Drassodes

Physical description and identification

Drassodes is a large genus of ground spiders in the family Gnaphosidae, erected by the Swedish naturalist Niclas Westring in 1851. More than 150 species are accepted, making it one of the biggest and most widely distributed genera in the family. It has no bright colours and no pattern, so identification rests on shape, texture and the spinnerets rather than markings.

A typical Drassodes is a heavy, slightly flattened spider, uniformly straw, sandy, fawn or coppery reddish brown, densely clothed in short fine hair that gives it a matt, dusty finish. The legs are stout and hairy and the chelicerae large and forward-projecting — a build that matches its habit of overpowering prey directly.

Adults

• Size: most species fall between 5 and 18 mm in body length. The largest European species, D. cupreus and D. lapidosus, reach 15–18 mm in the female and 9–13 mm in the male; small species such as D. pubescens are only 4–7 mm. Claims that the genus reaches 2 cm describe an extreme rather than anything you are likely to find.
• Colour: plain and cryptic. Pale straw to mid brown, often with a faint coppery or greyish sheen on the abdomen and a darker carapace. Some species show a vague darker median band, but nothing like the bold stripe of the parson spiders.
• Eyes: eight eyes in two rows of four. The rear-row median eyes are flattened and oval or angular instead of round, and reflect torchlight with a silvery gleam. That is the family character, and our guide to spider eyes explains how to use it.
• Distinctive features: the front spinnerets are long, cylindrical and clearly separated, projecting past the tip of the abdomen — conspicuous enough in a large Drassodes to see with a hand lens. Mature males are slimmer with swollen pedipalp tips. Species need a microscope and adult genitalia.

Eggs and egg sac

The female builds a white, thick-walled, lens-shaped egg sac and fastens it to the roof of her silk cell, usually on the underside of the stone she lives beneath, then stays with it and defends it. That is why lifting a stone in early summer so often exposes a large female sitting squarely on a white disc of silk.

Spiderlings

Spiderlings emerge pale and translucent, already the same shape as the adults. They pass their first moult inside the sac, then leave the maternal cell and build small silk retreats of their own nearby. Juveniles are the overwintering stage in temperate regions and resume growth in spring, each moult inside a freshly spun cell.

The silk cell instead of a web

No Drassodes spins a snare. What it builds is a retreat: a tough, closed, purse-shaped cell of dense white silk, usually pressed against the underside of a stone or fitted into a crevice under bark. The spider rests, moults, mates and guards its eggs there. Silk is also used offensively: the broad front spinnerets of Gnaphosidae flick sticky piriform threads over prey, gumming the legs of ants and rival spiders before the bite goes in — as effective as a web, but delivered at arm's length.

Where Drassodes spiders live

Drassodes is close to worldwide in the northern temperate zone and reaches well beyond it. The centre of diversity is the Palearctic — Europe, North Africa, the Middle East, Central Asia, the Himalaya, China, Korea and Japan — with many species in sub-Saharan Africa and Madagascar, several in the Indian subcontinent, and a smaller set in North America. It is therefore not a strictly Holarctic genus, as it is sometimes described: D. dregei and D. kibonotensis in Africa and D. malagassicus in Madagascar all sit well outside the Holarctic. In practice the genus turns up in Britain, across continental Europe, in India and South Africa, and at lower diversity in the western United States.

The habitat is consistent across that range: warm, dry, open ground with loose cover on it. Grassland, heath, chalk downs, coastal dunes, scree, quarries, field margins, dry stone walls and gardens all suit the genus, and the spiders spend the day under flat stones, boards, bark and logs. A few shelter in sheds and outbuildings, but Drassodes is far less of a house spider than Scotophaeus or Herpyllus.

Are Drassodes spiders venomous?

Yes, in the ordinary sense that applies to nearly every spider: they carry venom glands and use venom to kill the invertebrates they catch. That venom is not medically significant. No antivenom exists for any species in the genus, none is needed, and there is no credible record of necrosis, systemic poisoning or death caused by one. The genus is unrelated to the recluse spiders and to the widows, and lacks both of the venom components that make those groups dangerous. The real difference from a smaller spider is mechanical: a big D. cupreus or D. lapidosus has powerful chelicerae, so if it bites you feel the fangs rather than the venom.

Can Drassodes spiders bite?

They can, and a large female is one of the few ground spiders able to pierce human skin without difficulty. In practice bites are uncommon: these spiders live under stones in open countryside rather than in bedrooms, and their reflex when uncovered is to run for the nearest crack. The bites that do happen involve a spider picked up bare-handed, trapped in a glove or boot, or gripped while guarding an egg sac.

The result is a sharp, immediately painful nip with a small red mark and localised swelling, sometimes with an ache in the surrounding tissue for a few hours. It typically settles within a day and leaves no lasting mark. Wash the site, apply a cold pack and use a simple painkiller if needed. Seek medical advice if swelling spreads well past the bite, if the wound becomes hot and increasingly sore after a couple of days, which suggests infection rather than venom, or if hives, wheezing or dizziness appear. Never apply heat, cut the wound or attempt suction.

Ecological importance and behavior of Drassodes spiders

Drassodes species are nocturnal hunters that sit high in the invertebrate food web of open ground. After dark the spider leaves its cell and quarters the surface, picking up prey through the sensory hairs on its legs rather than by sight, then closing with a short rush. Its size and strong jaws let it take prey most spiders of comparable size cannot handle: beetles, crickets and grasshopper nymphs, caterpillars, woodlice, ants, harvestmen and a great many other spiders, including wolf spiders of its own size class.

Natural predators: ground-feeding birds, shrews, lizards, toads and centipedes take them, and spider-hunting wasps of the family Pompilidae specialise in exactly this kind of large, web-less, stone-dwelling spider, paralysing an adult and sealing it in a burrow with an egg.

Prey-predator dynamics: as both a heavy predator of other spiders and prey for larger vertebrates, Drassodes links the small arthropod layer to the vertebrate one. In dry grassland, heath and arable margins it is among the dominant nocturnal predators and is regularly recorded in agricultural surveys as a natural enemy of ground-active pests.

Seasonal behaviour: in temperate regions adults are found mainly from late spring to late summer, with mating in early summer and egg sacs from about May onwards. A distinctive habit is pre-mating cohabitation: the male finds a subadult female, moves into her cell and waits, sometimes for weeks, until she moults into maturity. Juveniles overwinter under stones and in litter, and a typical life span is one to two years rather than the several occasionally claimed.

Relationship with humans: harmless and useful. Drassodes is a garden ally that eats ground pests and asks for nothing but undisturbed stones. No control is ever warranted.

Species in the genus and similar spiders

Quick facts

Did you know?

• The genus was described in 1851 by Niclas Westring, a Swedish naturalist who named a great many of the northern European spiders still recognised today.
• The name comes from Greek roots meaning "to grasp" or "to seize", which suits a spider that catches everything it eats with its own legs and jaws.
• Males practise a form of mate-guarding rare among hunting spiders: a mature male moves into a subadult female's silk cell and shares it for days or weeks, waiting for her final moult so that he can mate first.
• Ground spiders spray sticky silk as a weapon. The broad front spinnerets deliver piriform threads that pin an ant's legs down, which is how a soft-bodied spider safely eats one of the best-defended insects in the litter.

In summary, Drassodes is a big, plain, powerful and enormously widespread genus of night-hunting ground spiders that trade webs for speed, strong jaws and a silk cell under a stone. They are harmless to people, valuable in gardens and farmland, and the easiest of all ground spiders to find: lift a stone, look, and put it back exactly as it was.