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
maxillæ, 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 (maxillæ) which seem to be
exclusively used on all ordinary occasions in making perforations. The
inner edges of these maxillæ 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. Æsculus glabra. 7. Lonicera involucrata. 8. Caragana
arborescens. 9. Andromeda Japonica. 10. Buddleia Japonica. 11.
Mertensia Virginica. 12. Rhododendron arborescens. 13. Corydalis
bulbosa.]