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Insects and other arthropods

Crab spiders

English
Photo: Insectarium de Montréal (Guillaume Dury)
Crab spider

Tabs group

Description

It’s easy to understand why the Thomisidae are called “crab spiders”: their flattened bodies, the way they often hold their front legs apart, ready to catch their prey, and the way they scuttle sideways when disturbed.

They are from 1.5 to 11.3 mm long. Their first two sets of legs are generally longer than the others. They are used for hunting, while the four hind legs are used for movement. These spiders generally move sideways or backwards.

Many species use mimicry to camouflage themselves in their surroundings.

Some resemble bird droppings, while others can even change colour to match the flower they are living and hunting on.

The males are often much smaller than the females. In some genera, the two sexes are quite dissimilar, even of different colours.

Life cycle

Crab spiders grow by shedding their “skin” when they moult. They do not undergo any kind of metamorphosis. The young spiders look like smaller versions of adults. The number of moults depends on the species.

To protect their eggs, the females in this family lay them all at once in a silken sac and guard it.

French name
Araignées-crabes (thomises)
English name
Crab spiders
Class
Arachnida
Order
Araneae
Family
Thomisidae