26 SOUTH-AFRICAN BUTTERFLIES. 



pointed. The abdomen of the male is more slender and compact, and 

 laterally compressed, while the thorax is relatively larger and thicker. 

 The more atrophied condition of the fore-tarsi in the male of three of 

 the five Families has been already treated of; in contrast to those of 

 the female, the fore-tarsi are especially noticeable for their imperfect 

 development in the male Erycinidce. This sex is also distinguished in 

 many genera by various badges on the wings, consisting of a small sac 

 (Danais), smooth patches of peculiarly arranged scales (JEuplcea), streaks 

 of short appressfed hairs along the nervures {Argynnis, some species of 

 Fapilio), or tufts of hair {Callidryas, Mycalesis)} The prehensile or 

 clasping organs at the extremity of the abdomen, although not very 

 apparent externally (excejDt in the Fa2nlionincc, where the outer valves 

 are conspicuous), are of remarkable development and complexity ; and 

 in all cases where the sexes are much alike in general appearance they 

 afford with a little pressure a certain means of determining the male.^ 

 Many of the Do,nain(B (genera Danais, Eiqjlcea, Amauris, Lycorca, Ituna) 

 possess, in the same region of the body, a pair of elongate organs 

 provided with a dense terminal fascicle of radiating hairs, which do 

 not appear to be often exserted, and which I have found only in the 

 males. Where there is much difference in colouring, it is almost 

 always the male that is the more brilliant in hue, most of the notable 

 exceptions being cases in which the female has been modified in pro- 

 tective resemblance to some species of another group. In the Danaincey 

 the Seliconinoi, a large number of the SatyrinoR and Nymphalince, most 

 Papilionincc and some Lycmnidm, the sexes are alike, or differ merely 

 in the female being somewhat duller than the male, and the same may 

 be said of most of the Hesperidm. Among the Acrceince, on the con- 

 trary, it is rare to find a species whose sexes are alike. It must be 

 noted, however, that in the cases of widest dissimilarity between the 

 sexes, it is almost invariably only the upper surface of the wings that 

 exhibits so great a contrast, the under surface presenting very slight, 

 if any, differences.^ The manifest reason of this is that, with scarcely 

 an exception, the colouring of the under side (exposed when the butterfly 



^ These are regarded as scent-organs by Fritz Muller and some other observers ; but I 

 have not seen proof of this view adduced, and am disposed, with Mr. Bates, to regard them 

 as " an outgrowth of the male organisation," without special function. 



^ These accessory male organs have been carefully investigated by Dr. P. Buchanan 

 White throughout the European Butterflies, and by Mr. P. H. Gosse in the genus Papilio 

 from all parts of the world. In the allied group of Trichoptera, Mr. R. M'Lachlan has 

 found in the homologoiis parts good classificatory characters ; but the astonishing differences 

 which they exhibit in closely-allied species of the genus Papilio (e.g., P. JDemoleus of Africa 

 and P. Erithonius of India, or the African P. Nireus and Bromius) render them apparently 

 of little value for systematic arrangement. See Trans. Linn. Soc, Zool., 2d Series, vol. i. 

 p. 357, and vol. ii. p. 265 (1S77 and 1S83). 



^ This is practically a character of the greatest assistance to the collector and student, 

 enabling him to identify the sexes of a species in numberless instances where, if both 

 surfaces of the wings had greatly differed, it would have been impossible to arrive at any 

 satisfactory conclusion. 



