512 



MR. J. DAVIDSON ON THE BIOUTH-PARTS AND 



A Jarge median plate, which I call the clypeus, cl., extends from the 

 proximal margin of the fore-head and forms the greater part of the anterior 

 face. Distally it narrows somewhat, and is divided by a shallow, trans- 

 verse depression from a smaller triangular sclerite, cl.l. This I call the 

 dypeo-labrum. It seems to be really a continuation of the clypeus. A 

 tapering plate of chitin, the lahrum, Ibr., extends in the median line from 

 the distal end of the clypeo-labrum. 



The floor of the clypeo-labrum, PI. 24. fig. 1, e.p., is composed of thick 

 chitin, which forms the roof of the pharyngeal duct, jjJi.d. This is the 

 epipliarynx. It possesses a deep, longitudinal groove on its internal face. 



Text-fig. 1. 



mx.pr 



Transverse section through the fore-head in region of pharynx protuberances, showing 

 relation of sclerites forming the fore-liead. X300. 



(For explanation of lettering see p. 329.) 



as is shown in transverse sections,, figs. 7-9, which affords a support for the 

 maxillary stylets. 



Distally, it is continuous with the internal face of the labrum, but the 

 chitin becomes much thinner. 



The labrum possesses a few, small, transverse ridges on its outer face and 

 a longitudinal groove on the internal face. It is connected with the clypeo- 

 labrum by a thin chitinous fold, which permits free movement. 



Two folds of chitin, the clypeal folds, text-fig. 1, c/./'., extend into the 

 fore-head on each side of the clypeus, and become continuous with the dorsal 

 wall of the pharynx. 



