NORTH AMERICAN DIPTEEA. 



TABLE OF THE FAMILIES OF DIPTERA. 



1. Flies of a leathery or horny structure, living parasitically in the adult 



state upon warm-blooded vertebrates; head small, either closely 

 united to the emarginate anterior part of the thorax or folding back 

 into a groove upon the dorsum ; mouth-part incomplete, the palpi 

 wanting; legs separated by the broad sternum ; abdomen indistinctly 

 segmentated; claws well developed. Pupipara. ... 48 

 Flies of softer structure, never living parasitically in the adult state 

 upon vertebrates ; head separated from the thorax by a free neck. 2 



2. Antennae many-jointed, often longer than the thorax, the two basal 



joints, only, differentiated, the remaining joints usually distinct ; 

 palpi composed of three or four joints, usually elongate; anal cell 

 rarely closed or narrowed in the margin. Nematocera. . 3 



Antennae rarely as long as the thorax, composed primarily of three 

 joints, the third of which may be simple or complex (that is com- 

 posed of more or less distinct annuli or segments,)* with or without 

 A terminal or dorsal arista or terminal style; anal cell closed before 

 the border, or, distinctly narrowed in the border, or, if of other 

 structure, the antennae composed of three simple joints with or with- 

 out an arista or style; palpi rarely much elongate, composed of 

 from one to three joints, or rudimentary. .... 14 



* To the beginner there will be several families here which will cause 

 doubt; they are especially the Simnlidce, Bibionidce, Orphnephilidce, and 

 some of the Xylophagince. The Simulidce are small, thick-set flies, with 

 the antennas not longer than the head, composed of ten joints, the veins of 

 the wings weak and the neuration incomplete. In the Bibionidce the anten- 

 nae have from nine to thirteen joints closely united, altogether no longer 

 than the thorax; there is no discal cell. Orpkncphila is composed of species 

 not more than three or four millimeters in length ; the antennae are appar- 

 ently three-jointed with a terminal arista; under close examination, how- 

 ever, the third joint will be found to be composed of three segments and 

 the arista of seven. The Xylophaghm will be best distinguished by the 

 complete neuration and the closed or narrowed anal cell. In all cases 

 where the palpi are found to be composed of four joints the species may be 

 unhesitatingly placed among the Nematocera. 



1 



