56 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. 139 



The mandibles are the slenderest of the stylets, but they vary some- 

 what in thickness and shape in different species. In Aedes here 

 illustrated (fig. 20 H, Md) each is slightly enlarged toward the taper- 

 ing distal end. The base of each mandible is movably connected with 

 the lower part of the cranial wall by a small suspensory sclerite, and 

 a slender muscle from the tentorium is inserted on the mandibular 

 base. The mandibles are thus retractile for a short distance, and, when 

 retracted, their withdrawn tips give free entrance to liquid into the 

 open end of the labral food canal. Protraction results from the elas- 

 ticity of the suspensory mechanism on relaxation of the muscles. 



The single, median hypopharynx, present as an independent stylet 

 only in the female, is a simple, flattened rod (fig. 20 H, Hphy) 

 traversed by the salivary outlet canal (sc), which opens on its acute 

 tip. The hypopharynx is not individually movable ; its anterior wall is 

 continued basally into the floor of the cibarial pump. 



The maxillae are less reduced than the other mouth parts, and are 

 well equipped with muscles. The principal part of each maxilla (fig. 

 20 I) is a long, flattened, sharp-pointed blade (Lc) armed with re- 

 curved teeth near the end of its outer margin (H, Mx). From the 

 base of the blade projects a usually short four-segmented palpus (I, 

 Pip). The maxillary blade has been regarded as the galea by some 

 writers (Robinson, 1939; Snodgrass, 1944), but it is more reasonably 

 interpreted by Schiemenz (1957) as the lacinia, which is usually the 

 operative part of a generalized maxilla. From its base a long, strongly 

 sclerotized, apodemelike rod extends backward in the head and gives 

 attachment to muscles (J). This rod is evidently the stipes, or more 

 probably stipes (St) and cardo (Cd) combined, sunk into the head, 

 since in some related flies, such as Phlebotomus (fig. 22 G), it is 

 superficial on the back of the head and articulates on the cranial 

 margin. 



The maxillary musculature of Aedes (fig. 20 J) includes a long 

 retractor arising on the head wall close to the posterior end of the 

 tentorial arm (Tnt) inserted on the distal end of the stipes, and two 

 protractors attached proximally on the stipito-cardinal rod. One of 

 these muscles arises on the tentorium, the other, very curiously, on the 

 base of the labium. A lateral muscle from the tentorium and a short 

 mesal muscle both attached on the base of the lacinia are regarded 

 by Schiemenz (1957) in Theobaldia [Culiseta] as an abductor and 

 adductor respectively of the maxilla. A short muscle from the stipes 

 is inserted on the base of the palpus, and each palpal segment contains 

 a small muscle inserted on the segment distal to it. 



