Mealworms are popular in biology labs for observations of insect metamorphosis: egg, larva, pupa and adult. Mealworms are not worms as their name suggests but the larvae stage of the Tenebrio beetle. This larval stage lasts a few months, the pupa stage then lasts a few weeks before finally emerging as beetles.
Mealworms are odourless and very easy to keep, simply feed oatmeal/bran and, after metamorphosis, slices of apple. House in a clean plastic container with ventilation holes to avoid mildew.
Ideal temperature 15-25¡C, to speed up the life cycle house at 25-30¡C, and to induce dormancy (for example over school holidays) store in the fridge (take care to avoid condensation). The entire lifecycle should take around 12 months dependant upon temperature.