Monday, 9 January 2017

Tiny Treasures

Sweep-netting over some rocky ground with patches of native and introduced grasses and forbs revealed a population of Pygmy Mole Crickets.

Pygmy Mole Crickets could easily be overlooked. These are only about 3 mm in length! They are strong jumpers and can leap a metre or so with a single hop. :Pygmy Mole Crickets are members of the family Tridactylidae.

A number of species are known from Australia and are placed in two different subfamiles. I covered these in the book below. The crickets, not really "crickets" in the true sense, live in short burrows they make in wet ground. They are said to feed on algae that the scrape from pebbles.


 This is Xya muta (Tindale). The tips of the hind legs are highly modified for swimming, the paired appendages acting like paddles.

Note the very short wings. This is a flightless species. It was originally thought that these insects were related to Mole Crickets (Gryllotalpidae) but they were found to be examples of convergent evolution.  John & Rentz (1987) showed that they are properly placed in the Caelifera, and as such they are phylogenetically closer to grasshoppers than they were to Mole Crickets. 


The swollen hind femora enclose the muscles that allow the "crickets" to make their incredible jumps.

Literature
John, B., Rentz, DCF. 1987 The chromosomes of four endemic Australian fossorial orthopterans: A study in convergence and homology. Bulletin of the Sugadaira Montane Research Center. 8: 205-216.

Rentz, DCF. 1996. Grasshopper Country: The abundant orthopteroid insects of Australia. University of New South Wales Press. Pp. 1-284.

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