vi THE ORDERS OF INSECTS 173 



consistency, frequently with much network ; the front pair not much, 

 if at all, harder than the' other pair, the latter with but little or no 

 fanlike action in closing. Mouth mandibulate. Metamorphosis 

 variable, but rarely slight. 



4. Hymenoptera (vfjujv membrane, Trrepov a wing). Four wings of membranous 



consistency ; the front pair larger than the hind, which are always 

 small and do not fold up in repose. Mouth mandibulate, sometimes 

 provided also with a tubular proboscis. Metamorphosis very great. 



5. Coleoptera (xoAeos sheath, TTTfpov a wing). Four wings ; the upper pair 



shell-like in consistency, and forming cases which meet together 

 over the back in an accurate line of union, so as to entirely lose a 

 winglike appearance, and to conceal the delicate membranous hind 

 pair. Mouth mandibulate. Metamorphosis great. 



6. Lepidoptera (AeTrt's scale, Trrepdv a wing). Four large wings covered with 



scales. Mouth suctorial. Metamorphosis great. 



7. Diptera (Sis double, Trrtpov a wing). Two membranous wings. Mouth 



suctorial, but varying greatly. Metamorphosis very great. 



8. Thysanoptera (Ovcravos fringe, Trrepov a wing). Four very narrow fringed 



wings. Mouth imperfectly suctorial. Metamorphosis slight. 



9. Hemiptera (i?/zi half, Trrepdv a wing). Four wings ; the front pair either 



leather-like with more membranous apex, or entirely parchment-like 

 or membranous. Mouth perfectly suctorial. Metamorphosis usually 

 slight. 



We must again ask the reader to bear in mind that numerous 

 exceptions exist to these characters in most of the great Orders; 

 for instance, wingless forms are not by any means rare in several 

 of the Orders. 



Before remarking further on this system we will briefly 

 sketch two other arrangements of the Orders of Insects, for which 

 we are indebted to Packard and Brauer. 



Packard's Classification. 



Packard has devoted much attention to the subject, and has 

 published two or three successive schemes, of which the following 

 is the most recent : * the definitions are those of the author 

 himself, but the information in brackets is given to institute a 

 concordance with the system we adopt : 



1. Thysanura. Wingless ; often with a spring (equivalent to our Aptera). 



2. Dermaptera. Front wings minute, elytra-like ( = Forficulidae, a part of 



our Orthoptera}. 



3. Orthoptera. Wings net-veined ; fore wings narrow, hind wings folded 



( = our Orthoptera after subtraction of Dermaptera). 



1 American Naturalist, xx. 1886, p. 808. 



