1912.] 



NATURAL SCIENCES OF PHILADELPHIA. 



277 



STATISTICAL STUDIES ON VARIATION IN THE WING-LENGTH OF A 

 BUTTERFLY OF THE SUBFAMILY SATYRINJE. 



BY T. FUKUDA. 



As is well known, the distinction of sex, generation, or habitat in 

 any species of butterfly may sometimes be a definite cause of the 

 differences in size. The aim of the pre sent report is to determine 

 statistically the degree of such differences found under these cir- 

 cumstances. 



Material. 



Ypthima philomera var. argus', which I selected for the material 

 of this work, is a small butterfly of the subfamily Satyrinse commonly 

 found in Japan. Judging from my observations and breeding 

 experiments, this species most likely repeats its life-cycle three 

 times during one year, at least in all the warmer districts of this 

 country, the butterflies appearing in succession, April-May (first 

 generation), June-July (second generation), and August-October 

 (third generation). The details of the material are shown in Table I. 



Table I. 



Lot, 



I 



II 



III 



IV 



V 



VI 



Date. 



11-15, V, 1910 

 13-17, VII, " 

 20-24, IX, 

 20-24, VIII, 1909 

 28-30, VIII, 1910 

 19-22, VIII, " 



Locality. 



Kawanabe, Prov. Satsuma. 



Himeji, Prov. Harima. 



n a tt 



Tsumago, Prov. Shinano. 



All the individuals of one and the same lot were captured by 

 myself within an area about two miles in diameter. ' There is scarcely 

 any doubt that Lots I— III belong to the corresponding generations 

 of 1910, while Lots IV and V are most likely the representatives of 

 the third. Having come from a comparatively cold district, Lot 

 VI probably consists of the individuals of the second generation. 



1 Kawanabe, Prov. Satsuma, 20 miles south of Kagoshima, nearly at the 

 southern extremity of Kiushiu; Himeji, Prov. Harima, 35 miles west of Kobe; 

 Tsumago, Prov. Shinano, 60 miles northeast of Nagoya. 



