February 2015

Butterfly boom

We have received many inquiries in the last few weeks asking us why there are so many butterflies on the wing.

Answer

Blue Tiger Blue Tiger Lemon Migrant Lemon Migrant Caper White Caper WhiteThere is no simple explanation for the recent explosion in butterfly numbers.

The recent extreme hot and humid conditions provides perfect flying weather for butterflies as they don't need to consume as much energy to keep warm and hydrated. The phenomenon of a 'butterfly blizzard' is often short lived, a sudden drop in temperature, rain or cloudy weather and the butterflies become 'invisible' again.

Not all regions are experiencing this phenomenon and the species involved seem to vary between areas. Our butterfly booms usually only feature one or two species but this year is different, with many species being more common than usual. Blue Tigers, Caper Gulls, Lemon Migrants, Blue Triangles, Caper Whites and a host of others are adding a vibrant splash of colour to parks, gardens and local bushland.

As to other possible explanations, we offer the following comments: We have not had exceptional rainfall; just enough to rescue plants from drought conditions and promote new growth.  Butterfly breeders, Tony and Katie Hiller have noticed that dry conditions are better for butterflies and their leaf-eating caterpillars. Neither thrives in wet conditions which stop butterflies from flying and cause caterpillars to develop fungal and viral diseases which can retard growth and cause mortality.  Parasitic wasps and flies which reduce numbers of butterfly larvae and pupae seem to be in lower numbers in drought conditions.

Some Australian butterflies species (like the Blue Tiger and Caper White) are well known for population explosions and dispersal flights.  Although the movement of these butterflies often appears to be co-ordinated and directional, it is not true migration.  In North America, a true seasonal migration of the Monarch Butterfly occurs and the butterflies avoid cold northern climes by flying south to overwinter, returning in the spring.

We are not sure what is so special about this particular butterfly season but one thing is clear, we should enjoy them while they last!

Queensland Museum's Find out about... is proudly supported by the Thyne Reid Foundation and the Tim Fairfax Family Foundation.