PROCEEDINCiS, 1916 25 



"All breeders of Lepidoptera naturally aim not only at olitaininsj 

 a high proportion of imagfines to the number of larvae, but also at 

 obtaining fine, richly coloured specimens. No doubt a large variety of 

 factors conduce to the production of such imagines, but one of the 

 greatest is. I I)elieve, quickness of development in the larval stage. Of 

 course the average life of larvae of different species varies enormously, 

 some taking years to come to maturity and others weeks onl}- ; so that 

 in speaking of quickness of development I only mean it to refer to the 

 usual length of life of the larva under consideration. Suppose for 

 example, we have a larva whose average life is 3 months; it will usually 

 produce a far finer imago if it comes to maturity in ten weeks, than if 

 it drags on for three and a half months. Other things being equal, the 

 cjuicker, within certain limits, larvae can be fed up without interferring 

 materially with their cycles, the larger will be the proportion to pupate 

 and the finer the resulting imagines. This I have found to be particularly 

 the case with larvae that feed up in the spring or early summer. 



"Xow if there is one thing that has more influence than another on 

 quickness of development, it is temperature. I do not mean that the 

 greater the heat the better will be the results. The temperature wants 

 to be consistent with that prevailing under the best conditions at the 

 time of year when the larvae naturally feed, and, above all, it should be 

 regular. I have frequently obtained quite remarkable results by feeding 

 up certain spring larvae in a temperature of 55 to 60 degrees kept up 

 regularly day and night in April and May. 



"This sort of treatment has one disadvantage, and that is, that 

 the imagines may appear two or three weeks before their proper time ; 

 but against this may be set very many advantages. The larvae seem 

 very much less liable to ailments ; the}- feed heartil}- and steadily, there 

 is practically no loss in changing skins or pupation, and the imagines are 

 large and handsome. I have found this use of a steady, fairly warm 

 temperature of the greatest help in rearing larvae hatched in the spring 

 from ova which were laid the previous stimmer or autumn, and have by 

 its means bred without any difficulty several species which pass the 

 winter as ova and are considered difficult, if not imjjossible. to get 

 through successfully in confinement. 



"Perhaps this effect of a regular temperature is one of the chief 

 reasons why some species vary so enormously in their abundance in 

 different years. If the temperature during the months the larvae are 

 feeding is unusually warm and steady for that period of the year, then 

 the next emergence of the species will be unusually abundant. It will 

 l)e noticed that I refer to the temperature being warm, not hot. Great 

 heat and drought have quite a contrary effect ; the larvae may feed up 

 very quickly, but the imagines are frequently small and stunted. This 

 may very likely be due to the fact that great heat dries up foliage and 

 makes it much less succulent, besides making it more difficult for the 



