Pardosa mackenziana

Geographic Range

Thin-legged wolf spiders ( Pardosa mackenziana ) are native to the Nearctic region and are widely distributed in 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 extends as far south as Colorado and northern California. They are also present in Alaska.

• Biogeographic Regions
• nearctic nearctic
  • native native

Habitat

Thin-legged wolf spiders are ground-dwelling spiders found 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. They overwinter in dead leaf litter.

• Habitat Regions
• temperate temperate
• terrestrial terrestrial

• Terrestrial Biomes
• tundra tundra
• taiga taiga
• forest forest

• Wetlands
• marsh marsh
• bog bog

Physical Description

Thin-legged wolf spiders are considered large wolf spiders. This species exhibits sexual dimorphism, with females being 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 ), this species has a high arched cephalothorax and long legs, with 3 claws on their tarsi. 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 has a light brownish-red band going down the center of the dorsal side, with wide dark brown stripes on either side. The light brownish-red band extends 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 setae that form a V-shape on the median section of their carapace. Members of this genus, Pardosa , have similar coloring, but can be identified by their copulatory organs. Females can be distinguished by their epigynum, which is almost as wide as it is long. In males, the tip of the median apophysis on the palp is tapered and notched.

• Other Physical Features
• ectothermic ectothermic
• heterothermic heterothermic
• bilateral symmetry bilateral symmetry
• venomous venomous

• Sexual Dimorphism
• female larger

Development

Female thin-legged wolf spiders carry their egg sacs. Once the eggs hatch, from late May to July, the spiderlings ride on the female's abdomen until late June or late July, when they disperse and achieve independence. These immature spiderlings typically overwinter in leaf litter from late September or October and emerge the next April. Populations in northern regions, particularly Canada, have two year development cycles. Sub-adults in these populations overwinter a second time. 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 molt into their reproductive adult phase. Mating occurs in the early spring. Males die shortly after their reproductive period, while females survive into the summer to carry and protect the egg sacs and the hatched spiderlings. Adults forage from April to September, but their population size typically peaks from May to June. Their number of instars is likely flexible, depending on the time of year that the eggs hatch. Since the mating period is consistent each year and eggs can hatch any time over a three month period in the summer, spiderlings that hatch later in the season have less time to grow and develop before overwintering. Regardless of when they hatch, all spiderlings are ready to mate in the spring, either one or two years later, depending on the region.

• Development - Life Cycle
• metamorphosis metamorphosis

Reproduction

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 mount females so that they are facing opposite directions. Females must twist and invert their abdomen so that males can reach around to the ventral side of their abdomen. Males use their pedipalps to transfer sperm into the females' epigynum. Thin-legged wolf spiders mate in May and June, after sub-adults that overwintered have molted into their reproductive phase. Mating may reportedly last about 60 minutes in this species. While the catalysts of mate attraction are unknown in this species, females from other wolf spider species, including other species of Pardosa , use pheromones or other chemicals to attract males. Contact pheromones are often used; males detect these pheromones with chemoreceptors on their forelegs and palps. Visual and vibratory cues may also be used.

After mating in May and June, female thin-legged wolf spiders begin constructing an egg sac. First, they spin a circular disc of web from their spinnerets on the ground, attaching it to the substrate. Then, they enlarge it 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 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. Their average clutch size is 48, though clutch size is highly affected by the size and health of the female parent. Female thin-legged wolf spiders can lay up to 2 egg sacs, though the second egg sac typically contains fewer eggs. Eggs in the second sac are heavier, containing more provisionings for the offspring who will have to overwinter after a shorter development period. Once hatched, spiderlings ride on the female's abdomen, leaving when they become independent, usually in late summer and into autumn.

• Key Reproductive Features
• semelparous semelparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• fertilization fertilization
  • internal internal
• oviparous oviparous

Female thin-legged wolf spiders invest a significant amount in parental care, as do most female wolf spiders. Adults provide provisioning in the eggs. The eggs are laid in an egg sac, which the female carries with her. Females with egg sacs can often be found on wooded surfaces, such as dead logs, in the sun. They are likely sunning the egg sacs, perhaps in an attempt to speed 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 than eggs from the first egg sac, indicating that these eggs contain more provisioning. Since the second egg sac hatches much later in the season, these offspring have significantly less time to grow and develop before they overwinter, so the extra provisioning can be vital to survival. 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 disperse in late June to late July.

• Parental Investment
• female parental care female parental care
• pre-hatching/birth
  • provisioning
    • female
  • protecting
    • female
• pre-independence
  • protecting
    • female

Lifespan/Longevity

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.

Behavior

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. It is thought that females sun their egg sacs. Spiderlings can be found overwintering in leaf litter. Wolf spiders are typically 'sit and wait' predators, waiting for prey to move past, they utilize their speed, long legs, and powerful, venomous bite to catch prey. Researchers have also found evidence of cannibalism in populations of thin-legged wolf spiders.

• Key Behaviors
• terricolous
• motile motile
• hibernation hibernation
• solitary solitary

Home Range

A study in Alberta, Canada found that thin-legged wolf spiders have an average density of 0.6 per square meter. This spider does not seem to be territorial, as density can be high and ranges likely overlap. Their home range is only limited by how far spiders can move along the ground.

Communication and Perception

While there is little information specific to this species, much is known about the communication and perception of wolf spiders in general. These spiders have three rows of eyes that are strongly developed, allowing them to see prey and mates, though their eyes generally detect movement better than forms. Wolf spiders have chemoreceptive hairs on their legs. These hairs are used to detect prey, mates, and other individuals. Male wolf spiders, which also have chemoreceptors on their palps, have been observed feeling the ground or other substrates with their legs to detect chemicals and odors. Males often begin courtship motions after detecting pheromones and chemicals left by females that have recently passed over the same substrate. To find prey, wolf spiders visually detect their motion, responding to stimuli such as flashing or moving lights. Chemical detection of prey is also utilized. Vibrations may be the most important information source when searching for prey. These vibrations can be detected by mechanoreceptors through both substrate and air. Vibratory cues are also used for communication between mates.

• Communication Channels
• visual visual
• chemical chemical

• Other Communication Modes
• pheromones pheromones
• vibrations vibrations

• Perception Channels
• visual visual
• vibrations vibrations
• chemical chemical

Food Habits

Thin-legged wolf spiders are predatory insectivores. Wolf spiders are avid 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 chelicerae that can do significant mechanical damage. Thin-legged wolf spiders feed on many species of insects and other arthropods , including herbivores, detritivores, omnivores, and other predators. They also likely exhibit cannibalism at some point in their life cycle.

• Primary Diet
• carnivore carnivore
  • insectivore insectivore

• Animal Foods
• insects
• terrestrial non-insect arthropods

Predation

There is little information available about predators of thin-legged wolf spiders. As a significant predator itself, they likely have to deal with few predators. Predation by other arthropods has been reported as insignificant even for young spiderlings. Cannibalism and intraguild predation between other species of wolf spiders are a potential threat. The brown colors and patterns of these spiders may function as camouflage as they move across the ground.

Ecosystem Roles

Thin-legged wolf spiders are significant predators to many species of insects and other arthropods. They have a very high density in many areas, particularly in Canada, where average density is 0.6 per square meter. This species is sympatric with another wolf spider, Pardosa moesta , in Canada. There is thought to be little direct competition between the two species, as they occupy different niches, but they can usually be found living in close proximity. 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 destroy the egg sac. These wasps also likely parasitize egg sacs of thin-legged wolf spiders.

Economic Importance for Humans: Positive

There are no known positive effects of thin-legged wolf spiders on humans.

Economic Importance for Humans: Negative

While there is no documentation of this species biting humans, wolf spiders in general are known to have potentially painful and venomous bites. Their large chelicerae may cause more damage than their venom, making the bite damage more mechanical in nature. Bites can cause pain, swelling, redness, and ulceration. In extreme cases, they can require medical attention. It is likely that thin-legged wolf spiders can also inflict a venomous bite to humans, though rarely and probably only when feeling threatened or provoked.

• Negative Impacts
• injures humans
  • bites or stings
  • venomous venomous

Conservation Status

Pardosa mackenziana has no special conservation status.

Additional Links

Encyclopedia of Life

BioKIDS Critter Catalog

Contributors

Angela Miner (author), Animal Diversity Web Staff, Leila Siciliano Martina (editor), Texas State University.

References

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