Tuesday, 5 March 2013

Beetles and Bugs 3: Six-Spot Ground Beetle

Currently on show in Bug World is a large and spectacular ground beetle, the Six-Spotted ground Beetle Anthia sexguttata. Unlike the previous species in the series, they are most definitely carnivorous, and have impressive mandibles as armament.

In this respect they follow one of the most ancient beetle lifestyles, as the Carabidae, to which they belong, can be traced back as far as the Triassic and almost all of them are also predators. The various species of Anthia are all flightless as adults, and catch their prey by fast running, aided by their excellent vision. They are large beetles, around 4cm long, and might be considered at risk from being eaten as they are diurnal and very conspicuous when present. As might be guessed from their contrasting colour pattern however, they are well armed themselves. Glands on their abdomen are highly developed and can spray formic acid several centimetres with considerable accuracy. The acid is strong enough to cause temporary, or even permanent, blindness in birds or animals that get caught out, and those that do not suffer serious injury soon learn to leave anything with their colour patter alone.

Warningly coloured insects are often mimicked by harmless ones that are at risk of predation, and A.sexguttata is mimicked by a cockroach living in the same south Inidan scrub forests. The Domino Cockroach Therea petivereana is not the same shape as the beetle, but shares its pattern and if discovered amongst leaf litter by a prospecting shrew or mongoose the pattern is enough to enable it to escape back under cover with ease.

Although maintaining wild caught adult Six-Spotted Beetles in captivity is fairly straightforward, and feeding is also easy (they take all sorts of insects and even have been known to feed on carrion in the wild) breeding is much more difficult. The larvae are apparently obligate predators on ants, seeking out a nearby ant nest after being laid in the soil nearby. Apparently there is usually only one larva per nest, which is probably an indication that larvae are cannibalistic as well. Adults require a deep soil/sand substrate so that they can dig burrows, which in the wild they use to escape the heat of the day.

Much more easy to breed are their mimics. T.pettivereana is one of the more widely kept pet roach species and are easy to care for. They simply need a container with a reasonable depth of dead leaves, rotten wood, and compost (make sure there is no insecticide added to the latter). They take some time to mature though, at least 10 months, and once adult they live perhaps a month or more, so once a colony gets going there will always be a few visible. I have some living in the live substrate I use in my main phasmid tank, and they seem to be doing OK.

(images from wikipedia)

1 comment:

  1. Hello,

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    Volunteer Ethiopia