80 
Indiana University Studies 
hypertrophy, and in a few cases a considerable swelling. Any 
growing part of the plant is attacked, and the form of the 
gall (see duhius, minutus , Sind quercicola) is very largely deter- 
mined by the nature of the plant tissue involved, — both of 
which are very primitive characteristics even in a genus like 
Neuroterus. The female insects show most of the primitive 
characteristics of subgenus Diplohius, differing mainly in hav- 
ing some hairs on the face, the thorax roughened, and the 
radial cell of moderate width. The males, however, are a 
distinct advance over Diplohius males, differing from the 
females in color (in most cases a considerable difference), 
in the lengthened thorax, the moderately enlarged eyes, and 
the slightly curved third antennal segment. These male char- 
acters are furthest differentiated in the species irregularis, 
and it is unfortunate that the most extreme species must 
serve as the type of the subgenus. The similarly simple galls 
of all Dolichostrophus species, and several of the insect struct- 
ures point out the unity of the group, as do also the known 
life histories which are all very simple alternations of very 
similar, largely identical insects, and of galls which are clearly 
similar but differ as different parts of the plant are attacked. 
However, the several species are so distinct that they evidence 
quite diverse evolution along at least three different lines. 
Two pairs of species, minutus and quercicola, and irregularis 
and decipiens, are eastern and western developments of one 
primitive type; the two stem gall species, batatus and rileyi, 
show some distant relationships, with contortus still less close- 
ly connected ; and the species duhius has a simple but distinct 
development along another path. 
Neuroterus (Dolichostrophus) batatus (Fitch) 
Figures 56, 61 
FEMALE. — Head largely piceous or black; antenna brown, the first 
three or four segments yellow, with 13 segments, the third half again as 
long as the fourth; thorax entirely black, more or less longer than wide 
and high, as broad as or broader than the head; mesonotum and scutel- 
lum distinctly but finely coriaceous, almost naked of hairs; mesopleurse 
finely roughened; abdomen black, moderately larger than the thorax, 
produced or not, sharply triangulate; legs yellow, the coxse, the centers 
of all femora, and the hind tibiae brown; areolet rather large to small; 
the first abscissa angulate or arcuate; length 1.2-2. 2 mm. 
