Appearance (Morphology)
Adult Beetle
* Black with hardened front wings (elytra)
* Antennae arise under ridge near eyes
* Antennae many-segmented, enlarging near tip
* Shape quite variable, from almost parallel-sided to round
* Head visible from top, followed by pronotum and elytra about same width
* Mealworm (larva) averages an inch in length. They have a tough yellowish brown exoskeleton and are cylindrical.

Adult Males and Females
It is difficult to tell the difference between the males and females without a microscope and dissection.

Immatures (different stages)
The larval stage (referred to generally as mealworms) is worm-like and somewhat hardened for burrowing. The egg is white. The pupa is 1/2 to 3/4" long., white initially then darkening just before the beetle emerges. Length of the life cycle is 3-5 months. The larval stage may molt 9-20 times.

The beetles and larvae eat decaying leaves, sticks, grasses and occasionally new plant growth. As general decomposers, they also eat dead insects, feces and stored grains.

Mealworms live in areas surrounded by what they eat under rocks, and logs, in animal burrows and in stored grains. They clean up after plants and animals, and therefore can be found anywhere where "leftovers" occur.

Many predators eat mealworms including rodents, lizards, predatory beetles, spiders, and birds.

When disturbed, some beetles (genus Eleodes) assume a defensive posture in which they stand on their head and release chemicals from a scent gland in the rear that produces noxious odors and turns skin brown. Mealworms prefer darkness and to have their body in contact with an object.

Rather than spend time looking for mealworms in the wild, spend a couple dollars of buy them. Most pet stores and many fish tackle shops sell small and large mealworms. They are sold individually or in amounts of 50, 100 or 200. The large mealworms cost more, but are more lively and easier for students to observe. The large mealworms often are treated with hormones so they will not become adult beetles. The small mealworms will change into adult beetles within a month or two. Mealworms are very easy to rear in the classroom. The larvae grow to 25 mm before pupating. After pupating, the adults emerge in two to three weeks. In seven to ten days, the females may lay eggs. In about fourteen days, the eggs hatch and the larvae begin to eat and develop.

Mealworms will not bite. Dead mealworms are stiff and dark brown and should be removed from the container. Provide plenty of room for the large mealworms since they will eat each other in a constrained container. Small mealworms can be stored in a refrigerator door for several weeks to delay pupation or to extend their life. .

How do darkling beetles defend themselves?
As we mentioned above, many darkling beetles have a very interesting defense mechanism. If disturbed, they assume a head down and tail up position, and if handled roughly, they emit a dark-colored, foul-smelling fluid. This behavior is enough to discourage all but the most determined predators. The fluid washes off easily with water in case of contact with your hands. Coyotes, foxes, hawks, snakes, ravens, and crows often eat darkling beetles. The larger species have no other insect predator as adults.

Some species of Darkling ground beetles lay their eggs in ant nests. Upon hatching, the larvae emit pleasing odors that fool the ants, while the darkling larvae busily eat the ants' larvae!

Where do darkling beetles go in winter?
Most species of darkling beetles are active above ground from spring to late fall. With the onset of winter weather, some species seek shelter below ground in burrows of other animals and remain there until warmer weather returns in the spring. Other species of darkling beetles do not live through the winter as adults. They lay eggs in the soil during warm weather and die with the onset of freezing. Their eggs hatch into larvae when warm weather returns. These larvae live in the soil for up to two years before the adults emerge to eat and reproduce.