Issue 17, October 17, 2011

Cedar Beetle

A number of cedar beetles have been sent in for identification over the past few weeks from the southern half of Illinois. Cedar beetles, also known as cicada parasite beetles, are in the family Rhipiceridae. Generally, they are reported as flying around or crawling on a tree in large numbers.

Cedar beetle adults are large, stocky, dark brown beetles that are about one inch long. They are flattened dorsally with the head pointed downward. The males have short but obvious comb-like antennae. The adult beetles lay their eggs bark cracks which hatch into slender, active larvae called triungulins. These triungulin larvae burrow through the soil seeking out cicada nymphs. Once a cicada nymph is found, the triungulin larva molts into a slow-moving, grub-like larva that grabs onto the cicada nymph and feeds on its hemolymph, its blood.

Cedar Beetle Adults

Mature larvae pupate and emerge as adults in years when periodical cicadas emerge. We are seeing these beetles in the same areas of Illinois where periodical cicadas emerged this year. They were also numerous last year in southern Illinois. Those were likely beetles that matured a year early, as do some of the periodical cicadas.

As cicada nymphs feed on tree roots, it is natural for their parasites to emerge from the soil under tree canopies. It is also where the adults would lay their eggs so that the larvae could seek out cicada nymphs feeding on the roots.

These beetles are interesting due to their habits and life style. Although large and locally numerous, they are not considered to be pests. In fact, some could argue that any insect that reduces the number of cicadas should be considered to be beneficial. (Phil Nixon)

Phil Nixon

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