Sunday, June 12, 2005

Redback Spiders

Andrade's web page is fascinating, not to mention that she must be most attractive spider copulation researcher imaginable!

Maydianne C.B. Andrade

Much of my current research involves studies of the sexually cannibalistic Australian redback spider (Latrodectus hasselti), and its close relatives, the black widows (genus Latrodectus). Redback spiders are intriguing because males actively 'encourage' females to cannibalize them while they mate. Unlike most other sexually cannibalistic species (e.g., praying mantids) where males attempt to escape from the female's jaws, redback males actually 'somersault' onto the female's mouthparts during copulation = male sexual sacrifice.

The copulatory somersault
(A) Copulation begins with the male standing on the female's abdomen. Both spiders are facing in the same direction and are 'belly to belly'. The male has two copulatory organs (the palps) that are attached at the anterior-most part of his 'head' (cephalothorax). Copulation begins when one of the palps is inserted into the female's genital opening. In most other black widow spiders, the pair copulates while in this posture.

(B) In redbacks, however, a few seconds after palp insertion, the male, using the palp as a pivot, moves into a 'headstand' posture.

(C) The male then quickly turns through 180 degrees, landing with his 'back' (the dorsal surface of the abdomen), directly above the female's fangs. In most matings, the female begins to extrude digestive enzymes almost immediately. She also pierces the male's abdomen with her fangs and begins to consume him while he is transferring sperm.

There's a video of this on her web site.
A previous spider mating post

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