172 A NATURALIST IN BORNEO 



they are present in the larva of the male, because 

 the male beetle has well-developed wings and wing- 

 covers. 



If, then, the adult male of the " Trilobite-Larva " is 

 provided with wings and wing-covers, then its larva 

 should possess imaginal rudiments, but a careful 

 microscopic examination of male larvae, ranging from 

 a comparatively small size to nearly the largest, has 

 failed to reveal the slightest trace of these organs. I 

 can therefore declare with some degree of confidence 

 that if an adult male of this larva be eventually found 

 differing in its external anatomy from the larva, then 

 it must be apterous. In spite of the abundance of 

 these larva?, in spite of the fact that they have been 

 known to collectors for many years, a male of this 

 description has never been found. I will venture to 

 prophesy, moreover, that it never will be found, but 

 that some day a "larva" with completely developed 

 internal generative organs communicating with the 

 exterior by ducts will be found, and such a " larva " 

 will be to all intents and purposes an adult. If this 

 is ever established we shall have a gradual transition 

 from species exhibiting complete metamorphosis to 

 species without any metamorphosis at all, as thus : 



Males and females undergoing complete metamorphosis 



Lycidce, etc. 



Males and females undergoing complete metamorphosis, but 

 female larviform Lampyris noctiluca. 



Male undergoing complete metamorphosis, female not meta- 

 morphosing, indistinguishable from larva Phengodes. 



? Luciola vespertina. 



Male and female undergoing no metamorphosis, both indis- 

 tinguishable from larvae " Trilobite- Larvae." 



