Mimetidae (pirate or cannibal spiders) (original) (raw)

(Phylum: Arthropoda, subphylum Chelicerata, class Arachnida, order Araneae, suborder Araneomorpha)

The Mimetidae, with the Scytodidae(spitting spiders), are the stealth fighters of the spider world. Due to their araneophagous habit of preying mainly on spiders, they are commonly referred to as pirate or cannibal spiders. They are harmless to man.

Mimetus sp. from the De Hoop Nature reserve near Bredasdorp.

Mimetids are small spiders (3 to 7 mm long) and are intermediate between the Aranaeidae and the Theridiidaein appearance. They are pale yellow to brown in colour with the cephalic area (head area around the eyes) dark brown. The abdomen is usually marked with yellow and brown speckles and variegations. The legs are usually banded.

The two anterior legs are long and slender and the tibia and metatarsus of these anterior legs are armed with rake-like macrosetae (socketed hairs) that are interspersed with smaller macrosetae, all situated prolaterally - a diagnostic feature of the family. In the genus Ero, the length of the first pair of legs is 1.3 (or less) times the length of the fourth pair of legs. In the genus Mimetus, the first pair is 1.5 times longer than the fourth pair.

The globose abdomen usually has two dorsolateral (on top at the sides) humps and has isolated, scattered setae.

Prey capture was first described in Britain by W. S. Bristow in 1958. From his and further Australian research, it appears that they prey mainly on web-living Araneidae and Theridiidae but also on Agelenidae, Dictynidae, Linyphiidae, Tetragnathidae and the cursorial Philodromidae, insects, Lepidopteran larvae, spider eggs and they also steal the prey from the webs of spiders.

Mimetids can normally be observed at dusk suspended from a few silk strands at the edge of a spider web. This would not be its own web but that of another spider as it does not construct a web of its own. At night it will vibrate the web, mimicking either captured prey or a courting male spider of the species that occupies the web. The duped spider will rush to investigate and once within reach, the mimetid will move forward with such stealth that the movement is barely noticeable. The four anterior legs are stretched over its prey and it is quickly drawn forward, its legs pinned down with the spines on the attackers forelegs. The mimetid then bites the prey in the femur, instantly immobilizing it. It is not known whether the bite kills or merely paralyzes. Bristow observed that if the prey is bitten on the body, a vigorous struggle ensues that requires an additional bite to the legs to subdue it.

While mimetids are ferocious on the attack, they are gentle during courtship - albeit one of the briefest courtships in the spider world. The female produces 3 cocoons each suspended from silk thread and each containing about 8 eggs.

The Mimetidae family includes 12 genera, four of which occur in the Afrotropical region of which Ero and Mimetus occur in South Africa. _Ero_includes two species that occur in the Western and eastern Cape respectively. While the two described species of Mimetus are both recorded from Kwazulu Natal, its interestingly to note that the Mimetus species illustrated above was photographed by Norman Larsen at the de Hoop Nature Reserve near Bredasdorp illustrating the need for further work on the group.