718 JOURNAL, BOMBAY NATURAL HISTORY SOCIETY, Vol. XVII. 



Summary 1905. 



Mouth. 



Mean. 



'iighe>t 

 residing. 



Lowest 

 reading 



Maxim 

 imi vari- 

 ation. 



Kain- 

 fal). 



Wot 

 days. 



Insects captured. 



January (24 days ) 



February .. .. 



March 



April 



May 



June 



July 



August 



September .. 



October 



November . . 



December .. 



73 '■ 

 73-8 

 71 

 701 

 6V5 

 63-9 | 

 61-9 | 

 63 I 

 65-2 j 

 66U I 

 67-5 I 

 70-5 I 



All " wet." 



Dltio. 



Ditto. 



Ditto. 

 W.ll. 1.3. D. 2. 

 \V. 7. I. 6 D.18. 

 w. 2. I. 7. D 20. 

 W. 0.1.4- D.15. 

 W. 2. I 3. D.ll. 

 W. i). 1 .5. D.9. 

 W. St. I 5. b.4. 

 W. 15. I. 9. D.l. 



Conclusions. 

 On the hypothesis that the seasonal form is determined in the last few days of 

 pupal life, we may draw the following conclusions from the above observations : — 



1. When the mean temperature falls below 70° F., the "dry" forms ap- 

 pear, and the lower the mean the more numerous they become. 



2. When the temperature is lowest, the " dry " forms are most numerous 

 and conversely. As an instance, July, the coldest month, mean +68*— 61*9, 

 shows the greatest number of "dry" forms, though there were !i3 wet days 

 and a rainfall of 10*77 inches. February the hottest month, mean + 79'S — 

 68*6, shows no " dry" forms, though the rainfall was only 7*92 inches. 



3. It is not therefore a dry or humid atmosphere that produces a " dry " 

 or " wet "' form, but a low or high temperature. 



The following experiments were undertaken with a view to testing whether 

 the hypothesis is sound, that the seasonal forms are dependent on changes in 

 the pupal state. For this purpose pupse within twenty- four hours of their 

 last ecdysis were placed under the following conditions. The modus operandi 

 I will give more fully subsequently ; at present it would confuse the issues. 



Conditions, 



Average tem- 

 perature 



Average 

 d»ys iu pupse 



Number of 

 I upae I 



Results. 



20 



20 



12 

 4 

 8 



Id 



•I. d. 1. W. 1. Kemainder died. 



All cripples. D. i.I. d. 8. 



All diea immature. 

 W.2.1 w.2.i.d.2 .Remainder died . 



* Dr. Dixey his sub-divided the Intermediate -forms into Intermediate wet and Intermedi- 

 ate dry, and the sub-division is a useful one. In order to simplify matters I combined the 

 two under one heading iu the first t .bles, but in these latter experiments the sub-diviion is 

 imperative. There is, of course, no hard and fast lice between the two intermediates and each 

 individual must use his own standard. My own ideas areas follows. By Intermediate dry 

 I mean an insect ( Melanilis) with pronounced median fascia : subapxal and bis.il fasciae 

 distinct. Urouu'i colour, more or less uniform not miuutely .-triated. Ocellated spots 

 clearly marked, but ii is absent or incefiuite. Outer margin of win bolow apes more or less 

 but still distinctly falcate. Inttrm diate wet, fasciae iudistinct or almost absent, ground 

 colour uniformly coloured and mioutely s-triated. OcelLited spots c.eurly marked, the iris 

 present* but indefinite. Outer margin of wing almost even, especially in the male. 



