Reproduction

Males of this spider exhibit spontaneous, programmed sudden death while mating. Immediately upon inserting his second palp (secondary sperm transfer organ) into the female epigyna (sexual organ), his heartbeat ceases. Foellmer & Fairbairn (2003) postulate that this unusual behavior increases the male's paternity because his palps and body act as mating plugs, thus making them difficult to remove by the female or by competing males.

Life History

A. aurantia webs can be up to two feet across and individuals hang head down, with legs in pairs at the center. Webs are usually decorated with bright, ultraviolet reflecting silk in a vertical and cruciate (cross-shaped) zig-zag pattern. This extra webbing is commonly seen in other spider species' webs and is called the stabilamentum. Hypotheses to explain the origins and adaptive advantage are as varied as the webbing itself (Herberstein et al., 2000):

• stabilising and strengthening the web
• hiding and concealing the spider from predators
• preventing web damage by larger animals, such as birds
• increasing foraging success
• providing a sunshield

Although there is a considerable and conflicting body of research on the adaptive significance of A. aurantia stabilamenta, most experimentation reveals prevention of damage and increased foraging success.

References

Foellmer, M. W. and D. J. Fairbairn. 2003. Spontaneous male death during copulation in an orb-weaving spider. Proc. R. Soc. Lond. B (Suppl.) 270: S183-S185.

Herberstein, M. E., C. L. Craig, J. A. Coddington and M. A. Elgar. 2000. The functional significance of silk decorations of orb-web spiders: a critical review of the empirical evidence. Biological Reviews 75: 649-669.