Have you ever noticed strange lumps and bumps on the leaves and stems of native plants? Galls are especially common on gum trees and wattles, and they are abnormal plant growths that form in response to invasion of plant tissue by a variety of organisms. Galls can be caused by certain species of wasps, flies, beetles, psyllids, coccids, thrips, moths and aphids, as well as by nematodes, mites, bacteria or fungi. This post concentrates on some common gall-inducing insects found in Australia. Continue reading Gall-inducing insectsShare this:
Men are from Mars and women are from Venus or so the saying goes. However the anatomical differences between male and female humans are relatively minor when compared to the differences between male and female insects.
“Why is this ‘ant’ attacking a ‘fly’ via its ovipositor?” an insect enthusiast asked me in an email recently (the insects in question can be seen below). The image clearly illustrates sexual dimorphism. My Dictionary of Entomology, a massive tome only owned by insect nerds like me, defines sexual dimorphism as ‘differences in size, shape, anatomical features, colour or behaviour between males and females of a species’.
Insects are ectothermic meaning they don’t generate their own body heat, and rely on external sources to regulate their body temperature. Freezing temperatures are life threatening to many insects, so how do they survive winter?
One July morning I went down to my vegetable garden to see how the plants had survived the deep freeze (-3°C) of the night before. I wasn’t surprised to find my brassicas were covered in ice crystals, but I didn’t expect to find a cabbage white butterfly (Pieris rapae) larva also encrusted in ice. I decided to keep an eye on it, so after the day warmed up a bit I revisited the garden to find the caterpillar happily munching on the plant. How did it do it?
As winter sets in there are less and less flying insects to be seen, which might seem like a bad time to be an entomologist. But even in the middle of June there are still plenty of insects around – you just need to know where to look. Personally when I get a bit desperate for hexapodal company I head for the nearest gum tree.
Gum trees (Eucalytpus spp., Corymbia spp and Angophora spp.) are hosts to myriad insects but today I want to talk about the insects which form “lerps” on gum tree leaves. A lerp is the white sugary, waxy covering which the immature stages of some psyllid insects (family Psyllidae) produce from liquid excretions known as honeydew. There is disagreement among scientists as to the purpose of the lerp. Some argue that the lerp is protection from predators, while others insist that it provides the immature psyllid with a more humid environment. Perhaps it is a mixture of both. The image below shows an intact lerp in the upper image and then moved to reveal the Glycaspis sp. nymph underneath.