File: <drili1.ima.htm> [For educational purposes only] Terminology Glossary <Principal Natural
Enemy Groups > <Citations> |
Immature Stages
of Drilidae
Detailed
information on immature stages of Drilidae is being acquired. However, Clausen noted some detail about
this family, stating that the larvae of subsist 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 generally
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 ] |