94 THE GYPSY MOTH. 



The Increase and Distribution of 

 THE Gypsy Moth. 



The Rate of Increase. 



The study of the increase and dissemination of the gypsy 

 moth in Massachusetts is most interesting. Perhaps there 

 never has been a case where the origin and advance of an 

 insect invasion could be more readily traced. As the moth 

 appears to be confined as yet to a comparatively small area, 

 and as the region has been examined more or less thoroughly 

 for five successive years, the opportunities ofiered for the 

 study of the multiplication and distribution of the insect 

 have been unequalled. 



When it is considered that the number of eggs deposited 

 by the female averages from 450 to 600, that 1,000 cater- 

 pillars have been seen to hatch from a single egg-cluster, 

 and that at least one egg-cluster has been found containing 

 over 1,400 eggs, there can be no doubt that the reproductive 

 powers of the moth are enormous. Mr. A. H. Kirkland has 

 made calculations which show that in eight years the unre- 

 stricted increase of a single pair of gypsy moths would be 

 sufficient to devour all vegetation in the United States. This, 

 of course, could never occur in nature, and is mentioned 

 here merely to give an idea of the reproductive capacity of 

 the insect. 



It seems remarkable at first sight that an insect of such 

 reproductive powers, which had been in existence in the State 

 for twenty years, unrestrained by any organized eflTort on the 

 part of man, did not spread over a greater territory than 

 thirty townships, or about two hundred and twenty square 

 miles. Some of the causes which at first checked its increase 

 and limited its difiusion in Medford have already been set 

 forth (pages 5-7). Most of the checks which at first served 

 to prevent the excessive multiplication of the gypsy moth in 

 Medford operate efiectively to-day wherever the species is iso- 

 lated. True, it has now become acclimated. But any small 

 isolated moth colony still suflTers greatly from the attacks 



