24 OUTLINES OF ENTOMOLOGY. 



With insects, as with all other organic beings, the species is the 

 root of classification the only group defined by nature. All other 

 associations of forms, though based upon natural affinities, have been 

 devised by man, and, being in a sense artificial, are liable to rearrange- 

 ment, restriction or extension whenever new discoveries, or the adop- 

 tion of new theories of classification, make such changes seem desirable. 



In classifying insects we first group them according to their gen- 

 eral structure : i. e., arrange them in their proper Order, Tribe, Family 

 etc., which is ordinarily quite easy, after which we proceed to look up 

 the more difficult matters of genus and species. 



The first step, then, is to determine in which Order a given speci- 

 men belongs. This can usually be decided without difficulty by an 

 examination of the wings, for in the system of classification most gen- 

 erally adopted, the Orders seven in number are mainly founded upon 

 the character of these conspicuous and important organs, and the 

 names of these Orders are Greek compounds of which the termination 

 jptera means wings^ while the prefix describes the kind of wing. 



There is some difference of opinion among writers as to the rela- 

 tive rank of the Orders, but the following arrangement seems most in 

 harmony with the development of the insects included in each Order, 

 -and has the sanction of a majority ot the best authorities : 



I. H YMENOPTERA (membrane- wings), bees, wasps, ants, etc. 



Jl. COLEOPTERA (sheath-wings), beetles. 



III. LEPIDOPTERA (scale-wings), butterflies and moths. 



IV. D1PTERA (two wings), house-flies, mosquitoes, gnats, etc. 

 V. HEM1PTERA (half-wings), true bugs, cicadas, plant lice, etc. 



VI. ORTHOPTERA (straight- wings), grasshoppers, katy-dids, crickets, etc. 

 VII. NEUROPTERA (nerve-wings), dragon-flies, lace- wing flies, etc. 



Two of these orders, COLEOPTERA and DLPTERA, were defined 

 ^according to the type of wing, by the Greek philosopher Aristotle, 

 more than three hundred years before the Christian era. Thus it will 

 be seen that entomology is one of the most ancient of the natural 

 sciences, although for many centuries it made little or no true progress. 



Adopting the idea of Aristotle, Linnaeus (or Linne), a Swedish nat- 

 uralist, and the most celebrated one of the eighteenth century, pro- 

 posed five additional orders. In his system, however, the ORTHOP- 

 TERA were included with the HEM1PTERA, and the seventh order 

 APTERA was devised to contain all insects which, in their perfect state, 

 lacked wings. But as it was long since discovered that wingless spe- 

 cies and wingless females exist in each of the orders, from which it 

 would be extremely inconvenient to separate them, the order APTERA 

 was dropped and its number made good by a very necessary separa- 

 tion of the ORTHOPTERA from the HEMIPTERA. 



