CHAPTER 6

ZOOGEOGRAPHICAL CHARACTERISTICS OF THE ENTOMOFAUNA OF THE KURIL ISLANDS

SECTION 2. ZOOGEOGRAPHICAL ELEMENTS, ORIGINS, AND TRENDS

The general patterns of the distribution of insects on the archipelago and the zoogeographical character of some orders and families touched upon in the review of the individual groups of insects, the ecological features of the entomofauna and the entomological complexes in preceding chapters. Let us now dwell in greater detail on a zoogeographical analysis of the entomofauna as a whole. The Kuril entomofauna is heterogeneous in origin. It is composed of many zoogeographical elements, characterized by various types of ranges which will make it possible to judge not only the territorial associations of this fauna, but its genesis as well. Groups which are of unequal significance zoogeographically are encountered among the diverse orders and families of insects; this is determined by the scope of the given taxon, its origin, history of development, ecological delimitation, etc. Therefore, a sufficiently complete and reliable notion of the zoogeographical character of the entomofauna as a whole can be framed only through a comparison and general analysis of a number of taxa.

The entire entomofauna of the Kuril Range can be divided with respect to types of ranges into two main complexes - the boreal and the palaearchaearctic, which include a number of smaller groups and subgroups (Table 22).

The boreal complex combines groups of species that are distributed mainly in the forest zone (from the forest tundra in the north to the forest steppe in the south), with ranges extending primarily in the latitudinal direction. The groups differ in the degree of extension of the range from east to west; this frequently points to the origin of the species included in them.

The holarctic group is characterized by the widest - circumboreal or eastern boreal - distribution within the limits of the Palaearctic and Nearctic. It includes mainly forest species, as well as individual representatives of arctic and arctoalpine fauna. Its participation in the Kuril entomofauna is not large and in general evidently does not exceed 10% (see Table 22). Species with a holarctic range are entirely lacking in many systematic groups of insects. Representatives of this group are encountered throughout the archipelago; however, their percentage in relation to other zoogeographical elements on the northern islands is higher than on the southern, due to the small numbers or absence there of representatives of other zoogeographical groups.

The transpalaearctic group consists of species with a wide range encompassing the boreal zone of Eurasia, and as in the case of the preceding group, may contain some subarctic and arctoalpine elements, which are extremely few in number and rare on the Kurils. The species included in this group are distinguished by a wide ecological spectrum. Some of them are associated with coniferous taiga forests, others with leaved species that grow in the northern and southern parts of the forest zone of the Palaearctic; some are polyphages or oligophages of both woody and herbaceous plants. This group is represented in the entomofauna of the archipelago by the maximal number of species in nearly all orders of insects (see Table 22), but their numerical relation to other groups differs on the southern, central, and northern islands. The transpalaearctic species on Kunashir and Shikotan are associated mainly with coniferous species, and occupy a subordinate position in relation to the palaearchaearctic. By Urup this ratio shifts appreciably toward an increase in the percentage of boreal species, while on the central and northern islands they hold a predominant position, but are represented by different ecological complexes. Species of the coniferous forests are nearly absent here, while on the other hand inhabitants of meadows and elfin stands of alder, mountain ash, and willow predominate.

The amphipalaearctic group differs from the preceding group in that the insects included in it have a discontinuous (disjunctive) range, usually linked to the range of their food plants. The majority of such insects are associated with broadleaved species (oak, maple, elm, linden, and some others) that are absent in the modern epoch in Siberia. These are relicts that have been preserved up to the present, apparently from Tertiary or Early Quaternary times, when the plants with which they are biologically linked had a continuous distribution from the Far East to Europe, including Siberia. Such species are considered in greater detail in the examination of the entomological complexes (see Chapter 4, section 3). As a rule, these are monophages or narrow oligophages, adapted to life on a limited range of closely related plants. A larger number of them are encountered among the aphids, cicads, coccids, and some families of lepidopterans and hemipterans, and fewer among other orders. On the Kuril Range they live mainly in broadleaved forests and are concentrated principally on the southern islands. It cannot be excluded that insects associated with some herbaceous plants also occupy an amphipalaearctic range, but their distribution remains insufficiently studied. Since the amphipalaearctic species are mainly geographical relicts, a large increase in their number among the Kuril entomofauna cannot be expected, although it obviously must rise as new chorological data accumulate and the study of individual groups of insects deepens.

The transsiberian group is represented by taiga species whose range encompasses the forest zone of the northern part of Asia, from the Urals to the Kuril Islands. They apparently have an Angaran origin, but as they are quite free-ranging they have been able to penetrate westward to the Urals. The number of such species in the Kuril entomofauna is not large. The following belong to these species: the aphids Paraprociphilusbaicalensis Chol., Aphis galiae Iv., and Sorbaphis chaetosiphon Shap., a long-horned beetle Tetropium gracilicorne Reitt., a crane fly Tanyptera (Protanyptera) gracilis Portsch., a horsefly Chrysops (Heterochrysops) vanderwulpi Kr÷ber, a number of butterflies - Dendrolimus superans Btl., Pyrausta luctualis Hb., Polychrysia aurata Stgr., and Chrysorithrum flavomaculata Brem., and some others.

The Angaran group includes species that are mainly distributed within the limits of Eastern Siberia (in the geological past on the Angaran land mass), from the Enisey River to the shore of the Pacific Ocean. In particular instances these species reach westward across southern Siberia to the Altay and southward to Mongolia and North China. They are confined ecologically mainly to taiga coniferous forests. They hold a secondary though not least position in the entomofauna of the Kuril Islands, and are encountered throughout the entire Range, but singly. As was indicated in Chap. V, some island forms are derivatives of Angaran species.

The Okhotsk group may in essence be regarded as part of the Angaran fauna that formed autochthonously on the northeast rim of the Eurasian continent, apparently on the site of the contemporary Sea of Okhotsk and the territories adjacent to it. At the present time the species that are included in this group are distributed within the limits of the land surrounding the Sea of Okhotsk: on the Okhotsk and Northern Okhotsk littorals of Asia, Kamchatka, Sakhalin, and the Kuril Islands. Some of them reach southward along the mountain ranges to the Sikhot1-Alin'. They do not predominate in the Kuril entomofauna in terms of the number of species, but in population size they occupy an appreciable place in it.

As they are ecologically associated mainly with moist dark coniferous forests and mountain elfin forests, the species of this group are represented by a fairly specific complex, which is defined by a relatively small range of food plants. The following are characteristic for this complex: the leafhopper Oncopsis sardescens An.; the leaf-beetle Gonioctena chujoi L. Medv., which forms several subspecies on the islands and continental part of the Okhotsk littoral; a number of bark-beetle species - Polygraphus sachalinensis Egg., P. proximus Blandf., Cryphaluspiceus Egg., C. kurenzovi Stark., Drycoetes rugicollis Egg., D. ussuriensis Egg., Trypodendron proximum Niiji., and Pityogenes foveolatus Egg.; the horntail Urocerus umbra Sem.; crane flies Tipula (Architipula) pudibonda Sav., T. (Acutipula) acanthophora Al., T. (Pterelachisus) ochotana Sav., T. (Vestiplex) kamchatkana Al., Nephrotoma parvirosta Al., and N. saghalinensis [sic] Al., and some butterflies - Garaeus mirandus Btl., Abraxus carafutonis Mats., Ochropleura militaris Stgr., and Syngrapha transbacailensis Stgr.

Another complex of Okhotsk species is confined to seashores, i.e., occupies a different ecological niche. It includes the following: a ground beetle Amara bipartita Motsch., darkling beetles Phaleromela subhumeralis Mars., Emypsara riederi Fald., bumblebees Bombus tichenkoi Skor. and B. albocinctus Smith, a crane fly Tipula (Lunatipula) gondatti Al., and others. Many species of this complex are encountered only in the northern and central parts of the archipelago, but are unknown on the southern islands.

The Beringian group is close to the Okhotsk in terms of its origin, but reflects somewhat different territorial links. The Beringian fauna arose and developed at the junction of Asia and North America, i.e., at the site of ancient Beringia, as a unitary faunistic complex (Sushkin, 1925; Tugarinov, 1929; Shtegman, 1936; Kuznetsov, 1938; Portenko, 1961; Kurentsov, 1963a). Remnants of this fauna, now often transformed, were preserved until the present on territories surrounding the modern Bering and Chukchi Seas: on the Kamchatka Peninsula, in Chukotsko-Anadyrskiy Kray, in Alaska, on the Aleutian and Komandorskiye Islands (Frey, 1969), and to some extent on the Kuril archipelago. Some Beringian elements, mainly forest species, following the biogeocenoses that are characteristic of them, penetrated adjacent regions of the Asian continent - Eastern Siberia, the Priamurye, and even the Primorye (Sikhot1-Alin'). Others were more widely distributed in North America, reaching Canada, and reaching the more southerly regions of the eastern littoral of the Pacific Ocean along mountain chains.

The number of Beringian species on the Kuril archipelago is not large. The overwhelming majority of them are concentrated on the northern islands (a leafhopper Diplocolenus evansi Aschm., a bug Irbisia sericans StFl, ground beetles Bembidion ventricosum Motsch., Pterostichus pinguidineus Eschch., and Trechus apicalis Motsch., a click beetle Hypnoidus nocturnus Eschch., a crane fly Tipula (Odonatisca) subarctica Al., and others), and only particular representatives of this group (for example, a click beetle Hypnoidus litoralis Eschch., a crane fly Tipulamalaisei Al.), encountered throughout the entire Range, reach its southern region. Ecologically, the Beringian species found on the Kurils are associated with herbaceous eco-areas or seashores. The only representative of the fauna of dark coniferous forests, the horntail Urocerus antennatus Marl., which is evidently of Beringian origin, is encountered on the southern islands. But this horntail is absent in the central and northern regions of the archipelago, and is not found on Kamchatka, although it is known in North America and on territories surrounding the southern part of the Sea of Okhotsk and the northern part of the Japan Sea, from whence it may even have penetrated the Southern Kurils. It must be assumed that the discontinuity of this species' range is explained by the disappearance in the ice age of the dark coniferous forests on Kamchatka and the Northern Kuril Islands.

The palaearchaearctic complex is composed of species of eastern and southeastern genesis. The groups included in it are distinguished mainly by ranges of meridional extent which are contained in general within the limits of the Palaearchaearctic subregion (in the interpretation of A. P. Semenov-Tyan-Shanskiy). This complex contains a large number of relict and archaic species, not infrequently belonging to Indo-Malaysian genera that are richly represented in the tropics of Southeast Asia and are ecologically associated with nemoral broadleaved forests.

The Manchurian group is one of the most numerous on the southern islands of the archipelago (see Table 22). It reflects the broad links that existed in the past between the island and Manchurian (according to A. I. Kurentsov, Priamuryan) faunas. The range of the species of this group encompasses a substantial portion of the Amur basin, North East China, the northern half of the Korean Peninsula, Japan, the Southern Kuril Islands, and Sakhalin. Particular species, going beyond the borders of the general range of the group, reach North East Mongolia and North West China and penetrate the southern regions of Yakutiya and Northern China. The Manchurian elements in the Kuril fauna are represented by nearly all systematic groups of insects; many species form island subspecies or geographic forms. They primarily inhabit broadleaved and dark coniferous-broadleaved forests, but are encountered in other eco-areas as well (see Chapter 4, section 3). They are localized on the southern islands, Kunashir, Shikotan, and Iturup, and only a small proportion reaches northward as far as Urup. The majority of the Manchurian species observed on the Kurils are widely distributed in Japan; however, some of them are unknown there. Fairly detailed lists of the Manchurian species have been cited in the zoogeographical characterizations of particular taxa and in the examination of the faunisitic complexes; it is therefore to no purpose to repeat them here.

The Ussuri-Island group is actually included in the Manchurian group, but is distinguished by a unique range that encompasses the Ussuri basin (mainly its southern portion), to some extent the Korean Peninsula the islands adjacent to the continent (Sakhalin, the Southern Kurils, and Japan); we have therefore set it apart as a separate group, although it may be regarded as a variant of the Manchurian group. It reflects the close links that apparently existed in the recent geological past between these territories and the faunas populating them. In addition to the Japanese-Korean dry-land "bridge", faunisitic exchange evidently also occurred in other areas, since some of the Ussuri-Island species are not found at all in Japan (an aphid Tuberculatus favus Mordv., bark-beetles Ernoporicus spessivtzevi Berg., Eocryphalus semenovi Kurenz., Phellodendrophagus elegans Krivol., Scolytus ventrosus Schev., Dryocoetes orientalis Kurenz., crane flies Tipula bicompressa Al., T. sibiriensis Al., T. fortistyla Al., and a horntail Xiphydria jakovlevi Sem. et Guss.) or are encountered only on Hokkaido (the bark-beetle Dryocoetes striatus Egg.). This can only be explained by presuming the presence of separative links between the continent and the Southern Kurils through Sakhalin, assuming a wider distribution earlier of southern Ussuri species that are relicts today. Insects with the Ussuri-Island type of range are not a rarity; they are observed in a number of orders and families.

The island group includes species that are distributed only on the islands and only singly enter territories closely adjacent to them (the Korean Peninsula and Kamchatka). In essence, all the species included in this group must be regarded as island endemics. Since island endemism was considered in detail in Chapter 5 in the analysis of the processes of species-formation, we will not touch on this problem in such detail. Let us simply recall that the island group consists of several subgroups that differ from one another in the breadth of their intra-island ranges (Figure 64), and is of great interest for an understanding of the interconnections between the faunistic groupings of particular islands. Each of the subgroups corresponds to a specific "age" group of island endemics. The inhabitants of island dark coniferous and mixed broadleaved forests can be distinguished among them; the latter are more diverse.

Species with a Sakhalin-Kuril-Japanese range are distributed in the southern part of Sakhalin, on the Southern Kurils (mainly on Kunashir and Shikotan), and in Japan, primarily on Hokkaido and Honshu. Some of them penetrate much further to the south, reaching Taiwan. The Kuril-Japanese species, lacking on Sakhalin but widely distributed in Japan and entering the Southern Kuril Islands, mainly Kunashir, much more rarely Iturup, only at the range's northern boundary, have nearly the same range.

A large number of island endemics that are known on the archipelago are included in these subgroups. Both subgroups constitute the most ancient core of the island entomofauna, probably preserved in little-changed form since the Neogene and partially since the Paleogene as well, when dry-land "bridges" appeared not only between neighboring islands, but a dry-land link also apparently existed between territories that were at a significant distance from one another. We assign the following paleoendemics to the Paleogene relicts: Syntelia histeroides Lew., long-horned beetles Plectrura metallica Bat., Paraclytus excultus Bat., a bark-beetle Polygraphus nigrielytris Niiji., a wedge-shaped beetle [Rhipiphoridae -Trans.] Metoecus satanas Schild. (Figure 65), a leafroller Eurydoxa advena jezoensis Mats., and some others that have vicariants in North America, Central Asia, and Europe.

The archaic species Syntelia histeroides Lew., one of five species of the only genus of the fam. Synteliidae, is of great interest. It is known in Japan (Honshu, Hokkaido), and we have found it on Kunashir. The distribution of the remaining species of the genus (1 in East India, 1 in China, 2 in Mexico) points to the great antiquity of the family Synteliidae, which is a relict in our era, and which was apparently represented much more richly in the past in the subtropical and tropical countries encircling the northern half of the Pacific Ocean.

The wedge-shaped beetle Metoecus satanas Schild. is also the legacy of a fauna of the distant past. It is known on Sakhalin, in Japan (Honshu, Hokkaido), and in Tibet; we have found it on Shikotan. The largest species of all representatives of the fam. Rhipiphoridae inhabiting the Palaearctic. The remaining species of the genus are distributed in Europe and the Mediterranean; the majority of the species of the family are typical inhabitants of the tropics.

The bark-beetle Polygraphus nigrielytris Niiji., which is distinguished by a discontinuous range within the limits of the Central and the Northern Kuril Islands, is no less interesting. It is common in Japan, on Southern Sakhalin, the Southern Kurils (up to Urup, inclusively), and on Kamchatka; it has not been found on the central and the northern parts of the archipelago, despite careful searches. The vicariant species replacing it lives on related plants in Europe; this attests to the antiquity of this bark-beetle. Japan is undoubtedly the homeland of Polygraphus nigrielytris Niiji., and its presence on Kamchatka may be regarded as merely a relict legacy of a Tertiary fauna that survived there from preglacial times. This is not an isolated example. Some sawflies (Tenthredopsis camtschatcallis Ensl., Eutomostethus tomostethi Mal., Nematinus nigrosternatus Mal., N. kamtchaticus Mal.) that are known on Sakhalin and Kamchatka, crane flies, and other insects have a similar distribution.

However, the majority of general island endemics which do not have vicariants on the continent and are limited in their distribution to the confines of the islands under consideration are relatively young. Some of these are probably of Late Miocene and others of Pliocene-Pleistocene age, but on the whole they belong to a preglacial fauna, since they are associated primarily with thermophilous broadleaved forest. They are represented in all orders of insects and in nearly all large families.

Another, less numerous group of island endemics is localized on a comparatively small territory, limited to the islands of Hokkaido, Sakhalin, and the Southern Kurils. These include the Sakhalin-Kuril-Hokkaido, Kuril-Hokkaido, Sakhalin-Hokkaido, and Sakhalin-Kuril species. The range of each of these subgroups reflects a certain stage of the geological development of this territory, which has undergone substantial and continuous changes throughout the Tertiary and Quaternary periods.

According to the data of Japanese geologists, starting from the Cretaceous, Hokkaido was divided throughout prolonged periods of time into two uneven parts (north-east and south-west) by a marine strait (Figure 66). Its north-east part was periodically connected with Sakhalin and the Southern Kurils, while its south-west part was periodically connected with Honshu or existed in the form of an isolated island. The width and outlines of the strait changed periodically; from time to time it disappeared entirely, and Hokkaido was connected with the other Japanese islands, as occurred in the Eocene, the very beginning of the Miocene, at the end of the Pleistocene, and possibly other segments of geological history. Thus, Hokkaido, together with the territories abutting it to the north, was isolated for a prolonged period from Central and Southern Japan. As it was situated at more northerly latitudes, it was distinguished by a less warm climate than the rest of the Japanese islands, and a more boreal appearance of the vegetation, which even now has many traits in common with that of Southern Sakhalin and the Southern Kurils.

Its own fauna formed here in keeping with the natural conditions, among which a fairly large number of endemic forms became differentiated. Some of them were possibly localized in restricted areas, partitioned from neighboring areas by mountain chains or other barriers, like the mosaic distribution of insects which is observed at the present time on Kunashir and other southern islands of the Kuril Range (see Chapter 4, section 2). This evidently explains the absence of many Kuril-Hokkaido species on Sakhalin, and of Sakhalin-Hokkaido species on the Kuril Islands.

The range of the Sakhalin-Kuril species points to the existence of separative connections between Sakhalin and the southern part of the Kuril archipelago; this has been repeatedly referred to above. True, there is no absolute guarantee that these species will not be found as well on Hokkaido, whose entomofauna has not yet been sufficiently carefully studied. But thus far there are grounds for assuming that such a connection did exist.

The age of the endemics of this group is obviously varied, since the conditions of marine isolation appeared in various regions of Hokkaido and the islands adjacent to it throughout the entire history of the geological development of the region. Nevertheless, not many ancient forms were apparently preserved there; this is indicated by the comparatively low percentage of endemics of this group. This is explained by the substantial cooling of the climate in the ice age, when the most thermophilous insects and other animals were killed by cold there simultaneously with the disappearance of many southern plants. The entomofauna of the dark coniferous and broadleaved-dark coniferous forests, which became predominant, appeared to take their place. Later endemics, mainly Pleistocene, in fact appeared in its composition. Among the latter are the majority of the Sakhalin-Kuril-Hokkaido and Kuril-Hokkaido species and especially subspecies. The ground beetles Carabus (Damaster) rugipennis Motsch. and Cyrchus morawitzi Geh. and some other species from various taxa are ancient forms of this group.

The active differentiation of the Kuril proper species began mainly after the final separation of the Kuril Islands from Hokkaido at the end of the Pleistocene-beginning of the Holocene. It cannot be excluded that some species living on the archipelago acquired independence significantly earlier, since the connection with Hokkaido was interrupted repeatedly and since conditions of marine isolation existed on these islands in the past. As the study of the individual taxa of insects by specialists has deepened, an ever larger number of endemics of the Kuril Islands have been identified. The high percentage of endemics of the subspecies categories and the low percentage of those of the species categories serve as an indicator young endemism (see Chapter 5). The ancient forms found on the Kurils are extremely rare and few in number. The following may be classed among these: of the beetles, a representative of the tropical family Languriidae - Languriomorpha kunashiriana K!no. (possibly a derivative of the close Kuril-Japanese species living here, Languriomorpha lewisii Crotch.); a burying beetle Phosphuga shakotana K!no, described on Shikotan and later found only on Paramushir; some rare click beetles, Hypnoidus kurilensis Gur., Ampedus doii Miwa (Kunashir), A. etorupensis Miwa (Iturup), and A. shakotanensis Miwa (Shikotan); of the neuropterans, Lysmus kurilensis Kuwayama (Iturup) and Hemerobius shikotanus Kuwayama (Shikotan), described by S. Kuwayama on the basis of single specimens; as well as some other insects. Young evolving species, on the contrary, are distinguished by relatively frequent incidence and relatively high numbers.

Local endemic forms are encountered in all parts of the archipelago, but their number varies on the different islands. The largest number of Kuril endemics are observed on Kunashir and fewer on the other islands. The endemic species are more often distributed on one island and less often on two or several islands. By way of example, we present lists of endemics of various taxonomic levels that are known from particular large islands.

These lists do not exhaust the entire composition of forms that are endemic for the Kurils, but offer a notion of their proportion on various islands and point to the territorial connections that existed between particular islands in the past. Thus, it can be concluded on the basis of the character of the ranges of the endemic species, that the entomofauna of Kunashir had bilateral contact with the faunas of Iturup and Shikotan, and that the connection with Iturup was apparently more prolonged, since the greatest number of common forms is encountered on these islands in particular. At some stage Iturup in its turn was connected to Urup (possibly briefly). At the same time, there was a separative connection between Shikotan and Iturup, since some endemic species of insects exist that are common to these islands, but are absent on Kunashir. In addition, the Kuril Dahurian larch grows only on these two islands, of the entire Kuril Range. The above hypothesis seems entire probable to us, because the depth of the Yuzhno-Kuril'skiy Strait is only 15-20 m and of the Ekaterina Strait does not exceed 260 m, as well as by virtue of the fact that volcanic activity went on very intensively on the Greater Kuril Range throughout nearly the entire Neogene and the Quaternary and that the active Barutarube Volcano is located at the very southern tip of Iturup. Our point of view on this matter does not coincide with the opinion of other investigators, for example, A. G. Velizhanin (1970).

The Sino-Japanese group is represented in the Kuril entomofauna by a fairly small number of rare species, such as a cricket Scapsides micado Sauss., the bug Acanthosoma expansum Horv., the stag beetle Eurytrachelus rectus Motsch., the lycid Mesolycus atrorufus Kiesenw., long-horned beetles Eryssamena tuberculata Pic, Glenea relicta Pascoe, Dihammus fraudator Bat., and Asaperda meridiana Matsush., and butterflies Lethe diana Btl., Neope gashkewitschi M1n., Spilarctia casignata seriatopunctata Mast., Moma champa ainus Wil., Lophopteryx saturata Wkr., Pergesa elpenor lewisi Btl., Mimeusemia persimilis Btl., and others. Only some of them (Lethe diana Btl., Neope gashkewitschi M1n., Mimeusemia persimilis Btl.) are found to be common. They are encountered mainly in the broadleaved forests of Kunashir (principally in its southwestern region), and extremely rarely on Shikotan and Iturup; on the other hand, they are widely distributed in Japan all the way to the south.

This group attests not only to the initial commonality of the Sino-Japanese entomofauna, but to its periodic interchange as well, which has taken place even more recently, evidently right to the end of the Pleistocene, across the dry-land "bridge" at the site of the Tsushima Strait. Otherwise it is hard to explain the cause of the penetration into China of some species of Japanese origin. The discovery of clearly Japanese species (the lamellicorns Heptophylla picea Motsch., Anomala rufocoprea Motsch., Gnorimus viridiopacus Lew., and Cetonia roelofsi Har.; the clickbeetles Selatosomus notabilis Cand. and Silesis musculus Cand.; the bark-beetle Scolytoplatypus daimio Blandf., and others) on the Korean Peninsula may serve as a confirmation of such a migratory route of the island entomofauna to the continent. For some reasons they were unable to penetrate beyond the boundaries of the peninsula and stopped, as it were, halfway.

Since the connection of Japan with the continent was broken repeatedly, the age of immigrants moving in both directions (from the continent to the islands and back) may vary. Insects belonging to the same genera but represented on the islands and the continent by different species are more ancient. Species that have formed different subspecies or geographical forms on these adjacent territories must be assumed to be younger than they. Finally, species having a Sino-Japanese range at the present time must be regarded as the youngest, apparently, Late Pleistocene or Early Holocene. On the Kuril Islands, species having such a range must be regarded as relatively late immigrants that crossed over there from Japan via Hokkaido in the Pleistocene, and possibly in the postglacial period. The widely distributed East Asian species, which constitute a negligible part of the Kuril entomofauna, also found their way into the Kurils in a similar manner. The cosmopolites as well as the casual and ecdemic species, which are disregarded in the zoogeographical assessment of the fauna, are undoubted immigrants on the archipelago.

It can be seen from this analysis of the zoogeographical groups that the Kuril entomofauna formed mainly under the influence of two ecologically different faunas - the boreal and the palaearchaearctic. The process of formation of this entomofauna, which is heterogeneous at the present time in different parts of the Kuril archipelago, seems to us to be as follows.

At the end of the Cretaceous-beginning of the Tertiary periods, when the dry land stretched to the shores of the Pacific Ocean and the climate was evenly warm and moist at various latitudes all the way to Kamchatka, the fauna living there apparently constituted a unitary whole. It was represented by thermophilous forms inhabiting mixed forests which consisted of diverse coniferous and broadleaved species of a Tertiary flora. After the formation of the Western Kamchatka trough (presumptively in the Eocene), the continental littoral was transformed into a chain of islands. The part of the entomofauna that was left on the island territory found itself in more favorable little-changing climatic conditions, as a result of which it was long preserved in its primordial form. The absence on the Kuril archipelago and along the littoral of Japan of clearly-marked vertical zonality points to the fact that up to the present time the island fauna maintained the features of an ecologically weakly-differentiated Tertiary fauna. Then, under the influence of constant volcanism, accompanied by powerful discharges of lava, periodic transgressions, and cooling beginning in the Oligocene, the composition of the entomofauna became gradually impoverished. On the small islands it could be entirely annihilated, but then again be restored in the northern portion of the archipelago due to an influx of insects from Kamchatka, and in the southern portion from territory of the Lesser Kuril Range and Hokkaido that had not subsided and that made up, along with Kunashir and possibly with Iturup as well, a single land mass. Thus, a stable entomofauna composition that contained many southern forms was permanently supported on the Southern Kurils.

The central islands, with the exception of Urup, did not exist during the Paleogene and possibly the Neogene, or they appeared only periodically. In their place there was a strait connecting the Sea of Okhotsk with the Pacific Ocean. Therefore the known discontinuity between the entomofauna of the southern and northern islands had already arisen at that time.

To the degree the cooling intensified and the composition of the vegetation altered in the direction of the predominance of dark coniferous and small-leaved species, the appearance of the entomofauna also gradually changed; it lost the most thermophilous forms and increasingly acquired a boreal appearance. The entomofauna of the southern islands was systematically supplemented by taiga and Manchurian species which had gotten there from the continent via Sakhalin and Hokkaido, and by Japanese, Chinese, and East Asian inhabitants of the more southerly broadleaved forests from Central and Southern Japan. Having reached the islands, the continental species, which had already altered under the influence of the process of xerophilization [??sic - xerophytization/xerotization?] that was taking place at that time on the continent, were partially transformed into island forms under the influence of moister climatic conditions. Consequently, the synthesis of entomofauna of the most varied zoogeographical elements, along with the preservation of its more ancient, indigenous, component, took place on Hokkaido and the Southern Kurils. The entomofauna of the Northern Kuril Islands as well took place analogously, but form different zoogeographical components. In the main Beringian, northern Okhotsk, and northern boreal species predominated there, and at the same time a certain number of southern forms were preserved.

The majority of the vegetation (in the first place, forest) was annihilated in the first phase of the ice age by blanketing glaciers on the northern and central islands, and the insects associated with it died out. The extreme impoverishment of the entomofauna in these parts of the archipelago in fact arose as a result. Evidently the dark coniferous forests disappeared precisely at that time from Urup and the southern islands closest to it, which later became part of Iturup, while some of the insects associated with those forests adapted to life on the Japanese stone pine, as was referred to above.

In the southern half of Iturup and on Kunashir, where the glaciation was semi-blanketing, as well as on the Lesser Kuril Range where it may have not existed at all, the insects found themselves in better conditions. Despite the general worsening of the climate, dark coniferous forests and in particular areas, apparently, broadleaved-dark coniferous forests were preserved there; a distinctive microclimate was created under their canopy, as it has been now. Moreover, thermophilous insects and other animals were able to find shelter and to group around hot springs, fumaroles, and other volcanic thermal springs which undoubtedly existed on the Kurils in the ice age as well; we observe this up to the present time on the Kuril Range (see Chapter 4, section 3) and on Kamchatka (Markov, 1962). Many thermophilous forms were able to persist and survive the glacial epoch in such refugia against the general background of degradation of the entomofauna.

Some of the insects associated with broadleaved species adapted to the new ecological conditions, switching to feeding on small-leaved species - alder, birch, willow, and others instead, apparently, of the broadleaved species (ash, oak, cork tree, etc.) that disappeared at that time from the Kuril forests. These secondary associations proved to be so durable that they have persisted until the present, although the broadleaved trees enumerated are growing again on the Southern Kuril Islands. This characteristic of a number of species serves as an indirect proof of the persistence on the Southern Kurils of the indigenous, preglacial entomofauna. At the same time, a substantial proportion of the thermophilous insects died out there, unable to tolerate the change in the ecological situation, and were unable to recover; the marked impoverishment of the entomological complexes associated with each of the broadleaved species attests to this (see Chapter 4, section 3).

With the onset of interglacials, when the climate would become warmer, the dissemination of the insects and other animals over the Kuril Range, both in the northerly and southerly directions, would commence. However, it could not be a mass dissemination, since the periods of temperature rises coincided with marine transgressions and with the destruction of the land connections in the south with Hokkaido and in the north with Kamchatka.

The wind is the most powerful factor promoting the transport of insects from island to island. At the present time the paths of cyclones in the warm season of the year pass in the southerly, southwesterly, and westerly directions, while the anticyclones pass in the northwesterly, and north-northeasterly directions (Zhuneva, et al., 1967). During interglacial temperature rises, in keeping with the regular pattern inferred by G. G. Lemb (1968), the paths of cyclones must have coincided or approximated contemporary paths. Thus in the past, as is the case now, the transport of insects by wind along the Kuril Range was possible. But not all insects are transported by wind with equal success. Groups with well-developed free wings and hovering flight - dragonflies, flies, butterflies, hymenopterans, aphids, and some others, in this case have superior vagility; wingless forms, bugs, and beetles have inferior vagility. And in fact, when the entomofauna of the central and northern islands were analyzed, it was found that the beetles and bugs were very few in number in these parts of the archipelago by comparison with other groups, for example, flies, sawflies, and butterflies, while the orthopteroid insects are entirely lacking, although they are present on the Southern Kurils and Kamchatka. It must also be borne in mind that individuals brought to an island can only survive if they find conditions of existence that are suitable for them, and food above all. Therefore, many forest species, having ended up on unforested islands, inevitably die due to the lack of their food plants. The inhabitants of meadows - flies, sawflies, particular species of butterflies, and some species of aphids, on Urup the bamboo aphid in particular, are background species on the central and northern islands.

As we know, the connection of the southern part of the Kuril Range with the continent was re-established several times during the Pleistocene via the Sakhalin-Hokkaido dry-land "bridge". But since regressions of the sea were coupled with periods of cooling and the intensification of glaciations, a mainly boreal fauna, associated with dark coniferous forests and herbaceous vegetation, was able to penetrate the islands during this time segment. The climatic barrier, on the other hand, apparently impeded the influx of southern forms. The boreal species, having better adaptability to severe climatic conditions, had greater possibilities for disseminating along the archipelago toward the north. This was especially true for the hortobionts, inhabitants of herbaceous eco-areas. Consequently, the Kuril entomofauna took on a more boreal appearance throughout the second half of the Pleistocene.

The path of penetration of the larch into the archipelago, which forms forest stands only on Iturup, remains not entirely clear thus far. According to the data of N. V. Dylis (1961), the range of the Kuril Dahurian larch, which is represented by two subspecies, encompasses the littoral territory of the Sea of Okhotsk: Central Kamchatka, the Okhotsk continental littoral (roughly to the mouth of the Amur), Sakhalin, Iturup, and Shikotan. The subspecies Larix kurilensis ssp. kurilensis is encountered only on Sakhalin and the Kurils, but is absent elsewhere, including Hokkaido. Hence the inference suggests itself: the only path along which the larch could have penetrated Iturup along with the entomofauna peculiar to it is a dry-land "bridge" directly between Sakhalin and Iturup, but at the same time, a connection between Kunashir and Hokkaido was lacking.

Summarizing the above, it can be concluded that the origin of the entomofauna of the Kuril Islands is not identical in various parts of the Range. It is purely migrational in character on the northern and central islands, and had formed as far back as the postglacial period. On the northern islands (Paramushir and Shumshu) the influence of the Kamchatka, northern Okhotsk, and Beringian faunas was greater, due to the proximity of the Kamchatka Peninsula and the Aleutian Islands. Representatives of Manchurian and other southern faunas are nearly entirely absent there; the number of the forest insects is limited to species living on the Japanese stone pine, alder, willow, and mountain ash; arctoalpine elements are not uncommon.

On the central islands, which lie between the Fourth Kuril and Boussole Straits, the entomofauna comprises a markedly impoverished variant of the northern Kuril fauna. On these islands, with the possible exception of Simushir, representatives even of the Manchurian fauna are entirely absent. Urup occupies a transitional position, zoogeographically, between the central and southern islands. Residuals of the indigenous entomofauna of the dark coniferous forests (some "spruce" and "fir" species of bark-beetles and long-horned beetles that today live on Japanese stone pine) have persisted on it, and at the same time, a fairly small number Manchurian and other forms among various groups of insects are present along with northern forms.

The entomofauna of the Southern Kuril Islands is of mixed origin. It includes both groups of indigenous species, associated not only with dark coniferous forests, but with broadleaved forests as well, and immigrants which have arrived there by various routes and from various territories. A large number of Manchurian, Japanese, Japanese-Chinese, and other southern species are encountered on the southern islands, as well as the greatest number of endemic forms of Sakhalin-Kuril-Hokkaido and Kuril proper genesis; this points to active species-formation processes in this region, occurring in the past and continuing up to the present. A. I. Kurentsov (1968a) regards this region as a special "Hokkaido-Kuril" center of endemism of the Far East.

The formation of the Kuril entomofauna continues in the present epoch, and is proceeding in the direction of ever greater differentiation of island forms under the influence of aquatic isolation. The main factors determining the character of the entomofauna are geological processes that are expressed in active volcanic activity, aquatic isolation, marine climate, diverse vegetation which is being appreciably altered under the influence of man, natural migrations (mainly by means of the wind), and active importation of some species by people (synanthropic insects, pests of agricultural plants and produce stores).

Active volcanism is a specific feature of the Kuril Islands. Along with the positive role of various thermal springs, which serve as refuges for many thermophilous species, the diverse manifestation of volcanic activity has a negative impact on the entomofauna of the islands as a whole. Thus, the eruption of volcanoes is often accompanied by the abundant emission of toxic gases and ashes that are carried far by the wind, kill many animals, including insects, and act lethally on plants (Snow, 1902; Kurenkov, 1957; Vorob'ev, 1963). As a result of the ashfall that we observed on Kunashir in 1962, during the eruption of Takachi-dake Volcano on Hokkaido, the majority of insects perished, first of all butterflies, hymenopterans, flies, etc., especially in the imaginal phase (Krivolutskaya, Nechaev, 1963). Their numbers were slowly restored, due to diapaused and pupal phases situated in shelters where the ash did not penetrate.

The discharge of lava, especially on small volcano islands, often destroys all vegetation and animals and causes fires. Organic life is again restored on such islands following an eruption. Tsunamis with terrific destructive force break up over the islands and devastate the entire littoral zone, at times over a substantial distance. The process of build-up of the flora and fauna at sites of their catastrophic destruction or on newly emerging islands under the conditions of the Kuril Range remains unstudied, although it is of great interest.