A close up of a silver orb spider on tree branch
Another silver orb weaver. Recent studies have shown that the silk in the zigzag bands reflects ultraviolet light, which is attractive to flying insects. SARA MATTHIS/Keys Weekly

Entomologist Larry Hribar from the Florida Keys Mosquito Control District talks spiders:

Florida is home to a lot of spiders. Among the most conspicuous are the orb weavers.  Pictured is the silver orb weaver, Argiope argentata. You might also encounter related species such as the tropical orb weaver, Eriophora ravilla; the Florida argiope, Argiope florida; and the golden orb weaver, aka the “banana spider,, Nephila clavipes. The different species can be distinguished most easily by the color patterns on their abdomens and legs. What the general public calls “crab spiders” are actually spiny-bellied orb weavers. (True crab spiders are an entirely different group of spiders.)

Orb weavers can inspire fear and even panic in some people due to their large size. The fact is that these spiders are not aggressive and will not bite unless handled roughly or carelessly. For a healthy, non-allergic adult, the bite is said to be about as painful and of as much concern as a bee sting. Orb weavers build large round webs in open areas, often between trees or tall plants.  Sometimes the webs are supported by very long support strands and the web itself seems to hang in midair far from any anchor point. Many times the webs are not noticed until someone walks through one and gets a face full of silk. Adult female spiders tend to hang head down in the center of the web and wait for prey to become tangled in the web. Most of their prey consists of flying insects but small lizards sometimes end up being captured. Some orb weavers build their webs close to each other in aggregations while others are more solitary.

In the photo you will notice four zigzag bands of silk around the center of the web. The structure is called a stabilimentum. Long ago it was believed that the stabilimentum served to strengthen and reinforce the web.  Now biologists argue whether it serves to scare away birds or to attract prey. Recent studies have shown that the silk in the stabilimentum reflects ultraviolet light, which is attractive to flying insects. The shape and size of the stabilimentum varies between species and with the age of the spider.

Orb weaver spiders are natural pest control agents. They have very attractive color patterns.  They are harmless to people. Leave them alone and they’ll leave you alone.

My name is Larry and I’m an entomologist with the Florida Keys Mosquito Control District.  I’m originally from the Pittsburgh area and I graduated from Penn State, Tennessee, and Auburn.  My family and I reside in Marathon (there’s nowhere better in Monroe County!) and when I’m not at work I’m home recuperating from a broken leg.

Are you wondering about something? Email [email protected].

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