62 THE ENTOMOLOGIST. 
are also modified. The province, as altered, contains four 
sub-provinces, as under :— 
1. Heaapods, 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 and sawflies ; 
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 Jnsecta 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 
