Monday, 14 February 2011

Tinkling crickets

Most of us hear the very low pleasant sounds of crickets coming from the undergrowth in the rainforest or along rainforest margins.

Cricket Classification

Most crickets are classified in the family Gryllidae. There are currently eight subfamilies in this large family. Recently some taxonomists have elevated some subfamilies and tribes to full familial status. As an example, the Mole Crickets, once considered as a subfamily of the Gryllidae, are now considered in their own family, the Gryllotalpidae. In addition, the Scaled Crickets are now in their own family, the Mogoplistidae. Most taxonomists follow the classification presented on the Orthoptera Species File (OSF). This is an active catalogue of the Orthopteroid insects of the world. (http://orthoptera.speciesfile.org/HomePage.aspx). It is kept up to date and a Committee adjudicates on controversial matters.

Cricket songs, when compared to those of katydids, are melodious to the human ear. Katydid songs are more metallic, buzzy or tinny. The pitch (carrier frequency) of the two taxa is usually very different. Cricket songs have pure carrier frequencies between 2000 to 9000 cycles per second. Katydid sounds are generally much much higher in frequency.

Here I present the Calling songs of two cricket species. One is a widespread species, the other more local.




Homoeoxipha lycoides (Walker) seems most at home in tall dense green grasses. The crickets can be found in their greatest numbers along roadsides and forest margins. Numbers can be large and the sounds of an aggregation of calling males are very distinctive, though very low in volume. Males sing mostly during the day and early evening. These crickets are often attracted to lights. The call is a continued, prolonged wavering trill, a series of pulses. The pulses come at about 51 per second in distinct groups of 8. The wingstroke in this species is much greater than that described below for O. coorumbena.



Ornebius coorumbena Otte & Alexander is nocturnal. The crickets occur in low shrubby vegetation in the rainforest to about 2m. They feed on detritus that falls from the canopy onto leaf surfaces. They are not usually attracted to lights. Their calls can be the dominant cricket sound at certain times of the year. Males call, isolated from one another, never in aggregations. The song consists of groups of pulses (chirps) with 7 pulses separated by about a second. Each of the 7 pulses corresponds to a wing closure.

These notes served as the basis for an article in Audio Wings. This is the journal of the Australian Wildlife Recording Group. There are two issues a year containing articles dealing with wildlife sounds ranging from insects to birds, mammals and reptiles. There are important reviews of new recording and analyzing gear. A workshop is held every second year in the field where wildlife recordings are made, analyzed and techniques compared and reviewed.

For more information on this club, contact the President, Mr Fred van Gessel fvangessel@optusnet.com.au

Finally I am very grateful to Mr Ken Hickman who has helped me to understand the fairly complex nature of embedding sounds into this blog. Thanks Ken.

Literature
The "bible" for Australian cricket information is:
Otte, D., Alexander, R. D. 1983. The Australian Crickets (Orthoptera: Gryllidae). Academy of Natural Sciences of Philadelphia, Monograph 22. Pp 1-477.

This book is available from the Academy of Natural Sciences of Philadelphia or over the web.

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