Page:The Gall Wasp Genus Cynips.pdf/163

 altho we cannot raise the same question for Schenck's records, it seems not to have been verified by later experience.

According to Beyerinck (1883:25) the abdomen of one of the larger agamic females may contain as many as 178 large eggs, altho a smaller individual may have only a score of eggs. Hartig (1840) first figured the structure of the abdomen of divisa, showing details of the ovipositor, eggs, and ovaries which we have copied in the present paper. Rössig (1904) used larvae of this species in his study of the origin of the gall-producing stimulus of gall-wasps, and his paper gives many details of the larval structure of divisa, especially of its oenocytes and Malpighian tubules.

In the early search for the missing male of the gall wasps, Hartig gathered 28,000 galls of this species and bred between 9,000 and 10,000 adult insects which were, of course, all females. This observation attracted considerable attention at that time, and provided some impetus to the investigations which resulted in our present knowledge of alternation of generations among these insects. Hartig first recorded his observations as applying to the ordinarily rare wasp, Cynips disticha; but in 1843 (Germar Ent. Zeit. 4:398) he stated that the observations applied to Cynips agama. Mayr-Fitch (1876, The Ent. 9:149) noted the correction, and later authors have accepted it.

Adler, in 1877, observed that the agamic divisa oviposits in unopened, terminal buds of the oak. Altho he obtained none of the galls of the alternate generation in these first experiments, his results in 1878 were more fortunate. The adults lived over a period of fourteen days during which a series of buds were pricked by the insects, and from these he obtained, on the young leaves in the following spring, five galls of verrucosa, the bisexual form described below.

The histology of the gall of divisa has been described by Lacaze-Duthiers (1853), Fockeu (1889), Hieronymus (1890), Kustenmacher (1894 acc. Kieffer 1901), and in more detail by Weidel (1911). These studies have all emphasized the similarity of divisa galls to those of Cynips folii, noting only such differences in epidermal coloring materials, more openly spongy parenchyma, hardness, size, and shape as are apparent in examining the gall with one's naked eye. Küster (1911) records only 53.5 per cent of water in these galls, which is