74 Dr. F. A. Dixey on the Relation of 



forces, so to speak, in order to share the dangers of 

 experimental tasting. In the first kind it is obvious that 

 the onl}'- imitation must be by the unpi'otected of the 

 protected form ; there is no force tending in the converse 

 direction. But in the second kind it does not seem to 

 have been sufficiently noticed that, especially if the 

 numbers of the associated species are approximately 

 equal, there may fairly be expected to arise a kind of 

 give-and-take arrangement, in consequence of which two 

 or more inedible forms may hasten the assimilative 

 process by imitating each other. This is my reading of 

 the case before us. There are some independent grounds* 

 for tbiukiug that the mimicking Pierines in this par- 

 ticular group of instances are not, as has been generally 

 assumed, edible. It is therefore not unreasonable to 

 suppose that being distasteful, like the associated 

 Heliconii, and forming with them a company for mutual 

 protection, they have both taken from and bestowed on 

 them characteristic features of pattern — both sides, in 

 fact, having undergone what I some time since ventured 

 to call " reciprocal mimicry.^' I have elsewhere given more 

 detailed reasons in support of this view ; I reintroduce it 

 here for the sake of illustrating it from those Pierine marks 

 that have been specially under consideration. t 



* JE.f/., (1) the abundance of some of the mimetic species of the 

 same or of a closely allied genus, as Percute charops and Euterpe 

 ti'.iras (testified to by Messrs. Godmau and Salvin and by Fritz 

 j\I idler respectively) ; and (2) the fact that the nearest old-world 

 representatives of the same group, i.e., the members of the genus 

 Ih'Vias, have all the characteristics of insects protected by a 

 disagreeable taste or odour. 



f It may perhaps be objected that the resemblance between such 

 forms as are represented in Figs. 13, 14 is not sufficiently close 

 to warrant the supposition of mutual protection between them. 

 To this it may be replied, that (1) the colour of the diagonal band 

 of the forewing is probably in the living IlcUconius much nearer 

 to that of the Perente than appears in the figure, which was taken 

 from a specimen that bad been for some years in the Hope collec- 

 tion. It is well known that the reds in Hellconius and Acrcca are 

 especially apt to fade on keepiug. (2) The resemblance may be 

 enhanced by attitude, the figures having been di-awn without any 

 particular attention to this. (.">) The brightly coloured basal marks, 

 though occupying different relative positions in the two insects, 

 convey the same general idea of a gently-curving, slender, white or 

 yellow streak (belonging to the forewing in the Pereute and the 

 Iriidwing in the Heliconlus), beset nearits base with isolated spots 

 of vivid red, and traversing a black or dark-brown area of wing 

 close to the body. 



