THE CLASSIFICATION OF INSECTS 59 



Many naturalists recognise seven orders of the class 

 Hexapoda, or Insecta, namely : — 



Orthoptera (or straight-winged). 

 Ncuroptera (or nerve-winged). 

 Coleoptera (or sheath-winged). 

 Hymenoptera (or membrane-winged). 

 Lepidoptera (or scale-winged). 

 Diptera (or two-winged). 

 Hemiptera (or half-winged). 



In the first three orders — Orthoptera. Neuroptera, and 

 Coleoptera all the mouth-parts are formed for biting; 

 in Hymenoptera the mandibles, as such, are always 

 present, but the other mouth-parts are usually adapted 

 for licking and sucking; while in the three last orders — 

 Hemiptera, Lepidoptera and Diptera — all the mouth- 

 parts are definitely modified for sucking, or for piercing 

 and sucking. This arrangement of insects, however, does 

 not account for certain small groups of parasitic, or semi- 

 parasitic forms, such as the fleas ; while it includes in the 

 order Neuroptera an assemblage of families which differ 

 greatly in their life-histories, and in many details of their 

 structure. We shall be well advised, therefore, to follow 

 the more extended scheme of classification adopted by 

 Professor Carpenter in the current edition of the Encyclo- 

 pedia Britannica, in which nineteen orders are recognised. 



Order I. — Aptera. 



This order is made up of tiny insects, typically mandi- 

 bulated, which never develop wings. They undergo 

 no kind of metamorphosis, the newly-hatched young 

 resembling the adults except in size. The segments of 

 the body are more clearly defined and less modified than 



