Spiny-Bellied Orb Weaver

Micrathena gracilis
Araneidae (orb weavers) in the order Araneae (spiders)

Colors vary from whitish to yellowish, mottled with black or brown. The ten-spined, chunky abdomen sets the female spiny-bellied orb weaver apart from all other spiders. The carapace is amber, and the legs are glossy black.

Males of this species are seldom seen. They are much smaller and do not spin webs. Their abdomens lack spines and are instead simply elongated and dark. Most people who see them find them courting in the webs of females.

Orb weavers, including this one, spin wheel-shaped webs that are usually positioned vertically. This species tends to hang with its "back" or "top" toward the ground and the spinnerets pointing upward, with the abdomen looking like a tiny pyramid. Also like other orb weavers, Micrathena gracilis typically has one very long silk thread leading to a leaf or branch above the web. This is the spider's escape line, and it comes in handy when a bird or a hiker blunders into the web.

Length (not including legs): females to about 3/8 inch; males only about 1/8 inch.
Habitat and conservation: 
Commonly seen during woodland walks in August and September, as the females take advantage of the open areas of hiking trails, which flying insects use as trails, too. Also often seen in yards and other places where trees and bushes create appropriate open areas for them to spin their circular webs. They almost never enter houses.
The web is a delicate, closely woven orb (wheel-shaped web) with a pattern specialized for catching minute flying insects such as gnats and mosquitoes.
Distribution in Missouri: 
Statewide in woodland areas, although it is more common in central and southern Missouri, where timber is more extensive.
Life cycle: 
As a general rule, spiders in our area hatch from eggs in spring and spend the growing season eating, maturing, mating and laying eggs. Females are capable of creating webs; males are not. Females continue creating egg cases as long as the weather holds out. As temperatures cool in fall, their metabolism slows, and they generally die when it freezes. Egg cases overwinter, and spiderlings hatch in spring.
Human connections: 
It would be easy to dismiss the importance of these tiny predators, but once you have been plagued by the tiny insects they prey on, such as gnats and mosquitoes, you become thankful for their role in limiting such pests.
Ecosystem connections: 
Spiders are little predators that help to control populations of the insects they capture. Being small themselves, they easily fall prey to larger predators such as birds, reptiles, and mammals. Many animals eat their eggs. Hummingbirds steal webs from spiders in order to build their own nests.
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