side Kernels
Primary insect pests of stored grain develop within
grain kernels and can destroy whole, sound grain.
Adults deposit eggs on or in whole kernels, and larvae
develop inside the kernels. Feeding by these insects
causes grain to be classified as sample grade.
The primary pests found in stored grain in Illinois
are the weevils—rice weevil, maize weevil, and granary
weevil. The grain weevils are small (between 1
⁄ 16
and 1
⁄8 inch long) but recognizable as a group because
the head projects forward as a prolonged snout. Another
primary pest found in wheat, but only rarely
in corn, is the lesser grain borer. The adult’s head
projects downward, not forward, and does not bear a
snout. These insects may be found in any portion of
the grain mass within a bin.
The Angoumois grain moth lays its eggs on grain
kernels, and the larvae bore into the kernels and feed
there. Although this insect may attack grain before
harvest, most of the damage occurs in stored grain.
Infestations in storage are limited to the surface of the
grain mass. However, this insect only infrequently infests
stored grains in Illinois.
Beetles That Develop and Feed
Outside Grain Kernels
Most insects commonly collected in stored grain in
Illinois are beetles that range in size from 1
⁄ 16 inch to
more than 1
⁄2 inch long. Adults of most species are
red–brown to black, and their forewings are hardened
to form a “shell” over the body. Larvae of common
species are cylindrical and cream colored; some bear
fine hairs. Species frequently collected in Illinois grain
bins include the sawtoothed grain beetle, flat grain
beetle, rusty grain beetle, foreign grain beetle, hairy
fungus beetle, larger black flour beetle, red flour beetle,
and confused flour beetle.
Like the weevils, beetles that feed and develop outside
grain kernels may inhabit any portion of a grain
mass. They feed on bits and fragments of several different
grains; their buildup usually results from an
abundance of broken kernels (fine material) or fungal
growth on moist grain. Their dependence on fines or
fungal growth accounts for the description of these
insects as secondary pests, “bran bugs,” or “fungus
feeders.”
Surface-Feeding Caterpillars
Most caterpillars that feed in stored grain inh