62 tHE ENTOMOLOGIST. 



are also modified. The province, as altered, contains four 

 sub-provinces, as under : — 



1. Hexapods, which at no 'period of their existence have 

 more than six legs, and which are variously known as butter- 

 flies and moths; gnats and flies; bees, wasps andsawflies; 

 beetles; locusts and cockroaches; bugs, plant-bugs, plant- 

 lice, animal-lice, springtails; dragonflies and stoneflies, &c. : 

 these are associated by the single and simple, though 

 constant, character of possessing six legs, and no more. 

 These frequently possess also two or four wings; but in 

 a primary definition this appears scarcely deserving of 

 notice, since wings are so frequently wanting. [These are 

 the Insecta of Latreille.] 



Moreover, these insect-wings are in reality windpipes, or, 

 perhaps, speaking with greater precision, portions or branches 

 of windpipe everted and altered expressly to fit them for 

 the function of flight, instead of confining their duties 

 to the more ordinary and — as we believe — normal office of 

 respiration. In order to achieve this additional duty, we find 

 that certain main branches of windpipe, having forsaken 

 their usual site in the interior of the trunk, issue, one or two 

 from each side of the mesothorax, and one or two from each 

 side of the metathorax, each branch encased in a bony 

 cylinder, which is frequently sufficiently transparent to admit 

 of the structure of the windpipe being seen through its 

 walls; while the constant pulsatory movements of blood- 

 disks everywhere, between each cylinder and its enclosed 

 windpipe, proves, beyond the possibility of doubt, the 

 existence of a circulation throughout the insect world. These 

 external ramifications of the windpipe, and as a consequence 

 its bony casings, are infinitely less numerous than those 

 confined to the trunk, Lyonet having stated that he counted 

 1804 branches in a specimen of Xyleutes Cossus, and that 

 he only discontinued counting because they eluded the 

 powers of his glass from excessive tenuity. Still they are 

 numerous and conspicuous, and subserve the useful purpose 

 of supplying characters to the descriptive entomologist; but 

 of this more hereafter. We find them always connected 

 with each other throughout their length by a membrane, 

 which, in fact, is double, or composed of two membranes, 

 although it appears as only one : its double character is 



