MIMETIC ASSOCIATIONS 



27 



of chrysippus. Should the weather become dry, or a drought set in, and the larva possibly 

 have to aestivate, then the conditions will be favourable to the appearance of klugii 

 {dorippus) ; though I consider that chrysippus will always prove to be the predominant 

 form, and that even under the most favourable conditions klugii [dorippus) will never 

 surpass, perhaps never even equal it in numbers. The white on the hind-wing of the 

 secondary group, alcippus and dorippus [albinus], I look on as the brand of humidity affecting 

 the butterfly while in the pupa stage at a most susceptible stage of its existence. The pupa 

 skin has, I believe, been compared to a photographic plate, and possibly this white blaze 

 may be due to the reflection of the sun's beams from the drops of water, and may be similar 

 to an attempt to photograph the roof of a conservatory with the sun shining on it. When 

 one considers the extremely local and partial distribution of the rainfall in desert and semi- 

 desert countries, there seems nothing improbable in the four forms of D. chrysippus being 

 evolved close together in a restricted area. The argument in support of local races that 

 alcippus alone occurs on the west coast of Africa (Sierra Leone, &c.) appears to me to be 

 of little value, the driest season in that district being in excess of the wettest round the 

 Gulf of Aden. If, however, it can be shown that alcippus alone occurs in the drier regions of 

 French Senegambia inland from Dakar and St. Louis, the argument will become much 

 stronger, for here I should expect the tetramorphic form to exist, the exact form appearing 

 to be dependent on local conditions. 



'With reference to the distribution of chrysippus the occurrence of the klugii [dorippus] 

 form near Trincomali is of interest, the Foul Point district being the driest in the island.' 



This letter was written some time ago, and before there was so large an amount of 

 material to work upon in connexion with this species. An interesting discussion on the 

 origin of the forms of D. chrysippus was communicated to the Entomological Society in 

 1902 by Professor Poulton, and the conclusions differ so much from those of Col. Yerbury 

 that it is desirable here to recapitulate them. Mr. and Mrs. S. L. Hinde captured a set of 

 fifteen specimens on May 6, 1900, almost on the sea level in the uniform damp heat of 

 Mombasa. Of these four were of the type form chrysippus and eleven of the dorippus 

 variety. All were taken in less than an hour in a spot of ground a few yards in extent, thus 

 affording a fair criterion of the proportionate numbers of the two forms. The second set 

 of about thirteen was taken at a height of about 5,400 feet at Machakos Road on the Uganda 

 railway on May 22, 1900, and consists of four of the type form, one alcippoides, and seven 

 dorippus and one albinus. These were also taken in a spot of ground a few yards in extent 

 in less than an hour. May 22 was at the end of a very dry wet-season in an exceptionally 

 dry year. The specimens show the effect of this, being on the average much smaller than 

 those bred from larvae, which fed on the more luxuriant food plant in Mombasa. An 

 examination of the two series favours the conclusion that the Machakos larvae were 

 partially starved, probably feeding on a parched food plant. It is further shown that 

 a comparison of the two series indicates very strongly that the various forms of the species 

 are not in any way due to environmental causes, but are inherent and hereditary. ' Dorippus 

 is considered to be due to drought, but there is a larger proportion of this form in the 

 series bred in the moist heat of Mombasa than in that reared at high and dry Machakos. 

 The great difference in conditions which is manifest in the different average size of the 

 two series was powerless to effect any change in the inherent hereditary tendency of the 

 individuals to become either klugii [dorippus) or its modification dorippus (white form), the 

 type form, or its modification alcippoides.' 



This comparison of forms from adjacent localities under different climatic conditions 



D 2 



