252 CLASS VIII. 
insects it isnot 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 hooklets, or claws: in addition, its inferior surface is often 
covered with fine hair, to attach it to small imequalities which even 
the smoothest objects present. Sometimes these hairs are set on 
two or three delicate membraneous appendages (cushions, pulvilli) 
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}. 
Besides the feet, wings also are placed on the thoraa 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 squame 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?. Wings are membraneous, 
arid, usually transparent, composed of two laminz grown together 
at the edges; these lamine are expansions of the skin hke 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 lamine, 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 lamine 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 povsers (halteres) ; 
they consist of a little button with a pedicle, and are often covered by 
a membraneous scale (squama halterum)*. The anterior wings are 
1 BLACKWELL, Remarks on the pulvilli of Insects. Transact. of the Linn. Soc. Vol. XVI. 
Pt. 3, pp. 487—492. 
2 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. Lehrbuch der Naturphilosophie, U1. 1811, s. 271; the 
same work entirely revised. 1843, s. 316. 
3 See AupouiIn, Dict. class. d’Hist. nat. 11. pp. 140—142, at the word Balanciers, 
and Newport, 1. 1. p. 926. 
