362 



Family LBPTIDAB 



In the present paper I have Hmited this family to include only the 

 genera placed in the subfamily Leptinae in Williston's Manual of 

 North American Diptera. This grouping is not a new one, having 

 been used by Brauer and several subsequent vv'riters, and from a 

 phylogenetic point of view it has much to recommend its general 

 adoption. 



FAMII^Y CHARACTERS 



Larva. — Head with a rather small protruded portion ; maxillae 

 not so prominent or so heavily chitinized as in Asilidae, closely re- 

 sembling those of Tabanidae ; maxillary palpi well developed ; man- 

 dibles vertical, parallel, curved, and very long; retracted portion of 

 head with a large arcuate upper covering which is not very heavily 

 chitinized, and 4 elongate rods. Body in terrestrial forms circular 

 in cross-section, distinctly tapered anteriorly, without pseudopods; 

 lateral spiracles on metathorax and abdomen very small; in aquatic 

 forms body slightly flattened and with paired abdominal pseudopods 

 and dorsal and lateral filannents ; anterior spiracles small ; posterior 

 pair large, located, in terrestrial forms, under a single flap-like process 

 or at the base of an upper pair of pointed processes ; in aquatic forms 

 the spiracles are not distinguishable, and there are two rounded, pro- 

 trusive blood-gills on apical segment below the bases of the long 

 terminal appendages. 



Pupa. — Head without projecting thorns ; antennae short, swollen 

 at base, slender apically, directed downward and slightly outward. 

 Thoracic respiratory organs sessile (terrestrial forms) ; wings extend- 

 ing to second or third abdominal segment ; hind legs extending to apex 

 of wings or slightly beyond that point. Abdomen with a transverse 

 series of bristles on each segment, the series becoming stronger 

 tov/ards apex of abdomen. 



Imago. — Robust species with short antennae and stout legs. For 

 characters to distinguish the family from other Brachycera see key to 

 imagines of this division. 



HABITS OF I^ARVAE 



Only one genus known to me is aquatic — Athcri.v. The terrestrial 

 forms are found in rotten wood or in the ground in woods, generally 

 under thick covering of leaves or under decaying logs or tree-stumps. 

 They are predaceous, feeding upon larvae of other insects, and prob- 

 ably also upon worms. The species which I have reared were very 



