20 



action of the parts, this connecting membrane is suppHed with 

 certain highly chitinized portions which act presumably as 

 "braces" or "connecting rods." The parts, as a whole, are very 

 strong, being highly chitinized throughout. So much so. in fact, 

 that it was found necessary to first boil them in caustic potash 

 (5 per cent, solution) before attempting to study them. 



The position of the mouth-parts on the head is ventral. The 

 clypeus extends out over the parts with the exception of the 

 mandibles, which fold together directly in front, and the distal 

 ends of the maxilary palpi and the labrum-epipharynx. 



That the parts do represent a generalized type may be seen by 

 looking at those of Lyda sp. (Plate I, figure i.) The parts are 

 drawn in situ to give an idea of the comparative size of the dif- 

 ferent parts and their position in relation to each other. We have 

 here mandibles {nid), strong, highly chitinous, large in compari- 

 son to the other parts and acting independently. The view is 

 ventral and the labium {11) is seen overlying the other parts. The 

 mentum {m) is shield shape, the lateral edges being bent inward 

 like the sides of a saddle. From the mentum extend distad the 

 glossa {gl) and the paraglossa ipgl). Caudad of the mentum and 

 lying in the connecting tissue is a portion that is chitinized and 

 supplied with hairs. Until further studies of higher orders are 

 made this part will be called the sub-mentum {sm), since in go- 

 ing from the lower to the higher forms this structure becomes 

 more and more important and is in the family Apidae distinctly 

 joined to the mentum. The tendency, however, is shown within 

 the family Tcnthrcdinidac. From the base of the paraglossa 

 extend laterad on either side the labial palpi ( lip ) . They are four 

 lobed. There is an hypopharynx but it is not distinct in some 

 species. It is well shown in drawings farther on. 



Right and left of the labium lie the maxillae {inx). One of 

 another species can be seen dissected out in Plate II, figure 4. 

 This figure will serve equally well in describing the parts. This 

 is figured for the reason that in Lyda sp. the cardo {cd) is not 

 visible since it forms with the stipes (st) a right angle. The 

 maxillae are not unlike the general type, that is, the cardo, stipes, 

 galea, and lacinia are easily understandable. The stipes, as is 

 also the mentum of the labium, is very much arched, making it 

 difficult to show the true form bv drawing one aspect. 



