44 
Indiana University Studies 
of the unfolded but still immature leaves which are on the 
oaks at that season. 
The constancy of this life history thruout nearly all of the 
genus Cynips is a remarkable testimonial to the hereditary 
stability of physiologic characters. This precise combination 
of characters is found nowhere else among the gall wasps. 
Its nearest approach is in the genus Disholcaspis, which is 
certainly a close relative of Cynips. But the agamic Dishol- 
caspis emerges in the late fall, ovipositing in the veins of the 
embryonic leaves instead of in the bud scales; the bisexual 
Disholcaspis females do not emerge until mid-summer, and 
they oviposit in the bark of younger twigs of oak. 
The life history of any cynipid is determined by a variety 
of physiologic characteristics of the insect. The date at which 
the adult matures depends both upon the season at which it 
started development and upon its rate of development. The 
place of oviposition of the female depends upon the inherent 
reflex and tropistic responses of the insect to factors which 
lead them to particular parts of particular species of plants 
and which inspire oviposition in those places. The length of 
the dormant period thru which each egg goes before it finally 
hatches must depend on the nature of the egg materials and 
on the reactions of those materials to external factors. In 
Cynips the eggs go thru a mid-winter dormancy of say 16 
weeks before they hatch. The eggs of Disholcaspis require 
about 22 weeks. In each group the date of hatching is, how- 
ever, a matter of long standing. 
The mid-winter emergence of the agamic Cynips deserves 
further consideration. It is an interesting fact that we have 
bred most of our 17,000 insects of this genus out-of-doors at 
temperatures never more than perhaps fifteen degrees above 
freezing, and in many cases ten or fifteen degres (Fahrenheit) 
below freezing. When these agamic forms are at room tem- 
perature they emerge later than normally, if they emerge at 
all. Active insects brought indoors become more active for 
a few minutes, but soon they are killed by such stimulated 
activity. 
The cause of mid-winter emergence is not satisfactorily ex- 
plained, altho it has been generally accepted as inherent in 
some way within the species. Miss Payne’s studies (1925- 
1926) on the behavior of insect tissues at low temperatures 
