Scorpions in Canada

1. Sun scorpions

Sun scorpions (Order Solifugae, in the Class Arachnida) are found in semi-arid and arid regions with dunes, eroded slopes, open sand or rocks. We have them in southern Alberta, usually in coulees and badlands, but often right in the cities of Lethbridge and Medicine Hat). They are also known from the southern Okanagan Valley of BC, and less commonly in southern Saskatchewan. Southern Canada is the northern range of these arachnids, so they are low in numbers relative to warmer regions to the south. Sun scorpions apparently increase activity and numbers during warm and dry years, and serve as indicators of warmer climate trends here in the north. They were observed relatively frequently during 1984-88, and 1999-2003. It is unknown why they increase during in warm periods, but more warm weather probably results in great survival of immatures, more rapid development, more favourable conditions for reproduction, and an abundance of prey (which typically include immature grasshoppers, and other small insects).

Our common sun scorpion species are in the genus Eremobates. They are only 1 to 2 cm in length, but are similar in appearance to the much larger species of the Middle East (see example photo further down this page).

Sun scorpions often seek dry crevices and cracks for cover, and to find prey (mainly insects). You might encounter them on a hike, or even in your basement. They are delicate and cautious in their movements, but they can move rapidly when warm. When distrubed, they will play dead briefly, resume investigation of their surroundings, and try to escape. If you see sun scorpions, don't kill them or handle them. If you are bitten (the small ones almost never bite, but if they are handled they might), use antiseptic and a bandaid. Our sun scorpions have less venom than a bee or wasp.

The sun scorpions are also referred to as wind scorpions or camel spiders (although they are not actually spiders, they are close relatives in the same Class, the arachnids). Sun scorpions are sometimes collectively called the Solpugidae, although the species of sun scorpions are arranged into a number of different families.

You can contact me if you want to donate specimens for study, or report sightings. There is no active research program here on sun scorpions, but observations on their biology, ecology and biodiversity are certainly worth recording, and your news would be much appreciated. There is no survey, but I keep track of general observations.

Sun scorpions found in Canada are small, and can be recognized by the lack of a tail and stinger (called a telson) and lack of claws. The narrowly spaced, beady eyes and pointed mouthparts are characteristic of sun scorpions. The head appears large relative to the body, giving it a "bulldozer" appearance.

 

A dead, dried specimen collected near Medicine Hat, Alberta.

The two large, needle-like jaws on the front of the head of a sun scorpion are called chelicerae, a feature that distinguishes them from the line of insects and their close relatives, which have mandibles instead of chelicerae. The chelicerae pierce the body of a captured prey item, and in a kind of rotating bicycle-pedal motion the chelicerae are moved in and out like daggers while the prey's internal body fluids are sucked into the gut of the sun scorpion. The dried remains of prey are discarded by sun scorpions. Sun scorpions do not consume the prey whole, as true scorpions often do.

Click here to see photos of a sun scorpion that was killed by black widow spider.

Sun scorpions have four pairs of legs, plus one pair of leg-like pedipalps, which are held out in front like antennae as they feel and smell the environment ahead of them. The presence of the palps explains why scorpions of all kinds appear to have ten legs, when they actually have only eight. True scorpions (below) also have pedipalps, but they are shaped like large claws.

In Alberta, I have seen sun scorpions in Lethbridge, Coaldale, Taber, Barnwell (these were found in a home), Medicine Hat, Milk River, Onefour and in a few other places. They were fairly common during 1984-88 and 1999-2003. Future warm, dry conditions will likely lead to higher abundance and more encounters.

Regarding "home invasions", sun scorpions (and also true scorpions) may move into a home if the weather stripping allows gaps at the bottoms of doors, or if openings around pipes and wires are not caulked. They are not dangerous, nor do they harm pests of plants or pets. To remove them, you can let them walk into a jar. Or, let them walk onto a piece of newspaper and set them outside, where they will eat grasshoppers and other insects (and spiders).

I would appreciate hearing about the presence of sun scorpions. They are indicators of climate, and part of the biodiversity in the grassland food web.

Address: Dan Johnson
Dept of Geography, Environmental Science
University of Lethbridge
4401 University Drive West
Lethbridge, AB, T1K 3M4, Canada
E-mail: dan.johnson@uleth.ca

The photo below from Iraq (recently circulated on the internet) illustrates the similar appearance of the much larger species of sun scorpions that are found in the Middle East. These might be of Galeodes arabs, a large desert species.

2. True scorpions

True scorpions (such as the northern scorpion, Paruroctonus boreus) have a telson (segment with a poison gland on the tail) with a stinger, and large claws (pincers) on the pedipalps. They consume prey by macerating and swallowing it, rather than simply suck the fluids.

True scorpions have four pairs of legs, one pair of palps with pincers, a tail, and telson (stinger segment).

At left: two views of a northern scorpion, shown here eating a house cricket. This one was collected in the Oldman River Valley, in the city of Lethbridge (collected by Dan and Julie Johnson, in July, 2001).

Johnson, D. 2004. Observations on the Northern Scorpion, Paruroctonus boreus, in southern Alberta, 1983-2003. Map and poster, 7th Prairie Conservation and Endan-gered Species Conference, Calgary, Feb 26-29, 2004.

Johnson, D.L. 2004. The Northern Scorpion, Paruroctonus boreus, in southern Alberta, 1983-2003. Arthropods of Canadian Grasslands 10: 14-15. Biological Survey of Canada, Ottawa. (PDF)

If you collect a scorpion for photographing or observation, try to release it in the same location where you found it. In captivity, they will consume immature grasshoppers, crickets, maggots and small caterpillars. Don't damage the tail or claws. These are not the dangerous scorpions of wild west movies.

Click here for on-line survey forms to report your observations of where you have seen true scorpions (requires Internet Explorer or Netscape 6+). If you prefer, I will supply survey forms on paper (with a paid stamp supplied by me), for your Canadian and Northern Great Plains sightings of sun scorpions or true scorpions (dan.johnson@uleth.ca).

More information on other scorpions: Kari McWest's Scorpion website. His page on this genus is here.

3. False scorpions

(Class Arachnida, Order Pseudoscorpionida)

False scorpions (usually refered to as pseudoscorpions) are very small arachnids, usually only about 2 to 4 mm in length.The body of a pseudoscorpion would not even be as big as the stinger of a true scorpion, even the stinger of a small species of true scorpion such as the northern scorpion shown above.

Like other arachnids, pseudoscorpions have four pairs of legs and a pair of pedipalps, which hold large claws (or pincers). The claws of pseudoscorpions are their most noticeable feature, and the claws and palps together might be longer than the rest of the body! They have no tail or stinger, and appear rounded at the posterior end. When disturbed they will briefly pull in all their appendages and look like a small seed.

Here are some drawings of the appearance of typical pseudoscorpions.

Pseudoscorpions are common in woodland, but relatively rare in grassland. They can be captured by allowing leaf litter and loose, moist soil to slowly dry in funnels. The arthropods (including small arachnids) will move down as the sample dries, and fall out the bottom.

The pincers on the palps have tiny hairs that allow them to feel their way, and also to assess prey item movement and even prey size. Years ago, I conducted experiments with pseudoscorpions preying on springtails (Collembola), which are tiny hexapods (six-legged relatives of insects) that live in soil and leaf litter. The pseudoscorpions hunt for springtails. When they approach one, they sense the size of a springtail before grabbing it in a pincer and proceeding to suck out the prey's body fluids with the chelicerae. Springtails that are very small are ignored by the pseudoscorpion predator, and large springtails are avoided. Springtails have numerous age and size classes that reproduce, so this size-selective predation can have consequences for population growth.

Johnson, D.L., and W.G. Wellington. 1980. Predation of Apochthonius minimus (Pseudoscorpionida: Chthoniidae) on Folsomia candida (Collembola: Isotomidae). Predation rate and size-selection. Researches on Population Ecology 22: 339-352

Johnson, D.L., and W.G. Wellington. 1980. Predation of Apochthonius minimus (Pseudoscorpionida: Chthoniidae) on Folsomia candida (Collembola: Isotomidae). Effects of predation on prey populations. Researches on Population Ecology 22: 353-365.