6 Dritte allgemeine Sitzung. 
the structural differences between them, as larva, pupa and imago, 
are strongly marked and indicate that the first sub-family belongs 
to one side of the great Nymphalid family and the second to the 
opposite side. This remarkable uniformity in the species of certain 
butterfly sub-families was first explained by Professor Meldola!) 
on the lines suggested by Dr. Fritz Miiller2) in 1879, viz. as an 
adaptation in order to reduce the amount of life sacrificed during 
the period when young and inexperienced insect-enemies are 
learning to distinguish between palatable and unpalatable (and 
perhaps unwholesome) food. If two species living intermingled 
and equally numerous are superficially exactly alike, and both 
nauseous, each will lose only half the number of individuals which 
would have been required in order to educate their enemies if they 
had been dissimilar. The sacrifice of life is also reduced by the 
strong general resemblance running through the species of each 
spec ially protected sub-family in one country. Such resemblance 
is by no means confined to the Khopalocera or the L epidoptera. 
It is found abundantly in all specially defended insect orders, princi- 
pally the Hymenoptera. If we look at the Australian Aculeata we 
notice a large group of species in which the orange ground colour 
is deeper and browner than in banded Aculeata generally, while 
the black zones are broader and fewer, being in fact usually 
reduced to two, one crossing the thorax, another the abdomen. 
This very characteristic appearance is to be found in Abispa, 
Eumenes, Alastor, Odynerus, Bembex and probably many 
other genera: it also occurs in mimetic Diptera (A silidae) and 
Longicorn Coleoptera. Here is a broad fact which receives an 
intelligible explanation by Natural Selection but by no other theory 
which has been suggested. We can well understand on the theory 
of Natural Selection w hy the members of specially detended groups 
should be far more alike than those of others, why they should 
resemble members of other such groups in the same region, why 
they should have conspicuous patterns and contrasted colours which 
in Lepidoptera tend to be the same upon the under as on the upper 
side of the wings, why their flight should be slow and flaunting, 
why they should be remarkably tenacious of life. Here are a number 
of important characters ; associated together and true of all such groups 
wherever they may occur in any part of the world. One theory alone 
explains all the numerous observations which are here condensed 
into a brief statement. It is by no means an assumption to main- 
tain that the groups in question are specially defended. This is 
admitted to be the case with the Hymenoptera and there is NOW 
a very large mass of experimental evidence in the Lepidoptera’). 
1) Ann. and Mag. Nat. Hist., Dec. 1882, p. 417. 
2) Kosmos, May 1879, p. 100; also Kosmos, V, 188t. 
3) See especially Frank Finn in Journ. Asiat. Soc. Bengal LNIV, pt. 11, 
1895, p. 344; LXV, pt. 11, 1896, p. 42; LX VI, pt. 22, 1897, p. 528; EXVIE 
pt. rr, 1897, p. 614. 
