So it is with the nests of birds, which vary partly in dependence on the situations chosen, and on the nature and temperature of the country inhabited, but often from causes wholly unknown to us.

Audubon has given several remarkable cases of differences in the nests of the same species in the northern and southern United States.

Why, it has been asked, if instinct be variable, has it not granted to the bee "the ability to use some other material when wax was deficient?" But what other natural material could bees use? They will work, as I have seen, with wax hardened with vermilion or softened with lard.