interior chambers of the caverns, half a mile or more from daylight, and not, as a rule, in dense clusters, although thousands may be hanging on a few square yards of rock. The positions of a number of bats were marked on the roof of a low chamber early in October. A week later about one third had moved, two weeks later half had moved and at the end of a month not one remained in its original position. By the end of December this chamber was entirely deserted and its occupants were scattered and were, for the most part, in higher chambers, where they were difficult of access.
The first week in January was very warm, and at this time I found many of the animals clustered near the cavern entrance. There is little doubt that some of them went outside, but they are unfitted for securing food that is cqncealed and they probably found few, if any, insects on the wing after nightfall. A sudden drop in temperature a week later was accompanied by a rush of cold air into the caves, and this scattered the bats and sent them into the inner recesses where the temperature is very nearly constant the year round. During February they again began to congregate near the entrance and the numbers increased and diminished irregularly until late in April, when they rapidly diminished as the bats left the cave for the season.
This, in brief, is the winter life of the cave bats. It begins, with some individuals, in August but is interrupted before winter begins. During the winter they move about to some extent and become more restless at the approach of spring, but are not able to get any considerable quantity of food until warm weather begins in earnest, usually in April.
The torpid condition of hibernation is induced by abundance of food and is not dependent on cold weather. The animals can be awakened from their lethargy at any time by mechanical disturbance alone. They are also made active by hunger after most of their fat is absorbed, but the end of their fast is determined directly by food supply and indirectly by weather conditions.
The Thirteen-lined Ground-squirrel
This animal is an inhabitant of the upper Mississippi Valley from Indiana to the Rocky Mountains. It is better known as the "striped gopher" but the gophers are very distinct, zoologically, while this species, as its name implies, is a squirrel.
It is closely related to the familiar chipmunk of the east, which it resembles in size and habits, although it is more slender of build and differently colored. In the region where it abounds it lives on the lawns, in the orchards and pastures, along railway embankments, and, in fact, almost everywhere. Hence it is easier to study than the chipmunk, and this is the reason for selecting it in preference to the more familiar eastern animal.
