Thin-legged wolf spiders are considered large wolf spiders. This species exhibits sexual dimorphism, meaning that females and males can be told apart by their appearance. In this case, females are slightly larger than males. Females are generally 6.9 to 8.6 mm in length, while males are 5.9 to 7.1 mm in length. Like all wolf spiders (Lycosidae), thin-legged wolf spiders have a high arched body and long legs, with 3 claws. They have three rows of eyes; the first row on the lower part of their face has four eyes, just above are two large eyes, and two medium sized eyes are placed farther back. Their brown cephalothorax (the front section of their body) has a light brownish-red band going down the center, with wide dark brown stripes on either side. The light brownish-red band continues down the center of their abdomen, though wider, and flanked by narrower dark stripes. Their eye region is black and their legs have dark brown or black alternating rings. Females and males are similarly colored. Immature spiderlings have white hairs that form a V-shape on the middle section of their body. Members of their genus, Pardosa, have similar coloring, but can be identified by differences in their genitalia. (Buddle, 2000; Chamberlin, 1908; Vogel, 2004)
Thin-legged wolf spiders (Pardosa mackenziana) are native to the Nearctic region and are common throughout North America. They are widespread across Canada and can be found across the northern half of the United States, from coast to coast. Their range goes as far south as Colorado and northern California. They also live in Alaska. (Aitchison and Sutherland, 2000; Buddle, 2000; Buddle, 2001; Buddle, 2002; Jennings, et al., 1988; Vogel, 2004)
Thin-legged wolf spiders live on the ground in temperate regions. They typically live on forest floors and can often be found on woody material such as downed logs. Their habitat includes both deciduous and coniferous forests, as well as salt marshes, bogs, and beaches. Thin-legged wolf spiders can also be found in Canada's taiga and alpine tundra. They have been recorded at elevations as high as 3,500 m. During the winter, they live in dead leaf litter. (Buddle, 2000; Buddle, 2001; Buddle, 2002; Schmoller, 1970)
Female thin-legged wolf spiders carry their egg sacs. Once the eggs hatch, anytime from late May to July, the spiderlings ride on the back of the female's abdomen until late June or late July, when they leave their mother and become independent. These immature spiderlings typically spend the winter in leaf litter from late September or October and become active again the next April. Populations in northern regions, particularly Canada, have two year development cycles. Sub-adults in these populations go into hiding for a second winter, which is called overwintering. Populations in the southern region of their range, such as Colorado, have one year cycles and only overwinter once. Once sub-adults have emerged from overwintering, they shed their skin (molt) and enter their reproductive adult phase. Mating occurs in the early spring. Males die shortly after their mating period, while females survive into the summer to carry and protect egg sacs and hatched spiderlings. Adults forage for food from April to September, but their population is typically largest from May to June. (Buddle, 2000; Buddle, 2002; Schmoller, 1970)
While there is little information specific to the mating habits of thin-legged wolf spiders, mating habits for wolf spiders (Lycosidae) in general are known. Males typically climb on top of females so they are facing opposite directions. Females must twist their abdomen so that males can reach around to the underside of their abdomen. Males use their pedipalps to transfer sperm to the females' genitals, also known as their epigynum. Thin-legged wolf spiders mate in May and June, after the sub-adults that overwintered have molted into their reproductive phase. Mating may last about 60 minutes. While it is unknown how this species finds and attracts mates, females from other wolf spider species use pheromones or other chemicals to attract males. Often a contact pheromone is used that males can detect with chemical detectors on their forelegs and palps. Vision and vibrations may also be used to find mates. (Buddle, 2002; Jiao, et al., 2011; Stratton, et al., 1996; Wilder and Rypstra, 2007)
After mating in May and June, female thin-legged wolf spiders begin constructing an egg sac. They first spin a circular disc of web from their spinnerets on the ground. They make it larger and lay their eggs in the center. They spin a covering disc on top of the eggs, connecting it with the bottom disc, to form a sac and use their mouthparts, called chelicerae, to detach the sac from its surroundings. Fresh threads are laid over it and females carry it under their abdomen by their spinnerets into the summer. The average number of eggs per sac is 48, though this number is highly affected by the size and health of the female parent. A female thin-legged wolf spider can lay up to 2 egg sacs, though the second egg sac typically contains fewer eggs. The eggs in the second sac are heavier, containing more nutrients for the offspring, who will have less time to grow and develop before winter. Once hatched, the spiderlings ride on the female's abdomen, leaving when they become independent, usually in late summer and into autumn. (Buddle, 2000; Buddle, 2002; Chamberlin, 1908)
Female thin-legged wolf spiders invest a large amount in parental care, as do most female wolf spiders. Adults provide nutrients in the eggs. The eggs are laid in an egg sac, which the female carries with her. Females with egg sacs are often found on wooded surfaces, such as dead logs, in the sun. They are likely sunning the egg sac, perhaps to speed egg development by increasing the temperature. Females can lay up to two egg sacs, though the second egg sac usually contains fewer eggs. Eggs in the second egg sac are often heavier because they contain more nutrients than eggs in the first sac. Since the second egg sac hatches much later in the season, these offspring have less time to grow and develop before winter, so they need these extra nutrients to make sure they survive. Once the eggs hatch, the spiderlings climb to the female's abdomen. Females carry the young spiderlings, protecting them until they disperse. Spiderlings typically leave the female parent after about a week; those from the first egg sac leave their mother in late June to late July. (Buddle, 2000; Buddle, 2001; Buddle, 2002)
Populations in the far north have two year development cycles, while populations farther south typically develop in one year. Males die shortly after they reproduce, while females live longer, though probably less than a year. (Buddle, 2000; Buddle, 2002)
Thin-legged wolf spiders are solitary predators, living mainly on the ground, though females can often be found on surfaces such as downed logs in the sun. Females likely sun their egg sacs. Spiderlings can be found in leaf litter during the winter. Wolf spiders (Lycosidae) are 'sit and wait' predators, waiting for prey to move past, then using their speed, long legs, and powerful, venomous bite to catch the prey. Researchers have found evidence of cannibalism in populations of thin-legged wolf spiders. (Buddle, 2000; Buddle, 2002; Persons and Uetz, 1999)
A study in Alberta, Canada found that there are about 0.6 thin-legged wolf spiders per square meter. This spider does not seem to defend their territory, as there can be many spiders in an area and ranges of different spiders likely overlap. Their home range is only limited by how far they can move along the ground. (Buddle, 2000)
While there is little information specific to this species, much is known about communication and perception of wolf spiders in general. They have three rows of eyes that are well developed, allowing them to see prey and mates, though their eyes generally detect movement better than forms. Wolf spiders have hairs on their legs that can detect chemicals. These hairs are used to detect prey, mates, and other individuals. Male wolf spiders, which also have these hairs on their palps, feel the ground with their legs to detect chemicals and odors. Males often begin courtship motions after finding pheromones and chemicals left by mature females that have recently passed over the same substrate. To find prey, wolf spiders detect their motion using their vision. They can also see flashing or moving lights, or use chemical detection. Vibrations may be the most important information source when searching for prey. These spiders can detect vibrations in the air and on objects. Vibrations are also used for communication between mates. (Chamberlin, 1908; Jiao, et al., 2011; Kronestedt, 1979; Lizotte and Rovner, 1988; Persons and Uetz, 1999; Stratton, et al., 1996)
Thin-legged wolf spiders are predatory insectivores. They are strong hunters and are usually 'sit and wait' predators. They typically move very quick, using their long legs to grab prey that moves past. Wolf spiders also have a venomous bite and large mouthparts that can do significant damage. Thin-legged wolf spiders feed on many types of insects and other arthropods, including herbivores, detritivores, omnivores, and other predators. They also likely practice cannibalism at some point in their life cycle. (Buddle, 2002; Chamberlin, 1908; Fagan, 1997; Livshits, et al., 2012; Persons and Uetz, 1999)
There is little information available about predators of thin-legged wolf spiders. As predators themselves, thin-legged wolf spiders likely have to deal with few predators. Predation by other arthropods has been reported as insignificant even for young spiderlings. Cannibalism and predation between other species of wolf spiders are possible threats. The brown colors and patterns of these wolf spiders may act as camouflage as they move across the ground. (Buddle, 2002)
Thin-legged wolf spiders are significant predators to many species of insects and other arthropods. They have very high numbers in many areas, particularly in Canada, where there may be almost one spider per square meter. This species is often found in the same habitat with another wolf spider, Pardosa moesta, in Canada. There is thought to be little competition between the two species, as they use different resources, but they can usually be found living closely together. Wasps of genus Gelis parasitize the egg sacs of northern Pardosa species that are closely related to and from the same region as thin-legged wolf spiders. These parasitoids lay their own eggs in the spider egg sacs, which destroys the egg sac. These wasps likely also parasitize egg sacs of thin-legged wolf spiders. (Bowden and Buddle, 2012; Buddle, 2000; Buddle, 2002; Chamberlin, 1908; Fagan, 1997)
While there are no reports of thin-legged wolf spiders biting humans, wolf spiders in general are known to have potentially painful and venomous bites. Their large mouthparts may cause more damage than their venom. Bites can cause pain, swelling, redness, and sores. In extreme cases, bites may need medical attention to heal. Thin-legged wolf spiders can likely also deliver a venomous bite to humans, but it is probably rare and only when they feel threatened. (Livshits, et al., 2012)
There are no known positive effects of thin-legged wolf spiders on humans.
Thin-legged wolf spiders are not an endangered species.
Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Animal Diversity Web Staff.
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