us, the number of these arches would, I believe, be of great
service to entomology in the differentiation of species. I see it
remaining constant for any given species, with marked variations
between one species and another. But this is not my business: I
merely call the attention of the classifiers to this field of
study and pass on.

About the end of May, the coloring of the nymph, hitherto a light
red, alters greatly and forecasts the coming transformation. The
head, the thorax and the scarf formed by the wings become a
handsome, shiny black. A dark band shows on the back of the four
segments with their two rows of spikes; three spots appear on the
two next rings; the anal armor becomes darker. In this manner we
foresee the black livery of the coming insect. The time has
arrived for the pupa to work at the exit gallery.

I was anxious to see it in action, not under natural conditions,
which would be impracticable, but in a glass tube in which I
confine it between two thick stoppers of sorghum pith. The space
thus marked off is about the same size as the natal cell. The
partitions front and back, although not so stout as the
Chalicodoma's masonry, are nevertheless firm enough not to yield
except to prolonged efforts; on the other hand, the side walls are
smooth and the toothed belts will not be able to grip them: a most
unfavorable condition for the worker. No matter: in the space of
a single day, the pupa pierces the front partition, three quarters
of an inch thick. I see it fixing its double plowshare against
the back partition, arching into a bow and then suddenly releasing
itself and striking the plug in front of it with its barbed
forehead. Under the impact of the spikes, the sorghum slowly