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Pardosa milvina

By Austen Ross

Geographic Range

A common and widespread spider in North America, Pardosa milvina can be found in the United States from New England to Florida and west to the Rocky Mountains. It is most common in the eastern third of Texas between the months of May and September. (Foelix, 1982; Jackman, 1997)

Habitat

This wolf spider can be found in grasslands, dry open woods and also in wet grounds along streams and ponds. Recently, P. milvina has been found among various agricultural crops. This spider does not create a snare or web. Rather, it is somewhat nomadic, resting under rocks and grass in between hunting. (Jackman, 1997)

Physical Description

Wolf spiders (family Lycosidae), are among the most common spiders worldwide. Their colors range from black to brown or tan with lengthwise dark and light stripes. Their eyes (they have eight) are arranged in three rows of four, two, and two. The anterior eyes (those in the first row) are smallest, and are in a straight line. The middle row has the largest eyes, and the eyes in most posterior row can be nearly as big as those in the middle. All eyes are dark in color.

The genus Pardosa is large, and itan be difficult to differentiate between species in this genus. In fact, only an expert can reliably tell members of the genus from one another. P. milvina does exhibit certain traits that distinguish it from other wolf spiders. The legs are long and thin with extremely long spines. Scopulae are claw tufts on spiders' legs that aid them in gripping during locomotion. This spider does not possess scopulae and therefore cannot climb smooth surfaces. The cephalothorax is highest in the head region, or carapace. Chelicerae are much smaller than in other wolf spiders, measuring 4 to 9.5 mm. The dorsal stripes common to wolf spiders are more wavy than in other species. The abdomen has yellow spots. Sexual dimorphism exists in this species. The males have white hairs on the patella of the legs. These spiders are considered small. The length of females ranges from 5.1 to 6.4 mm and male length ranges from 4.3 to 5.0 mm. (Jackman, 1997; Milne and Milne, 1980)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • Range length
    4.3 to 6.4 mm
    0.17 to 0.25 in

Reproduction

Male wolf spiders mature in spring and perform elaborate courtship dances on sunny days. A male waves at a female vigorously with both pedipalps (legs), raises them, and at the same time performs a few dancing steps. Males must be cautious in their approach, for a female may decide he is food and not a mate. If he succeeds, the male then mounts the female's back, inserting his pedipalp into the epygynum of the female and transferring sperm. (Foelix, 1982; Jackman, 1997; Milne and Milne, 1980; Preston-Mafham and Preston-Mafham, 1996; Foelix, 1982; Grzimek, 1972; Milne and Milne, 1980; Nichols and Cooke, 1971; Preston-Mafham and Preston-Mafham, 1996)

Eggs are laid soon after mating and are bundled in an oval-shaped, compact silk egg sac or cocoon. The cocoon is green primarily, and then turns to dirty gray. Females carry the egg sac at all times, attached to the spinnerets. This leaves her jaws free for action at all times. Female wolf spiders are well known for their care of offspring. When the cocoon is mature, the mother rips it open, aiding her babies in emerging. The offspring climb onto their mother's back. Babies can number more than one hundred; so several layers are formed on the mother. Here they remain there for approximately one week before leaving to fend and feed for themselves. (Foelix, 1982; Grzimek, 1972; Milne and Milne, 1980; Nichols and Cooke, 1971; Preston-Mafham and Preston-Mafham, 1996)

  • Range number of offspring
    100+ (high)
  • Average time to independence
    1 weeks

Female wolf spiders are known to provide fairly extensive parental care to their young. Females carry their egg sac with them, providing the developing young with protection. When the young spiders hatch, a female helps them to emerge from the egg sac. The newly hatched young are carried on the mother's back for about one week. (Foelix, 1982; Grzimek, 1972; Milne and Milne, 1980; Nichols and Cooke, 1971; Preston-Mafham and Preston-Mafham, 1996)

  • Parental Investment
  • precocial
  • pre-fertilization
    • provisioning
    • protecting
      • female
  • pre-hatching/birth
    • protecting
      • female
  • pre-independence
    • protecting
      • female

Behavior

Pardosa milvina does not build a shelter. It roams freely over stones and among grasses and other low vegetation. This spider has a small territory. Basking in the sun often helps this spider to keep its body temperature high and to be ready for pursuit of prey. Pardosa milvina typically reacts to vibrations from both birds of prey and other predators as well as from possible prey for the spider. Having eight eyes, one might think that visual stimuli heavily affect P. milvina. However, the eyes of this wolf spider only allow it to see coarse objects, the exception being when objects are extremely close.

When two male wolf spiders encounter one another in the presence of a female, they get into threatening stances and sometimes will fight. The attacking male is usually the winner and will appear to flaunt his superiority with jerking movements. A selective advantage is associated with this practice: the winner has better chances of mating with a female. (Foelix, 1982; Milne and Milne, 1980)

Communication and Perception

Visual and tactile communication occur during courtship. Visual stimuli are important to this species in capturing prey. These spiders respond to vibrations. (Foelix, 1982; Grzimek, 1972; Foelix, 1982; Jackman, 1997; Milne and Milne, 1980)

Food Habits

Like most every spider, P. milvina is carnivorous. Previously thought of as active hunters, this wolf spider appears to obtain food more often as a "sit-and-wait" predator. This makes P. milvina a bit different from most other wolf spiders, which tend to hunt by sight and chase prey. Wolf spiders are so named because of the way in which they pounce on their prey with great speed and strength. The spider then envenoms its prey with fangs, at the same time puncturing the body so it may suck the body fluids. Staying near the ground during the day, large numbers have been found feeding in cotton fields at night. Common food includes the cotton fleahopper, insect eggs, crickets, locusts, ants, grasshoppers, and other spiders. Pardosa milvina eats about 3.5 mg of insects daily, equivalent to 12% of its body weight. (Foelix, 1982; Preston-Mafham and Preston-Mafham, 1996)

  • Animal Foods
  • body fluids
  • insects
  • terrestrial non-insect arthropods

Economic Importance for Humans: Positive

Most believe that P. milvina benefits humans by limiting insect and pest populations. Like most other spiders, P. milvina is a generalist, eating a variety of other animals (mostly other invertebrates). This leads some to believe that this increases the spider's effectiveness as a population limiter. Yet others feel that since the spider does not specialize in any single species and does not live in colonies, it cannot effectively limit the populations of pests. Thus, although P. milvina shows behaviors which are of potential benefit to humans, it is difficult to determine the extent of the actual benefit provided. (Foelix, 1982)

  • Positive Impacts
  • controls pest population

Economic Importance for Humans: Negative

This spider is able to bite humans if defending itself. These bites can cause skin irritation or possibly lesions. (Jackman, 1997)

  • Negative Impacts
  • injures humans
    • bites or stings

Conservation Status

This species is not a special conservation concern.

Other Comments

There are approximately 2,500 species of wolf spiders worldwide. (Foelix, 1982)

Contributors

Nancy Shefferly (editor), Animal Diversity Web.

Austen Ross (author), Southwestern University, Stephanie Fabritius (editor), Southwestern University.

Glossary

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

agricultural

living in landscapes dominated by human agriculture.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

ectothermic

animals which must use heat acquired from the environment and behavioral adaptations to regulate body temperature

fertilization

union of egg and spermatozoan

forest

forest biomes are dominated by trees, otherwise forest biomes can vary widely in amount of precipitation and seasonality.

insectivore

An animal that eats mainly insects or spiders.

internal fertilization

fertilization takes place within the female's body

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

riparian

Referring to something living or located adjacent to a waterbody (usually, but not always, a river or stream).

sedentary

remains in the same area

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

solitary

lives alone

suburban

living in residential areas on the outskirts of large cities or towns.

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

terrestrial

Living on the ground.

tropical savanna and grassland

A terrestrial biome. Savannas are grasslands with scattered individual trees that do not form a closed canopy. Extensive savannas are found in parts of subtropical and tropical Africa and South America, and in Australia.

savanna

A grassland with scattered trees or scattered clumps of trees, a type of community intermediate between grassland and forest. See also Tropical savanna and grassland biome.

temperate grassland

A terrestrial biome found in temperate latitudes (>23.5° N or S latitude). Vegetation is made up mostly of grasses, the height and species diversity of which depend largely on the amount of moisture available. Fire and grazing are important in the long-term maintenance of grasslands.

vibrations

movements of a hard surface that are produced by animals as signals to others

visual

uses sight to communicate

young precocial

young are relatively well-developed when born

References

Foelix, R. 1982. Biology of Spiders. Cambridge: Harvard University Press.

Grzimek, B. 1972. Grzimek's Animal Life Encyclopedia. New York: Van Nostrand Reinhold Company.

Jackman, J. 1997. A Field Guide to Spiders and Scorpions of Texas. Houston: Gulf Publishing Company.

Milne, L., M. Milne. 1980. The Audubon Society Field Guide to North American Insects and Spiders. New York: Alfred A. Knopf, Inc..

Nichols, D., J. Cooke. 1971. The Oxford Book of Invertebrates. Oxford: Oxford University Press.

Preston-Mafham, K., R. Preston-Mafham. 1996. The Natural History of Spiders. Ramsbury: The Crowood Press.

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