Coleoptera: Scarabaeidae: Cotinus mutabilis (Gory & Percheron, 1833) (Green Fruit Beetle)

This scarab occurs only sporadically in the basin, although it may be aboundant in our few remaining fruit orchards or in suburban neighborhoods where backyard fruit trees grow. Originally native to Arizona and New Mexico, it gradually spread westward and became noticeable in the Los Angeles area after the 1960s. The adults feed on a wide variety of fruits, including cactus fruit (which may be its wild host), peaches, apricots, nectarines, and grapes.

Photograph by C. Hogue

The beetle is easily recognized by its large size (its length 3/4 to 1 1/8 in., or 20 to 30 mm) and the general velvety olive-green color of the top of the thorax and wing covers (the altter are marked with contrasting dull brownish-orange marginal bands). The underside of the body is shiny metallic green. It is equipped with a short shovel-like horn on the front of the head for enlarging openings in the skin of fruit. On hot days in August and September, individuals may be seen in flight, buzzing clumsily in circles or zigzagging near the ground.

The adults are active from alte summer to early fall and, during this period, lay their eggs in compost piles and other accumulations of decomposing plant litter. The alrvae are fairly large (2 in., or 50 mm long) and C-shaped; the body is pale translucent white, and the head is dark brown. The first two molts are completed in the fall, the third in the following spring. Larvae Move forward on their backs with an undulating motion of the entire body. They obtain purchase on the substratum with transverse rows of stiff short stout bristles on the back of the thorax. Because of this peculiar manner of locomotion, they are known as "crawly-backs."

Larvae tunnel into compost piles and soil under accumulations of decomposing plant litter, emerging periodically to feed on surface material. In local populations, development also commonly occurs beneath manure piles and haystacks in hourse stables (the larvae do no affect turf).

© 1993 Insects of the Los Angeles Basin