September 2018

Bright Green Slug

This bright green creature was adhered quite firmly to a camphor laurel leaf on the ground. It looks like a slug but I have never seen anything like it. What is it?

Answer

Image Credit: Warick Nash Image Credit: Warick NashThis beautiful bright green creature is actually the caterpillar of a species of moth. It is one of the cup moths, belonging to the family Limacodidae. The moths are named for their round, cup-like cocoons, but the caterpillars are characterised by their stout build, and often extremely unusual appearance. Many are ornamented with clusters of stinging spines and they are often brightly coloured. The vivid hues act as a warning, advising would-be predators that these caterpillars are not to be meddled with. Your caterpillar belongs to a group of slug-like larvae which has given rise to the common name “Slug Moths”.

Moths and butterflies belong to the order Lepidoptera. By the very nature of their developmental stages, where caterpillars bear no resemblance at all to the adults, identification of Lepidoptera demands two completely separate identification skills. This means identification of caterpillars to species level can be a tricky business.

For starters, when using a photograph there are often diagnostic features not visible in the picture. They may require examination of a specimen under a microscope, as a number of caterpillar species can look quite similar. Also, caterpillars have a series of growth stages called instars, and sometimes these may look quite different from each other. It may often be necessary to rear the larva to adulthood in order to reach a correct identification. This process may be further complicated because many adults are also very difficult to tell apart without specialised skills. There are also plenty of undescribed species awaiting attention.

In the case of your caterpillar, there are a couple of genera with larvae that look similar.  It could be a species of Eloasa (possibly E. symphonistis) or a species of Chalcocelis (possibly C. albiguttatus). These have not been recorded on camphor laurel, so the caterpillar may have finished feeding on its food plant and be on its way to pupate

Caterpillars are extraordinary insects, exhibiting a near-limitless variety of form, ornamentation and colour. Their metamorphosis from grubs to winged, flying insects seems almost too remarkable to be true. And they remain among the most challenging insects to identify.

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