EVOLUTION 371 



bordered, and spotted above and below, is the wet-season 

 form of the insect known in the dry season as P. sesamm, 

 which has the wings above dark blue with many black 

 markings and sub-terminal rows of red spots, while below 

 they are uniformly dark and mottled so as to resemble dead 

 leaves ; this likeness is intensified by the markedly falcate 

 tips of the forewings, these being evenly rounded in octavia. 

 Hale Carpenter (1920), in his recent work on African insects, 

 confirms the opinion of Marshall and Poulton that the dry- 

 season forms are the more definitely protectively coloured 

 (" procryptic "), " and that this is due to the operation of 

 the dry season, when insects are so scarce that insectivorous 

 animals need to work harder to obtain food, and the risk to 

 any particular insect is proportionally greater." Though the 

 two forms Precis octavia and P. sesamus (Plate XIV, A) are 

 only seasonal varieties, the difference between them is much 

 more conspicuous than that which exists between thousands 

 of undoubtedly distinct species nearly allied to each other. 



Protective resemblance in general may therefore be 

 confidently regarded as adaptive, whether or not the 

 distinctive features causing the resemblance are of specific 

 importance. There is another set of facts connected with 

 the coloration of insects to which H. Bates (1862) was the 

 first to call attention. Certain groups like the wasps among 

 the Hymenoptera, and several sub-families of Nymphalid 

 butterflies — Danainae, Ithomiinae, Acraeinae, and Heliconi- 

 inae — are arrayed in a livery of startlingly contrasted colours 

 and are thus rendered very conspicuous. Such appearance 

 is now generally defined as warning (" aposematic ") colour 

 or pattern, and is frequently associated with the possession 

 of noxious quahties of some kind ; wasps have stings and 

 many of the butterflies of the groups just mentioned produce 

 poisonous or repellent secretions which render them 

 distasteful to lizards, birds, monkeys, and other creatures 

 that eat butterflies. The warning colour is believed to be 

 advantageous to such insects, because it ensures that they 

 are rapidly recognised by possible enemies and left alone. 

 Bates noticed that certain Brazilian butterflies, belonging to 



