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IV. Systematic temperature ex-perimcnts on some Lepi- 

 doptera in all their stages. By Fkederic Merri- 



FIELD, F.E.S. 



[Read December 4th, 1889.] 

 Plates IV. & V. 



The experiments made last year on the effect of tem- 

 perature upon some Lepidoptera in various stages 

 suggested so many points for further investigation that 

 I determined to pursue my inquiries in a more syste- 

 matic way this year. Therefore, instead of sending 

 pupae away to be iced, I provided myself with a 

 refrigerator, in which I ascertained that the temperature 

 ranged during the summer from about 39°, when freshly 

 filled with ice, to about 55° (or even higher in warm 

 weather) when most of the ice had melted ; 47° was 

 about the usual summer temperature ; in spring and 

 autumn the temperature was sometimes below 39°, and 

 I think about 43° was the average in these seasons. 

 This refrigerator temperature I speak of hereafter as 

 " cool." Inside the refrigerator, however, I had an ice- 

 box, where the temperature was uniformly 33"^ ; this is 

 where I kept the insects spoken of as "iced." I had, 

 besides, two forcing-boxes, and the " forcing " tempera- 

 ture must be understood as about 80° unless otherwise 

 stated. 



I had two main objects in view; one to find what 

 exposure to a low temperature could be borne in the 

 different stages, the other to ascertain the effect of 

 temperature, applied in stages anterior to the last, on 

 the colour and markings of the perfect insect, and 

 incidentally I hoped to throw light on some other 

 questions. 



As to the first object in view, I hoped the experiments 

 might throw some light on the capability of the insect 

 to pass the season of winter in some different stage from 

 that in which it is now passed. It is well known that 



TRANS, ENT. SOC. LOND. 1890. — PART I. (APRIL.) K 2 



