Spined Micrathena – Spiny Orbweaver Spider

spiny micrathena sidways

Spiny Orbweavers are spiny and hard indeed.

If you’ve taken a walk in the woods lately, you’ve likely run into a spider web. Chances are pretty good it was the orb web of the Spined Micrathena (Micrathena gracilis) or Spiny Orbweaver Spider. It is one of the most common woodland spiders, and it commonly builds webs across trails. Why does it always build its web across a trail where something will run into rather than parallel to the trail? Because those same trails used by people and larger animals are also the most likely to be used by the flies and other small insects that make up the vast amount of prey for these bizarrely shaped spiders. Though they are a nuisance, they are harmless to people.

spiny micrathena upside down

When looking at the bottom portion, the body is cone-shaped

Female Spined Micrathena Spiders have 10 spines or points above their bodies and are cone shaped below. They can come in a variety of colors, but often are darker below and lighter colored (often white, yellow, or orange) above. This is a form of counter-shading, helping to camouflage them in the dappled light of the forest. They hang head down in the center of their webs, and from above match the darker forest floor, but from below match the lighter colored sky. They can get to about half an inch long and only the females build webs.

The males are rarely seen. They only have two spines and are very slender, being only half the size as adults than the females. They often station themselves near a female’s web seeking an opportunity to mate with her. They have to be careful or the larger female will eat them.

These small and common orb web spiders only live about a year (the males not even that long). By late summer and early Fall, the females will lay their eggs in a fuzzy egg sac hidden off to the sides of their webs. The adults all soon die, but the eggs will overwinter and young spiderlings will hatch out to spread through the forest the next spring.

>> Read more at the Capital Naturalist blog.

Comments

  1. I run early in the morning in parks and on trails and am constantly wrecking these spiders’ webs, so I apologize to the critters! I’m glad to know they’re harmless so I won’t get bitten one of these days. Thanks for sharing this great info!