38 
coloration are at the bottom of little pits which have a black raised 
edge, and the insect consequently looks blackish-violet or black from 
the fact of the raised edges preventing the light reaching the eye. 
I know of no other beetle among our indigenous Coleoptera which 
shows this adaptation in such a marked degree, but in all our metallic 
species the nearer the insect is to the level of the eye, when looked at 
horizontally, the darker it becomes. There is another point in beetle 
coloration which to the evolutionist is a matter of great importance. 
I refer to the guide which colour affords as to the past history of a 
species or group. In no group amongst our indigenous Coleoptera can 
this be seen so well, or so markedly, as in our Staphylinidie, and this 
is the more valuable as it is one of the most natural and homogeneous 
groups that we have, and there are so many closely allied species, and 
so comparatively little difference between many of the groups, that 
gaps are very few, and we seem to have nearly the whole series which 
the group contains, and, as the llritish members number over 700, we 
have a good range of material to work on. Taking the species in the 
order in which they are classified in Sharp’s ( 'ataUxjne, we come 
very early in the list to O.rijioila altcntaiis, which is coloured as 
follows:—head black, thorax red, elytra black, base of abdomen red, a 
spot about the 5th and 6th segments black, and the extreme apex of 
abdomen red. This is not strictly true, the red being testaceous and 
the blacks not really black, but it shows what I want to draw attention 
to, namely, that tlie species is alternately coloured. Beginning with the 
black head, the beetle is alternately black, red, black, red, black, red. 
Now this as an isolated case would be renuu’kable in itself, but we 
could gather nothing from it except that it appeared somewhat highly 
specialised in its coloration. But this is by no means a solitary instance 
at all, and if we pass over 200 species, we come to two or three species 
in the genus (1 iiraphaout, and just past these to two of Jidlitocliara, 
namely lucida and Ix'lld, all of which have just this coloration, starting 
with the black head and running through the alternate colours, just in 
the same way as we saw in Oxipoda ulicniana, only Avitli the colours 
more defined. We then pass about another 75 species, and Ave come 
to l>(ilit(>l)iiis ((trirfijiillii.s, shoAving, perhaps, more markedly than in 
any other species, exactly the same arrangement of colour ; and then 
after a jump of about anothei' 110 species, this colour arrangement 
is again perfectly depicted in rxiptoliiuis <tltrr)iaits, and again about 50 
species further on is found in the genusV Vev/era.s. VouAvill no doubt check 
me here and say the elytra are blue in this group, but this is clearly a 
metallic structural colour not due to pigment, and that the elytra are 
really black but for this. We then pass another 60 species or so and 
(Kniponix nifiix. is reached, and the members can see that the identity of 
coloration betAveen this species and UnUlnhius atrirapillds is extra¬ 
ordinary. Finally, after another 100 species or so, Ave come to < hiialimn 
iopicniiii, the colours being not so Avell marked in this insect but 
sufficiently Avell, I think, to be included in this list. We see, then, that 
this peculiar scheme of coloration is continually cropping up at 
intervals right tlirougli the Avhole family, and that it alAvays begins 
Avith the head black. Are Ave to sup))ose that in each instance it lias 
arisen de iKim in each individual case as a ri'sponse to the external 
environment of the species, or are Ave to suppose it is an liereditary 
cluiracter banded doAvn from some common ancestor of the whole 
