Tuesday, October 2, 2012

Wolf Spiders

Wolf spiders
(Lycosidae)


photo via http://bit.ly/Q6ZEAW

Wolf spiders are members of the family Lycosidae, from the Ancient Greek word "λύκος" meaning "wolf". They are robust and agile hunters with excellent eyesight. They live mostly solitary lives and hunt alone. Some are opportunistic hunters pouncing upon prey as they find it or even chasing it over short distances. Some will wait for passing prey in or near the mouth of a burrow.
Wolf spiders resemble Nursery web spiders (family Pisauridae), but wolf spiders carry their egg sacs by attaching them to their spinnerets (Pisauridae carry their egg sacs with their chelicerae and pedipalps). Two of the Wolf spider's eight eyes are large and prominent, which distinguishes them from the Nursery web spiders whose eyes are all of approximately equal size. (Wikipedia)

Appearance: These are usually large spiders. Wolf Spiders can range from 3-30 mm in body length. Female wolf spiders are often bigger than males of the same species.


photo via http://bit.ly/OBvibU 


Like all spiders they have two body sections: the cephalothorax in front and an abdomen behind. The abdomen contains the digestive and reproductive systems, and on the underside of it are the glands where silk is produced. The structures that produce the silk are called spinnerets.

Wolf spiders have eight legs, all attached to the cephalothorax. On the front of the cephalothorax are the mouth, the fangs, the eyes, and two small "mini-legs" called pedipalps. These are used to grab prey, and in mating, and are much bigger in male spiders than in females. They have eight eyes in three rows. The front row has four small eyes, the middle row has two much larger eyes, and the back two eyes are medium sized and off to the sides. These spiders have strong fangs and and venom glands to quickly kill their prey.

Wolf spiders are colored in camouflage colors of brown, orange, black, and grey. Sometimes they are all one color, but usually they have some stripes or blotches.

Wolf spiders are found all around the world, and about 2,300 species are known. There are about 50 species of wolf spiders in Michigan.

Wolf spiders live in all kinds of habitats, anywhere there are insects to eat. They seem to be most common in open habitats like grasslands, and are often found in farm fields and meadows. Most species stay on the ground, but a few climb up onto trees and other plants when hunting. Some wolf spiders hunt along the shores of ponds and marshes, and may even dive into the water to capture prey.

These spiders can be found in the following types of habitat: temperate; tropical; terrestrial.
Terrestrial Biomes: taiga; desert or dune; chaparral; forest; rainforest; scrub forest; mountains.
Aquatic Biomes: lakes and ponds.
Wetlands: marsh; swamp.

Wolf spiders hatch from eggs, and the hatchlings look more or less like grown-up spiders, though sometimes their colors change as they age. In many species, the hatchlings ride on their mother's body for some time before going off on their own. To grow, spiders must shed their exoskeleton, which they do many times during their lives. Unlike insects, some spider species keep growing after they become adults, and continue to molt as they grow even larger.

After mating, female wolf spiders lay a batch of eggs (usually several dozen or more), which they wrap in silk. If she gets enough food, a single female may produce several clutches of eggs in a year. They are seasonal breeders (sexual; oviparous). Female wolf spiders wrap their eggs in a round ball of silk, and keep them close. Wandering species carry their egg sack under their abdomen as they move around. Tunnel-building species keep their eggsacks in their tunnels, and bring them up to warm in the sun during the day (the warm temperature helps their eggs develop faster).

Parental investment: female parental care.
Male wolf spiders probably don't live more than a year, but females of some species can live for several years.

Behavior: many wolf spider species hunt at night, but some are active during the day. 
They are solitary animals, they hunt alone and only come together to mate.

Some species wander, hiding during the day and roaming at night to find food. Some patrol a regular territory, returning to the same place to rest. Others dig tunnels, or use tunnels made by other animals. A few build little walls or turrets around their tunnels, and then sit inside the wall looking out for passing prey or predators.

Key behaviors: diurnal; nocturnal; crepuscular; motile; nomadic; sedentary; solitary; territorial.
How do they communicate with each other?
Wold spiders use their vision more than most other spider groups. Males often signal to females by waving their pedipalps in certain patterns. Wolf spiders are also very sensitive to vibrations in the ground, and use scent and taste as well.

Wolf spiders eat insects and other invertebrates, and really large females might eat very small vertebrates, like amphibians and reptiles, if they find them. They sometimes attack insects that are larger than they are.

Different species of wolf spider have different ways of finding prey. Some build tunnels and ambush prey that come near their hiding place. Others wander on the ground, looking for small animals to eat. When they find a target, they jump on them and grab and quickly bite. Often they roll over onto their backs and hold the prey in a "basket" made by their legs before they bite.



photo via http://bit.ly/QeXC4r
Primary Diet: carnivore (eats terrestrial vertebrates, eats non-insect arthropods).
What eats them and how do they avoid being eaten?
Known predators: other spiders, wasps, ants, praying mantids, birds, small reptiles, toads and other amphibians, and shrews.
Wandering wolf spiders rely on speed and camouflage to escape predators. They have good vision and are very sensitive to vibrations in the ground that help them detect predators. Some species hide in tunnels in the ground. Wolf spiders will bite to defend themselves if necessary.

Wolf spiders can give you a painful bite if you handle them carelessly, but it the bite usually doesn't do much damage unless the person bitten is allergic to the venom.

Wolf spiders are often common in agricultural areas, and can be very helpful in reducing populations of insect pests.

No wolf spiders are known to be endangered. (Michigan University - BioKids)



Edited, Revised and Condensed by:  Scott Glaze    August 26, 2012

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3 comments:

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