CONCLUSION

Let us summarize what has been presented in this work. It has been possible as a result of investigations of the insects on the Kuril archipelago to identify and determine more precisely the faunistic composition of the principal taxonomic groups of insects encountered on the islands, to disclose the general character of the Kuril entomofauna, its faunistic, ecological, and biogeocenotic features, and its origin and pathways of development, as well as to distinguish zoogeographical regions within the limits of the Range on the basis of a zoogeographical analysis of the entomofauna.

A great deal of faunistic material was analyzed in the study of the Kuril entomofauna, the analysis of which presented major difficulties, since a substantial proportion of the species belongs to the Japanese fauna. In connection with the fact that it was not possible to analyze all groups of insects to an equal degree for various reasons, only several systematic groups of various taxonomic levels (superorders, orders, suborders, families, genera) were chosen for detailed review. The completeness of the analysis of the collected materials, the extent of previous study of various groups and its scope, as well as the diversity of ecological associations were taken into account in the process.

In addition to a detailed review of the leading groups, a general characterization of the entomofauna, containing a list of all orders and families of insects known on the Kuril Islands, is provided in the study. Twenty-one orders of insects have been recorded on the Kuril Range at the present time, including 2,882 species (the number is far from exhaustive). The question of the total scope of the Kuril entomofauna remains thus far an open one, since the lower insects, the inhabitants of the soil and forest litter, remain nearly unstudied here, and orders such as the may flies, stone flies, copeognaths, bird lice, thrips, fleas, dipterans (with the exception of particular families), and some others are insufficiently studied. As a result of our investigations the number of species known on the Kurils has increased by 965. In the order of coleopterans alone, 17 families, previously unknown for this region, have been added. Several new genera, a number of new species (from various groups), and a large number of subspecies forms have been described on the basis of our collections. In addition, many genera and species previously unknown to the fauna of the USSR have been observed.

It was established, on the basis of a study of the distribution of the insects over the Kuril Range, that the entomofauna is unevenly distributed across the archipelago. The greatest diversity of species and the number of southern forms is observed on the southern islands, especially on Kunashir; there are substantially fewer of them on Iturup and Shikotan. In the central part of the Range, the number of species falls sharply, and the maximal impoverishment of the entomofauna is created; it is enriched somewhat on the northern islands due to an influx of Kamchatka species. The disposition of insects is also somewhat uneven within the limits of particular islands, and depends on the influence of local climatic conditions, first and foremost on the location of warm and cold marine currents bathing the Okhotsk and Pacific Ocean littorals, as a result of which the southern thermophilic species are concentrated on the western littoral. In addition to general climatological factors, local areas having their own microclimatic conditions, in which distinctive complexes of insects are formed, are of considerable significance on the Kuril Islands.

On the Southern Kuril Islands (within the limits of the dark coniferous-broadleaved forests of the southwest coast of Kunashir and near hot springs), groups of animals have been discovered which may be regarded as relicts, evidently preserved in little-altered form since preglacial time. It has become clear that some features which distinguish it from the entomofauna of the continent are characteristic of the Kuril entomofauna: appreciable impoverishment of species and genera, and sometimes the complete absence of some groups, the limited number of mass species, the absence of foci of mass reproduction of insects over large areas and at the same time on several islands. As a rule, only isolated species multiply en masse, but do so on limited areas within the limits of one island, while on neighboring islands these species are scanty or even rare. The leaf-beetle Clitena fuscipennis Jac. may serve as an example of the mass species on Iturup, the butterfly Neope gashkewischi Mén. on Kunashir, and the bamboo aphid on Urup and Iturup.

The phenological periods of development in the majority of species on the islands lag behind by approximately a month by comparison with continental regions of similar latitude. The time of mass flight falls as a rule in the second half of July-first half of August, while in isolated southern forms, it falls as a rule at the end of August-beginning of September. Often the occurrence of the same phases of development in the very same species of insects commences at different times on opposite coasts of islands. Some species (for example, leaf-rollers) generate a second, summer, diapause in the period of the summer rains under the conditions of the islands. This occurs under the influence of a cool marine climate, a protracted cold spring, and a prolonged warm autumn.

The constant high humidity and moderate temperatures, as it were, even out the climatic conditions at different altitudes. As a result, the vertical zonation on the islands is inconspicuous among various groups of animals (including insects), as well as among plants. The influence of the marine climate is also reflected in the ecological structure of the Kuril entomofauna, among which mesophilic, hygromesophilic, and hygrophilic species predominate, while the xeromesophils are represented only by a small group of insects which are concentrated on near-fumarole, relatively dry meadows areas and stony scree. The high humidity permits many moisture-loving animals (terrestrial and some marine crustaceans, terrestrial molluscs, and of the insects, the leafhoppers-froghoppers) to live an open mode of life and to multiply in large numbers.

The limited number of light-requiring forms, especially heliophils, and a change in the behavior of some nocturnal insects, which here fly in the daytime, even in the sunlight, is typical of the insects of the Kuril Islands; this is evidently brought about by the lowered solar insulation in the warm season of the year.

Eleven entomological complexes which are characteristic for the principal biotopes have been distinguished on the basis of a study of the biotopic distribution of insects on the Kuril Islands: the entomofauna of the broadleaved and the broadleaved-dark coniferous forests, the dark coniferous forests, the larch stands, birch stands, alder stands, the Japanese stone pine groves, the floodplain plantations (primarily willow stands), Kuril bamboo groves, herbaceous vegetation, and near-fumarole and supralittoral communities. All these complexes are distinguished by uniqueness of the entomofauna. The entomofauna of coniferous-broadleaved forests, which reveals ancient connections to broadleaved species and which is a legacy of Tertiary fauna, as well as the entomofauna of the near-fumarole communities, which is characteristic for the Kuril Islands and Japan, and the entomofauna of the bamboo stands are of special interest.

Processes of speciation take place in all groups of organisms under the influence of isolation by water and the specific conditions of existence on islands. These are manifested in the Kuril insects in the appearance of morphological and biological adaptive alterations. Change in coloration in the direction of melanism in many of the island insects and the loss of scales and partially of hairs on the elytra by some beetles and simultaneous acquisition of glossy integuments have been observed as morphological adaptations. Other adaptive alterations are associated with the peculiar features of feeding and living on a particular substrate. We classify the phenological features which are characteristic for the Kuril entomofauna and the changes in the behavior of some insects as biological adaptations.

The activity and remoteness in time of the speciation process on the Kuril archipelago can be judged on the basis of the character of the island endemism. Paleoendemics, ancient relict forms (clearly differentiated species) and neoendemics, young forms in the process of formation (more often subspecies and geographic races), have been distinguished among the island endemics.

A group of island endemics in the broad sense, the Sakhalin-Kuril-Japanese species, among which there are the most paleoendemics, a group of endemics of several islands (the Sakhalin-Kuril-Hokkaido), which represents a later phase of the speciation process, and endemics of individual islands, the youngest, which reflects the latest, recent phase of speciation, have been distinguished on the basis of the character of the range. Comparison of information regarding the endemic and vicariant species offers the possibility of concluding that the limited number of endemic forms on individual islands, their insufficient differentiation, and actively progressing processes of recent speciation in various groups of organisms, together with the presence of paleoendemics that are in common with Japan and Sakhalin, testify to a relatively recent occurrence on the Kurils of insular isolation and separation of them from Japan. Based on a number of scientific arguments, it can be hypothesized that the speciation processes proceeded more slowly on the islands of East Asia, after their separation from the continent, than they did on the continent, due to the prolonged preservation on the island territory of climatic conditions that were close to the original conditions.

The entomofauna of the Kuril Islands is zoogeographically heterogeneous. Various zoogeographical elements are present in its makeup which are grouped into two principal complexes in accordance with the types of ranges, the Boreal and the Palaearchaearctic. Species with Holarctic, Transpalaearctic, Amphipalaearctic, Transsiberian, Angaran, Okhotsk, and Beringian types of ranges are included in the Boreal complex. The comprise about 40% of the fauna and are fairly evenly distributed over the territory of the archipelago, but they constitute the overwhelming majority on the central and northern islands. Species with other types of ranges form the Palaearchaearctic complex: Manchurian, Ussuri-Island, Island, Sino-Japanese, and Sino-Ussuri-Japanese. The insects which are included in this complex, despite their numerical predominance, are concentrated on the southern islands. A small number of these reach Urup, and only individuals reach the northern islands. The largest number of archaic species, some of which are relict and endemic, is present in precisely this complex.

The formation of the entomofauna of the Kuril Islands took place under the influence of the southern faunas of East Asia (Japan, the Priamurye, China) and under the influence of boreal and subarctic elements of a moderate and cold climate. This has been reflected in the distribution of the insects over the Kuril Range.

The origin of the entomofauna of different regions of the archipelago is varied. It has an origin more in common with that of Hokkaido and Sakhalin on the Southern Kuril Islands, that is, a Manchurian-Japanese origin. This territory was not (or if it had been, then negligibly) affected by glaciations, and preserved a larger number of southern forms that are residuals of an entomofauna that was formerly generally more thermophilic. The climatological changes of the Quaternary period altered its appearance overall, but not its refugia, evidently mainly in local areas warmed by the thermal influence of volcanic activity, and representatives of southern faunas, partially adapted to the cooler climate of the Quaternary period, survived in coniferous-broadleaved forests. The character of the distribution of some species of insects of various taxa, as well as of plants, for example, the Kuril larch and the entomofauna associated with it, makes it possible to assume the presence of a separative dry-land link which existed at some stage of geological history between Sakhalin, Iturup, and Shikotan.

The glaciations on the Central and Northern Kuril Islands were blanketing, and in combination with powerful transgressions, evidently destroyed all or nearly all the entomofauna. After the disappearance of the glaciers, the northern islands began to be populated from Kamchatka with Boreal, namely widely distributed Okhotsk and Beringian, species, but relatively few of them penetrated the northern islands. Some groups (the orthopteroid insects and others) were entirely unable to overcome the climatic barrier initially, and then the aquatic. They are common on Kamchatka, but they are absent on the northern islands. It cannot be excluded that even now (despite the general warming that commenced in the postglacial period) the climate on the northern islands remains too severe, and that the necessary ecological conditions for the habitation of a number of taxa do not exist there. Therefore, even the insects that have found their way there are far from always capable of surviving and taking hold on those islands. The near-fumarole areas on Paramushir (for example, the fumarole fields on the slopes of the Ébeko Volcano) are entirely devoid not only of entomofauna, but of any vegetation as well, by contrast with similar eco-areas on the southern islands.

The central islands following the melting of the glaciers turned out to be in conditions of the most rigorous marine isolation and of an even more severe climate. Here the entomofauna is represented exclusively by immigrants, both from the north and from the south; therefore, it is extremely impoverished and is accidental in character. Somewhat larger numbers of species were still able to penetrate Urup, while the most central part of Range is extremely impoverished.

The peculiar features of the Kuril entomofauna that we have observed and the regular patterns of its distribution over the archipelago obviously coincide to a substantial degree with analogous patterns in other animals. But it must be emphasized that the insects are in conditions of more rigorous marine isolation than other highly-organized animals, in particular the birds and mammals. They are in that case deprived of the possibility of active transmigration by flight over great distances and of migration along glaciers in the winter season.

Future study of the entomofauna of the Kuril Islands should add to the knowledge of the insects of this most interesting region, their origin, the history of the formation and modern evolution of its fauna. Many questions still remain which touch on the island fauna as a whole; these will be for future investigators to resolve. We hope that the present study will prove to be useful to them in some measure.