98 NORTH AMERICAN DIPTERA. 



In the arrangement of the families, it will be observed that 

 I have changed the order, placing the Calyptratae last, an 

 arrangement which I believe coincides better with the degree 

 of specialization of the insects. 



Very much remains to be done in the study of this wide 

 group, not only in America, but throughout the world. As 

 throughout the order, especial care should be taken in the 

 identification of East Indian, Australian and African genera 

 among the forms occurring in Central and South America and 

 the West Indies. In the study of the Calyptratae, especially 

 the Tachinidse, there has been an extraordinary activity during 

 the past few years. I confess myself unable to straighten 

 out the maze in which they seem to be. Professor Townsend 

 has given to them the most and best study and is the best 

 authority we have on their classification. 



TABLE OF FAMILIES. 



1. Tegnlaj large; first posterior cell narrowed or closed; front of male 



always narrower than that of the female. .... 2 



Flics withont^tt' the above characters.* ...... C> 



2. Mouth-parts rudimentary or wanting. .... Gi^STRin.i:. ^3o 

 Mouth-parts functional. ......... •! 



8. Arista of antennae bare or very slightly pubescent. . Taciu^idm.^v ^ 



Arista plumose or distinctlj' pubescent. ..... 4 



4. Arista bare on the distal part; dorsum of abdomen rarely bristly on the 



anterior part Sakcoi'hagid.i;. J 3^ 



Arista plumose or pubescent to the tij). ...... 



5. Dorsum of abdomen bristly; third joint of antcnnne usually not eloiii 



gated; legs usually long. ...... DEXI^).^•:./4^v^ 



Abdominal segments without bristles, except more or less near the tip ; 



legs not elongated. Musciimc sens. str. /4^0 



6. Tegula2 large; thorax with a complete transverse suture; first posterior 



cell* never narrowed ; front of male narrower than that of the female 



Antiiomyid.e. /^^ 



*In Gastrophllns {(Estrida), the first posterior cell is not narrowed and the 

 tegulae are rather small; the genus will be distinguished by the rudimen- 

 tary mouth-j)arts. 



