116 Mr. G. A. K. Marshall on Diaposematism, with reference 



whose unpalatability is well established ; a view which is 

 still stroi)s[ly held by Mr. Trimeii. But this idea has been 

 traversed "by Prof. Poulton (Trans. Ent. Soc. 1902, p. 488), 

 who claims that the brown triangle is more characteristic 

 of, and more highly developed in, the Papilios than the 

 Planemas. He therefore assumes the Papilios to be 

 unpalatable, and suggests that it is their mimetic influ- 

 ence which has produced the brown triangle in Plancma; 

 and then subsequently tlie process has been reversed and 

 the Papilios have begun to mimic the Planemas by a 

 partial conversion of their stripes into spots, this being 

 described as " a late diaposematic response " {I. c. p. 489). 



Although this suggestion is supposed to indicate a case 

 of diaposematism, it is clear that the interpretation is not 

 really diaposematic, in the sense of suggesting a mutual 

 simultaneous approach. On the contrary, it evidently 

 comes under the heading of what I have termed (p. 103) 

 Alternating Resemblance, and involves tlie assumption of 

 a corresponding alternation in the individual numbers of 

 the respective species. 



The main point at issue is whether these Papilios are 

 really unpalatable, and of this there is no practical evi- 

 dence. It can only be settled by direct experiment, and 

 by careful observation of the insects in relation to their 

 environment. Personally, I have had experience of only a 

 single species of the group, namely, the extremely local 

 P. echerioidcs. The general behaviour of this insect ap- 

 pears to me to be entirely at variance with the supposition 

 that it is endowed with nauseous qualities, but its habits 

 suggest a possible interpretation of the facts under dis- 

 cussion. In South Africa F. cchcrioides is essentially a 

 forest insect ; it is not to be found in open woodlands, but 

 only among dense and lieavy timber, coursing irregularly 

 over the undergrowth beneath the trees. In such an 

 environment, lit up by splashes of broken sunlight, the 

 under-surface of the butterfly, as it settles on some low 

 shrub or among dead leaves on the ground, exhibits none 

 of the conspicuous warning characters which have been 

 attributed to it; on the contrary, its colours harmonise 

 most effectively with the surroundings in which it spends 

 most of its time and in which it habitually goes to rest. 



The habits of our only Flcmema, F. aganice, are very 

 different. For although it is also a lover of forests, it does 

 not fly beneath the trees, but is to be found sailing about 



