14 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 121 



One type was found in the genus Adoxomyia. The mouthparts of 

 the species in this genus are very similar to those found in the larva 

 of Cyphomyia. In addition, the larvae of both genera are known 

 only from wounded or decaying succulents in North America; con- 

 sequently, Cyphomyia and Dicyphoma have been transferred to the 

 Clitellariini (Cyphomyinae of James) along with Adoxomyia. 



A second tribe, the Hermetiini (Hennetiinae of James), has been 

 transferred to this subfamily on the basis of similarities in morpholog- 

 ical and ecological characters of both adults and larvae of Hermetia 

 to the clitellariiue genera Adoxomyia, Cyphomyia, and Dicyphoma. 



The genus Dieuryneura has been placed in this subfamily also but 

 not in either tribe. A comparison of larval mouthparts shows it to 

 be more closely related to the Hermetiini than to the Clitellariini, 

 but a more definite attempt at classification is impossible at this time. 



The larvae of the remaining genera in the Clitellariinae of James 

 are either aquatic or semiaquatic and the mouthparts are similar 

 to the genera originally placed in the Stratiomyinae. These 2 

 facts by themselves give sufficient cause to unite the genera in a 

 single subfamily; in addition, all of the genera except Nemotelus 

 that were removed from the Clitellariinae possess ventral hooks. 

 These curious structures may represent a clinging device for living 

 in fast-flowing water. Stratiomys larvae lack these structures but 

 they are present on larvae of Odontomyia. It is possible that the 

 hooks have evolved tmce but it seems more likely that the genera are 

 more closely related than they were previously thought to be. 



Larvae of Nemotelus pose a special problem. In addition to lack- 

 ing the ventral hooks, the orifice of the spiracular chamber is on the 

 dorsal surface of the last abdominal segment and possesses a cornet 

 of hydrofuge setae as contrasted with the terrestrial larvae that lack 

 this feature and as contrasted wdth other aquatic larvae that also 

 possess a coronet of hydrofuge setae but have the spiracular chamber 

 at the apex of the last segment. This combination of characters is 

 rather unique and provides the basis for elevating this genus to 

 subfamilial status. 



Key to Suborders, Divisions, and Principal Families of Brachycera- 

 Orthorrhapha Based on Larval Characters 



1. Head complete, or the posterior portion with deep longitudinal incisions; 

 mandibles capable of horizontal movement; body consisting of 13 segments 

 in addition to head; with 9 pairs of spiracles . . Suborder NEMATOCERA 

 Head incomplete, frontal region not strongly arched; mandibles capable of 

 vertical movement; body comprising fewer than 13 segments and only ex- 

 ceptionally with as many as 9 pairs of spiracles. 



Suborder BRACHYCERA 2 



