SUBJECTS OF LATER LETTERS: 1867-71 231 



a few words of encouragement on Trimen's great 

 paper on Mimicry are contained in No. 13 ; the 

 geographical distribution of beetles in No. 19. 

 Of four brief letters, two contain invitations 

 (Nos. 13, 14), and two are concerned with diffi- 

 culties caused by ill-health (Nos. 17, 18, the 

 latter written by Mrs. Darwin). 



The first letter (No. 9) of the following series 

 introduces, and subsequent letters return to the 

 question of ocelli (ocellated spots or eye-spots) 

 on the wings of butterflies and moths. It is evi- 

 dent, from his reference to the male peacock and 

 inquiries as to ocelli restricted to male butterflies, 

 that Darwin was inclined to seek an interpreta- 

 tion based on the hypothesis of Sexual Selection. 1 

 It was not known until long after the date of 

 these letters that eye-spots together with certain 

 differences in shape 2 are in the vast majority 

 of cases characteristic of the butterfly broods of 

 the wet season. The existing interpretation of 

 them was first suggested by an observation made 

 by Professor Meldola and the present writer in 

 1887, when a lizard was seen to exhibit special 

 interest in an eye-spot on the wing of the English 

 ' Small Heath ' butterfly (Coenonympha pamphilus). 



the attraction of males by the female of Lasiocampa quercus, 252 ; 

 on Pnevmom, 288 ; on difference of colour in the sexes of beetles, 

 294; on moths brilliantly coloured beneath, 315 ; on mimicry in 

 butterflies, 325 [324] ; on Gynanisa /si's, and on the ocellated 

 spots of Lepidoptera, 428 ; on Cyllo Leda, 429.' Nearly all the 

 above subjects are referred to in letters 9-12, 15, 16. 



1 Compare pp. 104, 105, 113, 125, 127, 128, 133-5, 140-1. 



2 Figured by Darwin in Descent of Man, &c. (1874), 429. See 

 also 428 . 48. 



