Green Crab (Misumessus oblongus)

Physical description and identification

Misumessus oblongus is a small, delicate member of the family Thomisidae, the crab spiders. It has the family build — flattened body, short rear legs, long heavy front pairs held permanently open — but in a narrower form than the broad, rounded flower spiders it is usually confused with, and it walks sideways and backwards as easily as forwards.

Adults

• Size: females measure roughly 3–7 mm in body length (0.12–0.27 in), and males are about half that. Even a large female is smaller than a grain of rice.
• Colour: a clear light to emerald green over the whole body, faintly translucent, with a paler underside. Many individuals carry a thin red band along each side of the abdomen and some have none — the bands are variable.
• Shape: the abdomen is slender and pointed toward the rear, giving the kite or diamond outline that separates this species at a glance from the round-bodied goldenrod crab spider.
• Eyes: eight small, dark eyes in two curved rows on a low, wide head, the side pairs set on small bumps. None is enlarged, which rules out the jumping spiders immediately.
• Colour change: none. Unlike Misumena and Misumenoides, which repaint themselves between white and yellow over days, this species stays green, which ties it to foliage and stems rather than pale blooms.

Eggs and egg sac

The female spins a tough, flattened silk sac among leaves, folding and binding the surrounding foliage into a shelter around it. She guards it for the rest of her life, which usually means she dies before the young emerge. The species passes the cold months in the sac or as very small juveniles, with spiderlings active again in spring.

Spiderlings

Hatchlings are pale, almost colourless miniatures that green up over their first moults. They disperse on silk lines or by ballooning, take thrips and aphids on low vegetation, and mature over the following spring and summer. Total lifespan is about a year.

Hunting instead of a web

The green crab spider builds no capture web — no orb, no sheet, no tangle; see our guide to spider webs for how the web-building families differ. Both sexes still spin silk: females for the egg sac and safety drag-lines, and males of many crab spiders drape a fine bridal veil of silk over the much larger female during courtship — the grain of truth behind the claim that a male covers a mate twice his size in silk.

Prey is caught by ambush. The spider settles on a leaf edge, stem or flower head and holds the long front legs apart, sometimes for hours without moving. When a small insect lands within reach the legs close, the fangs go in behind the head, and the venom stops the prey before it can pull free.

Where the green crab spider lives

Misumessus oblongus is a North American species with a far wider range than it is usually credited with. It occurs across the eastern and central United States, west to the Great Plains and beyond, north into southern Canada, and south through Florida and the Gulf states into Mexico. Lists that confine it to Alabama, Florida, Georgia, Louisiana, Mississippi and South Carolina describe a handful of well-surveyed states, not the species’ actual limits.

The habitat is outdoor vegetation in the open: meadows, old fields, tall grass, hedgerows, woodland edges, shrubs, garden borders and crop margins. Because the spider is green rather than white or yellow, it sits on leaves, stems and seed heads at least as often as on flowers. It is not a house spider and does not live in garages — indoor records are almost always spiders carried in on cut foliage.

Are green crab spiders venomous?

Yes, in the ordinary sense that nearly all spiders are. The green crab spider injects venom to subdue the insects it catches, and it relies on that venom completely: with no web to hold prey and a body of only a few millimetres, it has to shut down a struggling fly or bee almost instantly.

The venom is adapted to insects and is not medically significant to people or pets. The species is unrelated to the recluse spiders and the widow spiders, and carries neither the tissue-damaging enzymes of the first group nor the neurotoxins of the second. Its fangs are also far too short to be a realistic threat to human skin.

Can green crab spiders bite?

In principle yes, in practice almost never. The spider is a few millimetres long, its instinct on being disturbed is to freeze and then drop off the plant on a silk line, and it has no defensive display at all. A bite would require the spider to be pressed against skin — typically inside a picked flower or a handful of cut foliage.

Where one has been reported the effect is a momentary pinch with at most a small red mark, gone within an hour or two. No swelling beyond the spot, no systemic symptoms and no tissue damage have been documented for this species. Wash the area with soap and water; a cold pack is enough if it feels sore. Spreading swelling, hives or difficulty breathing would indicate an allergic reaction rather than the venom and should be assessed medically, as after any insect sting.

Ecological importance and behavior of the green crab spider

This is a patient sit-and-wait predator that hunts entirely by stillness and colour. Because it matches green tissue rather than petals, it holds a productive leaf or stem for days and takes insects moving through foliage as well as those arriving at flowers.

Diet: small flower and foliage insects — hoverflies and other small flies, small bees, parasitic wasps, leafhoppers, aphids, thrips, small moths and beetles. It does not eat centipedes or millipedes, which live in soil and litter well away from the spider’s hunting ground, and any spiders it takes are tiny ones that blunder within reach.

Natural predators: insectivorous birds, lizards, ants, assassin bugs, mantises and larger spiders, together with spider-hunting and mud-dauber wasps that paralyse crab spiders to stock their nest cells. Camouflage and absolute stillness are the only defences it has.

Prey-predator dynamics: the species is both hunter and hunted. On crops and garden plants it removes leafhoppers, aphids and small flies while also taking the occasional pollinator, and its numbers are low enough that neither effect dominates.

Seasonal behaviour: adults are most obvious from late spring through summer. Males mature earlier and wander in search of females, then live only a short time after mating; females feed through midsummer, build a single guarded egg sac and rarely survive to see it hatch.

Relationship with humans: harmless and quietly beneficial, and a good indicator of an unsprayed garden, since broad-spectrum insecticide removes both the spider and its prey.

Similar spiders and how to tell them apart

Quick facts

Did you know?

• The green crab spider is one of very few North American crab spiders that is green, which is exactly why it is so often missed — searchers look for the familiar white or yellow flower spider.
• The red bands along the abdomen are optional. Two spiders on the same plant can differ completely, and the bands are no guide to sex or age.
• The male’s courtship veil of silk does not restrain the female at all; she can walk out of it whenever she chooses.
• Because it stays green year round, this species hunts on leaves and stems long after the flowering season ends, when white and yellow flower spiders have run out of matching blooms.
• At 3 to 7 mm, a female regularly kills insects longer than herself — a consequence of venom that acts far faster than the prey can react.

In summary, this is a tiny, harmless and superbly camouflaged ambush hunter of North American foliage. It builds no web, never turns white or yellow, poses no risk whatsoever to people, and quietly removes a steady stream of small pest insects from gardens and field margins.