Kinsey : Gall Wasp Genus Cynips 
43 
developed, with a more pronounced development of the col- 
lenchyma layer. In Besbicus all five layers are again present 
(with the parenchyma most so in mirabilis) . In Philonix 
the development is chiefly that of a rather solid spongy paren- 
chyma. In Atrusca it is a parenchyma with few but tremen- 
dously extended fibers. In Acraspis all five layers are 
developed among the species centering about Cynips mellea, 
but in the other specific stocks in Acraspis the protective and 
parenchyma zones seem absent and the collenchyma and epi- 
dermal layers are unusually well developed. 
The gall-producing stimulus, whatever its origin, is evi- 
dently selective in its effects upon particular plant tissues; 
and, since the gall characters are usually of subgeneric signifi- 
cance, it is apparent that these peculiarities of the gall-pro- 
ducing stimuli are of as ancient standing as any of the 
morphologic structures of the insects. This means that these 
physiologic qualities have been constant in heredity for pos- 
sibly ten or twenty million years during which the specific 
stocks of Cynips have been differentiated. 
The second body of data on the physiologic inheritance of 
species is concerned with life histories in Cynips . Like most 
of the other higher gall wasps, these insects have an alterna- 
tion of a bisexual and an agamic generation. Thruout the 
groups the life history data are so uniform that it may be 
readily summarized. 
The agamic insect develops in a gall which appears on the 
leaves early in the summer. The gall is mature by the end 
of the summer, and the insect matures and transforms into 
an adult early in the fall. Then — the most unique feature of 
the genus — the adult continues in the gall, chewing an exit 
passage thru everything except the epidermis of the struc- 
ture, but not emerging until very late in the fall or some time 
in the winter. Most of the emergence is in mid-winter. The 
agamic females oviposit within the scales of unopened buds 
on the trees. The bisexual galls do not begin development 
until the leaves begin to unfold on the trees in the spring. 
These galls are simple, seed-like or bladdery, thin-shelled de- 
velopments usually not larger than the buds within which 
they occur. The bisexual insects mature within three or four 
weeks, emerging in the middle of the spring. They copulate 
and oviposit in the main veins, usually on the under surfaces 
