How male spiders try to trick females into sex

November 14th, 2011 - 1:46 pm ICT by IANS  

Washington, Nov 14 (IANS) Male nursery web spiders try to trick females into sex with worthless silk-wrapped gifts. But females are not so easily impressed.

Most gifts contain insects, but some gifts are inedible plant seeds or empty exoskeletons left after the prey has already been eaten, presumably by the male himself, useless from a female perspective.

Males also ‘play dead’ if a female moves away and then attempt to re-establish mating, the journal BMC Evolutionary Biology reports.

Maria J. Albo, genetic scientist at the University of the Republic, Montevideo, Uruguay, explained: “The evolution of male deceit involves a complex equation of costs and benefits.

“It costs the males to find and wrap a gift, but these costs can be reduced if the male does not have to first catch his gift, or gives one that has already been eaten,” said Albowho, who led the research, according to a a Montevideo statement.

Male spiders were provided with either a potential gift of a fly, or a worthless item, such as a
cotton wool ball, a dry flower head, a prey leftover (previously eaten housefly), or no gift at all.

All the gifts were approximately the same size, so the females would not be able to tell what the gift was without unwrapping it.

It appears that both male and female spiders are apparently able to assess the value of the gift
and modify their behaviour accordingly.

Not only did the female spiders end mating sooner with an inedible gift, but male death feigning (thanatosis), which is triggered by the female attempting to end mating and run away with the gift, occurred in half of the matings involving an edible gift, but only once with a worthless gift.

The benefit of the gift is longer mating, which leads to more sperm being transferred, and potentially a higher number of offspring. However, the females are wise to deception and terminate mating early for worthless gifts.

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