THE FOOD OF THE OTHER LAND ANIMALS 95 



The bats, all of which fly, hke most birds, though guided 

 by their hearing instead of by their sight, are nearly all carniv- 

 orous, and mostly insect eaters; a few catch birds, one is a 

 fish eater, some are blood suckers, and several of the largest 

 ones eat fruit, often committing serious depredations. 



In Australia except for the so-called monotremes, including 

 the spiny ant-eaters and the duck-billed mole {Ornithorhynchus) 

 which lay eggs like birds, for the bats and for some rodents, 

 all of the mammals are of a single type called the marsupial 

 because in nearly all, the females possess pouches in which 

 their singularly helpless young are reared. In the absence of 

 competition from more efficient types the marsupials in Aus- 

 tralia have to a considerable degree paralleled the chief mam- 

 malian types found in other lands, some being vegetarians, 

 like the kangaroos, others fierce predaceous beasts like the 

 marsupial wolves and the Tasmanian devils, some ant-eaters, 

 some feeding on insects generally, and some more or less 

 omnivorous. Outside of Australia the only marsupials are 

 the carnivorous opossums of South and southern North Amer- 

 ica. 



To complete the picture of life on land let us consider briefly 

 the food of the few remaining groups. 



The land molluscs, the snails and slugs, occur ever>^vhere 

 and form the most numerous and important animal group after 

 the insects and the vertebrates. Nearly all of them inhabit 

 damp places out of doors, or cellars, and are active only at 

 night or in wet weather. They feed chiefly on decaying vege- 

 tation and on fungi, but often on green vegetation and on 

 fruit, sometimes causing much damage in gardens. Some 

 pass sand or mud through the alimentary canal, digesting out 

 the organic particles, like earth-worms. A few are more or 

 less carnivorous, earth-worms being their chief victims. One 

 land snail possesses the power of boring into rock. In addi- 

 tion to the snails and slugs, a small bivalve, like a minute 

 clam, is sometimes found among moist leaves in the woods, 

 usually near water. 



