EXPERIMENT STATION EEPORT. 555 



Danger to Ne-nr Jersey ? 



In a careful study of the life history of the gypsy moth, the question 

 arose: Assuming that the insect is introduced into the State, can it 

 maintain itself here? As to the more northern' sections, in all proba- 

 bility, yes ; as to the region south of the red shale line, in all prohabil- 

 ity, no. 



Dr. Fernald's careful study of the life history and development of 

 the gypsy moth proves to demonstration that the matter of egg de- 

 velopment is almost entirely a question of temperature. As soon as 

 the spring temperature rises sufficiently, the eggs hatch — those in the 

 warmest places first, the others as the general temperature rises. The 

 egg masses formed in early August are, of course, subject to the same 

 general laws of development. They are normally intended to pass the 

 winter in that condition, and development of the embryo proceeds 

 slowly. As the average temperature decreases through longer, cool 

 nights, development is checked, proceeds more slowly, and soon ceases 

 altogether until resumed under the influence of the spring sun. Yet, 

 if the average temperature continues sufficiently high, development 

 will continue, even to the hatching of the eggs, as was found in the 

 season of 1895, at Woburn, Mass., where an unusually warm period in 

 late August and early September induced the hatching of a large per- 

 centage of the eggs. None of the larva? of this late hatching reached 

 maturit}'. 



Now, the climatic conditions in New Jersey south of the red shale 

 line are just those of the unusual conditions of 1895, and we are entitled 

 to conclude that the effects on the insects would be similar. In other 

 words, assuming that a colony were established anywhere in Burling- 

 ton count}^, it might develop normally until the e^gs were laid in late 

 Jul}^, but then the high average temperature of August and early Sep- 

 tember would induce these eggs to hatch, and long before the larvne 

 could come to maturity the food supply would be cut off or lessened to 

 such an extent tliat none of them could develop. 



As to the question that has been asked : Can we do anything to pre- 

 vent introduction of the insect into New Jersey ? the answer must be, 

 no. It is possible, however, to keep a close lookout and to be in readi- 

 ness to stamp the species out should it succeed in forming a colony. 

 On that point the Department expects to keep itself posted, but it is 

 dependent largely upon information that comes from those especially 

 interested in trees or parks. 



