APPLE LEAVES, PLANT-LOUSE VARIETIES. 55 



shorter and more slender than the third, whilst the sixth is but half 

 as long, and the seventh is double the length of the sixth, and quite slender 

 and thread-like. The abdomen is short and thick, of an oval form, and ob- 

 tusely rounded at its apex, of a bright grass-green color, with a row of black 

 dots along each side forward of the nectaries, one dot upon each segment. On 

 its under side at the tip, are two square brown spots, more or less separated 

 from each other as the abdomen is distended with aliment in a greater or less 

 degree, and above the apex are often three short blackish transverse stripes. 

 The tail-like appendage in the female is black, and about a third as long as the 

 nectaries, which are also black, and if pressed against the abdomen, would 

 reach its tip in the females, but are shorter in the other sex. The legs are pale 

 dull yellow or whitish, with numerous even hairs; the feet, tips of the shanks, 

 and of the thighs, black or dusky; the hind thighs black, except upon their 

 basal third. The wings are transparent, but not perfectly pellucid, the stigma 

 or opake spot towards the end on the outer margin, is dull white, and the 

 veins are dark tawny brown, the longitudinal rib-vein being paler and becom- 

 ing whitish towards its base, the third or forked vein is abortive and colorless 

 at its base, and, as in many other species, the first vein has a dusky mark 

 from its tip, running upon the margin, towards the base. The first and second 

 veins are more than twice as far apart at their tips as they are at their bases; 

 the third vein is slightly farther from the second at its tip than at its base, and 

 is a third farther, or more, from the second at base than this is from the first; 

 the tip of the first fork is much nearer the tip of the second fork than that of 

 the third vein, and is about the same distance from the tip of the third vein 

 that this is from the second; the tip of the second fork is equidistant between 

 the tips of the first fork and the fourth vein ; the tip of this last is commonly 

 twice as near the tip of the second fork as it is to that of the rib-vein. 



Individuals have been observed, in which the wing-veins varied from their 

 normal state as follows : 



1. Tip of the third vein nearer that of the first fork than that of the second. 

 Common. 



2. The second and third veins parallel with each other. 



3. The second fork very short, its tip only half as far from the tip of the first 

 fork as from that of the fourth vein. 



4. Left wing with but one fork to the third vein, the second wanting. 



5. Right wing with three forks to the third vein. 



6. Left wing with the second vein slightly forked at its tip. 



The following varieties in the colors and marks of this species may be spe- 

 cified. The greatest diversity in these respects occurs after the coming on of 

 frosty nights in autumn, it being then difficult to find two individuals with 

 precisely the same hue and marks. This diversity is undoubtedly produced 

 by the cold to which the insects have been exposed, and the unhealthy juices 

 of the faded and decaying leaves which now furnish the only nourishment which 

 is accessible to them. It might hence be deemed that the whole race was now 

 in a diseased state, if it were not that sexual intercourse takes place freely, 

 and the females are all industriously occupied in depositing their eggs. 



Variety a, pallidicornis. The antennae brownish yellow instead of black. 

 Young individuals. 



