any of about 85 species of solitary (nonsocial), primitive wasps (order Hymenoptera), classified in five different genera, that 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
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