Spiders live among us in almost every conceivable habitat. Their ecological role, one that benefits us, is as the ultimate predators of insects. They pursue this role with instinctive dedication; some have even moved into the warm micro-climates of people’s homes, unwittingly protecting us from pesky insects. In turn, they are a food source for many animals, forming an important link in the food chain.
Evolution has equipped spiders with a myriad of techniques for capturing insect prey: jumping spiders leap, crab spiders ambush, wolf spiders give chase and web-weaving spiders entrap. The earliest spider fossils date back 300 million years, and the creatures probably developed at least 100 million years before that, during the Devonian period. No other group of animals has been hunting insects so efficiently for so long.
Although feared by many, Ontario spiders are generally not dangerous and hardly ever bite humans. Most spiders use venom, delivered from an opening in their chelicerae (jaws), to subdue and predigest prey. In Ontario, however, only the rare and shy northern widow spider (Lactrodectus variolus) is considered dangerous to people. Even from this species, a bite is very unlikely to be fatal.
Both insects and spiders are arthropods (invertebrates with jointed legs). Insects form one class of arthropods, while spiders are an order – a level that is subordinate to a class – of arachnids. Other arachnids include harvestmen (daddy-long-legs), scorpions, ticks and mites. Spiders differ from insects in having eight rather than six legs, simple rather than compound eyes, two main body parts (abdomen and cephalothorax – a fused head and thorax) instead of three, no antennae and, of course, no wings.
In Ontario, the best time for observing spiders is from late spring to early fall. Early morning dew or frost reveals webs that are nearly invisible at other times. Some adult spiders do not live past the fall season, while others overwinter under bark, in leaf litter or in other shelters. Yet some spiders can be observed year-round. Yellow sac spiders (Cheiracanthium mildei), longbodied cellar spiders (Pholcus phalangioides) and others share our homes, egg cases can be found on buildings and vegetation, and thinlegged wolf spiders (Pardosa spp.) may take advantage of a sunny, mild winter day to catch some rays on a stump or log.
Researchers have discovered astonishingly high densities of spiders in certain habitats. For example, a British researcher once estimated a total of about 5.5 million spiders in a productive hectare of meadow.
These myriad of spiders are quite diverse. Closer to home, more than 800 species, representing 35 families, have been found in our province, and these numbers continue to grow as new spiders are reported.
Spiders can be daunting to identify. The colour of a species is often quite variable even when mature, while immature spiders are often very different than adults. Males and females of the same species may be similar or quite different in coloration and size. Males are slightly or much smaller than females. The pedipalps of the males resemble boxing gloves (for transferring sperm).
Learning family characteristics helps greatly. Among web-weavers, the type or location of web often distinguishes the family. Families can also be identified by the arrangement of the spider’s eyes. Some species are so distinctly marked that identification in the field is easy.
The following guide, of course, is not comprehensive. Instead, an effort has been made to choose species and families to represent the following: first, commonly observed spiders; second, distinctive and dramatic species; and third, examples of some unusual families that make our arachnofauna so diverse and interesting.
Note: Sizes listed refer to body length (excluding legs).
Orb weavers are nature’s poster spiders. Their spiralling orbs with strong support lines make a highly effective insect snare. From start to finish a web, which can contain up to 20 metres of silk and 1,000 to 1,500 connections, may be created in a mere 30 minutes. Remarkably, an orb weaver spider can weigh more than 1,000 times the weight of the web on which it lives. Orb weavers will eat and remake webs every few days – or sometimes daily – recycling 90 percent of the silk used for the original web.
Orb weavers rotate trapped insects with their forelegs while their hind legs pull out silk from the spinnerets to wrap the victim. Despite possessing eight eyes – arranged in two rows of four – an orb weaver’s vision is poor, rendering it dependent on sensing vibrations from its web.
Yellow garden spider
Banded garden spider
Conical trashline orbweaver
This family constructs orb webs, but these are usually angled greatly from vertical and may even be nearly horizontal. There is an open hub in the web’s middle where the spider can easily pass from one side to the other. Tetragnathids are long, slender spiders with prominent chelicerae (jaws) that are two-thirds the length of – or longer than – the cephalothorax. These spiders hide in grass, extending their long first, second and fourth pairs of legs lengthwise while clinging to blades of grass with their much shorter third pair of legs. Their webs are small- to medium-sized orbs with few radiating supports and are usually suspended at an angle between branches of shrubs. The small eyes are arranged in two rows. These spiders can be very difficult to identify to the species level. The orchard spider is an exception to this, but identifying others to the genus level in the field is sometimes best (e.g. Tetragnatha sp).
Silver long-jawed orbweaver
This family’s tangled, messy but effective webs fill spaces such as corners on a building, within tree crevices, hollows or among vegetation. Their abdomen is very large and globular, and they have very long legs. A comb of curved bristles (setae) on their back pair of legs is used to throw silk strands over insect prey that has become entangled in the web. Once the prey is subdued, the cobweb weaver injects venom, drags it further into the web and sucks the juices from its prey. The eyes are arranged in a fairly tight group, making a rather narrow horizontal oval.
Common house spider
Northern black widow
Candy stripe cobweb weaver
In Ontario, one species of this family is highly adapted to living in human habitation (therefore the name “cellar spider.”) A spider with the description below, living among a messy web, is unmistakable. Tolerance of these spiders in less-used areas of the house, like the cellar, will allow for many observation opportunities, including their rapid defensive gyrations which defend them from their main predators, which are wasps. In the southwestern United States, species in this family also inhabit caves and dark crevices.
Longbodied cellar spider
Many of these spiders are so tiny that identifying them by web type is most effective. The webs of these sheet-web weavers consist of a flat or curved sheet-like web below “knockdown” strands of silk that entangle tiny prey. The weaver clings to the bottom of the sheet or hides at the edge, ready to rush out and bite its victim from below and drag it through the web. Dewy sheet-web weaver webs decorating low plants and shrubs almost magically transform a meadow or shrubby area in the early morning light. This group is the most accomplished in “ballooning,” extruding silken threads to carry themselves on the wind to new locations. Ballooning spiders have been collected thousands of metres above the ground, and hundreds of kilometres out at sea. A subfamily of this group (the dwarf spiders) either build very small webs or none at all, but are also accomplished ballooners.
Bowl and doily weaver
Splendid dwarf spider
This family of spiders typically constructs a flat, sheet-like web with an attached funnel-like hideout. The web is often supported by grass or small tree branches, or may be constructed inside a shelter such as a tree trunk crevice or between rocks. These spiders conceal themselves in the narrow end of the funnel and wait for insects to stumble onto the web. When the spider senses a vibration, it charges out and subdues its victim with a paralyzing bite. Most have long spinnerets that extend beyond the posterior abdomen. Most members of this family have four eyes arranged in a middle row with two widely spaced eyes below this line and two narrowly spaced above.
Barn funnel weaver
This family of small spiders (less than 5 millimetres) may be most easily recognized by their distinctive web, although not all members of this family produce webs. The web often covers the tip of a small branch or plant head, or covers a leaf or is enclosed within one. Rather than sticky silk, these spiders use a cribellum, a sieve-like body part near the spinnerets to produce fuzzy silk to entangle prey. This is termed “hackled” silk. Although tiny, they are compact and heavy-bodied.
Most species in this family build webs with cribellate silk among leaf litter or under rocks or decaying logs. The webs are similar to funnel webs except for the fuzzy hackled silk which may appear messy.
Wolf spiders are primarily nocturnal hunters. Depending heavily on camouflage for protection, wolf spiders tend to be cryptically coloured (often grey or brown) to blend into their surroundings at night. Four eyes are arranged in a line beneath two very large eyes, and two more are mounted above and to the side of these. The two very large eyes distinguish them from the somewhat similar nursery web spiders, whose eyes are all relatively similar in size. Wolf spiders have excellent vision, as well as a keen sense of touch. These spiders are ground dwellers that chase their prey rather than use web snares or traps. Uniquely, females in this family carry their egg sac on their spinnerets, rather than in their jaws as with nursery web weavers. After hatching, the tiny spiderlings – that may number up to 100 or so – ride on the mother’s abdomen.
Thin-legged wolf spiders
Even arachnophobic humans may be attracted to these eccentric spiders. Any sort of stimulus, like putting a finger near to a jumping spider, will likely elicit its jerky motion and namesake jump, to a nearby object or sometimes right onto the curious person. Two enormous owl-like eyes dominate the face of this family, whose members rotate their cephalothorax to peer at nearby objects. They have binocular and colour vision, and can adjust their eyes’ focus by changing the shape of the retina. This results in extremely accurate judgement of distance, and an accurate pounce on unlucky prey. A silken dragline is set down in case of a miss. Jumping spiders also use silk to weave retreats in which they moult, rest and hibernate. With over 5,000 species described world-wide, Salticidae is the most diverse spider family, comprising approximately 13 percent of all species.
Tan or familiar jumper
With its long legs and large grey brown body, the nursery web spider somewhat resembles a wolf spider in appearance. The best way to distinguish them is by examining their eye arrangement. Wolf spiders have a very large pair of eyes above a smaller row of four eyes, while nursery web spiders have two slightly curved rows of four eyes that are fairly equal in size. These spiders, which have good vision, will run after their prey over land, skate across water surfaces chasing aquatic insects and some even dive underwater in pursuit of a meal. Females of this family use their fangs and pedipalps to carry their egg sacs.
Brownish-grey fishing spider
Striped fishing spider
Six-spotted fishing spider
Nursery web spider
This family is nocturnal, spinning a silken cocoon-like structure to hide during the day and emerging to wander at night, mostly on or near the ground but very often in people’s houses. Recently, the subfamily Eutichuridae, formerly included in Miturgidae and which includes the Yellow and Agrarian Sac Spiders below, has been considered a separate family.
Yellow sac spider
Ground spiders never construct a prey-catching web; instead they run down insects on the surface. Mostly nocturnal, they spend the day in a silken retreat. They are often found in leaf litter, or under rocks or logs. Their spinnerets are like tiny cylinders, somewhat widely spaced and often extending beyond the abdomen (visible from above).
These spiders are small-to-medium-sized and often light-coloured. This family is named for the silken “sac” that they make each morning in a rolled or folded leaf or under wood (often bark) or stone. Sac spiders hide in their shelter by day, emerging at night to hunt insect prey on the ground or among foliage. They are similar to ground spiders, but their spinnerets are smaller and not as obvious from above.
Leaf curling sac spider
Many species of this family are convincing ant-mimics in both appearance and behaviour. They presumably gain protection by associating with ants, which are avoided by many predators. This family of spiders catches prey by pursuing it on the ground.
Originally grouped with crab spiders, this is now considered a separate family. They tend to be medium-sized and light-coloured (light brown or grey). Many of these species hold their legs crab-like (out to the side) when at rest. They are active hunters.
Slender crab spider
Like their namesake, crab spiders extend their legs to the sides. The first pair of legs often has sharp spines to capture and hold prey, while the second pair of legs is longer than the other pairs. Crab spiders may climb in and around plants or on the ground in search of prey, or wait patiently on flowers, using camouflage to ambush unsuspecting insects.
Goldenrod crab spider
Ground crab spider
- Protect natural habitat, and create some of your own. A profusion of flowers in a small meadow or a small section of garden or lawn will attract many spiders.
- Provide a variety of natural habitats including shrubs, meadow, forest and ponds.
- If you find a spider inside your home, putting it outside in cold weather will probably kill it. It’s better to put it in an attic or basement, or even to let it wander where it likes.
- Avoid using pesticides.
- Common Spiders of North America, by Richard A. Bradley
- Spiders and Their Kin (A Golden Guide) by Herbert and Lorna Levi
- Spiders of the North Woods by Larry Weber
- Biodiversity sheets: uoguelph.ca/arboretum/educationandevents/arboretumbooks
- Design: Noah Cole
- Editing and proofreading: Jaklynn Nimec, Ron Corkum
- Photography: John Reaume, Camille Tremblay Beaulieu, David Coulson, Eric Eaton, Brett Forsyth, Noah Cole
- Expertise: Tom Mason, Gergin Blagoev
Written by Dan Schneider