564 L. DONCASTER. 
do so in the pupa is shown by von Siebold’s experiments, and 
since often all the eggs hatch, it cannot be in the egg. I 
have reared a number of eggs in the hope of answering this 
question, but my results are hitherto uncertain, for I have 
never succeeded in rearing as much as 50 per cent. of the 
unfertilised eggs up to the imago. This is partly due to the 
exceptionally dry summer of 1904, which caused a greater 
mortality among the young larve than in 1903. It seems 
certain, however, that a much larger percentage of eggs of 
impregnated females grow up to imagines than from unfer- 
tilised. From eggs of impregnated females a large but 
varying percentage of female flies is produced; frequently 
considerably over 50 per cent. are females, and this suggests 
that the male larve are more delicate, so that the high 
mortality among larve from virgin eggs may be so accounted 
for, and since it is the common experience of those interested 
in sawflies that the females are more hardy than the males, it 
seems unlikely that all should die off when the eggs are not 
fertilised.) I must, however, leave the question open until 
next summer, when I hope to be able to settle it definitely. 
2. MavrerRIAL AND MeErTgops. 
‘The eggs are generally laid on the under side of the leaf 
of the food plant, and they are nearly always arranged so 
that the anterior end of the egg lies away from the base of 
the leaf. In N. ribesii the female, when laying, stands 
with the head directed towards the base of the leaf, and in 
attaching the egg to the groove made by the saw turns the 
abdomen so far over that the front end of the egg, which lay 
forward in the ovarian tube, lies backward when it is laid. 
The eggs are laid usually at intervals of about a minute, and 
of any row that nearest the edge of the leaf is the first laid, 
that nearest the base the youngest. I have not observed the 
1 It cannot be said that the unfertilized female lays the male eggs and 
keeps back the female, for a female will lay about 100 eggs and then die, and 
I find that only three or four eggs remain in the ovarian tubes. 
