Puant Lick INJURING FOLIAGE AND FRUIT OF THE APPLE 703 
genital plate and the large oval area on the preceding segment are black. 
The antennae are 5-jointed, the third joint in some cases showing seg- 
mentation and thus giving a 6-jointed antenna. The length and number 
of sensoria of the antennal segments (fig. 112, a, page 685) are as follows: 
Segment III, 0.35 mm., sensoria 0; segment IV, 0.17 mm., sensoria 1; 
segment V, 0.11 + 0.15 mm., sensoria the usual group. The beak, reach- 
ing the base of the third pair of legs, is yellowish in color, with the last 
segment black. The legs are yellowish to dusky; the knees, the ends of 
the tibiae, and the tarsi are black. Lateral tubercles are present on the 
thorax and on the first eight abdominal segments. 
The second generation 
The young produced by the stem mothers all develop into either winged 
or wingless females. Fr m close observation covering two years the 
writer found that over 75 per cent of this generation acquire wings and 
rapidly distribute the species from tree to tree and from orchard to 
orchard. In 1915 the first individuals of this generation began maturing 
the last two or three days in May and the first days of June. In the 
rearing cages winged forms began appearing on May 31. Under the 
conditions of that year, which were decidedly unfavorable, the early 
individuals required more than nineteen days to reach maturity, while 
in some of the cages twenty-five days were required. 
It seems rather remarkable that so many individuals of this generation 
are provided with wings. Various theories have been advanced to explain 
the production of winged forms. The one oftenest quoted is that the 
condition is due to crowding, resulting in the lack of food. In cage after 
cage in these experiments there was neither crowding nor lack of suitable 
food, and yet the proportion of insects that acquired wings seemed, and 
actually was, as large as where there was undoubted crowding. It would 
seem that the production of such a high proportion of wiuged forms in 
this generation is entirely a provision by the species for its rapid and 
widespread distribution. It is self-evident that such a provision is emi- 
nently wise, and to account for it on a basis of crowding or lack of food 
appears, to say the least, highly inadequate. 
Activities 
Wingless forms.— The wingless forms exhibit no activities differing 
greatly from those of the stem mothers. After reaching maturity they 
