Sept., I9I3-] MeLANDER: SYNOPSIS OF DiPTERA. 227 



grouped a number of characters that are correlated in the specimens 

 before me. The descriptions of the older authors are often silent 

 regarding some of these characters, e. g., the color of the calypteres, 

 the number of fronto-orbitals or dorsocentrals, the details of venation, 

 etc. Rather than encumber the key with repeated statements that the 

 correlation of characters is based on the specimens studied and is not 

 known to hold in those species that I do not possess, I have left it 

 for the list of localities to indicate those species I have, and those 

 concerning which there might be doubt. The localities include, in 

 addition to places already recorded, the localities of specimens in the 

 collections of Dr. Garry deN. Hough, now at Chicago University, 

 and of Professor J. M. Aldrich. Those places from which I possess 

 specimens are marked with a star (*). 



While in the preparation of this paper I have depended almost 

 entirely on the material in my own collection, still I wish here to 

 express my appreciation of the good-will of my friend, Professor 

 Aldrich, who has always been ready to share his collection and library 

 whenever asked. For some years our common interest in these flies 

 has brought out many inductions that working independently we might 

 have missed. Mr. Charles W. Johnson has also generously sent his 

 species of Spilochroa for examination. 



The work on these small flies has practically all been done under 

 the Zeiss prism binocular microscope, using mainly the a^ objective 

 and number i ocular. While a magnification of but thirty-one diam- 

 eters is thus produced, the clearness afforded by stereoscopic vision 

 has certainly repaid the extra labor of centering the specimens in the 

 field of the microscope. Indeed, the hand lens has been practically 

 discarded as incapable of resolving such difficult characters as the 

 fracturing of the costa or the boundaries of the sclerites of the head. 

 In this connection I wish to call attention to the insect holders, made 

 by the Spencer Lens Company and the Ernst Leitz Company, a ball 

 and socket attachment that easily enables a specimen to be viewed in 

 any position under the microscope. For extra illumination needed in 

 deciding difficult points I have attached over the field of the micro- 

 scope a small low-voltage tungsten automobile headlight. By placing 

 the lamp beyond the focal point the parabolic reflector concentrates 

 the light on the specimen. A step-down transformer furnishes low 

 voltage and a small rheostat regulates the intensity of illumination, 



