Puant Lice Insgurinc FOLIAGE AND FRuIT oF THE APPLE 745 
The reproductive activities of the spring and the fall migrants are 
undoubtedly due to the same factors, and are in marked contrast to 
those of the summer and spring forms. With the latter the rate of repro- 
duction usually is low at first, gradually reaches its maximum, and then 
as gradually declines. The reproductive activities of the migrants can 
be explained, in all probability, in the following manner: They do not 
leave their host plants until a few days after reaching maturity, so that 
the reproductive organs are extremely active on reaching the new host, 
plant. In order to avoid destruction by many agencies, such as climatic 
conditions, predatory enemies, or the like, it would seem essential that 
the greatest possible deposition of young should occur as soon as possible 
after the new host plant is found. So much of the vitality of these 
forms has been used in the production of wings and in the search for 
the new host plant, that a high reproductive capacity would seem 
physiologically impossible. 
The summer generations consist very largely of wingless viviparous 
females. In 1916 winged forms appeared in the third, the fourth, and 
possibly the fifth generation, counting the descendants of the spring migrants 
as the first generation on plantain. In the third and fourth generations 
winged forms appeared in considerable numbers; the writer made no 
attempt, however, to determine the relative proportions of winged and 
wingless forms. This is in rather marked contrast to the results of 
Baker and Turner (1916 b), who record having observed but six winged 
forms thruout a summer’s rearing work.” The winged forms developing 
in the large rearing cages were very active and flew about with great 
ease. Unfortunately the writer was unable to do much work with these 
forms, tho they reproduced normally and appeared well able to distribute 
the species during the summer. Whether these forms can return to 
the apple and breed there was not determined; the probability of such 
a condition has already been discussed (page 741). 
Baker and Turner (1916 b) conclude that the summer winged forms 
are produced in such relatively small numbers that they are of no particular 
importance in the life history of the species. The writer cannot accept 
such a conclusion founded upon a single season’s rearing work, particularly 
as different results were obtained at Ithaca. Furthermore, the large 
®JIn the writer’s rearing experiments of 1917, results similar to those of Baker and Turner were 
obtained. However, the writer does not consider ‘such results as normal. 
