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COLEOPTERA, Drilidae -- <Images> & <Juveniles> Description The larvae of Drilidae feed almost entirely on snails. Some species show a remarkable sexual
dimorphism, the males being winged and females apterous and larviform
(Clausen 1940/62). Drilidae oviposit in large masses
in shallow burrows in the soil.
Females are able to produce 300-500 eggs, and sometimes the entire
quota is laid in a single day. There
is a large range in the exceptionally long periods of incubation recorded for
the different species, varying from 6 weeks to 3 months. First instar larvae are similar in appearance to the larvae of
other Coleoptera. They are very
active in their search for their snail prey.
When a snail is located, the anal sucker takes a firm hold on the
shell. The prey is then taken to some
sheltered place, after which the larva enters the shell. The snail's operculum often proves to be a
difficult barrier for the larvae.
Feeding is gradual as compared with lampyrid larvae on the same hosts,
and the snail may not die for many days after the larva has entered the
shell. There do not seem to be any
digestive juices or toxic fluids introduced into the snail's body during this
early feeding. The mature larva is
greatly distorted and twisted, due to confinement in a spiral cavity. Drilus
flavescens Rossi appears to have a
distinctive resting stage, induced by adverse conditions such as food
shortage and adverse weather, which is comparable to the coarctate stage of
Meloidae (Crawshay 1903). The
integument of this stage is thin, nearly white, and largely bare, and the
head and body appendages are rudimentary.
They return to the active feeding stage when favorable conditions
prevail. Pupation is within the
snail's shell. The life cycle from egg to adult takes 3-4 years; during which
time 2-4 snails may be consumed each season.
The larva molts after completion of feeding on each host and
immediately before it abandons the shell.
Adult beetles appear in late spring and early summer (Clausen
1940/62). Early accounts of the life history
and behavior of D. mauritanicus Lucas and Malacogaster passerinii Bass were given by Cross (1926, 1930). =
= = = = = = = = = = = = = = References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Barker,
J. F. 1969. Notes on the life cycle and behaviour of the drilid beetle Selasia
unicolor (Guérin). Proceedings of the Royal Entomological Society of
London (A) 44: 169–172. Bocak, L., M. A. Branham & R.
Kundrata. 2010.
4.9. Drilidae Blanchard, 1845. Pp. 104-110 in: Leschen, R.A.B.; Beutel, R.G.; Lawrence, J.F. (volume eds.) Coleoptera, beetles. Volume
2: Morphology and systematics (Elateroidea, Bostrichiformia, Cucujiformia partim). In: Kristensen,
N.P. & Beutel, R.G.
(eds.) Handbook
of zoology. A natural history of the phyla of the animal kingdom. Volume IV. Arthropoda: Insecta. Part 38. Berlin, New York: Walter de Gruyter. ISBN
3110190753 ISBN 9783110190755 Böving, A.
G. and Craighead, F. C. 1931. An
illustrated synopsis of the principal larval forms of the order Coleoptera.
Entomologica Americana (New Series) 1: 1–351, 125 pls. Lawrence, J. F. 1991.
Drilidae (Cantharoidea). P. 424 in Stehr, F. W. (ed.), Immature Insects. Vol.
II. Kendall Hunt: Dubuque, Iowa. Lobl, I. & A. Smetana (eds). 2007. Catalogue of Palearctic Coleoptera. Vol. 4:
Elateroidea, Derodontoidea, Bostrichoidea, Lymexyloidea, Cleroidea and
Cucujoidea. Apollo Books, Stenstrup, Denmark ISBN 87-88757-67-6, p. 209 |