86 GNATS OR MOSQUITOES — CHAPTi:R VI 



the four lancets, which are simple, rapier-like blades, simpl}' 

 pointed, and unprovided with teeth or serrations of any 

 kind, though a false appearance of the sort is lent to the 

 points of the maxilhie by the plate of their blades beinf]f 

 fibrillated. The maxillap are usually stated to be the smaller 

 and more delicate, but, as a matter of fact, they are con- 

 siderably the stouter, and except in this the mandibles 

 and maxillae closely resemble each other. Neither pair of 

 lancets appears to be provided with any special musculature, 

 and they are probably forced into the skin simply by the 

 thrust of the head ; the labrum being drawn back while 

 they make their puncture, and then forced into the wound 

 they have made. Lastly, the labium is a comparatively 

 stout, fleshy organ, soft, flexible, and clothed with scales 

 on its outer surface, which is wrapped round the other 

 parts so as to form a sheath, open only above. Between 

 its scaly ventral surface and its delicate dorsal lining is 

 interposed a considerable amount of loose connective tissue, 

 in which lie a pair of tracheae, and immediately^ beneath 

 them two large nerves. The labium ends in a pair of valve- 

 shaped, articulated lobes, capable of being moved by certain 

 special muscles. The function of these lobular organs, 

 which are said to represent the labial palps of certain other 

 arthropods, is probably to grasp the styles as they pierce 

 the skin, while the stem of the labium is being looped 

 down out of the way. 



The above account differs, it may be noticed, from pre- 

 vious descriptions, inasmuch that it has hitherto been 

 assumed that both food and saliva passed through the 

 proboscis by the same channel ; but there can be no doubt 

 of its correctness, which I have verified by several series 

 of sections, in both Culex and AnojjJieles ; and I gather 

 from Professor Grassi that he holds the same view of 

 the functions of the various structures, who I trust will 

 understand that his priority in the matter is herein fully 

 recognised ; though he must not be held responsible for 

 the existence of the salivary valve, and the other structural 

 details of the above description. 



A little reflection will, moreover, show that an arrange- 



