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" No compound of this earthly ball 
Is like another, all in all." 





?' v- . .- 

" I do not enter so far into the province of the logicians as to take notice of the dif- 
ference there is between the analytic and synthetic methods of coming at truth, or 
proving it ; whether it is better to begin the disquisition from the subject, or from the 
attribute. If by the use of proper media anything can be showed to be, or not to be, 
I care not from what term the demonstration or argument takes its rise. Either way 
propositions may beget their like, and more truth be brought into the world." 
Religion of Nature Delineated, p. 45 (A.D. 1/22). 

^ HS 




Whose researches, in various parts of the world, have added 
so much to our knowledge of Zoological geography, 

this short Treatise 

is dedicated. 


To make a dry subject entertaining, is impossible ; 
but to render it, at any rate, readable, has been 
my endeavour in the following pages. How far I 
have succeeded in the experiment, it is not for me 
to decide. 

It having been suggested, by several of my 
friends, that it might be desirable to bring together 
into a small compass some of the evidence on 
Insect variation (with reference to external disturb- 
ing causes) which my researches in the Madeira 
Islands have supplied me with, I have been en- 
couraged to do so : and I have added numerous 
conclusions from other data also, which have from 
time to time fallen in my way, so as to confer 


on the volume a more practical interest, for the 
general naturalist . 

One of my main objects, however, has been to 
call attention to the fact, that the Annulosa have 
not been hitherto sufficiently considered, in the 
great questions arising out of the distribution of 
animals and plants ; hoping that, by so doing, 
some few of our British entomologists, who have 
not looked into this branch of their science, may 
be induced to enlist themselves in the cause of 
Insect geography. 

If such a result be brought about ; or if I 
be fortunate enough to open for discussion any 
of the topics which have been touched upon, and 
so lead to a more perfect solution of the problems 
which I have attempted to explain, I shall con- 
sider myself more than repaid. 

10 Hereford Street, Park Lane, London, 
May 10th, 1856. 



Introductory Remarks 


Fact of Variation 7 

As a matter of experience 8 

As probable from analogy 10 


Causes of Variation 19 

1. Climatal causes generally (whether dependent 

upon latitude or upon altitude) 23 

2. Temporary heat or cold, of an unusual degree ... 42 

3. Nature of the country, and of the soil 46 

4. Isolation; and exposure to a stormy atmosphere . 70 


Organs and Characters of Variation 95 


Geological Reflections Ill 


The Generic Theory 157 


Conclusion 181 

Page 90, for Pecteropus Maderemis read Pecteropv.s rostratu-s. 






A VERY small amount of information gained by the 
student in the field of Nature is sufficient to kindle the 
desire to increase it. The more we know, the more we 
are anxious to know ; though the less we seem to know. 
It is one of the distinctive privileges of the naturalist 
that he has to labour in a mine which is inexhaustible : 
the deeper he digs beneath the surface, the richer is the 
vein for excavation, and the more interesting are the 
facts which he brings successively to light. Dive he 
ever so deep, Truth, " at the bottom of the well," is 
assuredly present, under some form or other, to reward 
him still ; nor will she even for once elude his grasp, 
provided he be content to receive her as she is, instead 
of endeavouring to mould her to his preconceived ideas 


of what she ought to be. In these times of patient re- 
search, when the microscope is disclosing, day by day, 
fresh wonders to our view, and new lines of speculation 
are springing out, as it were spontaneously, from the 
regions of thought, it is remarkable that many of the 
commoner questions relating to the members of the 
external world around us have remained comparatively 
unsolved ; nor indeed have some of them ever been dis- 
cussed at all, except in a desultory manner and with 
insufficient data to reason from. Foremost amongst 
these, numerous problems affecting the distinction be- 
tween " varieties " and " species '' (as usually accepted) 
of the animal kingdom stand pre-eminent, especially 
in the Annulose Orders, in which those distinctions are 
less easy, a priori, to pronounce upon. 

The descriptive naturalist, whose primary object it is 
to register what he sees (apart from the obscurer phe- 
nomena which come within the province of the more 
philosophical inquirer), can have scarcely failed to re- 
mark the variation to which certain insects are at times 
liable from the external agencies to which they have 
been exposed : and yet, in spite of this, it is but too true 
that even physiologists have frequently shunned the in- 
vestigation of the circumstances on which such varia- 
tions do manifestly in a great measure depend, as though 
they were in no degree accountable for the changes in 
question, and did not indeed so much as exist except in 
theory. In the following pages I purpose, inter alia, to 
throw out a few general hints ; first, on the fact of aber- 

ration, as a mere matter of experience ; and, secondly, 
on some of the causes to which the physiologist would, 
in many instances, endeavour to refer it. 

The former of these considerations (namely, the fact 
of specific instability as ordinarily noticed) nobody will 
be inclined to dispute : and yet it is abundantly evident 
that it cannot be taken into account, at any rate satis- 
factorily, without involving the latter also, it being 
scarcely possible to attach the proper value to an effect 
without first investigating its cause. The importance 
of assigning its legitimate weight (and that only) to a 
variety, is perhaps the most difficult task which the 
natural historian has to accomplish ; since on it depends 
the acknowledgment of the specific identity of one 
object with another, whilst, to draw the line of separa- 
tion between varieties and species is indeed a Gordian 
knot which generations have proved inadequate to untie. 
Now it is not the object of this publication to attempt 
to throw positively new light upon a subject which has 
ever been one of the main stumbling-blocks in the lower 
sciences, and which is perhaps destined to be so to the 
end ; still less would I wish to imply that the causes of 
variation are altogether overlooked in these days of 
accurate inquiry, when thousands are accumulating 
data, in all parts of Europe, destined to be wielded by 
the master's hand whensoever the harvest-time shall 
have arrived : but I do, nevertheless, believe that there 
exists a growing tendency, especially in some portions of 
the Continent, to regard every difference (if at all perma- 



iient) as a specific one ; and hence I gather the informa- 
tion that a reviewal of our first principles is occasionally 
necessary, if we would not restrict (however gradual and 
imperceptibly) that legitimate freedom which Nature 
has had chalked out for her to sport in, or strive to im- 
pose laws of limitation in one department which we do 
not admit to be coercive in another. 

Perhaps, however, before entering on the subject- 
matter of this treatise, my definition of the terms 
" species '' and " variety," so far at least as such is 
practicable, will be expected of me. I may state, there- 
fore, that I consider the former to involve that ideal re- 
lationship amongst all its members w r hich the descent 
from a common parent can alone convey : whilst the 
latter should be restricted, unless I am mistaken, to 
those various aberrations from their peculiar type which 
are sufficiently constant and isolated in their general 
character to appear, at first sight, to be distinct from it. 

The first of these enunciations, it will be perceived, 
takes for granted the acceptance of a dogma which I 
am fully aware is open to much controversy and doubt, 
namely, that of ' ' specific centres of creation." With- 
out, therefore, examining the evidences of that theory 
which would be out of place in these pages (and which has 
been so ably done already by the late Professor Edward 
Forbes), I would merely suggest that t\ie admission of it 
is almost necessary, in order to convey to our minds any 
definite notion of the word "species "at all : and that, 
lience, whilst I would not \vish to reject the hypothesis 

as involving an absurdity (which I believe to be the 
exact opposite of the truth), I would, in the present 
state of our knowledge, desire rather to regard it as a 
postulate, assumed to illustrate the doctrine of species, 
than as a problem capable of satisfactory demonstration. 
The second of the above definitions may likewise 
require briefly commenting upon ; for I have frequently 
heard it asserted that everything is to be regarded as a 
' ' variety ' which has wandered in the smallest degree 
from its normal state. Now this I contend is essentially 
an error ; for a ' ' variety," to be technically such, must 
have in it the primd-facie elements of stability, and to 
an extent moreover that, without the intermediate links 
(which, although rarer than the variety itself, must 
nevertheless exist] to connect it with its parent stock, 
its condition is such that it might be registered as speci- 
fically distinct therefrom. Thus, to take an example for 
illustration, there are many darkly coloured insects 
which, as every entomologist knows, vary, by slow and 
regular gradations, into a pallid hue, sometimes into 
almost white. It also most frequently happens, in such 
instances, that the extreme aberration is of more common 
occurrence than the intermediate ones. Here then is a 
case in point : there is but a single variety involved, 
namely a pale one, the gradually progressive shades 
which imperceptibly affiliate it with its type not being 
regarded in themselves as " varieties ' at all. If this 
indeed were not so, then would our position be far from 
pleasant, since we should be compelled to record, as a 


variety, every separate degree of colour which could 
possibly be found between the outer limits, seeing that 
(increasing, as they did, in an even ratio) no one could 
be tabulated in preference to another. 

This however is an example in which the rate of altera- 
tion (so far as colour is concerned) is equal and one 
therefore in which the extreme end of the series can be 
alone singled out as the aberration to be specially noticed. 
It sometimes occurs that, between the two extremes^ 
there are several nuclei, or centres of radiation, to which 
the name of varieties may be legitimately applied, in- 
asmuch as they may possess a series of characters which 
do not, all, in combination, progress evenly ; and which 
consequently stand out as it were, to a certain extent 
isolated, from the remainder. 

As a corollary arising out of these remarks, it would 
seem to follow that even small differences should be re- 
garded as specific ones so long as the intermediate links 
have not been detected which may enable us to refer 
them to their nearest types. In a general sense, I 
believe that it would be proper to do so : nevertheless 
there are instances, the results, for example, of isolation, 
in which abrupt modifications may be a priori looked 
for ; and in which our judgment must be regulated by 
our knowledge of the local circumstances which may be 
reasonably presumed to have had some influence in pro- 
ducing them. The consideration of these, however, and 
other kindred questions, must be deferred to a subse- 
quent chapter of this work. 



IT is scarcely possible to survey the members of the 
external world around us without being struck with the 
instability with which everything is impressed. The 
very shadows, as they pass, leave a moral lesson behind 
them on the mountain-slope,, which the student of 
Nature would do well to contemplate. Whatever be 
our preconceived ideas of the " immutability of the uni- 
verse," from first to last the same truth is re-echoed to 
our mind, that here all is change. Organic and in- 
organic matter are alike subjected to renovation and 
decay ; and, dependent on that general law, variability 
within specific limits would seem to be an almost neces- 
sary consequence. In the animal and vegetable king- 
doms, this principle of fluctuation is peculiarly apparent ; 
and not more surely do the winds of heaven ruffle the 
forests over which they rage, than does the ebb and flow 
which is perpetually going on amongst created things 
mar their boasted constancy. 

The fact of aberration, to which we would briefly 
allude in this chapter, requires but little comment ; it is 
patent a priori. As a matter of experience, every ob- 
server who has spent a week in the field of Nature 

knows it to exist. However difficult it may be, in some 


instances, to distinguish aright betwean. species and 
varieties, as rigidly defined, there is an instinct within 
us which often recognizes the latter, even at first sight, 
as unmistakeably such : and in these cases, a well-edu- 
cated eye, although of course occasionally deceived, will 
not often be found to err. 

In the vegetable world this proneness to variation is 
self-evident; and botanists innumerable, who have in- 
vestigated the causes on which the modifications of cer- 
tain plants have been presumed to depend, have not 
been behindhand in acknowledging it. Soil, climate, 
altitude, and a combination of other circumstances and 
conditions, have been successively taken into account, 
and to each an amount of disturbing influence (more or 
less, as the case may be) has been conceded. "The 
more powerful agents," writes Professor Heiifrey, ' ( en- 
force their general laws, but every little local action 
asserts its qualifying voice; and we see that all these 
irregularities and uncertainties (as we in our ignorance 
call them, and complain of) are necessary and important 
parts of a great whole, are but isolated features of a 
comprehensive plan, in accordance with which all work 
in concert to bring about that change absolutely indis- 
pensable to the existence of animal and vegetable life 
upon the earth's surface, and that variety of conditions- 
by which is ensured a fitting abode for each kind of its 
multifarious and diversified inhabitants." 

Whilst exploring the barren moor, or bleak upland 


heights, the botanist would as assuredly look for a 
change in the outward configuration of certain species, 
which colonize equally the rich meadows and teeming 
ravines, as a geographical difference is a priori antici- 
pated between the hard, sturdy mountaineer and the 
more enervated denizen of the plain. A daisy, gathered 
on the cultivated lawn, has usually attained a greater 
degree of perfection and luxuriance than its companion 
from the sterile heath; and the bramble which chokes 
up the ditches of the sheltered hedgerow, wears a very 
different aspect from its stunted brother of the hills. 

Nor is this dependency on external circumstances less 
apparent in the animal kingdom also, the domesticated 
races of which every agriculturist is aware are capable 
of modification, artificially, to an almost unlimited ex- 
tent ; and which exhibit, when even in a state of nature, 
nearly as great a variety, from purely natural causes, as 
they have been proved to do when subjected to the laws 
and routine of agrarian science. Take the sheep, for 
example, of Dartmoor or Wales, and compare them with 
those from the wolds of Lincolnshire and the downs of 
Kent ; or contrast the Hereford oxen with those of the 
midland counties, or of the Caledonian breed, still extant 
in Cadzow Forest, and it will require but little argument 
to convince us how important is the operation of local 
circumstances in regulating the outward contour of these 
higher creatures. If therefore this general obedience to 
influences from without be self-evident in the vegetable 
world, and equally traceable amongst the Mammalia, 

B 5 


why, we may ask, are the lower members of the animal 
creation to be denied analogous effects from the same 
causes ? 

We are often told that the Annulosa present so many 
anomalies in their organization, that we cannot apply 
the argument of analogy, when reasoning on their struc- 
ture and attributes ; and that we must consequently be 
content to leave it an open question, as to whether or 
not they possess anything in common with the Verte- 
brata, or can be presumed to be acted upon, by external 
agencies, in at all a similar manner. Now, whilst there 
is clearly some truth in this assertion (especially as 
regards the senses of insects, which must ever remain a 
subject of obscurity), I contend that to accept it in all 
its fullness would be in the highest degree unphiloso- 
phical; whilst, to endorse it to the extent which even 
its partial advocates do insist upon, would at once 
involve us in a host of difficulties (affecting other de- 
partments of natural science), the very existence of 
which they have themselves tacitly repudiated. 

" Creation/ 7 says one of our most intelligent writers 
of modern times, " is full of analogies, pointing to one 
general originator, and linking all sentient things into 
one great family of related fellow-creatures : ' : -and 
there is an amount of sagacity in the remark which it 
would be wise for us to digest. Throughout the whole 
of animated nature, it is impossible not to perceive that 
certain circumstances do, in the main, produce certain 
results. They may often fail to produce them, and the 


results themselves may frequently be modified (or, ap- 
parently, even reversed), from counter influences of 
divers kinds. This touches not, however, the existence 
of the law; and the effect is not the less specifically 
dependent on its own peculiar cause, because those 
"counter influences' prevail, and because different 
effects may chance, therefore, to be occasionally brought 
about by causes which may possibly seem to be identical. 
We should, rather, bear in mind that the agents which 
operate in moulding the outward contour of organic 
beings are various, and capable inter se of permutations 
innumerable; so that it is only on a broad scale that 
parallel results can be looked for in creatures severally 
exposed to the action of elements, which are liable to be 
differently compounded from what may primd facie 
appear to be the case : and that, consequently, where 
opposite phenomena are displayed under circumstances 
seemingly coincident, our first object should be (not to 
regard the phenomena as indicative, that no constant 
result can be anticipated from causes which are similar, 
but), to inquire whether the circumstances in question 
are really coincident or not, seeing that some counter- 
acting stimulus may have been, here or there, unex- 
pectedly at work, which shall enable us, so soon as it is 
detected, to account for the discrepancy. 

It is by this process alone that we can hope to make 
real use of analogy, without abusing it : for whilst there 
is danger, on the one hand, of needlessly rejecting the 
argument which it suggests to us, through opposite 


effects being observed (amongst the members of the 
organic world) from conditions which we assume to be 
co-ordinate, but which in fact are not so; we may, on 
the other, run a similar risk (and thus fail to discern a 
corresponding modus operandi in the maturation of like 
results), from a mere a priori belief that the lower 
animals cannot be acted upon, by external influences, in 
a manner at all equivalent to that which is self-evident 
in the higher ones. 

" To make a perfect observer in any department of 
science," writes Sir John Herschel, "an extensive ac- 
quaintance is requisite, not only with the particular 
science to which his observations relate, but with every 
branch of knowledge which may enable him to appre- 
ciate and neutralize the effect of extraneous disturbing 
causes. Thus furnished, he will be prepared to seize on 
any of those minute indications which often connect 
phenomena which seem quite remote from each other. 
He will have his eyes as it were opened, that they may 
be struck at once with any occurrence which, according 
to received theories, ought not to happen ; for these are 
the facts which serve as clews to new discoveries *." 

There can be no doubt that amongst a large proportion 
of our naturalists, differences, as such, are too exclusively 
studied. Essential as their investigation is (for we could 
not progress a step without some presumptive notion as 
to the specific identity, or not, of the objects about which 

* Preliminary Discourse on the Study of Natural Philosophy 
(London, 1830), p. 132. 


we have to treat), we should not forget that there are 
other questions, likewise, which ought to occupy our 
attention in, at any rate, an almost equal degree, as 
being of eminent significance in guiding us to a correct 
interpretation of the phenomena with which we have to 
deal. Such are, more especially, similitudes and ana- 
logies, in their widest sense, --which are too often 
neglected, even by those who admit the necessity of 
recognizing them where they may be shown to exist. 
Lord Bacon, in referring to a similar tendency amongst 
a certain section of the naturalists of his day, remarks 
(though perhaps his love of analogies may have led him 
to somewhat overrate their importance) : " Up to this 
time the industry of men has been great, and very curi- 
ous in marking the variety of things, and explaining the 
accurate differences of animals, herbs, and fossils, the 
chief part of which are the mere sport of Nature, rather 
than serious and of use toward the sciences. Such 
things tend to our enjoyment, and sometimes to even 
practical use; but little or nothing towards an insight 
into Nature. And so our labour is to be turned to in- 
quiry into, and notice of, similitudes and analogies, both 
in the whole and in the parts of things : for these are 
they which unite Nature, and begin to establish 


* " Magna enim hucusque atque adeo curiosa fuit hominum in- 
dustria, in notanda rerum varietate, atque explicandis accuratis 
animaliuin, herbarum, et fossilium differentiis ; quarum plerseque 
magis sunt lusus nature, quam seriae alicujus utilitatis versus 


I believe that, if analogies were more carefully studied 
in the lower departments of the animal kingdom, we 
should be less inclined to deny some sort of uniformity 
to the action of elements and conditions which, by a 
law of Nature, must at times operate equally upon the 
various and dissimilar members of the organic creation. 
Amongst the Insecta, where the individuals exist in such 
multitudes that accuracy in generalizations concerning 
them, becomes, as it were, peculiarly within our reach, 
this doctrine cannot be too rigidly insisted upon ; and it 
is not difficult to foresee that, should the principle of 
external disturbing influences ever be admitted by ento- 
mologists to the extent which it has been accepted by 
the students of the Vertebrata, our so-called ' ' species ' 
will have to submit to a process of elimination and 
inquiry, which at present would be well nigh incre- 
dible. The time for such a step is yet far off : perhaps 
indeed, considering the innovations of nomenclature 
which it would necessitate, it will never arrive at all ; 
yet the fact remains the same, that, if analogy with 
creatures of a more perfect development be not altogether 
disallowed us, during our researches into the insect 
tribes, or if similar causes may be presumed to have 
somewhat similar effects in opposite sections of the 

scientias. Faciunt certe hujusmodi res ad delectationem, atque 
etiam quandoque ad praxin; verum ad introspiciendam naturam 
parum aut nihil. Itaque convertenda plane est opera ad inquiren- 
das et notandas rerum similitudines et analoga, tarn in integralibus, 
quam partibus : ilia? enim sunt, quae naturam uniunt, et constituere 
scientias inciphmt." Novum Organum, lib. ii. 27. 


animate world, an enlargement of our prescribed limits, 
for specific variation, ought in reality to follow (sooner 
or later) as an inevitable consequence. 

In whichever light, therefore, insect aberration is 
viewed by us, whether as a matter of experience (which, 
being self-evident, will satisfy the practical observer), or 
as probable from analogy (which will hardly be denied, 
at any rate to a certain extent, by even the most theo- 
retical), we affirm that it does, ipso facto, exist. 
" There is no similitude in Nature that owneth not also 
to a difference-," let this be constantly borne in mind, 
for it is a truism almost beyond controversy, and one 
which, to a reflective mind, will scarcely admit of a 

It will be perceived, from the above remarks, that I 
draw a distinction between insects which simply vary 
(that is to say, which aberr from their normal state), 
and those which afford (in the sense as enunciated in 
the last chapter) one or more actual " varieties," 
technically so called : and it will be further gathered, 
that, whilst I regard the former as universally to be met 
with, the latter are, on the contrary, of only occasional 
occurrence. That positive and well-defined varieties, or 
races, should be confined to certain species, is not re- 
markable ; but that every individual insect should differ, 
however slightly, from its nearest relation and ally, may 
perhaps require some few words of explanation, even to 
a naturalist. It is not essential however to our present 
subject (which is merely a plea for specific variation 


generally, as commonly understood) that any such 
dogma should be propounded ; nevertheless, since all 
analogy teaches us to anticipate it, and observation tends 
more and more, as our knowledge advances, to corrobo- 
rate the fact, I shall be pardoned for venturing a passing 
thought upon a question even thus difficult of demon- 

Perhaps we are too prone to regard those specific 
characters, which are so subtle that they cannot be 
grasped by our clumsy faculties except in their broadest 
and plainest features, as incapable of fluctuation. Yet a 
practised eye can detect discrepancies innumerable in 
specimens which appear absolutely alike to one that is 
uneducated ; whilst a third person, better qualified still, 
will trace out other and more delicate distinctions, with 
even greater precision. And thus it is that we rise, step 
by step, even amongst the humbler representatives of 
the animal kingdom, to the comprehension of that great 
truth which is so conspicuous in the nobler ones, and 
which we have already summoned to our aid, that " there 
is no similitude in Nature which owneth not also to a 
difference." Let us not forget that the sphere of our 
senses is limited; and that, although tuition will do 
much to enlarge their capacity for perception, we are at 
the best but a dim- sighted race : hence, we should be 
careful to avoid conclusions which are not warranted by 
analogy, and which our understanding, as it becomes 
gradually brighter, no less assuredly condemns. True 
it is, that we may not be able, as in the higher animals, 


to appreciate the differences between individuals without 
a rigid inspection, and that sometimes we may fail to do 
so even when the objects are critically examined ; yet 
the fact that new peculiarities do unquestionably open 
out upon us, as we become more and more trained for 
the recognition of them, ought to warn us that others 
may exist likewise, despite our primd-facie conclusions ; 
whilst analogy with what we know to be the case in 
other departments of the organic world should suggest, 
unless indeed there is presumptive evidence to the con- 
trary, that they in all probability do. 

The Alpine range, when seen from afar, appears a 
monotonous mass of a dull uniform hue ; and nothing, 
of all the wondrous details which it includes, can be 
distinguished, except perchance the outline of its jagged 
peaks projected in faint relief against the distant sky. 
One by one, however, as we approach it, inequalities 
present themselves; the surface which lately seemed so 
uniform and grey that it could be compared only to a 
cloud, is found to be cleft by ravines ; and valleys, in all 
their magnificence and breadth, expand slowly to our 
view. Yet, marvellous as is the change, this is not all : 
wood and water, without which the landscape would be 
barren, are in turn revealed ; whilst the play of light 
and shade upon the mountain-slopes proclaims at length 
that the picture is well nigh complete. Still more to be 
disclosed does in reality remain ; and we must advance 
nearer yet if we would either fully realise the whole, or 
enter into the surprising minutiae of each of its com- 


ponent parts. And so it is with the objects which we 
have been just discussing. When contemplated in a 
mass, and by an uneducated eye, hosts of them may 
appear to be identical ; but as our vision becomes clearer 
and more acute, differences, formerly inappreciable, are 
gradually made manifest, until at last we can detect 
modifications innumerable, throughout the entire length 
of the living panorama ; and are enabled to endorse the 
belief (repugnant a priori though it be), that individual 
variations, even to the extent which I have ventured to 
suggest, are not incompatible with specific similitudes. 





IT is not impossible/' says a writer of the last century, 
that such laws of Nature, and such a series of causes 
and effects, may have been originally designed, that not 
only general provisions may have been made for the 
several species of beings, but that even particular cases 
(at least many of them) may have been provided for 
without innovations in the course of Nature"*." And 
let us not suppose that this is a mere wanton specula- 
tion, unsiipported by evidence (if not actually circum- 
stantial, at least) strongly presumptive ; since the further 
we penetrate into the ramifications of the organic world, 
the less are we inclined to ignore the operation of those 
various modifying influences which our understanding 
tells us do everywhere exist. 

To investigate the causes of things, and to endeavour 
to trace out by slow, inductive processes those second- 
ary agents, by the assistance of which a large propor- 
tion of the phenomena around us are gradually matured, 
is no insignificant task; yet how much animadversion 
from without have the students in such fields of research 
frequently to endure ! A fact many times repeated, and 
which comes within our daily experience, is too often 

* Religion of Nature Delineated, p. 103. 


looked upon as a matter of course, and as therefore 
beneath the notice of an intelligent mind : yet the man 
who regards truth as valuable, for its own sake, under 
whatever aspect it may come, and who can rise to the 
appreciation of results, whether they be of rare or con- 
stant occurrence, will have learnt to pronounce nothing 
as unimportant which may supply a single link in that 
chain of knowledge which would be broken and im- 
perfect without it. A spirit of inquiry, however, is 
becoming, year by year, more evident ; and we may con- 
fidently anticipate the period when such reproaches will 
have for ever died away. Natural history, in all its 
branches, will then advance more rapidly than hereto- 
fore, and each separate labourer, in his own peculiar 
province, will breathe a more genial atmosphere ; whilst 
observation and reason, mutually dependent on each 
other, will work in concert more effectually. " Reason 
without observation" writes the author above quoted, 
" wants matter to act upon : and observations are neither 
to be justly made by ourselves, nor to be rightly chosen 
out of those collected by others, without the assistance 
of reason. Both together may support opinion and 
practice, in the absence of knowledge and certainty." 

In the last chapter we offered a few passing remarks 
on insect- aberration generally, whether regarded as a 
universal fact (which, however, even supposing such to 
be true, it is not the object of the present treatise to 
substantiate), or as an occasional one, that is to say, 
as existing at all times to that extent (as an hereditary 


principle), that it is liable to manifest itself, or not, 
according as external agencies may favour or oppose its 
occurrence. In the latter case, which alone I propose 
to consider, this inherent tendency may be displayed, 
either through the expression of " varieties ): well de- 
nned, or by a mere proneness to wander, irregularly and 
at large, from an assumed diagnostic type. In the fol- 
lowing pages, the former of these resultant conditions 
(namely, that in which " varieties," technically so called, 
though more or less isolated in their character, are appa- 
rent) will be especially discussed; since my principal 
desire is, to point out the influence of local disturbing 
causes in regulating, to a greater or less extent, though 
of course within certain specific limits, the outward 
contour of the insect tribes, and it requires no argu- 
ment to prove that, where those local elements (whatso- 
ever they may be) prevail, the same effects will, for the 
most part (in the same species), be produced ; and that, 
therefore, modifications which are characteristic of coun- 
tries and regions far removed from each other have an 
a priori claim for stability, above those which circum- 
stances less important than geographical ones, and 
which are consequently more fluctuating in their com- 
binations, may from time to time (as it were, accident- 
ally) shape out. Having then examined our premises, 
and prepared ourselves, with an unbiassed mind, for the 
reception of phenomena which should be constant (and 
in some instances, also, conspicuous) in proportion as 
the conditions which unite in bringing them about are 


significant ; let us advert to a few of the more prominent 
cases in which our instinct would seem to warrant the 
belief that aberrations are to be usually anticipated. 
And since it will hardly be denied that, like the repre- 
sentatives of other departments of the animate world, 
insects may, in their outward configuration and deve- 
lopment, be in some measure under the control of the 
external influences to which they are immediately ex- 
posed, we will take a rapid glance at a few of the circum- 
stances and conditions which are known to have more or 
less of a qualifying effect on the members of large and 
opposite sections of the organic creation ; and then see 
how far we are enabled, by means of facts, to trace out 
results for the Insecta, corresponding to those which are 
admitted to obtain in the other groups. And, since the 
existence of analogous results infers, to a certain extent, 
the similarity of the agents which have brought them 
about, our " causes of variation ' (provided the effects 
can be shown) may be in reality almost demonstrated. 

Amongst the numerous influences and conditions, in 
obedience to which the members of a large proportion 
of the animate world would appear, at times, in their 
outward aspect to be modified or fashioned, the following 
may be selected as perhaps of primary importance : 

1. Climatal causes generally (whether dependent on 
latitude or upon altitude). 

2. Temporary heat or cold, of an unusual degree. 

3. Nature of the country and of the soil. 

4. Isolation, and exposure to a stormy atmosphere. 


I. Climatal causes generally, whether dependent on 

latitude or altitude. 

Perhaps, judging superficially, climatal causes gene- 
rally would appear to have more effect on insect deve- 
lopment than any with which we are acquainted ; yet, 
powerful as they unquestionably are, experience teaches 
us that such is not the case. In combination with other 
modifying principles, hereafter to be noticed, they may 
be (and probably are) exceedingly important ; yet, when 
taken singly and alone, we have no evidence to show 
that their consequences are of such primary significance 
as might be anticipated. Mr. Darwin, in describing the 
fauna (which includes many mundane forms) of the 
Galapagos Archipelago, situated immediately under the 
equator, remarks : " The birds, plants, and insects have 
a desert character, and are not more brilliantly coloured 
than those from Patagonia ; we may therefore conclude, 
that the usual gaudy colouring of the intertropical pro- 
ductions is not related either to the heat or light of 
those zones, but to some other cause, perhaps to the 
conditions of existence being generally favourable to 

Although it is true, in a broad sense, that the nearer 
we approach the Line the grander and more gorgeous 
are the animate beings which tenant the surface of our 
earth, there are at the same time so many exceptions to 
this law, that it cannot be regarded as by any means 
* Journal of Researches (London, 1852), p. 381. 


universal; and whatever, therefore, be our ideas on a 
subject which might perchance seem to be self-evident, 
we are compelled to infer that climatal causes, of them- 
selves, will not suffice to account for the numerous cases 
of aberration which we so constantly meet with in re- 
presentatives of the same species exposed, through a 
long series of centuries, to opposite conditions of atmo- 
sphere. We need not, however, go so far as the Gala- 
pagos to convince ourselves of this. The Madeiran 
Group is placed between the 32nd and 33rd parallels of 
north latitude, off the coast of Africa, and contains a 
Coleopterous fauna (as hitherto ascertained) of about 
550 species. Now 240 of these, at least, occur also in 
Europe (many of them even in our own country) ; 
hence, if a more southern climate may be presumed, 
of itself, to exercise any very decided modifying influ- 
ence on insect development, we have an amount of ma- 
terial for comparison which should surely afford us some 
definite and tangible result. My own experience in 
those islands would tend to prove, that, amongst the 
many aberrations from their northern types which are 
there everywhere displayed, comparatively few of them 
can be referred for explanation to causes strictly climatal. 
I do not say that none can be thus accounted for ; yet 
I trust to make it obvious in the following pages that 
there are even greater agencies at work than climatal 
ones in regulating (albeit within prescribed limits, and 
by slow gradations) the outward contour of the insect 


When viewed geographically, there are two heads 
under which the insects of every individual area may be 
classed : namely, those which were created within its 
bounds, and which constitute its true aborigines (in the 
strictest sense) ; and, secondly, those which have reached 
it, either by ordinary migration over an intervening 
land, or by accidental introduction through human or 
other agencies. Now it is to the members of the latter 
of these ideal divisions that we principally look for any 
positive evidence, whilst discussing the causes of varia- 
tion : since, by the nature of the case, we must have 
identical, or at any rate closely allied species to reason 
upon before any sound conclusions can be drawn con- 
cerning them from the circumstances and conditions 
to which they are severally exposed ; and it is clear, 
that the fact of creatures being specifically coincident, 
and yet under influences remote, does, for the most part, 
actually imply a transportation of them (from their 
primeval centres) beyond the limits of a naturally 
acquired range. Moreover, the avro^Oove^ of the soil 
(if we may be excused the idiom) are in all instances 
adjusted to the peculiarities of the region in which they 
were formed; and, consequently, where they have not 
(as very frequently happens) diffused themselves to a 
sufficient distance from the birthplace of their kind to 
be acted upon in two opposite manners from without, 
the date which they supply, during our inquiry into 
specific modifications as dependent on external disturbing 
elements, cannot be very considerable. 



In spite of this severe distinction, however, which I 
would urge between the insect aborigines of a country 
and those ivhich (whether by compulsion or not) have 
colonized it, and of the preference which (as just stated) 
must be given to the latter whilst investigating the con- 
trolling principles of aberration, I would not wish to 
reject in toto the testimony which the former likewise 
may indirectly furnish, especially under the present 
section, in which climatal causes on a large scale have 
to be taken into account. True it is that we cannot 
hope to descry physical results amongst phenomena 
which are due to the creative force alone ; yet we may, 
in the contemplation of them, recognize such an amount 
of design, or a primary adaptation to conditions from 
without, as shall afford, through its permanence and 
method, fresh presumptive evidence that the " conditions" 
themselves may have some inherent modifying power of 
their own on the aggressors from other districts, in which 
a contrary influence may perchance prevail, and for the 
overspreading of which they were, in the beginning, 
more peculiarly constituted and ordained. 

It has been already mentioned (and, despite the ex- 
ceptional cases which are to be found, it is in a general 
sense true), that the splendour and extravagance of the 
insect world attain their maximum within the tropics ; 
and that the nearer we approach the central heat, the 
more and more unmistakeable is the existence of this 
law. It has been also hinted, that when \iewed on a 
very extensive scale, we shall not derive much direct 


assistance (whilst examining insect-variation, with re- 
ference to climate) from the consideration of a fact thus 
seemingly important, since there are but few species 
whose range is so comprehensive as to embrace, at the 
same time, the equatorial and temperate regions of the 
earth; and since, as lately suggested, it is not from a 
comparison of the aborigines of countries far removed 
that we can hope to derive much positive information 
during our present inquiry. It may be useful however 
to speculate, why the creative energy should have been 
thus lavished, as it were, in the torrid zone, whilst the 
fauna of the cold north is so unpretending and sombre. 
I believe that in the actual number, both of individuals 
and species, which they contain, the difference is not so 
great, between the two latitudes, as might be imagined ; 
and that, were the minims of Scandinavia to be suddenly 
magnified into the giants of Brazil, the Laplanders and 
Swedes might stand a fair chance of being temporarily 
alarmed : nevertheless, as regards the multitude and 
eccentricity of her forms, there can be no question in 
which field it is that Nature has ever delighted more 
particularly to sport. 

Laying aside, therefore, the numerical statistics from 
our account, is not the exuberance of the tropics at once 
responsive to the conditions imposed upon them? Do 
we ask why it is that the insect population is there 
moulded upon a type comparatively so colossal ? let the 
redundancy of the vegetation reply. Have not, also, 
more rapid laws of putrefaction and decay been pre- 

c 2 


scribed than in our cooler clime; and can we imagine 
that it was not in obedience to this decree, that larger 
and more active scavengers were framed ? The gaudy 
wings that float idly on the breeze, and the coats of mail 
which glitter in the light, have they nothing to tell of 
the local circumstances around them ; or, is it too much 
to infer, that a more glorious and stimulating sun re- 
quired creatures of superior brilliancy to bask in its 
rays ? A moderate degree of heat, and that only during 
a certain portion of the year, may suffice in quiescent 
regions to keep up the equilibrium of the organic world, 
the various members of which, whether animals or 
plants, are ensured, in such countries, their alternate 
seasons of activity and rest ; but within the tropics, life, 
in all its aspects, is ever vigorous; and, though the 
several species may have their appointed times of partial 
repose, there is no such thing as tranquillity for the 
mass. Hence it is, that to meet the requirements of a 
Flora * such as there obtains, a less magnificent Fauna 
would have been inadequate ; and we cannot but recog- 
nize, that, in the wonderful and almost endless modifica- 
tions of the insect tribes which people those zones, a 
special provision has been made to check the overgrowth 
of other created things. 

The great preponderance of the phytophagous over the pre- 
dacious tribes, in the hotter regions of the earth, is a remarkable 
fact, and strongly suggestive of the relation which the insect and 
vegetable worlds (both of which attain their maximum in those 
zones) bear to each other. " The carnivorous beetles, or Carabidce," 
says Mr. Darwin, " appear in extremely few numbers within the 


But how, it may be asked, does this primary adapt- 
ation to external conditions affect the question of spe- 
cific development ? Perhaps not much : nevertheless, as 
lately urged, it is well that such adaptations should be 
borne in mind, not merely that due importance may be 
given to influences in conformity with which the creative 
act was at the first expressly regulated ; but also that we 
may be prepared, if any qualifying power be admitted to 
reside in those influences themselves, for the kind of 
aberration which reason and experience would seem 
alike to imply that we should, in the various instances, 

We have already stated, that climate, when taken 
alone, does not appear to produce any very decided 
modifying effect on insect form, seeing that there are 
vast numbers of species of a wide geographical range 
which do not display, on their northern and southern 
limits, differences sufficiently constant to be regarded as 
purely climatal ones -, and it is clear that, if climatal 
causes of themselves were of real primary significance, 
we should probably seldom fail to trace out, from their 
long- continued operation, some steady and positive 
result. Yet when combined with other principles, there 

tropics. The carrion-feeders and Brachelytra are very uncommon ; 
on the other hand, the Rhynchophora and Chrysomelidce, all of 
which depend on the vegetable world for subsistence, are present in 
astonishing numbers. The orders Orthoptera and Hemiptera are 
peculiarly numerous ; as is, likewise, the stinging division of the 
Hymenoptera, the bees, perhaps, being excepted." Journal of 
Researches, p. 34. 


is evidence that a considerable amount of influence must 
be conceded to the action of mere heat and cold, work- 
ing permanently and according to fixed laws, on the 
members of the insect world. Such being the case, it is 
perhaps not surprising that a slight difficulty should 
arise, through our employment of separate sections under 
which to examine the causes of variation ; for, since it is 
ordinarily by the union of several disturbing influences 
that aberrations are brought about, it is for the most 
part impossible to refer the results, however con- 
spicuous they may be, to a solitary controlling element. 
And hence, though we may be able at times to point 
out perchance the single reason for certain phsenomena 
with comparative precision, it will generally happen that 
two or three agents must be appealed to before we can 
arrive at a conclusion by any means satisfactory. I 
would desire, therefore, that the examples hereafter to 
be noticed may be judged of in the mass ; and may not 
be considered as severally assigned, of necessity, to an 
isolated deranging cause, through the fact of their being 
placed, for the sake of convenience, and because of the 
predominance which special controlling principles have 
had in maturing them, under sections, both, as it were, 
exclusive and particular. 

That climate of itself possesses but a limited modify- 
ing power on insect development, is evident from the 
consideration (just alluded to), that numerous species of 
comparatively wide distribution are totally unaffected by 
it. Thus, for instance, the Pissodes notatus, Fab., a weevil 


which occurs in pine forests from Lapland to Barbary, 
and which has been naturalized even in the Madeira 
Islands, passes through the alternations to which it is 
specifically subject, irrespective of country. In like 
manner, the Lixus angustatus, Fab., so abundant in Cen- 
tral and Southern Europe, the north of Africa, Malta, 
Madeira, and the Canaries, and which has been detected 
in Persia, would seem to be perfectly free from atmo- 
spheric control. The Coccinella 7-punctata, Linn., which 
exists in nearly every portion of the Old World, is 
apparently unacted upon geographically. Numberless 
beetles which follow in the track of man, or at any rate 
are liable to do so, almost everywhere (such as Carpophilm 
hemipterus, Linn., Trogosita mauritanica, Linn., Lcemo- 
phlceus pusillus, Schonh., Dermestes vulpinus, Fab., Ano- 
bium striatum, Oliv., Rhizopertha pusilla, Yab.,Sitophilus 
granarius and Ory2&, Linn., and Triboliumferrugineum, 
Fab.), show little or no tendency to variation. Nor is this 
independence of climate to be observed less frequently in 
the aquatic forms, than in the terrestrial ones : the Aga- 
bus bipustulatus, Linn., common in the streams and pools 
of the whole of Europe, the north of Africa, and in Ma- 
deira, although naturally somewhat inconstant, offers no 
aberration, the result of latitude ; as is equally the case 
with the Hydroporus confluens, Fab., w r hich is found from 
Sweden to the Canaries, and the Eunectes sticticus, 
Linn., an insect literally cosmopolitan. The Swallow- 
Tail Butterfly (Papilio Machaon, Linn.), the Clouded 
Yellow (Colias Edusa, Fab.) and the Painted Lady (Cyn- 


thia Cardui, Linn.) , the first and second of which occur 
throughout Europe, in Siberia, Syria, Egypt, Barbary, 
Nepaul, and Cashmere ; whilst the third (so general in 
our own country) has been recorded from India, North 
America, the Brazils, Africa, Java, and New South Wales, 
however irregular they may be, afford no indications'* 
of undoubted geographical instability. 

We need not however multiply examples, since our 
space will scarcely admit of it, and numbers of them will 
be at once suggested to the entomologist : what it mainly 
concerns us here to corroborate, is the thesis, that cli- 
matal operation, although by no means invested with a 
universal qualifying power, has an amount of influence on 
certain species, even whilst unconnected with other ele- 
ments, and therefore, a fortiori, when in combination 
with them. 

The two principal conditions on which climatal causes 
generally may be said to rest, are latitude and altitude. 
As regards the former of these, however, whilst the 
equatorial and arctic regions of the earth will of course 
give us the extremes of heat and cold, we shall often 
perceive differences of temperature (the result perhaps of 
local circumstances) in areas but slightly removed from 
each other, sufficient to affect very materially, though 
by what means it is difficult to understand, the outward 

* Mr. Westwood states that he possesses an individual of the 
Papilio Machaon from the Himalayan Mountains, captured by Pro- 
fessor Royle, " which scarcely exhibits the slightest differences 
when compared with English specimens." The Butterflies of Great 
Britain, p. 4. 


contour of the insect tribes. Thus, to go no further 
than Ireland, we find that the specimens of Silpha 
atrata, Linn., so abundant throughout England and the 
whole of Europe, have put on (it may be from the moist- 
ure of the atmosphere, or from some other obscure 
influence) the appearance of a distinct race, so distinct 
indeed as to have long received another name, S. subro- 
tundata, from British naturalists. I think it far from 
improbable that the Tachyporus nitidicollis, Steph., an 
insect eminently characteristic of that country (and one 
on which I have lately offered some remarks *), is but a 
darker climatal modification of the common T. obtusus : 
and it is well known that the examples of Pelophila 
borealis, Payk., from Killarney and Loch Neagh are per- 
manently larger, and much more metallic, than those 
from the Orkneys. The Nebria complanata, Linn., 
assumes a more pallid hue in the neighbourhood of 
Bordeaux than it does on the sandy coasts of Devonshire 
and Wales : and I have but little doubt that the Omu- 
seus nigerrimuSj Dej., of Spain, the north of Africa, and 
Madeira, is a geographical state of the 0. aterrimus of 
Central Europe. The Sitona gressoria, Illig., so univer- 
sal throughout the Mediterranean districts, Madeira and 
the Canaries, may be but the subaustral form of S. grisea. 
The Bembidium obtusum, Sturm, is shorter and less 
parallel in our own latitude than it is in the Madeiraii 
group and along the Mediterranean shores : whilst the 
Holoparamecus niger, Aube, of Madeira and Sardinia is 

* Zoologist, xiii. p. 4655. 

c 5 


very much paler than the same beetle when taken in 
Sicily. Specimens of Pieris Brassicce, Linn, (the White 
Cabbage-Butterfly, an insect of widely acquired range), 
from Nepaul and Japan, are recorded"* to have differed 
so strongly from the ordinary European type as to have 
been referred, by Boisduval, in doubt to that species. 
Mr.Westwood has received the Vanessa Atalanta, Linn., 
from North America, receding slightly from its British 
analogue ; but which he, nevertheless, does not regard 
as specifically distinct : and such also (he adds) was the 
opinion of Mr. Kirby, who has described his American 
examples under that name. The common Hipparchia 
of Madeira I believe to be a fixed geographical modifica- 
tion of the H. Semele, Linn., of our own country, in 
which the paler bars of the upper surface are evanes- 
cent; there are, however, I imagine, but few entomo- 
logists who would concur with me in this hypothesis. 
The Madeiran specimens of Lycaena PMceas, Linn, (the 
Small Copper Butterfly), are invariably darker, and more 
suffused, than the English ones : and Mr. Westwood re- 
marks that he possesses examples from North America 
which " differ in the decided black spotting of the under 
side of the hind wings, in the bright red streak near 
their hind margin, and in wanting the minute spot on 
the costa of the fore wings ; but that these characters can 
scarcely be held to constitute a distinct speciesf." 
. Few observers can have failed to remark, that increased 

* The Butterflies of Great Britain (London, 1855), p. 17. 
t Id. p. 94. 


altitude frequently corresponds, both in its fauna and 
flora, to a higher latitude ; and that, consequently, if we 
ascend the mountains of a southern land, we shall be 
struck, at times, by the presence of a host of species 
which obtain at a lower level in more temperate zones. 
This is peculiarly traceable in the Madeira Islands, 
which, from their subaustral position, and height (the 
loftiest peak of the central mass exceeding 6000 feet 
above the sea), afford a rich field to the student of zoo- 
logical geography. Yet, though the degrees of mere 
heat and cold are such as to allow, in the two cases, 
species positively identical to flourish ; we should surely 
anticipate some slight change from the different atmo- 
spheric conditions (especially w r hen in union with other 
circumstances) to which they have been, through a lapse 
of ages, respectively exposed : it may be well there- 
fore to inquire, whether experience does at all tend to 
strengthen what our reason has an a priori inclination 
to endorse. It must be recollected however that, in the 
instances to which we would draw attention, small aber- 
rations are all that can be usually looked for, since climate 
of itself does not appear to be very potent in its action. 
We should remember, also, that the boundaries of insect 
instability are restricted ; and, although we would advo- 
cate freedom of development within limits which are 
more or less comprehensive according to the species, to 
pass beyond them would be confusion, and such as could 
result from a lapsus Naturae only, rather than from a 
power of legitimate variation. 


In exact conformity with what the above remarks will 
have prepared us for, we find that the Dromius obscuro- 
guttatus, Dufts., of Central Europe, has undergone on 
the mountain summits of Madeira changes precisely to 
that extent which we should have calculated upon ; and 
although they would seem in reality to be referable to 
climate and isolation combined, yet, since it is not 
always possible (as lately stated) to treat the elements 
of disturbance separately, and it is my object in this 
short treatise to bring forward a few prominent examples 
in support of the considerations proposed, rather than to 
accumulate a mass of material for the registry of which 
my space would be inadequate, I will quote in extenso 
the reflections which, during the compilation of the 
1 Insecta Maderensia/ suggested themselves to me. " The 
Dromius obscuroguttatus is a common European insect, 
and the Madeiran specimens recede from the ordinary 
ones in being slightly larger, and in having their elytra 
more obscurely striated, with the humeral patch less 
distinct : their entire surface, moreover, is of a deeper 
black, a difference which is especially perceptible on the 
legs. It occurs in the greatest profusion in Madeira 
proper, though only from about 5000 to 6000 feet above 
the sea. Although so common throughout Europe, it 
is perhaps, when geographically considered, one of the 
most interesting of the Madeiran Coleoptera, as affording 
a striking example, not only of the modification of form 
in a normally northern insect when on its southern 
limit, but as showing likewise how a species, abundant 


on the low sandy shores and sheltered sea-cliffs of more 
temperate regions, finds its position here only on the 
summits of the loftiest mountains. It is true that the 
aberration from the typical state is not in the present 
instance very considerable ; yet when the circumstances 
producing it are taken into account, I am persuaded 
that the difference is exactly of that nature on which too 
great stress cannot possibly be placed, when discussing 
the general question of geographical distribution as 
having a tendency, more or less directly, to affect both 
colour and form. It is well known to naturalists that a 
multitude of insects from the New World, receding from 
their European analogues merely in certain excessively 
minute characters, have usually been pronounced at once 
as new to science, first because those differences are con- 
stant, and secondly because the specimens have been 
received from the other side of the Atlantic. And yet 
in instances like the present one, in an island which, 
while it belongs artificially to Europe, is yet naturally 
sufficiently distinct from it as to form at any rate a 
stepping-stone to the coast of Africa and the mountains 
of Barbary, species similarly circumstanced are not 
necessarily received as new (and rightly so, I apprehend), 
though in every respect affording differences not only 
analogous to those already mentioned, but in many in- 
stances positively identical with them. If, however, a 
specific line of demarcation does of necessity exist be- 
tween the creatures of the Old and New Worlds, the 
problem yet remains unsolved, so long as intermediate 


islands present parallel modifications, where that line 
is to be drawn. Meanwhile, how far geographical va- 
rieties of this kind, concerning the non-specific claims 
of which confessedly but little doubt can exist, may lead 
to the explanation of the Transatlantic ones just referred 
to, I will not venture to suggest. Yet certain it is, that 
the one case bears directly on the other ; and that, if 
we can prove that common European insects, when iso- 
lated in the ocean, become in nearly all cases more or 
less modified externally in form, there is at least pre- 
sumptive evidence that the law will hold good on a 
wider scale, and may be extended, not only to the 
Atlantic itself, but even to countries beyond. The dif- 
ferences of the present Dromius from its more northern 
representatives are, as just stated, small; nevertheless, 
since they are fixed, those naturalists who do not believe 
in geographical influence might choose to consider them 
of sufficient importance to erect a new species upon. 
But after a careful comparison of this with other insects 
similarly circumstanced, I am convinced that the modi- 
fications in question are merely local ones, and such 
as may be reasonably accounted for by the combined 
agencies of latitude and isolation, and the consequently 
altered habits of the creature, which is thus compelled 
to seek alpine localities in lieu of its natural ones*." 

In like manner the Calathus fuscus, Fab., the Ancho- 
menus maryinatus, Linn., and the Anthicus fenestratus, 
Schmidt, which occur almost exclusively in the loiver 
* Insecta Maderensia (London, 1854), pp. 7> 8, 9. 


regions of northern latitudes, are found in Madeira on 
the mountain tops ; each, moreover, possessing characters 
which are just sufficient (although slight) to distinguish 
them from their European representatives. 

And if we inquire, on the other hand, into the abo- 
riginal species of those islands, or, at any rate, into 
such of them whose naturally acquired range embraces 
the opposite extremes of atmosphere, we shall detect no 
less surely (albeit within a narrower space) the result of 
climatal action on insect form. The Helops confertus, 
Woll., " varies according to the altitude at which it is 
found ; being usually deeply striated and rugose on its 
lower, but subpicescent and much more lightly sculptured 
on its upper limits. I have taken specimens indeed on 
Pico Ruivo, and on the mountain-plain of the Fateiras, 
which are so far diminished in roughness as almost to 
resemble, at first sight, the H. Pluto*" The Pecte- 
ropus Maderensis, Woll., which ranges from about 2500 
feet above the sea to the summits of the loftiest hills, 
although usually with pale legs, is distinguished by 
having its femora almost invariably dusky when on 
its highest elevation ; and, following out the analogy 
with that beetle, the Trechus alticola, Woll., should 
perhaps be regarded as an alpine state of the T. custos. 
The Calathus complanatus, Koll., assumes along the up- 
land heights a very different aspect to what it does in the 
regions below, being generally more piceous and convex, 
altogether broader (in proportion) and shorter, and 
* Insecta Maderensia, p. 516. 


with both sexes (though, of course, especially the male) 

Nor is this principle of topographical variability (the 
result of climate) less apparent in other countries also. 
The Notiophili, for instance, " are extremely unstable, 
both in their sculpture and hue, being subject to con- 
siderable local modifications, though more particularly 
affected, it would appear, by altitude. Thus, in our own 
country, the N. semipunctatus, Fab., one of the common 
representatives of the plains, is found likewise on the 
summits of the mountains ; but at that elevation it be- 
comes liable to great alternations of colour, ranging 
from pale brassy -brown, with the apex testaceous, into 
deep black. The sculpture, however, perhaps is nearly 
as much dependent on other circumstances for its mo- 
dification as upon altitude, since it seems tolerably clear 
that proximity to the sea-shore, especially where the 
localities are saline, will frequently produce a more 
faintly impressed surface"*." It has indeed been lately 
suggested, that the Helobia nivalis, Payk., may be per- 
haps, after all, but a mountain variety of the H. brevi- 
collis ; the Leistus montanus, Steph., of the L.fulvibarbis, 
and the Patrobus septentrionis, Dej., of the P. excavatus ; 
but of this I think further proof is needed, seeing that 
certain species do appear to exist which are strictly 
alpine (that is to say, which have not been, severally, 
detected in the lower regions of more northern zones) ; 
and, in most instances, where aberrations are to be met 

* Insecta Maderensia, p. 17. 


with from the effect of altitude, we have a right to 
inquire (provided the types from which they are sup- 
posed to have originally sprung obtain in the less- 
elevated portions of the same country ), where are the 
intermediate links ? Now I am not aware that any such 
links have, in the examples above cited, ever been ob- 
served ; whilst I can vouch that in at any rate many 
districts where the quasi variety is found, the descend- 
ants of its assumed progenitor do occur in the plains 
beneath. I have remarked that the Cicindelidce often 
become inconstant in colouring as they approach their 
maximum of height above the sea; and I have but 
little doubt that the C. fasciatopunctata*, Germ., from 
Asia Minor and Turkey, is the C. sylvatica modified by 
a long residence in elevated regions. And so it is with 
the Chrysomela, many of which become, in the loftiest 
altitudes to which they ascend (as I have noticed at the 
head of the St. Gothard Pass of the Swiss Alps), subject 
to unusual changes, both in lustre and hue. 

The above examples, although few and indiscriminately 
selected, will serve to illustrate the principle which we 
have been contending for, that climatal influences 
generally, may (and in most instances do) tend to affect, 
more or less directly, the outward contour of the insect 
tribes. It will be remarked that, in the cases hitherto 

* I possess specimens of this insect captured on the summit of 
Mount Olympus by my friend E. Armitage, Esq., who is also of 
opinion that it may be but a mountain state of the C. sylvatica, 


cited no great disturbing power has been made evident, 
the aberrations to which we have appealed being, 
most of them, comparatively minute. This, however, is 
simply in harmony with the belief which we have already 
expressed, that climatal causes, when taken singly and 
alone, are not of primary importance whilst discussing 
the question of specific modification. It remains for us, 
in the following sections, to inquire, whether there are 
any other elements at work from which greater results 
are to be expected. Meanwhile, let us not forget that 
differences may be, in the strictest sense, significant, 
even whilst small ; and that it is their constancy, rather 
than their magnitude, which more particularly concerns 
us in the present treatise, seeing that it is with reference 
to those distinctions which are less conspicuous that the 
greatest amount of misunderstanding (through the fact 
of their being fixed) usually prevails ; whilst it is our 
main object to show that dissimilarities do not neces- 
sarily imply the specific isolation of the creatures which 
display them, merely because they are, in their several 
localities, permanent. 

II. Temporary heat or cold, of an unusual degree. 

It is perhaps unnecessary that the action of temporary 
heat and cold, of an unusual degree, should be considered 
under a separate head from that of climatal causes gene- 
rally ; nevertheless, since the latter are, in a certain 
sense, permanent in their operation, it may be thought 


desirable that I should offer a few words on the effect of 
sudden exceptions to the ordinary routine of things, 
such as, for instance, seasons of peculiar intensity. It 
does not however appear that any very important modi- 
fications do often occur from conditions thus abnormal, 
and as it were accidentally brought about : on the con- 
trary, indeed, it is a well-known fact, that the members 
of the insect world are singularly independent of such 
contingencies ; and that, in the same manner as their 
times of maturation are neither hastened nor retarded 
by them, their external development is for the most 
part free from their control. Yet, in spite of this, 
specific results are wont to happen, ever and anon, from 
such circumstances, as though it were a fundamental 
axiom, that every agent which Nature can press (regu- 
larly or irregularly) into her service should have, though 
it may not always exercise its privilege, some qualifying 

I believe that almost the only deviation from the 
typical state, in insect form, which has been observed to 
originate, par excellence, from the occasional continu- 
ance of undue heat or cold, is curiously enough an or- 
ganic one, having reference to the enlargement of the 
wings. Every entomologist must be aware that a vast 
proportion of the Coleoptera (especially the Carabida) 
are subject to great inconstancy in their metathoracic 
organs of flight. Many species, as the common Calathus 
mollis of our own country (to which my attention has 
been more particularly drawn by the Rev. J. F. Daw son), 


have the hind wings at one time ample, at another rudi- 
mentary, and at a third nearly obsolete. Now, although 
other causes, hereafter to be noticed, would seem to have 
far greater power than climatal ones in permanently 
regulating the size and capacity of these appendages ; I 
think it will be found on examination (and I may add 
that Mr. Westwood is of the same opinion *), that the 
greater or less development of them may be frequently 
explained by the unusual severity of the seasons. My 
own researches would certainly tend to prove, that heat 
does (in the main) favour, and cold retard, their pre- 
sence. Exceptions (often rendered intelligible from 
the evident working of counter influences) will of course 
arise in abundance to this hypothesis ; yet my impression 
is that, upon a broad scale, it will stand the ordeal of a 
rigid inquiry. 

Speaking of certain representatives of the Hymen- 
optera (Chalcididcs) , Mr. Westwood observes: "A 
curious peculiarity exists in one at least of these 
apterous species, which has been noticed by no previous 
author, namely, Choreius ineptus, Westw., which, 
although ordinarily found in an apterous state, was 
discovered by me in considerable numbers during the 
hot summer of 1835, with wings t". And, touching 
the irregularity of the alary organs in the Homopterous 
FulgoridcK, he remarks : " Other instances, in which the 
wings undergo a deficiency of development, occur in the 

* Introduction to the Modern Classification of Insects (London, 
1840), ii. p. 473. t Id. ii. p. 158. 


genus Delphax, the majority of which., in our English 
species, have the upper wings not covering more than 
one half of the abdomen, the terminal membrane 
being deficient, as well as the hind wings. In certain 
seasons, however, especially hot ones, the wings are 
fully developed *". Mr. Curtis has indeed formed the 
undeveloped specimens into a different genus, Crio- 

Although the result of a more stimulating sun may 
be often neutralized by that of isolation (which, as we 
shall hereafter see, is a resistless agent, amongst a host 
of species, in weakening, and frequently rendering abor- 
tive, the powers of flight) ; yet heat, when freed from 
counter influences, may be traced in its permanent effect 
on the alary system of insects, no less than when tem- 
porarily applied. The consideration of this, however, 
belongs strictly to the preceding pages, and we will not 
therefore discuss it here. The common Bed-bug (Cimex 
lectularius, Linn.) is almost invariably apterous, or with 
very short rudimental hemelytra; yet Scopoli (Ent. 
Cam. p. 354) mentions its occurrence with perfect 
wings. Fallen, also, and Latreille, state that it has 
been found winged ; whilst Westwood remarks that it 
has been reported as occasionally winged in the East 
Indies ; and it would seem extremely probable that, in 
these examples, as in numerous others w^hich are on 
record, we may detect the consequences of heat ; either 

* Introduction to the Modern Classification of Insects, ii. 
p. 431. 


as temporarily applied (in an uxmsnal degree), or 
through the accidental transportation of the insect into 
a naturally warmer atmosphere. 

III. Nature of the country and of the soil. 

Before we proceed to inquire to what extent the out- 
ward aspect of insects is liable to be controlled by the 
physical state of the areas in which they severally 
obtain, it may not be altogether out of place to offer a 
few reflections on the superiority which some regions 
possess intrinsically over others, both for the increase 
and diffusion of the animal tribes. To suppose that all 
countries within the same parallels of latitude are 
equally favourable for the development of life (not to 
mention the after-dispersion of it), is contrary to experi- 
ence ; for although (as we have already pointed out) the 
organic world does certainly, when viewed in the mass, 
approach its maximum as we near the tropics, there are 
at the same time so many violations of this law, that we 
cannot admit its operation except in a broad and general 

In a former section of this chapter, I drew attention 
to the fact, that certain islands, equatorial and subaustral, 
are anything but suggestive of their actual positions 
with respect to the line of central heat on the surface of 
the earth. It was with regard to climate alone, however, 
that I wished them to be understood : and it is not 
until now that I have ventured to urge the necessity of 


taking other influences into account also, if we would 
desire to recognize anything like design and adaptation 
(I will hardly call it cause and effect) between the con- 
tinent and the thing contained. It is almost needless to 
add, that there are many elements to be considered, 
such as local atmospheric conditions, excess or deficiency 
of electricity, superabundant moisture, diminished light, 
and the geological composition of the soil, before we 
can hope either to appreciate zoological phenomena as a 
whole, or to reconcile the apparent inconsistencies which 
they are accustomed to display. 

Mr. Darwin, to whom we are indebted for so much 
valuable information concerning the natural history of 
various portions of the world, in his notes on Tierra del 
Fuego, observes : " Beetles occur in very small num- 
bers ; it was long before I could believe that a country 
as large as Scotland, covered with vegetable productions 
and with a variety of stations, could be so unproductive. 
The few which I found were alpine species of Harpalidcs 
and Heteromera, living beneath stones. The vegetable- 
feeding Chrysomelidce, so eminently characteristic of the 
tropics, are here almost entirely absent. I saw very few 
flies, butterflies, or bees, and no crickets or Orthoptera. 
In the pools of water I found but few aquatic beetles. 
I have already contrasted the climate as well as the 
general appearance of Tierra del Fuego with that of 
Patagonia ; and the difference is strongly exemplified in 
the entomology. I do not believe they have one species 
in common ; certainly the general character of the 


insects is widely dissimilar *." Now, it is impossible to 
read this account without being at once struck with two 
primary considerations : first, that there must exist some 
great peculiarity (apart from climate) in a region the 
fauna of which is thus singularly constituted; and, 
secondly, that latitude (however important it may be in 
a comprehensive point of view) must exercise in this 
case a very secondary influence, to allow of localities 
separated only by the Straits of Magellan to present 
differences thus extraordinary. 


Although so dissimilar in many respects, Madeira 
and Tierra del Fuego have evidently much in common 
as regards the conditions which they afford for the 
increase of organic life. Mr. Darwin describes the latter 
as " a mountainous region, partly submerged in the 
sea." So is Madeira. He also adds, that it is " covered 
to the water's edge with one dense, gloomy forest;" 
that " to find an acre of level land in any part of the 
country is most rare ;" and that " within the forest, the 
ground is concealed by a mass of slowly putrefying 
vegetable matter, which, from being soaked with water, 
yields to the foot." Such was Madeira, in its normal 
state t ; and such it still is throughout a large district 

* Journal of Researches, p. 238. 

t That I may not be misunderstood by those of my readers who 
conceive Madeira to be a kind of " arva beata," with the sky for 
ever blue, and (as a consequence) an unclouded sun; I would re- 
peat, that I am not speaking of the vicinity of Funchal only (from 
which the invalids, who resort thither for their health, almost 
exclusively draw their deductions), but of Madeira, and, more- 


towards the northern coast. I cannot indeed refrain 
from quoting the following, since it portrays the cha- 

over, of Madeira as it was, and not of Madeira as it is. More or 
less of cultivation during a period exceeding four centuries, in con- 
junction with the overwhelming fire which completely devastated 
the entire south of the island, immediately after its first settlers had 
taken possession of it, and which is stated (in the accounts which 
are transmitted to us) to have smouldered on for nearly seven 
years, have so altered the features of the country, that it is only in 
the untouched regions of the north (on which the woodman's axe is 
nevertheless encroaching, season after season, with lamentable 
rapidity) that we can catch even a glimpse of its pristine condition. 
The dense forests which then everywhere abounded must have 
caused an amount of moisture and exhalation of which even the 
northern districts as they now are (though saturated, even yet, with 
dampness ; and at a certain elevation almost constantly enveloped 
with clouds) can give us but a faint idea. So tremendous indeed 
must have been the aqueous accumulations which then hung 
around the island, that even the splendour of a southern sun cannot 
have penetrated the atmosphere as it does at present ; and, hence, 
the historical fact that Madeira proper (although separated by a 
channel of only thirty miles in breadth, and now usually visible in 
bold relief against the sky, during a portion, at least, of every day, 
from a far greater distance) was not discovered for an entire year 
after the colonization of Porto Santo, on account of the thickness of 
the canopy which shrouded it from view, is at once rendered in- 
telligible. It is narrated, that, in the year 1419, Prince Henry of 
Portugal organized an expedition to attempt the doubling of Cape 
Bojador ; but the commanders, having lost their reckoning, were 
driven ashore on an island, which they named Porto Santo, in 
commemoration of their escape from the perils of the sea. " On 
their return," says Mr. Harcourt, " Prince Henry sent out Zargo, 
Vaz, and Pestrello, to plant a new colony in the island. It was not 
long before a dark spot was observed on the western horizon of 
Porto Santo. This was regarded by some with superstitious awe ; 
but Zargo concluded it to be clouds attracted by high land ; and 



racteristic features of Madeira so vividly, as to be, lite- 
rally, as suggestive of that island as it doubtless is of 
Tierra del Fuego. " Finding it nearly hopeless/ 7 says 
Darwin, (< to push my way through the wood, I followed 
the course of a mountain-torrent. At first, from the 
waterfalls and number of dead trees, I could hardly 
crawl along; but the bed of the stream soon became a 
little more open, from the floods having swept the sides. 
I continued slowly to advance for an hour along the 
broken and rocky banks, and was amply repaid by the 
grandeur of the scene. The gloomy depth of the ravine 
well accorded with the universal signs of violence. On 
every side were lying irregular masses of rock and torn- 
up trees; other trees, though still erect, were decayed 
to the heart and ready to fall. The entangled mass of 
the thriving and the fallen reminded me of the forests 
within the tropics ; yet there was a difference, for in 
these still solitudes, Death, instead of Life, seemed the 
predominant spirit"*." 

As regards the paucity of species in Tierra del Fuego, 
there are many instances on record of other countries, 
and in various latitudes, in which the same anomalv 


(though perhaps in a less degree) prevails. I have my- 
self observed, in Madeira, large forest tracts, at a con- 
shaping his course in that direction, in spite of the endeavours of his 
crew (by menaces and supplications) to prevent him, he discovered, 
in the year 1420, the island to which, from the trees that covered it, 
he gave the name of Madeira." A Sketch of Madeira, London, 
1851, p. 16. 

* Journal of Researches, pp. 209, 210. 


siderable elevation above the sea, and which are so 
densely clothed with wood as to be scarcely penetrable, 
almost destitute of insect life. Around such altitudes 
however the clouds perpetually cling, and the rain is 
well nigh incessant; and it would seem as if the very 
dampness which causes the vegetation (especially the 
ferns) to flourish in such rank luxuriance, and the timber 
to rot with such rapidity that the gigantic trunks are 
washed, reeking with moisture, down the mountain- 
slopes, was too extreme for animal existence. 

Now, it wdll be remembered that the Madeiran group 
is situated at a corresponding distance from the Equator 
as Morocco, Algeria, the lower limits of Syria, Texas, 
and Upper Florida are, all of which literally teem with 
life; and that Tierra del Fuego lies between the same 
parallels of south latitude as Durham and Central Russia 
do in the northern hemisphere. From which it is 
evident, that the equal removal of countries from the 
earth's greatest heat does not necessarily imply an 
equal exuberance in their Faunas, seeing that in both 
the regions just appealed to, we not only perceive a vast 
difference in the numbers of the insects which they re- 
spectively contain, from those in other districts which 
have a similar divergence from the tropics ; but we are 
even able to recognize a certain resemblance of physical 
conditions (and, therefore, of the creatures which have 
been either adapted to, or modified by, them) in lands 
so far asunder, not merely with respect to latitude, but 
longitude also, as Madeira and Tierra del Fuego. 


Other instances might be cited, in support of the im- 
mediate principle for which we are now contending, 
namely, that many areas have (from local circumstances) 
a natural superiority over others for the increase of the 
animal tribes, even apart from the direct action of heat 
and cold : but space will only permit me to glance at a 
very few of them. We may detect evidences of this fact, 
in Ireland ; which, in spite of the narrowness of the 
straits which separate it from our own country, and of 
its independent commerce with all parts of the civilized 
world, has an insect fauna curiously limited. Prom 
what cause this may arise. whether from some obscure 


physical influences peculiar to the soil, or (as Professor 
E. Forbes has suggested) from the sudden impediment 
which the establishment of St. George' s Channel pre- 
sented to the westward progress of the various species 
from the Germanic plains, it is difficult to speculate : 
yet the fact of its poverty remains, and we must explain 
it as best we are able. There can be no question, that, 
from more frequent communication with England, its 
entomological fauna has of late years been considerably 
increased; and it is equally easy to detect, through an 
examination of its less inhabited provinces, that at a 
period geologically recent its insect population must 
have been singularly scanty. I know of few regions 
(not even excepting the uplands of Madeira) which are 
more deficient in insect life than the mountains of 
Kerry. Although abounding, throughout extensive di- 
stricts, with wood and water, and presenting every appa- 


rent requisite for its full development; the naturalist 
will often be disappointed by finding that a hard day's 
work has not ensured him the same amount of success 
as he would have reaped in less than half an hour in 
many an English meadow. Do we ask, why this is so ? 
it is impossible to reply, except on the supposition 
that there are real physical agents, independently of 
heat and cold, which are unfavourable in Ireland to the 
existence of these lower creatures. We may perhaps be 
told, by the advocates of Professor Forbes' s theory, that 
it is the result of isolation, the quondam land of pas- 
sage having been broken up before the proper comple- 
ment of species had reached this large portion of their 
western destination. But even this, although I believe 
it to contain much presumptive truth, will not alto- 
gether suffice to account for the phenomena which we 
see ; for Ireland is not only remarkable for the paucity 
of its species, but also for the paucity of its individuals, 
and the latter fact cannot be explained by any stretch of 
the migration-hypothesis. We are compelled therefore 
to conclude, that Ireland, like the other countries to 
which we have already alluded, presents conditions 
(altogether irrespective of latitude) which must be re- 
garded as adverse to the general prosperity of the insect 

And so it is with localities (no less than with larger 
countries), many of which are eminently unproductive, 
when compared with others situated at but a short 
distance from them. Thus, the south-western corner of 


England is by far the most unprofitable portion of our 
island, unless indeed I am much mistaken, for insect 
ascendency. I have made some remarks on this subject 
in the ' Zoologist/ from which I extract the following : 
" Unlike the easy collecting to which we are accustomed 
in the more favoured East, miles of unprofitable country 
have often to be gone over, be it swampy moorland or 
iron-bound coast, where scarcely an insect is to be seen ; 
or, at any rate, where the few which exist are so ordi- 
nary, and so sparingly dispersed, as to be scarcely worth 
the labour of obtaining them, more especially since the 
identical species are many of them to be met with in 
the utmost profusion in more central, or eastern districts. 
Whether it be the moisture of the climate, or the vio- 
lence of the south-west winds, which (continually sweep- 
ing, as they do, over the high central mass of Devon- 
shire and the bleak, barren downs of Cornwall) present 
as great an obstacle to the development of animal, as 
they clearly do of vegetable life, I will not venture to 
suggest ; yet certain it is, from observation, that insects 
not only become fewer in number in proportion as they 
are exposed to these external agencies of wind and water ; 
but likewise, in many instances, diminish so consider- 
ably in stature as to be scarcely reconcileable with their 
normal types *." 

There can be no doubt that islands are, for the most 
part, more unproductive (even in proportion) than con- 
tinents ; and that, the smaller the area, the less favour - 

* Zoologist, x. 3616. 


able will it be for the development of insect life. Mr. 
Darwin has noticed this fact in the Galapagos (which he 
remarks are only equalled by Tierra del Fuego, in bar- 
renness), on Keeling Island (in the Indian Ocean), where 
he succeeded in detecting but thirteen species, in St. 
Helena, and at Ascension ; and I have added fresh 
evidence to the same in the various portions of the Ma- 
deiran Group*. It is however to geological causes that 
we must mainly look for the explanation of this pheno- 
menon ; and, therefore, since I propose to examine that 
branch of our subject in a future chapter of this treatise, 
we will not discuss it now. It will also be better per- 
haps to defer for the present the general question of 
se\f- diffusion, which, at the opening of this section, we 
proposed to consider, along with that of insect product- 
iveness (as dependent on other local influences, besides 
climatal ones), it being scarcely possible to render the 
problem of dispersion in any degree intelligible without 
calling in geology to our aid. 

* Considering that I have already detected more than one thou- 
sand species in those islands, it may perhaps be questioned whether 
the same truth is to be gathered from the result of my Madeiran 
researches. I would wish it therefore to be understood, first, that 
my statement refers to that group as contrasted with countries in a 
similar latitude ; and, secondly, that its real fauna is alone taken 
into account, the host of introductions from more northern regions, 
a large proportion of which have probably taken place within a very 
recent period (as may be fairly presumed from the knowledge that 
fresh arrivals, an almost necessary consequence of the importation 
of plants, are occurring nearly every season), having been dismissed 
from our present inquiry. 


Having then disposed of this preliminary appendage to 
our inquiry, by expressing our belief (which I am satisfied 
that observation will tend more and more to corroborate) 
that certain countries and spots are by constitution more 
favourable than others for the increase (apart from the after 
dissemination) of the insect tribes, and that too through 
local influences amongst which mere heat and cold are 
but secondary in importance ; let us proceed to consider, 
how far the nature of the several districts may assist us 
in accounting for some of those numerous aberrations 
from the typical state which various insects are accus- 
tomed to display, and on which it has too often hap- 
pened that "species' (so called) have been attempted 
to be established. I may premise however, that, whilst 
(as already urged) I would regard climate per se as sub- 
sidiary to many other agents, I would not wish to 
ignore its action altogether even under the present sec- 
tion, since in combination with peculiar circumstances 
and conditions it may have (and probably has) consider- 
able controlling power : nevertheless I would desire it to 
be looked upon here as, at any rate, an inferior element, 
and as working in conjunction with physical influences 
of greater significance than itself. If therefore under the 
preceding heads it has been treated (so far at least as the 
exceptions would permit) as a great geographical principle, 
possessing a certain modifying quality on a large scale, 
let us now merely recognize it to the extent in which we 
are actually compelled to do, when dealing with areas of 
smaller magnitude, namely as a topographical one. 


From amongst the many results which I have been 
long accustomed to associate (whether rightly so, or not, 
I leave it for others to decide) with certain special situa- 
tions, I would draw attention to the singular incon- 
stancy which numerous insects are liable to when ex- 
isting on the coast, and which frequently causes them 
to assume an aspect so permanently different from their 
inland types, that, without local knowledge to guide us, 
they might be supposed at first sight to be specifically 
distinct. Ten years ago I offered a few comments on 
this fact in the pages of the ' Zoologist'; which, as I 
have seen no reason subsequently to modify them, I will 
transcribe at length : 

" The extraordinary changes which many insects are 
subject to when occurring near the sea, is a fact worthy 
of notice, and one which I do not remember to have 
seen recorded. The strictly maritime species must be 
left out of the question ; for although many of them are 
exceedingly variable both in size and colour, still we 
have no means of ascertaining whether that variation is 
referable to the locality in widen they are placed, for, 
never being found inland, nobody can have an opportu- 
nity of asserting that the same changes would not take 
place, were they to occur in positions far removed from 
the influence of the sea. When we find, however, the 
same insects in profusion both inland and on the coast, 
and observe also numerous and marked deviations from 
the typical forms peculiar to the latter situation ; then, 
a priori, we have strong presumptive evidence that the 

D 5 


changes in question are the result of local circumstances, 
and not referable to chance. The alteration in size I 
have almost always observed to be from large to small, 
and scarcely ever the reverse ; whereas in colour the 
change takes place very nearly as much from light to 
dark as it does from dark to light : nevertheless the 
majority of instances I possess come under the latter 
department. It has been remarked that all the speci- 
mens of Mesites Tardii, which I captured in Devonshire, 
were much smaller than the original series taken by 
Mr. Tardy at Powerscourt Waterfall, in the county of 
Wicklow ; and so decided was the difference, that many 
of my friends, at first sight, concluded the two to be 
distinct species. This, however, I consider entirely 
owing to their locality, for my specimens were found 
only on the coast, and Mr. Tardy's at a considerable 
distance inland. And, inasmuch as neither of these 
instances rested on mere individual examples, but on 
long and conspicuous series, the certainty of the change 
from large to small was the more apparent. Mr. Holme 
of Oxford mentions having taken Olisthopus rotundatus 
in the Scilly Islands, in great profusion, none of the 
specimens of which exceeded two lines and a half in 
length. At Whitsand Bay in Cornwall I have captured 
Gymnaetron Campanula, none of which exceeded three- 
quarters of a line, the usual length being from a line 
to a line and three-quarters. Anthonomus ater, the 
average length of which is two lines, I have taken a 
series of in Lundy Island, none of which exceeded one. 


In the same locality, also, the common Ceutorhynchus 
contractus scarcely ever reaches its natural size ; and is, 
moreover, so variable in colour, that I was long before I 
could persuade myself that the species was not distinct. 
Instead of the bluish-black elytra which I had always 
considered invariable, they all possess a yellowish or 
brassy tinge ; and the legs, instead of being black, are in 
most instances entirely of a light yellow, and in all, 
more or less inclined to that colour. I have received 
from Mr. Hardy, of Gateshead, specimens of HaUica 
rufipes*, captured by him on the coast, in which the 
entire insect is of a uniform brownish-red hue. Of the 
rare Mantura Chrysanthemi I have taken beautiful 
varieties at Mount Edgcumbe and in Lundy Island, 
many of which inclined to a rich metallic-yellow, instead 
of the brassy-brown of the ordinary specimens : also, in 
the latter locality, particularly dark specimens of Tele- 
phorus testaceus. In like manner, I might enumerate 
other species equally remarkable ; but I trust that those 

* I perceive, on reference to the original examples, still in my 
collection, that this was wrongly quoted as the Haltica rufipes. It 
is the H. exoleta, Fabr., and it is thus entered in Messrs. Hardy and 
Bold's ' Catalogue of the Insects of Northumberland and Durham ; ' 
where they make the observation, " variable in colour ; specimens 
from the sea-coast are frequently of a dark mahogany tint." I have 
myself indeed, since I communicated the above remarks to the 
' Zoologist/ taken its precise counterpart, in abundance, along the 
Yorkshire coast, from Bridlington to the extremity of Flamborough 
Head ; so that it may perhaps be regarded as a topographical state 
which is more especially peculiar to the eastern shores of England, 
north of the Humber. 


already mentioned are sufficient to verify my observa- 
tions,, of the extreme liability to change which, more or 
less, most insects possess when placed within the imme- 
diate influence of the sea. How to account for it, I 
know not. I mention it as a mere fact, and leave it for 
others to assign a reason for its existence*." 

Apparently dependent, in a large measure, on the 
same circumstance (namely proximity to the coast), the 
Bembidium saxatile, GylL, so common at the edges of 
the mountain streams in the north of England, in Scot- 
land, and throughout a portion of Ireland, presents itself 
along our southern shores in the form of a permanent 
variety ; being, as the Rev. J. F. Dawson remarks, "more 
depressed, never narrower in front (the sides therefore 
more parallel), whilst the colour is always much paler 
and the spots larger, that before the apex being round 
and very conspicuous, and the anterior one occasionally 
expanding over the surface very considerably f." I have 
taken it in profusion on the coasts of the Isle of Wight, 
Dorsetshire, and Devon. And so with the Cistela sul- 
phurea, Linn., which in certain maritime localities (as I 
have particularly noticed on the sand-hills at Deal) is 
liable to become so dark in colouring, that, without the 
intermediate shades to judge from (which however may 
usually be obtained in situ], it might stand a fair chance, 
occasionally, of being mistaken for a separate species. 
A Psylliodes in Lundy Island, allied to (if not identical 

* Zoologist, iv. pp. 1283, 1284. 

t Geodepliaga Britannica (London, 1854), p. 186. 


with) the chrysocephala, Linn., found in abundance on 
a Brassica along the ascent from the eastern landing- 
place, varies "in every consecutive shade between the 
limits of light yellow and dark metallic-green "^/^ the 
former of which states (the normal one on that rock) 
might have been fairly set clown as specifically distinct 
from the latter, did not observation on the spot decide 
the question for us without doubt. 

Another curious example of the effect of local in- 
fluences (amongst which proximity to the shore plays, 
in all probability, an important part) on the external 
aspect of insects exists in the Aphodius plagiatus, Linn., 
which in this country is generally deep black. " It is 
a circumstance worth noticing," I remarked in the 
' Zoologist/ in 1846, " that the form which is looked 
upon by the continental naturalists as the variety, is in 
England evidently the typical one, for out of about 
sixty specimens which I captured [at Tenby in South 
Wales], only two possess the conspicuous red dashes on 
the elytra which are considered abroad as the almost 
invariable accompaniment." I have observed the same 
peculiarity in the flat and damp spots between the sand- 
hills at Deal, where I have never detected a single in- 
dividual which is not perfectly dark ; and I believe that 
the greater number of the specimens which were ori- 
ginally taken at Wisbeach, in Cambridgeshire, offered the 
same geographical characteristics; whilst those which 
were found near the more inland towns of Peterborough 

* Zoologist, iii. p. 900. 

and Norwich present a larger proportion of the ordinary 
European state. The blood-red dashes, however, with 
which the elvtra of numerous insects are adorned, I have 


constautlv remarked possess a singular teudencv to be- 

come evanescent. It is indeed almost diagnostic of the 
genus Gymnaetron, either that its representatives should 
be thus ornamented typically., or else that those which 
are normally black should, when they vary, keep in view, 
as it were, this principle for their wanderers to subscribe 
to. Thus, I have no doubt that the G. Veronica, Germ., 
is but a variety of the G. niger, an opinion which T 
expressed in the ' Zoologist ' nine years ago. "Whilst 
commenting on the Coleoptera of Dorsetshire, I then 
stated, that " for my own part I must confess I should 
have doubted the G. Veronica beins: really distinct from 

C? if 

the G. niger, for red dashes on the elytra seem naturally 
peculiar, more or less, to the whole genus ; and I should 
therefore have suspected that, had occasional aberrations 
from a black type existed (which is not unlikely), those 
aberrations would probably assume a form which is so 
common in the other species of the generic group*." 

The Bembidium bistriatum, Dufts., is usually much 
paler when found in saline districts (under which circum- 
stances it was described as a distinct species by Mr. 
Stephens) than when occurring in more inland positions. 
The Blemus areolatus, Creutz., I have frequently re- 
marked is similarly affected in brackish places : and I 
think it far from improbable that the Stenolophus Skrim- 

* Zoologist, v. p. 1941. 


shiranus, Steph., is but a local modification (though not 
altogether, perhaps, through marine influences) of the 
S. Teutonus, Schr. The Dromius fasciatus, Gyll., not 
being exclusively littoral, may be quoted as another case 
in point, the specimens which are collected near the 
coast being for the most part singularly pale. In 
speaking of the Anthicus bimaculatus , Illig., M. de la 
Ferte observes : " II y a seulement lieu de remarquer que 
les individus du bord de Focean soiit geiieralement plus 
pales que ceux des contrees orientales de FEurope, et que 
ceux des cotes de France et de Belgique sont entierement 
depourvus de tache discoi'dale*." And bearing, in much 
the same manner, on the subject of variations, the Anthi- 
cus humilis, Germ., " est une des especes le plus generale- 
ment repandues en Europe; mais il lui faut le voisinage 
de Feau salee. Aussi on le rencontre non-seulemeiit sur 
les rivages de toutes les mers, meme de la Baltique, mais 
encore aux bords des lacs sales, tels que celui de Manns- 
feld, en Saxe. Ceux de cette derniere localite sont gene- 
ralement noirs ; ceux que j^ai pris a Perpignan sont d^un 
rouge tres-clair, ce qui me porte a croire que cette espece 
est dans le meme cas que quelques autres Anthicus, dont 
les varietes les plus foncees appartiennent au nord de 
FEurope, et les plus pales au midif." 

Whilst touching on this immediate question of varia- 
bility as dependent to a great extent, in numerous cases, 
on proximity to the sea } we may just notice the marked ten- 

* Monographic des Anthicus (Paris, 1848), p. 149. 
t Id. pp. 127, 128. 


dency which even the insects peculiar to saline spots would 
seem in a large measure to possess, of converging, more or 
less obviously, to a lurid-testaceous, or pale brassy hue, 
in their colouring. True it is that we cannot (as above 
suggested) deduce any evidence of direct physical modi- 
fications from amongst species which are strictly mari- 
time, seeing that we have no means of judging in such 
instances whether similar phenomena would or would 
not be produced in central districts also : nevertheless 
we may perhaps detect in this general law some slight 
indication of the effects which an atmosphere and soil 
constantly impregnated with salt would be likely to 
bring about in the external aspect of those members of 
the insect tribes whose range is sufficiently extensive to 
expose them to its operation. The bare mention of 
such names as Nebria complanata and livida, Calathus 
mollis, Pogonus luridipennis, Trechus lapidosus, Aepus 
marinus and Robinii, Cillenum laterals, Bembidium scu- 
tellare, ephippium andipallidipenne, Ochthebius marinus, 
Psylliodes marcida, Phaleria cadaverina, Helops testa- 
ceus, and Anthicus instabilis, so eminently characteristic 
as they are of briny situations, will at once appeal to 
our native entomologists ; whilst the acknowledgement 
of the same principle is no less conspicuous in a host 
of other species which are not included in the British 

Hence, when we see the tendencies of coloration (not 
to mention other particulars, often readily apparent) 
essentially the same, both in insects which are peculiar 


to, and in those which have overspread (from without) 
certain regions or localities, it is impossible not to asso- 
ciate some inherent controlling power with the regions 
themselves ; and we are driven to the conclusion, that 
either well-defined races have been gradually shaped out, 
by means of the physical influences to which they have 
been exposed, or else that the species themselves (as 
witnessed by the intermediate geographical links, which, 
although sometimes rare, are in all instances to be found) 
do assuredly merge into each other. 

In addition to those which we have been just discuss- 
ing, there are other influences (equally independent of 
mere heat and cold) by which insect modifications may 
be brought about, modifications moreover of that pre- 
cise character which must be referred, in general terms, 
to the nature of the country and of the soil in which 
they severally obtain : a very few examples, however, in 
illustration of their action, must suffice for our present 
purpose. The Tarus lineatus, Schonh., is slightly shorter 
in Madeira, as also somewhat darker on its head and 
prothoracic disk (and with its elytral striae less deeply 
impressed), than it is in Algeria and Spain. The 
Madeiran specimens of the Aphodius nitidulus, Fabr., 
are usually a little paler, and more distinctly punctu- 
lated, than their northern analogues ; as are also, in 
the latter respect, those of the Clypeaster pusillus, Gyll. 
The Scydmanus Helferi, Schaum, is permanently smaller 
in the Madeiran group than it is in Sicily; and I 
believe that the Achenium Hartungii, Heer, of those 


islands, is but a local state of the A. depressum, Grav., 
of Central Europe. The Bembidium tabellatum and 
Schmidtii, Woll., may be in reality but geographical 
modifications of the B. tibiale and callosum of higher 
latitudes ; and the Malthodes Kiesenwetteri, Woll., of 
the common European M. brevicollis. Calcareous deposits 
would appear, ever and anon, to have considerable effi- 
cacy in regulating the outward aspect of such species as 
are able to adapt themselves to different geological 
districts ; and when in juxtaposition with the shore, 
their effects are often very conspicuous. The Dromius 
arenicola, Woll., is the Portosantan representative of 
the D. obscuroyuttatus, Dufts. ; and distinct as it is in 
colouring from that insect (as evinced both in Madeira 
proper and throughout Europe), I believe it to be in 
reality but a local condition of it, occasioned by a resi- 
dence through a long series of ages on a calcareous soil. 
For the same reason perhaps (though assisted, in all 
probability, by the qualifying power of isolation), the 
Hadrus illotus, Woll., may be specifically identical with 
the Madeiran H. cinerascens. In like manner, the Bem- 
bidium Atlanticum, Woll., which in Madeira proper is 
frequently so dark that its elytral patches are sub- 
obsolete, and which is but seldom brightly arrayed in 
that island, assumes in Porto Santo (which is not only 
more calcareous than the central mass ; but is strongly 
impregnated, as its streams and rills everywhere testify, 
with muriate of soda) a permanently paler hue, being 
at times almost testaceous. Some districts seem to be 


more prolific in varieties, generally, than others. The 
neighbourhood of Ipswich, in our own country, has 
been cited by Mr. Curtis'* as possessing this peculiarity ; 
and I have remarked a similar tendency in certain parts 
of Ireland. The common Haliplus obliquus, indeed, of 
the Black water river, in the county of Cork, is usually 
so dark and suffused in colouring, that it might be 
almost taken for a distinct species, its fascise, especially 
the hinder ones, being occasionally evanescent. 

One more example must satisfy us under this section, 
namely, the Harpalus vividus, Dej., of the Madeiran 
group. So curiously is that insect affected by the 
nature of the areas through which it successively as- 
cends, and that too irrespectively of heat and cold (as 
may be gathered from the fact that its phases on the 
shore and upland heights are well nigh coincident), that 
it may be appropriately singled out as a concluding in- 
stance of the effects of those obscure local influences to 
which we have been drawing attention. " Ranging 
from the beach to the extreme summits of the loftiest 
mountains, accommodating itself at one time to a low 
barren rock of 20 yards circumference, at another to the 
deep-wooded ravines of intermediate altitudes, around 
which the clouds perpetually cling, and where vegeta- 
tion and decay are ever rampant, or harbouring beneath 
the rough basaltic blocks of the weather-beaten peaks 
(6000 feet above the sea) -, we should naturally expect, 

* Proceedings of the Entomological Society of London (Part 3. 
New Series), p. 4. 


a priori, to discover some slight modifications of out- 
ward structure, according as the respective localities 
differed in condition. And such we find to be every- 
where the case. I am satisfied, moreover, that it is 
only by a careful observation on the spot that an insect 
like the present one can be properly understood ; for, to 
anybody acquainted with it practically in all its phases, 
it is but too evident how many ' species ' (so called) 
might be established on undoubted varieties, where 
there exists a desire for creating them, and where our 
sole knowledge is gathered from a few stray specimens 
collected by another person, and unaccompanied by local 
information to render the aberrations intelligible. For 
it must be tracked from the shore to an elevation of 
more than 6000 feet before we are enabled to discern 
the causes by which its development is controlled, or 
even to connect by slow and easy gradations its opposite 
extremes of form. And it is an interesting fact, that 
the distance between its variations does not increase in 
proportion to the distance between its altitudes. On 
the contrary, it would seem to pass through its minimum 
of size and maximum of sculpture at about the elevation 
of from 3000 to 4000 feet ; both above and below which, 
that is to say, as it recedes from the upper and lower 
limits of the sylvan districts, it becomes gradually 
modified, and almost in a similar manner. Thus, to a 
person who had visited Madeira and had picked up 
specimens on the coast, and to another who had per- 
chance penetrated into the interior, as passing visitors 


from the vessels are accustomed to do, and had brought 
away examples from the wooded mountain-slopes, the 
two insects would appear altogether distinct. For, com- 
mencing on the level of the beach, the usual type is 
broad, flat, more or less opake, with the prothorax 
almost impunctate, and the elytra soldered together. 
As we ascend higher, the breadth invariably diminishes, 
the brightness, and depth of sculpture, seem (up to a 
certain altitude) to increase, and the elytra are seldom, 
or but very imperfectly united ; until, on entering the 
lower limits of the forest region, at an elevation per- 
haps, ore rotundo, of 3000 feet, we find that it has 
gradually put on a very different aspect, being small, 
narrow, bright, convex, comparatively ovate and deeply 
striated ; the legs and antennse have become exceedingly 
pale ; the prothorax has altered considerably in shape, 
being much narrowed behind and punctured; and the 
elytra are nearly always free. In this state it continues 
for about 1500 feet; when again emerging into the 
broad daylight of the open hills, it recommences to 
mould itself as it did below ; until, having reached the 
summits of the loftiest peaks, more than 6000 feet above 
the sea, it has almost (though not entirely) assumed the 
features which characterized it on the shores beneath*." 

* Insecta Maderensia, pp. 55, 56. 


IV. Isolation ; and exposure to a stormy atmosphere. 

Having in the preceding pages touched upon the sub- 
ject of insect variability, as the occasional result, to a 
greater or less extent, of climatal and other influences ; 
let us now proceed to consider the importance of a 
certain physical condition, which will be found, I believe, 
on inquiry, to be accompanied by a more decided modi- 
fying power than any which we have yet discussed. 

Every one who has examined the natural history of 
islands, both in theory and practice, must be aware of 
the many difficulties which have constantly to be en- 
countered, before the several phenomena can be satis- 
factorily explained. Laying aside those forms which 
are manifestly endemic (the numerical proportion of 
which usually accords with the distance from the nearest 
mainland), again and again are we baffled by the near 
resemblance of the various creatures to continental 
types, whilst the minute differences which they display, 
from them, are at the same time so permanently fixed, 
that we are almost precluded, under the ordinary ac- 
ceptation of a " species," from regarding the two as un- 
doubted descendants of a common stock : and thus it is 
that insular faunas have frequently been magnified, in 
the novelties which they are supposed to contain, far 
beyond what is right. A person however who looks to 
the causes of things, and is prepared to recognize effects 
where there are fair grounds for anticipating them, will 
not be slow to perceive, that, in the small deviations 


which we are so often accustomed under such circum- 
stances to behold, the results of isolation itself (as an 
active controlling principle) may be traced out ; whilst 
geology, ever ready to lend a helping hand when ap- 
pealed to, will seldom fail to supply those intermediate 
links of probability which the believer in specific centres 
of creation must needs subscribe to, before he can draw 
any deductions on a broad scale, or be competent to 
analyse even the general bearings of a question thus 
necessarily comprehensive. 

Having thought it desirable to defer to a subsequent 
chapter of this treatise the few geological reflections 
which our subject may give rise to, it will not be my 
aim to allude to them in the present section more than 
is absolutely requisite. I propose rather to consider 
some of the ordinary effects of isolation, as mere matters 
of experience ; and to allow geology to tell its own tale 
when we come to examine the problem of self-dispersion, 
as occasionally interrupted by subsidence. 

If we except a few of the Heteromera and apterous 
Curculionida, which appear to be influenced in a dif- 
ferent manner, the power of isolation over insect form is 
perhaps more especially to be detected in a deterioration 
of stature. Whether this principally emanates from the 
constant irritation of a stormy atmosphere, such as 
small islands are of course exposed to, and which would 
seem to have stunted the development (during a long 
series of ages) of the animal and vegetable worlds, or 
from a diminution of area consequent on the breaking 


up of a continuous land, it is difficult to pronounce : 
nevertheless, it is most consistent with both reason 
and analogy to suppose that each of those causes has 
operated to induce a similar result ; and that we must 
therefore view them as working in concert, if we would 
appreciate their action aright. 

It is a law to which a large proportion of the organic 
creation would appear to be subject, that the exuberance 
of life (not so much, however, as regards the number of 
individuals which the various species may present, as in 
the grandeur of their size) has reference to the magni- 
tude of the spot over which it is permitted to range. 
The unnatural breeding-in of a single race, which must 
of necessity happen unless the intercourse with other 
varieties of its kind be possible, has always been attended 
with effects more or less pernicious ; and in the Annu- 
lose tribes I believe that the reduction of space which 
geological convulsions have at various epochs brought 
about, has been commonly succeeded (inter alia) by a 
reduction of stature in those species which have been 
cut off from their fellows. I do not assert that there are 
no exceptions to this rule ; for counter-influences may 
at times prevail (as we shall shortly see), to neutralize 
the above tendency. I hold it, however, as an absolute 
truism, in physics, that a law without an exception is 
an anomaly. If, therefore, we were once to admit the 
latter to negative the former, no such thing as a law 
could exist. Hence it follows, as a corollary (unless, 
indeed, we are prepared to endorse that conclusion), that 


where there is a law there must be an exception to it; 
and that, consequently, exceptional cases, if not exceed- 
ingly numerous, should never pervert our belief from an 
otherwise presumptive truth. 

This dwindling- down of size has seldom failed to 
attract my attention, more or less, in almost every island 
which I have hitherto had an opportunity of exploring : 
space, however, will not permit me to dwell upon many 
instances. I have already adverted to the diminished 
stature of Anthonomus ater, Mshm, and Ceutorhynchus 
contractus, Mshm, in Lundy Island, the first of which 
scarcely ever reaches, on that rock, more than half its 
natural bulk. The late Mr. Holme, of Corpus Christi 
College, Oxford, in like manner, captured the com- 
mon Calathus melanocephulus, Linn., and Olisthopus 
rotundatus, Payk., in Scilly, the former of which 
seldom exceeded two lines, and the latter two and a 
half, in length : and he also recorded, that the Bolito- 
chara assimilis, Kby, is invariably smaller in those 
islands than it is in the neighbourhood of Penzance *. 
The Vanessa Callirhoe, Fabr. (a geographical analogue of 
the Red Admiral Butterfly t, so common in our own 

* Trans, of the Ent. Soc. of London, ii. pp. 59, 62. 

t Considering that the true Vanessa Atalanta, of more northern 
latitudes, does occasionally occur around Funchal, it may be reason- 
ably contended that the fact of its coexistence (on the same spot) 
with the V. Callirhoe is strong presumptive proof that the latter is 
a true species, and no climatal or insular modification of the former. 
And so, judging from a distance, and without local evidence to ex- 
plain this phenomenon, I should have concluded myself : never- 



country) , is permanently smaller in Porto Santo than it 
is on the larger, more luxuriant and varied, and there- 
fore more protected, island of Madeira proper. And, as 
regards the Ptini of that group, so completely are some 
of them "affected by isolation, and by exposure to a 
perpetually stormy atmosphere, that they do not attain 
half the bulk on many of the adjacent rocks that they 
do in the more sheltered districts of the central mass ; 
and so marvellously is this verified in a particular 
instance, that I have but little doubt that five or six 
species (so called) might have been recorded out of one, 
had only a few stray specimens been brought home for 
identification, without any regard having been paid to 
the respective circumstances under which they were 
found *." That " one," Protean, representative is the 

theless, recollecting how easy of transport the larvas and pupse of 
Lepidoptera necessarily are (of which we have the plainest assu- 
rance in the almost certain introduction of the Pontia Brassica, 
Sphinx Convolvuli, Acherontia Atropos, &c. into those islands), 
especially in a region which for more than a century has been 
receiving a constant supply of vegetables and ornamental plants 
from western Europe ; I am induced to believe that the appearance 
of the Atalanta is a comparatively recent one, whilst that of the 
Callirhoe (which, unlike the typical Red Admiral, has naturalized 
itself in nearly all portions of the group) must be referred to the 
remote period when migrations over a long-lost continuous land 
were in regular operation. The slowness of the change, in external 
aspect, which the isolation of insects from geological causes would 
seem to bring about (and which follows, as a corollary, if the above 
conclusion be true), I propose to discuss in a subsequent chapter of 
this work. 

* Insecta Maderensia, p. 260. 


Ptinus albopictus, Woll. ; and it is so eminently a case 
in point, that it may be admissible to quote, in eoctenso, 
a few of the observations which I have already pub- 
lished concerning it : 

" The P. albopictus is the commonest of the Madeiran 
Ptini, and by far the most variable, having a separate 
radiating-form for almost every island of the group, 
whilst, at the same time, the whole are so intimately 
connected together (and merge into each other) by 
innumerable intermediate links, that it is impossible to 
regard them, in spite of the opposite contour of the 
extremes, in any other light than as different aspects of 
a single species, according as circumstances may favour, 
retard, or otherwise regulate its development. Insta- 
bility in fact (in its broadest sense) may be considered 
to be one of its most prominent characteristics, since it 
appears to be more sensitive to isolation and altitude 
than any of the other members of the genus with which 
we have here to do, as may be proved to a demonstra- 
tion by a careful study of its habits on the spot, where 
the influences of position and exposure are, in nearly all 
instances, more than sufficient to account for the suc- 
cessive phases assumed. Thus, commencing with var. a, 
which reaches its maximum in the sheltered ravines of 
the central mass, the bulk is usually large, and the tints 
comparatively intense. Var. /3. is likewise brightly 
variegated, but it is smaller. Now, if our premises be 
correct, that locality and the action of the external 
elements have much to do with the changes in question, 

E 2 


we might have expected, a priori, that this state, from 
its peculiarity to the Dezerta Grande, would not only 
have reduced in dimensions (which, it is), hut in colour 
also (which it is not). Here, therefore, observation, in 
situ, becomes extremely important; since such does at 
once convince us that its almost exclusive attachment to 
the interior of the stalks of the Silybum Marianum, 
Grtn. (the Holy Thistle of the ancients), with which the 
more protected portions of that island everywhere 
abound, affords it ample conditions, even on so bleak a 
rock, for its completion. Nevertheless, its stature (as 
already stated) is slightly diminished in spite of this : 
and when we come to examine the individuals which 
infest the lichen of more open situations (aberrant how- 
ever on the Dezerta Grande, and answering to the var. y. 
of the diagnosis), we immediately perceive that both of 
our required results are indicated, the reduction not 
being limited to size, but extended also to hue. In 
Porto Santo this modification is the normal one, where 
the insect likewise displays the same lichenophagous 
tendency, and where the districts in which it exists are 
equally barren. But, if its maximum be attained in 
Madeira proper, and a certain number of minor devia- 
tions range throughout Porto Santo and the Dezerta 
Grande, it still remains for us to show where its minimum 
is to be obtained : which, true to the modus operandi by 
which we have conjectured its divers degrees of abortion 
to have been brought about, would seem to be centred 
on the Northern Dezerta, or Ilhco Chao. When we bear 


in mind the minute dimensions of that flattened rock, 
which does not include so much as a single valley, or 

/ * 

depression, within its bounds, and is consequently seldom 
free from the violence of the winds (which sweep across 
it incessantly, from whatever quarter they may arise) ; it 
could hardly be supposed that an insect which is so obvi- 
ously subservient to atmospheric control should not have 
become materially affected, in its outward guise, through 
long seclusion on such a spot : and accordingly we are 
not astonished to find the race which has been thus cut 
off for ages on this extraordinary little island, itself as 
extraordinary. It is indeed very remarkable to trace 
out how clearly the agencies we are discussing have here 
operated on the species under consideration, for both 
sexes (though especially the male) descend on the Ilheo 
Chao to somewhat less than half a line in length, being 
literally of scarcely greater magnitude than some of the 
larger representatives of the Ptiliadce \ "* 

I stated above, that, although this diminution of 
stature is a very general accompaniment of isolation, 
amongst insects which have been long cut off from the 
rest of their kind, there is no rule without an exception 
to it ; and that, therefore, we must not always anticipate 
the result which has been described. We should re- 
member that immense periods of time are apparently 
necessary before any perceptible change can come over 
creatures from the stoppage of their migratory progress, 
and the unnatural in-breeding of their several tribes ; so 

* Insecta Maderensia, pp. 268, 269. 


that in islands geologically recent (which often implies, 
however, their existence through epochs which would 
sound vast indeed to ears unscientific) we must not in- 
variably expect to discover evidences of this law. On 
the contrary, we must first of all take into account the 
age of their formation, before we can judge a priori as 
to the probability of its operation through a sufficient 
interval of time to have become conspicuous in its 
effects. I say " through a sufficient interval of time," 
because the process of deterioration may be silently 
going on, even now, in many an island, which has not yet 
shown any matured traces of its action, except perhaps 
in the case of a few species which appear to be more 
particularly susceptible to contingencies from without. 
We should then call to mind, that an enormous propor- 
tion of nearly every insular fauna is composed of acci- 
dental colonists during the last few centuries, in which 
civilization and commerce have been unintentionally at 


work in the cause of animal diffusion ; and that, there- 
fore, if modifications in outward contour have not neces- 
sarily resulted during a positive geological interval, it 
would be absurd to look for them in the mere settlers 
(as it were) of yesterday. 

Thus, it will be perceived, how necessary it is to take 
every element and contingency into account before we 
venture to pronounce dogmatically on either the exist- 
ence or non-existence of any physical law; and how 
cautious we should be of denying the legitimate opera- 
tion of external influences in one region, because they 


would seem, primd facie, to be contradicted in another. 
It is surely more philosophical to endeavour to reconcile 
the two, by tracing out (as may frequently be done) 
some opposing principle in the latter, which shall enable 
us to understand the discrepancy, and to believe that 
the same action may be going on in both cases, but that 
in one of them it is either overruled by a greater con- 
trolling power than itself, or else has not had sufficient 
time to bring its fruits to maturity. If a proposition be 
true, we should recollect that it is always so (under all 
the circumstances and conditions to which it is appli- 
cable) ; for, otherwise, it would be both true and false, 
which is absurd : hence, if my premises be true, that 
the general tendency of isolation is to diminish the 
stature of those insects which have become isolated ; it 
follows that that tendency must remain, so long as there 
are no other special disturbing influences to absorb or 
neutralize it. " When any observation," says a writer 
of the last century, " hath hitherto constantly held true, 
or hath most commonly proved to be so, it has by this 
acquired an established credit : the cause may be pre- 
sumed to retain its former force ; and the effect may be 
taken as probable, if in the example before us there doth 
not appear something particular, some reason for excep- 
tion*" Hence it is, that, even amongst the opposite 
phenomena which one island may occasionally present 
from those of another, I have often been able to recog- 
nize the working of a selfsame law ; and clearly to detect, 
* Religion of Nature Delineated, p. 99. 


that it is not from its failure, in either instance, that 
contending results are brought about, but simply that 
some counteracting agent has been exerting its energy 
in the one case, so as to nullify what would have other- 
wise come to pass. 

The main object however of the present section being 
to show that a considerable amount of power is due to 
isolation itself, in regulating (after a long series of ages) 
the outward aspect of the insect tribes, it is not strictly 
necessary that we should so rigidly insist on deteriora- 
tion of size as one of its primary consequences, since 
(whether it be so or not) we are merely concerned here 
to demonstrate, that its influence, in some shape or other, 
is absolute and real. 

After the above remarks, we shall not be surprised 
that the phenomena displayed in certain islands, as 
regards size, are sometimes (though I believe it to be an 
exception to the ordinary rule) the exact opposite of 
what we have been describing. Let us not however be 
alarmed at this fact, on the bare statement of it, as 
though the proposition which we have been lately ad- 
vancing were at once disproved ; since we shall find, on 
inquiry, that the case is not so desperate as might be 
imagined; and that in many islands where even this 
principle is to be detected, we may recognize traces of 
the other also. But how, it will be asked, can this be ? 
for, since the influences are the same, creatures simi- 
larly exposed to them must be similarly affected. Now, 
although, on a broad scale, suck a notion contains much 


presumptive truth, on a narrower one it does not always 
apply ; for species are differently constituted ab ovo, and 
will sometimes give a different result from the operation 
of causes which are identical. Moreover, there is a 
curious tendency which I have remarked in most islands, 
that the wings (especially the metathoracic ones) of their 
insect inhabitants are liable to be retarded in their 
development, often indeed to such an extent as to 
become actually evanescent : and I believe it to be a law 
of Nature, that when any particular organ is either 
stunted or taken away, the creature receives a compensa- 
tion for its loss either by the undue enlargement of some 
other one*, or else in a general increase of its bulk. If 
such be the case, the presence of two apparently con- 
flicting effects in a single island is rendered somewhat 
more intelligible ; nevertheless, on the above hypothesis, 
the specimens which increase in dimensions should un- 
doubtedly have their organs of flight more or less en- 
feebled, w r hilst those which diminish should be regularly 
winged. And hence we arrive at the question, is this 
so ? My own experience would certainly tend to prove 

* Although the result of a primary (or creative) adjustment to 
special circumstances, rather than of a secondary adaptation, 
brought about by a self-modifying capability ; we may just call 
attention to the fact, that most of the blind insects, whether asso- 
ciates within the nests of ants, or natives of subterranean caverns, 
have either their palpi or antennae anomalously developed, as 
though, partially (although how, and in what degree, we cannot 
possibly ascertain), to make amends for the inconvenience Avhich a 
total want of sight must necessarily entail. 

E 5 


that it is ; and I suspect that future observations will 
confirm the fact. Meanwhile, I must content myself 
with simply advancing the subject for consideration., and 
with recording such few examples, in support of the 
theory, as space will permit, and which occur to me 
almost spontaneously. 

The Madeiras would seem to inherit, as it were, a 
more than usual control over the alary system of their 

V V 

insect population ; for, out of about 550 species of Co- 
leoptera which I have hitherto met with in that group, 
nearly 200 are either altogether apterous, or else have 
their organs of flight so imperfectly developed, that they 
may be practically regarded as such ; so that, if our 
preceding conclusions (from the compensation-hypo- 
thesis) be correct, we should a priori anticipate an in- 
crease of bulk in those islands, rather than a decrease 
of it. Unfortunately the greater number of these 200 
representatives are now, through the submergence of the 
once surrounding continent, endemic, so that we have 
no means of judging whether the obsoleteness of their 
wings is to be referred to the long action of Madeiran 
influences *, or whether they were thus created severally 

This is certainly rendered probable, however, from the fact that 
a large proportion of these apterous species are members of genera 
which are usually winged, such as Tarns, Loricera, Calathus. 
Olisthopus, Argutor, Trec/ius, Hydrobius, Ephistemus, Syncalypta, 
Phlwopliayus, Tychius, Longitarsus, Chrysomela, Scymnus, Cory- 
lophus, Helops, and Othius, whilst the knowledge that, out of 
twenty-nine genera which I believe to be endemic in those islands. 
six only are winged (the remaining twenty-three being apterous), 


in the beginning ; and, for the same reason (that is to 
say, having no others of their kind to compare them 
with), we cannot pronounce, even if we might assume 
this partial organic decay to be the consequence of their 
isolation on these rocks, whether their general stature 
has been subsequently augmented or not. Still, there 
are some few, out of the 200 just alluded to, which are 
of common European distribution ; and, as these would 
appear to have obeyed the principles to which we have 
been calling attention, it is not unreasonable to suppose, 
that many of the others (could we but behold them as 
they formerly were, emigrants over a vast continuous 
land) would be found to have done so also. 

I alluded, in a previous section, to the Dromius 
obscuroguttatus, Dufts., as presenting permanent charac- 
teristics in Madeira, the combined result of latitude 
and isolation ; and I also stated that it was not always 
possible, whilst dealing with physical agents which are 
necessarily obscure, to refer the respective phenomena 
(whatsoever they may be), which would seem to have 
departed from their types, to a single disturbing cause. 
Hence, whilst I there acknowledged latitude as in part 
answerable for the changes which that insect has under- 
gone, I may here suggest that it is, in all probability, 
to isolation that we must mainly look, if we would under- 
stand those changes aright. But what are the distinctive 

will not tend to diminish the probability that there is something 
peculiar in the action of Madeiran influences generally on the alary 
system of the insect tribes. 


features, it may be asked,, which the D. obscuroguttatus has 
adopted, since its first arrival from more northern latitudes 
over an unbroken* continent ? It has not altered much, 
after all : it is, however, the nature of the alterations, 
and their constancy, which give them their real import- 
ance. In a few words then, the insect is rather larger 
and more robust than its European analogue, and (to 
omit other minor differences) its wings are evanescent. 
But this, on our above hypothesis, is precisely what we 
should have expected : for, since it is self-evident that 
the species cannot have been naturalized accidentally on 
these mountains, and since geology informs us that a 
vast interval has elapsed since the Madeiran islands were 
portions of a continuous whole, we have at once a suffi- 
cient time assured us for the modifications to be com- 
pleted, and to appear at length permanently adjusted in 
accordance with the conditions and influences which 
locally prevail. 

There are other examples which might be quoted in 
support of my theory, that isolation, when involving a 
sufficient period of time, has a direct tendency either to 

* I do not think it necessary to apologize for the apparent dis- 
posal of this qucestio vexata ; because, from the wildness of the 
upland ridges to which the D. obscuroguttatus is in Madeira ex- 
clusively confined, I deem it an absolute impossibility that it could 
ever have been introduced, through any chance agencies whatsoever. 
And hence, unless we reject the doctrine of specific centres in toto, 
I contend that it must have migrated, together with other insects 
similarly circumstanced, by ordinary means, and without natural 
impediments, from its own area of diffusion. 


diminish the stature of the insect tribes, or else to neu- 
tralize their power of flight ; but that, in the latter case, 
the creatures, when thus despoiled of a function, do, on the 
contrary (instead of deteriorating in size), often receive 
a compensation for their loss by an actual increase in 
their bulk. The common Brady cellus fulvus, Mshm, is 
another instance in point. From its occurrence in the 
almost inaccessible districts of the Madeiran group, far 
removed from cultivation, I am inclined to refer its entry 
into this southern region to that remote period when a 
connective land oifered a natural passage to wanderers 
from the north. Hence our first stipulation, that of 
sufficient time, is satisfied ; and what is the result ? The 
insect is a trifle more robust than its ordinary European 
representatives, and it is invariably apterous. The Ca- 
lathus fuscus, Fabr., is also, as is clear from its special 
attachment to the mountain tops, strictly indigenous in 
Madeira (that is to say, it must have arrived there 
during the migratory epoch) ; and the consequence is, 
that, although usually winged in our own country, it is 
permanently subapterous in that island. I think it far 
from unlikely that the Dromius negrita, Woll., may be 
the ultimate phasis (from isolation) of the common D. 
glabratus, Dufts., from which it may be distinguished 
by its somewhat larger bulk, more robust head and pro- 
thorax, and by the obsoleteness of its wings. True it is, 
that the latter species flourishes alongside it in Madeira; 
but, like the Vanessa Atalanta (when considered with 
respect to the V. Callirhoe), may it not be of more recent 


importation from the European continent, and as vet in 
a transition state? an idea which the smallness of its 
wings, as compared with those of its British analogues, 
wonld seem rather to corroborate. 

But, if this slight increase of stature would appeal- 
generally to accompany that gradual extinction of the 
powers of flight which isolation is apt to induce, it 
follows, on the other hand (as indeed I have lately 
intimated), that where wings are so essential to the con- 
tinuance of a species that they cannot, without its posi- 
tive destruction, be taken from it, the primary effect of 
isolation, namely a diminution of bulk, will for the 
most part happen instead. As this fact, however, has 
been already commented upon, we will not discuss it 

AVhy it is, in the Insecta, that islands* should pre- 
dispose to an apterous state more than continents, it is 
not easy to speculate. Mr. Darwin has indeed suggested, 
and with much apparent reason, that, were wings fully 
developed, the indiscriminate use of them might lead to 
unhappy results, by tempting the creatures to venture 
too far from their native rocks ; and that, therefore, this 
partial decay is, under such circumstances, a wise pro- 
vision in their favour : whilst it has been urged, on the 
other hand, that since insular species are at all times 
liable during heaw scales to be blown out to sea, they 

4- O l 

* I am informed by Dr. Hooker, that the only two insects (belong- 
ing respectively to the orders Coleoptera and Lepidoptera) which 
he detected iu Kerguelen's Laud were wingless. 


should in reality be gifted with stronger powers of flight 
(rather than weaker ones), to fortify them against such 
disasters ; and that, consequently, the above phenomena 
are not explicable on Mr. Darwin's hypothesis. For my 
own part,, I am inclined to accept that theory, in all its 
fullness ; and, furthermore, I do not believe that the latter 
consideration (though it unquestionably contains much 
presumptive truth) does at all interfere with the admission 
of it, seeing that either requirement may be fulfilled, 
according to the nature of the several species which are 
destined to be acted upon. Thus, iffliyht is absolutely 
indispensable, as in the greater number of the Lepido- 
ptera, and beetles of a flower-infesting tendency, we shall 
find that the wings remain unaltered (if indeed they be 
not actually increased in capacity, of which I am by no 
means certain), and that the effect of isolation is more 
particularly evident in a diminution of stature. But if, 
on the contrary, the creatures are less dependent on 
aerial progression for their sustenance, as in the pre- 
dacious tribes generally, especially those of nocturnal 
habits, the reduced area in which they are confined, in 


conjunction, it may be, with the danger to winch they 
would constantly expose themselves by the promiscuous 
employment of organs which their modes of life do not 
positively need, would seem to render the presence of 
wings unnecessary; and they are accordingly, by degrees, 
removed : in which case, however, a compensation for 
the loss is not unfrequently granted by an increase (more 
or less perceptible) in bulk. 


In the Madeiras, this diminution and enlargement of 
stature, accompanied for the most part respectively by 
the retention and annihilation of the powers of flight, is 
singularly traceable on the selfsame rocks, particularly 
the smaller ones of the group. Thus, on the Flat 
Deserta, or Ilheo Chao, the Scarites abbreviates , Koll., 
Laparocerus morio, Schon., and the Helops Vulcanus, 
WolL, attain a gigantic size ; yet it is on that very island 
that the Ptinus albopictus, WolL, finds its minimum of 
development, scarcely exceeding in dimensions some of 
the larger members of the Trichopterygia. The Deserta 
Grande has some special modifying capability of its 
own, the Eurygnathus Latreillei, Lap., Notiophilus ye- 
minatus, Dej., Zargus pellucidus, WolL, Calathus com- 
planatus, Koll., Olisthopus Maderensis t Wo)l., Caulotrupis 
conicollis, WolL, Laparocerus morio, Schon., Omias Wa- 
ter housei, WolL, Helops Vulcanus, WolL, and the EUip- 
sodes glabratus, Fab., being also larger on that rock 
than is typical : all of them, however, with the excep- 
tion of Notiophilus geminatus, are there, as elsewhere, 

Other qualifying results, from isolation, are equally 
apparent. Take colour, for instance ; and we shall per- 
ceive that in the Dromius sigma, Rossi, it is sensibly 
affected. The normal state of that insect " does not 
occur at all in Madeira proper, but only in Porto Santo. 
True it is that the modifications in the several islands 
present but slight differences inter se ; nevertheless, 
being constant, I would lay particular stress upon them, 


since they go very materially to prove that the effects of 
isolation on external insect form are even more import- 
ant, if possible, than those of latitude. That this is 
the case in the present instance, appears clear from facts 
so minute as these. For, out of the many specimens 
which have come under my observation from various 


countries of Europe, if there is one point more constant 
than another in this otherwise variable species, it is, I 
believe, under all circumstances, its immaculate pro- 
thorax. Now, whilst this (we may almost say essential) 
character obtains in Porto Santo, in Madeira it does 
not hold good : the prothorax there is invariably infus- 
cate in the centre; and on a small adjacent rock (the 
Ilheo de Fora) it is entirely dark. Nor let anyone sup- 
pose that details apparently so trivial are beneath our 
notice, or the mere result of chance, since it is by the 
observation of such-like points, and by marking their 
development according to the circumstances of the 
several localities in which they obtain, that we are alone 
able to appreciate their importance, and so to form, in a 
wider and geographical sense, a correct estimate of their 
value*." The Olisthopus Maderensis, Woll., is much 
paler, larger, and more opake, on the Dezerta Grande 
than it is in Madeira proper. So great indeed is the 
change which it has undergone through a long isolation 
on that rock, " that, had the case been a solitary one, I 
should not have hesitated in regarding the specimens 
obtained from thence as specifically distinct; neverthe- 

* Insecta Maderensia, p. 6. 


less, with the knowledge both of the modifying effects of 
isolation, and also of the kind of modification essentially 
peculiar to that island, I am perfectly satisfied that it is 
a mere local state, although a very remarkable one, and 
has no claim whatsoever to be otherwise considered*." 
The Pecteropus Maderensis, Woll., is of a greenish- 
brassy tinge in Porto Santo, and much acuminated in 
front; whereas on the Dezerta Grande it is almost 
invariably coppery, and less narrowed anteriorly. The 
Caulotrupis lucifugus, Woll., although ranging through 
no very opposite phases, either of outline or sculpture, 
" appears to possess a slight modification for every 
island of the Madeiran Group : and hence small shades 
of difference, which might otherwise be regarded as 
trifling, become directly important, and cannot be 
ignored in a local fauna, even though a general col- 
lector may deem it unnecessary to recognize them. In 
real fact, however, such distinctions, when viewed geo- 
graphically, are of the greatest interest, as serving to 
illustrate what we have so often had occasion to com- 
ment upon, namely the influence of isolation and other 
circumstances on external insect formf." The Psyl- 
liodes vehemens, Woll., is permanently paler in Porto 
Santo than it is in Madeira proper, being almost entirely 
testaceous. "That the species is identical, however, 
with the Madeiran one I have not the slightest doubt, - 
the sculpture and colour, as I conceive, having merely 
undergone a change since the remote period of its isola- 

* Insecta Maclerensia, p. 36. t Id. p. 310. 


tion on a comparatively calcareous soil*." The Scarites 
abbreviatus, Koll., occupies the loftiest peaks of nearly 
all the Madeiran islands, and was probably once abun- 
dant over the entire ancient continent, whatsoever its 
limits may have been, of which the present group forms 
but an isolated part. "There are traces of it in the 
Canaries, from whence occasional specimens have been 
brought, and which, from the want of local data and of 
sufficient numbers to reason upon, have in their turn 
been severally regarded as distinct. The fact however is, 
that the species in question is an extremely variable one, 
assuming differences of size according to the altitude at 
which it lives, and differences of sculpture according to 
the circumstances of the spot on which it is isolated. 
That such is actually the case, a careful observation of 

*/ 9 

the many minute changes which the insect has under- 
gone in the various islands and altitudes of the Madeiran 
group will, I think, prove to a demonstration. For it is 
impossible to suppose that every rock contains its own 
species, that is to say, has had a separate creation ex- 
pressly for itself, a conclusion at which we must 
assuredly arrive, if small and even constant differences 
are of necessity specific. Rejecting therefore this hypo- 
thesis as utterly untenable, and as contrary to all expe- 
rience, we are driven to acknowledge that isolation does, 
in nearly every instance, in the course of time, affect, 
more or less sensibly, external insect form ; which 
being admitted, we have at once an intelligible principle 

* Insecta Maderensia, p. 452. 


whereby to account for modifications innumerable, each 
of which, when viewed simply as a difference, indepen- 
dently of the circumstances producing it, might have 
been regarded as sufficient to erect a ' species J upon, 
had the desire for multiplying them overbalanced the 
love of truth*." 

Such are a few of the circumstances, influences, and 
conditions, by which the outward aspect of the bisect 
tribes is liable, within definite limits, to be more or less 
regulated : and it is impossible to view them with an 
unbiassed mind and not arrive at the conclusion, that 
physical agents generally have a very decided control 
over the external contour of these lower creatures. In 
selecting the examples which we have lately discussed, I 
have avoided as much as possible those startling in- 
stances of variation which distant quarters of the globe 
will readily supply, because there are vast numbers of our 
naturalists who will not acknowledge the validity of any 
evidence which would tend to amalgamate, in a broad 
sense, the species of the Old and New Worlds. I have 
therefore contented myself with such data as must fall 
within our common experience, feeling satisfied that if 
the principle be allowed in the one case, it cannot long 
be objected to in the other. There are few entomolo- 
gists who would not recognize, in the abstract, a legiti- 
mate capacity for adaptation in every insect with which 

* Insecta Maderensia, p. 11. 

they have to do : yet I believe there are not many, who, 

/ * v %J ' 

if modifications were to be shown them as the fixed 
result of disturbances from without, would be prepared 
at once practically to accept them as such. The col- 
lectors of the present day are so prone to regard every 
permanent difference as a specific one, that a large pro- 
portion of them do not sufficiently realize, that well- 
marked races, or states, are no longer matters of hypo- 
thesis, but of fact ; and that, therefore, a sensible 
amount of aberration should not only be conceded to the 
action of certain physical combinations and elements, 
but even anticipated and looked for. Such however 
ought not to be ; and earnestly therefore would I advo- 
cate a greater latitude for geographical influences than 
has been hitherto admitted by many of us. Especially 
would I urge the necessity for a more careful study of 
insular phenomena, for I am convinced that a due allow- 
ance is seldom, if ever, made for the qualifying power of 
isolation, per se, the most significant perhaps of all the 
conditions which we have attempted in the preceding 
pages to examine. 

" Felix qui potuit rerum cognoscere causas ' is a 
motto which the student of Nature should keep con- 
stantly in view ; for it is undoubtedly a more honourable 
task to discover the reasons for what we see, than the 
mere appearances themselves. He who has dived deeply 
into the everyday circumstances around him will be 
reluctant to ascribe so much as a single item of all that 
comes within his ken, to chance ; for to him the whole 


system of created things is, from first to last, replete 
with design. Natura nil agit sine causa is as true 
now as it ever was, and it will be so to the end. Let us 
not therefore be discouraged at the apparent smallness 
of the data from which many of our conclusions have to 
be drawn, for nothing is in reality trivial which is the 
effect of a wisely appointed law ; and, even were such 
the case, it would not be thereby proved that the inves- 
tigation of the law itself (however liable it may be to 
exceptions) is unimportant. Nor ought we, on the other 
hand, to be discouraged if we cannot always reconcile 
conflicting phenomena, and detect in each a primary 
controlling cause. We should rather bear in mind, that 
the elements with which we have to deal are obscure, 
and subject to permutations from which various results 
must of necessity arise; and that it is only, therefore, 
on a broad scale that we can look for uniformity of 
action, even from conditions which may appear to be 
identical. " Nature is not irregular, or without method, 
because there are some seeming deviations from the 
common rule. These are generally the effects of that 
influence which free agents, and various circumstances, 
have upon natural productions*." 

* Religion of Nature Delineated, p. 84. 




HAVING in the preceding chapter briefly alluded to 
some of the principal causes by which the outward 
aspect of the insect tribes would seem to be in a large 
measure (though within definite specific limits) regu- 
lated, it may perhaps be desirable to gather into a 
small compass, from those remarks, what the chief 
organs and characters are which appear to be more 
peculiarly beneath the control of the various influences 
which we have been just discussing. To imagine that 
when an insect has become much altered in its general 
contour, all the parts of which it is composed are 
equally affected, is contrary to experience ; since obser- 
vation warns us that there are but few actual members 
which are capable of change, whilst even the external 
features, or secondary diagnostics, are only interfered 
with according to a fixed law, the workings of which are 
necessarily modified, in proportion as the constitutions 
of the several animals are differently organized and 
acted upon. 

As regards positive structure, indeed, we can have 
but few observations to communicate, seeing that the 
limbs and appendages themselves are usually of so con- 


stant a nature, that disturbing agencies have little or no 
power to divert them from their typical states. Still, 
there are occasional facts on record, which would tend 
to prove that even these are not altogether exempt from 
the deranging force of certain contingencies from with- 
out : the number of the antennal joints, for instance, in 
the tribes where those organs are multiarticulate, is said 
to vary ; but how far this may be dependent on physical 
influences, I am not in a position to decide. The con- 
nateness of the elytra, again, is a character which we 
may at any rate define as sw#-structural ; and this I 
have myself noticed, at times, to fluctuate, according to 
the circumstances and conditions of the respective 
localities in which the particular species obtain. Such 
is eminently the case with the universal Harpalus (the 
H. vividus, Dej.) of the Madeiran Group. Speaking of 
this peculiarity, in my volume on the Coleoptera of 
those islands, I made the following remarks : " But per- 
haps its most singular character, and in which it differs 
from every other Harpalus with which I am acquainted, 
consists in the tendency of its elytra to become united 
or soldered together. I say ( the tendency/ because 
it is not always the case that they are joined (which, 
since the law exists at all, is perhaps the more remark- 
able), although in most instances, especially in localities 
much exposed and but slightly elevated above the sea- 
shore, they are. I have examples, however, from the 
upper as well as the lower regions, in which both states 
are represented ; and others again in which the elytra 


are only partially connected, being free at the apex 
though firmly attached towards the scutellum. In 
every instance, however, even where they are united 
throughout their entire length, a little force will succeed 
in separating them, showing their structure, as I have 
indicated in the diagnosis, to be sub-connate rather than 
connate. But that it does require force to effect the dis- 
junction, when they are really in the condition described, 
is proved to a demonstration to any one who has seen 
the remains of the insect beneath the slabs of stone on 
many of the small adjacent islands where it most 
abounds, or drifting about over the surface of the rocks, 
under which circumstances I have observed them in 
immense numbers, apparently the accumulation of two 
or three generations, which the violence of the elements 
had not been able to sever. It is rare in the sylvan 
districts to find them joined ; nevertheless such is some- 
times the case, thus proving that the peculiarity is not 
actually essential, but merely one which it is the ten- 
dency of the species to assume, and which is more 
developed in some specimens, and under certain condi- 
tions, than in others.* ' 

But by far the greatest amount of variability to which 
insect structure is liable, is presented by the wings, 
especially the metathoracic ones. The wings, indeed, 
unless I am much mistaken, are essentially (as compared 
with other primary details) organs of variation, capable 
of being more or less developed, according as the several 

* Insecta Maderensia, pp. 56, 67. 



countries in which the creatures are placed may necessi- 
tate their action. I will not recapitulate the evidence 
which I have already adduced, proving that islands have 
an especial capability of their own, either for increasing 
or neutralizing, as it may happen, the powers of flight 
(in which latter case, however, a compensation is usually 
made for the loss) ; but I will point to the data which 
are there brought together, in support of the hypothesis 
for which I am now pleading, believing that they will 
be found sufficient, on inquiry, to establish the doctrine 
of alary mutability, so far at least as it is connected with 
isolation as an element of control. If, however (irre- 
spectively of its cause), the thing itself be recognized, the 
principle is at once established; and we may reason 
upon it as a matter of fact. So that, if we can ensure 
this concession or acknowledgment, the occasional 
proneness to variation of these thoracic appendages is, as 
a law, admitted. The only questions which would then 
appear immediately to suggest themselves, are : Under 
what circumstances do they principally fluctuate ? and 
why should it happen that organs which are apparently 
so necessary as a medium of subsistence, should be 
subject to inconstancy ? 

Both of these have, in reality, been already replied to 
in the preceding chapter. Nevertheless, we may briefly 
repeat, that, so far as the first is concerned, it is in 
islands that we detect the maximum of instability to 
which the wings of the Insecta are liable, and that it is 
in seasons of extraordinary heat that their development 


is everywhere inclined (if at all) to be especially stimu- 
lated : whilst, as regards the second, it will be sufficient 
to state, that in continents, when any decided alteration 
takes place in the organs of flight, it for the most part 
comes to pass that an increased (rather than diminished) 
action is the result ; whereas in islands, provided that 
the species are not absolutely dependent on aerial pro- 
gression for their food (in which case, in order to 
prepare for the contingency of being blown out to sea, 
the capacity of the wings is commonly augmented), the 
reverse is nearer the truth. So that the second problem, 
the reason why appendages thus apparently essential 
should be subject to inconstancy, is at once rendered 
intelligible from the consideration, that it is only under 
circumstances in which the indiscriminate employment 
of those organs would be apt to bring the creatures into 
trouble that (when not an actual sine qua non to their 
existence) they are liable to be taken away ; whilst, even 
in that case, it generally happens that some partial equi- 
valent for the privation incurred is granted, as a recom- 

Mr. Westwood, in his admirable Introduction to the 
Modern Classification of Insects, has recorded many 
instances of alary variation ; which, however, as he does 
not appear to have noticed the peculiarity of island 
faunas, are principally in corroboration of what I have 
just insisted upon as the usual tendency in continents, 
namely, an enlargement of the erratic powers. Speak- 
ing of the Aphelocheirus cestivalis (a member of the 


Hemiptera), he observes : " My British, specimens have 
but short, rudimental, oval hemelytra, like those of the 
bed-bug ; but I possess one of Bosc's original examples, 
described by Fabricius, not quite so large as the others, 
in which the wings are fully developed. I do not, how- 
ever, on that account, regard the former either as pupae 
or distinct species, but as undeveloped specimens in the 
imago state *." And whilst discussing the Hydro- 
metrida, he expresses himself thus : ( ' It appears to me, 
that, from causes of which we are ignorant, numerous 
individuals of many of the species of these tribes are 
subjected to an inferior kind of development in the 
imago state, which does not allow the acquirement 
of wings, which, however, in certain cases, acquire 
their full size. Hence, I consider that the apterous 
specimens of Hydrometra stagnorum, those with very 
short elytra, and those with the full-sized ings and 
wing-covers, are all in the imago state, although some 
are more perfect than others t-" And, again, in his 
reflections on the Hemiptera, Mr. Westwood says (and 
most entomologists are aware of the fact) : " The species 
of GerriSj Hydrometra, and Velia are mostly found per- 
fectly apterous, though occasionally with full-sized wings. 
Chorosoma miriforme, Prostemma guttula, Pachymerus 
brevipennis, &c., are generally found with very short 
wing-covers, but sometimes with full- sized wings J." 
In like manner, the Cimex apterus, Linn, (one of the 

* Introduction to the Modern Classification of Insects, ii. p. 466. 
t Id. ii. p. 469. % Id. ii. p. 454. 


Lyg&ida) " exhibits, in an eminent degree, the ordinary 
occurrence of an imperfect perfect-state; whilst indi- 
viduals are occasionally found with fully developed organs 
of flight*"- Lyceus brevipennis, Lat., also ordinarily 
occurs with abbreviated hemelytra; but it has been 
found with them perfect by Westwood, as well as with 
metathoracic wings. 

None of the above examples however would appear to 
do more than refer to the alary instability of the Insecta, 
as a matter of fact ; but this is all for which we are now 
contending,, the preceding chapter having been in part 
devoted to some of the presumptive causes of it. Whether 
the specimens of Oncocephalus griseus, to which Spinola 
called attention, were insular ones, I cannot say ; but he 
seems to have noted an example in which an opposite 
phenomenon to those which Mr. Westwood has cited, 
was displayed, and moreover to have speculated on the 
conditions producing it, when he suggests : " L'influence 
du climat septentrional parait avoir arrete le developpe- 
ment des organes du volf." And, again, when com- 
menting upon the other tendency in a representative of 
the Reduviadce, he says (' Essai/ p. 96) : " Je pense qne 
la presence des ailes et leur developpement dependent 
du climat." Whilst treating of two British species of 
the same family, Mr. Westwood observes : " The Pro- 
stemma guttula, Fab., and Coranus subapterus, Curt., are 
interesting on account of their being generally found in 

* Introduction to the Modern Classification of Insects, ii. p. 480. 
f Essai, p. 103. 


an undeveloped imago state, the latter being either 
entirely apterous or with the fore-wings rudimental, 
although occasionally to be met with having the fore- 
wings completely developed*." The common Phos- 
phuga atrata of our own country has the organs of flight 
very rudimentary, and much too small for use : yet the 
late Mr. Holme of Oxford has mentionedf, that he has 
several times taken it on the wing, during the hot sun- 
shine. And, concerning the Olisthopus rotundatus, he 
states J that every specimen which he captured in the 
Scilly Islands was subapterous. 

But facts like these are, after all, nothing more than 
such as we may trace the counterpart of in higher ani- 
mals than the Insecta. Mr. Gould informs me, that the 
Swallows of Malta, which have but a comparatively 
narrow space to cross over, to the African continent, 
constitute (although specifically identical with them) a 
distinct race from those of England, all of which, he 
believes, winter in Morocco. But, what are the differ- 
ences displayed ? From amongst many minor ones, of 
a climatal or geographical nature, the most conspicuous 
is the length of the wings, those which have annually a 
longer journey to perform having, through a course of 
ages, acquired, as a race, a superior capacity for flight. 
And, in answer to a late query on this subject, he adds 
that all the sylvan birds in Malta, such as the Black- 
caps, Willow-wrens, Sec., though unquestionably of the 

* Introduction to the Modern Classification of Insects, ii. p. 473. 
t Trans, of the Ent. Soc. of London, ii. p. 60. J Id. ii. p. 59. 


same species as those of Great Britain, exhibit small 
local characteristics by which they may be immediately 
distinguished, such as the length of the wings, size of 
the bills, and tints of the plumage. So that the migra- 
tory birds generally, which pass to and fro between 
Europe and Africa in that particular latitude, would appear 
to form separate races from those which traverse the 
ocean to our own country; and to be, most of them, 
remarkable, inter alia, for a slight shortening of their 
organs of transit. 

If, however, the members of the insect tribes are 
capable of but small variation in actual structure, with 
the exception, in certain instances, of the greater or less 
development of the wings ; we shall find that their ex- 
ternal characters are much more prone to instability. 
There is not an item indeed of all their secondary 
diagnostics which does not admit of a positive change ; 
and, though it be only within fixed limits that the 
several modifications can occur, those boundaries are 
frequently far apart, and include at times numerous 
phases within their embrace which have been too often 
looked upon as specific. Thus, whether we regard their 
bulk, outline, colour, or sculpture, anything like absolute 
constancy, under all circumstances and conditions, does not 
so much as exist ; and we are driven to admit, that the 
physical influences to which these various creatures are 
exposed have a very decided power over their general 
configuration and aspect. It would be needless, however, 
to attempt to discuss the above details of aberration 
separately ; because, where any one of them is especially 


interfered with, it usually happens that the others are 
more or less involved with them : but we may offer a 
few desultory remarks, which will tend to show that 
disturbing agents are apt to mar them both individually 
and as a whole, and not only so, but to affect them in 
a permanent manner (as indeed has been already inti- 
mated), according as similar combinations of them are, 
from local causes (as it were), selected, to be acted 

I have stated in the last section of the preceding 
chapter that insect stature is eminently beneath the 
control of contingences from without; adducing, amongst 
other examples, in support of this, the Madeiran Ptinus 
albopictus, a species which, whilst it averages more 
than a line in length on the central island of the group, 
is reduced to less than half that bulk on a small and 
weather-beaten rock (the llheo Chao) at a distance from 
it. Judging indeed from many hundred specimens of 
the Plini which I have submitted to a close comparison, 
' ' the most constant of their characters would seem to be 
outline and sculpture, whilst size and colour are appa- 
rently the least to be depended upon : so that trifling 
differences may be of specific indication in the former 
case, where in the latter much larger ones are worth- 
less*." I have in fact generally noticed, that size and 
colour are more peculiarly liable to be affected together. 
This, however, is nothing more than what we should 
anticipate, since the same causes which have stunted the 

* Insecta Maderensia, pp. 260, 261. 


dimensions, during a long series of ages, of any par- 
ticular creature, will for the most part be found to have 
also impaired the brilliancy of its tints. Luxuriance of 
vegetation and sheltered districts are alike conducive, 
in the Annulosa, to the development both of the body 
and its adornment ; or, in other words, where the vege- 
table creation attains its maximum (which it certainly 
does not do in situations which are exposed to the irri- 
tating consequences of a perpetually stormy atmosphere), 
there the animal world will be usually observed to 

There are many insects which appear to have two 
distinct states, both in magnitude and hue, which we are 
seldom (in some instances, I believe, never) able to unite 
by intermediate links, or grades ; and yet which are 
universally admitted, although found in actually the 
self-same spots (a fact which prevents their being looked 
upon as separate, local modifications of a common type), 
to be mere varieties of each other. They are, however, 
exceptions to the general rule ; and, although infringing 
on the strict definition of a " variety," as given at a pre- 
ceding page"*, we nevertheless feel an a priori conviction 
that they are by no means specifically dissimilar inter se. 
Such phases, as regards stature, are presented by the 
Brachinus crepitans and Lamprias chlorocephalus of our 
own country ; whilst, as regards colour, the Philhydrus 
melanocephalus, Aphodius plagiatus, and the Psylliodes 
erythrocephala (constituting in its paler garb the P. ni- 

* Vide supra, p. 5. 

F 5 


gricollis, Mshm) may be quoted, as cases in point. Thus, 
also, in Madeira, the Mycetoporus pronus, Erich., has a 
large and small form, living in communion, which I 
have never been able to connect, and yet which are un- 
questionably identical (differing in no respect except in 
size) : and so have the Stenus Heeri, Woll., and the 
Saprinus nitidulus, Fab."* 

As regards the instability displayed by colour, in the 
insect tribes, when subjected to the action of certain 
conditions and influences from without, so much has 
been said in the fourth section of the preceding chapter, 

* Although, in our ignorance of their real nature, we cannot cite 
them as actually analogous to these separate phases in certain 
members of the Insecta, yet we are forcibly reminded by the latter 
of the distinct states which many of the Terrestrial Mollusca pre- 
sent (frequently in equal proportions) in the same localities. Thus, 
most of the Pupa have at least two abruptly-marked forms, a 
larger and smaller one. Many of the Helices also exhibit this ten- 
dency in an eminent degree : I have indeed been shown specimens 
by Sir Charles Lyell of the Helix hirsuta, Say, from North America, 
one state of which is considerably more than double the dimensions 
of the other ; and I believe it is a well-known fact that intermediate 
links have not yet been observed to connect the extremes. May 
not therefore the gigantic H. Lowei and Bowdichiana, which are 
now extinct in the Madeira Islands, have been but forms of the 
H. Portosanctana and punctulata, respectively, co-existent with 
them, though more sensitive to the great diminutions of altitude 
and area which were consequent on the breaking-up of a once con- 
tinuous land ? If such be the case, however, it is certain that they 
were far commoner at an early period than then* smaller colleagues 
(which, now, in their proper districts, absolutely teem), seeing 
that the latter are extremely rare in the fossil deposits, whilst they 
themselves literally abound. 


that it is unnecessary to repeat it here. True it is that 
it was then my sole province to discuss the causes which 
would appear to regulate, in a large measure, the external 
aspect of the Annulosa ; yet the existence of inconstancy, 
in the several organs and characters involved (with which 
alone we are now concerned), was, by the nature of the 
case, implied : so that if the disturbing element was de- 
monstrated, the mere fact that the thing (whatsoever it 
may have been) was interfered with, was surely proved 
a fortiori. I there pointed out the great proneness to 
a change in hue which divers circumstances are apt to 
induce; and I particularly instanced proximity to the 
sea- shore, and other saline spots, as well as an attach- 
ment to calcareous districts, as amongst the most power- 
ful of the deranging contingences. In case, however, 
that any further evidence should be looked for, on this 
immediate subject, I will quote the following, relating 
to the Bembidium Atlanticum of the Madeira Islands, 
which was but just touched upon in that chapter, as a 
concluding example of the general effect of physical 
agents on the colour of these lower creatures. " Through- 
out all the Madeiran Coleoptera there is perhaps no 
insect which displays such an extraordinary range of 
colouring as the present one does ; and although it is 
true that the section of Bembidium to which it belongs is 
essentially a variable one, yet I am not acquainted with 
any Peryphus in which the paler patches of the elytra 
are so remarkably unstable, or which appear to be so 
completely under the control of external circumstances, 


as are those of the B. Atlanticum : and indeed unless 
viewed in the mass, we should scarcely be inclined to 
recognize the same species in the many aspects which it 
puts on between its extremes. The examination, how- 
ever, of a very large number of examples, and a careful 
consideration of the several localities and altitudes in 
which they were taken, has convinced me that there is 
unquestionably but a single type of form amongst my 
entire series, since the whole are so intimately connected, 
by successive gradations both of outline and colour, that 
it is perfectly impossible to isolate even a single specimen, 
or to draw a line of specific demarcation between any 
two consecutive members of the chain. It will be per- 
ceived, by a reference to the diagnosis, that the insect in 
question passes imperceptibly from nearly a pure green, 
through a well-defined spotted state, into one which has 
the elytra almost testaceous, the paler portions being 
at last so largely developed as to become confluent, and 
almost to cover the entire surface. In Madeira proper 
the darker varieties would seem to be typical ; whereas 
in Porto Santo the brightly coloured ones preponderate, 
and in fact are all but universal. Both extremes do 
nevertheless occur in both islands, the tendency being 
merely, in either case, to assume the particular modifi- 
cation characteristic of the spot*. 

And so it is with the outline and sculpture (no less 
than with bulk and hue) : they also are equally liable to 
disturbance from physical causes, as indeed has been 

* Insecta Maderensia, p. 78. 


already insisted upon. Like most of the minutise of 
variation, however, to which we have called attention, it is 
more particularly on islands that this is to be observed, 
isolation, during an interval sufficiently long, appear- 
ing to possess some especial control over the external 
contour and surface of the insect races. Thus, in the 
Madeiras, for instance, the Caulotropis lucifugus has its 
prothorax more distinctly punctured, and its elytra more 
perceptibly striated, in the principal island, than on any 
of the smaller members of the group ; in Porto Santo, 
indeed, it is almost free from sculpture of any kind ; 
whilst its ally, the C. conicollis, apart from being some- 
what larger, is, on the contrary, both more punctured 
and striated on the Dezerta Grande than it is in Madeira 
proper. The Omias Walerhousei, again (in addition to 
its slightly increased bulk and less shining envelope, in 
that locality), is more lightly impressed on the Dezerta 
than it is in Madeira : and, not to mention other differ- 
ences, the E Hips odes glabratus is densely beset with 
most minute granules on that same rock whereas on 
the mountain slopes of the central mass, it is highly 
polished and glabrous. The Helops conferius, we have 
intimated at a previous page, is less coarsely sculptured 
in the lofty regions of Madeira, than in the lower ones : 
and the H. futilis has its elytral tubercles apparent in 
Madeira proper, but evanescent on the Dezerta Grande. 
The Eurygnathus Latreillei assumes a permanent variety 
on the Dezerta, the insect having become modified 
through a long isolation on those weather-beaten heights, 


where it not only attains a more gigantic stature than 
in Porto Santo, but is invariably also more parallel and 
opake, has the sides of its prothorax more recurved, with 
the punctures towards the lateral angles almost obsolete, 
and the strise of its elytra somewhat more evidently 

Such examples, however, might be multiplied ad infi- 
nitum ; and I will not therefore devote further space to 
the bringing together of facts which it is hardly possible 
will be disputed, especially as it has been my wish, in 
the present chapter, merely to enumerate what the organs 
and characters principally are which are more peculiarly 
sensitive to change, throughout the Annulose tribes. 
This I may venture to hope, though briefly, I have in 
part done ; and I will consequently pass on to other 
considerations, which, even if somewiiat alien to the im- 
mediate question of insect instability, should scarcely be 
altogether omitted in a treatise like this. 

* Insecta Maderensia, pp. 21, 22. 




WE frequently hear it asserted, that, since the members 
of the Insecta are so numerous and minute, when com- 
pared with those of other departments of the organic 
world, the entomologist, whose province it is to collect 
and classify them, can have but little time, if he attempt 
the real advancement of his particular science, for ge- 
neralizations on a broad scale. Now, whilst there is 
necessarily some reason in this remark (for the investiga- 
tion of species is a work of such labour and drudgery 
that it is apt to monopolize all the leisure hours which 
the greater number of us are able to command), we 
should recollect, on the other hand, that the soundest 
theorists have ever been the most patient and accurate 
observers ; and have, many of them, spent whole years 
of their lives as humble students in Nature's domain. 
We need not be afraid that an occupation amongst 
what is microscopically small is liable to cramp the 
mind, and render it unfit for wider processes of induc- 
tion, since the very opposite of this would seem to come 
nearer to the truth. The understanding which has 
been well tutored by a system of close and steady obser- 


vation, which has been trained to seize upon differences 
amongst the objects of our common experience, to 
balance the importance of generic and specific charac- 
ters, as tested in the acquisitions of our daily walks ; 
and which has been gradually brightened and matured 
by the habitual exercise of its judgment on the most 
trifling phenomena around us, has usually gained strength 
enough to form conclusions from such data, which will 
not only stand the test of analysis, but will be free from 
those eccentricities of genius which too often mar the 
speculations of less practical naturalists. The mind, 
moreover, having been chained and fettered for a season 
to the mere detail of facts, breaks forth, under such cir- 
cumstances, with all the vigour with which the contempla- 
tion of truth has gifted it, and takes its flight as it were 
to a clearer sky; and, though a reaction may at times 
set in, hurrying it away into regions beyond its sphere, 
it will assuredly return at length, fraught with the 
soberness which its vocation has inspired, and commence 
to build up its hypotheses, step by step, in harmony 
with the material which it has amassed. 

Yet though entomologists may be in reality as well 
qualified as any other natural historians for drawing 
general conclusions from the result of their researches, 
it is impossible to conceal the fact, that, as a body, they 
have not ordinarily done so. Whether this has hap- 
pened through an accidental disinclination on their part 
to occupy themselves in such matters, or (which is more 
probable) from their whole time having been engrossed 


by the dry routine of their science, I do not pretend to 
determine : be the solution, however, what it may, the 
inference is practically the same, that the Annulosa 
have not hitherto been sufficiently regarded, in the 
great questions of zoological geography. But especially 
have they been ignored during that most significant of 
considerations which has been so ably brought forward 
of late years by some of our keenest observers, namely, 
the distribution of animals, as affected by geological 
changes, on the earth's surface. 

It would be well if the collector of insects would 
devote at least a tithe of his energies to the speculative 
branch of his subject. Certain it is that much would 
probably be advanced, at first, on slender premises ; and 
w r ould, as a consequence, fall to the ground, leaving no 
record behind it. Yet such must inevitably be the case, 
at the outset, in every region of inquiry ; and we are 
prepared to expect it. It does not however follow that 
good would not be developed also ; whilst we are confi- 
dent of the fact, that unless the trial be made, it cannot 
possibly arise. No question has ever yet been mooted 
without beneficial results : it has either been shown to be 
absurd, and has received its death-blow on the spot, or 
else truth has been elicited (indirectly perhaps) , which has 
at once shed a new ray of light on some of its obscurest 
bearings. And so, assuredly, it would be in the present 
instance. We cannot doubt that there is much to be 
discovered in the past history of insect dissemination, 
which would tend, w r hen rightly interpreted, to explain 


many of the occult phenomena of the present day ; and 
we may be equally satisfied that this cannot by any 
possibility be attempted without the assistance of geo- 
logy. Let us therefore glance hastily at a few of those 
more undeniable convulsions which we are aware have, 
at various epochs, taken place ; and endeavour to catch 
a glimpse of how, in the common course of things, that 
portion of the insect world would be affected which was 
exposed to their influence. 

First and foremost, perhaps, in importance, of all the 
changes which it is self-evident have happened, may be 
mentioned subsidence. Including, as it does, both the 
general lowering of some countries, and the actual isola- 
tion of others, there are, I believe, no physical crises to 
which we could point, through the instrumentality of 
which the very existence of the insect races (not to 
allude to their diffusion) has been, by the nature of the 
case, more seriously interfered with. We know that 
there are certain species of an alpine and boreal cha- 
racter, which cannot live except in a climate of low tem- 
perature, guaranteed to them either by elevation in one 
land, or by a higher latitude in another : and let us 
picture the consequences of the gradual sinking of a 
mountain chain, even to a small extent, the summits of 
which only just afforded the conditions of atmosphere 
necessary for the continuance of creatures like these. 
Now this is an example by no means far-fetched, and 
such as must have occurred in instances innumerable. 
But, what would be the many results of a diminution in 


the level of our imaginary range ? It needs no argu- 
ment to prove, that one at least would be manifest in 
the total extinction of those forms which could not 
adapt themselves to the increased heat. Others, which 
were able with difficulty to endure the alteration, would 
in all probability, even though they had now emigrated 
to the loftiest peaks, nourish less vigorously than before ; 
and it is not unlikely, moreover, that they would become 
somewhat modified from their normal states, states 
which, be it recollected (for this is an instructive lesson), 
would still exist in more northern zones. 

During my researches in mountain tracts, I have 
usually remarked, that the highest points of land either 
teem with life, or else are perfectly barren. My own 
experience would certainly tend to prove, that, in a 
general sense, one or the other of these extremes does 
almost constantly obtain. And, although I would not wish 
to dogmatize on phenomena which may in reality be ex- 
plicable on other hypotheses, it would perhaps be worth 
while to inquire whether the geological movements of 
subsidence and elevation will not afford some clew to the 
right interpretation of them. Be this, however, as it 
may, I can answer, that in many countries, where there 
are strong indications of the former, the alpine summits 
harbour an insect population to a singular extent ; whilst 
in others, where the latter is as distinctly traceable, the 
upland ridges are comparatively untenanted. Now we 
have already shown, that where the gradual lowering of 
a region has taken place, there will be, of necessity, an 


undue accumulation of life on its loftiest pinnacles, 
for, even allowing a certain number of species (which 
even formerly were only just able to find a sufficient alti- 
tude for their development) to have perished, we shall 
have concentrated at that single elevation the residue of 
all those which have survived from the ancient elevations 
above it. But, if, on the other hand, an area, already 
peopled, be in parts greatly upheaved, there will be 
either a universal dying-out, from the cold, of a large 
proportion of its inhabitants, or else an instinctive 
striving amongst them to desert the higher grounds on 
which they have been lifted up, and to descend to their 
normal altitudes: in both cases, however, the present 
summits will display the same feature, namely, utter 

Such are a few of the effects which elevation and 
subsidence, even on a small scale, would seem (when 
tested by theory and practice) to produce. It yet 
remains for us to suggest, that the latter, when carried 
to its maximum, so as to cause the actual separation by 
the sea of one district from another, is a contingency of 
immense significance in regulating the distribution of 
the Annulose tribes. Their outward contour and aspect 
we have shown in a previous chapter to be very largely 
beneath the control of isolation, provided a sufficient 
time can be granted for the change : but their ultimate 
absence from any particular place, through the impedi- 
ment which it offers to their migratory progress, we 
have not yet touched upon. Let us conceive, therefore, 


an extensive continent ; and, since the insects which at 
present inhabit our earth must, if the doctrine of specific 
centres be true, have been originally created in certain 
definite spots, let us suppose a limited proportion of 
them to have been first produced upon this tract. Self- 
dissemination, we will assume, has been going on for 
centuries : those species which were gifted with quick 
diffusive powers have become pretty evenly dispersed 
over its surface ; whilst those of naturally slow or seden- 
tary habits have peopled, comparatively, but small areas 
around the respective localities of their birth. Such may 
have been the case, at some fixed period, amongst the 
aboriginal beings of any country which we choose to 
select as an illustration. But there is another element 
to be considered. If this region be not insular, it will 
have received colonists from foci of radiation situated 
beyond its bounds and these, therefore, according to 
their several capabilities for progression, will have, like- 
wise, in parts, overspread, or tenanted, it. Now it is 
impossible to cite a more simple example than this. 
But let us endeavour to realize what would be the neces- 
sary consequence of the breaking up of such a district as 
that which we have imagined. If a general sinking should 
take place, causing its higher points to be alone visible 
above the ocean, or merely & partial one, so as to admit of 
the sea encompassing portions of it which would remain 
unaffected in their altitude; the result practically would be 
the same, namely, the constitution of a group of islands 
out of a once continuous land. Then, as regards the 


animal population of this tract, the main phenomena are 
almost self-evident. Should any of its isolated frag- 
ments chance to contain a portion of one of those limited 
areas which a species of slow progressive powers had 
succeeded in colonizing, it would of course harbour (pro- 
vided that the other portion has disappeared) what would 
now be denned as endemic. Numbers of these small 
areas, or, in other words, of the species which had over- 
spread them, would in all probability be lost for ever ; 
whilst the occurrence of any of the surviving ones in 
more than a single island would manifestly depend on 
the proximity of the islands inter se. Those forms which 
had diffused themselves over the whole original con- 
tinent would now be found in all the detachments of the 
cluster; whilst others, which had wandered over the 
greater portion of it only, might be traceable perhaps in 
every island except a few. 

Such are the primary facts which suggest themselves, 
whilst discussing the question of isolation as regulating 
the distribution of the Annulose tribes. Its after ejfectSj 
on their external configuration and development, we 
have examined in a preceding chapter of this treatise; 
and we have also lately intimated what might be a few 
of the presumptive consequences of a subsidence (in a 
general sense), apart from the still more important 
principle of isolation. Before, however, we dismiss these 
brief and elementary reflexions on the upward and down- 
ward movements which geology testifies to have occurred, 
at various epochs, on the earth's surface, I shall per- 


haps be pardoned if I digress so far from my immediate 
subject as to trace out some of the actual results of iso- 
lation in the diffusion of the Insecta (especially recogni- 
zable in the stoppage of a former migratory progress) in 
a few of the northern Atlantic groups. I should pre- 
mise, however, that it is from the Coleoptera alone that 
I shall attempt to draw my inferences; nevertheless, 
since that order is more extensive than any of the others, 
and has moreover been closely investigated in most of 
those islands, it may possibly afford us data of sufficient 
comprehensiveness and accuracy for practical purposes. 

To commence, then, with the Madeiras and Canaries ; 
the first facts which isolation discloses to us, concerning 
the statistics of a region which was once continuous 
throughout that portion of the Atlantic, are the slowness 
and the direction of the ancient migratory movements. 
The former of these is rendered evident from the vast 
number of endemic species which are at present con- 
tained, not merely in the two groups combined, but in 
the several islands of which each of them is composed. 
True it is, that these peculiar forms are, most of them, 
apterous, and of naturally sluggish self- disseminating 
powers ; yet, still the circumstance remains, that these 
various creatures had not overrun areas of any extent 
before the land of passage was destroyed, for otherwise 
they must have occurred, now, on islands and rocks but 
slightly removed from each other, which they do not. 
The latter of the above conclusions, namely, the direction 
of the migratory current, will become apparent in the 


sequel. We may premise however, that, so far as the 
aborigines of this province are concerned, their course 
will be found, upon the whole, to have been a northerly 

As regards the slowness, and the direction, of the 
quondam migration (questions which can scarcely be 
treated apart from each other), some light may be 
thrown on the subject from considerations like the fol- 
lowing. The Canaries are the head- quarters of the 
genus Hegeter ; Teneriffe may indeed be called the land 
of Hegeters. No less than thirteen or fourteen species 
have been recorded as indigenous to those islands ; and 
there can be no reasonable doubt whatsoever that that 
ancient region (when continuous and entire) was the 
primaeval centre, or range, of that Heteromerous group. 
The Hegeters are an apterous race, and of a sedentary 
temperament ; hence, when the area (whether by general 
or partial subsidence, it signifies not) w^as broken up, it 
is not surprising that those local fragments of it should 
have become the nucleus of reception, as it were, for the 
members of that genus. Nevertheless, a few of these 
many representatives (of more discursive capabilities per- 
haps than the rest) had found their way, before the 
period of dissolution, to a considerable distance from 
their original haunts. Thus, one of them (the H. late- 
bricola, Woll.) had arrived at what now constitutes the 
rocks of the Salvages ; another (the H. elongatus, Oliv.), 
at least, if not two, had colonized the Madeiras, and is 
said (though I believe incorrectly) to have even reached 


the present coast of Portugal. This latter species is 
clearly of a more adaptive nature than its allies, inas- 
much as it has, also, naturalized itself (though this may 
be a more recent, and accidental, circumstance) on the 
opposite shores of Africa. One thing, however, is at any 
rate manifest, that the Hegeters attain their maximum 
in the Canaries, and that a few members only have been 
sent off, in a northerly, or north-easterly, direction, 
from thence. 

In like manner, the genus Tarphius is distinctively 
Madeiran. I have detected nearly twenty well-defined 
species of it in that group ; yet, out of so large a 
number, two only have occurred beyond the central 
island. Now the Tarphii are, also, wingless ; and crea- 
tures of very sluggish propensities, scarcely ever stir- 
ring from the masses of loose rotting timber which they 
so assimilate in hue, and to the under sides of which 
they affix themselves, day and night. Although difficult 
to investigate in their precise economy, it is extremely 
probable (may I not say, certain ?) that some important 
and peculiar office is assigned to them in the remote 
upland districts to which they exclusively belong : and 
there cannot be any question, to a person who has 
studied them carefully on the spot, but that the region 
which they now inhabit is the actual area of their prim- 
aeval appearance on this earth. Many kindred species 
may of course have been lost, during those gigantic 
subsidences which caused the Madeiras to be shaped 
out, and to tell their tale above the waves as ruins of an 



ancient land ; yet our existing cluster of forms could not 
have wandered far at that early period, from the Serras 
and ridges of their birth, perhaps not so far indeed 
(considering the limited bounds within which they are 
now confined, and that time should in reality have 
increased their range rather than diminished it) as they 
have succeeded in doing at the present day. Hence 
we may reasonably conclude, that Madeira proper is an 
example of what we have alluded to in a preceding page, 
namely, of the accidental retention, during a vast 
downward movement, of a nucleus of small specific areas 
of colonization, the colonizers of which had not extended 
elsewhere. But I stated, that two of the above-men- 
tioned Tarphii have occurred beyond the central mass, 
It is in Porto Santo that they make their appearance ; 
nevertheless, since one of them is apparently peculiar to 
that island, it is only the T. Lowei, Woll. (an insect of a 
different, and more active, nature than the rest) which 
has violated that local exclusiveness which would seem to 
be almost a generic character, as it were, of its allies. 
That species, however, both in its manners and aspect, 
recedes materially from the remainder. Although, like 
them, nocturnal in its habits, it is able to run with con- 
siderable velocity ; and, instead of attaching itself to the 
blocks of putrefying wood, which both fall and decay in 
situ on those elevated tracts, it hides within the -bunches 
of Evernia scopulorum and prunastri which clothe the 
trunks of living trees, and fill up the crevices of the 
weather-beaten peaks. Hence, when contrasted with 


its comrades, we can easily understand how the varied 
processes of accidental transportation would operate to 
increase the range of a creature which differs so essen- 
tially, in many respects, from them. It is indeed, not 
unfrequently, brought down, at the present day, by 
human agencies from the mountain-slopes ; for, since 
the cutting of faggots is one of the few sources of live- 
lihood to a large proportion of the poor of Funchal, 
numerous insects of subcortical and lichen -infesting 
tendencies are subject to be naturalized (provided they 
can adapt themselves to the change) in altitudes lower 
than their normal ones : so that there are many chances, 
even a priori, in favour of the T. Lowei having over- 
spread, whether by natural or artificial means, a wider 
area than its congeners. I believe that there is no such 
thing as a Tarphius in the Canarian Group : neverthe- 
less, singularly enough, a representative, which is more 
akin to the T. Lowei than to any other hitherto dis- 
covered (and which was imagined until lately to have 
been the sole exponent of the genus), namely, the 
T. gibbulus, Germ., occurs in Sicily. From which data 
we arrive at this significant fact : that, whilst Madeira 
proper is, without doubt, the original centre of the 
Tarphiiy two species (one of which is, likewise, Ma- 
deiran) are found in Porto Santo, to the north-east of it ; 
whilst a third makes its appearance in an island of the 

The genus Acalles presents a nucleus of species in the 
Canaries, moulded on a very large pattern. A closely 

G 2 


allied member, the A. Neptunus, Woll. (which may per- 
haps be in reality but an insular modification of the 
A. argillosus, Schon., from Teneriffe),has been detected 
on the rocks of the Salvages, to the north of them ; 
whilst on the Dezerta Grande, one of the most southern 
stations of the Madeirau Group, we have a third, which 
displays far more in common with the Canarian type 
than it does with that which obtains in Madeira proper ; 
-which last is gradually, in its turn, merged into the 
ordinary European form. The genus Pecteropus, Woll., 
is another instance in point. I possess three or four 
species from the Grand Canary, Fuertaventura, and 
Teneriffe ; and I believe it will be found, on inquiry, to 
attain its maximum in that cluster. Unlike the others, 
however, which we have just cited, it is powerfully 
winged ; and we should consequently expect to trace the 
evidences of its northward progression with comparative 
perspicuity. Can we therefore do so ? Yes : in Ma- 
deira proper it has two representatives, and in Porto 
Santo (to the north of it) one. And so with Xenostron- 
yylus, Woll. (which is likewise winged), we have two 
species, at least, in the Canaries ; one in the Madeiras ; 
and a third, unless I am mistaken, in Sicily. The genus 
Ditylus is shadowed forth in the Canary Islands by two 
or three singular representatives of a pallid, testaceous 
hue ; and, although the group is entirely absent in Ma- 
deira, a species (the D. fulvus, Woll.) is found on the 
' Great Piton ' of the Salvages, so nearly resembling, 
except in its smaller size, one of those from the Canaries 


that I think it far from improbable that it is a fixed 
insular state of that insect. Deucalion, also, may be 


quoted in support of this twofold hypothesis, of the 
direction, and the slowness, of the former migratory 
movements. It is an apterous genus, and of eminently 
sluggish habits ; and what is the consequence ? we have 
a very remarkable species (the D. oceanicum, Woll.) on 
one of the rocks of the Salvages, whilst another (the 
D. Desertarum, Woll.) has been isolated on the two 
southernmost islands of the Madeiran Group ; and of so 
sedentary a nature is this last, that, although physically 
unimpeded, it has not, even to this day, overrun the 
diminutive areas on which, when the surrounding region 
was submerged, it was originally saved from destruction. 
So strongly indeed was this fact impressed upon me, 
when I first detected it, that I shall perhaps be excused 
for recapitulating in extenso the few reflexions which 
then suggested themselves to my mind. " There is no 
genus, perhaps, throughout all the Madeiran Coleoptera, 
more truly indigenous than Deucalion. Confined appa- 
rently, so far as these islands are concerned, to the 
remote and almost inaccessible ridges of the two south- 
ern Dezertas, it would seem to bid defiance to the most 
enthusiastic adventurer who would scale those dangerous 
heights. Its excessive rarity, moreover, even when the 
localities are attained, must ever impart to it a peculiar 
value in the eyes of a naturalist ; whilst its anomalous 
structure and sedentary* mode of life give it an addi- 

* " When we consider indeed the apterous nature of Deucalion, 


tional interest in connexion with that ancient continent, 
of which these ocean ruins, on which for so many ages it 
has been cut off, are the undoubted witnesses. Approxi- 
mating in affinity to Parmena and Dorcadion, yet pre- 
senting a modification essentially its own, it becomes 
doubly important in a geographical point of view ; and 
it was therefore with the greater pleasure that I lately 
received a second representative, from the distant rocks 
of the Salvages, midway between Madeira and the 
Canaries. Differing widely in specific minutiae, yet 
agreeing to an identity in everything generic, they offer 
conjointly the strongest presumptive evidence to the 
quondam existence of many subsidiary links (long since 
lost, and radiating in all probability from some interme- 
diate type) during the period when the whole of these 
islands were portions, and perhaps very elevated ones, of 
a vast continuous land. * * * * * The Deucalion 
Desertarum is of the utmost rarity, the only two* speci- 

its subconnate elytra, and its attachment (at any rate in the larva 
state) to the interior of the stems of particular, local plants, or its 
retiring propensities within the crevices of rocks ; we are at once 
struck with the conviction, that, during the enormous interval of 
time which has elapsed since the mighty convulsions which rent 
asunder these regions terminated, it has probably never removed 
many yards from the weather-beaten ledges which it now inhabits." 
* Since the above was published, I have succeeded in detecting 
one more example, namely (in June 1855) on the summit of the 
Ilheo Bugio, or Southern Dezerta, within a few yards of the self- 
same spot where it was found by the Rev. R. T. Lowe in May 1850. 
Although I searched diligently on the Dezerta Grande, during my 
late campaign in the Madeira Islands, I was not able (so great is 
its raritv) to discover farther traces of it on that rock. 

/ * 


mens which I have seen having been captured (the first 
by myself, in 1849 ; and the second by the Rev. R. T. 
Lowe, in 1850) on the respective summits of the Middle 
and Southern Dezertas. So local indeed does it seem to 
be, that it, apparently, has not extended itself even over 
the Dezerta Grande (where there are no external ob- 
stacles to bar its progress) ; but retains the very position 
which in all probability constituted its original centre of 
dissemination at the remote period of time when this 
ancient continent received its allotted forms. Judging 
from the slowness with which creatures of such habits 
must necessarily, under any circumstances, be diffused,, 
it is at least unlikely that the present one could have 
circulated far, when the now submerged portions of that 
region began to give way; and hence it is not impossible 
that the Southern Dezerta, with the adjacent part (then 
united to it) of the Central one, may have embraced the 
whole area of its actual primaeval range, the remains 
of which (though they be now separated by a channel) it 
still continues to occupy, and from which, even when 
physically unimpeded, it has never roamed*." 

Although it is not my province in this volume to draw 
inferences from data which are not strictly entomologi- 
cal, I shall perhaps be pardoned for adding a few words 
on the testimony which the Land Mollusca of the 
Madeiras would seem to afford, in support of the general 
slowness of the animal migrations over that primaeval 
continent. The researches of the Rev. R/. T. Lowe, and 
* Insecta Maderensia, p. 435. 


of myself, on every rock and island of the group, have, 
it appears, so nearly exhausted the whole number of 
species which lately remained to be found, that the con- 
chological statistics are perhaps, at the present time, 
more accurate than those of any other department of the 
fauna : and, independently of the modifications which 
have been manifestly brought about, in some few instances, 
by isolation, since the periods of subsidence, it is truly 
singular to remark how every detached portion of the 
entire cluster harbours real species, which are now pecu- 
liarly its own. Thus (to select an illustration from 
amongst the most anomalous of the endemic forms), we 
have in Madeira proper, Porto Santo, and on the South- 
ern Dezerta, respectively, true representatives, in the 
Helix tiarella, coronata, and coronula, which in all 
probability still occupy the positions (or nearly so) of 
their original debut upon this earth. Considering the 
sluggish, or sedentary, nature of the Terrestrial Mollusks, 
it is extremely likely (nay, almost certain) that many 
intermediate links, radiating from the same type, were 
lost for ever, when the gigantic movements which rent 
this ancient region were in course of operation : so that, 
if such were 'in reality the case, we need not be surprised 
that one at least of this small geographical nucleus should 
have been preserved on three of the existing islands of 
the group. That these are actual species (saved alive 
from their fellows, after the wholesale destructions in 
this Atlantic province had been completed), and no 
results of insular development, is demonstrated by the 


fact that two of them (for the third has apparently 
become extinct) have not altered one iota since the fossil 
period, which,, in the opinion of Sir Charles Lyell, is 
anterior to the dissolution of the intermediate land ; 
whereas,, had they been mere modifications of each other, 
induced by the local conditions and influences to which 
they have been, through a long series of ages, severally 
exposed,, the difference between their recent contour and 
that of their fossil homologues would have been doubtless 
at once conspicuous. I gather, therefore, that like the 
Tarphii, to which we have lately drawn attention, they 
are veritable surviving members of an esoteric assemblage 
which found its birth-place on this post-miocene (?) tract. 
In a similar manner, the H. undata in Madeira pro- 
per, the H. Vulcania on the Dezertas, and the H. Porto - 
sanctana in Porto Santo, are representative species,- 
each occupying the same position, and being equally 
abundant, on their respective islands : and, although it 
may be a problem whether the second of these is not an 
insular modification of the first (or vice versa) ; yet, with 
the analogy of the three already mentioned before us, I 
am inclined a priori to view it as distinct. These, also, 
occur in a subfossil state ; and no alteration appears to 
have been brought about, by either circumstances or 
time. And so it is with numerous others (as the H. latens 
in Madeira, and the H. obtecta in Porto Santo; the 
H. squalida in Madeira, and the H. depauperata in 
Porto Santo; the H. Delphinula in Madeira, and the 
H. tectiformis in Porto Santo), widen are no less repre- 

G 5 


sentative inter se. From which, we are driven to con- 
clude ; first, that this quondam continent was densely 
stocked at the beginning with foci of radiation created 
expressly for itself* ; and, secondly, that the areas which 
these various creatures had overspread, before the land 
of passage was broken up, was extremely limited, or, 
which amounts to the same thing, that their migratory 
progress was unusually slow. 

Touching the two-fold question, of the local engage- 
ment of this Atlantic district with specific centres of 
diffusion, and the extreme slowness of their diffusive pro- 
gress, much instruction may be derived from a contem- 
plation of the conchological statistics. Porto Santo, for 
instance, is a very small island (not more than seven 
miles in length), yet the number of endemic species 
which it includes is so perfectly astounding that it may 
be appropriately termed a generic area of radiation. 

* It would seem, when viewed on a broad scale, as if particular 
districts throughout the world had been made as it were the special 
fields for the exercise of the creative force, or that, generic areas 
of radiation were part of the elementary design. Thus, Professor 
E. Forbes records his belief that most, if not indeed all, of the ter- 
restrial animals and plants now inhabiting Britain are members of 
specific centres beyond its bounds, they having migrated to it over 
a continuous land, before, during, or after the glacial epoch. Hence, 
since the greater number of them are supposed to have come from 
the central Germanic plains, we may assume that those plains were 
one of the primary areas of diffusion for a large mass of created 
beings. There is good cause for suspecting that the Pyrenean 
region may have been another; and certainly all evidence would 
tend to prove that this vast Atlantic province was, also, well stocked 

with aboriginal forms. 


Nor does this primaeval excess of its aboriginal beings 
strike us more forcibly than does the utter quiescence 
(if I may so express it) which has been going on amongst 
them since the remote era of their birth. Although a 
few have apparently died out* since that epoch, conse- 
quent perhaps on the change of level and diminished 
range which took place during the process of subsidence ; 
we are amazed to find that certain species which are now 
limited to particular spots (even whilst unopposed by 
physical barriers) have been absolutely peculiar to them 

* Assuming the Helix Lowei and Bowdichiana to be gigantic 
phases of the H. Portosanctana and punctulata, respectively ; four 
only, namely H.fluctuosa and lapicida, Achatina Eulina, and Cyclo- 
stoma lucidum (the first three of which are extinct throughout the 
entire group), seem to have altogether disappeared. Nevertheless, 
the gradual dying-out, as it were, of species, both here and in 
Madeira proper, is singularly evident. Thus, in the latter, the Cani- 
cal beds show the H. tiarella to have been once most abundant (it 
literally teems in those calcareous formations). Yet so rare is it in 
a recent state, that, until the summer of 1855, when it was detected 
by myself and the Rev. R. T. Lowe in two remote spots along the 
perpendicular cliffs of the northern coast, it was supposed to have 
been lost for ages. And the same may be said of its counterpart, 
the H. coronata, in Porto Santo, which, likewise, swarms in every 
fossil-bed of that island ; but which was, also, until I met with it, 
on the 15th of December 1848, adhering to slabs of stone at a con- 
siderable depth beneath the ground, on the extreme eastern peak 
(opposite to the Ilheo de Cima), imagined to have long passed 
away. And so, reasoning from analogy, I think it far from impro- 
bable that the third representative of this little geographical assem- 
blage, the H. coronula of the Bugio (which has hitherto only 
occurred in the mud deposits on the summit of that rock), may be 
still alive, though perhaps in very small numbers, on some of the 
inaccessible ridges of those dangerous heights. 


from the first, or, in other words, that, whilst the fossil 
deposits extend throughout the lower regions of the 
island, far and wide, it is only in those respective por- 
tions of the beds which join on to the present ' ' habitats ' 
that the fossil homologues of several of the species are 
to be met with. The H. Wollastoni is eminently a case 
in point. That most interesting of the Madeiran Mol- 
lusks was first detected by myself on the southern ascent 
of the Pico de Conseilho, of Porto Santo, April 22, 1849 ; 
and the subsequent explorations of the Rev. R. T. Lowe, 
in conjunction with my own, have, I think, satisfactorily 
proved that it occurs nowhere else except upon that 
single slope. Throughout the large expanse of calcare- 
ous incrustations which are spread over the island else- 
where, and on the adjoining Ilheo de Baixo, all of which 
teem with shells, I think I may assert, without fear of 
contradiction, that the H. Wollastoni does not so much 
as exist. Yet at the Zimbral d'Areia, which the Pico de 
Conseilho directly overhangs, a rich tract for these 
fossil remains, as well as in the muddy composition of 
a cliff near at hand, it literally abounds. 

In like manner, we might recall many others which 
are peculiar, recent and fossil, to the self-same precincts. 
Such, for example, are the H. calculus and commiscta, 
which swarm on the summit of the Ilheo de Baixo, in 
both states. The H. attrita, again, is the Pico d'Anna 
Ferreira modification of the H. polymorpha ; and it is 
only in the beds towards the base of that mountain that 
its fossil homologue is found. But what do these facts 


indicate ? Surely they tell us plainly of what we have 
already so often insisted upon, namely, the redun- 
dancy of this once continuous land with specific foci of 
its own, and the sluggish or sedentary nature of those 
primaeval radiating forms. 

We must not however omit to notice, that some few 
of these endemic Helices appear to have been gifted (as 
we should a priori anticipate) with more rapid capabi- 
lities for diffusion than the rest. Thus, the H. erubescens 
and paupercula seem not only to have colonized the 
entire province of which the Madeiras are detached frag- 
ments, but to have even found their way to that distant 
portion of it which now constitutes the Azores. The 
H. polymorpha has also penetrated the Madeiran region 
throughout ; and being, like the H. erubescens, peculiarly 
sensitive to the action of external influences, we per- 
ceive, in consequence, that almost every island and rock 
has now its own especial phasis of it. So greatly indeed 
is that species beneath the control of local circum- 
stances, that the very districts of an island as insignifi- 
cant as Porto Santo have each their separate races to 
boast of. On the Pico d'Anna Ferreira it assumes a 
form to which the name of H. attrita has been applied ; 
when on the Ilheo de Baixo, it is the H. papilio ; at the 
Zimbra d'Areia, on the Pico de Conseilho, and in the 
Ribeira da Coxinha, it is the H. pulvinata-, and, in 
many other situations widely removed inter se, it puts 
on the shape (variable, both in size and hue) to which 
the title of H. discina has been given. But, if we leave 


Porto Santo, and follow this Protean Helix into the 
other divisions of the group ; we meet with it on the 
Dezertas as the H. senilis (those moreover from the 
central island having a much more open umbilicus than 
is the case in the northern and southern ones), whilst in 
Madeira proper it constitutes the H. lincta (with an 
additional pale variety for the calcareous district of 
Carnal), and the H. saccharata, from the Sao Lou- 
ren9O promontory. 

In the same may we might pursue the H. erubescens, 
and show that in the sylvan regions, and on the low 
barren Ponta Sao Louren9o of Madeira, on the Pico 
de Facho of Porto Santo, on the Ilheo Chao, on 
the Central Dezerta, and on the Bugio (where it at- 
tains a gigantic size), it has its distinct and permanent 
phases, the evident results of isolation, and other topo- 
graphical influences, since the subsidence of the inter- 
vening tracts. And in like manner, the Clausilia delto- 
stoma is universal throughout the Madeiran Archipelago, 
-displaying, however, in Porto Santo a fixed and 
strongly ribbed state, peculiar to that island. Thus, if 
the examples which we previously cited tend to establish 
the extreme slowness of the migratory movements of 
the terrestrial mollusca across this former continent, 
the present ones (which refer to a few exceptional 
species of quicker self-diffusive powers) will show, no less 
than the insects to which I have lately called attention, 
that where sufficient areas had been overspread (before 
the periods of subsidence) for the creatures to have 


reached what now constitute the various islands of the 
cluster, we at once detect traces of this fact, through 
their more or less altered aspects, the result of isola- 
tion, and diminished range, during the enormous in- 
terval which has elapsed since the successive* convulsions 
which caused the partial destruction of this Atlantic 
province were brought to a close. 

To return, however, to the insects, after this long con- 
chological digression, I need not multiply evidence, in 
corroboration of my theory. Enough has been said to 
render intelligible the idea which I wished to convey, 
concerning the general direction of the migratory current 
over that ancient tract, and the extreme slowness of its 
progress, the former of which I consider probable 
from the north-easterly course in which creatures generi- 
cally identical were, if we may so express it, " given- 
off -" whilst the circumstance of their being for the 
most part specifically dissimilar (or, in other words, of 
the islands harbouring, many of them, species which 
are endemic) would seem as it were to establish the 

We must not however forget, that it is only to the 
aborigines of this quondam land that the above specula- 
tions apply. Assuming the region not to have been 
insular, that is to say, to have been connected, on its 
outer limits, with a European, or Mediterranean, conti- 
nent ; it would necessarily follow, that a certain number 
of colonists must have found their way over its area, 
and moreover in an opposite direction to the living 


stream (if we may so call it) which had been long flow- 
ing in a north-easterly course across its surface. What- 
ever be the length of the periods, however, during which 
these counter migrations were going on, I think it 
sufficient to state that I would refer them to epochs 
altogether different, so that, accompanied as they may 
have been by special geological phenomena, which, if 
known, would in all probability become at once explana- 
tory, we should be the less inclined to regard as absurd 
what might appear at first sight difficult to understand. 
In the case of the British Isles indeed, no less than five 
of these distinct migratory eras have been assumed, and 
specified*, by Professor Edward Forbes; therefore (what- 
ever value be attached to his able and interesting theory) 
I do not consider it necessary to apologize for requiring 
at least two in behalf of this ancient Atlantic province. 
Not to insist upon those of his faunas and floras which 
are of a less evident, or more questionable, character, 
he has at any rate proved, I think, almost to a demon- 
stration, the westward progress of the great mass of our 
British animals and plants, over a then unbroken land 
(the upheaved bed of the glacial sea), from the central 
Germanic plains; whilst the accurate calculations of 
the late Mr. Thompson of Belfast, concerning the reptile 
statistics of Ireland, England, and Belgium, respectively, 
have succeeded in showing, with much presumptive rea- 
son, how the formation of St. George' s Channel, before 

* Origin of the Fauna and Flora of the British Isles (in Mem. of 
the Geol. Survey of Great Britain, vol. i. p. 336, A.D. 1846). 


that of the German Ocean, interrupted the march of 
these wanderers to the far West, and debarred an im- 
mense proportion of them from an entry into Ireland, 
which would otherwise have colonized that country 
equally with our own. 

As regards Professor Forbes' s views of the creation of 
a vast continent (reaching far into the Atlantic *) at the 
close of the miocene epoch, through the upheaved bed 
of a shallow miocene sea, a region moreover of such an 
extent as to have connected the various island groups 
between the Fucus bank and the shores of the Old 
World, not only with each other, but with a Mediterra- 
nean province, Asturias, and even the south-west of 
Ireland, I must be content to pass them by, hazarding 
only a few crude and desultory remarks. So large a 
question, indeed, cannot be safely handled without 
a corresponding amount of data, in all departments of 
natural science, to reason from, which I do not possess : 
still, if a speculation from entomological premises, per 
se, be not altogether worthless, I w r ould point to the 
conclusions (lately adverted to) which my Madeiran 
researches have forced upon me, concerning the direc- 
tion of the former insect migrations, inferences which 
are, from first to last, of necessity erroneous, if the 
requisite medium for transit (into South-European lati- 

* " My own belief," says Professor Forbes, " is, that the great 
belt of gulf-weed, ranging between the 15th and 45th degrees of 
north latitude, and constant in its place, marks the position of the 
coast-line of that ancient land." 


tudes, at all events) be a mere conjecture or romance. 
Such a notion, however, I would not for a moment 
entertain, for there is too much direct evidence in 
support of distinct epochs of diffusion, to allow of any 
hypothesis, when endeavouring to account for the 
phenomena which we now behold, to supersede the 
assumption of a once continuous tract. No matter if 
we be compelled to suppose, whilst attempting to in- 
terpret what we see, that the disseminating current has 
flowed in exactly opposite courses, at different and 
remote periods, over the surface of that ancient land, 
seeing that the fact (if such in reality it be) remains 
untouched, that the land itself is at any rate there. I 
am not, however, prepared to assert that the opinion at 
which I had independently arrived, from the insect 
statistics, does positively require a northerly prolonga- 
tion of that area beyond the line of the central Mediter- 
ranean districts ; yet, after making every possible allow- 
ance for accidental introductions since the subsidences 
have taken place, there is still left a large residuum 
which I am convinced can never be explained (unless 
the doctrine of specific centres be a myth) except 
through the means of ordinary and regular migration 
over an unbroken continent. Nevertheless, though I 
would not presume, from insufficient material, to insist 
upon an extension of this Atlantic region into higher 
latitudes than those which I have just referred to, I 
must express my individual belief that, the more the 
subject is examined, with reference to the distribution of 


the Annulosa, the less will Professor Forbes' s idea suffer 
from the inquiry. In the ' Insecta Maderensia/ I have 
already thrown out a few scattered hints which bear on 
this immediate consideration ; and, since no subsequent 
reason has induced me either to withdraw or modify 
them (but rather the reverse), I will select the following, 
extracted from my preface to that work. 

"Taking a cursory view of the Coleoptera here 
described, the fauna may perhaps be pronounced as 
having a greater affinity with that of Sicily than of any 
other country which has been hitherto properly investi- 
gated. Apart from the large number of our genera 
(and even species) which are diffused over more or less 
of the entire Mediterranean basin, this is especially 
evinced in some of the most characteristic forms, such 
as Apotomus, XenostrongyluSj Tarphius, Cholovocera, 
Holoparamecus, Berginus, Litargus, Tlior ictus, and Boro- 
morphus. There is, moreover, strange though it may 
appear to be, some slight (though decided) collective 
assimilation with what we observe in the south-western 
extremity of our own country and of Ireland, nearly 
all the species which are common to Madeira and the 
British Isles being found in those particular regions; 
whilst one point of coincidence at any rate, and of a 
very remarkable nature, has been fully discussed under 
Mesites. Whether or not this partial parallelism may 
be employed to further Professor E. Forbes' s theory of 
the quondam approximation, by means of a continuous 
land, of the Kerry and Gallician hills, and of a huge 


miocene continent extending beyond the Azores, and 
including all these Atlantic clusters within its embrace, 
I will not venture to suggest : nevertheless, it is impos- 
sible to deny that, so far as the Madeiras betoken, 
everything would go to favour this grand and compre- 
hensive idea. Partaking in the main of a Mediterranean 
fauna, the northern tendency of which is in the evident 
direction of the south-western portions of England and 
Ireland, and with a profusion of endemic modifications 
of its own (bearing witness to the engorgement of this 
ancient tract with centres of radiation created expressly 
for itself), whilst geology proclaims the fact that subsi- 
dences on a stupendous scale have taken place, by 
which means the ocean's groups were constituted; we 
seem to trace out on every side records of the past, and 
to catch the glimpses, as it were, of a veritable Atlantis 
from beneath the waves of time *" 

* Although, for want of a better name, it may be admissible, 
when speaking either figuratively or poetically, to allude to this 
former region (as I have done in the above quotation) under the 
title of "Atlantis;" yet it seems incredible that certain writers 
(assuming its quondam existence) should have recently referred to 
it seriously as the possible " Atlantis of the ancients \ ' : Consider- 
ing that there is good reason to believe that all these islands were 
islands in a miocene sea, and that, if (through a general elevation) 
they were subsequently connected, the land of passage was broken 
up long anterior to the appearance of man upon the earth, " the 
ancients" must have assuredly merited their appellation, if they 
could have thrown any light on a problem which belongs to an 
epoch thus remote. Whether the " Atlantis " had any being at all 
except in the imagination of the Latin poets, or whether (as Lord 


The Mesites Maderensis, Woll., to which I alluded in 
the above quotation, is undoubtedly a strong case in 
point. Although specifically dissimilar from the M. 
Tardii, its Irish counterpart, it nevertheless approaches 
it so closely, that it might be literally mistaken, primd 
facie, for that insect ; and we know that it is one of the 
plans on which Nature com monl y proceeds, that species 
which are not merely representative of (or analogous to) 
each other, but which are actual homologues, or allies, 
should usually emanate at first from foci not far removed 
inter se ; or, at all events, if distant, connected by an 
intervening land : in other words, that generic areas, 
no less than specific centres, of radiation, form a sub- 
stantial item of the comprehensive scheme on which the 
system of created things was originally planned. We 
detect traces of this primary law in each division, or 
class, of the organic world ; nor is its reality as a law 
interfered with, through the occasional exceptions which 
are liable, as in every other instance, to present them- 
selves. Such deviations are often easily to be accounted 
for, whether by natural or artificial means ; and do not 

Bacon has suggested) it was the New World, will probably never 
now be known ; yet the fact that the Insulce Fortunate of Juba are 
almost universally identified with the present Canarian Group (as 
indeed the accurate description of Pliny well nigh demonstrates), 
and the Purpurarice with the Madeiras, ought at once, apart from 
geological evidence, to point out the absurdity of the hypothesis, 
that an Atlantic continent, in the very position which those islands 
occupy, could have been acknowledged to have any existence by the 
literature of either Rome or Greece. 


affect the subject, as a whole. Sometimes indeed they 
become at once intelligible from the historical records 
connected with them, proving that human agencies have 
been at work acting as transporting media, within a 
period comparatively recent ; whilst at others, the fact 
of the creature having been endowed with self- diffusive 
powers to an extravagant degree may succeed equally in 
rendering the phenomena explicable. But, even where 
neither of these solutions would seem to suffice, we 
should still recollect that it is only in the mass that such 
questions can be pronounced upon ; and that, con- 
sequently, where we are able to discover a rule which is 
for the most part adhered to, it is more philosophical to 
conclude that the departures from it are the result of 
special disturbing causes (whatsoever they may have 
been), than to permit them to undermine our faith in 
what would be otherwise universally true. Thus, the 
botanist tells us of Ixias, Stapelias, Mesembrianthe- 
mums, Pelargoniums, and Euphorbias, as concentrated 
in Southern Africa ; of Magnolias in Central America ; 
of Calceolarias on the Andes; of Myrtles, Banksias, 
Mimosas, and Eucalypti, in Australia ; and of the 
Bread-fruit Trees in the South Sea Islands : the orni- 
thologist points, inter alia, to the Toucons and Hum- 
ming-Birds from South America and the West Indies ; 
whilst the student of the higher animals informs us of 
the Kangaroos (indeed of the whole of the subclass 
Marsupialia, except the genus Didelphys) as peculiar to 
Australia and a few islands to the north of it ; of Lemur 


proper to Madagascar ; of the Sloths, Armadillos, Tree 
Porcupines, and of Alligators, and of the Platyrrhini 
(amongst the Monkeys), to South America; and of the 
Ourangs to the islands of the Indian Archipelago. 

And so it is with the Insecta; many of the larger 
groups of which (as Amycterus and Paropsis, in Australia; 
Pachyrhynchus and Apocyrtus, in the Philippine Islands ; 
Hipporhinus, Monochelus, Diclielus, and Moluris, in 
Southern Africa ; Macronota, in Java ; and Naupactus, 
Hypsonotus, Centrinus, Platyomus, and Cyrtonota, in 
South America) are confined to countries of propor- 
tionate magnitude, whilst the smaller ones are more com- 
monly (as it were) shaped out for special provinces or re- 
gions, according as local circumstances may require pri- 
mary adaptations to harmonize with them. Thus, whilst we 
frequently find an extensive genus diffused over the greater 
portion of the known world, we perceive that even its 
structural characteristics are not uniform throughout, but 
afford fixed geographical modifications (not, in this case, 
however, the effect of development), which have often, 
in their turn, obtained the name of ' genera/ and have 
been described as such. Whether genera, however, or 
not, they are undeniably small topographical assemblages, 
satellites around their central types; and they may 
therefore be safely regarded as genera, if we choose to 
view them in that light. Of such a nature I have 
already pointed out* is Saprinus, as compared with 
Hister ; Atlantis with Laparocerus ; and Oxyomus with 

* Insecta Maderensia, p. 214. 


Aphodius; and,, I might also add,, Mesites with Cos- 
sonus. I believe indeed that Mesites will be found to 
attain its maximum on the Pyrenees (I already possess 
two or three species, in abundance, from that region) ; 
and, if such should be the case, we shall be able to ap- 
preciate the significance of two representatives so closely 
allied as the M. Tardii and Maderensis, one of which 
has been given off in the direction of Ireland, and the 
other of the Madeiran Archipelago. 

But I will not digress further on the subject of this 
Atlantic province; since, however much I may indivi- 
dually regard it as a reality of the past (which the 
Coleopterous statistics have compelled me to do), it must 
of necessity remain, as heretofore, a matter of much 
controversy and doubt. I should indeed apologize for 
having trespassed on the reader's attention, in wandering 
thus far from the immediate results of subsidences, 
which I proposed, at the outset of this chapter, to exa- 
mine, with reference to the impeded diffusion of the 
Annulose races. Nevertheless, concluding that a prac- 
tical illustration of the effects of one of those great 
downward movements to which geology so repeatedly 
bears witness would not be irrelevant to the assumed 
consequences which I had previously ventured to define, 
I have acted on that judgment; and, having finished 
my task, will now proceed to notice, briefly, a few other 
considerations which should not be omitted, when 
inquiring into insect distribution as influenced by geolo- 
gical phenomena. 


Next in importance, perhaps, to the elevations and 
sinkings (traces of one or the other of which are more or 
less manifest in almost every region of the world), 
natural barriers may be cited, as presenting, not un- 
frequently, insurmountable obstacles to the self-dissemi- 
nation of the insect tribes. By natural barriers, how- 
ever, I would be understood to imply natural primary 
barriers, or, in other words, such as have continued as 
barriers ever since the present animals and plants came 
into existence upon the earth. For, the ocean (by way 
of illustration) is a natural barrier ; and yet it is not 
necessarily a primary one, as may be readily gathered 
from the above remarks, in which the results of subsi- 
dences are discussed, subsidences which have had the 
effect of letting it in over portions of an already tenanted, 
and unbroken, continent. Mountain- chains, also, are 
barriers ; but it may happen that they have not been so 
from the beginning, as in instances, for example, where 
they have been gradually upraised during periods geolo- 
gically recent. But both sea and alpine ranges are 
barriers, when (as usually happens) they have remained 
as such since the creation of the several species which 
now inhabit our globe. Mr. Darwin has acknowledged 
this distinction, whilst commenting upon the marked 
divergence of the faunas on the eastern and western 
slopes of the Cordillera. " This fact," says he, " is in 
perfect accordance with the geological histoiy of the 
Andes; for these mountains have existed as a great 
barrier since the present races of animals have appeared ; 



and therefore, unless we suppose the same species to 
have been created in two different places, we ought not 
to expect any closer similarity between the organic 
beings on the opposite sides of the Andes, than on the 
opposite shores of the ocean. In both cases, we must 
leave out of the question those kinds which have been 
able to cross the barrier, whether of solid rock or salt- 

Conceding, therefore, this distinction between barriers 
of a primaeval and more recent character, it is not diffi- 
cult to understand why the opposite sides of an alpine 
chain, as well as countries separated by the sea, should 
display different phenomena from each other. On the 
contrary indeed, if we could feel satisfied that no means 
of accidental transportation had operated to take them 
there, and that the animals themselves were incapable of 
enduring great diversities of temperature, and other con- 
tingencies ; we should be startled to discover creatures 
specifically identical in such regions, so long at least as 
the doctrine of unique centres of radiation formed part 
of our zoological creed. We must not, however, be too 
hasty in questioning (if I may be pardoned for the com- 
pletion of a metaphor of which I thoroughly disapprove) 
this article of our faith, through the occurrence of simi- 
lar beings in areas between which there exist barriers, 
both primary and well-defined; for the methods of 
diffusion are so complicated and numerous, that, even 
where human agency (that most important of elements) 

: Journal of Researches, pp. 326, 327. 


is not concerned, what at first sight may frequently 
appear to be impossible becomes clear enough when 
more critically inquired into. Some species, we know, 
are gifted with greater powers for horizontal and vertical 
progression than their comrades, and can (though they 
are doubtless exceptions to the general rule) pass through 
extremes of atmosphere sufficient to render even lofty 
mountain summits no obstacles to them. Others, as the 
Calosoma Syncophanta of Europe, have been stated to 
traverse the ocean unhurt* ; and I believe that many do 
at times accidentally arrive, in a half-drowned state, 
especially after boisterous weather, across channels of 
considerable breadth. Mr. Kirby, on examining the 
marine rejectamenta, during one of these apparent oc- 
currences, along the Suffolk coast, writes as follows : 
" Whether the insects I observed upon the beach, wetted 
by the waves, had flown from our own shores, and, fall- 
ing into the water, had been brought back by the tide ; 
or whether they had succeeded in the attempt to pass 
from the continent to us, by flying as far as they could, 

* Many of the Calosomata would appear to possess this power 
of crossing, either by flight or by abandoning themselves to the 
waves (though more probably by the assistance of both), even ma- 
rine barriers with impunity. Numerous instances are on record to 
this effect ; and I am informed by Mr. Darwin that a Calosoma flew 
on board the ' Beagle,' off the Bay of San Bias, in South America, 
whilst they were ten miles from shore. It seems likely, therefore, 
that the occasional occurrence of the C. Syncophanta in our own 
country, along the southern and eastern coasts, is due to this generic 
capability, and consequently (as indeed it is usually acknowledged 
to be), the result of accident. 



and then falling had been brought by the waves, cannot 
certainly be ascertained; but Kalm's observation in- 
clines me to the latter opinion*." And Sir Charles 
Lyell remarks : " Exotic beetles are sometimes thrown 
on our shore, which revive after being drenched in salt 
waterf." Nor should we forget that chance agencies of 
every description, which we are too apt to overlook, are 
daily at work (and have been so since, at any rate, the 
last creative epoch) to transport these variously organized 
beings beyond their original spheres. Sometimes they 
are carried on, or within, the bodies of larger animals, 
which is especially the case with the parasitic tribes ; at 
others on floating trunks of trees, and casual substances 
of divers kinds, which are able to resist for a definite 
period the destructive action of an element saturated 
with salt. Unwilling victims, again, are ever and anon 
hurried to comparatively distant lands by the very 
winds that blow ; and not only to distant lands, but 
over altitudes in which the severity of the cold would 
quickly annihilate them, were they (as perhaps usually 
happens) to be deposited there on their headlong and 
compulsory course. " As almost all insects are wingedj/' 
says Sir Charles Lyell, " they can readily spread them- 
selves wherever their progress is not opposed by un- 

Introduction to Entomology, ii. p. 13. 

f Principles of Geology, 9th ed. p. 657. 

J Although this is true on a broad scale, a reference to my ob- 
servations in a preceding chapter will show, that in some countries, 
especially islands, the reverse will frequently be found to obtain. 


congenial climates, or by seas, mountains, and other 
physical impediments ; and these barriers they can some- 
times surmount by abandoning themselves to violent 
gales, which may in a few hours carry them to very con- 
siderable distances. On the Andes some sphinxes and 
flies have been observed by Humboldt, at the height of 
19,180 feet above the sea, and which appeared to him to 
have been involuntarily carried into those regions by 
ascending currents of air*." With respect to the acci- 
dental conveyance of numerous species across the sea, it 
is not to the winds alone that we must look for an ex- 
planation. Large and rapid rivers are liable to inun- 
date their banks and bring down insects in prodigious 
masses, which are disgorged into the ocean, and car- 
ried to a distance from the coast, in proportion to the 
violence of the ejecting stream. When the body of 
water is considerable, the sea becomes diluted to an un- 
usual extent ; and creatures which must have otherwise 
perished, from the action of the salt, are able to survive 
for a time, and may be deposited, by means of rapid 
currents into which they are borne, on neighbouring 
islands and continents. Even the Hydradephaga are 
thus occasionally transported ; for Darwin mentions 
having captured a Cohjmbetes off Cape S ta Maria (to the 
north of the Kio de la Plata), when forty-five miles 
from the shore. And, in his ' Journal of Researches/ 
he records the following remarkable facts, which bear 
upon this immediate question. " On another occasion, 
* Principles of Geology, p. 656. 


when seventeen miles off Cape Corrientes, I had a net 
overboard to catch pelagic animals. Upon drawing it 
up, to my surprise I found a considerable number of 
beetles in it, and, although in the open sea, they did not 
appear much injured by the salt water. I lost some of 
the specimens ; but those which I preserved belonged to 
the genera Colymbetes, Hydroporus, Hydrobius, Nota- 
phus, CynucuSj Adimonia, and Scarabteus. At first I 
thought that these insects had been blown from the 
shore ; but upon reflecting that, out of the eight species, 
four were aquatic (and two partly so) in their habits, it 
appeared to me most probable that they were floated 
into the sea by a small stream which drains a lake near 
Cape Corrientes. On any supposition, it is an inter- 
esting circumstance to find live insects swimming in the 
open ocean seventeen miles from the nearest point of 

Accidental means of dissemination, such as those to 
which I have just alluded, and others to which we might 
appeal, will generally account, and with much presump- 
tive truth, for the many exceptional cases which present 
themselves, during our investigation into the effects of 
natural barriers, as visible in the distribution of the 
Annulose races, on the earth's surface. I say " excep- 
tional cases," because any one who has laboured practi- 
cally in mountain tracts cannot have failed to recog- 
nize the marked difference which is often displayed by 
the insect population on opposite sides of some alpine 
* Journal of Researches, p. 159. 


chain ; whilst he whose lot has been cast amidst island 
groups, will have become even more conscious than the 
former of the permanency of those impediments which 
have been placed (in this instance by the broad arms of 
the mighty ocean) as checks upon a too rapid system of 

But if the sea and mountain ranges, when of a suffi- 
cient age in situ, are amongst the most effectual of 
Nature's barriers against the self-dispersion of the 
animate tribes ; it follows that, if the two could be (as 
it were) united, we should Have found the greatest ob- 
stacle which physical conditions can ordinarily present 
against the wandering capabilities of the latter. The 
question therefore arises, Is it possible for them to be 
so joined ? Undoubtedly it is : and hence we arrive at 
the conclusion, that a mountain island should afford us 
the minimum of size, as regards the areas its species 
have overspread, which any country is able to furnish. 

Madeira is a mountain island, its highest peaks 
rising, although resting on so small a base, to an alti- 
tude of more than 6000 feet. Yet it is only partially a 
case in point; for, although it was a mountain mass, 
and perhaps a very elevated one, when its endemic 
beings made their first appearance upon its surface, we 
have already intimated that it has become isolated since 
that epoch : so that, whilst one of the natural barriers 
against dispersion which it involves (namely, mountain 
ridges) may be considered as primary ; the other (to wit, 
the sea, as it now obtains) has played, as an agent of 


obstruction, but a secondary part. Still, there is good 
reason to believe that the ancient tract of which it is a 
portion was broken up at a comparatively early date 
after the creation of those peculiar organic forms which 
found their birthplace within its bounds ; and that, con- 
sequently, the latter could not have wandered far (if we 
except those species on w r hich unusual powers of diffu- 
sion were bestowed) when the land of passage began to 
give way. Hence, even the sea, in this particular in- 
stance, partakes almost of the character (no less than 
the mountain heights) of an original impediment ; and 
Madeira therefore may be safely quoted as an example 
in which two barriers, of a primary nature, are united ; 
and where, consequently, we may anticipate those ultra 
phenomena of areal limitation upon which we have 
been just commenting. 

But let us now inquire, whether the hypothesis at 
which w T e have arrived will stand the test of experience ; 
for unless it will do so, we might have been spared the 
labour of propounding it. Madeira is a country com- 
posed of narrow mountain ridges, which radiate from 
central crests, and form the lateral boundaries of deep 
and precipitous ravines. Modifications of this structural 
type are of course traceable everywhere ; the upland 
tracts are often undulating and broad, and the buttresses 
which slope towards the sea are sometimes expansive 
and irregular : yet upon the whole the above description 
is correct, and we may accept it in a generic sense. 
Now we may premise that, even to this day, it is an 


island of floods ; therefore, how much more must it 
have been so when its primaeval forests, in all their 
splendour, caused an amount of exhalation and moisture 
of which at present we can have but a remote conception ! 
Hence, it is hardly to be imagined, that (however limited 
may have been the naturally acquired areas of those of 
its inmates which are most sluggish and sedentary) a 
fusion would not have taken place, in the course of ages, 
so as to render its modern fauna, in a large measure, 
homogeneous throughout. Yet, in spite of this esoteric 
tendency, it is surprising how little amalgamation has 
been effected amongst the tenants of its several districts. 
Scarcely a gorge or woodland serra exists within its 
bounds which does not harbour some species essentially 
its own; and in many instances the ranges of these 
creatures are so local or confined, that they might 
be easily overlooked even in their respective neighbour- 
hoods. It is certain, however, that the floods (which 
happen periodically) have done considerable work in 
naturalizing many of the subalpine forms, which could 
adapt themselves to the climatal change, in altitudes 
below their normal ones : and, in the north of the 
island, where the temperature is cooler than on the 
opposite side, and where the lofty defiles terminate, even 
at their lowest outlets, in abrupt precipices along the 
coast, so that the rejectamenta during the annual rains 
are brought into direct contact with the shore, this 
gradual process of deportation is particularly evident, 
a circumstance to which I have already alluded else- 

H 5 


where *. But, after making due allowance for these 
powerful means of dissemination (which,, in the common 
order of things, must necessarily obtain in mountain 
islands, as it w r ere, par excellence), the fact still remains, 
that in the Madeiran Group the acquired areas, even up 
to the present date, of a vast proportion of the insect 
inhabitants, are wonderfully circumscribed. The real 
state of the case, however, would appear to be simply 
this : that the floods, although they may have tended to 
diffuse the members of a comparatively uniform alpine 
fauna in the various clefts or gorges beneath, can have 
had no power to combine the aborigines of the several 
gorges themselves ; and, since a large proportion of the 
endemic species of those islands are (as I have previously 
stated) apterous, the perpendicular edges of the ravines, 
which in many instances rise to an elevation of 2000 
feet, have acted (and ever will act) as impassable barriers 
to vast numbers of the insect tribes. 

With this single example (by way of illustration), 
which the Madeiras have supplied, I will take my leave 
of the question of natural barriers, as tending to regulate 
the topographical diffusion of the Annulosa, feeling that 
I have already devoted too much time and space to this 
portion of the subject (if such indeed it be) which I had 
proposed in the present treatise to discuss. Other 
barriers might have been adverted to, such as large 
rivers, extensive deserts, and thickly set forests (espe- 
cially of pine-trees, which frequently offer a very decided 

* Insecta Maderensia, p. 81. 


impediment to insect progress), but they are of 
secondary importance, when compared with marine and 
alpine ones ; and their consequences may be, to a certain 
extent, deduced from the considerations which I have 
just entered into. My main object has been to draw 
attention to the fact, that the great obstacles which 
Nature has placed against the too rapid dispersion 
of animal life should be more strictly taken into account 
(as a matter of positive reality) than it is, during our 
investigations into entomological geography. To be 
aware that these barriers exist, and yet to feel surprised, 
especially in a country where the species are principally 
wingless, that we do not discover indications of a general 
uniformity in its fauna, involves an absurdity, unless 
the doctrine of specific centres of creation be a mere 
coinage of the brain. But, if we believe in that theory 
(which, until it can be shown to be impossible, I hold 
that we are a priori bound to do), we must at least act 
consistently with ourselves, and not anticipate phseno- 
mena where we have neither reason nor right to look 
for them. 

We are too apt to draw a line of imaginary demarca- 
tion between the sciences, as though each had its own 
propositions to establish, and nothing more : indeed, 
some of us would appear to assume (though perhaps 
tacitly), that what is proved to be true in one depart- 
ment may be, at least, rendered inconsistent (if not 
actually negatived) in another. But surely this requires 
no argument to refute, since a principle which is true. 


is true under every circumstance and condition; for 
otherwise, it could be both true and false. We need 
not therefore be afraid of comparing truth with truth, 
under whatever shape it may arrive, as though it were 
possible that either of its phases could ever suffer from 
the ordeal of a close contact ; since, if they be really 
true, and free from deception, they must needs go hand 
in hand, and may become (however opposite they be in 
their subjects) directly explanatory of each other. The 
astronomer who is not intimately acquainted with pure 
mathematical analysis, in its various aspects and 
bearings, is in fact no astronomer at all. The geologist 
who would interpret the grand phenomena of the earth's 
crust apart from statical and dynamical knowledge, and 
without the help which the chemist, mineralogist, 
anatomist, zoologist, and botanist can afford him, stands 
a fair chance of leaving his problems unsolved ; whilst 
the students of zoology and botany who would endeavour 
to understand, and account for, what they see in the 
animal and vegetable worlds around them, without 
calling in geology to their aid, must assuredly be pre- 
pared to fail signally in their attempts. All indeed 
must work in concert, if the whole is to be advanced,- 
and not only in concert, but as mutually assisting each 
other. "By the help of truths already known, more 
may be discovered; for those inferences which arise 
from the application of general truths to the particular 
things and cases contained under them, must be just.* ; 
* Religion of Nature Delineated, pp. 73, 74. 




How glorious to the observant eye is the great system 
of the organic world, how perfect in each separate part, 
how complete and harmonious the whole ! The unity 
of the comprehensive plan, amidst the infinite modifica- 
tions which it includes, has ever been a theme of admi- 
ration and delight ; for the mind, which has once caught 
a glimpse, even in physics, of what it is not possible to 
disprove, instinctively clings to it, as to a grand material 
truth. The discovery, at all times, of what we feel to 
be actually certain is in itself so fascinating, that the very 
data which it gives us are scarcely more prized than the 
mere knowledge that we have gained a single additional 
light to guide us on our forward way : for, since in the 
inductive sciences we can but climb from step to step, 
at a slow and even pace, we hail with inward satisfaction 
whatsoever may tend to lighten our task, and to lead us 
more quickly onwards (gradually though we must of 
necessity advance) towards its final accomplishment. 

But how, it may be asked, is this general harmony of 
the organic creation to be insisted upon, when beings so 
extravagant and dissimilar are everywhere to be met 


with ? Is it possible to recognize anything like a unity 
of type amongst creatures so differently constructed, 
and so widely removed from each other in their habits, 
aspects, functions, and attributes? Such questions as 
these, however, though they may occasionally perplex 
the tyro, or amateur, are not likely to be raised by any- 
one who has mastered the merest alphabet of zoology, 
and who is aware that the integrity of Nature is some- 
thing real and positive, as experience indeed is ever 
tending more and more to corroborate, and by no means 
the day-dream of an enthusiastic, or fertile, imagination. 
To trace out the progressive development of animal life, 
from its humblest phases ; and to mark, as they become 
visible in the intermediate grades, the first rudiments 
of organs and instincts which are destined to attain 
their maximum in the higher ones, embody but a small 
portion of what it is the naturalist's mission to investi- 
gate. To him belongs the special privilege of inquiring 
dogmatically into this structural advancement ; and of 
suggesting methods of classification which shall accord, 
in their several component divisions, so far at least as is 
practicable, with the constitutional change. We should 
recollect, however, that this system, being based upon 
truth, must, if it would be consonant throughout, adapt 
itself to all the various phenomena (in their respective 
positions, in the scale), from the consideration of which 
it should be exclusively deduced, or built. To draw 
broad conclusions of any kind, or to attempt the esta- 
blishment of propositions and principles, from simple 


dialectics, without a previous training in the practical 
bearings of the subject, would be absurd, and almost 
certain to beget error. " It cannot be that axioms 
established by means of reasoning [alone] should be of 
any value for the discovery of new results ; because the 
subtilty of Nature far exceeds the subtilty of reasoning. 
But axioms duly and orderly abstracted from parti- 
culars, in their turn easily point out and mark off new 
particulars ; and so render the sciences active*." Such 
were the words of the greatest philosopher which this 
country has ever produced ; and it would be well, whilst 
examining the causes of what we see, and endeavouring 
to obtain some faint and distant notion of the vast 
scheme of Nature as originally designed, to keep them 
constantly in view, lest, by trusting to theory only, 
apart from observation and facts ; or by venturing to 
pervert the latter (instead of being led by them), so as 
to tally with our preconceived ideas of what ought to be, 
we miss our road, and become lost in the mazy labyrinth 
of our own fanciful inventions. 

With this preliminary stricture on the express duty 
which devolves upon the naturalist (with whom the 
phenomena of the organic world principally rest, for 
interpretation) to make facts, rather than reason and 

* " Nullo mode fieri potest, ut axiomata per argumentationem 
constituta ad inventionein novorum operum valeant ; quia subtilitas 
natures subtilitatem argumentandi multis partibus superat. Sed 
axiomata a particularibus rite et ordine abstracta, nova particularia 
rursus facile indicant et designant; itaque scientias reddunt ac- 
tivas." Novum Organum, Aphoris. xxiv. 


argument, the basis of his various doctrines, at any 
rate of those in which the critical subject of arrangement 
is concerned ; I shall perhaps be pardoned, after having 
been drawn, in the preceding chapters (however involun- 
tarily), into the question of ' species/ as rigidly defined, 
if I now offer a few passing remarks on the theory of 

There can be no doubt that amongst a large class of 
ordinary observers a clear perception of the generic 
system, in an abstract sense, does not by any means 
prevail. What the nature of a genus really is, would 
appear to have been very commonly overlooked, or per- 
haps misunderstood, by people of this stamp; and the 
consequence has been, that the wildest notions have 
frequently arisen, even from men of sound specific 
attainments, as to the claims (for annihilation or re- 
tention, as ( genera ') of certain subsidiary zoological 
assemblages. The terms ' genus ; and ' species ' have 
been conjointly so long associated in our minds with the 
selfsame things (whatsoever they may be), that they 
have become almost part and parcel of the objects them- 
selves; so that the student who does not sufficiently 
reflect on their true signification, is apt to regard them 
as of equal importance, or, rather, more often perhaps 
than otherwise, to make the latter subservient (or 
inferior) to the former ! This however is, in reality, the 
very reverse of what should be the case, as a moment's 
consideration will indeed at once convince us : for what 
are genera, after all, but dilatations (as it were) along a 


chain which is itself composed of separate, though dif- 
ferently shaped, links? The links (or the actual, inde- 
pendent bodies which constitute the chain) are the 
species ; but the knobs, or swellings, which their several 
forms may tend, by degrees, to establish along its course 
(through the slight disparity which each of them pre- 
sents from that which is next in succession to it; and 
therefore through the gradual manner in which the 
bulbs, or nodules, may be said, on the whole, to be pro- 
duced), are the groups into which those species naturally 
fall. It matters not a straw whether these assemblages 
be primary, secondary, tertiary, &c., in other words, 
whether they be departments, families, or genera, as 
usually understood, the principle is in every instance 
the same ; the difference being merely relative, and not 

Or, if we choose to vary the simile, we may compare 
the whole system to a cord, upon which beads, of innu- 
merable sizes, patterns, and colours, have been densely 
strung. Now, if there were no such things as natural 
divisions in the organic world, these beads (which repre- 
sent the separate species) might have been disposed of 
anyhow, their positions, with respect to each other, 
would under those circumstances have been of no im- 
portance. But such is not the case : there is an order 
and method throughout Nature, which shows that every 
individual portion of it has been adjusted by the Master's 
hand, and that nothing has been left to chance. Those 
beads (to follow up the metaphor) of countless magni- 


tudes and hues, have had their proper places allotted to 
them, and moreover with such care and regularity, that 
a complete plan, or scheme, of distribution is at once 
conspicuous. Although there are not even two, amongst 
that enormous multitude, which are precisely alike (for 
every species, however it may resemble its next ally, has 
some distinctive feature of its own), we immediately per- 
ceive that those beads which have most in common, are, 
as it were, attracted to each other, so as, by their close 
approximation, or contact, to create excrescences and 
stripes, of divers kinds, along the entire length of the 
cord. If we assume now that the red beads have been 
collected together, to the length (for instance) of a yard, 
and that within that space a dozen protuberances, of 
discordant aspects and dimensions, have (by the union 
of those beads which more nearly simulate each other) 
been brought about ; we shall have a very fair idea of 
the ordinary grouping of the animate tribes. The red 
beads, taken in the mass, may be likened to a perfect 
" family ;" the differing gibbosities to twelve well-marked 
" genera," which that family includes ; whilst the 
" species ' (the real dramatis persona, of independent 
existence, which are nevertheless compelled to occupy 
the situations we have described, thus causing the divi- 
sions to be mapped out) are here typified, as everywhere, 
by the several beads themselves. 

I have not thought it necessary to pursue this reason- 
ing into higher divisions than " families ;" but of course 
it may be extended to any amount, so as to shadow 


forth, equally, the compartments of primary significance. 
Nor would I wish to imply, by the above similes, that I 
regard a lineal method of arrangement as the correct one. 
Every zoologist is aware, that in Nature such does not 
exist : but the mode of illustration which I have selected 
is applicable to all systems alike, so far as the principle 
is concerned. 

It will consequently be seen, from what has been said, 
that the terms " genus " and " species '' not only differ 
very considerably in importance, but in signification also. 
Whilst the former is merely suggestive of a particular 
position which a creature occupies in a systematic scale 
(a position, however, which depends upon the various 
structural peculiarities which it possesses in common with 
other beings, which thus more or less resemble it) ; the 
latter expresses the actual creature itself: so that while 
one applies to several animals (of distinct natures and 
origins, though bound together by a certain bond of 
imitation), the other belongs to a single race alone, which 
it therefore exclusively indicates. But if such be the 
case, it will perhaps be asked, Why then insist upon a 
generic name at all, if "the specific one be sufficient to 
denote all that is required, namely, the animal itself*} To 
which, however, we may reply, that the binomial nomen- 
clature is demanded for two elementary reasons, first, 
because it is founded upon a natural truth, which (to say 
the least) it would be unwise to violate ; and, secondly, 
because it is convenient, both for simplification and 
analysis. We should assuredly be surprised were a man 

to object to his surname, as unnecessary, because lie has 
a Christian (or specific"*) one which is the exponent of 
him alone. True it is that his family (or generic) title 
applies to the rest of his kin also ; but, since there are 
other people (of other families) who may have the same 
individual appellation as himself, it is clearly desirable, 
even as a matter of expediency alone, that patronymic 
and Christian name should be alike retained. We need 
not, however, plead expediency, in favour of this accept- 
ance of what has been so long tested, and shown to be 
correct ; we appeal to a higher tribunal, that of expe- 
rience, in proof that it draws its origin from Nature 
itself, and is implied by the very existence, or reality, of 
natural groups. The ' Methode Mononomique ' has indeed 
been attempted f; and it has failed, or at any rate it 
has shown itself to be inferior, both ideally and in prac- 
tice, to the plan commonly in use : and if I might be 
pardoned a passing conjecture on its ultimate success, I 
should be inclined, since it is contrary to the canon of 
the organic world, to regard its case as utterly hopeless. 
Let us not be unfair, however, towards those who have 
sought to establish a nomenclature which they conceived 
would be less open to objections than that which we have 
been hitherto accustomed to endorse. The notion did, 

* In selecting this simple method to illustrate the principle of a 
binomial system of nomenclature, it is scarcely necessary to remind 
the reader that I do not intend to imply that every man is specifically 
distinct from his neighbour ! 

f Considerations sur un Nouveau Systeme de Nomenclature, par 
C. J. B. Amyot (Rev. ZooL, p. 133, A.D. 1838). 


at any rate, arise out of an apparent defect in the bino- 
mial process, for the inconveniences which they com- 
plained of are real ones ; and, having felt them practi- 
cally, they aspired to sweep them away by remodelling 
the wiiole system afresh. But, had it not been for an 
evident misconception of the generic theory, in the 
abstract, the trial would in all probability have never 
been made ; and we should have been spared the downfall 
of a contrivance which has had but little to recommend 
it beyond the ingenuity of its machinery and detail. If 
we analyse the motives for this experiment, we shall find 
that it originated from a belief, that genera are either 
purely imaginary, or else that they must (like species) 
have a definite and isolated existence. Now both of 
these conclusions appear to be equally gratuitous and 
untenable ; and such as a lack of observation could alone 
beget. Genera are not mere phantoms of the brain (as 
most naturalists will readily admit) ; but they are, like- 
wise, by no means abrupt, or well-marked, on their 
outer limits (except indeed by accident, of which here- 
after), but merge into each other by gradations, more 
or less slow and perceptible. Such being the case, we 
can easily understand why it is that the followers of the 
' Methode Mononomique' (who, paralysed by the fact that 
genera are seldom clearly defined at their extremes, would 
seem to repudiate them in toto) have rashly regarded the 
binomial system as intolerable. Finding that it was 
possible for numerous species, whose structural charac- 
teristics were less conspicuously pronounced than those 


of their allies, to be enumerated, and with equal plausi- 
bility, under two consecutive groups ; they immediately 
inferred that the groups themselves could not be upheld 
on account of these connective links : and so it was re- 
solved (through a new and artificial scheme) to ignore 
them ; and to fall back upon the creed, that species alone 
(and not genera) are to be recognized in the organic 
world. This was but the device, however, at the outset, 
of a single mind ; and the perverts to it have been but 
few. It is in direct opposition to the first principles of 
nomenclature, and sets at defiance a great natural truth. 
But what, it may be inquired, is this great primary 
truth which the monomial system tends to violate ? I 
repeat what I have already stated, that it is the existence 
of natural assemblages which that scheme would, if it 
were practicable, discountenance. Order and symmetry, 
however (which involve classification, or arrangement), 
are the law of Nature, and it is not possible to set them 
aside. It matters not if harsh lines of demarcation are 
undiscernible between the several consecutive groups, 
the groups themselves must still remain (however equivo- 
cal it may be where they exactly commence or termi- 
nate), and cannot be wiped out. To suppose a priori 
that the allied divisions of the animate creation are per- 
fectly disconnected inter se } is in fact to break the chain 
on which the unity of the organic world depends ; whilst 
to assume that groups cease to be groups when they can 
be discovered to merge into each other, would no less 
destroy the harmony of that admirable method, or 


array, which the naturalist, above all others, delights to 
contemplate. If things are no longer to be regarded as 
dissimilar because they unite on their outer limits, 
differences may be given up, as having no special 
meaning, and as therefore unworthy of investigation. 
It requires but a slight insight into the physical universe 
to be convinced, that nearly everything which we see 
(and, moreover, without injuring its individual reality] is 
blended into that to which it is the most akin. Night 
is distinct from day ; yet, so long as the twilight inter- 
venes, no man can pronounce where the one ends, and 
the other begins. Heat is opposed to cold ; yet, if by 
degrees they be respectively diminished, they will at last 
amalgamate, in a central temperature. And thus it is 
with things material. The sea and the land are essen- 
tially unlike ; yet the precise boundary between the two 
is never clearly denned, the ebb and flow are constantly 
going on, and the line of separation is variable. The 
mountain-range is moulded on a different type to the 
level country beneath it ; yet the turning-point of them 
both is, in all instances, on neutral ground. We need 
not however adduce further evidence in support of this 
fact, that, throughout the whole of Nature, the general 
principle of fusion (either absolute or apparent) is most 
obvious. From first to last, traces of it are everyAvhere 
to be detected ; not only between clusters, or material 
combinations, of objects (in which case it is absolute), 
but even between the objects themselves, under which 
circumstances, however, it is merely apparent ; for, since 


they are specifically dissimilar, it can only arise from 
their near resemblance to each other, and not from their 
positive coalescence. But, admitting that this universal 
blending, throughout the animate world, does not inter- 
fere with the gradual conformation of its several groups, 
which therefore should be recognized ; we may perhaps 
be told by the believers in the c Methode Mononomique/ 
that they do not intend to ignore the arrangement which 
Nature has so broadly laid down, but that, on the 
contrary, they tacitly endorse it, their device having 
reference to the names only. To this however it will be 
sufficient to reply, that, if they deem it necessary (of 
which I am by no means convinced) to accept the 
natural genera of the organic creation at all, why not 
acknowledge them ? and how can they be so well 
acknowledged, either in principle or practice, as through 
the medium of a binomial nomenclature? Such a 
system is the only consistent one, on the hypothesis that 
they do consider them of primary importance; it is 
more in unison with our notions of what ought to be ; 
more suggestive of what actually is ; more honest and 
generous to those who have laboured (as describers), with 
such care and diligence, before us. 

It will be perceived, from the above remarks, that, 
although professedly criticizing the ' Methode Mono- 
nomique/ into the analysis of which my subject has 
unintentionally drawn me, it is the absurdity of ob- 
jecting to genera because they are not rigidly defined 
throughout, that I have been mainly striving to con- 


demn. It is indeed well nigh incredible that any such 
strictures could ever have been advanced ; for it must 
surely have occurred to the most superficial inquirer, 
that genera, after all, cannot be homogeneous, seeing 
that they are necessarily composed of detached species, 
no two of which are precisely similar, even in the few 
structural details which may have been accidentally 
chosen for generic diagnostics. How is it possible, 
therefore, that mere groups, even though they be in 
accordance with Nature, should be so far isolated and 
uniform in their character as to occupy an analogous 
position to that of the absolutely independent species (of 
distinct origins) which they severally contain ? 

Taking the preceding considerations into account, the 
question will perhaps arise, How then is a genus to be 
defined? To which I may reply that, were I asked 
whether genera had any real existence in the animate 
world, my answer would be that they undoubtedly have, 
though not in the sense (which is so commonly 
supposed) of abrupt and disconnected groups. I con- 
ceive them to be gradually formed nuclei, through the 
gathering together of creatures which more or less 
resemble each other, around a central type : they are 
the dilatations (to use our late simile) along a chain 
which is itself composed of separate, though differently 
shaped links, the links being the actual species them- 
selves, and the swellings, or nodes, the slowly developed 
genera into which they naturally fall. When I say 


" slowly developed," my meaning may possibly require 
some slight comment. It is simply therefore to guard 
against the fallacy, which I have so often disclaimed, 
that genera are abruptly (or suddenly) terminated on 
their outer limits, that the expression has been employed. 
Though I believe that a series of species, each partially 
imitating the next in contact with it, is Nature's truest 
system ; yet we must be all of us aware that those 
species do certainly tend, in the main, to map out 
assemblages of divers phases and magnitudes, distin- 
guished by peculiar characteristics which the several 
members of each squadron have more or less in common. 
So that it is only in the middle points that these various 
groups, respectively, attain their maximum, every one 
of which (by way of illustration) may be described as a 
concentric bulb, which becomes denser, as it were, in its 
successive component layers, and more typical, as it 
approaches its core. 

If, then, the theory of genera be such as I have endea- 
voured to expound, it results from what has been said, 
that every generic type is to be looked for in, or about, 
tJie centre of its peculiar group, or at any rate in that 
region of it which would seem to be the most charac- 
teristically, or evenly, pronounced. I lay particular 
stress upon this conclusion, because (if correct) it will 
somewhat modify the notions which are occasionally 
entertained upon the subject. A stricture, however, 
may here be required upon what I have advanced, lest, 


through using the metaphors which I selected for the 
elucidation of a principle, it be supposed that I would 
wish them to apply to the smaller details, likewise, of 
the problem. If a genus has been portrayed under the 
similitude of a bulb, or of a nodule (formed by the ap- 
proximation of beads which more or less resemble each 
other in their primary aspect), it does not follow that 
either bulb or nodule are to diminish in a similar ratio 
towards their respective circumferences, or, which is the 
same thing, that they are to be symmetrical ; whether 
spherical, ovoid, or otherwise. The general method of 
the organic creation is a progressive one; and its suc- 
cessive types, therefore, will not always be found to 
radiate equally from their normal foci : so that it is in the 
direction of the higher (rather than the lower) extre- 
mities of the assemblages that those foci are usually to 
be discerned ; and where the groups are large, it is not 
often difficult to pronounce which of their ends are, as a 
whole, the more perfectly developed. 

It will, moreover, be further acknowledged (if my 
premises are allowed), that, since it is a somewhat 
central position which the typical member of a genus 
usually occupies, the diagnostic characters, although (in 
combination) carried out to the full, are more evenly 
balanced in a generic type than in any of its associates ; 
or, in other words, that a species in which any single 
organ is monstrously enlarged, at the expense of the 
rest, is seldom typical of the assemblage with which it is 
placed ; but may be a priori regarded as in all proba- 


bility a transition form, leading us onwards into some 
neighbouring group *. 

I will not, however, venture too closely into this ques- 
tion in its minor bearings ; suffice it to have demon- 
strated that, whatever be the rate, law, or direction, of 
the advancement of the various groups towards a more 
perfect model ; or in whatsoever position the several types 
are to be discerned, with respect to their immediate 
associates, genera cannot be isolated and distinct, but 
must of necessity merge (each into two or more others) 
on their outer limits. Hence, if such be the case, as I 
contend that it usually is (the exceptions to the rule 
being, as I shall hope shortly to prove, the result of 
accident, and by no means a part of the original design), 
it may perhaps be a problem, how far we are justified in 
rejecting many large and natural assemblages, through 
the fact that they blend, both at their commencement 
and termination, imperceptibly, with others, their pre- 
cise boundaries being dimly defined. 

That the recognition of genera is necessary, even as 
a matter of mere convenience, is self-evident; for in 
many extensive departments they combine with each other 
so completely at their extremities (although sufficiently 
well-marked in the mass), that, unless we are prepared 

* I may add, that this suggestion, as to the evenly balanced state 
of generic types, is in accordance with the views of Mr. Waterhouse, 
whose extensive knowledge in the higher departments of zoolo- 
gical science gives a value to his opinion, especially on questions 
such as these, which I am glad to have an opportunity of acknow- 


to accept them as they are, we must needs repudiate 
them altogether : under which circumstances, our diffi- 
culties, both in determination and nomenclature, would 
be increased tenfold. We should also recollect, that 
clusters which seem abruptly chalked out whilst our 
knowledge is imperfect, are very frequently united with 
others when fresh discoveries are made, and the inter- 
mediate grades brought to light : so that their apparent 
isolation may oftentimes arise from our ignorance of the 
absent links, rather than from the fact itself. It would 
surely be more desirable, therefore, when viewed even 
in the light of expediency alone, to submit to the possi- 
bility of a few neutral species being conceded, with equal 
reason, to different groups, than to amalgamate the 
whole, and so lose sight of the general method or 
arrangement, into which the various creatures do un- 
questionably (in a broad sense) dispose themselves. If, 
however, there be any truth in the generic doctrine 
as above enunciated, the question of convenience may be 
omitted from our speculations in toto, seeing that all 
genera (except those whose present abruptness is the 
effect of accident) fuse into others with which they are 
in immediate contact : so that in reality, unless we 
ignore these natural assemblages from first to last, we 
have no choice left us as regards the equivocal forms ; 
but must consent to recognize them as of doubtful loca- 
tion, and as possessing an equal right to be placed in 
one or the other of two consecutive groups, according 


to the judgment of the particular naturalist who has to 
deal with them. 

But let us glance at the subject through the medium 
of an example, and endeavour to realize what would be 
the consequence of that wholesale combination at which 
we must sooner or latter arrive, if genera are not to be 
upheld because they slowly merge into each other as we 
recede from their respective types. The immense de- 
partment Carabidce, of the Coleoptera, is eminently a 
'case in point. In the details of their oral organs the 
whole of that family display (as I have elsewhere* re- 
marked) so great a similarity inter se, or rather shade 
off into each other by such imperceptible gradations, 
that the tendency which various clusters of them possess 
to assume modifications of form which attain their max- 
imum only in successive centres of radiation, must often- 
times be regarded as generic, if we would not shut our 
eyes altogether to the natural collective masses into 
which the numerous species (however gradually) are, in 
the main, so manifestly distributed. It is possible 
indeed that, as our knowledge advances and new dis- 
coveries take place, we shall so far unite many of the 
consecutive nuclei which are now considered pretty 
clearly defined, that we shall be driven at last either to 
accept the Linnsean genera only, or else the entire host 
of subsidiary ones (albeit perhaps in a secondary sense) 
which are, one by one, being expunged. And, since 
* Annals of Nat. Hist. (2nd series), xiv., p. 199. 


under the former contingency the determination of species 
would become practically well nigh hopeless, it is far 
from unlikely that we shall eventually hail the latter as, 
after all (at any rate to a certain extent), the more con- 
venient of the two. Look, for instance, at the great 
genus Pterostichus, which has nearly 200 representatives 
in Europe alone : true it is that its several sections 
(Pcecilus, Argutor, Omaseus, Corax, Steropus, Platysma, 
Cophosus, Pterostichus proper, Abase, Percus, and Molops), 
although easily recognized in the mass, do unquestionably 
blend into each other; yet I believe that it has arisen 
from a too rigid promulgation of the generic theory 
that they have not been retained as separate. And this 
opinion may be rendered somewhat more plausible, 
from the knowledge that certain of the Pterostichi (the 
Argutors, for instance) approach so closely, in their 
trophi, to Calathus, as to be hardly discernible from it ; 
which latter genus is scarcely distinguishable (struc- 
turally) from Pristonychus, a form which, in its turn, 
leads us on towards another type. Who would have 
imagined, again, some fifty years ago, that the widely 
distributed groups, Calosoma and Carabus, were not 
thoroughly detached inter se ? yet what naturalist now 
can draw an exact line of demarcation between them ? 
And so it is with numerous others, which it is needless 
to recall. The practical inference, however, from the 
whole, is this : that if genera must be rejected because 
they are not homogeneous and isolated throughout, the 


only ones that will remain are those which have become 
abrupt from causes which are merely accidental. 

Having now, however, examined the question in its 
broadest phasis, that is to say, on the supposition that 
Nature is complete in her several links and parts; I 
shall perhaps be expected to offer a few passing words 
on what I have already hinted at, namely, the possi- 
bility of genera being absolutely well-defined, even on 
their outer limits, from accident. Briefly, then, it is 
through the extinction of species that groups may, in 
some instances, be abruptly expressed : but, as such 
contingences are at all times liable (whether from 
natural or artificial causes) to happen; it would be 
unfair to build up our generic definition from examples 
which are the exception, and not the rule, and, more 
than mere " exceptions ' (as commonly understood by 
that term), the result of positive disturbances from 
without. Yet, that genera thus distinctly bounded, at 
either end, do actually occur, must be self-evident to 
any one who has attempted to study the distribution of 
organic beings with reference to the geological changes 
which have taken place on the earth's surface ; for it is 
clear that a vast proportion of the creatures which 
inhabit our globe came into existence at periods anterior 
to many of those great convulsions which altered finally 
the positions of sea and land, apportioning to each the 
areas which they now embrace : so that, if generic 
provinces of radiation (no less than specific centres) be 


more than a fancy or romance, it is certain that nume- 
rous members of many geographical assemblages must 
have perished for ever during the gigantic sinkings 
which have at various epochs been brought about. From 
which it follows, that those groups, or clusters, of which 
but few representatives (comparatively] are extant, will 
be more or less abruptly terminated, according as the 
original type to which they severally belong ivas peculiar., 
and in proportion as the number of its exponents has been 

Although there are many means through which 
species may become annihilated, yet, since the sub- 
sidence of a tract into the sea involves the maximum of 
loss which a space of that magnitude can sustain, the 
above conclusion gives rise to a corollary : that it is in 
islands that we should mainly look for genera which 
are to be rigidly pronounced. The question therefore 
naturally suggests itself, Is this in harmony with what 
we see; or, in other words, is it consistent with ex- 
perience, or not? I believe that it is; for I think it 
will be found, on inquiry, that the greater proportion of 
those groups which are more especially isolated in their 
character (I do not say, necessarily, the most anomalous ; 
though this in some measure follows from, the fact of 


their detachment) are peculiar to countries which are 

But, however important an element, in the eradica- 
tion of species, submergence may be; we must not 
entirely omit to notice other methods also, through the 

t 5 


medium of which genera may become well-defined. We 
should recollect that the removal of a very few links 
from an endemic cluster is sufficient to cause its dis- 
junction from the type to which it is next akin, and that 
where the creatures which unite in composing it are of 
slow diffusive powers, or sedentary habits, the elimina- 
tion of such links is (through the smallness of the areas 
which have been overspread) a comparatively easy opera- 
tion. The accidental introduction of organic beings 
amongst others to the interests of which they are hostile, 
may be a powerful means, as Mr. Darwin has suggested, 
of keeping the latter in check, and of finally destroying 
them*. The gradual upheaval of a tract which has 
been well-stored with specific centres of radiation, 
created expressly for itself, may (through the climatal 
changes which have been brought about) succeed in 
extirpating races innumerable, those only surviving 
which are able to adapt themselves to the altered condi- 
tions ; and which would now be consequently looked 
upon as abrupt topographical assemblages. The over- 

* A familiar example of this disappearance of a creature before 
the aggressive powers of another, which is either hostile to or stronger 
than itself, is presented by the Black Rat (Mus rattus) of our own 
country, which is said to have been extremely abundant formerly, 
but which is now replaced by the common brown (or " Hano- 
verian ") one of Northern Europe. The British species, how r ever, 
although it has become extremely scarce, is not yet quite extermi- 
nated : it has been recorded (vide ' Zoologist,' 611) in Essex, and in 
Devonshire (' Zoologist,' 2344) ; and it still swarms on a small rock 
off Lundy Island, in the Bristol Channel. It is reported, moreover, 
to have been lately re-introduced at Liverpool. 


whelming effect of a volcanic eruption, in a region 
where the aborigines of the soil have not wandered far 
from their primaeval haunts, may, as Sir Charles Lyell 
has well remarked, put an end to others, and so effect 
the separation of their allies from the central stock. 
And, lastly, the intervention of man, with all the various 
concomitants which civilization, art, and agriculture 
bring in his train, is the most irresistible of every 
agency in the extensive (though often accidental) demo- 
lition of a greater or less proportion of the animate 

The whole of these ultimate assortments, however, are 
dependent, as it were, for their outline, upon contingency 
or chance ; and we must not deduce our ideas of genera 
from the examples which they supply. We should 
rather reflect, that it is no matter of mere speculation, 
that many organic links, now absent, have, through the 
crises and occurrences to which we have just drawn 
attention, become lost. On the contrary, indeed, we 
know that, in the common course of things, it must 
have been so; and therefore we are induced to regard 
those cases as exceptional, and as in no way expository 
of Nature's universal scheme. The more we look into 
the question, whether by the light of analogy or the 
evidence of facts, the more are we convinced that lines 
of rigid demarcation (either between genera or species, 
though especially the former) do not anywhere, except 
through accident, exist. And hence it is that we ascend, 
by degrees, to a comprehension of that unity at which I 


have already glanced ; and are led to believe that, could 
the entire living panorama, in all its magnificence and 
breadth, be spread out before our eyes, with its long-lost 
links (of the past and present epochs) replaced, it would 
be found, from first to last, to be complete and continuous 
throughout, a very marvel of perfection, the work of a 
Master's hand. 



Deposita sarcina, levior volabo ad coelum. S. Jerome. 

HAVING now completed the short task which I had 
undertaken to perform, I will, in conclusion, offer a few 
brief comments on the results at which we have arrived, 
and endeavour to realize to what extent the considera- 
tion of them is likely to be found useful, during our 
inquiries into the general subject of entomological 

Commencing with the thesis, that specific variation, 
whether as a matter of experience or as probable from 
analogy, does ipso facto exist ; I have endeavoured to 
maintain that position, by evidence of divers kinds j and 
I have sought to strengthen the inferences deduced, by 
an appeal to some of those external agents and circum- 
stances which may be -reasonably presumed (if not 
indeed actually demonstrated) to have had a consider- 
able share in bringing it about. I have also suggested 
what the principal organs and characters are, in the 
Insecta, which would appear to be more peculiarly 
sensitive to the action of local influences; and I have 
then diverged to the question of topographical distribu- 
tion, in connection with the geological changes on 
the earth's surface ; and, lastly, to some practical hints 


arising out of a proper interpretation of the generic 
theory. How far I have succeeded in elucidating the 
several points which I proposed to examine, is a problem 
which must be solved by others ; meanwhile, if I have 
failed at times to interpret what seems scarcely to admit 
of positive proof, I shall at least have had the advantage 
of propounding the enigmas for discussion, and of so 
paving the way for future research. We must remember, 
however, that, where certainty is not to be had, proba- 
bility must be accepted in its stead ; or, as an old writer 
has well expressed it : " That we ought to follow pro- 
bability when certainty leaves us, is plain, because it 
then becomes the only light and guide that we have. 
For, unless it is better to wander and fluctuate in abso- 
lute uncertainty than to follow such a guide ; unless it 
be reasonable to put out our candle because we have not 
the light of the sun, it must be reasonable to direct our 
steps by probability, when we have nothing clearer to 
walk by *". 

What my chief aim in the present treatise has been, 
will be easily perceived, namely, to substantiate, as 
such, those elements of disturbance (on the outward con- 
tour of the Annulose tribes) with which the physical 
world does everywhere abound : and, thereupon, to pro- 
voke the inquiry, whether entomologists, as a mass, have 
usually taken them into sufficient account, when de- 
scribing as "species," from distant quarters of the 
globe, insects which recede in only minute particulars 
* Religion of Nature Delineated, p. 103. 


from their ordinary states. My own impression is, that 
they have not done so ; and, moreover, that, if they 
had, our catalogues would have worn a very different 
appearance to what they now do : for, when once the 
subject is fairly looked into and analysed, it is impossible 
not to be convinced, that the primd-facie aspect of these 
creatures is eminently beneath the control of the several 
conditions to which they have been long exposed. But 
let me not be misunderstood in the conclusion which I 
have been thus compelled to endorse, or be supposed to 
ignore the fact that truly representative species may 
frequently occur in countries far removed from each 
other; which cannot therefore be regarded as modifica- 
tions of a common type. I believe, however, that this 
doctrine of representation, whatever truth it may con- 
tain, has been too much relied upon ; and that we have 
been over-ready to take advantage of it (unproved as it 
is) for the multiplication of our, so called, " specific 
novelties/' I suspect, indeed, that actual representative 
species (if they may be thus expressed) are more often 
to be recognized on the isolated portions of a formerly 
continuous tract, than in regions which have been widely 
separated since the last creative epoch ; and that, in the 
instances where beings of a nearly identical aspect are 
detected in opposite divisions of the earth, it is more 
often the case that members of them have been trans- 
ported at a remote period (either by natural or artificial 
means) from their primaeval haunts, and have become 
gradually altered by the circumstances amongst which 


they have been placed, than that the respective phases 
were produced in situ on patterns almost coincident. 

I have before announced my conviction, that generic 
areas have a real existence in Nature's scheme; and 
that, consequently, where species which are so intimately 
allied that they can with difficulty be distinguished, 
prevail, there is presumptive reason to suspect (until at 
least the contrary is rendered probable) that the areas 
which they now colonize were once connected by an 
intervening land, or, in other words, that the migra- 
tions of the latter were brought about, through ordinary 
diffusive powers, from specific centres within a moderate 
distance of each other. I say "presumptive reason/' 
because there are undoubted exceptions to this law (as 
to every other), and it can therefore be only judged of 
on a broad scale. Still, I contend that in a wide sense 
it holds good ; and that, consequently, if closely related 
" species ' are traceable in countries which geology 
demonstrates to have been far asunder during the entire 
interval since the first appearance of the present animals 
and plants upon our earth, there is at any rate an 
a priori probability that they are no species at all, but 
permanent geographical states, which have been slowly 
matured since their casual introduction beyond their 
legitimate bounds. 

If we except those forms which are in reality but 
modifications, from climatal and other causes (and 
which have, therefore, been wrongly quoted as distinct) ; 
I believe that a vast proportion of the species which 


have been usually considered to be " representative y 
ones, were members, in the first instance, of the self- 
same assemblages, which had wandered to a distance 
from their primaeval haunts, and were afterwards, 
through the submergence of the intervening land, cut 
off from their allies. I have adduced, in a preceding 
chapter, some remarkable examples in illustration of 
this hypothesis, an hypothesis which I believe to be 
the true clue to a very large item of the " specific 
representation ' theory. A considerable number of the 
Madeiran Helices may be cited (which I have already 
done *) as, in the strictest sense, representative of each 
other, and as therefore specifically distinct : and I 
may add, that it is to island groups that we must 
mainly look for this system in its full development. 

But, apart from the fact that I would not wish to 
resign in toto the doctrine of " specific representation," 
even as frequently understood (that is to say, as recog- 
nizable in countries which have been altogether dis- 
connected since the last creative epoch), and therefore, 
a fortiori, in what I conceive to be its truer meaning ; 
there is yet another point on which I would desire to be 
interpreted aright, whilst endeavouring to substantiate 
the action of local influences on the members of the 
insect world. It has been my aim, in the preceding 
pages, to call attention to the importance of external 
circumstances and conditions in regulating, within defi- 
nite limits, the outward aspect of the Articulate tribes. 

* Vide supra, p. 128. 


I do not, however, assert that every species is liable to 
be interfered with ab extra \ that is a question which 
the greater or less susceptibility of the several races, as 
originally constituted, can alone decide ; still less would 
I willingly lend a helping hand to that most mischievous 
of dogmas, that they are a//-important in their opera- 
tion, or, in other words, that they possess within them- 
selves the inherent power (though it may not invariably 
be exercised) of shaping out (provided a sufficient time 
be granted them, and in conjunction with the advancing 
requirements of the creatures themselves) those perma- 
nent organic states to which the name of species (in a 
true sense) is now applied. Such a doctrine is in reality 
nothing more than the transmutation theory, in all its 
unvarnished fulness ; and I do not see how it can be for 
a moment maintained, so long as facts (and not reason- 
ing only) are to be the basis of our speculations. I 
repeat, that it is merely within fixed specific bounds that 
I would advocate a freedom of development, in obedi- 
ence to influences from without : only I would widen 
those limits to a much greater extent than has been 
ordinarily done, so as to let in the controlling prin- 
ciple of physical agents, as a significant adjunct for our 

It does indeed appear strange that naturalists, who 
have combined great synthetic qualities with a profound 
knowledge of minutiae and detail, should ever have 
upheld so monstrous a doctrine as that of the transmis- 
sion of one species into another, a doctrine, however, 


which arises almost spontaneously, if we are to assume 
that there exists in every race the tendency to an un- 
limited progressive improvement. There are certainly 
no observations on record which would, in the smallest 
degree, countenance such an hypothesis. Many animals 
and plants, it is true, are capable of considerable modifi- 
cations and changes, for the better, very much more 
than is the case with others. But what does this prove, 
except that their capacity for advancement has a slightly 
wider compass than that of their allies ? It touches not 
the fact, that the boundaries of their respective ranges 
are absolutely and critically denned. It is moreover a 
singular phenomenon, and one in which the strongest 
proofs of design (or a primary adjustment of limits with 
a view to the future) may be discerned, that the mem- 
bers of the organic creation which display the greatest 
adaptive powers, are those which were apparently des- 
tined to become peculiarly attendant upon man. " The 
best-authenticated examples," says Sir Charles Lyell, 
"of the extent to which species can be made to vary 
may be looked for in the history of domesticated animals 
and cultivated plants. It usually happens that those 
species which have the greatest pliability of organiza- 
tion, those which are most capable of accommodating 
themselves to a great variety of new circumstances, are 
most serviceable to man. These only can be carried by 
him into different climates, and can have their pro- 
perties or instincts variously diversified by differences of 
nourishment and habits. If the resources of a species 


be so limited, and its habits and faculties be of such a 
confined and local character, that it can only flourish in 
a few particular spots, it can rarely be of great utility. 
We may consider, therefore, that in the domestication 
of animals and the cultivation of plants, mankind have 
first selected those species which have the most flexible 
frames and constitutions, and have then been engaged 
for ages in conducting a series of experiments, with 
much patience and at great cost, to ascertain what may 
be the greatest possible deviation from a common type 
which can be elicited in these extreme cases *." 

The fact, however, that all areas of aberration (how- 
ever large they may be) are positively circumscribed, 
need scarcely be appealed to, in exposing the absurdity 
of the transmutation hypothesis. The whole theory is 
full of inconsistencies from beginning to end ; and from 
whatever point we view it, it is equally unsound. How, 
for instance, can any amount of local influences, or the 
progressive requirements of the creatures themselves, 
give rise to the appearance of several well-marked re- 
presentatives of a genus on the self-same spot, where 
the physical conditions for each of them are absolutely 
the same ? Look, for example, at the Tarphii (to which 
I have already alluded f) of Madeira : I have detected 
about eighteen abundantly defined species ; and, as 
stated in a previous chapter, I have but little doubt, 
from their sedentary habits, and the evident manner in 

* Principles of Geology, 9th edition, pp. 583, 584. 
t Vide supra, p. 121. 


which they are adjusted to the peculiarities of the region 
in which they obtain, that they are strictly an esoteric 
assemblage, inhabiting the actual sites (or nearly so) of 
their original debut upon this earth. Here, then, we 
have a sufficient length of time for developments to have 
taken place; they are all exposed to the self-same 
agencies from without (for they live principally in com- 
munion) yet, though I have examined carefully more 
than a thousand specimens (a large proportion of them 
beneath the microscope), I have never discovered a 
single intermediate link which could be regarded as in a 
transition state between any of the remainder. But 
how is this ? Is it possible to account for differences so 
decided, yet each of such amazing constancy, amongst 
the several creatures of a central type which have been 
exposed to identical conditions through, at any rate, 
generations innumerable? They clearly cannot be ex- 
plained on the doctrine of transmutation : yet they are 
no exceptions to the ordinary rule, occupying an ana- 
logous position to the members of every other endemic 

But I will not occupy more space on the transmuta- 
tion theory : suffice it to have shown that, in thus con- 
ceding a legitimate power of self-adaptation, in accord- 
ance with external circumstances, to the members of the 
insect world; and in suggesting the inquiry, whether 
the action of physical influences has been adequately 
allowed for by entomologists generally (or, in other 
words, whether the small shades of difference which 


have often, because permanent, been at once regarded 
as specific, may not be sometimes rendered intelligible 
by a knowledge of the localities in which the creatures 
have been matured), I do not necessarily open the door 
to the disciples of Lamarck, or infringe upon the strict 
orthodoxy of our zoological creed. On the contrary, 
indeed, I believe that the actual reverse is nearer the 
truth ; and, moreover, that those very hyper-accurate 
definers who recognize a " species y - wheresoever the 
minutest decrepancy is shadowed forth, will be found 
eventually (however unaware of it themselves) to have 
been the most determined abettors of that dogma, see- 
ing that their species, if such they be, do most assuredly 
pass into each other. 

We must not, however, omit to notice, briefly, how 
this perversion of Nature' s economy took its rise. It 
was from the desire, which is almost inherent within us, 
to account for everything by physical laws ; and to dis- 
pense with that constant intervention of the direct crea- 
tive act which the successive races of animals and plants, 
such as are proved by geology to have made their appear- 
ance at distinct epochs upon this earth, would seem to 
require. Or, which amounts to the same thing, it 
resulted through an endeavour to explain by material 
processes what is placed beyond their reach. But, if 
this be the case, it may be reasonably asked, Are mate- 
rial laws then not to be inquired into, and should the 
various influences which operate in the organic world 
around us be debarred from analysis? Unquestion- 


ably not. Truth is truth, under Avhatever aspect it may 
come; and cannot possibly contradict another truth. 
To exercise our intellectual faculties, by tracing out, 
through slow, inductive methods, the modus operandi of 
even a single natural law, is an honourable task; nor 
should the apparent smallness of the media which we 
are at times compelled to employ, render it less so (else 
would this present treatise, like many others of a kindred 
stamp, have been best unwritten) : but it is from the 
conceit that our own imperfect interpretations have left 
nothing more to be found out, that the great danger is 
to be anticipated. An effect may be literally dependent 
upon a certain proximate cause ; and if we be so fortu- 
nate as to ascertain that cause, we have done something ; 
but it does not necessarily follow that we have done much. 
On the contrary, it often happens that, in so doing, we 
have achieved wonderfully little, seeing that the pro- 
blem may be self-evident. Behind that "cause," we 
should recollect, others lie concealed, of a far deeper 
nature, each depending upon the next in succession to 
it ; until, in the order of causation, we are at length led 
back, step by step, to the Final One, with which alone 
the mind can be thoroughly content. " We make dis- 
covery after discovery," says Dr. Whewell, "in the 
various regions of science ; each, it may be, satisfactory, 
and in itself complete, but none final. Something 
always remains undone. The last question answered, 
the answer suggests still another question. The strain 
of music from the lyre of Science flows on, rich and 


sweet, full and harmonious ; but never reaches a close : 
no cadence is heard with which the intellectual ear can 
feel satisfied*." 

As regards that most obscure of questions, what the 
limits of species really are, observation alone can decide 
the point. It frequently happens indeed that even 
observation itself is insufficient to render the lines of 
demarcation intelligible, therefore, how much more 
mere dialectics ! To attempt to argue such a subject 
on abstract principles, would be simply absurd ; for, as 
Lord Bacon has remarked, " the subtilty of Nature far 
exceeds the subtilty of reasoning : ' but if, by a careful 
collation of facts, and the sifting of minute particulars 
gathered from without, the problem be fairly and deli- 
berately surveyed, the various disturbing elements which 
the creatures have been severally exposed to having been 
dulv taken into account, the boundaries will not often be 


difficult to define. Albeit, we must except those races 
of animals and plants which, through a long course of 
centuries, have become modified by man, the starting- 
points of which will perhaps continue to the last shrouded 
in mystery and doubt. It would be scarcely consistent 
indeed to weigh tribes which have been thus unnaturally 
tampered with by the same standard of evidence as we 
require for those which have remained for ever un- 
touched and free, especially so, since (as we have already 
observed) it does absolutely appear, that those species, the 
external aspects of which have been thus artificially con- 
* Indications of the Creator (London, 1845), p. 163. 


trolled, are by constitution more tractile (and possess, 
therefore, more decided powers for aberration) than the 
rest. Whether traces of design may be recognized in 
this circumstance, or whether those forms were originally 
selected by man on account of their pliability, it is not 
for me to conjecture ; nevertheless, the first of these in- 
ferences is the one which J should, myself, be a priori 
inclined to subscribe to. 

In examining, however, this enigma, of the limits 
within which variation is (as such) to be recognized; it 
should never be forgotten, that it is possible for those 
boundaries to be absolutely and critically marked out 
even where we are not able to discern them : so that the 
difficulty which a few domesticated creatures of a singu- 
larly flexible organization present, should not unneces- 
sarily predispose us to dispute the question in its larger 
and more general bearings. Nor should we be unmind- 
ful that (as Sir Charles Lyell has aptly suggested) " some 
mere varieties present greater differences, inter se, than 
do many individuals of distinct species ;" for it is a truth 
of considerable importance, and one which may help us 
out of many an apparent dilemma. 

But, whatever be the several ranges within which the 
members of the organic creation are free to vary; we 
are positively certain that, unless the definition of a species, 
as involving relationship, be more than a delusion or ro- 
mance, their circumferences are of necessity real, and 
must be indicated somewhere, as strictly, moreover, and 
rigidly, as it is possible for anything in Nature to be 



chalked out. The whole problem, in that case, does in 
effect resolve itself to this, Where, and how, are the 
lines of demarcation to be drawn ? No amount of incon- 
stancy, provided its limits be fixed, is irreconcilable with 
the doctrine of specific similitudes. Like the ever- 
shifting curves which the white foam of the untiring 
tide describes upon the shore, races may ebb and flow ; 
but they have their boundaries, in either direction, 
beyond which they can never pass. And thus in every 
species we may detect, to a greater or less extent, the 
emblem of instability and permanence combined : al- 
though perceived, when inquired into, to be fickle and 
fluctuating in their component parts, in their general 
outline they remain steadfast and unaltered, as of old, 

" Still changing, yet unchanged ; still doom'd to feel 
Endless mutation, in perpetual rest." 


Aberration, perhaps indicated universally, 16, 17, 18. 

Aborigines, insect, unimportant for climatal modifications, 25, 26, 27. 

Acalles, the Canarian type of, apparent on the Salvages and De- 
zertas, 124. 

Neptunus, Woll., perhaps a state of A. argillosus, 124. 

Achatina Eulima, Lowe, its extinction in Porto Santo, 131. 

Achenium Hartungii, Heer, a form of A. depressum, 65. 

Acherontia Atropos, Linn., its introduction into Madeira perhaps 
recent, 74. 

Adimonia, the capture of, out at sea, 150. 

Aepus marinus, Strom., pallid hue of, 64. 

Robinii, Lab., pallid hue of, 64. 

Agabus bipustulatus, Linn., unaffected by climate, 31. 

Alligators, their peculiarity to S. America, 143. 

Alpine species, some peculiarly so, 40. 

Altitude and latitude, sometimes reciprocal, 35, 114. 

Amycterus, its concentration in Australia, 143. 

Amyot, M., his 'Methode Mononomique,' 164. 

Analogies, Lord Bacon on the importance of, 13 ; why necessary to 
be studied, 14. 

Analogy, argument from, 10, 11, 12. 

Anchomenus marginatus, Linn., slightly modified in Madeira, 38. 

Andes, dissimilarity of the fauna on the opposite sides of the, 146. 

Anobium striatum, Oliv., unaffected by climate, 31. 

Antennae, joints of, said occasionally to vary, 96. 

Anthicus bimaculatus, Illig., variability of, near the sea, 63. 

fenestratus, Schmidt, slightly modified in Madeira, 38. 

humilis, Germ., variability of, in salt places, 63. 

instabilis, Hoffm., pallid hue of, 64. 

Anthonomus ater, Mshm, very small in Lundy Island, 58, 73. 

Aphelocheirus (sstivalis, Fabr., the hemelytra of, sometimes fully 
developed, 100. 

Aphodius nitidulus, Fabr., paler in Madeira than in Europe gene- 
rally, 65. 


196 INDEX. 

Aphodius plagiatus, Linn., usually black in England, 61 ; two 
distinct states of, indicated, 105. 

Apocyrtus, its concentration in the Philippine Islands, 143. 

Apotomus, common to Madeira and Sicily, 139. 

Argutor, always apterous in Madeira, 82 ; trophi of, almost iden- 
tical with those of Calathus, 175. 

Armadillos, their peculiarity to S. America, 143. 

Armitage, Mr., on Cicindelafasciatopunctata from Mount Oly mpus,4 1 . 

Arrangement, a lineal one is not indicated in Nature, 163. 

Atlantic continent, Prof. E. Forbes on the former existence of, 137- 

Atlantis of the ancients, the impossibility of its being identified 
with a former Atlantic region, 140 ; perhaps the New World, 141. 

Atlantis, the genus, a modification of Laparocerus, 143. 

Azores, the colonization of, by two Madeiran Helices, 133. 

Bacon, Lord, on the importance of analogies, 13; on the Atlantis 
of the ancients, 141 ; on the necessity of observation for forming 
science, 159. 

Banksias, their concentration in Australia, 142. 

Barriers, natural, the difference between primary and recent, 145 ; 
their hindrance to insect diffusion, 145. 

Bembidium Atlanticum, Woll., paler in Porto Santo than in Ma- 
deira, 66 ; the variations to which it is subject, 107, 108. 
bistriatum, Dufts., paler in saline districts, 62. 

- ephippium, Mshm, pallid hue of, 64. 

obtusum, Sturm, varies in southern latitudes, 33. 
pallidipenne, Illig., pallid hue of, 64. 

- saxatile, Gyll., variety of, on the south coast of England, 60. 

- Schmidtii, Woll., perhaps a state of B. callosum, 66. 
scutellare, Germ., pallid hue of, 64. 

tabellatum, Woll., perhaps a state of B. tibiale, 66. 
Berginus, common to Madeira and Sicily, 139. 

Black Rat, nearly exterminated in England, 178. 
Blemus areolatus, Creutz., paler in brackish places, 62. 
Bolitochara assimilis, Kby, smallness of, in the Scilly Islands, 73. 
Boromorphus, common to Madeira and Sicily, 139. 
Brachinus crepitans, Linn., two distinct sizes of, frequently indi- 
cated, 105. 

Bradycellusfulvus, Mshm, apterous in Madeira, 85. 
Bread-fruit Trees, their peculiarity to the South Sea Islands, 142. 

Calathus, apterous in Madeira, 82; its trophi almost identical with 

those of Pristonychus, 175. 
complanatus , Roll., varies from altitude, 39; variety of, on one 

of the Madeira Islands, 88. 
fuscus, Fabr., slightly modified in Madeira, 38, 85. 

INDEX. 197 

Calathus melanocephalus, Linn., smallness of, in the Scilly Islands, 


mollis, Mshm, variable in its wings, 43 ; lurid colour of, 64. 

Calcareous soils, effect of, on the aspect of insects, 66. 

Calceolarias, their concentration on the Andes, 142. 

Calosoma, a species of, ten miles from shore, 147 ; the genus, merges 

gradually into Carabus, 175. 

Syncophanta, Linn., its power of crossing the sea, 147. 

Canary Islands, migratory direction of their insect population, 119. 
Carabidee, inconstant in their organs of flight, 43 ; family of, nearly 

similar throughout in its oral organs, 174. 
Carpophilus hemipterus, Linn., unaffected by climate, 31. 
Caulotrupis conicollis, Woll., large size of, on one of the Madeira 

Islands, 88, 109. 

lucifugus, Woll., varies from isolation, 90, 109. 

Causes, never final ones which we investigate, 191. 

Centrinus, its concentration in S. America, 143. 

Ceutorhynchus contractus, Mshm, smallness of, in Lundy Island, 

59, 73. 

Cholovocera, common to Madeira and Sicily, 139. 
Choreius ineptus, Westw., on a winged state of, 44. 
Chorosoma miriforme, the development of the wings of, 100. 
Chrysomela, apterous in Madeira, 82. 
Chrysomelce, vary from altitude, 41. 
ChrysomelidfB, almost absent in Tierra del Fuego, 47. 
Cicindela fasciatopunctata, Germ., a state of C. sylvatica, 41. 
Cicindelidce, often variable, 4 1 . 
Cillenum laterale, Sam., lurid hue of, 64. 
Cimex apterus, Linn., the development of the wings of, 100. 

lectularius, Linn., on the development of the wings of, 45. 

Cistela sulphured, Linn., its variability near the sea, 60. 
Clausilia deltostoma, Lowe, a Porto-Santan form of, 134. 
Climatal modifications significant, although small, 42. 
Climate, not important as a disturbing cause, 23, 24, 31, 32, 42. 
Clouded-yellow Butterfly, unaffected by climate, 31. 
Clypeaster pusillus, Gyll., differs slightly in Madeira, 65. 
Coast, inconstancy of insects in the vicinity of the, 57- 
Coccinella 7-punctata, Linn., unaffected by climate, 31. 
Colias Edusa, Fabr., unaffected by climate, 31. 
Colour, its inconstancy in insects found near the sea, 57, 58. 

of insects, affected by isolation, 88. 

Colymbetes, a species of, captured forty-five miles from shore, 149,150. 
Compensation, generally apparent when an insect is deprived of an 

organ or sense, 81. 

Coranus subapterus, Curt., the development of the wings of, 101. 
Cordillera, Mr. Darwin on the fauna of the, 145. 

198 INDEX. 

Corylophus, apterous in Madeira, 82. 

Criomorphus, Curtis, referable to the genus Delphax, 45. 

Cyclostoma lucidum, Lowe, its extinction in Porto Santo, 131. 

Cynthia Cardui, Linn., unaffected by climate, 32. 

Cynucus, a species of, seventeen miles from shore, 150. 

Cyrtonota, its concentration in S. America, 143. 

Darwin, Mr., on the fauna of the Galapagos, 23 ; relative propor- 
tions of the insect tribes in the tropics, 28, 29 ; on the insects of 
Tierra del Fuego, 47 ; on the natural features of Tierra del Fuego, 
50 ; on the insects of Keeling Island, 55 ; on the insects of St. 
Helena, 55 ; on the insects of Ascension, 55 ; on the apterous 
condition of insular species, 86 ; on the fauna of the Cordillera, 
145 ; on a Calosoma captured at sea, 147 ; on insects captured 
in the sea, 149, 150; on the disappearance of animals before 
more powerful ones than themselves, 178. 

Dawson, Rev. J. F., on a variety of Bembidium soxatile, 60. 

Definition of the term ' species,' 4 ; of the term ' variety,' 4. 

Delphax, on the development of the wings of, 45. 

Dermestes vulpinus, Fabr., unaffected by climate, 31. 

Deucalion, its occurrence on the Salvages and Dezertas, 125. 

Desertarum, Woll., its sedentary nature, 125, 126, 127. 

Dichelus, its concentration in S. Africa, 143. 

Differences, when to be regarded as specific, 6 ; too exclusively 
studied, 12. 

Diffusion, various means of, which operate on the insect tribes, 148. 

Disturbing agents, Prof. Henfrey on, 8. 

Ditylus, the same type of, indicated in the Canaries and Salvages, 124. 

Domesticated animals, pliable nature of, 187, 192. 

Dromius arenicola, Woll., representative of D. obscuroguttatus, 66. 

fasciatus, Gyll., its paleness near the sea, 63. 

negrita, Woll., perhaps an ultimate state of D. glabratus, 85. 

obscuroguttatus, Dufts., its changes in Madeira, 36, 37, 38 ; 

apterous in Madeira, 84. 

sigma, Rossi, its colour affected by isolation, 88, 89. 

Elevation, sometimes corresponds with latitude, 35, 114. 
Ellipsodes glabratus, Fabr., singular variety of, on one of the Ma- 
deira Islands, 88, 109. 

Elytra, connateness of, a variable character, 96. 
' Endemic,' to what species the term is applicable, 118. 
Entomology, the study of, does not necessarily cramp the mind, 111. 
Ephistemus, apterous in Madeira, 82. 
Eucalypti, their concentration in Australia, 142. 
Eunectes sticticus, Linn., unaffected by climate, 31. 
Euphorbias, their concentration in Southern Africa, 142. 

INDEX. 199 

Eurygnathus Latreillei, Lap., variety of, on one of the Madeira 

Islands, 88, 109. 

Exceptions, not be allowed to negative a law, 72, 73. 
Extinction of species, as indicated in the Madeiran Helices, 131 ; 

the only cause by which genera may be abruptly defined, 176. 

Forbes, Prof. E., on the origin of the British animals and plants, 
130; his epochs of migration of the British animals and plants, 
136; on the existence of a former Atlantic continent, 137- 

Forests, the hindrance which they offer to insect-diffusion, 154. 

" Fortunate Islands " of the ancients, probably the Canarian group, 

Galapagos, fauna of, 23. 

Genera, the nature of, often misunderstood, 160 ; a familiar expla- 
nation of, 160, 161, 162; cannot be abrupt except Irom accident, 
169; how to be denned, 169; the types of, usually situated 
towards the centres of the several groups, 170; the types of, 
usually evenly balanced in their structural characters, 171, 1/2; 
may be abruptly defined from accidental causes, 176, 177- 

Generic areas, an important feature throughout Nature, 130, 141, 184. 

Geology, a necessary item in the study of insect-diffusion, 113. 

Germanic plains, the, probably a primary area of diffusion, 130. 

Gerris, on the development of the wings of, 100. 

Gould, Mr., on the Swallows of Malta, 102. 

Gymnaetron, blood-red dashes characteristic of, 62. 

Campanula, Linn., its smallness on the Cornish coast, 58. 

Veronica, Germ., a variety of G. niaer, 62. 

Hadrus illotus, Woll., perhaps a form of H. cinerascens, 66. 

Haliplus obliquus, Gyll., dark state of, in Ireland, 67. 

Haltica exoleta, Fabr., its variability on the coast, 59. 

Harcourt, Mr., on the discovery of Madeira, 49, 50. 

Harpalus vividus, Dej., changes to which it is subject, 67, 68, 69; 
variable in the connateness of its elytra, 96, 97. 

Hegeter, its maximum attained in the Canaries, 120. 

elongatus, Oliv., its migration from the Canaries, 120; of a 

more adaptive nature than its allies, 121. 

latebricola, Woll., its occurrence in the Salvages, 120. 

Helices, have often two distinct states, 106; many of them repre- 
sentative in the Madeira Islands, 128, 129 ; those in the Madeiras 
chiefly of slow migratory powers, 130, 131. 

Helix attrita, Lowe, its local character, 132. 

Bowdichiana, Fer., perhaps a gigantic state of H. punctulata, 


calculus, Lowe, sedentary nature of, 132. 

200 INDEX. 

Helix commixta, Lowe, sedentary nature of, 132. 
coronata, Desh., its peculiarity to Porto Santo, 128 ; its occur- 
rence beneath the surface of the ground, 131. 

coronula, Lowe, its peculiarity to the Southern Dezerta, 128. 

Delphinula, Lowe, the Madeiran representative of H. tectifor- 

mis in Porto Santo, 129. 
discina, Lowe, a form of H. polymorpha, 133. 

erubescens, Lowe, its powers of diffusion greater than those of 

j. *_; 

its allies, 133; sensitive to external influences, 134. 

fluctuosa, Lowe, its extinction in Porto Santo, 131. 

hirsuta, Say, two distinct states of, 106. 

lapicida, Linn., its extinction in Porto Santo, 131. 

- latens, Lowe, the Madeiran representative of H. obtecta in 
Porto Santo, 129. 

lincta, Lowe, the common Madeiran form of H. polymorpha, 

Lowei, Pfr., perhaps a gigantic state of H. Portosanctana, 106. 

papilio, Lowe, a form of H. polymorpha, 133. 

paupercula, Lowe, its powers of diffusion greater than those 
of its allies, 133. 

polymorpha, Lowe, sensitive to external influences, and of 

great diffusive powers, 133. 

Portosanctana, Sow., its peculiarity to Porto Santo, 129. 

pulvinata, Lowe, a form of H. polymorpha, 133. 

saccharata, Lowe, a local state of H. polymorpha, 134. 

senilis, Lowe, the Dezertan form of H. polymorpha, 134. 

squalida, Lowe, the Madeiran representative of H. depauperata 

in Porto Santo, 129. 

tiarella, Webb, its sedentary nature, 128. 

- undata, Lowe, its peculiarity to Madeira proper, 129. 
Vulcania, Lowe, its peculiarity to the Dezertas, 129. 

Wollastoni, Lowe, sedentary nature of, 1 32. 

Helobia nivalis, Payk., perhaps a state of H. brevicollis, 40. 
Helops, always apterous in Madeira, 82. 

confer tus, Woll., varies from altitude, 39. 

futilis, Woll., varies from isolation, 109. 

testaceus, Kiist., pallid hue of, 64. 

Vulcanus, Woll., large size of, on one of the Madeira Islands, 88. 

Henfrey, Prof., on disturbing agents, 8. 

Herschel, Sir John, on the requisites for an observer, 12. 
Hipparchia Semele, Linn., has a distinct aspect in Madeira, 34. 
Hipporhinus, its concentration in S. Africa, 143. 
Holme, Mr., on Olisthopus rotundatus in the Scilly Islands, 58, 102; 

on a winged state of Phosphuga atrata, 102. 
Holoparamecus, common to Madeira and Sicily, 139. 
niger, Aube, different in Madeira and Sicily, 33. 

INDEX. 201 

Hooker, Dr., on the insects of Kerguelen's Land, 86. 

Humboldt, his notice of Sphinxes and flies high up on the Andes, 149. 

Humming-Birds, their peculiarity to S. America and the W. Indies, 


Hydrobius, apterous in Madeira, 82 ; the capture of, out at sea, 150. 
Hydrometridce, on the development of the wings of, 100. 
Hydroporus, the capture of, out at sea, 150. 

confluens, Fabr., unaffected by climate, 31. 

Hypsonotus, its concentration in S. America, 143. 

Influence of climate not important, 23. 
Insect-aberration, perhaps a universal fact, 16, 17, 18. 
Insulcs FortunatcB of Juba, probably the Canarian Group, 141. 
Ireland, poverty of the fauna of, 52, 53; the south-west of, has 

something in common with Madeira, 139. 
Islands, faunas of, often too greatly magnified, 70 ; the species of, 

generally more isolated in their structure than those of continents, 


Isolation, effects of, on insect-stature, 71. 

Ixias, their concentration in Southern Africa, 142. 

Kangaroos, their concentration in Australia, 142. 

Kerguelen's Land, insects of, 86. 

Kirby, Rev. W., on insects washed up on the Suffolk coast, 147- 

L(smophl(Bus pusillus, Schb'nh., unaffected by climate, 31. 
Lamprias chlorocephalus, Ent. H., two distinct sizes of, frequently 

indicated, 105. 
Laparocerus mono, Schb'nh., large size of, on one of the Madeira 

Islands, 88. 

Latitude and altitude, sometimes reciprocal, 35. 
Leistus montanus, Steph., has been supposed to be equal toL.fulvi- 

barbis, 40. 

Lemur, its peculiarity to Madagascar, 143. 
Litargus, common to Madeira and Sicily, 139. 
Lixus anyustatus, Fabr., unaffected by climate, 31. 
Localities, some naturally more productive than others, 53, 54. 
Longitarsus, the native species of, apterous in Madeira, 82. 
Loricera, apterous in Madeira, 82. 

Lowe, Rev. R. T., his capture of Deucalion Desert arum, 127. 
Lundy Island, smallness of the insects in, 58, 59 ; occurrence of the 

Black Rat in, 178. 

Lyccena Phlceas, Linn., darker in Madeira than in England, 34. 
Lvell, Sir Charles, on Helix hirsuta, 106 ; on the fossil period of 

the Madeiran Helices, 129 ; on insects washed up on the shore, 

148 ; on the effect of gales in the transportation of insects, 148 ; 

202 INDEX. 

on the effects of a volcanic eruption in destroying species, 1 79 ; on 
the flexible nature of certain animals and plants, 187 ; on the greater 
differences which varieties often present than do species, 193. 
Lygceus brevipennis,, on the development of the wings of, 

Macronota, its peculiarity to Java, 143. 

Madeira, has some features in common with Tierra del Fuego, 48, 
49, 50, 51 ; former state of, 48, 49 ; great fire on the southern 
side of, 49 ; origin of the name of, 50 ; the insects of, 55 ; the 
tendency of its insects to become apterous, 82 ; the migratory 
direction of its insect population, 119; the local nature of its 
various species, 152, 153. 

Magnolias, their concentration in Central America, 142. 

Malta, Mr. Gould on the birds of, 102. 

Malthodes Kiesenwetteri, Woll., perhaps a state of M. brevicollis, 66. 

Man, agency of, in the destruction of species, 179. 

Mantura Chrysanthemi, Ent. H., variability of, in Lundy Island, 59. 

Marsupialia, their concentration in Australia, 142. 

Mesembryanthemums, their concentration in Southern Africa, 142. 

Mesites, a modification of Cossonus, 144. 

Maderensis, Woll., its near relationship to the M. Tardii, 141. 

Tardii, Curtis, its variability near the coast, 58. 

'Methode Mononomique,' the unsoundness of, 1.64 168. 

Migratory powers, slowness of, in the Madeiran Helices, 130 132. 

progress, direction of, in the Madeiran animals, 120, 135. 

Mimosas, their concentration in Australia, 142. 

Mollusca, Terrestrial, often present two distinct states, 106. 

Moluris, its concentration in S. Africa, 143. 

Monochelus, its concentration in S. Africa, 143. 

Mountain-chains, their hindrance to insect -diffusion, 145. 

Mountain-tops, either very prolific in insect life, or else barren, 115. 

Mus Rattus, almost exterminated in England, 178. 

Mycetoporus pronus, Erichs., two distinct states of, indicated, 106. 

Myrtles, their concentration in Australia, 142. 

Naturalist, the, what his province to investigate, 158. 

Nature, not irregular because presenting occasional anomalies, 94. 

Naupactus, its concentration in S. America, 143. 

Nebria complanata, Linn., unusually pale near Bordeaux, 33 ; pallid 

hue of, 64. 
New World, some of its insects perhaps but states of those of the 

Old, 37. 

Nomenclature, a binomial system the only true one, 164, 168. 
Notaphus, the capture of, out at sea, 150. 
Notiophili, extremely variable, 40. 

INDEX. 203 

Notiophilus geminatus, Dej., large size of, on one of the Madeira 
Islands, 88. 

Observation, indispensable in natural science, 20, 159, 192. 

Ocean, the, its hindrance to insect-diffusion, 145. 

Ochthebius marinus, Payk., lurid hue of, 64. 

Olisthopus, apterous in Madeira, 82. 

Maderensis, Woll., large state of, on one of the Madeira Islands, 

88, 89. 
rotundatus, Payk., very small in the Scilly Islands, 58, 73 ; 

subapterous in the Scilly Islands, 102. 
Omaseus nigerrimus, Dej., a form of 0. aterrimus, 33. 
Omias Waterhousei, Woll., large state of, on one of the Madeira 

Islands, 88, 109. 

Oncocephalus griseus, development of the wings of, 101. 
Othius, apterous in Madeira, 82. 
Ourangs, their peculiarity to the Indian Islands, 143. 
Oxyomus, a modification of Apliodius, 144. 

Pachymerus brevipennis, the development of the wings of, 100. 

Pachyrhynchus, its concentration in the Philippine Islands, 143. 

Painted-Lady Butterfly, unaffected by climate, 32. 

Papilio Machaon, Linn., unaffected by climate, 31. 

Paropsis, its concentration in Australia, 143. 

Patagonia, insects of, distinct from those of Tierra del Fuego, 47, 48. 

Patrobus septentrionis, Dej., has been supposed to be a state of P. 
excavatus, 40. 

Pecteropus, its maximum attained in the Canaries, 124. 

Maderensis, Woll., varies from altitude, 39. 

rostratus, Woll., varies from isolation, 90. 

Pelargoniums, their concentration in Southern Africa, 142. 

Pelophila borealis, Payk., larger in Ireland than in the Orkneys, 33. 

Phaleria cadaverina, Fabr., pallid hue of, 64. 

Philhydrus melanocephalus, Oliv., two states of, frequently indicated, 

Phlceophagus, apterous in Madeira, 82. 

Phosjjhuffa atrata, Linn., taken with the wings developed, 102. 

subrotundata, Leach, the Irish form of the P. atrata, 33. 

Phytophaga, preponderance of, in the tropics, 28, 29. 

Pieris Brassicce, Linn., varies in Nepaul and Japan, 34. 

Pissodes notatus, Fabr., unaffected by climate, 30. 

Platyomus, its concentration in S. America, 143. 

Platyrrhini, their peculiarity to S. America, 143. 

Pogonus luridipennis, Germ., lurid hue of, 64. 

Pontia Brassicce, Linn., its introduction into Madeira probably re- 
cent, 74. 

204 INDEX. 

Porto Santo, origin of the name of, 49 ; a generic area of radiation 
for certain Helices, 130. 

Predacious insects, less numerous in the tropics, 28, 29. 

Prostemma guttula, Fabr., the development of the wings of, 100, 101 . 

Psylliodes, a variable species of, in Lundy Island, 60. 

erythrocephala, Linn., two distinct states of, frequently indi- 
cated, 105. 

marcida, Illig., pallid hue of, 64. 

nigricollis, Mshm, a pale state of the P. erythrocephala, 105. 

vehemens, "Woll., varies from isolation, 90. 

Pterostichus, its various divisions are natural ones, 175. 

Ptini, their stature affected by isolation, 74 ; which characters of, 
are the most constant, 104. 

Ptinus albopictus, Woll., its changes on the islands of the Madeiran 
Group, 75 77- 

Pupa, often two distinct states of, 106. 

Purpurarice of the ancients, probably the Madeiran Group, 141. 

Pyrenean region, the, perhaps a primary area of diffusion, 130. 

Reasoning, not sufficient of itself for the formation of science, 159. 

Red-Admiral Butterfly, its introduction into Madeira perhaps re- 
cent, 74. 

Reduviadce, on the development of the wings of a representative of 
the, 101. 

Representative species, exemplified by the Madeiran Helices, 128, 
129, 185; where frequently to be recognized, 183. 

Rhyzopertha pusilla, Fabr., unaffected by climate, 31. 

Rivers, their power of transporting insects along their course, 149. 

Saline spots, variation of insects in, 57. 

Salvages, occurrence of a Canarian form on the, 120, 124. 

Saprinus, a modification of Hister proper, 143. 

- nitidulus, Fabr., two distinct states of, indicated, 106. 
Scarabceus, the capture of, out at sea, 150. 
Scarites abbreviatas, Koll., large size of, on one of the Madeira 

Islands, 88 ; varies both from isolation and altitude, 91. 
Sciences, the, should assist rather than oppose each other, 155, 156. 
Scydmcenus Helferi, Schaum, smaller in Madeira than in Sicily, 65. 
Scymnus, an apterous species of, in Porto Santo, 82. 
Sea, inconstancy of insects in the vicinity of the, 57. 
Sicily, the fauna of, has much in common with that of Madeira, 139. 
Silpha atrata, Linn., presents a distinct state in Ireland, 33. 
Silybum Marianum, Grtn., its stalks the food of a Ptinus, 76. 
Similitudes, Lord Bacon on the importance of, 13. 
Sitonia gressoria, Illig., perhaps a form of the S. grisea, 33. 
Sitophilus granarius, Linn., unaffected by climate, 31. 

INDEX. 205 

Sitophilus oryzce, Linn., unaffected by climate, 31. 

Sloths, their peculiarity to S. America, 143. 

Species, definition of the term, 4 ; familiar explanation concerning 
the nature of, 161, 162 ; limitation of, how to be attempted, 192 ; 
limits of, real, though often difficult to trace out, 193 ; in a cer- 
tain sense both unstable and permanent, 194. 

Specific centres of creation, 5. 

Sphinx Convolvuli, Linn., its introduction into Madeira probably 
recent, 74. 

Spinola, on one of the Reduviadce, 101; on Oncoceplialus griseus, 

Stapelias, their concentration in Southern Africa, 142. 

States, large and small ones indicated in some insects, 105. 

Stature of insects, smaller in islands than on continents, 70. 

Stenolophus Skrimshiranus, Steph., perhaps a state of S. Teutonus, 

Stenus Heeri, Woll., two distinct states of, indicated, 106. 

Structural characters, seldom variable in the Insecta, 95. 

Subsidences, the effect of, on insect life, 114. 

Swallow-Tail Butterfly, unaffected by climate, 31. 

Syncalypta, apterous in Madeira, 82. 

Tachyporus nitidicollis, Steph., perhaps a state of T. obtusus, 33. 

Tarphii, their economy in the Madeira Group, 121. 

Tarphius, its maximum attained in Madeira proper, 121 ; common 

to Madeira and Sicily, 139. 

gibbulus, Germ., the Sicilian exponent of the genus, 123. 

Lowei, Woll., of a more adaptive nature than its allies, 122. 

Tarus, always apterous in Madeira, 82. 

lineatus, Schonh., assumes a distinct state in Madeira, 65. 

Telephorus testaceus, Linn., its variability in Lundy Island, 59. 
Thompson, Mr., on the reptiles of Ireland, England, and Belgium, 


Thorictus, common to Madeira and Sicily, 139. 
Tierra del Fuego, insects of, 47 ; has many characters in common 

with Madeira, 4851. 

Time, an important item in the question of modifications, 77- 
Toucans, their peculiarity to S. America and the W. Indies, 142. 
Transmutation-theory, uusoundness of the, 186 189; how it took 

its rise, 190. 
Trechus, always apterous in Madeira, 82. 

alticola, Woll., perhaps a state of T. custos, 39. 

lapidosus, Daws., pallid hue of, 64. 

Tree-Porcupines, their peculiarity to S. America, 143. 
Triboliumferrugineum, Fabr., unaffected by climate, 31. 
Trogosita mauritanica, Linn., unaffected by climate, 31. 

206 TXDEX. 

Tropics, exuberance of the, 27, 28 ; relative proportions of the insect 

tribes within the, 28, 29. 
Tychius, always apterous in Madeira, 82. 

Unity, indicated in the organic creation, 179, 180. 

Vanessa Atalanta, Linn., has a different aspect in N. America, 34 ; 

perhaps a recent introduction into Madeira, 74. 
Callirhoe, Fabr., smaller in Porto Santo than in Madeira, 73. 
Variation in the Insecta, a matter of experience, 7? 8, 15 ; probable 

from analogy, 15; perhaps indicated in every individual, 16, 17, 

18 ; restricted, 35. 
Variety, definition of the term, 4. 
Velia, on the development of the wings of, 100. 

Waterhouse, Mr., his opinion concerning generic types, 172. 

Westwood, Mr., on Papilio Machaon from the Himalayas, 32 ; on 
American specimens of Lyccena Phloeas, 34 ; on the effect of heat 
in developing the wings of insects, 44 ; on a winged state of 
Choreius ineptus, 44 ; on the development of the wings in Del- 
phax, 45 ; on a winged state of Cimex lectularius, 45 ; on Aphelo- 
cheirus cestivalis, 100; on the development of the wings of the 
Hydrometridee, 100; on Cimex apterus, 100; on Prostemma gut- 
tula and Coranus subapterus, 101 ; on the development of the 
wings of Lygceus brevipennis, 101. 

Whewell, Dr., on the natural causes which science has to investi- 
gate, 191. 

White-Cabbage Butterfly, varies in Nepaul and Japan, 34. 

Winds, the effects of, in the diffusion of insects, 148. 

Wings of insects, subject to undue development in hot seasons, 43 ; 
liable to become gradually obsolete in islands, 81 ; more variable 
than other organs, 97. 

Xenostrongylus, its geographical distribution, 124 ; common to 
Madeira and Sicily, 139. 

Zargus pellucidus, Woll., variety of, on one of the Madeira Islands, 



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