ANNALS 



The Entomological Society of America 



Volume IX DECEMBER, 19 16 Number 4 



NOTES ON NORTH AMERICAN DROSOPHILIDAE WITH 

 DESCRIPTIONS OF TWENTY-THREE NEW SPECIES. 



A. H. Sturtevant, Columbia University. 



The writer has in preparation a comprehensive treatment 

 of the North American species of Drosophila and closely related 

 genera. This paper is not yet ready for publication ; but there 

 are several unnamed species that are being used as laboratory 

 animals, so it has seemed advisable to put out a preliminary 

 paper describing these and other new forms, and revising the 

 names of a few additional species. 



In the following descriptions there are a few terms that 

 will need explanation. The "number of rows of acrostichal 

 hairs" is to be counted just in front of the anterior pair of 

 dorsocentral macrochaetas. The "costal index" is the number 

 obtained by dividing the length of the second section of the 

 costa by that of the third section; the "4th vein index" is 

 obtained by dividing the length of the ultimate section of the 

 fourth vein by that of the penultimate section; the "5x index" 

 is obtained by dividing the length of the last section of the fifth 

 vein by the length of the posterior cross- vein; the "4c index" 

 is obtained by dividing the length of the third section of the 

 costa by that of the penultimate section of the fourth vein. 

 These indices are somewhat variable, but nevertheless are 

 sufficiently characteristic to be valuable aids in classification. 

 I hope later to publish some detailed data on their variability. 



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