Spitfire
Some years ago there seemed to be many Spitfires and Gum Moth caterpillars
in the street trees around Sydney. Now there do not seem to be any.
Where have they all gone?
Gum Moth
There have been several reasons suggested for this phenomenon.
One suggestion is that the replacement of the old incandescent street
lights by fluorescents with their high UV output has disrupted the
mating process of many lepidoptera species.
Another is that the build up of lead from leaded petrol exhaust
deposited on the foliage poisoned them. If this is the case,
perhaps they will come back soon now we are mainly using
unleaded fuel.
Another is that the populations naturally go through random highs
and lows. For example there was an amazing population explosion
of Gardenia Bee Hawks in 2003 in Sydney, yet
they were rare in the preceeding 10 years and also since in 2004.
It has also been suggested that the increasing population of
Euro Wasps (Vespula germanica, VESPIDAE) is
killing the caterpillars. These wasps have been observed
cutting caterpillars up to take back to their nests.
Gardenia Bee Hawk Caterpillar
(updated 24 May 2008)
