March, 1914.] The Food of Rana Pipiens Shreber. 
259 
and covered with a sticky secretion which adheres firmly to the 
food seized. So rapid is the protrusion of this weapon that a 
careful watch is necessary in order to see the animal feed. 
The material contained in the stomachs examined can be 
divided into two classes, animal and foreign. All the evidence 
indicates that the presence of substances other than those of an 
animal nature is merely incidental, and due to the mode and con¬ 
ditions of feeding. 
Foreign Matter. Nothing can be more natural, since the 
frog captures the greater part of its prey on the ground by means 
of its tongue, than that a small amount of foreign substance 
should be swept into the mouth along with the animals upon 
which it feeds. In the stomachs examined, this foreign substance 
LOT 11 
Frog N umber 
1 
2 
3 
4 
5 
6 
7 
8 
9 
10 
1 1 
12 
13 
14 
15 
16 
17 
18 
19 
20 
21 
AmmaU 
5 
8 
9 
3 
2 
12 
7 
6 
6 
9 
6 
2 
9 
2 
3 
6 
18 
1 1 
8 
7 
2 
Mollusca 
1 
1 
2 
1 
1 
1 
130poda 
1 
1 
1 
1 
1 
•Spi d«rs 
2 
2 
4 
1 
4 
2 
3 
2 
4 
4 
1 
1 
3 
4 
4 
1 
Insects 
j 
5 
4 
2 
2 
8 
4 
3 
A 
6 
2 
2 
5 
1 
2 
3 
12 
6 
6 
4 
2 
Acr ididae 
2 
Gcrndae 
1 
1 
1 
1 
3 
Membrac idae 
1 
1 
1 
Cote rpt II ars 
2 
2 
1 
2 
4 
2 
5 
2 
1 
2 
1 
5 
1 
Coleoptera 
2 
3 
2 
1 
4 
2 
3 
4 
1 
1 
2 
1 
2 
11 
2 
1 
1 
Cara btolac 
1 
1 
1 
2 
3 
1 
/ 
STapb ^Imi da<2 
1 
2 
Rhgnc^ophor a 
2 
2 
2 
1 
3 
2 
3 
4 
1 
2 
3 
2 
Beetle Larvae 
3 
Pormi cina 
1 
Bembeciolae 
1 
Collected Aug. 11, 1913, between 2:00 p. m. and 3:30 p. m. 
consisted of vegetable and animal matter. Very little vegetable 
matter was found. In four stomachs, it consisted of bits of rotten 
wood, in eight stomachs, seeds of Washingtonia claytoni Britton, 
in two stomachs, pieces of linden leaves (Tilia americana L.), 
and in two stomachs, a little spirogyra, the latter being found 
in stomachs containing aquatic insects. The mineral matter, 
which consisted of pebbles and sand, composed the greater part 
of the foreign material. Four small pebbles were found in four 
stomachs, and about fifteen per cent of the stomachs contained 
sand, three being completely filled with the latter only. Almost 
invariably, in the stomach containing sand, the frog had been 
feeding or preying on animals found on the ground. As the frog 
swallows its prey entire and the stomach does the whole process 
of trituration, it is probably that the sand aids in grinding the 
animals, especially insects like beetles with hard chitinous bodies. 
