Nursery Web Spiders

Media
Photo of a nursery web spider on a plant
Scientific Name
Pisaurina spp.
Family
Pisauridae (fishing and nursery spiders) in the order Araneae (spiders)
Description

Four species of nursery web spiders in genus Pisaurina occur in North America north of Mexico. These streamlined spiders have long legs, slender bodies, and, often, lengthwise striping, helping them blend in with plant or grass stalks when they position themselves with legs outstretched before and behind them. Often, the front two pairs of legs are held together. Depending on species, growth stage, and individual color forms, the color ranges from blackish to brown, tan, rusty, grayish, or yellowish, and markings can vary, too. The hairs on their bodies and legs looks a little like suede.

Similar species: Fishing spiders in genus Dolomedes are in the same family as nursery web spiders, Pisauridae. This family is distinguished from the similar-looking wolf spiders (family Lycosidae) by carrying their egg sacs in their mouths (jaws or pedipalps) as opposed to attaching them to their spinnerets as wolf spiders do. Also, nursery web and fishing spiders have all eight eyes about the same size, while wolf spiders have two eyes that are noticeably larger.

Common Name Synonyms
Fishing Spiders
Size
Length (not including legs): about ½ to ¾ inch; males are smaller.
Where To Find
Statewide.
Nursery web spiders are usually seen among the foliage of plants, as opposed to walking on the ground as wolf spiders usually do. They occur in grasslands, woodland borders, fencerows, roadsides, parks, and gardens and landscaping shrubs. Nursery web spiders are closely related to fishing spiders, and many species in this group can walk or run across the water’s surface if necessary.
Nursery web spiders use their silk for constructing protective structures for their egg sacs, but otherwise they are not web builders. They get their insect food by hunting for it — either walking around and grabbing prey, or by standing motionless and waiting for prey to come by.
The genus name, Pisaurina (pronounced py-saw-RYE-nuh), is based on the related Eurasian genus Pisaura, which apparently referred to either the Pisaurus (Foglia) River or the city of Pesaro, both in Italy.
Life Cycle
Nursery web spiders got their common name because the spider mother builds a little tent to protect her egg sac. Often, it is well off the ground, among the leaves of a milkweed plant, for example. The tent can take the form of a folded-over leaf, held in place by a network of silk, with the egg sac safe within. The mother spider typically holds the sac in her jaws, protecting it with her body; often, she stands guard outside the tent. Showing strong maternal instincts, she remains with them, protecting them, until they have hatched and are ready to disperse.
Nursery web spiders are harmless to humans. They do us a great service by eating garden pests and other obnoxious insects, naturally controlling their populations. Their strong maternal instincts give us reason to admire their innate loyalty to their offspring.
When an animal blends in with its surroundings, it is likely facing predation pressure, or its hunting success requires surprise attacks. In the case of nursery web spiders, both are probably the case. The spider’s behavior of spinning protective tents and then guarding the eggs and young is a way to prevent predators from devouring them.
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About Land Invertebrates in Missouri
Invertebrates are animals without backbones, including earthworms, slugs, snails, and arthropods. Arthropods—invertebrates with “jointed legs” — are a group of invertebrates that includes crayfish, shrimp, millipedes, centipedes, mites, spiders, and insects. There may be as many as 10 million species of insects alive on earth today, and they probably constitute more than 90 percent all animal species.