Feb. 3, 1870] 
MR. BATES'’S ADDRESS TO. THE 
ENTOMOLOGICAL SOCIETY 
[NX printing the following extracts from the address delivered to 
the Entomological Society on the 24th ult. by the President, 
Mr. H.W. Bates, we must express our regret that we cannot find 
space for the insertion of the whole of that able and interesting 
discourse. 
Referring to the ‘‘ Transactions” of the Society, Mr. Bates 
remarked :—The volume for the past year comprises twenty- 
seven memoirs, of which twenty-five belong to the department of 
systematic or descriptive Entomology, and two only—welcome 
contributions from Mr. Jenner Weir and Mr. Butler, on the 
selection of insects as food by insectivorous animals—to other 
branches of the science. To those who might object that too 
large a share of our work is occupied by mere descriptions, I 
would remark that many original and valuable observations on 
relationships, geographical distribution, and other deeply inte- 
resting philosophical questions, are contained in some of our 
descriptive papers. In fact, it is not at all a necessary conse- 
quence that a descriptive treatise should be nothing more than a 
string of dry definitions. It will become, I hope, more and 
more the practice of entomologists to give, together with their 
descriptions, the new data on relationships, distribution, com- 
parison of faunas, &c., which the handling of such subjects most 
usually brings forth. 
In speaking of the contributions of importance which have 
been made to the science in this country outside the Entomo- 
logical Society, the President alluded to the examination by Mr. 
Wollaston of the largest collection of insects which has yet been 
made in St. Helena. This suggested the following observations : 
As you are aware, the great interest which attaches to the fauna 
and flora of oceanic islands arises from the problems involved in 
the modes in which they obtained their species of animals and 
plants, and those are rendered more complicated by the exist- 
ence on some island of anomalous forms, representative, it is 
considered, of types ages ago extinct on continents. Such 
islands, however, differ greatly from each other as to degree of 
peculiarity in their productions ; and it often happens that species 
identical, or nearly so, with those found in the nearest continent, 
form nearly the whole of their present inhabitants. Thus the 
investigation of the origin of their faunas and floras is necessarily 
exceedingly complex. Geology has to be invoked to ascertain 
whether the islands are of recent or ancient elevation above the 
sea-surface, and whether the supposition is admissible of a 
recent connection with the nearest continental land. Oceanic 
hydrography, deep-sea soundings, and the force and direction 
of currents and winds, have to be studied in reference tofthe 
depth of the surrounding seas ; for these must all be taken into 
consideration in discussions on the probable derivation of the 
curious mixture of forms which is often found on these isolated 
spots. On the other hand, it must be noted that the fauna and 
flora themselves throw light on the geographical and geological 
relations of the islands to the nearest land. In fact, the classifi- 
cation of islands into oceanic and continental, is founded quite as 
much on resemblance or difference in organic productions, 
between islands and the mainland, as on relative proximity. 
Thus Great Britain is classed as a continental island, quite as 
much because its fauna and flora are nearly identical with those 
of continental Europe as because it is separated only by a shal- 
low sea, and is now known to have been actually connected in 
recent geological times. In these investigations entomology is 
now generally admitted to have great importance, owing to the 
large number and variety of species which it offers, as elements 
in the elaborate comparisons which have to be instituted. 
The following remarks well illustrate the high scientific im- 
portance of studying the geographical distribution of insect life :— 
The idea of the value of localities in connection with specimens 
or species, with some entomologists, I am afraid does not reach 
very far. They like to know in what countries the different forms 
are found, and perhaps, as in French collections, show the 
distribution by writing the specific names in their cabinets on 
labels coloured according to the part of the world the species 
inhabit ; the primary divisions of the world, as Europe, North 
and South America, Africa, Australia, perhaps the West Indies, 
and so forth, being considered sufficient. This brings out the 
leading facts of distribution very well, such as the restriction 
of many genera and groups of genera to each of the great 
divisions, and the distinctive facies which all the products 
from one region possess; but we seldom see it carried 
NATURE 
Sey 
further, and it remains a pretty association of geography with 
natural history, and no more. Results infinitely more suggestive 
are brought about if the student labels each sfecimen with its 
locality, instead of recording it on the ticket which bears the 
specific name placed below all the specimens, and if he is fortunate 
enough to be able to amass a large suite of specimens, accurately so 
ticketed, of genera abounding in local varieties and closely-allied 
species, indications of the conditions under which varieties, local 
races, and perhaps species, are formed in nature, are revealed by 
this method, and a field of investigation is opened which connects 
the study of a few insect species with some of the most difficult 
problems that are now engaging the attention of philosophers. The 
most common event that happens, when a student works at a series 
of species in this way, is the discovery that even the most constant 
species vary in some parts of their area of distribution ; the next, 
that a small well-marked difference in a species is generally a local 
difference, and embraces all the individuals of the district in which 
it occurs. As the collection increases, further curious facts come 
out. It is found, for instance, that some highly-variable species 
give rise to one set of varieties in one area, another distinctly 
different set in another area, and so on; and further, that in 
some areas one, or perhaps more, of these variations will be 
better marked than, and preponderate in number over, the other 
varieties of the same species. Still further, it is found that in 
some districts one sych variety alone occurs, having apparently 
prevailed over all the others. To be properly impressed, how- 
ever, with the great truth and reality of these facts, the student 
should himself have travelled as an entomological collector over 
an extent of country embraced by many local varieties of vari- 
able species ; otherwise his attention will not be sufficiently 
excited to the curious facts nature presents to him, and he will 
not take the trouble to amass and obtain the exact localities of 
numerous specimens of common variable species. Perhaps the 
most important result of this attention to distribution of varieties 
is, that a fine gradation of forms or degrees of variation will be 
found, from the ‘‘sport” or variety, such as is liable to be pro- 
duced in the same brood, to the well-segregated race living in 
company with another race referable to the same stock. As 
such, most authors, perhaps rightly, consider these latter 
as good and true species; and thus the formation of species 
out of mere variations is illustrated by the facts of geographical 
distribution. 
But it is not this branch of the subject with which we are so 
much concerned, when we wish to compare the productions of 
the different Andean valieys and their vertical ranges, as that 
relating to the nature of barriers to distribution. It has been 
received as a principle in zoological and botanical geography, that 
grand physical barriers, such as mountain ranges, form an impas- 
sable limit to the faunas and floras of the plains on each side of 
them. It is repeated, in almost every manual of physical geogra- 
phy, after Humboldt, who, I believe, was the originator of the 
statement, that the species are all different on the two sides of the 
Andes of South America. Such a fact, if well established, would 
be interesting in many ways. First, it would throw light on the 
geology of the country, as proving that the Andes must have 
existed as a ridge, sufficiently lofty to prevent the creatures of 
the plains crossing it, before the origin of the species which now 
people the plains on each side. Now, it is possible that this 
broad and important generalisation may have been made on a 
too slender foundation of facts. Of course, in those parts of 
the Pacific coast-region (two-thirds of the whole line within the 
tropics), where the conditions of soil, climate, and vegetation 
are totally different on the two sides of the Andes, no community 
of species is possible. A lofty mountain barrier would be here 
unnecessary, for a few steps of level road, in many parts of the 
world, would suffice to bring the traveller from the domain of 
one fauna to that of another—for instance, from an arid plain to 
a luxuriant forest along some river-valley. This would be a 
difference of ‘‘ station,” and not of area of distribution,—a dis- 
tinction long ago recognised in Botany. The question is, then, 
limited to this: In those parts of the Pacific coast-region, such 
as Guayaquil, where a humid forest-country exists on both sides 
of the Cordillera, are the species of the two sides entirely dis- 
tinct? This would test the efficacy of mountain-barriers better 
than almost any other case. For the species, at least of insects, 
which inhabit humid forests near the equator, are probably 
unable to exist at a higher altitude than 4,000 or 5,000 feet, and 
no pass over the Cordillera exists of half this depression, through- 
out the whole line of the Andes from Bolivia to the Isthmus 
of Darien. The species could not voluntarily pass over, nor by 
