Pedigree Moth-breeding. 127 
me, as I judge, to estimate differences amounting to the 
tenth of a millimetre, and I do not think all sources of 
error taken together would much exceed a quarter of a 
millimetre. It was not, however, until after I measured 
my sleeved wlunaria on the 22nd July that I attained 
to this amount of accuracy, and therefore my earlier 
measurements must be taken as only approximate ; but 
I think the general results are not far wrong. I should 
add that the ‘‘crease’”’ cannot always be found, especially 
where the moth is very hairy; experience will tell the 
observer where it should be, and if the same person 
always measures, not much addition need be made to 
the percentage of error on account of the absence of the 
‘‘crease.’’ All measurements are of one wing only, so 
that the ‘‘expansion of wings’ would be double the 
measurement given, plus about 3°5 mm. for the width of 
the body between the wings at the point measured. ‘The 
‘‘ expansion of wings,” however, measured from tip to tip 
of a moth set in the English fashion, would be about 
1 mm. less than double the expansion of the single wing, 
owing to the inclination downwards and forwards. 
After the moths had been measured, they were paired 
off in cylindrical muslin bags kept open by wire frames, 
each about 8 or 9 inches by 5; these bags, except where 
otherwise stated, were kept on a shelf outside the window 
of a cool room facing W.N.W., and protected from heavy 
rain; and there the moths laid their eggs, generally 
scattered over the muslin, and preferably in folds. I 
_ gave up inserting sprigs of the food-plant, as I found 
they rarely took any notice of them. The eggs, which 
will bear rough handling, were detached by hand or by 
the back of a knife, &c. 
Nearly all the facts recorded are from my own personal 
observation, as I did not leave home for more than three 
or four days at a time, except during the last ten days 
of September and less than a week at the end of October, 
and on these occasions | had an efficient locum tenens, 
who had acted as my assistant at other times. 
I have a more or less full record in most cases of the 
number of eggs laid, the number hatched, the number 
of moths that pupated and of moths of each sex that 
emerged, with dates and measurements, all of which may 
be useful for reference before the experiments are brought 
to a close, and which will, I hope, be dealt with by 
