Callirhytis medularis, new species
Hosts: Quercus borealis=Q. rubra L., Q. velutina Lam., and Q. coccinea Muenchh.
Gall (pi. 1, fig. 6) : Cells are in the pith of current year's growth of various red oaks with no visible evidence until exit holes are noticed, when it is too late to secure adults. Synergus and three species of chalcids emerged the next spring, April 27 to May 3.
Habitat: The types are selected from a series of 16 females and 35 males reared by Dr. F. C. Craighead near Blain, Pa., from twigs of northern red oak, the males emerging July 15 to July 24, the females July 16 to Aug. 1, 1956, from current season's growth. He had cut out dead males and females in August 1955. Four paratypes were cut out of twigs of scarlet oak in August 1950 at Cincinnati, Ohio, by R,. B. Neiswander. From black oak are two paratypes from Vienna, two from Williamsburg, and one from East Falls Church, Va.
Nurseries at Cincinnati, Ohio, and at Southampton, Pa., reported that leaders of pin and scarlet oaks broke off where weakened by many exit holes causing lateral branches to form, resulting in poor-headed trees. The landscape superintendent at Williamsburg, Va., reported branches 12-18 inches long breaking off there. Similar cells in the pith of willow oak were noted at Durham, N. C, where 200 terminal twigs, weakened by exit holes, had been broken off or left hanging on one tree on the Duke University campus. Similar cells occur in the pith of twigs of red oak in Missouri and in blackjack and scrub oak in Virginia.
