|V. arenata - legs tucked up|
It typically builds its web at head height, making it one of the most commonly seen species. Unlike all the other orb weaver spiders which cling to the web head down, V. arenata is usually found head up.* Another distinctive trait is its tendency to sit with its legs tucked under the body instead of extended.
|Spiny Orb Weaver - Photo by Richard Hover|
|M. gracilis - Wikimedia|
In both species only the females build webs; circular structures suspended vertically from strong silk lines stretched across trails and openings between woody vegetation. These are pathways frequented by small flying insects and incidentally, humans. They specialize in tiny flying insects like mosquitoes, gnats and flies. After the prey hits their sticky, closely woven silk, the spider bites it, injecting its venom which digests it internally. The spider then returns later to suck up its predigested juices.
The female needs all the energy she can get as she will continue to produce egg cases as long as the weather holds. The adults die over the winter and the new generation emerges from the egg cases the following spring to continue the cycle.
• More research on V. arenata's head up position and its effect on speed and web construction is at this Pubmed article.
Details on the arrowhead spider are at this MDC xplore page.