110 THE ENGLISH SPARROW IN AMERICA. 



ried off by the Sparrows every day, yet are bound to say that there 

 was no appreciable diminution in the number of worms, and earlier in 

 the season, when the wingless moths were depositing the eggs for this 

 devastating army, the Sparrows were never detected eating the moths 

 at all, though the robins fed on them constantly. Moreover, the nature 

 and habits of this worm make it not only possible but easy to com- 

 pletely prevent or control its depredations, (See Professor Eiley's let- 

 ter to Dr. Cones in the report which follows.) 



Furthermore, the female, being wingless, does not wander far after is- 

 suing from the pupa, and the worms, when very abundant, after strip- 

 ping one orchard or row of trees, are too small to travel far in search 

 of more and yet too small to complete their transformation without more 

 food. Thus this state of affairs frequently brings about the extinction 

 of almost the whole army 



It has been remarked frequently by observant persons that the disap- 

 pearance of the canker-worms and similar caterpillars is very sudden. 

 One year an orchard or park may be overrun by them, and the next 

 season it may be impossible to find any at all. It is a well-known fact 

 that excessive multiplication often weakens an entire race, and then 

 when attacked by the multitudes of parasites which have increased 

 with it, or by disease which has been slowly advancing, it is unable to 

 resist, and a wholesale reduction in number is the result. A few days 

 of heavy rain, an unusual period of drought, a few hours of excessive 

 heat or cold, should these conditions occur at the critical point in the 

 career of a species, may so reduce its abundance that it will not regain 

 its former numbers for a dozen years or even more ; and if meanwhile 

 this turn of Fortune's wheel has given another species the ascendant in 

 the same district, the subsequent struggle may be prolonged indefinitely. 

 We do not know that any such crises were imminent in Philadelphia at 

 the time the Sparrows were first introduced there in numbers, but with 

 our present knowledge of the Sparrow's habits we believe that the re- 

 sults there are far more likely to have been reached through some such 

 combination of circumstances than through the comparatively insignifi- 

 cant number of worms devoured by the Sparrows. 



The following report by Professor Eiley on the insect food of the Spar- 

 row is a most valuable contribution to our knowledge of the food habits 

 of the species, and a careful study of this report, and of the tables which 

 follow it, will do much to dispel the illusions of those who class the 

 Sparrow among beneficial birds on account of its insectivorous habits. 



