Neuroterus (Diplobius) verrucarum (Osten Sacken)
agamic forms
[Kinsey gives lengthy series of varieties by host, region, and morphology now treated as synonyms of N quercusverrucarum:
var exiguissimus Bassett - Quercus alba; MA, RI, CT.
var inficiens Kinsey - Quercus breviloba; TX
var macrocarpae Kinsey - Quercus macrocarpa; TX, OK, LA
var opacus Kinsey - Quercus stellata, breviloba; TX, OK, LA
var pulvinus Kinsey - Quercus stellata; TX
var restrictus Kinsey - Quercus chapmanii, margarettae; FL, GA
var verrucarum Kinsey - Quercus stellata; DC, VA
Three of his varieties, var minutissimus on live oaks and vars floccosus and pernotus (=floccosus) on Quercus macrocarpa and bicolor, are now recognized as valid species distinct from quercusverrucarum.]
GALL. — A minute cell covered with a flattened disc of wool. Monothalamous. Each gall a smooth, seed-like cell, hard, thin-shelled, entirely hollow, attached by a small point to a leaf-vein, separable, but the leaf depressed so at the point of attachment that the gall is not easily detached; the cell covered with a dense, whitish mass of wool which dries brown, the wool somewhat flattened, disc-shape, varying in diameter from 0.7 mm. in one variety to 3.5 mm. in another, averaging 2.5 mm. Attached to veins on the under surfaces of the leaves; indicated on the upper surfaces by a smooth, naked, circular, papilla elevation with a slight indication of a central point, this papilla however almost lacking in a couple of varieties. On leaves of white oaks except the chestnut oaks (figs. 32, 33).
RANGE. — Ontario to Minnesota, Florida, and Texas. Apparently confined to the eastern half of North America. This very common species has developed varieties in which the insects are usually distinguishable only by slight differences in size, color, and size of the areolet. These differences would not be enough to warrant the recognition of distinct groups, except that they are very constant in large series representing several localities of a single faunal area, and are correlated to a large degree with host and distributional data. Nevertheless in some cases I have not been able to distinguish material from undoubtedly distinct faunal areas. The galls of the several varieties differ mostly in regard to average size. Many of the varieties are confined to single hosts in distinct faunal areas ; in a few cases a variety seems to occur on two closely related oaks or over two adjacent areas. Pulvinus is a variety with a very distinct gall but the insect is indistinguishable from opacus. The species is closely related to Neuroterus niger which is evidently a more primitive species. The degree of separability and the distinct form of the gall of verrucarum, its restriction to eastern North America, and its exclusion from the chestnut oaks, all suggest something of specialization. The best key characters for the insect of verrucarum are the small abdomen and the slightly and smoothly curved first abscissa of the radius; the eyes are smaller and the cheeks are wider than in niger. The known life history data are much the same for all of the varieties. The galls are first seen after mid-summer, in August further north, probably earlier further south; the larvae do not mature until late in the fall or early in the winter, then quickly becoming adults which remain in the galls on the dead leaves over winter, emerging in the early spring, March or earlier in the south to May further north. This is as much as is known of the species, the bisexual form not being known. It is probable that an obscure bud or flower gall, probably monothalamous, will prove to be the alternate of the agamic verrucarum.
