Mealworms are the larval 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 pet food for captive reptiles, fish, and birds. They are also provided to wild birds in bird feeders, particularly during the nesting season. Mealworms are useful for their high protein content. They are also used as fishing bait.
They are commercially available in bulk and are sold in containers of bran or oatmeal. 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.
Tenebrio molitor is also used for biological research. Its relatively large size, ease of rearing and handling, and status as a non-model organism make it useful in proof of concept studies in the fields of basic biology, biochemistry, evolution, immunology and physiology.
The mealworm beetle breeds prolifically. Mating is a three step process, the male chasing the female, mounting her and inserting his aedeagus, and injecting a sperm packet. Within a few days the female burrows into soft ground and lays about 500 eggs.
After four to 19 days the eggs hatch. Many predators target the eggs, including reptiles.
During the larval stage, the mealworm feeds on vegetation and dead insects and periodically molts. A molting episode occurs between each larval stage, or instar. The larva of this species has 9 to 20 instars. After the final one it becomes a pupa. The new pupa is whitish, and it turns brown over time. After 3 to 30 days, depending on environmental conditions such as temperature, it emerges as an adult beetle.
Mealworms are edible for humans. Baked or fried mealworms are marketed as a healthful snack food. They may be easily reared on fresh oats, wheat bran or grain, with sliced potato, carrots, or apple as a moisture source.
Mealworms have been incorporated into tequila-flavored novelty candies. Mealworms are not traditionally served in tequila, and the "tequila worm" in certain mezcals is usually the larva of the moth Hypopta agavis.
- Finke, M. and D. Winn. (2004). Insects and related anthropods: A nutritional primer for rehabilitators. Journal of Wildlife Rehabilitation 14-17.
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