Black bean aphid

The black bean aphid is a small, soft-bodied insect that has specialised piercing and sucking mouthparts which are used to suck the juice from plants. This aphid is usually seen in large numbers and is a tiny, plump insect about two millimetres long with a small head and bulbous abdomen. The body is blackish or dark green in colour. Many adults are devoid of wings, a state known as aptery. Winged forms, known as alates, are longer and more slender than aptates and have shiny black heads and thoraxes. The membranous wings of the alates are held angled over the body. The antennae are less than two-thirds of the length of the body and both they and the legs are pale yellow in colour with black tips. The tibiae of the hind legs are swollen in egg-laying females. Near the rear of the abdomen are a pair of slender, elongated tubes known as cornicles or siphunculi. Their function is the production of a defensive waxy secretion. They are twice as long as the finger-like tail and both are brownish-black.