317 



— Segments without lateral notch 4 



4. Bristles on dorsum very short, arranged in groups of 3-4; lateral 



bristles arranged similarly, two such groups on each side of each 

 segment Beridinae (p. 331). 



— Bristles on dorsum and lateral margins long, not in groups 5 



5. Head much elongated, the portion anterior to eyes distinctly longer 



than its greatest width ; antennae of moderate length, apical por- 

 tion slender ; the 6 conspicuous hairs on dorsal surface of thoracic 

 and abdominal segments not in an almost straight transverse 

 series, the median pair close to anterior margin and very much 

 longer and stronger than the 2 lateral pairs, which are close to 

 posterior margin; thorax and abdomen without long decumbent 

 hairs Genus inccrtus 2 (p. 345) . 



— Head not much elongated, the portion anterior to eyes about as long 



as its greatest width ; or if the head is elongated the hairs on ab- 

 domen are in straight or almost straight transverse series 6 



6. Very large robust species, over 18 mm. in length ; antennae of mod- 



erate length, apical portion stout; eyes moderately prominent; 

 head distinctly narrowed immediately behind eyes, almost paral- 

 lel-sided; thoracic and abdominal segments densely covered with 

 decumbent lanceolate hairs Clitellarhnae, pt. 



— Smaller species, 10-12 mm. in length at most ; antennae very small ; 



eyes very prominent 7 



7. Thoracic segments 1 and 2 each with a smooth plate on dorsum ; 



apical segment with a transverse series of short teeth near base 



on ventral surface which are directed caudad 



Xylomyiinae (p. 340) . 



— Thoracic segments without smooth plate on dorsum 8 



8. Bristles slightly clubbed with the exception of some of those on 



head and those on apical segment Gc7ius incertus 3 (p. 345). 



— Bristles tapered to a point, not clubbed 9 



9. Robust species; dorsum distinctly striate; head short and broad. . . 



Geosarginae (p. 331) . 



— Slender species ; dorsum unicolorous, brown or testaceous ; head long 



and slender Pachygasterinae (p. 334). 



Subfamily STRATIOMYIINAE 



SUBFAMIIvY CHARACTERS 



Larva and Puparmm. — Head elongate, armed as in Figures i and 

 2, Plate XLVIII; antennae well developed; maxillae very elaborate, 

 the palpi well developed; mandibles weakly chitinized, the teeth slen- 

 der. Body with rather weak armature, sometimes with scale-like 

 hairs on dorsum, and in Odontomyia with strong thorns (2 or 4) on 

 posterior margin of penultimate, or of both penultimate and ante- 



