MAXILLARY PALPI IX DIPTERA. 



223 



In tlie female the maxillae, mandibles, hypopharynx, and labrum are very beautiful 

 weapons. In the male the lancets are obviously atrophying, and they can only with 

 difficulty be dissected out from the enclosing labium. Here is seen the process, which 

 has been completed in the Syrphidae and Empidse, actually proceeding, or suddenly halted 

 in a stage of the process. 



In the males the cardines of the maxillae hinge on to the maxillary palpi, which, in 

 this sex, are very long and highly developed (PI. 9. figs. 25, 26, and text-fig. 2). 



Summary. — In the Muscidae the mandibles are embedded in the dorsal side of tlie 

 labium. The maxillary palpi, galeae, and laciniae are aborted, but the cardines remain. 

 The palpi present are labial, and the palpigers are represented by chitinous plates with 

 two or three setae springing from or near them. 



In the Syrphidae and Empidae the mandibles are similarly placed, but the maxillae are 

 represented by the laciniae, the palpi, cardines, stipites, and palpifers. The labial palpi 

 are aborted. 



Rule. — A rule can be formulated : — The maxillary palpi token present in Diptera are 

 always in contact with the upper part of the cardines, the stipites. 



Fis. 2. 



Extremities of maxilla and mandible of Culex pipiens, $ . 



JRudimentary Maxillary JPaljn. — I was fortunate in discovering a number of species, 

 in the Anthomyiidae, Muscidae, and other families of the Cyclorrhapha, with four 

 palpi which afford useful clues to the surrounding parts. They appear in different 

 stages of atrophy, from a fairly developed organ to a rudiment of a few hairs. Some 

 examples were described in a paper read at the meeting of the Royal Microscopical 

 Society on June 18tb, 1902, and since published in the Journal of that Society *. 

 These palpi enable us to indicate the position of the maxilhe with certainty, and, 

 by proving the other pair to be labial, establish the proposition that the whole organ is 

 the labium. 



We have now the mandibles, the maxillae and palpi, the labium and palpi, and the 

 mentum clearly defined. 



Faraglossa', Ligulce.—'We now come to the parts of the labium, the paraglossae and 



* Journ. Roy. Micr. Soc. 1902, p. 412. " Undescribed Palpi on the Proboscis of somo Dipterous Flies, with 

 Remarks on the Mouth-parts in several Families." 



