g slightly on the upper surface; and its
double structure is so difficult to perceive that at first we take it
for the animal's head alone, though it includes both the head and the
prothorax, or first segment of the thorax.

The mesothorax, or middle segment of the thorax, which is two or three
times larger in diameter, is flattened in front and separated from the
nipple formed by the prothorax and the head by a deep, narrow, curved
fissure. On its front surface are two pale red stigmata, or respiratory
orifices, placed pretty close together. The metathorax, or last segment
of the thorax, is a little larger still in diameter and protrudes.
These abrupt increases in circumference result in a marked hump, sloping
sharply towards the front. The nipple of which the head forms part is
set at the bottom of this hump.

After the metathorax, the shape becomes regular and cylindrical, while
decreasing slightly in girth in the last two or three segments. Close to
the line of separation of the last two rings, I am able to distinguish,
not without difficulty, two very small stigmata, just a little darker
in color. They belong to the last segment. In all, four respiratory
orifices, two in front and two behind, as is the rule among Flies. The
length of the full sized larva is 15 to 20 millimeters and its breadth 5
to 6.

Remarkable in the first place by the protuberance of its thorax and
the smallness of its head, the grub of the Anthrax acquires exceptional
interest by its manner of feeding. Let us begin by observing that,
deprived of all, even the most rudimentary walking apparatus, the animal
is absolutely incapable of shifting its position. If I disturb its rest,
it curves and straightens itself in turns by a series of contractions,
it tosses about violently where it lies, but does not manage to
progress. It fidgets and gets no farther. We shall see later the
magnificent problem raised by this inertness.

For the moment, a most unexpected fact claims all our attention. I refer
to the extreme readiness with which the Anthrax' larva quits and returns
to the Chalicodoma grub on which it is feeding. After witnessing flesh
eating larvae at hundreds and hundreds of meals, I suddenly find myself
confronted with a manner of eating that bears no relation to anything
which I have seen before. I feel myself in a world that baffles my old
experience. Let us recall the table manners of a larva living on prey,
the Ammophila's for instance,