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 Miss Clarke, Thompson, and other students of the family have made observations confirming Bassett's statements, and there can be no doubt of the regular alternation of these forms, even though the data has not been checked by experimental work. This was the fourth and last instance of heterogeny discovered by Bassett.

The galls of this form appear when the young leaves first unfold in May and, like most of the spring galls of dimorphic species, grow very rapidly to maturity. The adults are known to emerge from June 12 to July 5. They occur in about equal numbers of the sexes: I counted 276 females and 233 males in one lot bred by Millett T. Thompson. After fertilization the females oviposit in the new wood of the twigs, usually not far from the galls in which they have developed.

Neuroterus noxiosus form noxiosus (Bassett) Plate XXIX, Figures 17 to 19

—Almost identical with the female vernalis, with the thorax and abdomen more piceous, especially at the base of the abdomen; the anterior parallel lines on the mesonotum more distinct, the abdomen relatively larger and more angulate; the wing veins slightly darker brown; the whole length 1.6-2.0 mm.

—Irregular, elongate, woody swellings (Figs. 17 to 19) of young stems and sometimes petioles. Polythalamous. About 60×10 mm., roughly cylindrical, but often very irregularly twisted, etc. Inseparable from the plant. Bark-colored, usually with a glaucous bloom. Internally the gall is closely packed with larval cells which are distinct but not separable from the surrounding woody tissue. On the newer growth of Quercus bicolor, Q. Prinus, and possibly other oaks.

—Cotype females, males, and galls in The American Museum of Natural History, the Academy of Natural Sciences of Philadelphia, and the Museum of Comparative Zoology.

This gall is the better-known form of the species, due apparently to its longer persistence on the tree. The gall very closely resembles that of Neuroterus batatus batatus, from specimens of which it is often difficult to distinguish this species. The more highly distinct larval cells of noxiosus is often a good basis for making the distinction. The most certain test, however, is the species of the host plant, noxiosus being confined as far as known to Quercus bicolor and Q. Prinus, while batatus occurs on Q. alba. It would prove interesting to try to induce one of these species to oviposit on the "wrong" species of oak, and to observe if galls and what galls were produced.

The larvæ of noxiosus overwinter in the galls, emerging the following spring from March 24 through April to early May.

Neuroterus tectus Bassett

Neuroterus tectus BASSETT, 1900, Trans. Amer. Ent. Soc., XXVI, p. 331. , 1902, Gen. Ins., Hymen., Cynip., p. 51; 1910, Das