The first thing kids should know about black beetles is most are harmless, and the term covers more than one insect. Black beetle may describe the common black ground beetle, the black carpet beetle, the black water beetle, the black blister beetle, the southern pine beetle, the blister beetle and the black turpentine beetle. These beetles can be approximately the size of a grain of rice to 2 inches long.
Adult black beetles have four sets of wings. The fore wings form a protective shell that covers the abdomen like armour. The fore wings are not flapped when a beetle flies, but they are raised so the beetle can move its hind wings. Beetles are not strong flyers since they are too heavy for their wings and lack dexterity. Black beetles tend to fly only between vegetation.
Friend or Foe
Black beetles are sometimes viewed as a pest, particularly to homeowners who find carpet beetles unsavory. However, like bees and birds, beetles are garden-friendly because they pollinate flowers. Beetles also consume animal waste and dead plant matter, which they convert into soil compost. Although most beetles are harmless, the black blister beetle is a toxic insect. The blister beetle produces a caustic substance called cantharidin. Canthardin can cause blisters on human skin, and can poison livestock if they eat hay infected by blister beetles.
The Life Cycle
The black beetle begins its life as a white egg measuring approximately 2mm long. Several days after it is laid, the egg changes from an oval shape to a circle just before the larva hatches. The larva is approximately 2.5mm long, with a light brown head, greyish body and black hind end. The larva feasts on plants, rotting vegetables and small insects. The pupa stage comes next. The beetle will turn light yellow, then reddish-brownish, just before adulthood. Beetles have one generation per year. They generally lay eggs between January and February.
Adulthood and Threats
Beetles develop a hard shell a few hours after they emerge from the pupa stage, which doesn't do much to protect them from predators. Some of the many predators of black beetles are birds, mice, raccoons, bears, foxes, wildcats, skunks (which prefer the larvae), mice, shrews, rats, frogs and toads.
Black carpet beetles eat animal proteins found in woollen carpets or silk scarves, food droppings, hair and leather. The common black ground beetle feeds on aphids, grubs and maggots, while the blister beetle thrives on plant matter such as alfalfa, wild flowers and weeds. Pine beetles feed on pine trees, often causing damage to entire areas of a forest. Black water beetles feed on decaying vegetation.