156 PEOF. W. H. JACKSON ON THE 



seventeen pupae of undetermined sex were all male, an unlikely occurrence, and it is to 

 be regretted much that pressure of work prevented my examining closely the butterflies 

 to which they gave origin, there would be 140 males to 137 females, i. e. about equal 

 proportions of the two sexes *. Another more curious circumstance was noted. The 

 friends who kindly accompanied me and helped me to collect the specimens took their 

 supply from different colonies of caterpillars from those from which I took my own supply. 

 Our several finds were kept in different boxes, and it was found subsequently that the 

 individuals in the several boxes were principally, but not entirely, of one or of the other 

 sex. How far the colonies in which the caterpillars of V. Io feed may be derived from 

 different batches of ova 1 do not know. 



The second point relates to the coloration of the pupae. It is a well-known fact that 

 the pupae of the Peacock butterfly may be very dusky in colour or green and golden. 

 Every pupa that I saw actually at the moment of casting the larval skin possessed a 

 light green hue ; the only noticeable difference between individuals lay in the colour of 

 the coelomic fluid contained in the wings. The darker the tint the pupa was destined 

 to assume, the darker the green of that fluid. My pupae fell naturally into three classes. 



(1) A large number of caterpillars suspended themselves singly on the food-plants, the 

 common nettle. The part of the nettle, stalk, or leaf to which they were suspended was 

 for convenience removed and pinned to the underside of a box-lid which was then placed 

 over the box. They consequently hung in the dark. The pupae to which they gave 

 origin were yellow-green, their spines reddish, tipped with black. They had bright 

 golden specks at the bases of the abortive spines of the anterior somites and a few 

 pigmented streaks on the wings. Three caterpillars found by myself and my friend 

 Mr. Latter, suspended to the nettles in the nettle-bed whence we obtained our supplies 

 of specimens, pupated within a few hours of their capture and belonged to this class. 



(2) Many caterpillars suspended themselves in larger or smaller groups to the nettles, 

 to the sides of the boxes in which they were kept, or to the muslin covering the open 

 tops of the boxes. The pupae to which they gave origin differed inter se. Those at the 



* Bessels gives the following table of the numerical relations of males to females as he observed them (Zeit- 

 schrift fiir wiss. Zoologie, xvi. p. 500) : — 



Specie9. No. of males. No. of females. 



Pontia brassiere 70 19 



Sphinx euphorbire 100 35 



Gastropacha rubi 40 10 



„ potatoria 48 13 



Mamestra brassiere 80 30 



The names are as he gives them. I have a number of pupse of Pieris brassicce (winter brood) at the present time. 

 There are 2(i males lo 37 females. 



Mr. Doncaster, of the Strand, has lately permitted me to go over a number of pupre. The following notes as to the 

 relative proportions of males and females were taken: — Papilio Alachaon, J 21, $28; P. podalirius, d 37, 2 35; 

 Thais cerisyi, <$ 24, § 20; Sphinx Kgustri, tS 19, S 17; Smerinthus populi, d 15, J 20; Sm. tilice, tf 35, $ 29; 

 Chcerocampa elpenor, J 49, £ 50; Dianthcecia irregularis, tf 12, $ 5; Hadcna glauea, <S 8, J 3 ; II. chenopodii, 

 J 17, ? 13; Nyssia zonaria, tf 21, £ 22. 



