PROTECTIVE COLORING IN CATERPILLARS/ 1145 



where wc know no reason for liolding such a view ; unil it is a little per- 

 plexing when we come to examine the large, naked and exposed caterpil- 

 lars of our Papilioninae, as of Laortias philenor, for instance, its hlack 

 body with projecting orange points set ott' vividly against the deep green 

 of the Aristolochia, or the gay bodies of Iphiclides and Papilio with their 

 transverse stripes of brilliant orange, green and black, — it is perplexing, 

 I say, to assert tiiat these are warning colors given to show the inedibility 

 of the caterpillar, possibly indicated also by the nauseous odor of the 

 osmateria, when in two other of our own genera, Jasoniades and Eu- 

 phoeadcs, with the same osmateria, wc iiavc protccfirc colors of no mean 

 importance. They may, however, be explained, at least in part ; for the 

 caterpillars of Laertias conceal themselves beneath the broad leaves of 

 Aristolochia so as not readily to be found but for the marks of their pres- 

 ence in their droppings ; and although one finds it difficult to look upon 

 the colors of Papilio polyxenes (the more striking of the other two men- 

 tioned) as in any sense protective, it is nevertheless true, as pointed out 

 by Poulton with regard to the similarly colored species, P. machaon of 

 Europe, that the protection afforded by the coloring of these insects is 

 "very real when the larva is on the plant, and can h.ardly be appreciated 

 at all when the two are apart." 



Poulton, therefore, distinguishes between general protective mimicry, 

 which, he says, is "such an appearance in an organism that the artistic 

 effect of its surroundings is sufficiently reproduced in it to prevent atten- 

 tion from being attracted when the one is seen in the midst of the other," 

 in fact simply a general harmony with its surroimdings ; and special pro- 

 tective mimicry, where protection is gained by the acquisition of a special 

 appearance. Slater has urged that gaily colored protected caterpillars 

 feed upon poisonous plants like Euphorbiaceae, Asclepiadaceae, Aristolo- 

 chia, etc. ; perhaps experimentation might show how much value there 

 is in this suggestion. 



One further point may be alluded to. It is well known that the cater- 

 pillars of many species of Lepidoptera are dichromatic in their later life, 

 some of the forms being Ijrown and others green. This has nothing what- 

 ever to do with sex or with food, and Poulton argues that in these cases 

 both colors are protective and that the species (though in no way the 

 dichromatic form) is advantaged, because when once discovered by an 

 enemy others of the same color would then be more easily found by this 

 enemy (a reason which would appeal to every field entomologist) ; so 

 that while one form might suffer, the species would be saved through the 

 escape of the other. Weismann believes that this change has been brought 

 about by natural selection, but Semper urges that selection "could not pos- 

 sibly effect any alteration in the pigment, but could only operate after such 

 a change had actually occurred." Closely allied to this is the well known 



'•M 



