112 MIMICRY, AND OTHER PROTECTIVE 



though it is never perhaps quite equal to that of the 

 female. In insects the case is very different ; they 

 pair but once in their lives, and the prolonged existence 

 of the male is in most cases quite unnecessary for the 

 continuance of the race. The female, however, must 

 continue to exist long enough to deposit her eggs in a 

 place adapted for the development and growth of the 

 progeny. Hence there is a wide difference in the need 

 for protection in the two sexes ; and we should, there- 

 fore, expect to find that in some cases the special pro- 

 tection given to the female was in the male less in 

 amount or altogether wanting. The facts entirely con- 

 firm this expectation. In the spectre insects (Phas- 

 midae) it is often the females alone that so strikingly 

 resemble leaves, w r hile the males show only a rude 

 approximation. The male Diadema misippus is a very 

 handsome and conspicuous butterfly, without a sign of 

 protective or imitative colouring, while the female is 

 entirely unlike her partner, and is one of the most 

 wonderful cases of mimicry on record, resembling 

 most accurately the common Danais chrysippus, in 

 whose company it is often found. So in several species 

 of South American Pieris, the males are white and 

 black, of a similar type of colouring to our own 

 " cabbage " butterflies, while the females are rich 

 yellow and buff, spotted and marked so as exactly to 

 resemble species of HeliconidaB with which they asso- 

 ciate in the forest. In the Malay archipelago is found 

 a Diadema which had always been considered a male 

 insect on account of its glossy metallic-blue tints, 



