(xb) 
pupal stage may affect the size of the imago in some Hetero- 
cera.—‘ I exhibit 134 specimens of Selenia bilunaria, belong- 
ing to five separate ‘families’ (by a ‘family’ I mean 
offspring of the same parents), some of the pupae of each 
‘family’ having been at a ‘forcing’ temperature, about 
80° F., the rest of each family at a ‘cool’ temperature, 
about 42° to 53° F. In looking through my rather numerous 
collection of the effects of temperature on geometrid moths I 
had been struck with the apparent difference in size between 
those in which the pupae had been forced and those in which 
they had not been forced. This seemed to me especially 
marked in the cases of Selenia bilunaria and S. tetralunaria, 
but it seemed also more or less noticeable with Pericallia 
syringaria and some of the genus Zonosoma, including Z, 
punctaria. 
“The difference in mass between the summer and the 
winter phase of Se/enia is well known, and in a paper I read 
before the International Entomological Congress at Brussels 
last year I gave reasons for the conclusion that the cause of 
this difference is temperature in the /arval stage. But the 
specimens I am now exhibiting appear to indicate that 
temperature during the pupal stage may cause substantial 
difference in mass, at least so far as wing-expanse may 
be taken as a measure of that. Knowing, however, how 
deceptive general appearance often is, and in order to be sure 
of my facts where the circumstances admitted of certainty, I 
selected as many as five families which struck me as indicating 
this difference in a marked degree, and I caused the wing 
expanse of each individual to be carefully measured by a 
qualified observer, Mr. Ricks, one of the staff of the Brighton 
Municipal Science College. The measurements were made with 
a Vernier microscope, reading to ;,'55 part of a centimetre, but 
I am informed that the results cannot be relied upon to a 
greater accuracy than ,j, of a centimetre, 7. ¢. about 54,5 of 
aninch. The following tables epitomise the results— 
