- Care of Ground Beetles
(Coleoptera Carabidae)
By Liz Asteraki and Gordon Ramel
Introduction
Ground beetles (Carabidae) are one of the largest and most successful
families of beetles in the world. There are more than 40,000
species of Ground Beetles in the world most of which are found
in the tropics, Britain has around 350 species. Not only they
are fascinating and easy to find, but they are relatively easy
to keep in captivity and will readily reproduce, so that you
can study all of the life cycle. The largest species in Britain
is Carabus intricatus, which is very rare and can only be found
in a couple of places on Dartmoor.
Housing
Plastic storage boxes or washing-up bowls make suitable cages
to keep the beetles in. A layer of peat (or coir compost) or
sand needs to be put in the bottom. This must be kept moist (but
not wet) at all times. A shelter must be provided, this can be
a large stone or up- turned flower pot saucer.
Feeding
Most Ground Beetles are omnivorous and can be fed on a variety
of foods such as fly larvae, small seeds, ant pupae (sold as
ant eggs for fish food), aphids or any other small insects. Some
species however are specialist feeders, i.e. Harpalus rufipes
(the Strawberry Seed Beetle) on seeds, Loricera pilicornis (the
Springtail Beetle) on Collembola and Abax parallelopipedus (ater)
and Cychrus caraboides on slugs and snails. The larvae are generally
carnivorous and always so if the adults are. Most species of
Ground Beetles are cannibalistic. This isn't too much of a problem
if they are kept well fed and not overcrowded, but it may be
a good idea to take out any larvae found and keep these in a
separate container to prevent cannibalism. Abax parallelopipedus
is a species which is not cannibalistic and therefore makes a
very good pet or study animal. It can often be found under rotten
logs in woodlands.
Breeding
Different Ground Beetle species are unofficially classified as
either Spring or Autumn breeders. Spring breeders such as Pterostichus
cupreus over winter as adults while Autumn breeders such as Nebria
brevicollis over winter as larvae.
In general the number of eggs produced depends on nutrition,
environmental factors such as moisture, temperature, and the
age of the beetle. Research indicates that Carabids in the wild
seldom reach their reproductive capacity. As in most predators
egg production is related to food supply. It has been found that
the number of eggs produced is inversely related to body mass
hence large species lay less eggs and that autumn breeders tend
to lay more eggs than spring breeders. Also members of a given
species tend to lay more eggs in disturbed conditions than in
stable ones. In the first year females will lay 5-10 eggs per
female in those species with egg guarding behaviour, but up to
several hundred in those that don't. Eggs are laid all in one
batch, as several batches per season and in some species over
several seasons. Whilst in the second year, in most species,
far fewer or no eggs are produced. Some species lay their eggs
individually on the surface of the soil while others dig holes
and lay their eggs in these before covering them over with soil.
A few species dig nests with chambers and provide brood care
in the form of guarding the eggs and licking them to remove fungal
spores (e.g. Harpalus sp.). The eggs normally take at least five
days to hatch depending on the species and environmental conditions.
Ecology
There are usually 3 larval instars before pupation, however species
of Harpalus and Amara have only 2 larval instars, while other
species, particularly those which are ant or termite symbionts,
have four larval instars. Many species diapause (overwinter hibernation
or summer aestivation). Generally development takes about a year
from being an egg just laid to laying eggs, though it can take
up to 4 years in harsh conditions, i.e. Carabus problematicus
is univoltine up to 800 metres in height but semi-voltine above
that. Other species such as Carabus auronitens are more flexible
and adapts to the prevailing conditions. A pupal chamber is constructed
in the soil. They normally take at least 5 or more days to emerge
from the pupa.
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By gordon@earthlife.net
© Earth-Life Web Productions
Bringing Insects to the World http://www.earthlife.net/insects/
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