174 Annals Entomological Society of America  [Vol. XIV, 
aspect shows almost as many of the features. In a good many 
cases both views are presented. The drawings have been out- 
lined with the aid of a camera lucida, the outlines then proved 
under the binocular and finally again examined under higher 
powers of the compound microscope as they were inked. The 
writer believes that the drawings given herewith, which show 
the parts all assembled, will make it easily possible for any 
taxonomic worker to use these characteristics in determining 
and defining species. When isolated appendages alone are 
figured, the tyro finds great difficulty in determining what part 
is represented and what view of it is figured. 
METHODS OF WORK. 
I am so much interested in seeing the general adoption of 
the genitalic characters as an aid in the characterization of 
species that I venture to describe, somewhat fully, the methods 
I have found useful in preparing these parts for study, in the 
hope that even the isolated worker, not accustomed to lab- 
oratory methods, may not hesitate to make use of the valuable 
characters to be found in the terminal appendages of these flies. 
Every worker will, of course, develop his own particular 
methods of procedure, and there is little if anything new in the 
methods which I have used. But it will at least serve as a 
starting point, for it has enabled me to prepare hundreds of 
these parts without the loss of, and almost without damage to, 
a single one. 
Three kinds of material will ordinarily fall to one’s hands 
for use: freshly killed specimens, alcoholic ones and dried, 
pinned ones. All of them are valuable: indeed, for the chitinous 
parts with which the systematist is concerned, I believe the 
pinned specimens are as good as fresh ones, although the worker 
would do well to secure fresh material whenever possible as a 
check upon preserved material. 
(1). In any case I always first pin the specimen and then attach to the pin 
a serial number which is also placed (together with the name of the insect and 
any other data) ina notebook. Personally I use the space provided in most slide 
boxes, putting the number and name of the insect opposite the space which will 
eventually receive the prepared slide of the genitalia. 
(2). Ifthe material is freshly killed, this step is to be omitted. With material 
which is set, however, the next step is to relax the insect by placing in a moist 
chamber or relaxing jar. The length of time required for this process will vary 
with the species, the degree of chitinization of the specimen and the length of time 
it has been killed. Asa rough average, I have found about thirty-six hours to be 
