350 REPORT UPON COTTON INSECTS. 



countries only to a very limited extent, and not in continuous belts, the insect labors, 

 therefore, under conditions unfavorable to an excessive multiplication. 



Second. Aletia acquires migratory habits alone by excessive multiplication, as I have 

 had ample opportunity to observe daring last spring and summer. 



Third. Should the insect in the countries named above multiply excessively, and 

 therefore acquire migratory habits, its first appearance in the United States would be 

 very sudden and in large numbers, and perhaps confined to the regions nearest the coast. 

 The information I received last winter from numerous planters, which was fully cor- 

 roborated by my own observation during last spring, proves that the first generation 

 of worms is everywhere very scarce in numbers, and that the insect does by no means 

 appear first near the coast, but at various localities within the more southern portion 

 of the cotton-belt. 



In view of the facts mentioned above, the theory of the annual immigration of Aletia 

 from tropical countries appears to be seriously weakened, and only supported by the 

 undeniable fact that nobody ever found Aletia hibernating in any of its stages in the 

 United States. On this latter point I have already expressed my opinion in a former 

 letter to the department, and will only repeat here that the failure of others and my- 

 self to find Aletia in its winter quarters is no proof at all against the theory of the 

 hibernation of this insect in the United States. 



In connection with this subject, I would like to mention that, at various places 

 throughout the cotton- growing States, numerous planters, and among them very observ- 

 ing and intelligent ones, assert that they have seen the cotton-moth flying about houses, 

 &c., on warm evenings in winter time and early spring. How much truth there is in 

 these assertions I do not know, but the fact is that they only saw the iusoct flying 

 about, and never actually captured an Aletia, and still less sent it to entomologists for 

 identification. All moths either attracted by light or by sweets ami captured by my- 

 self in winter time in the Southern States proved without exception to be other species 

 than Aletia. I object, therefore, to the argument just mentioned being brought forth 

 at the present time in favor of the theory of hibernation of Aletia. 



What I have said above on the hibernation of Aletia refers only to the more southern 

 portion of the cotton-belt of the United States, as everybody who has traveled through 

 the Southern States must be convinced that the insect never hibernates in the more 

 northern portion of the cotton district. Its appearance there is exclusively due to 

 immigration of the insect from its breeding-places in the southern portions of the 

 cotton-belt. 



If circumstances are favorable to its development the insect can acquire migratory 

 habits in its second generation, or, at any rate, very early in the season, and the 

 result would be a more or less destructive appearance of cotton-woruis throughout the 

 cotton-growing States. Usually, however, the insect is kept, in check by its natural 

 enemies and by climatic influences or by both, or the vigorous and combined efforts of 

 the planters in poisoning the worms, and it acquires migratory habits only late in the 

 season, say in the month of September, when its ravages in the northern portion of the 

 cotton-belt does not materially injure the crop. 



It is, of course, impossible for me to circumscribe accurately the northern limits of 

 the breeding-grounds of Aletia, but they may be roughly indicated as follows: 



In Texas the breeding-ground of Aletia includes the whole extent of the cotton dis- 

 trict south of -the Galveston, Harrisburg, and San Antonio Railroad, but extending 

 farther northward along the river bottoms. In Louisiana and Mississippi it includes 

 the bottom-lands of the Mississippi River and its tributaries, but 1 am unable to indi- 

 cate the northern limits. In Alabama a portion or perhaps the whole of the canebrake 

 region. Farther east it includes the cotton districts of Florida and perhaps a small 

 portion of Southern Georgia. 



Within the area thus indicated the cotton-worm hibernates every year and appears at 

 various localities, wherever it has succeeded in escaping the winter, as early in the 

 season as the cotton-plant is fit to eerve as food for the young larva. It is hardly neces- 

 sary to say that these early generations of cotton-worm are overlooked by farmers, and 

 it is indeed a difficult task to find the first generation of worms, as it is usually con- 

 fined to small spots and as its ravages are inconsiderable. 



All efforts to keep the insect in check ought to be confined to this southern portion 

 of the cotton-belt in order to prerent an excessive multiplication and with this an 

 early immigration of the insect to the more northern portion of the cotton-raising 

 States. 



E. A. SCHWARZ. 



COLUMBUS, TEX., September, 1879. 



J. HENRY COMSTOCK, 



Entomologist, Department of Agriculture. 



