gives the nymph a
purchase on the wall of its gallery as the work proceeds. Thus anchored
on a host of points, the stern pioneer is able to hit the obstacle
harder with its diadem of awls. Moreover, to make it more difficult for
the instrument to recoil, long, stiff bristles, pointing backwards,
are scattered here and there among the climbing belts. There are some
besides on the other segments, both on the ventral and the dorsal
surface. On the flanks, they are thicker and arranged as it were in
clusters.

The sixth segment carries a similar belt, but a much less powerful one,
consisting of a single row of unassuming thorns. The belt is weaker
still on the seventh segment; lastly, on the eighth, it is reduced to a
mere rough brown shading. Commencing with the sixth, the rings decrease
in width and the abdomen ends in a cone, the extremity of which, formed
of the ninth segment, constitutes a weapon of a new kind. It is a sheaf
of eight brown spikes. The last two exceed the others in length and
stand out from the group in a double terminal plowshare.

There is a round air hole in front, on either side of the thorax, and
similar stigmata on the flanks of each of the first seven abdominal
segments. When at rest, the nymph is curved into a bow. When about to
act, it suddenly unbends and straightens itself. It measures 15 to 20
millimeters long and 4 to 5 millimeters across.

Such is the strange perforating machine that is to prepare an outlet
for the feeble Anthrax through the Mason bee's cement. The structural
details, so difficult to explain in words, may be summed up as follows:
in front, on the forehead, a diadem of spikes, the ramming and digging
tool; behind, a many bladed plowshare which fits into a socket and
allows the pupa to slacken suddenly in readiness for an attack on the
barrier which has to be demolished; on the back, four climbing belts, or
graters, which keep the animal in position by biting on the walls of the
tunnel with their hundreds of teeth; and, all over the body, long, stiff
bristles, pointing backwards, to prevent falls or recoils.

A similar structure exists in the other species of Anthrax with slight
variations of detail. I will confine myself to one instance, that of
Anthrax sinuata, who thrives at the cost of Osmia tricornis. Her nymph
differs from that of Anthrax trifasciata, the Anthrax of the mason bee,
in possessing less powerful armor. Its four climbing belts consist of
only fifteen to