with Spider Cannibalism During Mating
dinner and date"
with Spiders (Coleoptera;
Time: Oligocene to Miocene
by 20 by 9 mm
Region near Santiago, Dominican Republic
exceedingly rare occurence on foosil amber: spider mates with the
female appearing poised to cannibalize the smaller male.
spider mates are accompanied in their resin tomb by two Coleopterans
(one large and one small) and a small Dipteran.
research dispels a common misconception that the primary reason
for spiders engaging in cannibalistic mating was that the male body
provided nutrients for the female. Rather, the real reason for this
practice has to do with sperm competition, whereby each male tries
to ensure their sperm fertilizes as many of the female's eggs as
possible, so as to pass on their genes to the most offspring. Female
spiders may mate with many males and store the sperm, which they
can use to fertilize egg sacs for up to two years. When the male
is eaten during mating, however, more sperm is transferred since
it continues to ejaculate while being eaten. This increases the
time spent mating and the odds that their sperm will fertilize more
eggs. Evolution predicts that the genes that encode this behavior
will continue to be passed to progeny so long as it produces more
offspring on average than males that avoid being eaten.
pix to enlarge