come entangled in nursery material or used as packing. It is very interesting to find insects of so little vitality living through such a journey, and upon emergence from the galls to be able to endure the new conditions and to find the hosts necessary for the continuance of the species. There are only three other instances of the sort. The introduction of Rhodites rosæ and R. mayri, of roses, is easily understood, but the successful introduction of Aylax glechomæ and of A. taraxaci (not yet rerecorded from Europe, but since the dandelion is of European origin it is probable that the gall-wasp is also introduced) upon herbaceous plants is more surprising.
This species is, in many respects, very distinct from and more specialized than other members of the genus Aylax. The striations of the face resemble those of Diastrophus, the second abdominal segment is remarkably developed, the monothalamous and separable gall is (as I am showing elsewhere) a good indicator of advanced evolution, and the undoubtedly completely agamic reproduction is not found elsewhere, as far as is known, in the genus. These and other considerations suggest that glechomæ must be considered a high development in Aylax or possibly as belonging to a distinct genus.
The galls appear in late May or early June. In this young condition they are eaten in France. The galls mature in late July and, as the plants begin dying off in September, the diried galls drop to the ground where they overwinter, being in large part decayed by springtime. The galls are heavily parasitized. The insects mature in the fall and overwinter as adults, not emerging, however, until the following April or May. Adler proved, by experimentally raising successive generations, that there is no alternation of generations with the species and, since the male is unknown, it is likely that reproduction is regularly agamic, the eggs never being fertilized. This pure agamy is a remarkable condition not easily comprehended as a fit mnethod of maintaining the vitality of an organism.
Rhodites rosæ (Linnæus)
Plate XXVIII, Figures 3 and 4
Cynips rosæ Linnæeus, 1758, Syst. Nat., 10th Ed., p. 553.
Diplolepis bedeguaris Geoffrey, 1762, Hist. Ins., II, p. 310.
Diplolepis rosæ Fourcroy, 1785, Ent. Paris, p. 392.
Diplolepis bedeguaris fungosæ Lamarck, 1817, Hist. Anim., IV, p. 163.
Rhodites rosæ Hartig, 1840, Zeit. Ent. Germ., II, p. 194. Förster, 1869, Verh. zool.-