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The Stages of Development in Mealworms

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Mealworms are the larval stage of darkling Tenebrio beetles. Mealworms are scavengers who feed on decomposing plant or animal material. They consume grains and seedlings, too. Mealworms are prey of many animals such as birds, rodents, spiders and lizards. The mealworm metamorphosizes into a darkling Tenebrio beetle.


The first stage of growth of mealworms occurs when the female darkling Tenebrio beetle lays between 270 to 500 eggs. The eggs are hardly visible to the naked eye, oval, sticky and white. It takes a period of four to 19 days for the eggs to hatch into larvae. In favorable conditions such as warm and dry, eggs normally hatch after a period of one week.


The larval stage occurs for a period of 90 to 114 days after hatching. Mealworm larvae are normally light brown or creamy in color but darken as they approach the pupal stage. In the larval stage, mealworms are hunted by other lizards, spiders, frogs, rodents and other predators. At this stage, mealworms feed on a variety of foods, storing up energy for the next stage. As they grow, the larvae shed their exoskeletons -- molt -- between nine and 20 times before they become pupae. During the last molt, the larvae normally curl up, marking the beginning of the pupal stage.


The pupal stage lasts for a period of two to three weeks under favorable conditions, but it may extend up to nine months during winter. During this period, mealworms remain inactive, feeding little and just crawling around. The energy stored in the larval stage serves in the development of complex body structures, transforming the creatures into adults. If you are raising mealworms at home or in school, you can skip the pupal stage by refrigerating the mealworms.


Mealworms normally emerge as adults -- darkling Tenebrio beetle -- after pupating. Initially, the adults are white with black wings, but they soon change to all-black. These beetles are able to lay eggs within two weeks of adulthood. The beetles live for a few more months after maturity. The general life span of mealworms is about 1 year. Mealworms can be found in rotten logs or underneath rocks; they generally prefer warm and dark environments as their habitats. They're found in grocery stores and warehouses that store grains. Just like their larvae, these beetles feed on decaying material, grains and seedlings.