50 MEMBERS OF INSECTS. 



flanks, and the back plate of the corselet, one pair 

 uniformly on the mid corselet, and the other uniformly 

 on the hind corselet. 



The upper or fore wings^), which may he also called 

 the greater or first pair, are always jointed upon the 

 two upper flanks, and the hack plate on each side of 

 the mid -corselet, and of course near the centre of 

 gravity, being balanced on the one side by the head 

 and fore corselet, and on the other by the abdomen 

 and hind corselet. 



Somewhat like the human wrist, which is composed 

 of a number of little bones, the wing joint in insects 

 has small horny joint pieces ( 2 ), to the number of seven 

 in the first pair, of various size and figure, but all 

 united by a membrane, and jointed on the one side 

 with the wing, and on the other, with the back plate 

 and upper flank. 



These joint pieces move the wings by means of 

 three muscles, the first divided into two portions 

 where it is attached to the inside of the corselet ; but 

 these unite into a single tendon, and are fixed into 

 one of the joint pieces. When this muscle contracts, 

 it lowers the base of the wing and consequently raises 

 the tip. 



A second muscle is also fixed within the corselet, 

 and is attached to another of the joint pieces. This 

 muscle lowers the inner edge of the wing and gives 

 it a sort of pendulum-like motion. 



A third muscle is similarly placed, and acts in con- 

 cert with the two first. 



The preceding description applies to the wings of 

 bees and wasps ; while in two-winged flies there are 

 two sets of muscles : one set placed lengthwise for 



(I) In Latin, Alee anterior es. 

 (2) In Latin, Epidemee. 



