Issue 5, June 2, 2014

Caterpillar Hunter

The large ground beetle Calosoma has been reported in the Bloomington and Joliet areas of the state. This 1.2-inch long beetle is broadly oval with long black legs and antennae. There are species with purple wing covers and others with bright metallic green wing covers that occur in Illinois. The ones being seen currently have green wing covers.

Ground beetle adult.

These beetles are commonly known as fiery searchers or caterpillar hunters. One species, C. sycophanta, was introduced from Europe into the northeastern United States in the early 1900s to control gypsy moth caterpillars. Both the larval and adult stages feed on caterpillars, with the adults climbing through trees in search of caterpillars.

Once introduced, this ground beetle spread much faster than the gypsy moth and has been known to occur in Illinois for decades. It has been blamed partially for the huge reduction in the number of giant silk moths, such as cecropia, promethia, luna, and Polyphemus moths. These moths are generally forest insects, so the loss of large forest expanses to agriculture and other development is also a factor. The small remaining forest remnants likely allow increased predation by birds and parasitic wasps, so the silk moth decline is probably due to several factors.

These adult beetles are attracted to lights at night. They may be noticeable due to their large size and bright colors in the evening around lights or in parking lots and other brightly lit areas in the morning. They are considered to be beneficial insects and should not require control measures. They are large and predaceous beetles, and they will probably bite if they are handled. (Phil Nixon)

Phil Nixon

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