The Riddle Cracked - Why in Some Species of Spiders the Males are much smaller than Females

In some species of spiders the males are much smaller than females. Till now no satisfactory explanation was in place for this riddle. Now a Spanish research team headed by Dr Guadalupe Corcobado from the Spanish National Research Council's Arid Zones Research Station in Almeria has come up with an explanation.


The researchers say evolution favours small, light males as it gives them the ability to traverse thin strands of silk. Smaller size also ensures more mating opportunities. Large females are favoured because they reproduce more abundantly. In some species females are more than 12 times longer than males.


Plant dwelling spider produce strands of silk and allows the wind to carry one end of it. When the silk strand lands on a leaf or stem the spider pulls it tight and secures the near end. It then crawls across hanging upside down from the strand. Smaller sized males were very successful in bridging.


The link to bridging is a new concept derived by the Spanish researchers.


Details appear in the journal BMC Evolutionary Biology.