File: <carab1..ima.htm> [For educational purposes only] Terminology Glossary <Principal Natural
Enemy Groups > <Citations> |
Immature Stages
of Carabidae
Carabids are largely nocturnal and
terrestrial, although a number of species are arboreal. Most species are predaceous as adults and
larvae on a variety of hosts, mostly insects, but some species also attack
snails and earthworms. Several
species are associated with ants and termites, and a few species are
questionably phytophagous and others at times utilize plant food in addition
to the normal insect diet (Clausen 1940/1962). Entomophagous species more frequently attack the larvae and
naked pupae of Lepidoptera than the immature stages of other insects. Several species are obligatory, primary,
solitary ectoparasitoids, and a few species feed on seeds. Species that have developed obligatory
external parasitism show a degeneration in the larval instars following the
first molt. Most species are generally
beneficial, and have been considered vital in natural control of other
insects, such as certain pestiferous Diptera (Legner et al. 1980). Nevertheless, they have not been used
extensively in biological control.
European species of the genus Calosoma
have been introduced into North America as predators of the gypsy moth and
brown-tailed moth. As implied by the common name,
"ground beetles," adults are mainly ground dwellers, and they carry
on their activities principally at night.
They may be found in various protected locations, such as under
debris, loose bark of trees and stones, or they may inhabit distinct
burrows. Many others, such as the
genera Lebia and Calosoma are to some extent
arboreal, where they may be frequently found attacking foliage-feeding
insects in trees. Please CLICK on picture to view details: In a few species the newly hatched
larva does not feed for several days after hatching, because its nutrition is
provided by yolk derived from the egg, which is contained in the digestive
tract. Preoral digestion occurs among
some larvae, as is found also among adults, whereas others ingest tissues
directly. The injection of an
intestinal secretion associated with preoral digestion has a paralyzing
effect on the prey, which is important when the prey is large. The amount of food consumed by a larva is
often large compared with its size.
Burgess (1911, 1917) and Burgess and Collis (1915), studying C. sycophanta, found that each larva consumed an average of
41 6th instar gypsy moth caterpillars during its feeding period, covering ca.
14 days. Pairs of adults were found
to destroy 100-460 6th instar larvae between the time of emergence of the
beetles in springtime and the completion of feeding in midsummer. Regardless of where they feed,
Carabidae pupae in cells in the soil, often at a great depth. Therefore, C. sycophanta
under normal field conditions forms its pupal chamber 10-12.5 cm. beneath the
surface, but sometimes it penetrates deeper.
This ensures a considerable degree of temperature and humidity
uniformity, which is essential for pupae not tolerant of a wide range of
these conditions. When a species is
found to pupate above the ground, it is parasitic, such as Brachinus, which pupates in the
pupal cell of its host. The parasitic mode of development
has been found in several carabid genera that are widely separated
taxonomically. This relationship with
the host was first recorded by Wickham (1894) for Brachinus janthinipennis
Dej. and later also found by Dimmock & Knab (1904). The larvae occur in the pupal cells of Dineutes assimilis Aubé and show modifications in form, such as a
reduction of the legs to a nonfunctional state, which is typical for the
parasitic life style. A detailed
account of parasitic development was given by Silvestri (1904) for Lebia scapularis Fourc.
Adult beetles feed on all immature stages of the elm leaf-beetle, Galerucella luteola Mull, while larvae are
restricted to attacking pupae. The
1st instar larva does not differ much from others of the family in being
elongate, with 13 body segments, each of which bears sclerotized plates, and
the legs are long and well-developed.
There are 4-jointed caudal cerci.
After finding the host pupae in the soil, the young larva feeds
voraciously through a large puncture which it makes in the integument and in
which the head is embedded. After the
first molt, a grublike form is assumed in which the segmental plates and the
caudal cerci are lacking, and the legs are reduced to short conical processes
(see Clausen, 1940 for diagrams).
This is followed by the prepupal and pupal stages, in both of which
the meso and metathoracic segments are very much produced laterally. Before the larvae finish feeding, they
spin a lemon-yellow or brown cocoon, which is composed of a mass of
interwoven strands cemented together.
While spinning, the remains of the host pupa may be drawn into the
cocoon and enclosed within it. There
are two generations annually, and overwintering is in the adult stage in
sheltered areas. Salt (1928) observed the behavior
of Pelecium sulcatum Guer., one of an
aberrant genus of Carabidae. Several
larvae were found on various hosts, including beetle pupae and
millepedes. Development was quick and
apparently was completed on an individual host, so that in its essential
aspects the mode of life was identical to Lebia,
though no distinctive 2nd instar larva as found and no cocoon was made. Arsinoë grandis
Per. seems to represent a transitional phase between predation and parasitism
(Blair 1927). Larvae attack those of
the lichen-feeding tenebrionid, Catamerus
revoili Fairm., in
Nyasaland. Several larvae of the
latter were found to bear those of Arsinoë
attached by the mandibles to the abdominal dorsum. Feeding occurred in this position until the host died, after
which the larva released its hold and searched for another host. Younger larvae may feed for as long as 2
weeks before causing the host's death, while later instars do so in 1-2
days. They pupate in the soil, and
the duration of larval life was thought to be rather long, for some
individuals that were collected did not enter the soil for pupation until
several months later. This indicates
that a number of host individuals are required during the feeding period. Generally it may be concluded that
carabid eggs are laid in the immediate vicinity of the hosts on which the
larvae fed, though not closely associated therewith. The behavior of parasitic species in this
regard does not differ much from that of predaceous species. Most species lay their eggs singly in
small holes in soil with the ovipositor.
Pterostichus multipunctatus Dej. is known to
place a cluster of eggs in the soil chamber and then to guard it during
incubation and for a while after hatching (Clausen 1940/1962). Several species of Galerita, Chlaenius and Brachinus
lay the eggs singly in mud cells which are constructed on plant leaves,
stems, stones, etc. (Riley 1884, King 1919).
The form and composition of the cells, as well as their location, are
distinctive for the genus. Cells of Brachinus are crescentric or
triangular and are located in groups of 3-10 on the undersides of twigs,
plants stems and stones, while those of Galerita
are triangular or purse-shaped, with a finely granular surface, and are
formed on the undersides of smooth leaves.
They are oblong and smoothly convex in C. impunctifrons
Say, and are similarly placed on the undersides of smooth leaves. Those of C. aestivus
Say are found on dead twigs, plants stems, the bark of trees, etc. While forming the cell, the mud pellet is
first collected about the tip of the abdomen of the female beetle, and the
walls are built upon on the stone or other surface in the form of a mold
about the caudal segments. The cover
is formed from the mud carried on the dorsum of such segments (Clausen
1940/1962). Craspedonotus tibialis
Schaum., inhabiting sand duns in Japan, shows an elaborate provision for
laying eggs (Clausen et al. 1927).
The female beetle digs a burrow 25-45 cm. deep, inclined at an angle
of 45°, in embankments, and the eggs are laid singly in small chambers
branching off from the main burrow.
The entire egg-laying period is thought to be passed in the burrow, except
for regular trips in search of food. Life cycles in Carabidae are very
variable, ranging from several months in Lebia
grandis to several
years. Most species probably have an
annual cycle, with winger being passed as adults, although in many species
adult beetles may live for several years.
Calosoma sycophanta adults usually pass
two winters, and sometimes 3-4, though none are known to lay eggs for more
than two seasons (Burgess 1911, 1917).
Males and females both live the same length of time. The adult stage is reached late in the
season, and oviposition does not start until the following spring, with some
individuals not ovipositing until the second season. Studies on a large number of C. sycophanta showed that an average of 128.5 eggs were laid
per female, with a maximum of 653.
However, the average for Carabidae is thought to be much lower than
this (Clausen 1940/1962). References: Please refer to <biology.ref.htm>, [Additional references may
be found at: MELVYL Library ] |