The female Saw-toothed grain beetle lays up to 400 eggs, either singly or in small
batches, at a rate of 6-10 per day. These are laid in, or adjacent to, a suitable
food supply and at a temperature of 20-23'C hatch in 8-17 days to give flattened
larvae about 0.9mm long. They are yellowish-white in colour, with brown flecks and
a brown head. Typical of coleopterous larvae, they have a well-developed head, biting
mouthparts and 3 pairs of legs on the thoracic segments. The larvae are active and
feed on damaged grains, so they can be regarded as secondary pests of grain. The
larval stage lasts 47 weeks during which the larvae go through 2-5 moults, attaining
a length of 3mm. They then construct a cell of food particles and other debris in
which to pupate, emerging after 1-3 weeks as adults.
On emergence the adult beetles live for 6-10 months, breeding within a temperature
range of 17.5-40'C. At 20 degC the full life-cycle is completed in 12-15 weeks whilst
at 32-35'C it takes only 20 days.
Saw-toothed grain beetles are potentially important pests of farm-stored grain. They
also infest cereal products, dried fruit, dried meats, oilseeds, nuts, rice and even
In grain, the mere presence of insects may result in its rejection. The germ may
be damaged and when infestations become heavy they cause the grain to heat. This
in turn leads to caking, moulding and even sprouting. Both the quality and weight
of the grain may be reduced. Mailing barley may be rejected because of poor germination,
whilst milling wheat is adversely affected by tainting and discoloration.
The presence of insects in other foodstuffs will render them unpalatable and cause
their rejection. Merchant grain beetles mainly infest oilseeds and dried fruit whilst
Foreign grain beetles attack cereal products and cocoa as well as these commodities.