838 
ANNUAL REPORT OF NEW YORK 
AmiS. ITS GENERATION ANOMALOUS. 
spot also, the veins bounding its two sides being brown; inner edge with the oustoroary blackish 
streak extending forward for a short distance from the tip of the first vein. First aDd second 
veins more than twioe as far apart at their tips as at their bnses. Third vein as far from tho 
second at its origin as this is from the first, nearly parallel with the second vein, very slightly 
farther from it at its tip than at its base, its fork given off forward of its middle, and thia 
fork sending off the second one beyond its middle. Tip of the first fork twice as far from the 
tip of the third vein as from the tip of tho second fork. Fourth vein strongly curved through 
two-thirds of its length and then straight and parallel with tho second fork, its tip nearer the 
tip of the second fork than this is to that of tho first fork, and almost twice as far from the 
tip of the rib vein as from the second fork. 
The above description was drawn lip from a comparison of 
different individuals taken upon the leaves. Numerous varia¬ 
tions occur however in the colors, in the veins of the wings, &c. 
The wingless female, plate i, fig. 6, is so like the winged one that 
a separate description of it is unnecessary. 
In the generation of these plant-lice, we are presented with one 
of the most remarkable anomalies which we anywhere meet with 
in the works of nature. All the insects we see on the grain 
during the spring and summer are females. These do not pro¬ 
duce eggs, but living young, which mature in a few days, and are 
fertile without any intercourse of the sexes. It is only when 
cold wet ther is coming on, at the end of the season, that males 
are produced. The insects then pair, and the females thereupon 
lay eggs, placing them, no doubt, upon the fall-sowed wheat and 
rye, which is then up in our fields. These eggs remain through 
the winter, to be hatched by the warmth of the following spring. 
The young from them grow up, and commence 'bearing living 
young, no males and no eggs being produced, except as the clos¬ 
ing act of their operations in autumn. Such, at least, is the case 
with other species of plant-lice, whence I infer it will be the same 
with this. 
Rye grows so rapidly and ripens so early, that it outstrips this 
insect in its increase, and thus sustains no material injury from 
it. Winter wheat, ripening more slowly, suffers more from it. 
But the crops which ripen latest and when this aphis has become 
multiplied to its greatest extent, namely, spring wheat and oats, 
have been the most thronged and havo sustained tho greatest 
injury. At our recent State Pair, persons from different parts 
of the State informed me that the spring wheat in their respective 
localities had been severely injured by this insect, several 
instances being told me in which the yield has been diminished 
fully one-half by it. 
We come next to notice the destroyers of this insect, which at 
