A Tale of Two Beetles

Recent interest in the Japanese beetle has prompted questions about two other large "unusual" beetles that are moderately common throughout Iowa. Here are descriptions that should help identify the good, the bad and the ugly.

The dogbane beetle is a bright, shiny iridescent beetle found in fields, landscapes and gardens. This smoothly elongate oval beetle is about 3/8 inch in length and almost as tall as it is wide. The distinguishing characteristic is the color. They appear iridescent blue or metallic blue-green but as you move the beetle in the light other iridescent colors of gold or yellow appear. As the name implies, the dogbane beetle is found on hemp dogbane. They also feed on milkweeds. A few manage to wander away and show up in other locations as well.

The spotted grapevine beetle is a large member of the Junebug family. It resembles a light tan Junebug. It is 1 inch in length and has 6 small black dots on the wing covers. The adults feed on grape foliage but are not a significant pest. The larvae are huge white grubs that live in well-rotted stumps and logs. Adult beetles found on grapevines need only be handpicked and discarded.

Japanese beetles emerge in mid-June through July. They are also similar to Junebugs in general appearance but measure only 3/8 inch long by 1/4 inch wide. The head and thorax are shiny metallic green, and the wing covers are a coppery red. There is a row of five tufts of white hairs on each side of the abdomen that serve as a distinguishing feature.

This article originally appeared in the June 16, 2000 issue, p. 73.


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