226 A NATURALIST IN BORNEO 



first inclined to this idea after a study and arrange- 

 ment of the large collection of Phasmidce, or Stick- 

 Insects, in the Oxford University Museum. In South 

 America is found a sub-family of winged Phasmids 

 known as the Phasmince, and in Eastern Asia and the 

 Malay Archipelago occurs the sub-family of winged 

 species, the Necrosciince. The two sub-families are 

 widely separated geographically and genetically, yet 

 there exist numbers of species of Phasmince which re- 

 semble most closely in colouring and form other 

 species belonging to the Necrosciince. It is obvious 

 that these resemblances are neither due to mimicry 

 nor to genetic relationship, and they would be ex- 

 plained by nine out of ten entomologists as examples 

 of convergent development. But to confess that 

 certain species of a family exhibit convergence is 

 merely to state in other words that their evolution has 

 proceeded along very similar lines. It is exceedingly 

 common among the winged Phasmidce for the insect 

 when at rest to appear to be entirely green, and only 

 in flight to reveal the greater part of the hind-wings 

 as pink, the green colour being confined to a narrow 

 strip along the front. This arrangement of colours 

 crops up again and again in different genera belong- 

 ing to quite different sub-families, living in different 

 parts of the world. I regard this character as an ex- 

 pression of one of the lines of variation along which 

 the Phasmidce have moved ; we cannot suppose that 

 any other combination of colours, say yellow and blue, 

 would have brought down destruction, would have 

 been harmful to the species, and yet it is green and 

 pink, not yellow and blue, which form the common 

 widely distributed combination of colours ; and in my 



