May, 1953 
should be avoided, as they eventually make 
the specimens so soft that the parts will not 
hold together. Glycerin also eventually 
turns mayflies almost pitch black. Formalin 
hardens specimens so much that it should 
not be used. 
Collections of specimens in alcohol, if in 
vials with cork stoppers, will almost certainly 
have many losses due to evaporation of the 
alcohol. The use of red rubber stoppers in 
the vials will greatly reduce evaporation, 
but, even with the best care, specimens will 
occasionally be found to have dried out. 
Many dried specimens can, however, be 
partially restored by careful treatment with 
trisodiumphosphate (Van Cleave & Ross 
1947). This method of restoration often 
makes it possible to identify nymphs which 
formerly had to be discarded. 
Study Preparations 
For a study of the male genitalia, slide 
mounts of these structures must be pre- 
pared with special care. I have used the 
following procedures in material examined 
in this report. 
The entire mayfly is first relaxed and 
the caudal filaments removed but saved in 
case it should be necessary to study them 
later. Then the apex of the abdomen is 
cut off and cleared in cold 10 per cent 
potassium hydroxide for a period of 6 to 
12 hours. After this treatment the dis- 
section is placed in distilled water and any 
undisintegrated muscle or abdominal con- 
tents are carefully teased out with fine 
dissecting needles. The preparation is 
transferred first to 50 per cent ethyl alcohol 
and then through two changes of 70 per 
cent alcohol, being left in each not less than 
15 minutes. A few drops of acidulated acid 
fuchsin are added to the last change of 70 
per cent alcohol, and after a minimum of 
15 minutes the preparation is removed to 95 
per cent alcohol. In this alcohol the tenth 
tergite and the bases of the caudal filaments 
are dissected off so that they will not obscure 
the structure of the penis lobes in the finished 
slide. The genitalia are then left in the 95 
per cent alcohol until all excess stain has 
been washed away. 
The preparation is mounted, directly from 
the 95 per cent alcohol, in balsam. The 
latter is a special medium made by diluting 
standard, filtered Canada balsam with 10 
per cent turpentine. A small drop of this 
Burks: THE MAyr iss oF ILLINOIS 13 
medium is put on the slide and the stained 
genitalia preparation placed in it; the trans- 
ferring is done with a hooked dissecting 
needle, not a pipette. This turpentine 
mounting medium dries slowly enough to 
allow ample time for orienting the dissection 
correctly on the slide. Each specimen is 
mounted with the genital forceps down, care 
being taken to mount all dissections as 
nearly as possible in the same position, for 
the structures of the penis lobes of a single 
species may look quite different if seen 
from different angles. The preparation is 
then placed in a dust-tight box to dry. It 
should be examined at intervals over a 
period of several days and the dissection 
straightened, if necessary, with a dissecting 
needle. The coverslip is not put on until 
the preparation is almost completely dry. 
In this paper, the drawings of the male 
genitalia were, except in Leptophlebiidae, 
made from the dorsal aspect, that is, with 
the penis lobes above the genital forceps. 
In the Leptophlebiidae, the genitalia were 
drawn from the ventral aspect, so as better 
to show the ventral appendages of the penis 
lobes. 
In many instances, it is necessary to make 
dry mounts of the adult wings so that the 
venation can be studied critically. If the 
adult specimen is preserved in alcohol, the 
mount can be made directly, but, if the 
specimen is dry, it must first be relaxed. 
The wings from the alcoholic specimen or 
relaxed dry specimen are then carefully 
dissected off with dissecting needles or 
knives. As these wings are extremely 
fragile, the operation must be done with 
great care. The wings can easily be re- 
moved by severing the muscles at the base 
of each wing. 
The detached wings are carefully washed 
in a watchglass containing 70 per cent alcohol 
to remove any dust or debris. It may be 
necessary to use a fine camel’s-hair brush 
to remove all the dust; the brushing must 
be done very carefully, else the fragile 
wings will be torn. 
Next a drop or two of 70 per cent alcohol 
is placed on a clean microscope slide and the 
wings are floated onto it. They should be 
spread and arranged symmetrically, dis- 
secting needles being used for the manipu- 
lation. Then, before the alcohol evaporates, 
a square, No. 1 thickness coverslip is put 
on. Coverslips three-fourths inch or seven- 
