Tenlined June Beetle
Colorado Insects of Interest
Tenlined June Beetle
Order: Coleoptera (Beetles)
Family: Scarabaeidae (Scarabs, chafers, May/June beetles, dung beetles)
Identification and Descriptive Features: The adult tenlined June beetle (Figure 1) and the related Polyphylla species are the largest scarab beetles in Colorado, ranging from 22-30 mm in length.
Larvae (Figure 3) are a type of white grub and occur in soil. Compared to other large root feeding white grubs, notably those of the various Phyllophaga species (May/June beetles), they tend to be more tightly curled and stiffer bodied. When full grown they may have the circumference of a 50-cent piece.
Life History and Habits: Adults of this largest Colorado “June bug” usually fly from late June through early August. Males, which have large antennae (Figure 2), are strongly attracted to lights; females, which have substantially smaller antennae, rarely visit lights. Adults of both sexes feed on foliage of various trees and shrubs, but feeding injuries are rarely noticeable.
Although the tenlined June beetle causes little plant injury it is an impressively large, well-marked insect that commonly attracts interest. Furthermore, adults when disturbed can produce an impressive defensive display, hissing loudly by forcefully expelling air from their spiracles. This may also be accompanied by male beetles spreading and fanning out their large clubbed antennae. However, the insects are harmless.
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