Spiders are the largest group of arachnids on earth. Nearly 4,000 species have been described from North America, with more still to be identified. The term arachnid is derived from the Greek word “arachne”, which means spider. The group includes spiders, scorpions, ticks, mites and harvestmen (daddy longlegs). Although they look like insects, they aren’t. Insects have 6 legs, spiders have 8. Insects have 3 body parts – head, thorax, abdomen – spiders have two, cephalothorax (the head and thorax are fused) and abdomen.
For this note, I relied on several field guides, including “Common Spiders of North America” by Richard A. Bradley. It’s an amazing 271-page reference with 470 color illustrations. A must for anyone interested in spiders. Below is the Amazon link.
There are 68 families of spiders in North America so, where to begin? I’m just going to write about the ones I’ve seen at our place.
First, the orb weavers. This is a large family of spiders with several hundred species in North American. The male spider is much smaller than the female. Most of them spin circular, disk-shaped webs (orbs). My all-time favorite spider is the black and yellow garden spider (Argiope). I’ve seen two so far this fall. Both in our backyard. The large female is unmistakable. She is black or brown, and yellow. The head (cephalothorax) is whitish. Her legs are held paired and are orange at the base, becoming black toward the tips. In the fall, I often run into their webs stretched across our trails. The web usually has a verticle zigzag struckture referred to as a stabilmentum. Its purpose is to strengthen (stabilize) the web and provide camouflage for the spider. Many orb weavers build new webs daily.
There are two other orb wavers that I see, the marbled orb weaver and the spined micrathena. The marbled orb weaver is another common spider in our area. It is smaller than the garden spider, is orange or brown and has a large, round abdomen. The spined micrathena is a small, spiky, black and white spider that looks like a burr, especially if it’s on your jeans. It’s not as common as the marbled orb weaver.
The brown recluse belongs to the violin family of spiders, all of which are venomous. This is a small family with only one genus in North America. The brownish spiders are medium sized and have an inverted violin-shaped marking on the cephalothorax. It’s also called a fiddleback spider. They have 6 eyes instead of 8 like other spiders. While the bite is painless, mild to severe pain occurs within a few hours, accompanied by redness, itching and a blister develops at the site of the bite. This is frequently followed by nausea, chills and headache. The blister becomes an ulcer that may take weeks or months to heal. When the ulcer begins to heal, the dead tissue is removed, and skin grafting may be needed.
The black widow belongs to the cobweb spider family, one of the most diverse groups of spiders worldwide. Most cobweb spiders build their webs under a covering of some sort. When the kids were young, and we camped in the Pecos Wilderness north of Santa Fe, NM, we would always check under the seat in the outhouse for black widows. That’s where they liked to hang out. The black widow is not an aggressive spider. She is calm, slow-moving and will bite only if threatened. The black widow’s venom is a neurotoxin. It causes violent and prolonged muscle cramping. It is 15 times more toxic than rattlesnake venom. Fortunately, only a tiny amount is injected. She is recognized by a red or orange hourglass marking on her belly. Black widows tend to like damp areas, brown recluses prefer dry conditions.
Crab spiders are often found on flowers where they lie in wait to ambush flies, bees and other pollinators that visit the flowers. They have compact bodies and relatively short, thick legs that are held sideways, like those of a crab. Some of the ones that live on flowers can change their color to match that of the flower.
Wolf spiders live on the ground, have excellent vision and often hunt at night. Their scientific name is Lycosa, which is Greek for wolf. Rather than running down their prey the way a wolf would, they lie in wait for prey. Many live in burrows in the ground. The female will carry her egg sac and when the eggs hatch, the baby spiders will ride on her back.
The last spider I’ll mention is the jumping spider. It is a small, keen-eyed hunting spider that is often found indoors. We frequently find them in the house and just leave them alone or, if the weather is mild, take them outside and release them on the plants. Jumping spiders are as cute as spiders get. They do not build webs, but stalk their prey, the way wolf spiders do.
