seventeen double spiked arches, instead of twenty-five;
also, the abdominal segments, from the sixth onwards, are supplied
merely with stiff bristles, without a trace of horny spikes. If the
evolution of the various Anthrax flies were better known to 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 crumbles to pieces.
It is slow in coming away; but it comes away all the same, atom by atom.
At long intervals, the method changes. With its crown of awls driven
into the pith, the animal frets and fidgets, sways on the pivot of its
anal armor. The work of the auger follows that of the pickaxe. Then the
blows recommence, interspersed with periods of rest to recover from the
fatigue. At last, the hole is made. The pupa slips into it, but does not
pass through entirely: the head an