136 Mr. F. Merrifield's systematic temperature 



condition — did not seem in the least injurious to it. 

 Cooling the pupating larva, which at an ordinary 

 summer temperature turns in 3 or 4 days, sometimes 

 protracted the period to 14 days. 



(3) General results of j)reliminary icing experiments. — 

 These experiments show that not only is exposure to 

 cold in the soft green condition not fatal or necessarily 

 injurious to the species experimented on, but that the 

 pupation of these summer pup?e will take place in some 

 species at the low temperature of 33°, at which tempera- 

 ture therefore the necessary physiological changes must 

 go on, though with extreme slowness. A curious proof 

 is afforded of the harmlessness of the exposure to cold 

 of soft green pups of illustraria by the exhibition I 

 make of the pupa-cases of 3 that pupated at 33°, and 

 the perfect moths which came out of them ; it will be 

 seen by inspection of the former that by lying so long 

 in a soft condition, owing to the slowness with which 

 they hardened at the low temperature, the pupae became 

 flattened on the lower side like sausages lying on a 

 counter. There are indications that icing, not pro- 

 tracted, may be injurious to the summer jnipa of 

 illustraria in one stage, and in one stage only — viz., 

 that in which the pupa is going through the period 

 which separates the central lethargic period from emer- 

 gence ; and it seems not injurious even here, if the 

 exposure is limited to that very last pupal state of all, 

 when the insect is fully formed in the pupa-case, and is 

 only awaiting the usual time of day to emerge as a 

 moth. 



On the other hand, the considerable proportion of 

 deaths and of cripples (see the Tables), and the irregu- 

 larity of the period of emergence after the pupae were 

 taken out of ice or of the cooling temperature show 

 that long exposure to cold of these ennomos pupae, which 

 have only a summer existence, is very injurious and 

 disturbing to them. 



(4) Systematic experiments as to the effect of temperature 

 on the colour and markings of the imago with autumnaria. — 

 These experiments were directed to several ends. The 

 first was to ascertain beyond doubt whether it was in 

 the larval or in the pupal stage that the low temperature 

 operated, or chiefly operated, on the colour of the 

 moth, and I think in this respect they have yielded very 



