252 CLASS vin. 



insects it is not the same in the first two pairs of feet and in the last 

 pair, yet in most Insects the number is five. In some coleopterous 

 insects, the penultimate joint is extremely short, and was in conse- 

 quence overlooked formerly. The last joint of the foot usually ends 

 with two booklets, or claws : in addition, its inferior surface is often 

 covered with fine hair, to attach it to small inequalities which even 

 the smoothest objects present. Sometimes these hairs are set on 

 two or three delicate membraneous appendages (cushions, pulmlli] 

 which the Insects mould to the surfaces over which they run. In 

 this way flies can move upwards on mirrors, or with head down- 

 wards on smooth ceilings, as is seen daily 1 . 



Besides the feet, wings also are placed on the thorax of volant 

 insects : on the meso- and meta-thorax, as stated above, when there 

 .are four: when only two, on the meso-thorax. They are set on the 

 dorsal surface, and may be compared with the elytra or squamce in 

 Aphrodita: with the wings of vertebrate animals (Birds, Bats), which 

 are only modifications of the anterior limbs, they have only similarity 

 of use : they are not modified feet : they exist contemporaneously 

 with feet and are independent of them 2 . Wings are membraneous, 

 arid, usually transparent, composed of two laminae grown together 

 at the edges ; these laminae are expansions of the skin like the 

 parachute extended between the fingers of Bats and between the 

 ribs of flying Lizards (Draco). Canals (improperly named Veins 

 or Nerves) run between the laminge, and are more or less numerous, 

 more or less branched. These veins are branches of the air-tubes, 

 which lie between two wide horny semicanals of the upper and 

 under laminae that compose the wing. In some species the males 

 alone have wings. Bees, Wasps, Butterflies, &c. have four wings. 

 In the Diptera, besides the wings there are two parts which may 

 be considered as traces of hind- wings, called poisers (halter es] ; 

 they consist of a little button with a pedicle, and are often covered by 

 a membraneous scale (squama halterum) 3 . The anterior wings are 



1 BLACKWELL, Remarlcs on the pulvilli of Insects. Transact, of the Linn. Soc.Vol. xvi. 

 Pt. 3, pp. 487492. 



3 OKEN names the wings of insects gills; the elytra of Coleoptera he considers, less 

 happily, to be gill- covers ; they must have the same anatomical interpretation, (Bedeu- 

 tung), as the under- wings. Lehrbuck der NaturpkUosophie, in. 1811, s. 271; the 

 same work entirely revised. 1843, s - S 1 ^' 



3 See AUDOUIN, Diet, class. d'Hist. not. II. pp. 140 142, at the word Balanciert, 

 and NEWPORT, 1. 1. p. 926. 



