1918 | Grinnell: A Synopsis of the Bats of California 229 
Eyesight —Hahn (loc. cit., p. 155) says of the sight of bats: 
After extended observations on the subject, [ am still unable to form any 
definite conclusions with regard to the importance of sight to these animals. 
That they can see light and darkness and moving objects is unquestionable. That 
the sense of sight is not highly developed is equally certain. The behavior of 
some of the animals appears to indicate that at times they depend on this sense 
to a considerable degree, both in securing food and in avoiding objects. 
J. Grinnell (1913a, pp. 344-345) suggests that the fact that a 
given species of bat will appear abroad at a certain time almost to 
the minute each evening shows that these animals can appreciate light 
intensity within a very narrow range. 
It is suggested by Hahn (1908, p. 157) that a bat dipping to 
drink water from a quict pool is probably attracted to it by sight, but 
that the rising of moisture-laden air also helps the animal to locate 
water. 
Hearing —Low-pitehed rumbling noises have no effect upon bats; 
but to vibrations of high frequeney these animals are extremely 
sensitive (Hahn, loc. cit., p. 155). This is as one would expect to find 
it, since the hum produeed by flying insects is usually high-pitched, 
and the voices of the bats themselves are very shrill. . 
Hahn (loc. cit., p. 156) found that as a rule the bats he had under 
observation paid no attention to worms held near them, as long as 
the worms remained quiet, but became excited as soon as the worms 
began to wriggle. As this occurred when the bats were not touched 
by the worms and when they were out of the range of vision, Hahn 
infers that the food must have been perceived through the tactile 
organs, these being stimulated by air currents set in motion by the 
moving worms. In recording his experiments upon captive bats Hahn 
(loc. cit., p. 178) says: ‘‘Sound associations are formed readily. A 
sucking noise made by the lips at first alarmed the animals, but they 
soon learned to associate it with feeding. On hearing it they would 
look about and snap at any object that could be mistaken for food.’’ 
J. Grinnell (1913a, pp. 344-345) suggests that bats hunt their 
insect food by sound. He says: ‘‘Even the wing-strokes of a tiny 
miller must be distinetly audible to the bat which snaps it up so 
unerringly. And the droning of a June beetle must sound to the bat 
as penetrating as the roar of a biplane motor does to us.”’ 
At least one species of bat, Antrozous pacificus, undoubtedly 
secures a portion of its food upon the earth, since it brings to the 
roost wingless Jerusalem crickets (Stenopelmatus). It seems prob- 
