Hudson. — N .Z. Insects illustrating Principle of Sexual Selection 435 



Erehia hutleri. In this respect these Satyrid butterflies show a striking 

 resemblance to many of their European relatives which have the females 

 lighter coloured than the males, but it is perhaps questionable whether 

 they can be called more brilliant. 



A much more striking instance of the direct operation of sexual selection 

 is afforded by our very interesting endemic little butterfly Chrysojihanus 

 holdenarum. In this species the male is of a most refulgent metallic purple, 

 the female being dull yellowish-brown with a row of blue spots around the 

 margin of each wing. This butterfly frequents stony places in river-beds, 

 where the males may constantly be observed displaying their brilliant 

 colours to the rather dingy-looking females, which generally appear to regard 

 their attentions in an unconcerned manner. Again, the male of our small 

 blue butterfly Lycaena labradus is, in common with the males of most 

 members of the genus throughout the world, a glistening blue, whilst the 

 female is drab-grey. 



Probably of greater interest than colour and wing-markings are the 

 special scent-producing organs which exist in certain male butterflies and 

 other Lepidoptera for the purpose of attracting the female, and of which 

 no trace can be found in that sex. Attention was first directed to these 

 organs by Fritz Mliller in 1877, who at the same time emphasized their 

 significance in connection with Darwin's theories, which were then steadily 

 gaining ground in the scientific world.* 



We have in New Zealand several good examples of special scent- 

 producing organs in male Lepidoptera. In the male of that strong-flying, 

 very wide-ranging butterfly Danaida plexippus there is a pocket-like struc- 

 ture situated on the hindwing, close to vein 2, which is absent in the female, 

 and is undoubtedly a scent-producing organ. Amongst moths the male of 

 our beautiful moss-green Noctuid Erana graminosa has a large fold in the 

 costal edge of the forewings which conceals ^.n extensible tuft of long pink 

 hairs. These hairs when stirred with a pin emit a most agreeable vanilla- 

 like perfume. A similar structure exists in the male of Rhapsa scotosialis. 

 The remarkable lobe in the much-contracted hindwing of the males of our 

 curious genus Tatosoma is a pocket-like organ, which in the absence of any 

 evidence to the contrary must also be regarded as scent-producing. The 

 male of Declana leptomera has large tufts of hair on the tibiae of the hind- 

 legs, similar tufts being found amongst some of ou'r smaller Lepidoptera, 

 and it is almost certain that these structures are for the purpose of emitting 

 perfumes agreeable to the female. 



A very great many observations have been made during recent years 

 by Drs. Dixey and Longstafi on the scent-organs and scents emitted by 

 tropical butterflies ; and the use of these special structures by the males, 

 for the purpose of attracting the females, has been placed practically 

 beyond a doubt. At the same time it must not be forgotten that certain 

 species of butterflies emit odours of a disagreeable nature which serve to 

 protect them from the attacks of birds and other enemies ; but in these 

 instances the scent-producing power is not confined to the male sex. 



In regard to our moths, a fair number exhibit considerable differences 

 in the colouring and markings of the sexes, but except in the case of 

 one or two day-flying species the males are not more brilliant or more 

 beautiful than the females. The sexes of Xanthorhoe semijissata and 



* For translation of Fritz Miiller's papers on this subject see appendix to 

 Dr. LongstafE's work, Butterfly -hunting in many Lands. * 



