Friday, June 27, 2014

JUNE SPEAKER’S REPORT - 'Dung Down Under – Australia’s Fascinating Dung Beetles', by Dr Geoff Monteith, Queensland Museum

The Scarabaeidae family, in the order Coleoptera, includes dung beetles, and the identifying feature of the family is their antennae which are branched into flat plates at the tips. The plates are covered with smelling organs and can fold together when not in use. Some dung beetles are nocturnal and nearly all are winged. Some are “perchers” – they sit on low foliage with their antennae extended, waiting for the scent of dung on the air, whereupon they fly to the source. Others are “prehensile”, clinging by means of their hooked toes to the back- sides of macropods in particular, and falling to the ground on the droppings as they emerge (there are six species of these in Australia). Dung beetles use dung as food for their larvae, as most adults cannot chew – they suck the juice from the dung.

Dung beetles are divided into “buriers” and “ball rollers”.  • The buriers dig chambers up to one metre below ground but usually about eight centimetres, and fill them with balls of dung in which they make hollows to lay their eggs. Geoff showed photographs of the female beetles sitting down like potters, hollowing out the balls, then curling around to lay an egg, and finally filling in the gap with dung. The chambers are then sealed off, the eggs hatch, and the larvae feed on the dung balls until they pupate, hatch and then come to the surface. Onthophagus, a huge genus has 2000 plus members, of which 250 are found in Australia. Many in this genus have horns on their heads, which they use to fight each other and to defend their nests.

• The ball rollers break off small pieces of dung and roll them into balls which they then move up to 10 metres away to bury just below the surface. Ball rollers usually have curved legs to help them form the dung into balls. They never have horns. There are about 170 species of ball rollers in Australia.

Several species of African dung beetles were introduced into Australia some years ago to deal with the moister, semi-liquid cattle dung, as Australian native beetles are adapted to use the dryer macropod poo. One imported species doesn’t bury the balls, but builds a pile of them against a rock or a post. The larvae don’t defecate inside the ball until they are ready to pupate. They then defecate either inside the ball or make a small hole and defecate on the outer surface - the faeces is then spread evenly and hardens to form a protective covering.

Dung beetles are great for the environment for the following reasons. • They put nutrients into the soil. • They dispose of dung and thus stops flies breeding. • They prevent parasite transmission in dung. • They aerate the soil. • They bring subsoil to the surface.

Dung lying about in pastures encourages flies, and stock do not like to graze near it. Predators are cane toads, which wait at cow pats for their dinner to arrive, and ibis – cow pats with many beak holes can often be seen.

Demarziella genus – “cuckoo” dung beetles, lay their eggs in the dung balls of others. Some species use fungi as others use dung. They burrow up through the stem of a mushroom, collect armfuls of the nutritious spore- bearing gills and take it back down through the stem to their chambers. This may aid spore dispersal. Fungi and dung are both used in dung beetle traps.

The amazing habits of Cephalodesmius species were discovered in Australia about 25 years ago. They are found from Maryborough to Sydney, and in some places there are up to 50,000 per hectare in S.E. Qld rain- forests. They make and use their own artificial “dung”. The male collects small fallen leaves and fruit and takes them to the female in the nest chamber below ground. She mashes the material up and builds a kind of “compost heap” in the damp chamber. She adds her own faeces into it and after about a month it has decayed and is ready to use. She then breaks off small portions and hollows them into small balls and lays an egg in each, one a day for eight days. The eggs hatch, and the larvae start eating the material inside the balls. The male brings more leaves, which the female adds to the compost heap and continues to harvest decayed material to plaster on the outside of the larval balls. They grow as large as a macadamia nut, and the larvae “squeak” to their mother for more food by scraping their tails against their throats. When the larvae are ready to pupate, they excrete faeces onto the outside of the ball through a hole, which the female smears on the outside to seal it. The female and male then die, the larvae eventually hatching out and coming to the surface. This is called “progressive provisioning”, and is rare in insects and considered very advanced. Only two species do this, the Cephalodesmius species above, and Canthonosoma castelnaui which is wingless and common in Western Queensland and in vine scrub, continuing to feed its young on fresh dung happening to fall close to its nest.

These beetles are important as they recycle leaf litter. School experiments with corn plants prove that dung beetles promote growth by burying the dung and making it available to the roots of plants. The beetles are specialised to soil type, vegetation and altitude rather than to particular types of animal droppings. The largest species of Australian dung beetle is up to three centimetres long.

Aulacopris maximus uses bat guano, and is found inside hollow trees where bats sleep. It is found at Mt Glorious and Lamington NP, and was seen, unusually, on the trunks of trees at night. A hollow tree was cut down, and the beetles with their dung balls discovered inside. • Onthophagus tweedensis is a common open forest species in Brisbane – it is horned, and a beautiful dark green. • Onthophagus dandalu uses dog droppings. • Amphistomus storeyi is rare, wingless, and there are several communities found around Brisbane only. • Onthophagus gazella is imported, and is often attracted to lights at night. • Sisyphus spinipes makes piles of dung balls and is seen abroad in hot sun.

Dung beetles are a good indicator in biodiversity surveys, as they are sensitive to environmental factors and are linked to vertebrate fauna. They are easy to trap using pitfall traps baited with dung or rotten fungi. There are many parallel global studies, and lots of information available and they are comparatively easy to identify. The Qld Museum has thousands of specimens, and there are 95,000 in an Australia-wide data base. In disturbed areas the larger species disappear, but smaller species proliferate.

Report by Glenda Walter

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