Thopha saccata
Double Drummer cicada, Thopha saccata, in Wedderburn, NSW. Image: Dave Britton
© Australian Museum

Our collection managers can’t know everything, but part of their job is knowing who to ask when they don’t have the answer.

In my position as collection manager of entomology (the insect collection) I am sometimes asked what my expertise is. My flippant answer to this is that I am expected to know about everything!

Collection managers for each faunal group in the Museum are expected to have a broad knowledge of their group, and will often get asked questions that go well beyond identifying a particular animal. In practice we can’t know everything, but part of the job of collection manager is the knowledge of who to ask when we don’t know the answer.

We have an impressively broad range of expertise on hand in the Museum, and outside of the Museum, and we can draw on this when necessary. With this in mind, I got asked a very good question a week or two ago. Roger Phillips contacted me via the web enquiry link, and asked this:

Holes made by Double Drummer cicadas, Thopha saccata, in Wedderburn, NSW.
Holes made by Double Drummer cicadas, Thopha saccata, in Wedderburn, NSW. Matchbox included for scale. Image: Dave Britton
© Dave Britton

“I am intrigued and nobody can answer my question - hope you can! I have lots of cicada holes in my lawn and garden, but cannot understand how the nymphs can emerge from the ground without leaving any dirt residue around the top of the hole - some of these holes are 6 to 8 inches deep and around the width of my little finger - ants leave a stack of dirt around their holes.”

I was stumped, but fortunately I have the ideal source of information in Dr Max Moulds, a world expert on cicadas, a Senior Fellow of the Museum who now lives in Kuranda. I emailed the question through to him, and got a reply:

“Cicada nymphs feed from roots of trees and produce a lot of excess watery waste. This helps compact and stabilize the walls of their tunnel. Hence no soil is excavated. Before nymphs emerge they tunnel almost to the surface in preparation and only remove the last few millimetres on exit which tends to fall back into their tunnel. That is why there is never any free soil around their exit holes.”

A great question and an equally great answer!