Page:Phylogeny of cynipid genera and biological characteristics.pdf/47

 7.—Alternation of generations is a development of seasonal dimorphism, a gradual evolution incited by the differences in the nature of existence in different parts of the host plant at different seasons of the year, and achieved after a struggle for the fixation of the new generation. Agamy is not the primitive method of reproduction; it is of great advantage to the winter generation of dimorphic cynipids, and may have originated because of this.

8.—The highly specialized phenomena characteristic of the gall-wasps (gall production, agamic reproduction, and heterogeny) are of doubtful advantage, with the apparent consequences of the loss of vitality, exposure to the force of many enemies, and the ultimate extinction of the insects.

9.—Aulacidea and Phanacis are in every respect the most primitive of the Cynipidæ.

10.—Timaspis is almost as primitive.

11.—Aylax is primitive, but shows some specialization.

12.—Diastrophus is derived from the Aulacidea-Aylax group.

13.—Gonaspis is a specialized development of Diastrophus.

14.—Rhodites, derived directly from Aulacidea, is highly specialized.

15.—Neuroterus is the most primitive of the Cynipini, and in that genus are to be discovered the incipient stages of some of the peculiar phenomena of the Cynipidæ.

16.—Disholcaspis, highly specialized in most respects, shows somewhat direct relationships to more primitive groups.

The conclusions concerning the origin of the fully studied genera may be summarized as shown in figure 1.