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.
Evans, M. G. E. 1965. Proc. Royal Ent. Soc. London 40: 61-6.
Willis, H. L. 1968. J. Kansas Ent. Soc. 41: 303-17.