142 Journal New York Entomological Society. C^'oi. xxx. 



balsam in the usual way. If care is taken to support the cover glass 

 sufficiently the mount will not be distorted or compressed. 



This paper is intended solely as a study in taxonomy, detailed fig- 

 ures of mouth parts are therefore not given. It is probably true that 

 taxonomic characters may be found in them but- without having a 

 number of species within the same genus for comparison it would 

 be difficult to determine upon what part the intensive study should 

 be placed. This is particularly true in genera like Stratiomyia and 

 Odontomyia each of which contains a number of species. Students 

 interested in a study of the homologies of the mouth parts are re- 

 ferred to the most excellent paper of Prof. J. C. H. de Meijere 

 (1916) as well as to the earlier work of F. Brauer (1883). 



An interesting feature brought out in this study is the fact that in 

 a number of details of structure, armature of body, and mouth parts, 

 the earlier instars differ from the final one. In all larval stages the 

 body bristles are for the most part spiculate and more or less flattened. 

 In the European Pachygaster atra, and in the penultimate instar of 

 Microchrysa polita they are also slightly clavate. 



In the following key I have not indicated subfamily limits. Our 

 knowledge of the early stages of this family is still too fragmentary 

 to attempt broad generalizations. Xylomyia is here included. 

 Whether this genus is to be referred to the Stratiomyiidae or the 

 Leptidse is still an open question. When emerging, the imago of the 

 members of this genus withdraws the pupal skin, at least in part, 

 from the puparium, while in the Stratiomyiidae the pupal skin re- 

 mains wholly within it. Other characters of larvae and adult also 

 indicate Leptid affinities. 



A. Last abdominal segment with a tuft of soft plumose or pubescent hairs; 



aquatic or semiaquatic species. 



B. Caudal margin of the ventral side of at least the penultimate abdominal 



segment with a pair of stout, curved thorns or hooks ; antennae over 



three times as long as broad ; body more or less striped. 



C. Antennae placed at the latero-anterior angles of the head ; no stout 



spines in a transverse row on the venter of each abdominal 



segment Odontomyia. 



D. Species 20—30 mm. long; with a wide, paler, compound dorsal 

 vitta made up of four pale and three brownish stripes ; lateral 



margins dark ; antennae distinctly curved cincta. 



DD. Species 16 mm. long or less. 



