Page:The Gall Wasp Genus Cynips.pdf/92

 ; the legs often darker in some small part; the wings at least relatively longer than in the female; the spotting in the cubital cell lighter or heavier than in the female; length slightly greater than in the female, the legs apparently longer than in the female.

GALL OF AGAMIC FORMS.—Usually monothalamous (polythalamous in pezomachoides). Fundamentally spherical tho often much distorted in surface outline. The thin lining of the larval cell constitutes the nutritive layer; the cell wall (lacking in most of Acraspis) constitutes the protective layer; the bulk of the gall (except in Acraspis) is made up of a thinly or densely fibrous or a more compact parenchyma layer which holds the larval cell centrally and, in a few species (including all of Antron), contains a second, unoccupied cavity; an outermost hardened layer (constituting the bulk of the gall in Acraspis) is the collenchyma layer; and the epidermal layer is usually naked or finely pubescent, in Acraspis becoming contorted into a faceted surface sometimes coated with long spines or wool-like processes. Attached by only a small point (and therefore easily separable) on a main vein, usually on the under surface (less often on the upper surface, rarely on the petioles or young twigs) of leaves of white oaks; known from every group of white oaks that occurs in the regions inhabited by these insects.

GALL OF BISEXUAL FORM.—Monothalamous. A small, thin-walled, hard-shelled, largely naked, roughly egg-shaped or simple seed-like cell; or a larger thin-walled, more succulent, irregularly bladdery capsule; in either case without well differentiated layers of tissue or unusual epidermal development and without a differentiated larval cell except the central cavity of the gall; always within young buds, often completely enclosed by the unopened bud; closely connected to the young or older twigs or (in adventitious buds) on the bark of the older trunks; on white oaks of the same species which harbor the agamic generation of the insect.

RANGE.—Known from North America from southern Canada to central Mexico, from Europe wherever oaks occur, and from the borders of Asia and Africa on the Mediterranean Sea; not known, but to be expected from the rest of Asia wherever oaks occur. Figure 7.

GENOTYPE.—Cynips folii Linnaeus. Designated by Westwood, 1840, Generic Synop.: 56. See the discussion under the European subgenus Cynips.

The genus is here divided into six subgenera, Cynips, Antron, Besbicus, Philonix, Atrusca, and Acraspis, under each of which the systematic and biologic data are presented.