Arachnids (Class Arachnida) are arthropods with eight legs. This distinguishes them from insects with their six legs, a three-part body, and antennae. In some species, the front legs of adult arachnids are modified into claws or other appendages to feed, for defence, or to sense the world around them.

There are 325 species of spiders, two species of ticks, one species of harvestmen, and two species of pseudoscorpions confirmed present in the NWT. Four species of pseudoscorpions are expected to be present.

Spiders

Spiders (Order Araneae) form the seventh largest order of organisms on the planet (and the largest entirely predatory one) and are key components of all ecosystems where they occur.

Spiders, along with scorpions, harvestmen, mites, ticks, and other familiar and not-so-familiar organisms, belong to the Class Arachnida in the Phylum Arthropoda. Arachnid is a word derived from the Greek term for “spider-like”.

Spiders have fang-like mouthparts (called chelicerae) and most have four pairs of eyes. Unique among all animals, spiders possess abdominal spinnerets (from which they produce silk) and, in males, pedipalps (leg-like appendages at the front of a spider) that are extensively modified for mating purposes.

Spiders are excellent predators, primarily eating insects and other arthropods. Most are generalists, preying upon a wide variety of organisms. Only a few are specialists. Some actively hunt down their prey, others wait for prey to come to them and then capture them in elaborate webs or simply by ambushing and overpowering them.

All spiders use the silk they extrude from their spinnerets for various purposes, from safety lines and egg sacs to prey-capture webs. To most people, webs are probably the most familiar aspects of spiders. Many spiders, however, do not build webs. Spiders that ambush or actively hunt their prey (e.g., crab, jumping, wolf, ground, and sac spiders), do not build prey-capture webs. Among web-building spiders, species grouped within the same Family usually construct similar types of webs (e.g., funnel-webs for Agelenidae, orb webs for Araneidae and Tetragnathidae, sheet-webs for Linyphiidae and several other families, and cob webs for Theridiidae). Spider webs vary widely in size, shape, and the amount and type of silk used.

Most North American species take one to two years to complete their life cycles and, in the NWT, few live for more than one year. Almost all spiders are solitary animals. Because of this, spiders have evolved complex courtship rituals so that males and females of the same species can mate successfully… without eating each other.

Many Nearctic spiders spend the winter either as eggs (e.g., many orbweavers) or as sub-adults (e.g., many wolf and crab spiders). Sub-adult Pardosa wolf spiders are often one of the first signs of spring in the north, emerging from their winter hiding places and running about in open areas, often in large numbers, on the first reasonably warm days. They mature rapidly and mate in the first weeks of spring. Shortly thereafter the females can be found dragging egg cases behind them, attached to their spinnerets, or with young spiderlings riding on their backs. Although only a few types of spiders are known to care for their young, this type of maternal care is typical of wolf spiders.

Very little new information on NWT spiders has been produced since 2015. Only four species have been added to the checklist of the NWT spider fauna and the conservation rankings have remained essentially unchanged.

Fully 75% of spider species recorded in the NWT have an undetermined rank because of insufficient survey data. Many of these species, however, are widespread and common Nearctic species elsewhere in Canada and new data in the future will likely show that they are secure in NWT.

Large areas of the NWT are under-sampled for spiders, especially its vast regions of boreal forests and subarctic tundra. These and similar habitats in other parts of Canada continue to produce novel records of spider species, especially in Family Linyphiidae (sheetweb weavers and dwarf spiders – by far the most diverse spider Family in the northern Holarctic region). Thus, specialized collection techniques (especially pitfall and Berlese sampling, as well as supplementing classic morphology-based identification methods with molecular techniques) in just about any of NWT’s habitats should result in substantial further new additions to the NWT spider list as well as new geographical and quantitative data valuable for the ranking effort.

With adequate sampling the total number of spider species in NWT may range from 500 to 650 species, with about half of these being Linyphiidae. Of course, the only real way to find out is to get out there and look for spiders!

Ticks

Ticks (Order Ixodida) are parasitic arachnids. The adults are small (3 to 5 mm) and flat, and have modified mouth parts to feed on blood of their hosts, which can be mammals, birds, or reptiles and amphibians.

Ticks thrive in warm and humid habitats, so few species have managed to make a living in the NWT. We expect to see more species with our warming climate.

There are two major families of ticks, the hard ticks (Family Ixodidae) and the soft ticks (Family Argasidae). Only hard ticks are found in the NWT. The head and thorax (called cephalothorax) of adult fleas are fused to their abdomen. They look like a miniature round button with eight legs. Adults will enlarge after gorging with blood. They sport a hard shield (scutum) on their back and a beak for digging in skin and sucking blood.

The lifecycle of ticks includes the egg, larva, nymph, and adult. The species present in the NWT have one or two hosts. The winter tick specializes in feeding on moose, but some also have been found on boreal caribou. Eggs fall off a host on vegetation in early spring and hatching into larvae may be dormant for a while. But when conditions are good, in late summer or fall, the larvae group up the vegetation from where they get on a passing host, where within a couple of weeks, they transform into a nymph.

Then they will wait on the host and diapause to an adult in the middle of winter. Their blood sucking habit can cause major discomfort for a moose, who will scratch off fur and open wounds on its skin.

The snowshoe hare tick is well known to trappers in the NWT. This species completes its entire life cycle on ground or low vegetation and on a hare but may also take on another host species when hares are few.

Harvestmen

Harvestmen (Order Opiliones) are not spiders. In harvestmen, the space between the cephalothorax and abdomen is broad, and the body appears as one solid oval. Also, unlike spiders, the Opiliones have no venom. Their extremely long legs (eight of them of course) gave them the nickname “daddy-long-legs”, and they are also called harvesters. They are omnivorous and found worldwide but prefer warmer climates. The only species found in the NWT, the common harvestman, has been introduced, and is now ubiquitous near our homes.

Pseudoscorpions

These predacious arachnids are similar to true scorpions but are without a stinging tail and are much smaller (less than 5 mm). They are reddish-brown, light tan, or black. They have four pairs of walking legs and two crab- or lobster-like pincers. They do look like miniature crabs. Our pseudoscorpions are entirely harmless and actually beneficial.

Pseudoscorpions are one of the most peculiar, complex but still lesser-known groups of animals. Eggs and immature stages are carried by the females, so they look after their young up to a point. If food is scarce females may sacrifice themselves to feed the young. Some species have elaborate courtship dances. In some places males have not been found suggesting that the population is made entirely of females that reproduce without fertilization. Most species are found on the ground in moist litter and under rocks.

They feed on small invertebrates such as mites, lice, springtails, and insect larvae. Most of our pseudoscorpions may live a solitary life but in the tropics some species are social, forming colonies, and they hunt relatively large prey cooperatively. Others feed on parasites of other organisms.

Many species spin silk to make cocoons for protection. There is a venom gland in the pincer used to immobilize prey. This is far too small to be of any risk to people. Some of the digestion is external. A milky corrosive fluid is exuded over the prey and the liquefied mass is then consumed.

Some species of pseudoscorpions often use other animals for transport (called phoresy). We see pseudoscorpions attached to flies, bees, and beetles. By achieving transport to a new location, they obtain a new, possibly more valuable habitat, and they avoid inbreeding.

Pseudoscorpions are among the unique species that survive in some of earth’s deep caves in a dark, primordial and lethal cocktail of toxic compounds including depressed oxygen, increased carbon dioxide as well as sulphide, methane, and ammonia. An understanding of how they deal with this extreme environment may be useful to humans.

Although we do know some very interesting things, what we do not know is also notable. We have very little information on the distribution and ecology of pseudoscorpions in the northern part of North America. The fact that they are not easily identified to species makes their study more difficult. Microscopic examination of specimens and careful dissection and preparation may be necessary to reveal distinctive features.

Most of the 3,000 species of pseudoscorpions live in the tropics. There are approximately 30 species in Canada, and one reaches the northwestern unglaciated Arctic, also known as eastern Beringia. The Arctic pseudoscorpion is also found in Siberia (western Beringia). It was first discovered in Tibet. In Canada, it is confined to Yukon and the NWT, where it has only been found in the Richardson Mountains near the Yukon border. It may occur southward in the NWT in the Mackenzie Mountains and east of the Mackenzie Delta.

Arctic pseudoscorpions are believed to be relicts of the ice age. At that time most of the northern parts of North America were under mile deep ice, which lasted for many thousands of years. There was a huge area of ice-free landscape in the northwest of North America. Here woolly mammoths, saiga antelopes, horses, steppe bison, dire wolves, and 3 kinds of lions, among other species, shared the landscape with the pseudoscorpions. Although many of the large mammals are extinct, and much of the landscape has changed over the last 10,000 years, many small species that lived with the past megafauna are still present in the area to this day.

Different species of pseudoscorpions have different habitats. The house pseudoscorpion, only 4 mm long, occurs in buildings where it is said to feed on tiny organisms such as dust mites, clothes moths, carpet beetle larvae, bed bugs, and book lice. The house pseudoscorpion is mostly seen in the damper parts of homes with deteriorating paper, books, and mould in basements and washrooms where the prey is more common. This beneficial pseudoscorpion has been reported in Yellowknife.

Other species may be found in NWT in forest litter, bog moss, soil up to 30 cm deep, and in caves. Some found on open rocky hills in Yellowknife have yet to be identified. Any information on occurrence of these fascinating animals is of interest.