Tuesday, 5 April 2011

A Few Interesting Beetles

For the last month or so this Ground Beetle, Gnathaphanus phillippensis, has been everywhere. We find it in the rainforest as in the Mareeba-Atherton area as well. It is attracted to lights and has been seen in numbers in service stations, around street lights, in shopping centre foyers etc. It is an Australian beetle in the family Carabidae, the Ground Beetles, and probably is responding to the peculiar weather conditions we are experiencing this wet season.
Gnathaphanus phillippensis on the light sheet. The beetles aggregate and remain together for a time.

Ground Beetles are usually predaceous and many have been used to control other insects. Whether the abundance of this beetles will have any effect on the local fauna is yet to be seen.

A nitidulid that lives in palm frond sheaths
Whenever a palm frond falls, and that is often in the wet season, a look on the inside of the sheath usually reveals numbers of this colourful little beetle. It looks like a Rove Beetle but my colleague Tom Weir tells me it is a Sap Beetle, probably the genus Brachypeplus, family Nitidulidae.
Sap Beetles, family Nitidulidae, are small and usually not very colourful. Some species feed on pollen, fungi, vegetable matter; others live in bee's nests. I usually see them on decaying fruit in the bird feeder. Some nitidulids can cause considerable damage to stored dried fruit. But this species seems to live only under the palm sheathes where it is moist. As the fronds dry out, the beetles leave.

A Passalid Beetle
Passalid beetles are called Bess-bugs or Bess Beetles. About 500 species are known in the family Passalidae. There are 35 species in 9 genera recorded from Australia, (Hangay and Zborowski, 2010).

Bess-bugs have a distinct biology. Most species show parental care for eggs and young. They live in and under decaying wood and move around at night. They are infrequently attracted to lights. We find two species in the rainforests around Kuranda. This large one, 43 mm, and a smaller, more slender species about half that size.

Passalid beetles often carry mites. Some individuals are literally covered with them.

Defensive scratching of a passalid beetle when held in hand. The beetle produces sound by "stridulating". That is, the sound is produced by a rubbing of the wings against the dorsal surface of the abdomen. The larvae can also produce a squeaking sound. Sound is probably important in keeping individuals in contact with one another as well as warding off potential predators.

Hangay, G., Zborowski, P. 2010. A Guide to the Beetles of Australia. CSIRO Publishing, Collingwood, Vic., Pp. 1-238.

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