INTRODUCTION 37 
al 
proportions. Pollenia rudis also varies widely in eye size, but I 
am unable to find characters for separating distinct segregates. 
TECHNIQUE 
Since the male genitalia are diagnostic in many species, it is 
usually necessary to relax dried specimens in order to observe and 
study the various parts. Internal structures are seen to best ad- 
vantage in fresh material placed in proper fixing and killing 
solutions. The following technique applies only to the external 
sclerotized structures of the male and female. Relaxing of such 
specimens may be accomplished in several ways, but the method 
which I find most satisfactory requires merely a deep glass 
evaporating dish, a piece of cork, and a towel or two. The dried 
specimens are pinned to the cork, which is then placed in the 
evaporating dish; the towels are saturated with water, folded, 
and then placed over the top of the dish. Even the oldest and 
driest of specimens may be fully relaxed in from 24 to 48 hours. 
When the specimens dry, they usually retain all the color and 
pollinosity existing before treatment. There is little or no op- 
portunity for specimens to become moldy during relaxing be- 
cause both the dish and the towels may be sterilized frequently 
and the cork can be changed as desired. 
In nearly 120,000 male specimens relaxed in this way, only a 
very small percentage became damaged and these because of 
stain due to the presence of grease. This grease was removed with 
varying success by placing such specimens in ether or chloro- 
form for a day or two. Under this treatment they usually re- 
gained their former appearance. 
In certain instances when a hurried identification of a dry 
male specimen is desired one of two methods may be employed 
to relax the genitalia. Ammonia water may be applied to the tip 
of the abdomen with a camel’s-hair brush at 10-minute intervals 
until the parts have softened; this will usually allow the genital 
parts to be removed, often without damage to the rest of the 
specimen. The hazard to the wings and legs, however, is great, 
and the abdomen is sometimes broken during the process. If a 
specimen is of no particular value, the abdomen may be re- 
moved completely and placed in boiling water until the parts 
have relaxed. In some eases such abdomens can be dried in alco- 
hol and ether, then glued back in place upon the specimen. 
In order to pull the male genitalia into view without breaking 
the specimen or spoiling it during the process of extraction, 
a set routine has been developed. The relaxed specimen is 
removed from the relaxing jar and gently but firmly held be- 
