Thursday, 26 July 2012

The Humble Mole Cricket

Almost every gardener is familiar with Mole Crickets. They have a very distinctive appearance and are encountered when digging is loose soil or in soil that is wet. They are frequently attracted to lights.

Mole crickets are often accorded their own separate family, the Gryllotalpidae. That's where they are placed in the Orthoptera Species File. However, in the bible of Australian cricket taxonomy, they are considered a subfamily of the large cricket family, the Gryllidae.

Australia has a great diversity of Mole Crickets. Most are in one genus, Gryllotalpa. Over 20 species are known. They are distributed across the continent even in the most arid areas where they are concentrated around sinks and watercourses. There are some species that defy the tradition that they are always associated with water. I found a new species at the top of Mt Franklin in the Australian Capital Territory where it was living in leaf litter amongst house-sized boulders.
Mole Cricket species are tough to identify. The calling song of the male is the distinctive feature. Females of some species also produce sounds, probably in defense of their eggs in the chambers of their burrows.
A stylised version of the mole cricket in its chamber. (From the web).

Some species use the chamber as an amplifier and the singing male perches at the entrance and rotates his body 360 degrees as he produces his song. That is why it is often so difficult to locate a singing male. The sound seems to come from everywhere or nowhere! And most species sing only for a few minutes and that is at dusk when visibility is not good. They cease calling a the slightest disturbance. Calling can be initiated in late afternoons when lawns are watered. But this will only last for a few minutes.

The Mole Cricket in the photograph is in the Monanka Species Group based on the combination of the large ocelli (false eyes), the presence of subapical spines on the hind legs. Beyond that it could either be G. monanka Otte and Alexander of G. coarctata Walker. Beyond that,  identification is conjecture as the two species are often found together.

 Highly modified for digging, mole crickets are like little bull dozers as they tunnel thought the soil.
The ocelli are the two white convergent ovoid structures just above the black eyes.

The forelegs are highly modified with trowel-like spines that shift the dirt as the cricket moves through the soil.

Most of the Australian species are in the genus Gryllotalpa but there is a potential problem with an introduced pest, the Changa, Scapteriscus didactylus (Latreille), a South American species that causes damage to a diversity of crops. It was introduced into the Newcastle, NSW region in the early 1980's  apparently in ship's ballast which was used for golf courses in the Maitland and Wallsend area. Tunneling mole crickets do not meet with the approval of golfers! They make the surface of the ground uneven and their tunneling often breaks through causing hills and dales. This cricket is very distinctive. It is much larger than normal Australian mole crickets and has two instead of for "dactyls" (A fancy word for the finger-like claws on the foreleg). (See paper below for details).

Mole cricket biology is in its infancy in Australia. Not much has been done in this respect since the work of Normal B. Tindale in 1928. And this brings us to the larger than life figure of Tindale. He was born in 1900 in Perth. He was influenced into science by his father but during an experiment in his father's photographic lab, Tindale was involved in an explosion and permanently lost the sight of one eye. This did not discourage him. He decided to continue with science and his inspiration was Alfred R. Wallace.

Tindale is claimed by entomologists and anthropologists alike. An inspirational read is his obituary by Philip G. Jones. Tindale's entomological accomplishments are many. He was associated mostly with the South Australian Museum and there is a hall there named in his honour. Aside from detailed work on the taxonomy and biology of Australian Mole Crickets, Tindale was the world's expert on Ghost moths, the  Hepialidae. Not only did he work out the taxonomy of these moths but he studied the intricate habitats of their peculiar larval biology and the odd behaviour of the adults. He was also an ornithologist, geologist and a linguist. During World War II he spent time at the Pentagon decoding and translating Japanese transmissions intercepted by the Allies. He was unable to enroll in the active military because of the loss of sight in his one eye.

But some of Tindale's most notable accomplishments were in the field of Anthroplogy. This began in 1921 with a trip to Groote Eylant where he initiated studies of the aboriginal community. He was associated with Sir Walker Baldwin Spencer who encouraged him to take detailed notes every day. Thus began a wonderful career as noted below in the notes from Jones' obituary.

"Looking back on Tindale's career it is possible to discern half a dozen research paths which he followed, converging and diverging but persisting across several decades until his death. Few specialists would attempt to emulate such a course today; in Tindale's time, as his colleague and friend Joseph Birdsell put it later, it represented the 'proper breadth of interest'. In entomology, his first love, Tindale selected the study of the Hepialidae, one of the most primitive of the moth families; in geology his particular interest became the study of Pleistocene shore-lines and Tindale was to become recognised as one of the 'foremost workers on the Pleistocene geology of Australia' (Daily 1966). In linguistics as in broader anthropological studies his object was to gather sufficient data to scientifically describe variation in Aboriginal culture and society across the country. The same applied to his physical anthropological surveys. More focused studies, such as an investigation of initiation practice, Western Desert art and mythology, or the detailed description of a coastal and riverine society, followed from this survey data. In archaeology, informed by his geological and ecological training, Tindale's object was to establish the broad canvas on which more specific applied or theoretical investigations could be painted. Tindale's field trips became the testing ground for this tumult of ideas and theories against a background of wide reading in each area and constant rapport with colleagues, nationally and internationally."

I met Tindale personally in the 1960's when he visited the California Academy of Sciences. He was living at Palo Alto, just south of San Francisco where the Academy is located. I had no idea at that time that I would ever even visit Australia, let alone establish a career there. Tindale was a personable and encouraging person. I always recall this meeting and was I was privileged to dedicate a widespread southern, Shield-backed Katydid species, Oligodectoides tindalei Rentz, in his honour. Remember he did all this research with only one eye!


Rentz, DCF 1995. The Changa Mole Cricket, Scapteriscus didactylus (Latreille), a New World pest established in Australia. (Orthoptera Gryllotalpidae). Journal of the Australian Entomological Society 34: 303-306.


Piotr Naskrecki said...

I see quite a few parallels between Tindale and E.O. Wilson.

Mr. Smiley said...

Thanks Piotr. He was a very dynamic person. I've seen his early (1931) movies of aboriginal life in central Australia. Very awesome, indeed.

Sir Ward said...

What are the origins of the grass spider? The yellow and brown sac spider came from southern europe. The cob web builder the american house spider originated in south