ADAPTIVE COLORATION 229 
a species which is immune; while the male has had no such 
incentive 
so to speak—to become mimetic. Of course, there 
has been no conscious evolution of mimicry. 
Wallace’s fifth stipulation is important, but should read this 
way: “ The imitation, however minute, is but external and 
visible usually, and never extends to internal characters which 
do’ not affect the external appearance.” For, as Poulton 
points out, the alertness of a beetle which mimics a wasp, 
implies appropriate changes in the nervous and muscular sys- 
tems. In its intent, however, Wallace’s rule holds good, and 
by disregarding it some writers strain the theory of mimicry 
beyond reasonable limits. Some have said, for example, that 
the resemblance between caddis flies and moths is mimicry; 
when the fact is that this resemblance is not merely superficial 
but is deep-seated; the entire organization of Trichoptera 
shows that they are closely related to Lepidoptera. ‘This like- 
ness exprésses, then, not mimicry, but affinity and parallel 
development. The same objection applies to the assumed 
cases of mimicry within the limits of a single family, as be- 
tween two genera of Helicontidz or between the chrysomelid 
genera Lema and Diabrotica. The nearer two species are 
related to each other, the more probable 
it becomes that their similarity is due— 
not to mimicry—but to their common 
ancestry. 
On the other hand, the resemblance 
frequently occurs between species of such 
a A locustid, Myrme- 
Giterentworders that it. cannet be attrib=.  copfene | fal whee 
Mecdmionamimntyas wllliustrations Of tiiseare feria ane Shas 
natural length. From 
the mimicry of the honey bee by the Brunner von War 
TENWYL. 
Fic. 245. 
drone fly, and the many other instances in 
which stinging Hymenoptera are counterfeited by harmless 
flies or beetles. A locustid of the Soudan resembles an ant 
(Fig. 245), and the resemblance, by the way, is obtained in a 
most remarkable manner. Upon the stout body of this or- 
thopteron the abdomen of an ant is delineated in black, the rest 
