MINUTE OKGANISMS. 139 



this tribe of insects, and, with them, the species of birds which 

 subsist principally upon them. Thus the fine, large, red-headed 

 woodpecker. Pious erythrocephalus, formerly very common in 

 New England, has almost entirely disappeared from those States 

 since the dead trees are gone, and the apples, his favorite vegeta- 

 ble food, are less abundant. 



There are even large quadrupeds which feed almost exclusively 

 upon insects. The ant-bear is strong enough to pull down the 

 clay houses built by the species of termites that constitute his 

 ordinary diet, and the curious a/i-ai, a cHmbing quadruped of 

 Madagascar, is provided with a very slender, hook-nailed finger, 

 long enough to reach far into a hole in the trunk of a tree, and 

 to extract the worm which bored it.* 



Mmute Orgcmisms. 



Besides the larger inhabitants of the land and of the sea, the 

 quadrupeds, the reptiles, the birds, the amphibia, the Crustacea, 

 the fish, the insects, and the worms, there are other countless 

 forms of vital being. Earth, water, the ducts and fluids of vege- 

 table and of animal life, the very air we breathe, are peopled by 

 minute organisms which perform most important functions in 

 both the hving and the inanimate kingdoms of nature. Of the 

 offices assigned to these creatures, the most famihar to common 

 observation is the extraction of hme, and, more rarely, of silex, 

 from the waters inhabited by them, and the deposit of these min- 

 erals in a soHd form, either as the material of their habitations or 

 as the exuviae of their bodies. The microscope and other means 

 of scientific observation assure us that the chalk-beds of England 

 and of France, the coral reefs of marine waters in warm climates, 

 vast calcareous and silicious deposits in the sea and in many fresh- 

 water ponds, the common pohshing earths and slates, and many 

 species of apparently dense and sohd rock, are the work of the 

 humble organisms of which I speak, often indeed of animalculae 

 80 small as to become visible only by the aid of lenses magnifying 

 thousands of times the linear measures. It is popularly supposed 

 that animalculae, or what are commonly embraced under the vague 

 name of infusoria, inhabit the water alone, but naturalists have 



* On the destruction of insects by reptiles, see page 123 ante. 



