352 MOTIONS OF INSECTS. 



brane to n leathery or Iiorny crust ^ — and those in which 

 the base and the apex are of different substances ; the 

 first being "generally corneous, and the latter membra- 

 naceous''. The former division includes the Cicadiadce; 

 Aphis; Chermes; Thrips; and Cbrr?/.? ; — and the latter 

 the Cimicidce^ comprehending besides the Linnean ge- 

 nus Ciniex Notonecta ; S/oara ; Nepa ; Jlanatra ; and 

 JVaiicoris of Fabricius. The posterior tibiaB of some of 

 this last division (Li/gceusphj/llopifSjJbliaceus, &c., F.) 

 are furnished on each side with a foliaceous process — 

 which may act the part of out-riggers, and assist them in 

 their flight*^. I can give you no particular information 

 with respect to the aerial movements of the insects of 

 this order : the British species that belong to it are 

 generally so minute that it is not easy to trace them 

 with the naked eye; and unless some kind optician, 

 which vis much to be wished, would invent a telescope 

 by which the proceedings of insects could be examined 

 at a distance, there is no other way of studying them. 



The four Avings of the next order, the Trichoptera 

 or case-worm flies, both in their shape and nervures 

 resemble those of many moths''; only instead of scales 

 they are usually covered with hairs, and the under 

 wings, which are larger than the upper, fold longitu- 

 dinally. Some of these flies, I have observed, move 

 in a direct line, with their legs set out, which makes 

 them look as if they were walking in the air. In fly- 

 ing they often apply their antennae to each other, 

 stretching them out straight, and thus probably are as- 

 sisted in their motion. 



» Plate II. Fig. 4. " Plate X. Fig. 3. II. Fig. 5. 

 " Plate XV. Fig. 2. * Plate HI, Fig. 4. 



