196 A. L. MELANDER. 



on this family, aud distributed among the genera treated in this 

 paper, seventy-four, or nearly forty per cent, are represented in 

 the collection. Besides these described species we have discovered 

 eighty new forms. The fact alone, that in a collection of insects, 

 even as superficial as this one necessarily is, and representing a 

 family so recently revised, more than half of the species are new 

 shows the enormous work yet to be done in systematic dipterology. 

 Five genera, previously unknown from this continent, are here 

 added, and in addition four new genera are established. Another 

 genus is erected, but as the insect represented was taken in Brazil, it 

 does not properly come within the confines of this paper, and has 

 therefore been added as a foot-note. Several changes in synonymy 

 /have also been effected. As an interesting note in this connection 

 attention may be called to the fact that thirty-one years ago only 

 eighteen genera were known to Dr. H. Loew * as occurring in North 

 America, as compared with the thirty-seven now given. Will the 

 genera again be doubled in the next thirty years? 



In this paper I have attempted to gather the descriptions made 

 by former observers, and to reduce all to English, in some cases 

 abbreviating the original. The analytical keys are in large part 

 based upon Mr. Schiner's excellent work on the Austrian Flies, a 

 work which has been partially followed also in preparing the generic 

 diagnoses. 



The family Empididse includes rather small to moderate sized 

 flies. The smallest species of the family belong to Drapetis and 

 measure only 3^3 inch. The largest forms reach a length of J inch. 

 With the exception of a few brilliant, metallic Mexican species, 

 most of the species are very modest in coloration, a sombre gray- 

 black being the most prevalent color. 



Their habitus is generally the following : an almost spherical head 

 with large eyes, generally long pointed antennae and a slender pro- 

 boscis, directed either forward or downward ; a slender body, the 

 thorax large, the abdomen long, terminating sharply in the female 

 and more or less club shaped in the male ; the legs generally very 

 long and slender, especially the hinder pair, though not so notice- 

 ably long as in the Dolichopodid flies. 



The structural characters of the family present a wide range of 

 variation. Perhaps the principal morphological character of a dip- 



* Mouogr. Dipt. N. Am., No. 1. 



