Male redbacks' risky foreplay ritual

Foreplay can be a matter of life or death for the male redback spider in a courtship ritual that appears even more demanding than previously thought.

It's long been known that the female redback who is roughly twice the size of her male counterpart, regularly eats a number of her male courtiers, although exactly what determines who gets eaten has been unclear.

New Canadian research suggests that it depends on whether the female has been satisfied by the duration of the stimulatory courtship, which entails the male vibrating the female's web for approximately 100 minutes.

The report appears in the latest edition of the journal Proceedings of the Royal Society B.
Parasites of love

Once the threshold has been reached, a female is unlikely to eat the male upon copulation. She is also unlikely to eat other males who attempt to mate with her, whether or not they were involved in the courtship.

University of Toronto researchers Jeffrey Stoltz and Dr Maydianne Andrade, point out that it means that weaker - and perhaps smarter - males can exploit the courtship work of their rivals.

But in the end, they say the best odds for a redback male to mate successfully and avoid being eaten afterwards are when he has the female all to himself and can perform the vibrating courtship at length and uninterrupted.

The work was able to be done using a cluster of redbacks originally imported from Australia, but now living, breeding and cannibalising each other in the Ontario laboratory.
Female choice

The redback mating process is full of curiosities including that the tips of the male mating organs are broken off inside the female after copulation.

It's thought that this occurs in order to plug the female genitalia to prevent other males from depositing their sperm.

The female produces a number of batches of eggs from that sperm deposit during her lifespan.

Having lost their mating organs, it had been thought that the males offered themselves to be eaten by the female to ensure she had the strength to go on and produce the next generation.

The theory was that a male's strength and size determined whether he survived the ordeal to copulate again.


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