Bumble flower beetles are oval in shape and range in size from 12-15 mm in length.  Yellowish-brown to a dark reddish brown in color, dark spots pattern their bodies which are also covered with yellowish-brown hairs.  It is common to hear an audible buzzing sound from adults in flight.  Most commonly found in eastern Colorado, overwintering is done in the adult stage by burrowing into the soil.  Adults emerge in the spring, after mating females seek moist organic matter in which to lay her eggs.  Upon hatching, the C-shaped grubs begin feeding almost exclusively on the organic materials around them.  Once full grown, the larvae create chambers in the earth in which they will pupate.  Newly emerging adults appear a few weeks later and can be seen from mid-summer until fall.  Only a single generation is produced each year.

Bumble Flower Beetle Grub

Bumble Flower Beetle Grub

Adult bumble flower beetles feed on a variety of sweet or fermenting liquids including the bacterial ooze produced by infections in many trees.  Bumble flower beetles are not involved with the transmission of the underlying plant diseases.  They may also be attracted to ripening corn and some fruits like apples and peaches.  Adults also feed on the pollen and nectar of sunflowers, strawflowers, thistles and daylilies.  Large masses of bumble flower beetles may be seen on tree trunks, branches and flower stems late in the summer as they feed.  Colder weather causes them to move into the soil for overwintering.