74 Dr. F. A. Dixey on the Relation of 
forces, so to speak, in order to share the dangers of 
experimental tasting. Jn the first kind it is obvious that 
the only imitation must be by the unprotected 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 beforeus. There are some independent grounds* 
for thinking 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. 
* E.g., (1) the abundance of some of the mimetic species of the 
same or of a closely allied genus, as Pereute charops and Euterpe 
tereas (testified to by Messrs. Godman and Salvin and by Fritz 
Miller respectively) ; and (2) the fact that the nearest old-world 
representatives of the same group, 7.e., the members of the genus 
Delias, have all the characteristics of insects protected by a 
disagreeable taste or odour. 
+ 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 Heliconius much nearer 
to that of the Perewte than appears in the figure, which was taken 
from a specimen that had been for some years in the Hope collec- 
tion. It is well known that the reds in Heliconius and Acrea are 
especially apt to fade on keeping. (2) ‘he resemblance may be 
enhanced by attitude, the figures having been drawn without any 
particular attention to this. (3) 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 
vellow streak (belonging to the forewing in the Pereute and the 
hindwing in the Helzconius), beset near its base with isolated spots 
of vivid red, and traversing a black or dark-brown area of wing 
close to the body. 
