594. MISC. PUBLICATION 657, U. S. DEPT. OF AGRICULTURE 
It is remarkable that each species of the gall insects infests a special 
part of one or more species of plant. Even when the branches of 
several trees of one species intertwine, one tree may be loaded with 
galls, while the others are nearly or entirely free of them. Further- 
more, the galls produced by different species are of such definite forms 
that they can be classified according to the species that produced it. 
Felt (153) prepared a useful manual, i in which galls of many orders of 
insects are illustrated. 
The cynipids are very restricted in their host relations. Kinsey 
(264) estimated that 86 percent of the known species of gall wasps 
produce galls on @wercus and are confined to that genus. Another 
7 percent are restricted to species of Rosa and the remaining 7 per- 
cent are found on plants belonging to 35 genera of Angiosperms, more 
especially the Compositae. Felt (153. ye noted that there were 805 
species of gall wasps and 731 of these occurred on oaks. 
The eynipids are of relatively shght importance from an economic 
standpoint. A few insect galls are commercially valuable. Some 
have long been used in the manufacture of ink and in dyeing and tan- 
ning, and some provide winter food for bees. Kinsey (265) gave an 
excellent account of their economic importance and estimated that 
there are not more than 5 or 6 complexes, including possibly 10 species 
that do any appreciable damage. Three of these ¢ species are confined 
to the Pacific coast area. Appreciable damage is inflicted only by 
species that produce galls involving a considerable portion of the 
cambium or young twigs, although some undoubtedly destroy in- 
fested acorns. All the species listed by Kinsey in 1935 as causing 
some economic damage in the eastern part of the United States form 
twig or stem galls. “These, plus a few that form common galls on 
leaves, stems, flowers, and seeds are described in the following para- 
graphs. Felt (753) listed 41 species that form root galls, but they 
are of minor importance. 
STEM GALLS 
The stem swellings caused by Callirhytis floridana (Ashm.) are 
found covered with normal bark in the fall. They look hard and 
woody, but when cut into they are found to consist of a thick layer 
of soft, white, parenchymatous tissue which cuts like cheese, the 
numerous cells being imbedded next to the true wood. Galls range 
from 1% inch to 3 or more inches long and are not more than 14 inch 
in diameter. They are formed close to the ground on the lower 
branches. Galls taken by Weld (429) in Missouri contained pupae 
when examined in November, the adults emerging in the spring. The 
species is generally distributed over the southeastern part of the 
United States and westward into Texas. It has been recorded from 
Chapman oak (Q. chapmaniz), post oak (Q. stel/ata), and dwarf post 
oak (V. stellata margaretta). WKinsey (265) reported large acreages 
of Q. ‘stellata margaretta nearly k ied by this gall wasp in eastern 
North Carolina in 1935, and damaging infestations as far west as 
Louisiana. He considers Q. stellata margaretta as practically worth- 
less except as a ground cover, and notes that C. floridana has not been 
observed in abundance on the more valuable Q. sted/ata. Where prac- 
ticable, pruning would probably give effective control. 
Callirhytis (Andricus) punctata (Bassett), the gouty oak gall 
(fig. 176), infests the twigs and smaller limbs of red oak (Quercus 
