Page:Phylogeny of cynipid genera and biological characteristics.pdf/30

 galls of Andricus pellucidus, but from the other seven, monothalamous galls I secured seven mature adults, most of which had eaten their way through the walls of the larval cells but had then died before getting through the thinner walls of the outer gall. I gathered many adults of Andricus tecturnarum which had emerged through the hard walls of the galls but had then died before escaping from the coat of tangled hairs which covered the galls. Hundreds of other similar instances might be cited. It is likely that under natural conditions there is less of this sort of mortality than when the gall is gathered into breeding jars, but even this indicates an amount of vitality possessed by the insects which is none too sufficient.

On the contrary, species of Aulacidea are very easily bred in numbers and it is a rare thing to find adults left in the galls. The adults of these species will always live for many days. I have just found a female of Aulacidea annulata which was soaked in alcohol for half an hour and then glued to a cardboard point; the insect was discovered alive after ten days in a Schmitt box. Such vitality, as far as 1 nave ever seen, is not to be found among the oak gall-wasps.

On the basis of these considerations, the Cynipidæ may be divided into two miore or less distinct groups. One group, including mainly oak gall-wasps, has little vitality, possesses a mode of reproduction which would seem to guarantee a continuation of the lowering of vitality, and has a manner of living its larval life which invites a tremendous number of parasites and offers often insurmountable obstacles to the insect's growth to maturity. The other group, mainly Aulacidea and the allied genera, has a much larger amount of vitality, a method of reproduction (bisexual) which is fit to maintain the vitality of the group, and a mode of larval life (in simple galls or merely in stems) which offers fewer obstacles to the achievement of maturity. The first group is very apparently over-specialized and must ultimately become extinct. It is not likely that such a group could have furnished the progenitors of the second group, i. e., the Cynipini were not the ancestors of the Aulacini. This latter group possesses the far more successful mode of living and is likely to survive until it too has become specialized to the ultimate, the disastrous degree.