Seasonal Dimorphism in Butterjiics. 209 



as the result of the different treatment are more easily 

 visible in the first series than in the second. 



The Hope collection also possesses seven specimens of 

 the above-mentioned series of Crenis hoisduvalii, Wallgrn. 

 These are a pair of the " dry heat" emergence on April 14 ; 

 a pair of the "damp tin" emergence on April 15; and a 

 male and two females which emerged under normal con- 

 ditions, also on April 15. There is no doubt that the 

 "dry heat" female is considerably lighter on the upper 

 surface, and has the dark marks on the under surface of 

 the forewings less distinctly marked than any of the 

 others. The differences between the males are of the 

 same kind, but somewhat less apparent. 



" Aug. 29, 1899. — I am sending you by this mail a small 

 lot of butterflies, including the bred P. sesamus and archcsia, 

 and twenty-one bred specimens of Teracolus omphale and 

 T. acJmic, with their respective parents. . . . The Teracoli 

 will be valuable as actually proving seasonal dimorphism 

 in these species. I must admit that I was much surprised 

 to find that the warm, damp atmosphere had no effect on 

 T. omphale (Di — 4) whatever.* The apparatus I used was 

 a very deep circular tin (uncovered), which was partially 

 filled with water, in which was placed a stand ; to this 

 the pupse were pinned, they being about four inches above 

 the water. In the case of T. omphale (Di— 4) I kept the 

 spirit-lamp with only a tiny flame, so as to keep the water 

 just hot, and so that a faint warmth could always be felt 

 on placing the hand above the mouth of the containing tin. 

 On account of the negative results thus obtained, I came 

 to the conclusion that the heat applied was perhaps in- 

 sufficient in all these cases. Unfortunately, I had not 

 enough material left to test this properly, but in the case 

 of T. achine (Ci and C2) I kept the water at about 

 180° F., still keeping the tin uncovered, and, as you will 

 see, this has undoubtedly had a more decided effect, espe- 

 cially in the case of C2, which was put in before actual 

 pupation. I was, however, surprised that with Ci the 

 protectively coloured under side should have been affected, 

 rather than the black markings of the upper side. In 

 view of this result I think the previous experiments must 

 not be taken as conclusive. Among the Teracoli there 



* It. appears to nie to have had a slight effect, as can be seen on 

 comparing D2, D3 and D4 with D5, D6 and D7. See pp. 211-13. — 

 r. A. D. 



