Monday, 30 April 2012

Chirping lily beetles

The sun shone in all its glory to end this most rainy April. Many insects came out of their temporary hiding places to dry out and enjoy the warmth. Some of these were Scarlet Lily Beetles. I wasn't sure if I had an infestation, as I had collected just a couple of adults in the last few weeks, but today I found 12, the first ones were a mating couple. As I found them I placed them in a plastic pot, and while I was carrying it I noticed a faint chirping call. I thought that there must be a nest nearby with calling chicks, but then I realized that the sound was actually coming from the pot: the disturbed Lily beetles were stridulating! when I touched them, they chirped repeatedly. You can watch this short clip of them in the pot, as I push them inside the pot, they chirp - I was trying to place the camera on the pot opening to improve the sound recording, but they kept climbing up the pot.



The first description of the stridulation of this beetle was written by the early entomologist René Antoine Ferchault de Réaumur in 1737:
when one holds it, it lets a little cry be heard, produced by the friction of its last abdominal segments against the elytra, the more one presses the elytra against the body, the louder it cries
More recent studies have confirmed this description, and also shown that stridulation is common in the Lily Beetle subfamily (Criocerinae). The stridulatory apparatus consists on a file on the last tergite - the dorsal end of the abdomen - made of microscopic parallel ribs, which are scraped by files of sharp denticles in the underside margins of the elytra. The sound is produced while the abdomen contracts, and these contractions can be amazingly rapid, up to 200 times per minute and is loud enough to be heard if the beetles are less than 30 cm from your ear. The high variability of the chirps and the situations in which they are produced suggest that this behaviour is a defence mechanism: the beetle will chirp if captured and the sound can startle the potential predator to release the beetle before swallowing it. In other beetle species chirping is used in intraspecific communication, with the lily beetle, is is yet another way of avoiding being eaten.

More information
Michael Schmitt & Dieter Traue. 1990. Morphological and Bioacoustic Aspects oî Stridulation in Criocerinae (Coleóptera, Chrysomelidae). Zool. Anz, 1990, 225: 225-240.

7 comments:

Phil said...

Amazing! I had no idea they did this - makes me (almost) wish we had lily beetles here in the North East ....

Africa Gómez said...

I was quite surprised they did this and had to show everybody in the family, it is so cool. I ge tthe impression they won' t take long to get to you. I saw my first last year and the difference in density is staggering. Enjoy your lilies while you can!

Africa Gómez said...

Phil, I think they have actually arrived at your doorstep:
http://www.rhs.org.uk/Science/Plant-pests/pdfs/Lily-beetle-distribution-2012

alberta ross said...

never knew they chirrped - I gave up growing lilies because I hate killing stuff in the garden and if I didn't after the first couple of years I had no lillies - so i ceased - I will only kill that which threatens me and mine - so much easier that way:)

Africa Gómez said...

Alberta, I totally agree, I don't like to have garden wars and now pacifically coexist with slugs, snails and other bugs. So far I have been getting rid of lily beetles, but I am so curious about them now that I am happy to sacrifice my lilies - which so far have been in the same pots for years in order to learn about them. I haven't seen eggs or larvae in the garden yet, but I can't wait now.

John M. said...

That's quite stunning. I am amazed that they do that. These 'pests' are the ones that i would want in my garden because they're adorable. Thanks for the nice video and information.

Africa Gómez said...

Hi John, thank you for your comment. They are fascinating, I do hope I keep seeing them around.