Bug Category: Pantry Pests

Sawtoothed Grain Beetle


The sawtoothed grain beetle is a widely distributed species commonly found in stored grain. It is often confused with a closely related species, the less common merchant grain beetle.


The sawtoothed grain beetle lays its eggs loosely on foodstuffs at the rate of 6–10 per day, with total being 370 per female. The larvae are to be found within the mass of the foodstuff in the top centimetre or two. Damaged cereal is entered through broken kernels, and the larvae feed on the germ, causing damage by reducing the percentage of grains which will germinate.


The simplest and most effective control measure is to locate the source of infestation and quickly get rid of it. Use a flashlight or other light source to examine all food storage areas and food products carefully. Dispose of heavily infested foods in wrapped, heavy plastic bags or in sealed containers for garbage disposal service, or bury deep in the soil if permitted, practical, and regulations allow. If you detect infestations early, disposal alone may solve the problem.

The use of insecticides is discouraged around food materials. Insecticides are supplementary to sanitation and proper storage. Household insecticides have no effect on insects within food packages.

Mealworm Beetle


Mealworms are the larva form of the mealworm beetle, Tenebrio molitor, a species of darkling beetle. Like all holometabolic insects, they go through four life-stages: egg, larva, pupa, and adult. Larvae typically measure about 2.5 cm or more, whereas adults are generally between 1.25 and 1.8 cm in length.


Mealworms are typically used as a food source for reptile and avian pets. They are also provided to wild birds in bird feeders, particularly during the nesting season when birds are raising their young and appreciate a ready food supply. Mealworms are high in protein, which makes them especially useful as a food source. They are also commonly used for fishing bait.
They can be purchased at most pet stores and bait shops. They are also available via mail order and via internet suppliers (by the thousand). Mealworms are typically sold in a container with bran or oatmeal for food.

When rearing mealworms, commercial growers incorporate a juvenile hormone into the feeding process to keep the mealworm in the larval stage and achieve an abnormal length of 2 cm or greater.


Mealworm beetles (darkling beetles) are prolific breeders. Mating is a three step process: 1) The male gives chase until the female relents. 2) The male then mounts the female and curls his genitals (aedeagus) underneath himself and inserts it into her genital tract. 3) The male then injects a packet of semen into the female. Dependent on incubation temperature, just days after mating the female will burrow into soft ground and lays about 500 eggs.

After 1 week the eggs hatch and larvae emerge (mealworms).

Larve Stage

During the larva stage, mealworms will undergo repeated molting between bouts of eating various vegetation or dead insects. This takes place 10–14 times (instars) as it gets too big for its current exoskeleton. During its last molt, it loses its carapace before curling into its pupal form.

Pupa Stage

The mealworm remains in its pupal stage from 3 days to around 30 days (dependent on incubation temperature and overwintering). The pupa starts off a creamy white color and changes slowly to brown during its pupation stage.

Larder Beetle


Large numbers of small, brown, hairy larder beetle larvae often appear suddenly in the spring, alarming homeowners. Larder beetles attack all products of animal origin, including feathers, horn, skins, ham, bacon, dried beef, hides, hair, beeswax, and similar products. In recent years, they have been found in increasing numbers in dry pet foods containing a mixture of cereal and animal products. Adult beetles are occasionally found on flowers, where they feed on pollen.


The adult is a small, black beetle, 6 to 9 mm (1/4 to 1/3 inch) in length, with a pale, yellowish-brown to reddish band across the anterior half of its wing covers. On this band are six black dots, three on each side of the middle line. The larder beetle larva tapers towards both ends and may reach 16 mm (5/8 inch) when fully grown. The larva has a brown, hairy body, white undersurface, and two short, curved stiff spines on the top of the last abdominal segment.

Life Cycle

Larder beetles usually enter homes in May and June seeking food on which to deposit their eggs. If no food can be found, the beetles deposit their eggs in cracks and crevices about the pantry and other areas where the larvae will be able to find food. Larder beetles frequently follow heavy cluster fly infestations, as the beetles readily feed and lay their eggs on the fly carcasses. Large numbers of nearly full-grown larder beetle larvae consume the last of the cluster flies or other food upon hatching, work their way out of the partitions in the house, and wander about, ending up in sinks, tubs, bureaus, beds, etc. This invasion can last from two to four weeks. Similar problems can result from mice, birds or squirrels nesting in the walls. Under favorable conditions, there may be more than one generation per year. The larder beetle can complete its life cycle in 40 to 50 days.

Pest Control

Controlling cluster flies is often helpful in reducing larder beetle infestations. Seal baseboards and other possible openings into attics and partitions. Keep smoked meats in cold storage. Farm-cured meats should be carefully wrapped in cloth or paper immediately after smoking. Store all meat products in sealed containers. Catch the beetles and larvae by hand and destroy. Use cheese as a bait to trap the beetles. Infestations in dry pet food may be controlled by heating to 135 degrees F for 30 to 45 minutes or by freezing for several days. Microwaving should be equally effective.

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