CHAP. II.] CLASS ION AND NOMENCLATURE. 17 



Chapter II. 

 ( CLASSIFICATION AND NOMENCLATURE. 



■• 1 iur little systems have- their day ; 

 They have their day, and cease t 



Tennyson— in .)/. moriam. 



m distincte tradere convenit Nomina si pereunt, perit et 

 ; -'i rerum ; nomina si confundantur, confundantur omnia 



THE correct classification of insects is a problem which has 

 exercised the minds of entomologists for at least three centuries 

 and that various systems and schools of thought are in existence 

 at the present clay affords perhaps the best proof that the problem 

 is not so simple of solution as may at first appear. 



The casual observer who walks through a field and sees 

 grasshoppers jumping away before his advance may think that 

 grasshoppers are easily defined as insects that jump. Hut such a 

 definition would also include many other inserts, such as fleas and 

 some bugs and beetles, which no one would call grasshoppers. A 

 fly, it may be said, is easily distinguished by having only one p 

 of wings; but other insects, such as the males of some scale- 

 insects, share this similarity yet differ from flies in many other 

 respects. Bees and wasps may be defined as stinging insects, 

 but many caterpillars can sting just as badly, whilst the males of 

 the bees and wasps have no sting at all. Caterpillars of butterflies 

 and moths may be said to feed on leaves, but so do those of 

 sawflies, beetle-, etc. Such definitions — or, it would be better to 

 say. such popular generalisations — have very little value, but 

 they may serve at the same time to give some idea of the difficulty 

 of classifying such an enormous assemblage as the world of 

 insects by characters either natural or easily observed. 



The systems of classification generally used have been based 

 as a rule on the structural characters of the adult insect, especially 

 on those of the wings and mouth-parts, or on the type of metamor- 

 phosis or series of changes which insects undergo before attaining 

 the adult condition. Each system has its good points and its bad 

 and neither by itself can be accepted as satisfactory, 



-tern based solely on the type of wings, for example, might 

 unite grasshoppers and bugs and also flies and scale-ins 

 whilst the wingless crickets, wasps, moths, fleas, lice, etc., could 

 not be separated at all. The »n of sucking or biting 



mouth-parts seems at first sight to idler a reliable distinctive 

 character and the nectar-sucking butterflies and moths ma 

 quoted as examples until we find that some of the moths have 

 biting mouth-parts, and that some insects, such as bees and Thrips, 



