Neuroterus engelmanni Kinsey.

Quercus engelmanni
Leaf galls, integral
Fig 139. Small cells in numbers on leaf.

Fig 139. Q-engelmanni. The types emerged after Feb. 26 (Fallbrook).

Neuroterus engelmanni, new species

Galls (Pl. XXIV, Fig. 4). —Pustulate swellings embedded in the leaf-tissue; monothalamous, but often several galls confluent; about circular, averaging 1.2 mm. in diameter. The surface of the leaf not modified, the undersurface somewhat distended, the upper surface less so but very evidently swollen; thin-walled, hollow. On leaves of Quercus engelmannii.

Range: —California: Alpine, Fallbrook.

The galls were very abundant on the few trees on which they were found. On February 24 and 26 they contained only larvae. Of the two or three thousand insects bred from one of the lots of galls, only eleven gall-makers were recovered, the other insects being parasites. The galls closely resemble Neuroterus niger Gillette which occurs on Quercus macrocarpe, N. perminimus Bassett on Q. alba, N. papillosus Beutenmuller on Q. bicolor, and several other species which I shall describe from other species of oaks. The insects of these species show evident relationships morphologically, and it is of considerable significance to find the galls (an expression of the physiology of the insect!) similarly related. These species are certainly distinct, but it may be desirable at some time to label them varieties. Such "host varieties" are biologically important because of the material they may offer for experimental work on the possible effect of environment (the host) on the insect.

Neuroterus niger variety engelmanni, agamic form

Hosts: Quercus engelmanni

GALL. — About circular, with rather well-defined boundaries, often with an indefinite central point on the upper surface. On Quercus engelmannii (fig. 39).

RANGE. — California; Alpine, Fallbrook. Probably confined to the limited range of Quercus Engelmannii, in southern California and adjacent Mexico.