www.wolfspiders.org is created by Ph.d. Anders Nielsen. Drawings are © www.wolfspiders.org.
By Anders Nielsen, Ph.d.
The Greek name for wolf is Lycos, and wolf spiders (Lycosidae spp.) are named as such because they were previously thought to hunt in groups, in contrast to spiders catching their prey in webs. Wolf spiders are also characterized by good vision, females carrying their egg sacs with them (most do), and eight eyes.
Wolf spiders are diurnal and have fairly large and robust front legs. They use their strong cheliceraes to crush prey, and they can inflict sharp stinging bites on humans.
They are very fast and can reach a speed of two feet per second over short distances1.
Wolf spiders have a brown or dark coloration with bristles on their legs and body, which makes some species look a bit like tarantulas, but they are in fact very different. As there are many different wolf spider species, their appearances vary a lot. Consult the picture section and see also the latest photo submitted to this site (by Robert McDonald).
Wolf spiders can reach a size of up to 1.2 inches. That is the body size only - if the legs are included the total length of a Wolf Spider can be almost four inches. Wolf spiders are rarely found in groups and they prefer to hunt alone. Some are ambushers that lie in wait for a prey to pass by or exit from a burrow. Others chases their prey over relatively short distances.
Wolf spiders depend on their sight and have eight eyes in total, and of these are two very large. Above them, and laterally, they have two smaller eyes - and below the two large eyes, in a middle row, a row of four relatively small eyes is seen.
Although they have a good vision, they cannot discriminate between e.g. a finger and an insect; erroneously, this has lead to the wrong conclusion that Wolf spiders are naturally aggressive which they are not2.
However, the most pronounced feature of Wolf spiders is that females carry their egg sacs and spiderlings with them. The sac is attached to the spinnerets at the end of the abdomen and the female Wolf Spider keeps her abdomen in a position that prevents the eggs from being damaged. The egg sacs are white and occasionally even blueish. When the spiderlings are ready to hatch, she opens the egg sacs with her jaws. However, a few species (Arctosa, Trochosa and Alopecosa) hides their eggs underground and do not carry them with them.
The spiderlings attach themselves to the top of the females abdomen, and until their first change of skin they will stay with their mother. She will hunt with the spiders attached to her and provide her offspring with the necessary protection.
A unique feature of the wolf spiders is that their eyes reflect light well, so if you bring a flash light with you into Wolf spider territory, you will probably see some spider eyes.
For some people wolf spiders are a common pest in their homes, and it is true that in the fall they look for warm places to sleep through the winter. Wolf spiders are found on the ground in almost any terrestrial habitat. They of course prefer places were prey can be found such as around doors, near plants, windows, humid basements, and garages. Away from suburban gardens, they can be found in nearly all habitats. Wolf spiders disperse aerially and they are quite mobile too, so they are found almost everywhere.
The 125 species of Wolf spiders in the USA can be found all across the country and wolf spiders are one of the most abundant spiders in the US. They are extremely common in California and some even call them California Wolf spiders. In Texas they have the Texas Rabid Wolf spider which is one of the biggest spiders of Texas.
Wolf spiders eat insects. Crickets are among their favorites but they also eat fly-grubs, cockroaches, mealworms and beetles. In addition, there is some evidence of cannibalism.
The male wolf spider is smaller than the female, so to avoid any trouble the male approaches the female with caution. and weaves his front legs to identify himself and make his intentions clear. If lucky he is not eaten and it must be noted that not all wolf spiders are cannibalistic.
According to a study by Lomborg & Toft (2009)4 the courtship behavior includes encircling, jumping around and vibrating with both palps and the abdomen. The mating itself takes place with the male facing the female hind part while penetrating her genital opening with a palp containing his semen. The female can carry the male him during mating because he is much smaller than her.
Wolf spiders are in principle venomous and their venom is poisonous. Bites that penetrates the skin can cause pain, swelling and itchiness. Some people only experience the symptoms for a few minutes, while others get a wound that takes a few days to heal.
Until around 1990 wolf spider bites were treated with antivenom but that stopped when a study showed it was unnecessary. That is also why it is a little bit confusing to answer if this spider is venomous, or poisonous, because it really is. It is just not venomous enough to inflict serious damage to people due to its venom.
The bite may in itself be infectious if proper actions are not taken. A survey showed (Isbister & Framenau, 2004)3 that the median duration of acute pain from wolf spider bites were 10 minutes. Even so, Wolf spider bites should be avoided.
If you are bitten by a wolf spider the chances are that it is a rather large specimen, as smaller specimens do not have the power to penetrate skin. If the bite has penetrated your skin, and it is a wolf spider, you will probably experience a swelling around the site of the bite. Pain from bites are caused by mechanical trauma, not venom, as it is weak.
Necrotic arachnidism is usually attributed to wolf spider bites (Isbister ' Framenau, 2004)3. In a study they showed that approx. 24 % of all wolf spider bites could be considered severe, but that wolf spider bites did not cause necrosis (death of tissue), and that the pain associated with wolf spider bites is mainly due to mechanical trauma. In the same study they also found that the median duration of pain is 10 minutes only.
A study in Toxicon also showed (Ribeiro et al., 1990)6 that "No local necrosis, a severe complication described in the previous literature, was detected, suggesting that those old cases were due to misdiagnosed Loxosceles (brown recluse spider) spider bites".
Another study (Campbell et al., 1987)2 reported that bites from North American wolf spiders are generally mild, and that any mild cause of skin necrosis is due to the bite itself, and not the venom.
Recent research has shown that male wolf Spiders cannibalize on older female wolf spiders5. The study shows that male wolf Spiders occasionally preyed or mated bypassing female wolf Spiders, and that older female wolf Spiders had a larger chance of being eaten than young female wolf spiders. The research team hypothesize that this behavior improves the reproductive success of males, as they eat females with a lower reproductive value and mate with females with a higher reproductive success.
According to entomologists, wolf spiders are migrating indoors in greater numbers than ever seen before. The reason is believed to be the high temperature that has plagued the country for the past few weeks. Seal cracks and shut doors and windows if you want to keep them out - or make sure that your home is not a suitable for the insects that wolf spiders feed on.
1. Ed. Tavolacci, J. Insects and Spiders of the World 10 (2003)
2. Campbell, D.S., Rees, R.S & King, L.E. Wolf Spider Bites. Cutis 39(2) pp. 113-114 (1987)
3. Isbister, G.K. & Framenau, V.W. Australian Wolf Spider Bites (Lycosidae): Clinical Effects and Influence of Species on Bite Circumstances. Journal of Toxicology Clinical Toxicology 42(2) pp. 153-161 (2004)
4. Lomborg, J.P & Toft, S. Nutritional enrichment increases courtship intensity and improves mating success in male spiders. Behavioral Ecology 20(4) pp 700-708 (2009)
5. Aisenberg, A., Costa, F., Macarena, G. Male sexual cannibalism in a sand-dwelling wolf spider with sex role reversal Biological Journal of the Linnean Society (2011)
6. Ribeiro, LA, Jorge, MT, Piesco, RV, et al. Wolf spider bites in Sao-Paulo, Brazil - A Clinical and Epidemiologic-study of 515 Cases. Toxicon 28(6) pp. 715-717 (1990)
I wish to thank Don, Lisa, Gerardine and João for giving me the permission to use their photos.
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