This done, he makes a new hole rather above the first, and fills the interval between the two, continuing this process until he has arrived at the top of the stalk and filled the whole interior. (Figs. 10 and 11.) The bird seems at first to take unnecessary trouble by boring so many holes. He would reach his end as well, it would seem, by making a single hole at the top to fill his storehouse, and another at the bottom to empty it. But we must not thus accuse him of lack of judgment. The interior of the tube is just large enough for the passage of an acorn; but at certain points the sap is not entirely absorbed, and there might easily be an impediment which would leave a large part of the cavity empty. Hence the necessity for a number of openings. When the sun has scorched up plants, and provisions are rare, he turns to his barns of abundance. Now and every time that he has need he can utilise the method that has been employed by his cousin the _Melanerpes_. In order to feed on each acorn without too much trouble, or allowing it to slip from his beak, the bird places it in a vice. He hollows a hole in the trunk of a tree, introduces the fruit there forcibly, and eats it at his ease.[52] [52] Henri de Saussure, "Observations sur les moeurs de divers oiseaux du Mexique," _Arch. Sci. phys. et natur._, 1859, pp. 21-41. [Illustration: FIG. 10.] [Illustration: FIG. 11.] The provisions collected by these two birds reveal a remarkable fact. They possess indeed two distinct diets; they do not preserve for the period of famine the overplus of the foods which they consume in the period of abundance. They chase insects and feed on them as long as they can find them, while they gather up in their storehouses an entirely different food. _Physiological reserves._--All the animals of which I have just spoken place their provisions for the future in barns in the same manner as Man. Those who have not this foresight are either able to nourish themselves in all seasons by the chase, or else, after having feasted one half of the year, they fast during the other half. In the latter case they consume during the fasting period a portion of their own substance, and use up materials placed in reserve in their organism, in the form of fat for example. This arrangement, which allows them to prolong life, though growing thin, until the next season of prosperity, is not under the control of the will. It is a complication of physiological phenomena resulting from the functioning of different parts of the organism. _Stages between physiological reserves and provisions._--Between physiological reserves and industrial stores we may place as an intermediate stage the interesting case of the Honey Ants.[53] [53] H. C. McCook, _The Honey Ants of the Garden of the Gods, and the Ants of the American Plains_, Philadelphia, 1882. [Illustration: FIG. 12.] [Illustration: FIG. 13.]