Thursday, 5 February 2015

Parental Care Displayed in A Katydid

Katydids have figured prominently in research concerning male/female relationships, sexual selection, communication, and other areas of insect behaviour.

Parental care has been demonstrated in a few species. Here I report on the concealment of eggs by a female katydid. The observation was made at Talaroo Station, west of Mt Surprise, Queensland.

Of course, the mere act of laying eggs (oviposition) in katydids is an example of parental care to some degree. Katydids lay eggs in the ground, in leaf tissue, in wood and other media. But coating the egg with an external substance is unusual.

In the Guide to the Katydids of Australia (Rentz, 2010: 170) I noted a female Polichne argentata that had just completed laying an egg on a twig and then covering it with a bit of dirt that it had gathered from the ground beneath.
Polichne argentata with egg just laid and covered with bits of soil

Recently I made a similar observation on another, probably undescribed, species of Polichne. I was fortunate to have my camera at the ready and was able to record most of the event.

In this observation, the katydid first chewed a piece of bark from a eucalypt.

Then it guides its egg into the selected crack in the bark of the tree.

 The act of oviposition.
 The egg deposited.
The final act of plastering the egg with the chewed bark it had gathered just prior to oviposition.

So what is the "reason" for the unusual ovipositional strategy? Covering the egg with a foreign substance may aid in reducing desiccation in the normally dry habitat of the Australian outback. It may also afford some protection from minute hymenopterous egg parasites.  Or it may be none of these explanations. It seems less likely that it obscures the egg from potential vertebrate predators. 

Literature Cited

Rentz, DCF 2010. A Guide to the Katydids of Australia. CSIRO Publications, Pp. 1-214. CSIRO Publishing, Collingwood, Vic.

1 comment:

Linda Rogan said...

Interesting story Dave. It was great to meet you and see some of your local critters.