om the same kind of flower both in the normal way and by
perforating.

The chief perforators of flowers, in this part of the continent at
least, appear to be some kinds of humble bees (Bombus) and carpenter
bees (Xylocopa). These insects have developed an unerring instinct as
to the proper point to perforate the corollas from the outside, in
order to readily get at the nectar. The holes made by the humble bees
and by the carpenter bees are usually quite different and easily
distinguished.

The humble bees have short, stout, blunt jaws, ill adapted for
cutting, and the perforations made by them are apparently always
irregular in shape, and have jagged edges. It has been stated that the
humble bees often bore through the tubes of their corollas with their
maxillae, but in all cases observed by me the mandibles were first
brought into use in effecting an opening. The noise caused by the
tearing is often audible for a distance of several feet.

The true jaws of the carpenter bees are not any more prominent or
better adapted for making clean-cut perforations than those of the
humble bees; but behind the jaws there is a pair of long,
sharp-pointed, knife-like, jointed organs (maxillae) which seem to be
exclusively used on all ordinary occasions in making perforations. The
inner edges of these maxillae are nearly straight, and when brought
together they form a sharp-pointed, wedge-shaped, plow-like instrument
which makes a clean, narrow, longitudinal slit when it is inserted in
the flower and shoved forward. The slits made by it are often not
readily seen, because the elasticity of the tissues of some flowers
causes them to partially close again. When not in use the instrument
can be folded back, so that it is not conspicuous. The ordinary
observer usually sees no difference between the humble bees and the
carpenter bees, but they may be readily distinguished by a little
close observation.

[Illustration: THE PERFORATION OF FLOWERS.

1. Xylocopa and heads of male and female. 2. Bombus and head. 3.
Dicentra spectabilis, showing punctures. 4. Ribes aureum. 5. Ligustrum
Ibota. 6. AEsculus glabra. 7. Lonicera involucrata. 8. Caragana
arborescens. 9. Andromeda Japonica. 10. Buddleia Japonica. 11.
Mertensia Virginica. 12. Rhododendron arborescens. 13. Corydalis
bulbosa.]

No doubt, in some of the recorded cases of perforations, carpenter
bees have been mistaken for humble bees. The heads of all our Northern
humble bees are