MOEPHOLOGI OF THE LEPIDOPTERA. 147 



4 b. With a single aperture. 



2 Acherontia Atropos; Sphinx /irjusfri; 2 Ghcerocampa elpenor ; Smerinthus ocellatus ; Sm. 

 populi ; 2d Sm. mice ; 11 Enc/w/ia Jacobfca; ; 23 Arctia caja; 2 Cossus lit/nipcrda ; 1 Zvuzara 

 (Bsculi, St.; 1 Stauropus fayi, St.; 2 Notodonla dictteoides ; 1 N. dromcdarius, St.; 1 Leucmiiii 

 straminea, St.; Phakra bucephala ; 1 Thyalira { = Acronyctu) iridens, St.; 2 Gortyna flamigo, 

 St.; Mamestra brassicte ; lo M. persicarice ; 1 Achatia ( = Panolis) piniperda, St. ; 'y Diantluecia 

 irregularis; 1 MiseUia oxyacantha, St.; 1 Hadena ( = Agriopis) aprilina, St.; 3 Hadena glauca ; 

 13 H. chenopodd; CiiculUa verbasci ; 1 Bucephala {=Cucullia) umbratica, St.; 3 Gonoplcra 

 libatrix; 2 Selenia illustraria ; 18 Nyssia zonaria; 13 Biston hirtaria. 



The sti'uctures to which are due the marks distinctive of sex in chrysalids develop 

 towards the close of the caterpillar's life, and the cuticle that lines them is in continuity 

 with the cuticle of the future pupa. It is conceivable that the cuticle of the caterpillar 

 might in a given instance be sufficiently transparent to permit of their being seen ; it is 

 conceivable also, but not probable, that they might happen to develop at an earlier 

 stage of larval existence. Under no other conditions is it ^^ossible for them to afford aid 

 in deciding the question to what sex a living caterpillar belongs. It is easy enough to find 

 the answer to the question by dissection, as will apjoear later on (pp. 158-159 and note), 

 or by inspection in those few instances where the integument is of sufficient transparency' 

 to permit the testes and ovaries to be seen, and where at the same time there is a 

 difference of colour in those organs. I have examined, and in vain, for distinctive 

 external anatomical indications of sex, numbers of caterpillars of Pieris brassicce, 

 Vanessa lo, SpJiinx Ugustri, and Phalera bucephala, and have found none. It seems to 

 me, liowever, that the larger and longer caterpillars of Vanessa lo and the smaller 

 caterpillars of SpJiinx lUjustri. belong, as a rule, to the female sex. But I should not 

 like to be too positive without tables of measurements and weights. It is not only 

 possible but likely, however, that instances where size differentiates the sex of the 

 caterpillar may be found. Peculiarities of colouring are said to do so in some cases. 

 For example Weniger has stated, in the ' Entomologist ' (xx. 1887, pp. 87-89), that after 

 the second or third moult of the caterpillar of Altacus yama-mai, A. Vcrnyi, A. selene, 

 and A. cecropia, a coloured mark on the sternal region of the eighth abdominal somite 

 affords a certain test of sex. The mark in the female is a " black blotch " in the middle 

 of a yellowish tint, which in natural size is not larger than a large pin's head. The 

 male differs from the female in the fact that the black blotch has in its centre " a dark 

 green spot." In both sexes the distinctive mark disappears when they are killed and 

 " emptied." It is therefore probably due to a peculiarity in the larval cuticle. At least 

 there is no structure belonging to the reproductive organs in both sexes alike which has 

 the position assigned by Weniger. Professor Wcstwood points out, on p. 193 of his 

 ' Entomologist's Text-book,' 1838, that, according to de Geei-, brown caterpillars of the 

 yellow underwing, Triphcena pronuba, produce males, green caterpillars, females ; and I 

 gather from § 15, p. 20 of Ilerold's ' Entwickelungsgcschichte der Schmetterlinge ' 

 (Cassel & ^Marburg, 1815), that other instances are given in Kosel von Rosenhofs work 

 ' Der monatlich-herausgegel)enen Insecten-Belustiguugen,' published at Niiremberg in 

 1746-61, and illustrated with a large number of plates. This work I have seen, but 



