No. 04] DIPTERA OF CONNECTICUT: MORPHOLOGY 31 



The labriim is small in some Nematocera such as Trlchocera (Ficr. 

 jl. G) and most myeetophilids (Fig. 1, H), and is membranous in 

 RhahdojjJiagus and Ohironomus ; but in certain other Nematocera, such 

 as the blepharocerid shown in Fig. 1, B, it is well developed and is 

 strongly .sclerotized. The labrum is great!}' elongated in the tipulid 

 Geranomy'm (Fig. 4. H) and in the female culicid shown in Fig. 3, E. 

 It is well developed in the piercing mouth parts of the tabanids (Fig. 

 1, J), and is much elongated in the tabanid Pangonia longirostris. It 

 is also considerably elongated in the cj^rtid shown in Fig. 3, C. As a 

 rule, the labrum is onh' moderately developed in the Cyclorrhapha, 

 but it may become rather long in some of these also, as is the case in 

 the syrphid shown in Fig. 4, B. 



The labrum usually forms the roof of the food canal (or food 

 channel), and the hypopharjiix usually forms its floor in the higher 

 Diptera. Radial muscles, extending between the outer (anterior) 

 walls of the labrum and the walls of the epipharynx, serve to dilate 

 the lumen of the food channel extending between the labrum and the 

 hypopharynx, and aid in sucking up liquid food. 



The epipharynx is formed by a sclerotization of the hinder or 

 "inner*' surface of the labrum (i. e., the surface which would be ven- 

 tral in the prognathous position) ; and the epi})harynx is therefore 

 not a distinct and separate structure which has united with the labrum 

 to form the so-called "labrum-epipharynx", as is claimed by some dip- 

 terists. The epipharyngeal region of the labrum is not greatly modi- 

 fied as a rule, but in some of the Dolichopodidae chitinized prongs 

 project from the epipharyngeal region, and were mistaken for man- 

 dibles by Langhoffer (1888). 



The hypopharynx. hp^ \s an unpaired, median, stylet-shaped 

 structure immediately behind the labrum, Ir (Fig. 4, B), with which 

 it is frequently associated to form the floor of the food-channel, whose 

 roof, and sides, are formed by the labrum, Ir (Fig. 4, F). The sali- 

 var}- duct, sd, of Fig. 4, E, enters the basal portion of the hypo- 

 pharynx, and is continued as a channel extending to its tip, in many 

 Diptera. A dilation of the salivary duct in this region forms the 

 salivary bulb, or sj^ringe, occurring in many Diptera. The develop- 

 ment of the hypopharynx frequently parallels that of the labrum, and 

 in such a tipulid as Geranomyki (Fig. 4, H), the hypopharjaix, A^, 

 becomes extremely elongated when the labrum, li\ becomes elongated, 

 while it is greatly reduced in the tipulids which have a short labrum. 

 In the nycteribiids the hypopharynx may be much longer than the 

 labrum, but in the cyrtid Lasia shown in Fig. 3, C, it is nuich shorter 

 than the elongated labrum, Ir. 



The hyoid sclerite, ho, of Fig. 4, E, is a sclei-otized area situated 

 in the basal region of the labrum and hypopharynx, and forms a con- 

 necting capsule between the food channel (extending between the la- 

 brum and hypopharynx) and the food pump in the floor of the ful- 

 crum. Hendel (1928) calls the hyoid sclerite the "theca", although 

 other dipterists apply the designation "theca" to the prementum, etc. 



The fulcrum, fu, of Fig. 4, B and E, is a stirrup-shaped, internal 

 structure, sometimes referred to as the "pharjTigeal skeleton", al- 



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