The group of insects known as beetles, or Coleoptera, is enormous, fully 25 percent of all known animal life on earth. With over 300,000 different species worldwide and 30,000 in North America alone, beetles play an important role in our environment. Black beetles, which can be harmful pests or garden helpers, are a common beetle species and are easily identifiable by their size, coloration and shape.
All beetles have hard exoskeletons and three distinct sections: head, thorax and abdomen. Their legs are shorter at the segment nearer the body and longer farther from the body. They have long antennae with which they smell and sense their environment. Their hard top wings close over their delicate underwings like an oval rubber coin purse. When beetles fly, they open their top wings and use them for balance, flying instead with their underwings.
Three common types of black beetle—the black ground beetle, the black carpet beetle and the black turpentine beetle—live in gardens, homes and fields. All these beetles look similar, but are distinctive in their diet, behavior and habitats and can be easily identified if you know what to look for.
On the whole, the black ground beetle, or Pterostichus melanarius, is beneficial to humans. They are black and shiny, from a half inch to an inch long. Their wings have long length-wise grooves that are easy to spot when their wings are closed. Black ground beetles live in gardens and fields and eat pests harmful to crops, such as caterpillars and aphids. Though most black ground beetles are predatory (meaning they eat other insects), a few will suck the juices of plants. Keep a close eye on your favorite flowers and vegetables if you see these creatures in your garden. You will have to look sharp since black ground beetles are nocturnal and will scurry for cover if you disturb them during the day.
The black carpet beetle, or Attagenus unicolor, thrives on eating wool carpet. It also eats hair, leather, dead insects, your favorite silk scarf and anything else composed of animal protein. It sometimes enters your home in bags of dry dog food. The adult black carpet beetle is about 1/16 of an inch long and dark brown to black in color. But the adult black carpet beetle is not the culprit in your cupboards, since it prefers eating flower pollen outdoors. The carrot-shaped black carpet beetle larva, larger than the adult, golden brown in color with a reddish-brown curly “ tail,” are the voracious kitchen, closet or carpet raiders. These “eating machines” can live up to two years in your home before they become adults.
At 3/8 of an inch long, the black turpentine beetle, or Dendroctonus terebrans, is shaped like a barrel and is black or dark brown. This beetle is beneficial as well as harmful. It culls the weakest members of a pine forest by boring holes into the bark of pines with root-rot, fire damage or other natural or man-made injury and makes tunnels throughout the tree to lay its eggs. When the eggs hatch, the young black turpentine beetles eat the soft wood inside the tree. These beetles will also eat newly cut stumps, but can spread to healthy pine trees as well. You can recognize the work of the black turpentine beetle by the fine dust cast off by bore holes and, in healthy trees, the evidence of sap flowing outward to the exterior bark, a phenomenon called “pitch tubes.” Black turpentine beetles attack pine trees 8 to 10 feet from the ground.
Being able to identify black beetles is important. Though black ground beetles are usually beneficial garden and crop pest hunters, black carpet beetles and black turpentine beetles are harmful. Knowing which beetle is which can help you manage a potential pest problem.