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July 2021

Beauty is in the eye of the beholder

I brushed my hand against a wattle and something stung me. It was intense pain like a wasp sting. When I looked I saw this pretty caterpillar. Why is it so attractive?

Answer

The colours on this cup moth caterpillar are a warning of painful stings for any would-be predators.

You have been stung by a cup moth caterpillar. The one you’ve found is a widespread species called the Wattle Cup Caterpillar (Calcarifera ordinata). Caterpillars of the moth family Limacodidae are famous for the vibrant colours displayed by many species. Those colours are not just for show, but convey an important message.

Colours evolve in nature for a variety of reasons. In some cases the brilliant hues are actually displayed to be attractive and admired. Many male jumping spiders (family Salticidae) are strikingly marked in a bold livery of iridescent blues and reds. Countless birds exhibit breath-taking hues, with lilac bibs, scarlet crowns, metallic blue breasts and so much more. Some lizards too, such as males of the aptly named rainbow skinks (genus Carlia), acquire bright blue and red pigments on their throats and flanks during the breeding season. In all these cases, the beauty has a purpose. It is to attract. The colours have evolved for males to display to females in their quests for mates.

But sometimes the story behind the bright colours is more sinister. In the case of the cup moth caterpillar, they are there to repel. They warn of penalties in the form of acute pain for anything that gets too close. Such warning colours are called aposematic colours. They are widespread in the animal kingdom to advertise the potential for stings, bites, repugnant fluids and nasty tastes.

Cup moth larvae display a striking array of lurid colours. With those colours there are spines, each of them hollow and attached to a venom gland. The slightest touch can elicit an immediate, painful reaction, so they have no need for camouflage. They tend to sit comfortably on exposed leaves with the expectation that few, if any animals will attempt to prey on them. Those that do will sorely remember the experience and avoid them in future. Experiments have shown that some paperwasps, natural invertebrate predators of many caterpillar species, demonstrate an aversion learning response after negative experiences with cup moth caterpillars. When they know what they are, they leave them alone.

Cup moth caterpillars go under a number of names and some are quite evocative. The name ‘cup moth’ alludes to the round shape of the cocoon, but ‘Chinese junk’ and ‘Bondi tram’ are based on the unusually shaped larvae. So if you see cup moth caterpillars, enjoy and admire them but also be warned. There is a reason for those fabulous colours. Those caterpillars are not just sitting pretty!

Want to know more? Our Discovery Centre is a free service open seven days per week, with experts ready to answer your questions. You can phone, write, contact us via our website or pop in. If we don’t know the answer we will try to find out for you.

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