About 3,000 species of insects are presently known on the Kuril Archipelago. The insect fauna is unevenly distributed on the territory of the Archipelago. The greatest quantity of species inhabit the southern islands, especially Kunashir. In the Central Islands of the Archipelago the insect fauna is relatively depauperate, only to become more diverse once again in the northernmost islands due to the proximity of Kamchatka. On the large islands the insects are also distributed unevenly: the southern warm-loving species are concentrated in along the west coasts because of the warm currents and other climatic conditions.
The Kuril Island insect fauna is characterized by some peculiarities that make it differ from the continental entomofauna: the marked decrease in the number of genera and species and even the complete absence of some taxa; the limited number of mass species, absence of location of insects mass reproduction for the great areas and simultaneously for several islands; drift of phenological timings of development about the month in comparison with analogous continental regions of the same latitude; prevalence of mesophylous, hygromesophylous, and hygrophylous species; the decreased number of light demanding forms especially heliophylous (sun-lovers); changing of behavior of some night and day insects.
In accordance with biotopical placement of insects there are marked out eleven entomological complexes that are typical for the basic biotopes on the Kuril Islands. All marked complexes differ with peculiarity of insect fauna. The special interest presents insect fauna of coniferous and broad-leaved forests that is the inheritance of tertiary fauna; and also insect fauna of typical insular biotopes around the fumarol's plots, sea coast, and Sasa kurilensis.
The process of speciation is well marked in insular insects. In comparison with other types in this case the geographical (allopatric) speciation is more distinctly marked. The basic nucleus of the insular insect fauna includes the continental species and similar to them forms but in a number of cases it is found out the split of the daughterly ones that are younger. It may be observed in various orders of insects. New appeared variations from the initial form are highly various. For the Kuril insects, it is expressed in the appearance of morphological and biological adaptations variations. The latest species appear under the influence of existence on the conditions of increased moisture of air, reduced and little vacillating temperatures, reduced insolation
Paleoendemics that are ancient relicts (clearly isolated species that have continental vicariations) and insular neoendemics that are the young forms (often subspecies and geographical races) indicate the activity and long process of speciation.
In zoogeographical respects, the Kuril insect fauna is heterogeneous. There are various zoogeographical elements that according to areals are classified in two basic complexes, boreal and palearchearctic (East Asian).
The boreal complex contains the species with holarctic, transpalearctic, amphipalearctic, transsiberian, Angarsk, Okhotsk, and Beringian types of areals. They make up about 40% of the insect fauna, that is evenly distributed through the territory of archipelago but on the central and north islands make up overwhelming majority.
The Palearchearctic complex forms the species with other type of areals of meridional extension. The are Nanchurian, Ussuri-insular, China-Japan, and China-Ussuri-Japan.
The insects of the last complex, in spite of quantitative predominance, are concentrated mainly on the southern islands. The great number of archaic species, part of which are relicts and endemics, are present in this complex.
The formation of insect fauna of the Kuril Islands took place under the influence of the south faunas of Eastern Asia, Japan, Amur region, China, and boreal and subarctic elements of the temperate and cold climate.
The origin of the insect fauna in various parts of the Archipelago is different. On the southern Kurils it has general origin with Hokkaido and south Sakhalin, that is the Manchuro-Japan. On the north islands it is Kamchatkan and on the central islands it is immigration.
The scheme of zoogeographical subdivision is suggested on the grounds of character and origin of entomofauna in various parts of the Kuril ridge.