Saturday, 23 March 2013

Beetles and Bugs 5: Lesser Goliath Beetle

M.polyphemus male
Now on show in the newly redecorated Bug World is a pair of Lesser Goliath Beetles Chelorrhina polyphemus. The generic name is a bit uncertain – some authorities now put them in Mecynorrhina. A Cetoniine scarab beetle, they originate from Central Africa rainforest and have a very similar life cycle to the Purple Jewel beetles and Hercules beetles I wrote about in earlier posts.

One of the larger scarab beetles, males of this species can reach nearly 8 cm long, with females around 4cm maximum. Aside from size, the males can be distinguished by the ‘antlers’ on the head, which are not as well developed as those of the Rhinoceros beetle but are still useful in fighting with other males, for which reason males need to be kept separately in captivity.

M.polyphemus female
The adults can live many months, and the complete life cycle from egg to death of adult is around a year, although development time for the larvae is shorter at higher temperatures. Eggs are laid in the soil after the female digs down deep into the substrate, and the larvae feed on decomposing wood, decaying leaves, and anything else with some nutrient content. Although not predatory, they could be cannibalistic if hungry and crowded, and to protect themselves they craft a quite solid cocoon incorporating wood particles before pupating.

Although brightly coloured, the metallic green of their wings is quite effective camouflage amongst rainforest foliage. They are not especially secretive, instead relying on their wings (they are good fliers) and well-armoured bodies to protect themselves. Large beetles like these do not have many predators as adults, although the larvae are favoured foods for many terrestrial mammals and reptiles, and their main threat is probably parasitic wasps, many of which are species-specific, although I have not been able to find much information on what parasitizes this particular species.

In captivity they are slightly harder to raise than the smaller species, but are well within the range of a home hobbyist. Basic rearing conditions are a suitably large container of rotting wood and dead leaves maintained at around 25 degrees for the larvae, supplemented with dry dog food to add nutrients. Adults feed on fruit such as banana, but need a covered container to prevent escape.

For more on raising these and other beetles, see here:

(images from wikipedia)

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