The Kauai cave wolf spider (''Adelocosa anops'', the only species in the genus ''Adelocosa''), also known to local residents as the blind spider, is only known to occur in a few

caves A cave or cavern is a natural void in the ground, specifically a space large enough for a human to enter. Caves often form by the weathering of rock and often extend deep underground. The word ''cave'' can refer to smaller openings such as sea ...

in a lava flow with an area of in the Kōloa– Poipū region of Kauai, Hawaiian Islands, and only six populations are known to exist. While their nearest surface-dwelling relatives have large eyes, this species has completely lost its eyes. They reach a body length around , and are reddish brown and completely harmless to people. Unlike most

wolf spiders Wolf spiders are members of the family Lycosidae (). They are robust and agile hunters with excellent eyesight. They live mostly in solitude, hunt alone, and do not spin webs. Some are opportunistic hunters, pouncing upon prey as they find it or ...

, it produces only 15 to 30 eggs per clutch. The female carries the egg sac in her mouthparts until the spiderlings hatch. One of its primary prey species is the Kauaʻi cave amphipod, ''

Spelaeorchestia koloana ''Spelaeorchestia koloana'', the Kauai cave amphipod or ' in Hawaiian, is a cave-dwelling crustacean only found on the Hawaiian island of Kauai. It is eyeless and measures long. It is only known from 10 populations, and eats decaying plant ma ...

'', which is only known from nine populations and reaches about in length. These feed on decomposing plant matter. The Kauaʻi cave wolf spider was discovered in 1973. Counts have never documented more than 30 spiders or 80 amphipods.

Description

Adult Kauaʻi cave wolf spiders typically measure between 12.7 to 19.0 millimeters (0.5-0.75 inches) in length. The Kauaʻi cave wolf spider is the only wolf spider to completely lack eyes. It has a reddish brown to orange carapace with a pale abdomen and bright orange legs. Each leg has four pairs of short black spines and a thin coating of pale, silky hairs. The

chelicera The chelicerae () are the mouthparts of the subphylum Chelicerata, an arthropod group that includes arachnids, horseshoe crabs, and sea spiders. Commonly referred to as "jaws", chelicerae may be shaped as either articulated fangs, or similarly ...

has three large teeth used for biting prey.

Life history

Kauaʻi cave wolf spiders have a small clutch size compared to other wolf spiders. Kauaʻi cave wolf spiders only produce 15-30 eggs per clutch, whereas other terrestrial wolf spiders may have 100 to 300. Female Kauaʻi cave wolf spiders carry their egg sacs on their backs until their spiderlings hatch. Upon hatching, the large spiderlings will be carried on the back of the mother for several days. Kauaʻi cave wolf spiders have an adapted row of comb-like teeth on their claws. These align perfectly with the branched hairs of their mother's back and allow the spiderlings to hold onto the mother securely for protection and transport. This species takes up to a year to reach sexual maturity. At that time, the spiderlings are old enough to hunt for themselves and will disperse from the mother. Little is known about the mating strategies of Kauaʻi cave wolf spiders. Ecologists hypothesize that Kauaʻi cave wolf spider life history has been shaped by a behavior that allows other wolf spiders to fly through the air at short and long distances. Aerial dispersal is a behavior employed most often by young spiderlings, or

instars An instar (, from the Latin '' īnstar'', "form", "likeness") is a developmental stage of arthropods, such as insects, between each moult (''ecdysis''), until sexual maturity is reached. Arthropods must shed the exoskeleton in order to grow or ass ...

, though it has never been observed in Kauaʻi cave wolf spiders. However, there are close relatives to this species that are able to aerially disperse that inhabit the islands next to Kauaʻi. This suggests that Kauaʻi cave wolf spiders originated from an ancestor that came from other nearby Hawaiian islands. Dispersal mechanisms and behaviors allow individuals in a population to avoid competition for resources, unfavorable environmental conditions, and predation. Utilizing aerial dispersal would be dependent on the trade-off between the costs of landing in an unstable environment and the benefits of finding a new environment with fewer constraints or threats.

Ecology

Diet

The Kauaʻi cave wolf spider is an opportunistic feeder, meaning it feeds on other cave inhabitants whenever possible. Its diet may include the Kaua'i cave amphipod, as well as introduced spiders and cockroaches.U.S. Fish and Wildlife Service. 2006. Recovery Plan for the Kauai Cave Arthropods: the Kauai Cave Wolf Spider (Adelocosa anops) and the Kauai Cave Amphipod (Spelaeorchestia koloana). U.S. Fish and Wildlife Service. Portland, Oregon. 64 pp.

Behavior

The Kauaʻi cave wolf spider is slow-moving and spends most of its time standing still. Instead of building a web, the Kauaʻi cave wolf spider waits on the ground for prey. It senses prey through vibrations and chemical signals. Once it senses prey, the spider approaches and alternates raising its front legs vertically. Little information is available about the spider's mating behavior, but it is known that females carry the egg sac and care for the young.

Habitat

The Kauaʻi cave wolf spider is an obligate cave-dweller. It lives in large cave passages, small mesocaverns, and cracks that are inaccessible to humans. Since they can die of desiccation in low humidity, the Kauaʻi cave wolf spider requires a high humidity habitat. Because of this, they prefer to inhabit the dark and stagnant air zones of caves. These zones are characterized by high humidity, low air movement, and low temperature fluctuations.

Range

The Kauaʻi cave wolf spider is only found in the

Koloa Kōloa is an unincorporated community and census-designated place (CDP) in Kauai County, Hawaii, United States. The population was 2,231 at the 2020 census, up from 1,942 at the 2000 census. The first successful sugarcane plantation in the Hawa ...

Basin of the Hawaiian island of Kauaʻi. Within the island, Kauaʻi cave wolf spiders are only found in three caves regularly. These are called Koloa Cave 1, Koloa Cave 2, and Kiahuna Mauka Cave. Kauaʻi cave wolf spiders are also found in one experimental cave operated by the

US Fish and Wildlife Service The United States Fish and Wildlife Service (USFWS or FWS) is an agency within the United States Department of the Interior dedicated to the management of fish, wildlife, and natural habitats. The mission of the agency is "working with othe ...

, called Cave 3075C.

Conservation

The Kauaʻi cave wolf spider was first listed as endangered under the Endangered Species Act in 2000, after being proposed to be listed in 1997. Three 5-year reviews have been filed mentioning the Kauaʻi cave wolf spider in 2005, 2015, and 2020 which have considered the spider to still be endangered.

Threats

The Kauaʻi cave wolf spider is threatened by habitat modification, novel competition, and chemical runoff. Habitat modification is largely due to human development and interaction. Construction projects can expose caves to surface air and

desiccate Desiccation () is the state of extreme dryness, or the process of extreme drying. A desiccant is a hygroscopic (attracts and holds water) substance that induces or sustains such a state in its local vicinity in a moderately sealed container. ...

the subterranean environment. This also allows novel species like the

brown violin spider The Mediterranean recluse spider (''Loxosceles rufescens'') is a species of spider that originated in the Mediterranean region as its name implies, but can now be found in many parts of the world and is listed as one of the most invasive spiders w ...

to enter, which is known to outcompete with the native Kauaʻi cave wolf spider for prey. Development of agriculture and recreational areas, for example golf courses, change the surface vegetation composition above cave environments. This vegetation's shallow root composition decreases input of detritus into cave systems and increases sediment deposition. Recreational exploration of caves by humans also negatively impacts the delicate ecosystem of the cave as well.

Recovery

A recovery plan published in 2006 stated that the Kauaʻi cave wolf spider would be delisted as endangered when 12 populations of the spider are observed to have the following conditions: stable, self-sustaining, protected from human interference, and its habitat being utilized in a manner conducive to conservation. Recovery actions to meet this goal include protecting known populations from human-induced degradation, enhancing habitats known previously to have populations, conducting research to identify species-specific conservation strategies, educating the public on conservation efforts, and validating current conservation practices.

References

{{DEFAULTSORT:Kaua'i cave wolf spider Lycosidae Cave spiders Spiders of Hawaii Biota of Kauai Endemic fauna of Hawaii Endangered fauna of Hawaii ESA endangered species Taxa named by Willis J. Gertsch