26 
TRANSITION ZONE. 
The species occurs well up in the Transition zone, if not indeed 
overlapping on the southern limits of the Boreal zone, though in this 
northern latitude it is apparently not ver}^ destructive. It is here 
recorded as injurious to late sweet corn and also tomatoes. Rather 
severe injury was reported in the vicinit}^ of London, Ontario, in 1898, 
by Dr. James Fletcher,^' and also by Mr. J. Dearness.* Several fields 
of corn were infested, varying in extent from about 20 to 95, or in 
one case nearh^ 100 per cent, with from one to several larva? in each 
ear. In a letter concerning this species Doctor Fletcher states: 
Heliothis armiger \_obsoleta'] is sometimes abundant and destructive to late sweet 
corn, the larvae at that time being of all sizes to full grown. * * * Moths are out 
at Toronto and here [Ottawa] by the end of September and sooner. * * ^ We 
have also received specimens from Beulah, Manitoba, but the species is decidedly 
not common. 
Injmy to sweet corn in 1892 is reported^ from Farmington, Me., a 
town on the border line of the Boreal and Transition zones in that 
State. The identity and character of the insect seem to have been 
quite unknown to those suffering from its ravages, which ma^^ be 
taken as evidence of its infrequent occurrence. No records have been 
found to indicate its occurrence in the numerous patches of the Boreal 
zone along the Alleghen}^ and the mountain chains of the AVest, 
although it is known to occur in numbers in adjacent areas of the 
Transition zone. It may, therefore, perhaps be safely inferred that 
the insect is not able to extend itself permanenth^ into the Boreal 
zone, by reason of temperature and other conditions. 
It is pertinent to mention that in New Mexico Prof. T. D. A. 
Cockerell, who has given considerable attention to the life zones of 
insects, records^' the species onh" from the area designated by him 
Upper (including middle) Sonoran. 
The restraining influence of low and sudden changes in temperature 
on the successful- existence and increase of species of more southern 
occurrence, in their northward spread, has been recentlv commented 
upon ^ b}^ Doctor Chittenden, of this Bureau. According to this gen- 
tleman's observations the bollworm was comparatively rare on corn 
and other crops, which it commonly infests in the vicinity of Washing- 
ton during the season following the severe freezes of February and 
March, in 1899. The severe character of the winters .of the more 
northern States, coupled with the relativeh^ low sum of effecMve tem- 
perature, no doubt has an important bearing on the comparative 
immunity of this territor}^ from serious injury. 
"Eept. Ent. Soc. Ont., 1898, p. 82. 
&Ibid., p. 62. 
cAnn. Kept. Maine Agric. Exp. Sta., Pt. IV, 1892, p. 119. 
^Bul. 24, N. Mex. Agric. Exp. Sta., p. 35. 
eBul. 22, U.S., Div. Ent., U. S. Dept. Agric, p. 56. 
