Page:Phylogeny of cynipid genera and biological characteristics.pdf/33

 Lactuca is late July or early August. In all these instances there does not appear to be time enough for the development of an alternate generation in the same year between the date of emergence of the insect and the appearance of the gall of that species. More positive proof of the absence of an alternate generation is furnished by the work of Adler who secured, experimentally, the successive generations of Aulacidea hieracii and reported (1881) that there was no alternation of generations with that species. This absence of heterogeny is an important indicator of the lack of specialization of the group in that respect.

Our knowledge of fossil cynipids covers only three species and, with such limited knowledge, we are not warranted in drawing general conclusions. The three described fossils all belong to this genus Aulacidea.

The amount of vitality shown by individuals of this genus is (as I have described on p. 384) decidedly greater than that shown by the majority of cynipids, and this may be an indication of the relation of the group to the primitive, more successful insects rather than to the less vigorous, decidedly unsuccessful, more specialized forms.

We must conclude, then, on consideration of these eight or nine sorts of evidence, that this group is the most primitive in relationships of the existing Cynipidæ.

We should, undoubtedly, place this genus in as primary a position as Aulacidea, since the insect is morphologically as primitive and produces as primitive a gall. However, only two species of this genus are known (the gall of one is not known) and, consequently, we are not warranted in making too broad generalizations. We may not be correct in considering this genus distinct from Aulacidea.

This genus, with seven known species, is not very distinct from Aulacidea. The galls of the two groups are equally simple and occur on plants of many genera. An indication of higher position, evolutionarily, is seen in the radial cell, which is usually partly open; and the second segment of the abdomen, though of about the same size in the female as in Aulacidea, is larger in the male, there covering about onehalf of the abdomen.

We would include the following as belonging to the one genus: Aylax Hartig (=Aulax Hartig), Isocolus Förster, Eubothrus Förster, Liposthenes Förster, Antistrophus Walsh, Asclepiadiphila Ashmead, and