Kauai Cave Wolf Spider

Adelocosa anops – The Kauai cave wolf spider is both rare and unusual. Found only in three caves on Kauai Island, Hawaii, the species is blind-unlike other wolf spiders that are known to hunt using their keen eyesight. Endangered from habitat de adation, it is also thought to be at risk from the pesticide residues seeping into its cave dwelling. Wolf spiders get their name from their habits as hunters. They are swift runners; instead of snaring their victims in silken webs like most other spiders, they rely on speed to chase their prey and run it down, although they may use silk to set up ambushes or “trip wires.” They stalk their prey, watching every movement. Once it is trapped, they bite the victim and inject poison through their fang-tipped chelicerae-the first pair of head appendages, which look like miniature elephant tusks when seen through a lens. The venom paralyzes the prey and also digests its tissues, reducing it to a liquid, which the spider can suck out and swallow through its small mouth; they feed particularly on insects such as beetles and ants.

There are many species of wolf spider: over 100 in North America and about 50 in Europe. The best-known wolf spider is probably the Mediterranean tarantula. The wolf spider’s enemies are wasps, birds, and people. The spiders occur on all continents apart from Antarctica and on many islands, too: Spiders are often among the leading colonizers of volcanic islands. Wolf spiders are not large and rarely exceed 1 inch (2.5 cm) in length. Their bodies are covered in short hair or bristles, and in the main they are brown or drab in color. As well as the fangs, the head carries a pair of pedipalps (small leglike appendages located in front of the first pair of long walking legs) and (usually) eyes arranged in three rows. Usually a favorite habitat is leaf litter on forest floors. The spiders excavate shallow burrows and line them with silk spun by the spinnerets on the abdomen. In some species the burrow has a projecting silk entrance tube. The Kauai cave wolf spider, however, is an exception among wolf spiders. It is restricted in its distribution, being found only at three underground locations on the island of Kauai. The caves in which it lives were formed by ancient volcanic lava flows.

Eyes Wide Shut

Although the eyes of most wolf spiders are fairly simple (they have four large and four small eyes), they generally have good eyesight. This is important, since many hunt in poor light conditions. The Kauai cave wolf spider, like many cave-dwelling species, is blind. More unusually, it is eyeless-many cave dwellers cannot see but have vestigial eyes. This makes the species unique. It almost certainly detects the presence of potential prey by touch and smell, and is able to stalk its prey by following their scent trails. Hunting has not been observed, but this species probably feeds primarily on the Kauai cave amphipod, a type of crustacean that is also Endangered. Other species of arthropod that enter the caves from time to time may serve as food for the Kauai cave wolf spider. Eyesight is usually an important tool in courtship and mating behavior for wolf spiders. How the Kauai cave wolf spider copes is unknown. After mating, the female Kauai cave wolf spider lays eggs-up to 30 at a time. They are laid in a round or oval silk cocoon made by the mother. She fastens it to the tip of her abdomen and carries it everywhere with her until the spiderlings hatch. The young climb onto the mother’s back and are carried by her until they are old enough to fend for themselves.

At Risk

As a result of its restricted distribution, the Kauai cave wolf spider is highly endangered. Habitat destruction has occurred through soil filling, quarrying, and other activities associated with development and agriculture. The seepage of pesticide residues into the caves is also thought to be a source of risk. In the delicately balanced environment such problems also affect the Kauai cave amphipod, the spider’s main prey. The amphipod feeds on rotting tree roots that work their way into the cave system. If the roots dry out or do not enter the cave, both species are affected. The Kauai cave wolf spider was added to the IUCN Red List in January 2000. Of the 15 spider species considered to be at risk, six are cave spiders: The tooth cave spider of Texas, for example, was listed as Endangered under the United States Endangered Species Act in 1988. It is the limitation of their habitat that makes wolf spiders especially threatened.

Kauai cave wolf spider Adelocosa anops

• Family: Lycosidae
• World population: Unknown. Surveys of the 3 remaining populations could only find 30 members of each at any one time
• Diet: Small, cave-dwelling crustaceansBreeding: Female lays up to 30 eggs after mating with male. Spiderlings hatch and ride on their mother’s back
• Distribution: Kauai Island, Hawaii
• Habitat: Dark, moist areas of Kauai cave system, formed from a lava flow and covering about 4 square miles (10 sq. km). About 75% of former habitat has been lost to human activity
• Size: Length: 0.5-0.7 in (1.3-1.9 cm); legs. 1 in (2.5 cm)
• Form: Head lacks eyes. Reddish-brown carapace (hard, outer covering); pale abdomen and bright-orange legs. Back part of chelicera (pair of fang-tipped appendages on head) has 3 large teeth
• Related endangered species: Glacier Bay wolf spider (Pardosa diuturna); Lake Placid funnel wolf spider (Sosippus placidus); rosemary wolf spider (Lycosa ericeticola)

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