HORNTAIL

any member of the insect family Siricidae, a group of solitary (nonsocial) wasps of the order Hymenoptera. Five genera and about 60 species have been described. Horntails are moderately large, some reaching 3.75 cm (about 1.5 inches) in length. The cylindrical body is usually brown, blue, or black, often with yellow spots or bands. The abdomen is connected broadly to the thorax, or midsection, and terminates in a harmless hornlike projection, for which the insect is named. The head is strikingly broad, and the eyes are small. Female horntails use a conspicuous ovipositor to lay eggs. The ovipositor is used to drill a hole into a hardwood tree, particularly elm, beech, maple, or apple. The larvae tunnel through the tree for about two years, eating the wood. The insects are seldom economically destructive. Pupation takes place in a cocoon of silk and sawdust. The most common North American species is the pigeon tremex (Tremex columba). The adult is black and brown with yellow body stripes and yellow legs; its length is about 3.75 cm. The most common British species is Urocerus gigas, which feeds on the wood of pine trees.