436 
NATURE 
[March 30, 1871 

which are wholly apterous. Such phenomena undoubtedly show 
that there is something in Madeira which tends to abort wings ; 
and Mr. Wollaston was himself the first to suggest that it was 
connected with exposure to a stormy atmosphere. His further 
observation, that many of the winged species had wings more 
developed than usual, enabled Mr. Darwin to hit upon that 
beautiful explanation of the facts which commends itself to all 
who believe in the theory of Natural Selection, while Mr. Wol- 
laston himself admits it as fully accounting, teleologically, for the 
phenomena. That explanation briefly is, that the act of flying 
exposes insects to be blown out to sea and destroyed ; those which 
flew least therefore lived longest, and by this process the race 
became apterous. With species to whom flight was a necessity, 
on the other hand, the strongest-winged lived longest, and thus 
their wings became more and more developed in each succeeding 
generation. 
Now this view of the case enables us at once to explain some 
of the most striking gaps in the Madeiran coleopterous fauna. 
The Cicindelidz, for instance, are entirely absent ; and almost 
all the European species are winged insects of somewhat feeble 
flight, yet to whom flight is necessary. We can readily under- 
stand that such insects would be easily exterminated if they arrived 
singly or in small numbers ; though it is not so easy to under- 
stand why, in a forest-clad island, some of the sylvan species 
should not have found a home had the land ever been connected 
with a continent where they abound. Their total absence is, 
therefore, decidedly unfavourable to the theory of a land-con- 
nection with Europe. To the Melolonthidze and Cetoniidz, as 
well as the Eumolpidz and Galerucide, which are all wanting, 
the same argument will apply ; and also to the Elateridz and 
Buprestidz, which are represented each by one minute species. 
But if Madeira is the remains of a continent once continuous 
with the south of Europe and deriving its fauna from such con- 
tinuity, how are we to explain the absence of extensive genera 
very abundant in South Europe, and, from their being apterous, 
specially adapted to the peculiarities of Madeira? Such are 
Carabus, Lampyris, Pimelia, Akis, and many others. But these 
facts are all consistent with the theory of introduction across the 
sea. Apterous groups, however abundant on the continent, 
should, asa rule, be absent ; and I find that almost all the Euro- 
pean apterous genera are wanting, and among the few excep- 
tions there are some whose presence is easily explained and really 
prove the rule. We must remember, however, that the apterous 
condition, except in those cases where it is characteristic of an 
extensive group, is one of little stability or importance. There 
are species which are sometimes apterous and sometimes winged, 
and we may therefore be sure, that if any advantage was to be 
derived by either condition over the other, Natural Selection would 
very rapidly render it constant by the repeated survival of the 
favoured individuals. This is illustrated by the fact that we have 
winged and apterous species in the same genus, as well as winged 
and apterous genera in the same family. The coleopterous 
order being essentially winged, and the vast majority of its mem- 
bers being capable of flight, it is a presumption, if not almost a 
certainty, that all apterous varieties, species, or groups, have 
been derived from winged ancestors—comparatively recently in 
the case of the former, and at a more remote epoch as the charac- 
ter becomes more constant and attached to groups of higher clas- 
sificational value. 
Taking these principles as our guide, let us examine more 
closely the facts presented by the Madeiran Coleoptera, and their 
bearing on the rival theories as to their mode of introduction. 
There are a large number of European beetles belonging to the 
very varied genera and families which are apterous, and a large 
proportion of these inhabit the south of Europe and North Africa. 
Now, on the theory of land connection, there should be no 
marked absence of these groups ; on the contrary, apterous forms 
being especially adapted to Madeira, we should expect them to 
predominate. But, on the opposing theory of transmission 
across the sea, we should expect them to be wholly absent, or, if 
there are any exceptions, we should expect to be able to detect 
some special circumstances which might favour their trans- 
mission. A careful examination of Lacordaire’s ‘‘ Genera,” 
and of some works on European Coleoptera, has furnished me 
with the following list of genera which are wholly apterous, and 
which abound in South Europe and North Africa. 
Carabus possesses about eighty species in these regions ; but is 
wholly absent from Madeira. 
Thorictus has ten South European species, and one representa- 
tive in Madeira, which is an ants’-nest species. 

Rhizotrogus (Melolonthidz), twenty-seven species in Sicily 
and Algeria, the very country to which the Madeiran fauna is 
traced, yet it is wholly absent. 
Lampyris, Drilus, and Troglops (Malacoderms), of which the 
females are apterous, possess twenty-seven South European and 
North African species ; none in Madeira. 
Otiorhynchus, Brachycerus, and twenty other genera of Cur- 
culionidee, comprising more than 300 South European and North 
African species, are absent from Madeira, with two exceptions. 
One is the Zrachyphleus scaber, a widely-spread European insect 
often found in ants’ nests ; and this, with the case of the 7horictus, 
renders it probable that ants’-nest species have some unusual 
means of distribution, which are by no means difficult to con- 
ceive. Theother exception is that of the genus Acalles, which 
has a number of Madeiran species, all peculiar, and is very 
abundant in all the Atlantic islands. Now we have first to re- 
mark that Aca//es is an isolated form, but is allied to Cryprlorhyn- 
chus, which is often amply winged ; so that we may easily sup- 
pose that its introduction to Madeira took place before it became 
completely apterous in Europe. In the second place we have the 
fact, that many of the species are confined to peculiar herbaceous 
and shrubby plants, in the stems of which they undergo their 
transformations, and which habit would afford facilities for their 
occasional transmission in the egg or pupa state across a con- 
siderable width of ocean, while a fragment of dry stem con- 
taining egg or larva might possibly be carried some hundred 
miles or more by a hurricane. Such suppositions would not 
be admissible to account for numerous cases of transmission, 
but, as will be seen, this is almost the only example of a 
genus of large-sized apterous European beetles occurring in Ma- 
deira. 
Pimelia, Tentyria, Blaps, and eighteen other genera of Hete- 
romera, comprising about 550 species of South Europe and 
North Africa, are totally absent from Madeira, with the following 
interesting exceptions :—two common species of Alaps, which 
are admitted to have been introduced by human agency, and 
three species of AZe/oe, two of which are European and one pecu- 
liar. The means by which the apterous, sluggish, and bulky 
Meloes were introduced is sufficiently clear, when we remember 
that the minute active larvz attach themselves to bees, insects of 
exceedingly powerful flight, and more likely than perhaps any 
other to pass safely across 300 miles of ocean, ‘That the soli- 
tary exception to the absence of wholly apterous genera of 
European Heteromera from Madeira should be the genus JZe/oe, 
is, therefore, one of those critical facts which almost demonstrate 
that it is not to land-continuity with the continent that the island 
owes its insect fauna. 
Timarcha.—This, the only important apterous genus of Chry- 
somelidze, is especially abundant in Spain and Algeria, and 
possesses forty-four South European and North African species ; 
yet it is unknown in Madeira. 
The occurrence of two isolated European species of charac- 
teristic Atlantic apterous genera—Tarphius and Hegeter—may 
seem to favour the opposite theory. The Zurphius gibbulus occurs 
in Sicily, and is the only European species of the genus,of which 
about forty inhabit the Atlantic islands. It is most nearly allied 
to the smallest of the Madeiran species, 7: Zowe?, which is 
abundant among lichen on weather-beathen rocks, and even 
ascends in the forest regions to the highest branches of the trees, 
These habits, with its minute size, are all in favour of this species, 
or some ancestral allied form, having been carried across by the 
winds or waves, thus transferring to Europe one of the peculiar 
types elaborated in the Atlantic isles. The Hegister tristis is an 
analagous case, this species of an otherwise exclusively Atlantic 
genus having occured on the opposite coast of Africa. These in- 
stances will furnish a reply to one of Mr. Murray’s difficulties, — 
that all the migration has been in one direction, from Europe 
to Madeira, never from Madeira to the continent,—a difficulty, 
it may be remarked, which is wholly founded on an unproved 
and unprovable assumption; for how can it be determined 
that, in the case of Acadles for example, the genus had not 
been first developed in the Atlantic islands and then trans- 
ferred to Europe, instead of the reverse? It is always 
assumed to have been the other way, but I am not aware 
that any proof can be obtained that it was so, and it is 
inadmissible to take this unproved assumption, and base an argu- 
ment upon it as if it were an established fact. : 
We will next consider the facts presented by the distribution 
of those species of Coleoptera which range from Madeira to 
Europe, or to any of the other Atlantic islands. If their distri- 
