24 August 2009

Gryllacrididae species A - Raspy Cricket

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Raspy Cricket - Gryllacrididae sp. A

The crickets in this worldwide family are not well known with the last major Australian review published in 1990 by Rentz and John. The Australian Faunal Directory lists 28 genera and almost 100 species, but estimates suggest the number of species is closer to 200 and worldwide 600, giving Australia about a third of the total family population. Gryllacrididae is primarily a southern hemisphere family with only a few species occurring north of the equator, thereby providing strong evidence for a Gondwana origin.

Many species dig vertical burrows and line them with a silken substance they produce from their mouths, others use this substance to make shelters by gluing leaves together. They are nocturnal and being omnivores, venture forth at night to hunt small invertebrates or to feed on vegetation or detritus. Interestingly, there is evidence that they use the stars to navigate the way back to their shelters.

From an ecological point of view, these crickets play an important role in the food chain and although they are predatory themselves, they are commonly preyed upon by larger animals, particularly mammals and the larger spiders. Another feature of the Gryllacrididae crickets is their very long antennae, often several times the length of the insect, which they fold back over themselves.

There are several common names for these crickets, but most of the Australian ones are generally known as Raspy Crickets, due to the raspy sound they produce when they rub their abdomen against their legs, which they can use as a means of defence. Most of these crickets are apparently very habitat specific, but if you have ever taken the trouble to look closely at them, superficially they all look very much the same. So with that factor in mind and without microscopic examination, we appear to have at least two or three common species (one or maybe two large, and one much smaller) in the sandy heath habitat where most of my observations of these insects have taken place.

The single species above, or possibly 2 similar sized species are the larger of the local Raspy Crickets, having a head/body length of around 3 cm (11/4") and are regularly encountered during December and January, and again during April and May, leaving them noticeably absent during winter and the height of summer when they presumably remain in their shelters.

My thanks to Dr David Rentz for identification.