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XX. On certain temperature Torms of Japanese Butterflies. 

 By H. Pryer, C.M.Z.S., &c. 



[Read August 2ucl, 1882.] 



In the following paper I- have used the term " tempera- 

 ture " in i^reference to "seasonal," as the latter word 

 appears to me to insufficiently indicate the changes 

 which take place in many of the Japanese hutterflies 

 which appear more than once in the course of a year. 



The changes appear to me to depend not so much on 

 the season of the appearance of the perfect insect as on 

 the temperature the larva has borne during its existence ; 

 frequently also an odd specimen of the sprnig form will 

 put in an appearance in summer, and again the summer 

 forms will sometimes appear late in the autumn. To 

 illustrate this I will give an instance which came under 

 my notice five years ago. I then visited Boshiu and 

 Kadzusa, on the opposite side of Tolsiyo Bay, the ex- 

 tremity of Boshiu being always markedly warmer than 

 the neighbourhood of Yokohama. It was m the month 

 of November, and I found there the black summer form 

 of Polyommatus Phlaas in abundance, while as I worked 

 further north up the Bay this was replaced by the 

 . brightly-coloured spring and autumn form. 



Our seasons are pretty evenly divided ; the latter hall 

 of December, all January, February, and the first half 

 of March being winter ; the latter part of March, all 

 April, May, and June, spring ; July, August, September 

 summer; October, November, and the first halt ot 

 December autumn. 



Yokohama is situated on a plain intersected by many 

 cultivated valleys, the land seldom rising over 100 feet 

 in elevation ; to the north the plain extends about eighty 

 miles to the Nikko range, the nearest mountain to Yoko- 

 hama being Ohoyama, in Sagami, twenty-six miles 

 distant west. This plain, which includes both Yokohama 

 and Tokiyo districts, forms the province of Musashi. 



Temperature. — The variations in course of the year, 



TRANS. ENT. SOC. 1882v— PART III. (SEPT.) 



