THE HyMENopPTERA OF MINNESOTA 179 
CY NIBIDAE 
Dorsal abdominal segments not extending down the sides (as in Figitidae) so as 
to meet beneath ventral segments. All or nearly all the ventral segments visible. 
Basal joint of hind tarsi usually shorter and never much longer than joints two to 
five united. Abdomen not at all or very little longer than head and thorax combined. 
The true gall makers, affect oaks particularly. The amateur 
may well ask the question: “Why do galls take different shapes”; for 
it is a fact that “each spe- 
cies of gall insect infests a 
special part of one or more 
particular species of plant, 
and the gall made by each 
species of insect is of a 
definite form.” Cook, who 
has done much work on 
the Cynipidae believes that 
the morphological charac- 
ter of the gall depends upon 
the insect producing it, 
rather than upon the plant 
upon which it is produced ; 
Vig. 64. (Rhodites) Diplolepsis rosae L. and es as = Be 
side view of head, thorax, and abdomen. for example, galls Be 
duced by insects of a par- 
ticular genus show great similarity of structure even tho on plants 
widely separated, while galls on a particular genus of plants produced 
by insects of different genera, show great differences. 
The larval gall fly reaches its full development coincidentally with 
the full growth, or end of the vitality of the gall. On deciduous leaves, 
the vitality of the gall is shortest, ending in autumn; twig galls may 
retain their vitality all winter, or even through a second winter. The 
insect pupates in the dead protecting gall. 
In these galls, as stated, one finds not only the gall makers, but 
frequently guests or parasites. Both of these groups (commensals or 
parasites) may themselves belong to the Cynipidae. On the other 
hand, the parasites may be Braconids or Chalcids or Ichneumonids, 
while the boarders may be beetles or lepidopterous caterpillars. 
Cynips confluens Harris, is the maker of a gall known as the oak 
apple or may apple, found on the leaves of the red oak. These galls 
are sometimes two inches in diameter, green, pulpy at first, but later 
acquiring a hard shell with a spongy interior in the center of which is 
a woody kernel containing larva or pupa. 
