400 



ment and well separated, being sessile or nearly so in most species, 

 only rarely elevated ; this segment frequently has 4 short terminal 

 protuberances. 



Pupa. — The head very rarely has 2 long, strongly chitinized pro- 

 tuberances, and the antennae are short, directed downward and slight- 

 ly outward, with 2 hairs on slight elevations at bases, and sometimes 

 2 or 3 short, compressed teeth on basal half. The proboscis in the 

 Empididae that I have seen is much elongated, projecting much far- 

 ther between the wings than in Dolichopodidae. Brauer has indicated 

 that the former family possesses sessile thoracic respiratory organs, 

 while the latter has these organs pedunculate and slender. I have 

 reared one empid that has the type of respiratory organs which he 

 ascribes to the Dolichopodidae, and this invalidates the structure of 

 the respiratory organs as a differentiating character in these families. 

 The proboscis, as above indicated, may prove useful in separating 

 the families, but I suspect that Ocydromyia and several other genera 

 of Empididae that have the proboscis short, can not be separated from 

 Dolichopodidae by that character. 



Imago. — Most species of Dolichopodidae are distinguishable at a 

 glance from other Orthorrhaphae by their bright metallic blue or 

 green color and their slender elongate legs. The few genera that are 

 dull in color may be readily separated by their different habitus. 



The Empididae are usually blackish or brownish slender species 

 with elongate legs, those of the female frequently possessing a fringe 

 of scale-like hairs on some or all of their tibiae or femora. The pro- 

 boscis in the great majority of genera in this family is elongate, slen- 

 der, and fitted for piercing. For synoptic characters see key to 

 imagines of Brachycera. 



Family EMPIDIDAE 



FAMILY CHARACTERS 



Larva. — The labial plates and the longitudinal rods of the head 

 meet angularly, so that in profile they appear bent. The labium con- 

 sists of 2 arcuate bands, which are contiguous and form an angle 

 anteriorly; the mandibles appear in the form of a lunate plate, as 

 shown in Figures 4 and 6, Plate LVII. The antennae are well de- 

 veloped, consisting of 2 joints. The posterior spiracles are situated 

 upon the last segment, well separated and occasionally slightly ele- 

 vated ; the last segment is rounded or has a slight protuberance be- 

 low at tip. 



