INCREASE OF ANIMAL LIFE 393 



but he believed that the less intense cultivation of the corn- 

 field would yield only about half that enormous number. 

 Even more striking are the facts recorded by Marsh relating 

 to the increase of Earthworms which followed upon the de- 

 velopment of agriculture in North America. 



"Forty or fifty years ago," he wrote in 1874, "they [Earthworms used by 

 anglers for bait] were so scarce in the newer parts of New England, that 

 the rustic fishermen of every village kept secret the few places where they 

 were to be found in their neighbourhood as a professional mystery, but at 

 present one can hardly turn over a shovelful of rich moist soil anywhere 

 without unearthing several of them. A very intelligent lady, born in the 

 woods of Northern New England, told me that in her childhood these 

 worms were almost unknown in that region, but that they increased as the 

 country was cleared, and at last became so numerous in some places that 

 the water of springs and even of shallow wells, which had formerly been 

 excellent, was rendered undrinkable by the quantity of dead worms that fell 

 into them." 



INCREASE OF ANIMAL FOOD 



The increase of such animal life as depended upon vege- 

 table food naturally led to new developments in the numbers 

 of the creatures which subsist upon their fellows. The fresh 

 numbers of Worms in New England, just alluded to, gave 

 rise to an influx and increase of the small insectivorous 

 birds which follow the trail of the settler. It was they who 

 checked the excessive multiplication of the Worms and finally 

 abated the nuisance. 



So the augmentation of our own tiny vegetarians, earth- 

 worms and insect pests, has led to increase of carnivorous 

 Centipedes, insect-eating Birds, and Moles. Observation of 

 the habits, and examination of the food contained in the 

 crops of soft-billed birds leave no doubt that they subsist 

 largely upon the insect products of cultivated crops. Professor 

 Newstead found that on a low average a Starling visited its 

 young 169 times a day, and on some days 340 times, with 

 food which included 269 injurious insects. A Great Tit was 

 seen to make 384 visits in a day and 90 per cent, of the food 

 carried during its visits consisted of insect pests. Professor 

 Newstead concludes 



If 20 days are occupied in rearing the young, that gives us a grand total 

 of 7680 visits to the nest, so that the single pair of birds would be re- 

 sponsible for the destruction of between 8000 and 9000 insects, chiefly 

 caterpillars. 



