EPOW - Ecology Picture of the Week

The Thorn That is a Spider

Spined Micrathena, (Micrathena gracilis), Family Araneidae
West Virginia, USA

Explanation:  From afar, this dead tree branch seems to have an anomalous but innocuous thorn on it.  But look closely ... this thorn has legs.  Eight of them, in fact.  

It is actually a spider ... with an abdomen shaped like a thorn.  But why?  Does this odd adaptation help it hide from its predators?  Or to hide in ambush of its own prey?  Or does it serve both functions? 

Despite their appearance, spined micrathena spiders are harmless to humans.  They spin their usually three-lined webs across gaps in brushy woodlands, commonly across walking trails (oh, the feeling of walking into a web face-first...) to catch flying insects.  And it is the larger female, shown in this week's photo, that spins the web; the male is far smaller, and is essentially spineless (make up your own jokes here).