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RESIDENCE OF CERTAIN SOUTHERN FORMS IN LOCALITIES FAR NORTH 
OF THEIR NATURAL LIMITS. IS TRANSIENT. 
In the increase of the areas occupied by these insects they obey a 
natural impulse for migration, and are evidently largely influenced by 
the wind, and this is particularly the case with moths. There can be 
little doubt, also, that insects introduced into the North, and from there 
southward, are again brought northward by winds from the South; in 
fact, there is little stability in the localities occupied by many species, 
winds, frosts, prolonged heat and consequent drought, excessive rains 
inducing abnormal moisture of the insect’s food plants, diseases, and 
natural enemies being among the elements which produce changes caus- 
ing fluctuation in numbers in this or that locality, a decrease here this 
year and an increase there another year.’ 
SPECIES INTRODUCED IN THE NORTH FROM THE SOUTH AND FROM 
EUROPE REMAIN LATE IN THE FIELD. 
Southern or Lower Austral species, particularly those which are 
injurious, which have come up to this region from the South in com- 
paratively recent years, are rarely found early in the season, especially 
after severe winters, but increase toward the end of the season, and 
often, if not usually, occur in their larval stages, busily feeding through 
the months of October and November, even after frosts, as has been 
noticed for several years, and particularly during the two seasons just 
passed. The same is true, for some reason, of species which have 
widened their range in other directions, and particularly of insects 
which have been introduced from Europe. 
Most of the introduced plant-lice, and those which have come up 
from the South, live on their food plants after frosts, long after nearly 
all other insects have disappeared in the field. 
It is true that many native plant-lice also remain feeding late in the 
season. 
1 The writer desires here to call attention to the absurdity of recording strong-flying 
species of insects, and especially moths, like those just mentioned, as residents of 
northern localities beyond their natural limits, where theres no proof whatever that 
the species could ever have bred there, particularly when we know that no food plant 
upon which the larva could have subsisted grows there. If such species are included 
in local lists at all, the circumstances attending capture should be added. A familiar 
example of an insect which lives normally in the South and is frequently found as 
far northward as Canada is the gigantic Noctuid, Mrebus odora. It is native to the 
West Indies, and not known to breed in the United States. In spite of recent remarks 
that have been made that would appear to indicate that this moth might breed within 
the territory of the United States proper, the writer can not believe that it is at pres- 
ent established here, or even will be within the near future, as only isolated specimens 
are found northward, and these in late summer or autumn, as in the case of the cotton- 
worm moth, which it has been, I think, definitely proved does not breed in the North- 
ern States. 
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