424 ANNUAL REPORT SMITHSONIAN INSTITUTION, 1926 
which is usually stronger in the females, and in the males often is 
combined with a wholly different sweetish scent. An example is 
our common milkweed butterfly. 
A rank and disagreeable odor is in certain species common to 
both sexes when freshly dead, though not in life. 
Some butterflies, like the Old World purple emperors, the various 
species of Charaxes, and certain swallowtails, which are immoder- 
ately fond of excrement or of rotting flesh, occasionally proclaim 
their preferences in the odors they exhale, though these do not 
properly arise from them themselves. 
APPARENTLY SCENTLESS BUTTERFLIES 
There are certain of our common butterflies with a great de- 
velopment of scent scales in which as yet no odor has been found. 
One of the most conspicuous of these is Cercyonis alope (fig. 35, 
pl. 6). This at any rate must have an odor, though I have been 
quite unable to find any in either sex. Mr. Scudder also was unable 
to find any odor in the three species of @’neis, of the same family, 
examined alive by him. So far I have found no odor in our com- 
mon orange-tip (Anthocharis genutia, figs. 10, 11, pl. 2), though it 
probably has one. 
THE ODORS OF BUTTERFLIES BY GROUPS 
Pierids —Of all the larger groups of butterflies the pierids are 
the most remarkable for the very general occurrence and the 
strength and uniformity of scent in males. Its presence has now 
been well established in about 80 different species. Furthermore 
it has been found among these butterflies that closely allied forms 
may have quite different scents. One of the best examples of this is 
found in our common whites. 
Mr. Scudder wrote that among our common whites the males of 
the common cabbage butterfly (Pieris rape, fig. 1, pl. 1) “have a 
very faint but pleasant odor, difficult to detect. I have sometimes 
done so, but at other times have been unable to perceive it, on rub- 
bing the scales of the upper surface of the wings and immediately 
smelling the fingers.” More recently Doctor Dixey, Mr. Longstaff, 
and others have determined from studies made in England that 
the males of this butterfly have a scent, though it is neither so strong 
nor so distinctive as that of the green-veined white (P. napi, fig. 2, 
pl. 1). Originally Doctor Dixey compared the scent to that of 
mignonette (Reseda odorata), but Mr. Longstaff says that Prof. 
Selwyn Image’s comparison to sweetbriar is better, though that, is 
not exact. 
