Illinois Natural History Survey - University of Illinois

Species Spotlight: Green Tiger Beetles

beetle.gif
Green Tiger Beetles (Cincindela sexguttata) in the act of mating.

(photo by Michael Jeffords, INHS Center for Economic Entomology.)

With the sun shining off its iridescent blue-green elytra, the green tiger beetle resembles an emerald lost on a sandy path. A closer inspection usually reveals nothing but sand because the "emerald" has flown several feet down the path. The scenario is repeated until the beetle tires of the "game" and flies off. From early spring until fall, many species of tiger beetles may be found in open sunny habitats--roads, paths, beaches, and mud flats--and always one or two steps ahead of the observer.

Green tiger beetle adults are slender predatory beetles with long legs, large eyes, and thread-like antennae. Like all chewing insects, they have a pair of mandibles. Mandibles in general are powerful grinding jaws that are lined with teeth and work sideways instead of up and down like a human's. The tiger beetle's mandibles are sickle-shaped and very sharp, with several teeth on the inner face. The name tiger beetle refers to its predaceous habits (both adults and larvae eat all kinds of insects) and to the ability of the adults to suddenly pounce on their prey.

During the summer months females will deposit their eggs in sandy soil. The eggs become larvae that are whitish, S-shaped, and grub-like with long curving jaws and large hard heads. The larvae prop themselves up in their vertical burrows with their oddly-shaped heads often plugging the burrow entrance. They wait with open mandibles for a hapless victim, which they seize and take to the bottom of the burrow (sometimes a foot below the surface) to devour at their leisure. On the larva's fifth abdominal segment is a spine that anchors it to the side of the burrow. Thus, if a larva grabs an insect that is too large to overcome, it is anchored to the burrow and will not be pulled out.

Tiger beetle larvae also have enemies. Sometimes the larvae are attacked in their burrows by a small wasp that will sting and paralyze them. The wasp then proceeds to lay its eggs on the larvae and seals the burrows. The young wasps feed on the beetle larvae as they develop.

The tiger beetle sheds its exoskeleton three times in order to grow larger. Prior to each molt the tiger beetle larva must undertake an extra step and enlarge its burrow to accommodate its soon-to-be bulkier self. Pupation takes place in a chamber dug off the main tunnel and the entire life cycle will take up to three years.


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Subject: INHSPUB-2137
Last Modified 3/19/96



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