Mealworm Beetle

Summary

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.

Uses

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.

Reproduction

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.