with the bottom of a shoe. There are few species on Planet Earth more despised than spiders by the general population, and one of these species is the mosquito. Aside from obnoxious bites on the back of the neck, mosquitoes spread viruses, including Malaria. Some experts have suggested that, spanning from the stone-age to present day, Malaria has been the cause of 50% of human deaths throughout history. Of all the methods utilized currently to exterminate mosquitoes, it is often overlooked that spiders are a "natural exterminator" of this pest. Mosquitoes are one of the Orchard Spider's favorite foods, which equates to less of them biting humans and spreading viruses. Maybe we should work on being better friends.

Environmental Impacts

As stated in the previous section, spiders, in general, are an excellent population buffer on exploding populations of insects and other pests. Spiders, like the Orchard Spider, prey on mosquitoes and countless other pests, many of which are devastating to commercial crops. The spider's knack for natural pest control has revealed implications on a much larger scale.

An estimated 25% of commercial crops are lost to pests annually. Accompanying that statistic are the extensive financial and human resources that are applied in elimination attempts of these pests. And, of course the health concerns that arise from frequent use of herbicides on crops soon to be consumed by the general public. But, as the UCONN Health Center proved, spiders are a much more efficient pest control solution than chemicals- especially when a particular pest is being targeted by a specialist spider.






This strategy can be applied on a much smaller, home-garden-sized scale. Avid gardeners who allow spiders to frequent their vegetables may find this natural version of pest control to be cheaper, greener, and more effective than any herbicides that can be purchased in stores.

Even the aspect of spiders we tend to fear most- their venom, which is only a threat to humans on the rarest of occasions- is being beneficially applied in a variety of incarnations. Research undertaken by Newcastle University in the United Kingdom has produced a completely bee-friendly pesticide made entirely from plant protein and spider venom. This is an enormous breakthrough, as bees are currently experiencing devastating population loss. And, as one of the most important pollinators on the planet, bee decline is a troubling phenomenon for commercial crop growers. This new, bee-friendly pesticide, could provide some relief to the buzzing pollinator. Spider venom is also being experimented with in medicinal fields, providing some interesting and promising results in heart care.

Conservation

An unfortunate common denominator of all conservation, including conservation of Leucauge 
venusta and other spiders, is habitat conservation. Loss of habitat equates to loss of spiders. Of course, this can be considered on large scales, which can encourage us to create reserves, protected areas, and state parks- like Carolina Beach State Park where the Orchard Spider is currently thriving. And even though the Orchard Spider is not endangered or threatened, there is no harm in being proactive and ensuring that this never changes.

Individuals can do their part by being mindful of not destroying what could be perfect spider habitat. Perhaps leaving some uncut sections of grass, or overgrown shrubbery on the periphery of your yard- both strategies that benefit spiders. Even more effective, especially for gardeners, is diversification in personal "habitat." Having a variety of plants, trees, and consumable crops will only serve to increase potential spider propagation and organism diversity, which will unleash the aforementioned benefits our eight-legged friends have on us and the environment that connects all living things.

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Videos


The Orchard Spider- Life in the Undergrowth

The Orchard Spider- Day in the Life



Resources:



Web Site Links:
http://www.explorit.org/science/spider.html - How do spiders breathe? Do they have blood? Check out this FAQ archive of spider information. 
http://www.insectidentification.org/spiders.asp - Unidentified spider hanging out in the corner of your bathroom? Use this resource to reveal its identity. 
http://www.spiders.us/ - An international spider community with a North American focus. Articles, forums, images, and endless information. 
http://www.planetnatural.com/garden-spiders/ - Improve your garden...with spiders! The "why" and the "how" of utilizing eight-legged pest control. 
http://www.livescience.com/topics/spiders/ - All the up-to-date articles being written about spiders in one place
http://www.ncparks.gov/Visit/parks/cabe/main.php - Explore a sure-fire location to find Orchard Spiders: Carolina Beach State Park in NC.
http://www.ars.usda.gov/is/kids/insects/story7/spider.htm - If the U.S. Department of Agriculture isn't afraid of spiders, you shouldn't be either. 



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Brandt Hart,
May 31, 2015, 2:09 PM
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