DIPTERA. 5 



the lower and anterior part of the head. Labium ending in a thicker 

 bilobed piece (the "labella"), traversed internally by radiating tracheae; 

 sheathing the mandibles and maxillae when these are developed. La- 

 drum closing this sheath above, embracing the lingua. Palpi attached 

 to the base of the maxilla, or, if these are wanting, seated on the prop 

 of the proboscis. Pro thorax very small, immovably joined to the meso- 

 thorax, which is the largest piece. Wings and halteres developed, 

 almost always. Abdomen at the base much more slender than the 

 thorax, its dorsal segments at least distinct (4 or more). Legs of 

 each pair close together, and the posterior two pairs to each other ; the 

 fore pair usually farther from the intermediate. Ungues and onychia 

 symmetrical pairs. 



PROBOSCIDEA. 



rwith distinct joints, at least 6, 

 g I (usually more than 10) . . . 1. NEMOCERA. 



<! Lwith 3 to 10 joints; after 

 the 3d closely united, or 

 abruptly slighter. Pos- ("branched or inter- 

 terior veins of the wing \ laced, more or less 2. BRACHYCERA. 



I simple, detached, 

 and very faint . 3. HYPOCERA. 



NEMOCERA, Latr.; Macg.-, &c. 



Antennae articulis discretis saltern sex saepius decem et ultra. 

 Palpi plerumque deflexi, articulis pluribus exsertis. 

 Areola analis in marginem posteriorem aperta. 



Add. Antennas plerumque capite longiores, graciles, filiformes aut 



setaceae. 



Alulae scutellares obsoletse ; 

 Lob us axillaris quoque ut plurimum. 

 Alae venis multimodis, nee facile in typum redigendis. 

 Ocelli saepe desunt. 

 Ungues haud raro denticulati. 



BRACHYCERA, Macq. 

 Antennae articulis post tertium connatis, vel extremis (1-3) minis 



attenuatis. 



Palpi porrecti, aut proboscidi incumbentes, quasi exarticulati. 

 Areola analis ferme clausa. 

 Venae posteriores ramosae vel anastomosi connexae. 



Figure usually stouter and more compact than in Nemocera, and the 

 head broader, and more vertical. Cavity of the mouth at the underside 



