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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 writers, and from a 

 phylogenetic point of view it has much to recommend its general 

 adoption. 



FAMILY 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 filaments ; 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 LARVAE 



Only one genus known to me is aquatic — Athcrix. 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- 

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



