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Page:Popular Science Monthly Volume 34.djvu/176

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164
THE POPULAR SCIENCE MONTHLY.

every prominent feature of their homes was reproduced. I found that at 120° Fahr., with the atmosphere perfectly still, they invariably sought shelter, clustering in one cooler and dark corner; but at 100° they were exceedingly active, particularly if hungry, and made no effort to avoid the direct rays of the sun.

When exposed to a sudden transition from a very high to a low temperature, they quickly became inert, and, as the warmth was allowed to increase, it was instructive to see the sluggish movements of both the lizards and the imprisoned flies give way to more active ones, which culminated in the restored suppleness of the reptiles being equal to the capture of the swiftly darting insects. Forced exposure, for a period of three hours, to a temperature of 135°, caused death in four instances, and brought about a condition akin to æstivation in nine specimens thus exposed. As the pine-tree lizards are always found in localities where there is adequate shelter from excessively high temperature, it is not probable that æstivation ever occurs, as it does occasionally among some of our wild mice; but it is interesting to note that a condition closely allied to it can be artificially produced.

The conclusion reached by both field observation and experiments was, in brief, that when the temperature is such that those forms of insect life upon which they depend become inactive, the lizards withdraw to their shelters and likewise remain quiet if not asleep, this period of inactivity extending over several days, as during the prevalence of a northeast storm, or a protracted "spell" of cool and cloudy weather. Again, experiments with a large number in confinement showed that when kept without food at a low temperature, they lived for many days, while a like number starved in a short time when a high temperature was maintained. This lizard, therefore, appears to be one originally belonging to a tropical climate, that has gradually become adapted to a temperate and variable one.

The normal coloring of the pine-tree lizard is distinctly protective. Whether this has been gradually acquired or not, it is certain that it now renders the animal quite inconspicuous. Particularly when it is resting upon a rough-barked tree is this true; and one of my first objects, in studying the species in its native haunts, was to determine how far the markings were changeable and under their owner's control. Many specimens were found to be quite dark—indeed, almost black—while others were so light that the undulating transverse bars upon the back were very distinct and discernible at a considerable distance. This difference, I am quite sure, bore no relation to the surroundings; and the specimens subsequently collected and kept under daily observation for nine weeks practically retained the light or dark coloring they possessed, at the time of capture. In confinement many