Spiders of North America
Live spiders, spider eggs, ticks, mites, and other arachnids photographed at various United States. Spider Index | Funnel Web | Orb Web | Cobweb
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Furrow Spider - Larinioides cornutus mature female = 12mm
Orb Weavers - Family Araneidae is a huge group of spiders with 3500 species worldwide, 180 of which call North America home. These spiders vary greatly in color, shape and size, measuring between 2 - 30mm (1/16 -- 1 1/4") long.  Males are generally much smaller than females.

Most orb weavers spin spiraling webs on support lines that radiate outward from the center; the plane of the web may be vertical or horizontal or somewhere in between. Many orb webs are built on human structures, parallel to walls.

Orb webs are the result of millions of years of evolution; spider silk is many times lighter and stronger than steel, and the geometrical architecture could not be more economical or efficient.

Family Salticidae - Jumping Spiders are active hunters that capture prey by stalking and pouncing, exactly like larger  predators. Salticids range from 3-15 mm (1/8 -- 5/8") long. They have the most acute eyesight of all spiders, and can jump more than fifty times their own body length.

For what it's worth, jumping spiders are the only arachnids I can tolerate crawling on me. They are so "cute!"

Anatomical points of interest

  • Esophagus passes through the brain
  • Portion of the gut sits on top of the eyes and brain
  • Heart extends from abdomen into cephalothorax
  • Salticids move their retinas to look in different directions
Jumping Spider Index
External Spider Anatomy
External Spider Anatomy
A. Dorsal (top) view       B. Front view of face and chelicerae      C. Ventral (bottom) view [1]
Spiders, like most other arachnidss, have their body divided into two portions, the cephalothorax and the abdomen. The cephalothorax consists of the head and thorax fused together. Most spiders have four pairs of legs attached here, activated by muscles inside the chitinous exoskeleton. The top of the cephalothorax is covered by a convex hardened shield (carapace), with the eyes mounted at the front.

The eyes are simple, and resemble the ocelli of insects. Most spiders have 8 eyes; Some lineages have lost some or all their eyes, ergo there are spiders with 8,6,4,2, or one or none. The size and positions of the eyes is widely variable. Many of the hunting spiders, e.g. Salticidae (jumping spiders) and Lycosidae (wolf spiders) have large, forward-facing eyes and keen vision required for their craft; many of these spiders have at the back of the eye a reflective membrane called a tapetum [1]. It is this surface that aids in night vision and causes their eyes to reflect light and shine in the dark, like a cat's eyes. Most sedentary spiders have relied on their sense of touch for so long their vision is thought to be poor.

Spider eye arrangements are a simple diagnostic tool that can often get you to the family level. There is a great reference at Bugguide.net showing templates for many different families [2].

Spider catches wasp
Look out!
Below the carapace, on the bottom of the cephalothorax, is a heart-shaped plate, the sternum. In front of that is a smaller lip, or labium, which forms the bottom of the mouth. The coxae of the legs and pedipalpi are arranged radially around the sternum. In most spiders, the coxa of the pedipalp is fitted with an enlarged, sharp plate, the maxilla or endite, which helps the spider dismantle its prey.

Directly underneath the carapace at the front are two chelicerae, or jaws, which are the deadly weapons wielded by these predators. Each chelicerae is  tipped with a fang - the venom delivery vehicle that works roughly like a hypodermic syringe. The fangs are stored in a groove in the base of the chelicerae when not in use.

All spiders are predacious and carnivorous. They subsist on the bodily fluids and chewed up live insects they have paralyzed with their venom. Their method of feeding is pretty much the same as ours, except their "teeth" and digestive processes are external.  The strong chelicerae and the sharp edges of the endites are used to crush and pulverize the prey, all the while bathing the resultant wreckage in copious quantities of digestive fluid from the maxillary glands. The resultant broth is vacuumed up through the mouth and esophagus by means of powerful muscles that cause expansion of the stomach and gut. It is thought spiders do not ingest solid food, but only predigested liquids. Some hard-bodied insects like beetles are injected with digestive juice through a small hole, and the whole outer cuticle is discarded afterwards [1].

Lynx Spiders - Family Oxyopidae are diurnal, that is, they hunt during daylight hours. Their hunts are conducted much like those of their namesake; they roam the foliage looking for prey.

Their eyesight is not as keen as the jumping spiders, and they more often use the "wait and pounce" hunting tactic most often associated with the (equally well) camouflaged crab spiders, Thomisidae.

Studies have shown the green lynx spider to prey on many species of insect, with insects in the Order Hymenoptera being the most common, comprising over 40% of all captures. Diptera (true flies) accounted for fully 15% of all prey. It must be kept in mind, as well, that spiders serve as food for many other types of organisms, principally birds.

Lynx Spiders
Wolf Spider Eyes Detail
Wolf Spiders - Family Lycosidae are active hunters. They don't build capture webs per se, but some do construct hunting webs that serve as scaffolding on which the spider can move about very rapidly.

The female spins a large spherical egg sac, attaches it to her spinnerets and drags it around until the eggs hatch. The hatchlings then climb onto her back and stay there until they are able to fend for themselves.

Wolf spiders are harmless to humans and their pets. Contrary to anecdotal reports, wolf spiders do not have necrotizing venom and do not transmit pathogenic bacteria. Most spider bites attributed to this family are misdiagnosed and based on circumstantial evidence [3].

Nursery Web and Fishing Spiders (Family Pisauridae) superficially resemble wolf spiders. Most spiders in this family have their eyes arranged in two rows, with the front row in a straight line of four, the second row curved in a u-shape. These spiders do not build webs to catch prey, but use silk  to construct a special nest or nursery web.

The female carries a spherical egg sac around until the eggs are ready to hatch, then constructs a web and places the egg sac inside. She then stands guard nearby until the spiderlings have all grown and dispersed. Some of the largest spiders in this family, the fishing spiders, run over the surface of ponds and streams, and sometimes even go under water. They may capture tadpoles and small fishes near the surface, but mostly prey on insects.

Nursery Web Spider
Funnel web weavers (Family Agelenidae) are often found in grassy fields, low shrubbery, or living among leaf litter in forests. They spin sheet webs of nonsticky silk with a characteristic funnel extending off to one side.

The so-called Hobo spider (Tegenaria agrestis) is a member of this family. The hobo has been expanding its range since its introduction (from Europe) into Washington state in the 1930s. It has been implicated as a spider of 'medical importance' as  studies indicated the hobo spider bite caused necrotic lesions  either through the actions of hemolytic venom, or the introduction of pathogenic bacteria into the wound. However, a 2009 study conducted on T. agrestis spiders collected around homes in Washington state  revealed no hemolytic aspects of the venom, and no bacteria other than those routinely found in soil, in the air, or even on human skin [3].

Family Tetragnathidae - Long-Jawed Orb Weavers are usually easy to identify by their eponymous huge, powerful chelicerae (jaws) and long, slender abdomen. Like the other family of orb weavers, the Araneidae, these spiders have eight eyes and 3 claws on each tarsus. There are about 25 species in North America.

The Venusta Orchard spider, a very common woodland arachnid, is a member of this family. The Venusta (after Venus, the goddess of beauty) spider is nearly ubiquitous in the forest understory here in northern Illinois where they sit upside down in their smallish (6-8 inches or so) horizontal orb webs. Their chelicerae are not nearly so prominent as other spiders in this family.

Crab spider
Crab spiders (Family Thomisidae) hold their legs outstretched to the sides, in the manner of their crustacean namesake. They have short, broad bodies and 8 small eyes sometimes located on raised bumps. The second pair of legs is often much heavier and longer than the third and fourth pairs. Crab spiders do not build any sort of web, they prowl the ground and climb flowers and plants in search of prey. Many are masters of camouflage and simply await their prey on flowers, much like ambush bugs.  Their prey includes butterflies, flies, beetles, bugs - just about any insect that blunders within range.

Like all spiders, crab spiders go through a simple metamorphosis.  Young crab spiders hatch from eggs and look like tiny adults.  They shed their skin as they grow. Most live for less than 1 year. Females produce hundreds of eggs in the fall, and the offspring hatch in the spring.

Cobweb spiders (Family Theridiidae) are also called comb-footed spiders, after the inconspicuous comb-like bristles on the hind tarsi of many species. These spiders spin irregular webs (cobwebs) and use their combs to fling silk over any  prey that gets caught in the web. Thus swathed, the victim is then hauled to a rest site, injected with venom, and later eaten. There are more than 200 North American species in this family which includes the black widow spider.
Female Cobweb Spider
Female Cobweb Spider - Enoplognatha ovata
Brown Recluse Spider
Brown Recluse Spider - Loxosceles reclusa [4]
The brown recluse spider is one of the very few spiders that present real danger for humans and their pets. When this spider bites, it injects a hemolytic venom which can cause tissue necrosis.

Brown recluse spider bite symptoms are generally mild swelling and tenderness at the site, ranging up to severe dermonecrotic lesions. Widow spiders bite more people than the brown recluse.

Red Velvet Mite - Class: Arachnida / Subclass: Acari / Superorder: Acariformes / Order: Actinedida /
Velvet mites are critically important to soil replenishment and sanitation, preying on tiny insects that feed on bacteria and fungi that live in the soil and whose remains constitute a large volume of same.

Family Gnaphosidae (Ground Spiders) -Eastern Parson Spider - Herpyllus ecclesiasticus
Completely harmless, but big and black and hairy, this common indoor spider can startle the best of us.

Cellar / Vibrating Spiders - Family Pholcidae
Often live in dark, undisturbed places like basements and attics. They are small-bodied spiders with very long, thin legs. Many are capable of "vibrating" their way to invisibility; you can see a video of this process here.

Mesh-Web Weavers - Family Dictynidae
Tiny spiders in this family are all under 5mm long, most are in the 2-3mm range. There are approximately 290 species in 20 genera.

Running Crab Spiders - Family Philodromidae
These are very common spiders that frequently live in human dwellings - they are likely culprits when you find cobwebs in the corners of your ceilings. Pictures of spiders that are probably living in your house right now.

  1. William J. Gertsch, PhD. "American Spiders"
  2. Lynette Schimming, Bugguide.net, "Spider Eye Arrangements"
  3. Misdiagnosis of Spider Bites: Bacterial Associates, Mechanical Pathogen Transfer, and Hemolytic Potential of Venom from the Hobo Spider, Tegenaria agrestis, Melissa M. Gaver-Wainwright, Richard S. Zack, Matthew J. Foradori, and Laura Corley Lavine Journal of Medical Entomology 2011 48 (2), 382-388
  4. Photos © Jim Kalisch, University of Nebraska Department of Entomology used with permission
Wondering how to get that bug identified? Please see the kind folks at Bugguide.net. (North America)
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