PSYLLIA PEREGRIN A FÖRST., THE HAWTHORN RACE OF THE APPLE SUCKER, P. MALI SCHMIDB

Conclusions and Summary The conclusions based on these investigations may be summarised as follows: “P. peregrina” and P. mali of hawthorn are identical, and are only the seasonal forms of one and the same species. These insects are also morphologically indistinguishable from P. mali o. apple. The nymph of the forms occurring on hawthorn is different from the typical nymph of the apple sucker (P. mali), and has long been known as the nymph of “P. peregrina.” In it, however, there occurs a small percentage of variations, in which the characteristic brown longitudinal streak of the wing pads does not occur. Although morphologically similar, specimens of P. mali of hawthorn and apple do not mate with each other, nor do they oviposit interchangeably on each other's host plants. The nymph of either when transferred to the food plants of the other does not survive very long. 4. P. mali of the apple has a biological race on hawthorn, which has long been known as P. peregrina. This race should be distinguished as P. mali Schmidb. race peregrina, which is the name it is proposed to assipn to it. The two races, in view of their dissimilar nymphs, furnish an instance of poecilogony.