Yesterday I was
fortunate to watch what seemed to me to be a very strange example of insect
mating behaviour. On sunny days I keep an eye out for dragonflies at the pond
and yesterday noticed a small red coloured one buzzing around and resting on
the lily leaves. When I came back with the camera I saw that there were now two
of them flying joined tail to head - they were flying in tandem. I was
mystified. They couldn't be mating because the business end of the dull
coloured one at the back was too far from whatever the red one at the front had
in the way of wedding tackle. That was strange enough, but then something even
stranger began. The red one, whom I took to be the male, seemed to be thrashing
the water with the brown one. The two together were using a whipping action to
bring the tail of the brown one down to the water for a fraction of a second -
again and again, moving round the margins of the pond. I had seen dragonfly egg
laying before and this was clearly what these two were up to, but why on earth
were they doing it together? The male could not have been passing sperm so why
was he there?
I got on the
internet and looked it up. Whoever named the species must have been having a
bad day for names: this small red
damselfly turned out to be exactly that - a Small Red Damselfly. Interestingly
they are rare so this was quite significant. I also found a name for the
behaviour "Oviposition in Tandem" but no explanation. The only bit of evidence I could find was an extract
from an experiment which seemed to show that the female gains nothing from
having a male gripping her head with his tail. It must therefore benefit the
male - presumably it is to prevent other males getting to her before she lays
his eggs.
The next time I
stood by the pond with the camera ready one male looked as if he was standing
guard. He was perched at the edge of a lily leaf scanning the air above and
around the pond with his enormous eyes, twitching his head from side to side.
As soon as anything moved in his territory he was off chasing it. If it turned
out not to be a female small red etc. he would return to his look-out post. If
he caught a female the two would fly around the pond in tandem. I couldn't tell
whether this behaviour always leads to egg laying, but it seems a reasonable
assumption that the grip of the male would trigger egg laying behaviour.
I would be
interested to know if anyone else has come across this - or seen on of these
handsome little beasts.