Mealworm

The mealworm is the larval stage of the darkling beetle Tenebrio molitor, a species native to Europe but now found worldwide due to its long association with stored grain products. Despite the name "worm," it is a true insect larva with a segmented, armored body and six small legs near the head.

Mealworms are best known as a pantry and grain-storage pest as well as a widely cultivated feeder insect for reptiles, birds, and fish. Their hardy constitution and ability to thrive on dry cereal products make them easy to rear in captivity, which has made them one of the most commercially farmed insects on Earth.

In the wild and in storage facilities, mealworms feed on decaying plant material, grains, flour, and other starchy substances, playing a minor decomposer role while also representing an economic concern where they contaminate stored food products.

• Elongated, cylindrical, segmented body with a smooth, shiny, yellowish-brown to tan exoskeleton
• Six short legs clustered near the head end
• Hardened body wall gives a stiffer, more rigid feel than soft caterpillars or maggots
• Length of 20-32 mm at full growth, though younger larvae are much smaller
• Found in dry, dark places such as grain bins, flour bags, and animal feed
• Lookalikes: wireworms (click beetle larvae), which are similarly shaped but usually more slender and found in soil rather than stored grain

Mealworms thrive in dark, undisturbed places with a steady supply of dry organic material, especially stored grains, flour, cereal, bran, and pet food. They are common in granaries, mills, pantries, and animal feed storage areas across temperate regions worldwide, having spread with human grain trade. In the wild, related darkling beetle larvae can also be found under bark, in leaf litter, and in decaying wood.

Mealworms are sluggish, burrowing feeders that spend most of their time tunneling through their food source, avoiding light and open areas. They feed on a broad range of starchy and decaying plant matter, making them efficient scavengers of grain byproducts. In captivity they are prized for their ability to convert food waste into protein efficiently, and in natural settings they contribute to the breakdown of dry organic debris.

Female darkling beetles lay small white eggs in or near a food source, which hatch within one to two weeks. The larval mealworm stage is the longest part of the life cycle, lasting several months to a year depending on temperature and food availability, during which the larva molts many times as it grows. When mature, the mealworm pupates into a pale, immobile pupa for one to three weeks before emerging as an adult darkling beetle, which is shiny black to dark brown. Adults live for a few months and can produce multiple generations per year in warm, food-rich environments.