Sevenn and Severin—Habits of the Saw-fly . 
67 
dred and thirty-eight eggs on the left side of the mid-rib, leav¬ 
ing a difference of only four eggs. Undoubtedly the femaU 
does not prefer either side of the mid-rib in depositing her 
eggs, it being simply a matter of chance on which side of the 
leaf she happens to alight. 
The position of the receptacle within the leaf is nearly con¬ 
stant; it is usually found above the lower epidermis. Among 
the one hundred leaves of the peach-leaved willow there were 
no receptacles cut below the upper epidermis, but among the 
one hundred, leaves of the long-leaved willows there were six* 
teen leaves with eggs deposited below the upper epidermis and 
three leaves containing eggs both above the lower and below 
the upper epidermis. The total number of eggs deposited 
below the upper epidermis was sixty-three, out of which fifty - 
six eggs hatched. Undoubtedly the deposition of the egg below 
tbe upper epidermis of the leaf does not hinder the develop¬ 
ment of the eggs. 
It is worthy of notice that the saw-fly does not deposit her 
eggs indiscriminately on all the leaves of the willow. On the 
various species of willows which we examined no eggs were 
ever found on the younger leaves of the plant. Perhaps this 
avoidance of the youngest leaves may be because of their too 
rapid expansion, which would interfere with the development 
of the ovum. 
The number of eggs one female deposits may exceed five 
hundred. A dissection of the female reproductive organs 
shows that each ovary is made up of a variable number of ova¬ 
rian tubules or ovarioles. In six specimens dissected, the aver¬ 
age number of ovarian tubules in the right ovary was twenty- 
six and in the left twenty-five, although as many as thirty and 
sometimes only twenty-one were found. The following table 
shows the number of ovarioles found in each ovary and the 
total number found in both ovaries of the six specimens dis¬ 
sected. 
