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COLEOPTERA, Cicindelidae (Latreille 1804) -- <Images> & <Juveniles> Description & Statistics
Cicindelids are called "tiger beetles" because of the
markings of the elytra in some species and the way in which adults attack
their prey. They are also conspicuous
because of the metallic color of the elytra of many species and their agility
in flight and running. Most species
are terrestrial, some are arboreal and other semi-aquatic. All species are believed to be predaceous
as both adults and larvae, and their food consists of a wide variety of
insects and other small animals. The
adults, because of their greater activity, have a greater variety of food
than larvae, which are dependent on what they find in their comparatively
limited range. Several species are
associated with termite nests, although their exact status is not always
certain. Early biological studies
were performed by Shelford (1909), Hamilton (1925), Balduf (1935) and Clausen
(1940). Terrestrial
cicindelidae inhabit exposed locations such as paths, sandy areas and
roadways. When ovipositing, the
female excavates small cavities, <1/2 in. deep, in soil, and lay single
their ovate and translucent eggs. The
larvae show several morphological modification that suit them for predation
and movement in their burrows. The
head and pronotum are large and heavily sclerotized. The mandibles are very large and powerful,
being bent upward so that they serve for more than just seizing and holding
prey (Clausen 1940). Ventrally, the
head is decidedly convex. The legs
have long sharp claws, which in conjunction with the heavy, forwardly
directed hooks on the dorsum of the 5th abdominal segment and with the
S-shaped body, allow for quick movement in the burrow and also serve to brace
the larva in case of a struggle with a powerful prey. The burrow's depth is dependent on the type of soil in which it
is constructed, and it varies among species and with the age of the
larva. Some species make burrows in
sand that are 1-2 m. deep, although most do not exceed 1/2 m. The burrows are generally perpendicular to
the ground surface. The larva lies
with its head at the entrance of the burrow, the claws and dorsal hooks
embedded in the walls, and strikes out with a very rapid movement when an
insect or other animal of suitable size ranges close. Overwintering is most frequently as larvae, though some species
hibernate as adults at the bottom of the closed burrow. Prior to pupation, the larva closes the
entrance to form a special pupation chamber either at the bottom of the
burrow ar at one side of the main shaft.
In the tropics, the life cycle usually takes one year, while in colder
climates it may be 3-4 years. Arboreal species of Tricondyla and Collyris in Java
differ from those inhabiting soil principally in the location of their
burrows. These are formed instead in
young twigs of plants. The initial
entry hole through the bark and into the pith is made by the parent female
with her ovipositor. This hole is
plugged by the female after the egg is laid.
The burrow is increased in size as the larva develops. Coffee trees are susceptible to injury of
this type, and ants that tend various scale insects, notably Coccus viridis
and Pseudococcus spp. are thought to be the main food of the species
occurring in twig burrows (Clausen 1940/1962). Cicindelidae include about 36 genera and over 2002 species known
as of 1998. They are numerous in the
New World, but are missing from certain areas such as Australia. Diagnostic characters of these "tiger
beetles" include a prognathous head with long, thin sickle-shaped
mandibles; clypeus broad, extending laterally beneath the antennal base; eyes
protruding laterally, rendering the head wider than the pronotum. Their legs are long and thin, and the body
is 10-15 mm. and often vibrantly colored with a metallic hue. All active stages of cicindelids are predators. The larvae reside in tunnels in
hard-packed soil or sand. They hold
themselves in position at the mouths of the tunnels with hooks on the dorsal
side of the 5th abdominal segment.
The hooks also serve to fasten the larvae in their tunnels should
their prey, usually insects, prove difficult to pull down into the
depths. Adults are active and fast
runners. They are found along roads
and paths, the banks of streams and other open places. A few species live in termite nests; other
tropical species are arboreal. A few
species have been transported to other areas for biological pest control with
no reported results. References: Please refer to <biology.ref.htm>, [Additional references
may be found at: MELVYL
Library] Evans, M. G. E. 1965. Proc. Royal Ent.
Soc. London 40: 61-6. Willis, H. L.
1968. J. Kansas Ent. Soc.
41: 303-17. |