Wasp Spider

• The male is so small that he can enter the female's web undetected, and waits for her to finish her final moult so as to mate while her chelicerae are still soft. Even so, many end up eaten.
• In the centre of the web it weaves a zigzag called a stabilimentum whose function is still unclear: it has been suggested that it attracts insects, that it strengthens the web, or that it warns birds off so they do not fly through and destroy it.
• Its eyes shine in the dark because of the tapetum lucidum, the same tissue that makes cats' eyes shine, even though its own eyesight is very poor.
• Its web carries a stabilimentum: a zigzag band of white silk running vertically down it. Its function has been debated for a century, and the main hypotheses are that it strengthens the web, that it attracts insects by reflecting ultraviolet, or that it makes the web visible to birds and stops them breaking it.
• Its yellow and black bands mimic a wasp, a mimicry that protects it from birds even though it is harmless.
• Sexual cannibalism in this species is extreme for the male: in most matings the female devours him, and he helps bring it about by deliberately breaking off the tip of his copulatory organ inside her, where it remains as a plug preventing another male from fertilising her. His death is part of the strategy.
• It is expanding rapidly into northern Europe with the warming climate: within a century it has colonised Germany, the Netherlands, the United Kingdom and Scandinavia.
• Its egg sac is large, shaped like a brown paper urn, and holds several hundred eggs that spend the winter inside it.

Skeleton type

Invertebrate - chitin exoskeleton (arachnid)

Habitat & environment

Dense vegetation in somewhat damp places: rushes, reeds and grasses along riverbanks, damp meadows, crops and floodplain copses. Mediterranean in origin, it has spread north as far as Scandinavia and the British Isles

Sexual maturity

The female reaches maturity after her final moult

Gestation / incubation

The eggs spend the whole winter inside the ootheca and the young emerge in spring

Litter / clutch size

300 to 400 eggs per ootheca according to Iberian sources, with estimates of over a thousand in others. A female can make two or three oothecae in a single summer

Sources consulted: World Spider Catalog (Naturhistorisches Museum Bern); Fauna Ibérica; Elgar 1991; Fauna Europaea; El medi natural del Bages i del Moianès; Arácnidos Ibéricos

Best time: From June to October, when its webs are visible among the tall vegetation