72 LONDON INSECTS 



themselves, but only a class of the so-called wingless 

 order 'both pairs are rudimental and functionless 

 as wings. Of these orders the first five are haustel- 

 late ; the next four are mandibulate. The Aptera 

 are ametabolian ; the Hemiptera and Orthoptera are 

 hemimetabolian ; the remaining orders are metabolian.' 



' These characters,' Professor Owen adds, ' briefly and 

 succinctly express the highest generalisations, as yet 

 reached, relative to the Hexapod Insecta,' 



But here, as in every attempt of the kind, the more 

 perfect the work, the more one is made to feel that 

 classification, absolutely necessary as it is as a step 

 towards progressive knowledge, is at best a purely 

 human invention, and that there is no such thing as a 

 hard-and-fast line anywhere in Nature, where all is 

 gradual. We can find out without much difficulty 

 when the gas-lamps are lighted they are human 

 institutions, but it would puzzle the wisest of us to 

 say exactly when it is that the ' crimson streak ' on 

 the Serpentine ' grows into the great sun.' No wings, 

 two wings, and four wings are, we can see, the general 

 characteristics of large classes, but at what precise 

 spot the separating lines are to be drawn on paper 

 must be, to a great extent, a matter of fancy. They 

 may be, in most cases, moved up or down without its 

 mattering very much. As already mentioned, among 

 the wingless insects is a class the Aphaniptera 

 which has 'scales representing rudimentary wings.' 

 Most of the 'two wings' have a rudimentary second 

 pair, known as 'balancers,' behind their more perfect 



