LOCUSTS AND GRASSHOPPERS (ACRWIID^E). 87 



straight on its course for miles by favouring winds. 

 Meanwhile, scarcely as much muscular force is spent 

 through the day as is exerted during a few vigorous 

 hops. Towards evening, and in damp and cloudy 

 weather, the powers of flight are lessened, owing to the 

 diminished power of respiration. In the possession and 

 use of these air-sacs, locusts may be compared with 

 birds. 



When in addition to the sacs we find many expanded 

 or dilatable tracheae, chiefly in parts of the body where 

 there is not room for the sacs themselves, we can duly 

 estimate the wondrous powers of the locust as an 

 aeronaut. 



Intellectually the Acridiidae appear to be the equals 

 of most other insects, while many are inferiorly endowed. 

 Those that excel them in this respect are the ants and 

 bees or wasps, the social hymenoptera, which have a 

 brain constructed on a higher, more complicated, plan 

 than in the other winged insects. It must be under- 

 stood that the word " brain " so applied is a mere 

 courtesy term, as the brain of our insects does not 

 correspond to the brain of a vertebrate animal. It 

 consists of a double ganglion, placed in the upper part 

 of the head, the first and largest of the two ganglia 

 therein. Moreover, it is a much more complicated organ 

 than any of the others, having parts which are wanting 

 in them, hence it is par excellence nearer to our idea 



