Gr. F. Ferris and F. R. Cole 1 79 
of its characters can definitely be determined. A review of the existing des- 
criptions shows that in almost all cases this portion of the body has been passed 
over with little or no mention. Yet an examination of the material available 
to us has shown that the abdomen frequently presents characters that we 
believe to be of very great usefulness. 
\\ e are consequently presenting this paper more as a contribution to the 
methodology of the study of the Hippoboscidae than for any other reason, 
although in its inception it was intended merely for the description of a few 
new and little known species. We are taking advantage of the opportunity 
to figure and give notes upon all the species that are available to us for study. 
Technique. 
In the course of its development the study of practically all the ectoparasitic 
groups of insects has passed through certain fairly well-defined stages. Begin¬ 
ning with pinned material, even in those groups the members of which are the 
most fragile, it has progressed through various types of inadequate preparations 
resulting finally in the development of a specialized technique for the production 
of microscopic preparations m the making of which a considerable degree of 
care and skill is necessary. 
In the preparation of slide mounts of Hippoboscids we have utilized the 
following procedure. In the case of winged specimens the wings are detached 
and mounted directly. The body is boiled in a 10 per cent, solution of caustic 
potash until the contents are entirely liquefied. It is then transferred to water, 
judiciously placed slits are made in it and the contents carefully pressed out. 
In the case of these insects this is a bit difficult because of the highly developed 
network of tracheae within the body. The specimen is then transferred to 
95 per cent, alcohol for a few minutes, then to carbol-xylene and then mounted 
in balsam. In most cases it is desirable to support the cover-glass on bits of 
broken glass in order to avoid distortion of the specimen. 
There are certain very definite disadvantages in this method. It is rather 
difficult to avoid the accidental removal of more or less of the vestiture of 
setae and some distortion of the body is almost inevitable. The development 
of a certain amount of skill on the part of the preparator, however, will reduce 
these disadvantages to a minimum. We cannot consider that objections to 
the method based solely upon the necessity for acquiring this skill and the 
time consumed are valid. The histologist does not complain of the time spent 
in acquiring the skill in technique that is necessary for the accomplishment 
of his aims. 
A further objection that the colours of the specimen are lost by this method 
of preparation is in part valid. However, what we have seen has not led us 
to accord any special respect to colour as a taxonomic criterion in this group 
and in any case colour notes can be taken before the specimen is prepared. 
The general colour, whether light or dark, can be determined well enough from 
the mounted specimens as can the colour of setae. 
12—2 
