Natures Militia 319 



bushes with road-dust, pay regiments of school-children 

 to gather grubs by the quart, try in fact all the various 

 expedients which have ever been resorted to, and yet 

 find in the end that it is simply impossible to overtake 

 the damage caused by the absence of the birds, with 

 their marvellously keen sight and extraordinary appe- 

 tites. 



Let us consider for a moment one single fact. Mr. 

 Darwin found that scarcely more than a sixth part of 

 his seedlings survived the attacks of slugs, snails, and 

 insects. But what does this mean ? Only this, that 

 if the numbers of the enemy had been increased by so 

 much as a sixth, there would have been no seedlings 

 left alive at all. 



One additional slug or caterpillar to every five would 

 positively have destroyed the whole crop, even in 

 England, where there are many hedgerows and many 

 birds, and where insect life is not anything like as 

 abundant as it is in warmer latitudes, such, for instance, 

 as certain parts of the United States, where railway- 

 trains are from time to time brought to a standstill 

 by armies of caterpillars or grasshoppers a foot 

 deep. 



It is difficult to realize, or even to form a faint idea 

 of, the numbers of insects, or the extraordinary rapidity 

 with which they multiply ; for the figures which are so 

 easily quoted are ' like the distances of the heavenly 

 bodies, too great for comprehension : nothing equals 

 them except the incredible appetites of the insect- 

 eating birds.' 



Take, for example^ the common house-fly, one of 

 which is said to have 21,000,000 descendants in the 

 tourse of a single summer, or would have, if all 



