Page:Life histories of American Cynipidæ.pdf/7

 gall, the acorn-gall, were identical with those which had been found ovipositing to produce the woolly gall. This connection was finally established when C. V. Riley, in the spring of the same year in which Bassett found the producer of C. operator, bred the adult from the acorn-gall. It was identical with the producer of C. operator. The fact of alternation of generations in the Cynipidæ was thus completely proved.

Meanwhile, B. D. Walsh (1864) had reported in great detail the discovery of two very different forms of adults, one agamic and the other bisexual, emerging at different times of the year from very similar if not identical galls of Amphibolips confluens. The work was undoubtedly exact as far as it went and, if it covers the complete life cycle of the species, it furnishes the first completed record of alternation. But Walsh, though he attempted to control the insects by confining them in nets placed on the trees, was unable to discover oviposition and it is not yet satisfactorily shown that the complete life cycle of the species has been discovered. Osten Sacken (1865, p. 341), greatly impressed with Walsh's work, predicted that perhaps "in some cases, the galls producing the dimorphous females were somewhat, or perhaps even altogether, different from those producing the bisexual brood," thus anticipating a summary of the rule which was not to be proved satisfactorily for another twenty years.

European zoologists had long been impressed by Hartig's observation (1840) that among almost 10,000 females bred from one species of gall not a single male was discovered. Similar experience had been had by all the students of gall-wasps and Giraud is quoted (Lichtenstein, 1881, p. xi) as remarking "Il a y dans ces Cynipides agames un mystère dont la découverte fera la gloire d'un homme." To solve this mystery, Dr. Hermann Adler, a physician at Schleswig, undertook to raise under controlled conditions successive generations of species of cynipids. In 1877 he made the first report of his work and, when he made the more complete report, in 1881, the abundance of his observations with a number