368 MR A. E. SHIPLEY AND MR EDWIN WILSON ON A 



cross-nervure,* and, as we have stated, we consider it to be slightly movable. On its 

 hinder, free edge the bar carries a series of thirteen to fifteen well-marked teeth, 

 which, under certain circumstances, rasp across a series of ridges borne on the second 

 part of the system, which we now proceed to describe. . 



This is coloured yellow in our Plate. It consists primarily of a chitinous blade B, 

 shaped something like a butcher's knife, which is ridged on its upper surface with 

 thirteen to fifteen sharply-defined elevations placed slightly obliquely. It is against 

 these ridges that the teeth of the bar mentioned above rasp. The relative position 

 of the bar and the blade is not constant. The latter is usually lying partly under 

 the former, but at times it is free from it, and it seems as though it were hinged at 

 the handle and can oscillate through a few degrees, around an axis at the base of the 

 proximal end. But it cannot rotate very far. A little way behind the back of the 

 blade is an Upstanding flange of the membranous tissue of the wing, which we have 

 called the trough C. This trough catches and holds the blade, and prevents the 

 latter being thrown too far back. 



It is worthy of note that the wing area between C and A, over which the blade 

 travels, is quite smooth and entirely free from the minute hairs or prominences which 

 cover the rest of the wing. A similar freedom from these processes is found beneath 

 the next region of the apparatus to be described, and this, in our opinion, is also 

 slightly movable. These are the only two regions of the entire wing which are 

 quite smooth and free from hairs. 



The base of the blade or handle is held in position partly by being clamped by 

 the overlying bar A, and partly by a chitinous flap of the wing marked H in our 

 figure. Underneath this is a knob or process which may act as a fulcrum on which 

 the knife rotates. 



Running from the extreme proximal end of the knife handle to the posterior inner 

 angle of the wing are a series of sclerites of irregular outline, roughly recalling in shape 

 a number of knuckle bones. The most distal of these, D, seems to send a process into 

 a hollow at the extreme base of the knife, and may very probably serve to throw the 

 latter in, and out of, gear. The middle sclerite E seems to be articulated with 

 the proximal F by a very distinct joint, and the proximal runs into the thorax, just 

 ventral to the scutellum, and forms the attachment of the wing to the body at the 

 posterior edge. 



The bases of the middle sclerites are overshadowed by a flange G 1 which is supported 

 by the thickened ridge G which forms the outer limit of the squama. 



It must be remembered that the attachment of the wing is not in one horizontal 

 plane, but the line of junction has a slightly oblique course. The posterior edge of 

 the base of the wing is slightly dorsal to that of the anterior end of the same. 

 Hence it seems probable that, as the wings are raised and depressed, there will be a 

 shearing action between the slightly movable toothed bar A and the ridged blade 



* Vide Nuttall and Shipley, J, Hygiene, i., 1901, p. 475. 



