The Mouth-parts of the Nemocera, etc. By W. Wesche. 45 



prising modifications as the toothed trachea} of Hydrcllia griseola 

 Fin. being found. In Ephydra coarctata, or Parhydra coarctata Fin., 

 of Mr. Verrall's list, are remarkable trachea?, which may reasonably 

 be supposed to be primitive forms. They consist of a number of 

 hairs, arranged in double lines, which arch over and form passages, 

 capable of drawing up fluid by capillary attraction. This insect 

 I have taken in great numbers on marshy spots, and it may be 

 that it is a special modification, enabling the insect to feed on 

 infusoria ; but as it is in this family that I have found complete 

 maxilla? in one species {Hydrcllia griseola)* and remains in several 

 others, I am inclined to think them of very archaic type. The 

 labrum is a rather shapeless fold of skin, pierced with the sockets 

 of hairs, and the hypopharynx is very rudimentary. The larger 

 palpi are labial and thin. The cardines of the maxilla? bear palpi, 

 which in several species are quite relatively large (pi. VIII. fig. 7). 



In Mosillus subsidtans F. are nearly complete maxilla? ; the 

 lacinia? are atrophying, and appear exactly in the same state as in 

 H. griseola ; but the palpi are very hairy, though the gala? have 

 gone ; the stipites and cardines are much altered (pi. VIII. fig. 8). 



Drosophila funebris F. has trachea? somewhat similar to Sapro- 

 myza preusta Fin. ; the maxillary palpi are of the type seen in 

 the Opomyzida? ; the fulcrum is curious, and has an organ in the 

 interior which seems to be some sort of gizzard, or crushing- 

 apparatus. The palpi are relatively not so large as in the 

 Opomyzida? (pi. VIII. figs. 9, 10). 



The Borborida? have characteristic tropin with curious large 

 tracheae, and the paraglossa? are united and without a median 

 division. The maxillary palpi are very marked in some species, 

 but almost all the other parts of the maxilla? have disappeared ; 

 the cardines, with their characteristic joint or hinge, cannot be 

 made out, and only the stipites remain. The large development 

 of the mentum, and the character of the maxillary palpi, bring 

 this family very close to the Ephydridae. The seta? at the base 

 of the labial palpi, which represent the palpigers, are very constant 

 in this family (pi. VIII. fig. 11). 



Group 8 contains but one family, the CEstrida? ; these extra- 

 ordinary flies are quite devoid of any developed mouth-part, 

 two tubercles representing the elaborate structures of the ordinary 

 insect mouth. A small buccal orifice is visible, surrounded by a 

 chitinous ring, which is in some places shortly but thickly haired ; 

 more anteriorly placed are two chitinous arches, which appear to 

 cover another cavity. What these parts homologise with, it is 

 difficult to say, (1) but the tubercles have structures on their 



* 'The Labial and Maxillary Palpi in Diptera,' Trans. Linn. Soc. Lon Ion, 

 Zool., ser. 2, vol. ix., pp. 223-229, figs. 21, 22. 



