Nursery web spider

The family of nursery web spiders does not build webs to live or catch food. Their name comes from each female's habit of spinning a silken tent around her egg-case which she attaches to vegetation. She guards her spiderlings until they leave the safety of their nursery web.

Kingdom: Animalia

Phylum: Arthropoda

Class: Arachnida

Order: Araneae

Family: Pisauridae

Genus: Various (see below)

Species: Various (see below)

The Pisauridae spider family has over 500 species worldwide living in various habitats. A few are aquatic, or water-dwelling. Most members of the Pisauridae family live on the ground or amongst vegetation.

Nursery web spiders receive their name from the habits of the females. After mating, a female produces a large, round silken egg sac. She attaches it to the spinnerets on the underside of her abdomen, or lower body section, and grasps it in her jaws. Spinnerets are the silk-spinning organs of spiders. She carries the egg sac with her until the young are ready to hatch. The egg sac is so large the female's legs are barely long enough to reach the ground to walk. She frequently airs and warms the egg sac in the sun to prevent mold from growing on the case and speed up the hatching process.

Shortly before the spiderlings hatch, the female attaches the egg sac to grassy, sheltered vegetation and spins a silken tent around the sac. She guards them until they hatch while the spiderlings remain inside their nursery web. The spiderlings molt, or shed their skins, and leave after about a week. After a few molts, they are adults and probably live one to two years.

Each nursery web spider has three main body sectionsthe head, thorax, or middle section, and abdomen, or tail section. The abdomen is sometimes called the opisthosoma. The head and thorax are usually combined into one section called the cephalothorax or prosoma. Eight long, slender legs extend from the cephalothorax. The head has eight eyes to see in every direction. At the front of the head are two extensions called pedipalps for sensing. The spider's two jaws are called chelicerae and are poisonous fangs.

Like other spiders, nursery web spiders have tiny openings on the undersides of their abdomens. These are called spinnerets and are silk-producing organs. Though they have spinnerets and produce silk, nursery web spiders do not spin webs in which they live and trap prey. Instead, they are hunters that scurry quickly across the ground or among vegetation. Their eight eyes provide them with excellent vision. When they see insect prey, they stalk it slowly and speedily pounce. A bite from the poisonous fangs immediately paralyzes the insect, and the spider's digestive juices then begin to flow into the prey and turn its insides into liquid. The spider sucks the liquid and leaves the carcass.

Species in the genus Dolomedes of this family are aquatic, or water-dwelling. These species can run across the surfaces of ponds and lakes to catch insects that have fallen onto the water. They may dip their legs into the water as lures to tadpoles and small fish and then pounce on these prey. Such species are called fishing spiders in the United States and swamp spiders in Great Britain.

As with most other spiders, birds are significant predators of nursery web spiders.

Species include:

American nursery web spider Pisaurina mira

Clever fishing spider Dolomedes facetus

Fishing spider Nilus albocinctus

Great or fen raft spider Dolomedes plantarius

Nursery web spider Dolomedes minor

Raft spider Dolomedes fimbriatus,

White-banded fishing spider Dolomedes albineus

Bibliography

"Nursery Web Spiders." The Wildlife Trusts, www.wildlifetrusts.org/wildlife-explorer/invertebrates/spiders/nursery-web-spider. Accessed 1 May 2024.

Torres, C. "Pisaurina Mira." Animal Diversity Web, animaldiversity.org/accounts/Pisaurina‗mira. Accessed 1 May 2024.