Perhaps surprisingly, ‘bug’ is not a very old word for insects, having only appeared in the 17th century. By comparison, ‘fly’, ‘midge’ and ‘gnat’ have roots in ancient languages.
Originally, the term was mostly used to mean a night-fear, bogey or hobgoblin. Its relevance to insects crystallised around 1730 with John Southall’s A Treatise of Buggs, which dealt with bedbugs. Its use has since broadened.
To the entomologist, true bugs belong to the order Hemiptera (‘half-winged’) – a group that includes aphids, cicadas, capsids, leafhoppers, shieldbugs, boatmen, squashbugs, bedbugs and water skaters. They tend to have part-hardened wing cases, like beetles, but tubular sucking mouthparts rather than biting jaws.
Bugs can be both plant-feeding and predators. Most shieldbugs suck plant sap, but there are four UK species that hunt soft-bodied invertebrates such as beetle larvae. This suggests a recent (in evolutionary terms) divergence from their plant-feeding ancestors. On the other hand, all assassin bugs, damsel bugs, boatmen and skaters are predators, suggesting that they made the jump to hunting long ago.
Of late, ‘bug’ has become an eclectic term, referring to almost all invertebrate life as well as diseases, software faults and even microphones.
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