Phylloxera rimosalis Pergande, n. sp.
A very large and conspicuous gall, growing always upon the leaves of Hicoria tomentosa, bearing a great resemblance to the gall of Ph. c.-scissa, from which it differs in the round, not elongated, orifice and in some other characters.
It is not uncommon along the Potomac near Washington and affects more generally the terminal leaves of the more succulent young shoots. It matures somewhat later than most of the other galls, the first winged females occuring the latter part of May. It grows generally singly, though occasionally 2-4 may occur on the same leaf, in which case they tend to become more or less confluent, so as to form a large, flat mass ; each retaining, however, its cell independently. It forms upon any part of the leaf, often very close to the edge, and may extend across two or even three of the transverse veins, (when the upper surface becomes somewhat uneven) but never, as far as observed, across the midrib. The horizontal diameter ranges between 3-11 mm (those growing singly being usually much the largest) and between 1.6-3.4 mm in height. The form is quite flat or but slightly convex above, with the circumference usually sharply defined and sunken below the plane of the leaf, which forms around it a somewhat elevated and quite sharp edge or rim. The disk may be raised button-like above the plane of the leaf. Sometimes the upper surface is slightly uneven or concave; or there may be a slightly convex, central elevation, with a dimpled depression on one side of it. Beneath it is much more prominent and convex, resembling somewhat that of c. -septum, except that its nipple is extremely short and conical, with the orifice round and completely closed in the younger ones, with indications that it will split when mature into 5-8 short bracts, which are closely covered at the tip and inner side with minute, white, silken hairs. The surface above is perfectly smooth, whilst the under side is sparsely beset with short, pale yellowish, radiating hairs and yellow papillae which characterize the under side of the leaves.
It is seen to be slightly transparent, if held between the light, especially around its margin. Its walls are rather thick and hard, especially at the base. The color above and beneath is of a somewhat paler green than the surrounding surface of the leaf, occasionally faintly tinted with red at the centre and polished above.
Each gall contains, by the middle of May, besides the single stem-mother, large numbers of eggs, larvae and young pupae, covering closely its inner walls, each with the end of the body directed toward the centre, as if they were standing on their heads. Some individuals acquire wings by about the 20th, while the majority do not reach this condition till the end of the month or the first week in June.”
- Theo. Pergande: (1904) North American Phylloxerinae affecting hicoria (Carya) and other trees©