The Mouth-parts of the Nemocera. By W. West-he". II 



Porphyrons gravipt s W. 



Argyra argyria Mg. 



Medetcrus truncorum Mg. 



Aphrosylus raptor Hal. 



Chrysotus laesus W. (?) 



Psilopus vjiedemanni Fin. 



Campsicnemus scambus and (.'. curvipes Fin. 



MachwHum maritimce Hal. 



Hydrophorus litoreus I- In. 



The trophi of Aphrosylus raptor Hal. are like the limbs, 

 highly specialised for the attack of other insects, but they are also 

 of great interest from the anatomical point of view. The mosi 

 remarkable part is the labium, which is without the usual tracheae ; 

 the mentum is but little developed, and lacks the median process 

 that is found so constantly on this part in the Dolichopodidaa ; 

 nevertheless, the mandibles are imbedded, as dissection reveals 

 two broad blades in the muscles of the ventral side ; an interest- 

 ing confirmation of my theory as to the migrations of this part. 

 It can now be seen that Aphrosylus has halted in a stage of 

 development, which such genera as Dolichopus and Poecilobothrus 

 must necessarily have passed through. The dorsal sides of the 

 labium show the levers which are homologised as cardmes and 

 stipites in Dolichopus, but half-way up there is a thickening of the 

 chitin which suggests the junction of the stipites and laciniae ; if 

 this is the case it indicates another arrest of development. The 

 palpi are fiat and thinly haired, the hypopharynx is narrower than 

 in Dolichopus ; the labrum is formed into two large curved hooks, 

 and the portion between these hooks is very strongly and shortly 

 haired. Like the same part in D. griseipennis figured in the 1 ( .»04 

 paper, the back of the labrum is drawn out into a powerful lever 

 to which are attached muscles to work the labrum as an offensive 

 weapon (plate II. figs. 33-37). In Gymnoptemus assitnilis Staeg. 

 there is a type of trophi intermediate between Dolicliopus and 

 Orthochilc; the labium, while retaining most of the characters of 

 Dolichopus, being lengthened. This seems to indicate a change of 

 habit in favour of flower feeding, and this idea is confirmed by the 

 conteuts of the stomach, which is full of pollen (plate II. fig. 32). 



Psilopus wiedemanni Fin. departs in the trachea- of the 

 paraglossse from the usual curious type in the family, but still 

 retains traces, and keeps the barbed labrum and vent rally 

 imbedded mandibles, nearly always found in the Dolichopodida\ 



I shall devote considerable attention to the Phoridse, as very 

 little work has been done on the trophi, and owing to many 

 peculiarities, the position of the family in the systematic lists is 

 a matter of debate, on which the character of the mouth-parts 



