Page:Phylogeny of cynipid genera and biological characteristics.pdf/31

 PHYLOGENETIC POSITION OF GENERA

We include Pseudaulax Ashmead in this group. The radial cell of the wings in Pseudaulax is closed, which is a primitive condition found elsewhere among the true gall-wasps only in the genus Rhodites and in some few genera known only from a very few species.

In all the species of Aulacidea the first abscissa of the radius is arcuate, one of the extreme forms of that vein in this family and, although, as we have already pointed out, the arcuate is not necessarily a more or a less primitive form than an angulate form of the vein, it is definitely an extreme condition in this family. Because of the way in which all the other lines of evidence read, we consider the arcuate vein most primitive rather than most specialized. In one species, Aulacidea annulata, the vein is arcuate with a very slight suggestion of an angle on one side only.

The second segment of the abdomen is smaller here than in any of the other gall-wasps, and this small segment represents a more primitive condition than where the segment is enlarged to cover most of the abdomen, as in most of the genera of the family.

The hypopygium in this genus is less highly specialized than in any of the other cynipids. It has not assumed the peculiar, pointed form found in species of Rhodites, nor become narrow and elongate as in most of the oak gall-makers. In Aulacidea it is still a broad, ventral plate, very little produced.

The species of this group inhabit plants of thirteen different genera distributed widely from one of the lower monotcotyledons, Triticum, to the highest plants, composits. This wide range of hosts is a very primitive condition, compared with the complete restriction of the greater number (93%) of the gall-wasps to plants of only two genera, and further study will undoubtedly reveal species of Aulacidea on many more plants than they are at present described from. Moreover, the only known instances among the Cynipidæ where the same species regularly inhabits plants of different genera seem to be in this genus and in the very closely related Aylax. Thus, Aulacidea tumida is found on either Solidago, Sonchus, or Lactuca; several of the American species of Aulacidea may be found on either Lactuca or Prenanthes; and Aylax pisum lives on Lygodesmia and on Stephanotis; while Aulacidea hieracii has been reported (possibly not entirely correctly) from Hieracium, Linaria, Cytisus, and Triticum. This is a remarkable lack of specialization in the choice of host.