﻿92 SEVENTH ANNUAL REPORT 



exceeding eight — and then perish. These eggs are of two sizes, the 

 larger about 0,02 inch long and the smaller about three-fifths of that 

 length. In the course of a fortnight they produce the sexual indi- 

 viduals, the larger ones giving birth to females, the smaller to males» 

 These sexual individuals are born for no other purpose than the re- 

 production of their kind, and are without means of flight, or of taking 

 food, or excreting. They are quite active and couple readily ; one 

 male being capable, no donbt, of serving several females, as Balbi- 

 ani found to be the case with the European quercus. The abdomen 

 of the female, after impregnation, enlarges somewhat, and she is 

 soon delivered of a solitary egg, which differs from the ordinary eggs 

 of the parthenogenetic mother only in becoming somewhat darker. 

 This impregnated egg gives birth to a young louse which becomes a 

 virginal, egg-bearing, wingless mother, and thus recommences the 

 cycle of the species' evolution. But one of the most important dis- 

 coveries of Balbiani is that, during the latter part of the season, 

 many of the wingless, hypogean mothers perform the very same func- 

 tion as the winged ones ; i. <?., they lay a few eggs which are of two 

 sizes, and which produce males and females, organized and con- 

 structed precisely as those born of the winged females, and, like 

 them, producing the solitary impregnated egg. Thus, the interesting^ 

 fact is established that even the winged form, is by no means essen- 

 tial to the perpetuation of the species; but that, if all such winged 

 individuals were destroyed as fast as they issue from the ground, the 

 species could still go on multiplying in a vineyard from year to year. 

 We have, therefore, the spectacle of an underground insect posses- 

 sing the power of continued existence, even when confined to its 

 subterranean retreats. It spreads in the wingless state from vine to 

 vine and from vineyard to vineyard, when these are adjacent, either 

 through passages in the ground itself, or over the surface. At the 

 same time it is able, in the winged condition, to migrate to much more 

 distant points. The winged females, as before stated, begin to appear 

 in July, and continue to issue from the ground until vine growth 

 ceases in the Fall. Yet they are much more abundant in August than 

 during any other month, and on certain days may be said to literally 

 swarm. Every piece of root a few inches long, and having rootlets, 

 taken from an infested vine at this season, will present a goodly pro- 

 portion of pupae ; and an ordinary quart preserve jar, filled with such 

 roots and tightly closed, will furnish daily, for two or three weeks, a 

 dozen or more of the winged females, which gather on the sides of 

 the jar toward the light. We may get some idea, from this fact, of the 



