THE CYNIPIDH AFFECTING THE OAK, 29 
is concealed within the abdomen. The seta is a very 
stiff bristle united to the interior of the abdomen and 
controlled by five distinct sets of muscles. If a 
transverse section of the terebra be examined it will 
be seen that the seta occupies about half the area, 
which is circular. The spicule are alike in outline 
and serration, and occupy the remainder of the area. 
The action of the ovipositor when making a hole for 
the imsertion of an egg is very similar to the move- 
ments of the puncturing or stinging apparatus of other 
aculeate Hymenoptera; e. g. wasps and bees. 
So deeply and firmly do the organs penetrate the 
plant tissues that the insect is sometimes unable to 
withdraw them, and they are either broken off or torn 
away from the abdomen together with the mechanism 
which controls them. 
Some of the oak gall Cynipide require from fifteen 
to twenty minutes to deposit one egg (e. g. Newroterus 
leviusculus). 
The actual process of oviposition can be divided into 
three stages, which, according to Adler (‘ Alternating 
Generations,’ p. 119), are these: (1) The canal is 
bored, the ovipositor gliding under the imbricated scales 
to the base of the bud, and then being driven into the 
centre of the bud-axis. (2) The egg passes out of the 
ovarium to the base of the ovipositor, where the egg- 
stalk is pinched between the two spiculz, and the egg 
is pushed along the ovipositor. (3) After the point of 
the ovipositor is withdrawn the egg-body enters the 
pierced canal and is pushed forward by the ovipositor 
until it reaches the bottom.” 
The number of eggs deposited by a single individual 
varies. Those of the summer generations produce from 
200 to +00 eggs, the agamous generations several 
hundreds more. 
The eggs of this family are remarkable in having 
what is known as an egg-stalk which is attached to the 
anterior part of the egg. It is a continuation of the 
yolk sac, and has the function of a respiratory organ 
