Variation in mitochondrial COII gene sequences among two species of Japanese knotweed-boring moths, Ostrinia latipennis and O. ovalipennis (Lepidoptera: Crambidae)

The Ostrinia latipennis group contains two species, O. latipennis (Warren) and O. ovalipennis Ohno. These two species commonly utilize perennial knotweeds (Fallopia spp.) as their host plants, which are serious invasive weeds in Europe and North America. Ostrinia latipennis is widely distributed across north-east Asia including Japan whereas O. ovalipennis is restricted to north Japan (Hokkaido Is.) and highland areas of central Japan (Nagano Prefecture in Honshu Is.). To estimate the phylogenetic relatedness and geographical differentiation of the two species, mitochondrial COII gene sequences were determined for specimens covering their distribution ranges in Japan. The uncorrected sequence divergence between O. latipennis and O. ovalipennis was 0.6-0.7%, supporting a close relationship. According to the standard molecular clock proposed for arthropod mtDNA, the two species are speculated to have diverged about 0.3 Myr ago. A single COII gene haplotype was found in O. latipennis irrespective of collection locality. In contrast, two haplotypes were found in O. ovalipennis, and their frequencies were significantly different between the Hokkaido and Honshu populations. The patterns of geographical variation in the COII gene within the two species were in agreement with previously reported patterns of geographical differentiation in morphology of the two species in Japan. The present results support the hypothesis that gene flow among local populations of O. ovalipennis has been limited by geographical isolation.     

Mitochondrial DNA phylogeography of the red fox (Vulpes vulpes) in northern Japan

Mitochondrial DNA variation in the cytochrome b (cyt b) gene and the control region was examined in the red fox Vulpes vulpes from Japan, with special focus on the population divergence between Hokkaido and northern Honshu. Resultant haplotypes from Hokkaido were subdivided into two distinct groups (I and II), with an average genetic distance of 0.027 for cyt b. Divergence time is roughly estimated to be 1-2 million years ago, given that the conventional divergence rate of the mammalian cyt b gene is 2% per million years. Notably, Group II was only found in Hokkaido, whereas Group I comprised haplotypes from Honshu, Kyushu (Japan), eastern Russia, and Europe, as indicated by a comparison of our own data to the literature. On the other hand, judging from constructed trees, Group I haplotypes from Hokkaido appeared to differ from those from other parts of Japan, i.e., Honshu and Kyushu. This implies that Blakiston's Line, which demarcates the boundary between Hokkaido and Honshu, has been an effective barrier and has allowed the structuring of genetic variation in maternal lineages. Thus, these results suggest that the Hokkaido population, which is sometimes referred to as the distinct subspecies V. v. schrencki, has its own genetic background with multiple migration events and differs from the parapatric subspecies V. v. japonica found in Honshu and Kyushu.     

The genus Campylocheta (Diptera: Tachinidae) from Japan

Seven new species of Campylocheta are described and illustrated from Japan: abdominalis from Hokkaido, Honshu and Kyushu, flaviceps from Honshu and Tsushima, grisea from Kyushu, argenticeps from Honshu, bisetosa from Hokkaido and Honshu, hirticeps from Hokkaido, Honshu and Tsushima, and suwai from Hokkaido. Campylocheta dentifera Richter and C. umbrinervis Mesnil are redescribed and a key to nine Japanese species is provided.     

Genetic structure,admixture and invasion success in a Holarctic defoliator,the gypsy moth (Lymantria dispar,Lepidoptera: Erebidae)

Characterizing the current population structure of potentially invasive species provides a critical context for identifying source populations and for understanding why invasions are successful. Non‐native populations inevitably lose genetic diversity during initial colonization events, but subsequent admixture among independently introduced lineages may increase both genetic variation and adaptive potential. Here we characterize the population structure of the gypsy moth (Lymantria dispar Linnaeus), one of the world's most destructive forest pests. Native to Eurasia and recently introduced to North America, the current distribution of gypsy moth includes forests throughout the temperate region of the northern hemisphere. Analyses of microsatellite loci and mitochondrial DNA sequences for 1738 individuals identified four genetic clusters within L. dispar. Three of these clusters correspond to the three named subspecies; North American populations represent a distinct fourth cluster, presumably a consequence of the population bottleneck and allele frequency change that accompanied introduction. We find no evidence that admixture has been an important catalyst of the successful invasion and range expansion in North America. However, we do find evidence of ongoing hybridization between subspecies and increased genetic variation in gypsy moth populations from Eastern Asia, populations that now pose a threat of further human‐mediated introductions. Finally, we show that current patterns of variation can be explained in terms of climate and habitat changes during the Pleistocene, a time when temperate forests expanded and contracted. Deeply diverged matrilines in Europe imply that gypsy moths have been there for a long time and are not recent arrivals from Asia.     

Two mitochondrial lineages occur in the Asian corn borer, Ostrinia furnacalis (Lepidoptera: Crambidae), in Japan

The genealogy and diversity of the mitochondrial cytochrome oxidase subunit II (COII) gene were investigated for Ostrinia furnacalis in Japan. A preliminary examination of mitochondrial lineages in China and the Philippines was also made. Two lineages (A and B) were found in the COII gene. Lineage A was frequent throughout the Japanese main islands (Hokkaido, Honshu, Shikoku and Kyushu), while the frequency of lineage B varied among these islands. No clear patterns of geographical population structure were found. Population genetic features suggested that the O. furnacalis population harboring the lineage A mitochondria expanded in the recent past, while lineage B showed weak signals of a population expansion. It is not clear whether the two lineages of mtDNA evolved in separate or identical geographical regions. We discuss two hypotheses regarding the two lineages of mtDNA: a cryptic race/species hypothesis and a selective sweep hypothesis.     

Bottleneck effects on the sika deer Cervus nippon population in Hokkaido, revealed by ancient DNA analysis

The population size of the sika deer Cervus nippon on Hokkaido Island of Japan had been remarkably reduced because of heavy hunting pressure since the beginning of Meiji Period and effects of heavy snow in 1879 and 1881. After that, the number of sika deer in Hokkaido has increased gradually due to the protection by the Hokkaido government. In the present study, in order to investigate the bottleneck effects, we analyzed ancient mitochondrial DNA (mtDNA) on sika deer bones excavated from archaeological sites just before Meiji Period. On 86 of 113 bones from 13 archaeological sites of Ainu Culture Period (17-19th centuries), 602 base-pair fragments of the mtDNA control region were successfully sequenced. Consequently, we found three new haplotypes (g-, h- and i-types) which had not been identified in modern sika deer. In addition, four haplotypes (a-, b-, c- and d-types) identified from modern sika deer were also found in the archaeological deer. The new haplotypes and previously reported hapoltypes from sika deer of Hokkaido were phylogenetically much closer to each other, compared with those of modern sika deer from Honshu, Kyushu and the Chinese continent. Geographical distribution patterns of haplotypes of the ancient population were different from those of the modern population in Hokkaido. Our findings indicated that their genetic diversity was reduced through the bottleneck and that population structures of sika deer were changed widely in Hokkaido due to genetic drift.     

Resurrection of Rabdophaga salicivora Shinji (Diptera: Cecidomyiidae), a Japanese gall midge formerly misidentified as a North American species, Rabdophaga rigidae (Osten Sacken), with observations on the phylogenetic relationships of its populations in Japan and the Russian Far East

Intercontinental biotic connections between Eurasia and North America are common in many gall midge genera (Diptera: Cecidomyiidae), but only a few species have been recorded from both continents. In Japan, four gall midge species had been previously considered to be identical to North American species, but three of these cases have already been disproved. We examined the remaining species, Rabdophaga rigidae, which had been originally described from Japan as Rabdophaga salicivora in 1938, later recorded from the Russian Far East in 1967, and synonymized with a North American species, R. rigidae, in 1982. Morphological features and partial sequence data of the mtDNA cytochrome oxidase subunit I (COI) region suggested that the Japanese species is a distinct species and is identical to the species recorded from the Russian Far East. We therefore apply the original name, R. salicivora, to the Japanese and the Russian species. In addition, on the basis of a molecular phylogenetic analysis, we conclude that R. salicivora possibly came to the Japanese Archipelago through the Korean Peninsula and established itself first in the southern parts of Japan. Then, it expanded its distribution range to northern parts of Honshu, but could not reach Hokkaido, probably because of the Tsugaru Strait between Honshu and Hokkaido.     

rbcL sequences reveal multiple cryptic introductions of the Japanese red alga Polysiphonia harveyi

In Europe, the last 20 years have seen a spectacular increase in accidental introductions of marine species, but it has recently been suggested that both the actual number of invaders and their impacts have been seriously underestimated because of the prevalence of sibling species in marine habitats. The red alga Polysiphonia harveyi is regarded as an alien in the British Isles and Atlantic Europe, having appeared in various locations there during the past 170 years. Similar or conspecific populations are known from Atlantic North America and Japan. To choose between three competing hypotheses concerning the origin of P. harveyi in Europe, we employed rbcL sequence analysis in conjunction with karyological and interbreeding data for samples and isolates of P. harveyi and various congeners from the Pacific and North Atlantic Oceans. All cultured isolates of P. harveyi were completely interfertile, and there was no evidence of polyploidy or aneuploidy. Thus, this biological species is both morphologically and genetically variable: intraspecific rbcL divergences of up to 2.1% are high even for red algae. Seven rbcL haplotypes were identified. The four most divergent haplotypes were observed in Japanese samples from Hokkaido and south-central Honshu, which are linked by hypothetical 'missing' haplotypes that may be located in northern Honshu. These data are consistent with Japan being the centre of diversity and origin for P. harveyi. Two non-Japanese lineages were linked to Hokkaido and Honshu, respectively. A single haplotype was found in all North Atlantic and Mediterranean accessions, except for North Carolina, where the haplotype found was the same as that invading in New Zealand and California. The introduction of P. harveyi into New Zealand has gone unnoticed because P. strictissima is a morphologically indistinguishable native sibling species. The sequence divergence between them is 4-5%, greater than between some morphologically distinct red algal species. Two different types of cryptic invasions of P. harveyi have therefore occurred. In addition to its introduction as a cryptic sibling species in New Zealand, P. harveyi has been introduced at least twice into the North Atlantic from presumed different source populations. These two introductions are genetically and probably also physiologically divergent but completely interfertile.     

Patterns of distribution in Japanese land mammals

Distribution patterns among the terrestrial mammal species of Sakhalin and the main islands of Japan are shown to fall into 12 clear groups. The most fundamental distributional break (Blakiston's Line) is that separating Hokkaido and Sakhalin to the north, with their boreal fauna typical of northern Eurasia, from ‘Hondo’ (Honshu, Shikoku, Kyushu) to the south, which demonstrates a high degree of endemism and supports a small number of Indo-Malayan elements. Distribution patterns may be explained by considering the Quaternary geohistory of the area, particularly the formation of land bridges and the changes in climatic conditions during this period. A dynamic classification based upon origin of the fauna recognizes seven categories, although on evidence currently available the allocation of some species to categories is not yet possible. Hondo underwent two main periods of land bridge connection to the Asiatic mainland. The first, prior to the Pleistocene, allowed immigration of forms which have since developed into distinctive elements of the endemic fauna (‘Old Hondo Endemics’). The second, during the Middle Pleistocene, brought in widespread Palaearctic species as well as components from South-East Asia (‘Early Colonists’), some of which have since undergone vicariant speciation (‘New Hondo Endemics’); it also allowed several of the Old Hondo Endemics to extend their range to the mainland and Hokkaido (‘Expanding Hondo Endemics’). Sakhalin and Hokkaido have been more intimately connected to the mainland (most recently until less than 10 000 years ago), such that endemism is very restricted. Species groups here are the ‘Late Colonists’, cold-adapted tundra species which expanded with the glacial advances, but which are now restricted in distribution, and ‘Recent Colonists’, postglacial forest species which recolonized before the severance of land bridges. Moving the other way were ‘Expanding Northern Endemics’, which arose in Hokkaido or Sakhalin during the last glacial and colonized the adjacent mainland before severance of land links. There are, additionally, several possible Expanding Hondo Endemics in Hokkaido, although human intervention in determining their current distributions cannot be ruled out. Bats, to which the sea barriers of the Japanese area are less complete, exhibit somewhat different patterns of distribution, confirming predictions about the role of even narrow marine straits in restricting ranges of nonflying mammals.     

Two Genetically Distinct Lineages of the Sika Deer, Cervus nippon, in Japanese Islands: Comparison of Mitochondrial D-Loop Region Sequences

To investigate genetic diversity among populations of the sika deer, Cervus nippon, nucleotide sequences (705–824 bases) of the mitochondrial D-loop regions were determined in animals from 13 localities in the Japanese islands. Phylogenetic trees constructed by the sequences indicated that the Japanese sika deer is separated into two distinct lineages: the northern Japan group (the Hokkaido island and most of the Honshu mainland) and the southern Japan group (a part of the southern Honshu mainland, the Kyushu island, and small islands around the Kyushu island). All sika deer examined in this study shared four to seven units of repetitive sequences (37 to 40 bases each) within the D-loop sequences. The number of tandem repeats was different among the populations, and it was specific to each population. Six or seven repeats occurred in populations of the northern Japan group, while four or five repeats occurred in populations of the southern Japan group. Each repeat unit included several nucleotide substitutions, compared with others, and 26 types were identified from 31 animals. Sequences of the first, second, and third units in arrays were clearly different between the northern and the southern groups. Based on these D-loop data, colonization and separation of the sika deer populations in the Japanese islands were estimated to have occurred less than 0.5 million years before present. Our results provide an invaluable insight into better understanding the evolutionary history, phylogeny, taxonomy, and population genetics of the sika deer.     

Asian origin and rapid global spread of the destructive dry rot fungus Serpula lacrymans

The dry rot fungus Serpula lacrymans (Basidiomycota) is the most damaging destroyer of wood construction materials in temperate regions. While being a widespread aggressive indoor biodeterioration agent, it is only found in a few natural environments. The geographical source of spread and colonization by this fungus in human environments is thus somewhat of an enigma. Employing genetic markers (amplified fragment length polymorphisms, DNA sequences and microsatellites) on a worldwide sample of specimens, we show that the dry rot fungus is divided into two main lineages; one nonaggressive residing naturally in North America and Asia (var. shastensis), and another aggressive lineage including specimens from all continents, both from natural environments and buildings (var. lacrymans). Our genetic analyses indicate that the two lineages represent well-differentiated cryptic species. Genetic analyses pinpoint mainland Asia as the origin of the aggressive form var. lacrymans. A few aggressive genotypes have migrated worldwide from Asia to Europe, North and South America and Oceania followed by local population expansions. The very low genetic variation in the founder populations indicate that they have established through recent founder events, for example by infected wood materials transported over land or sea. A separate colonization has happened from mainland Asia to Japan. Our data also indicate that independent immigration events have happened to Oceania from different continents followed by admixture.     

Comments on cephalometrical configurations of the Japanese

Cephalometrical configurations of Japanese people were investigated on two hundred and sixteen groups living on the four main islands of Japan: Hokkaido, Honshu, Shikoku, and Kyushu. The Japanese in Honshu were divided geographically into a narrow-featured eastern major group and a broad-featured western major group. A physical characteristic of Japanese living in the western mid-Honshu was the lengthened feature of their cephalic measurement, an influence of a long-headed group of Korean people; Japanese residents in eastern mid-Honshu, however, showed the result of mixing with a short-headed group of Korean people. Japanese people living in Hokkaido, the northernmost island, and in the Ryukyu Islands in the South of Japan, presented no important finding which suggests their influence on the physical characteristics of the Japanese. Ongoing studies indicating physical relationships between Kyushu or Shikoku residents and Honshu residents, are as yet insufficient.     

Intraspecific variation of cuticular hydrocarbon composition in Formica japonica Motschoulsky (Hymenoptera: Formicidae)

Cuticular hydrocarbons and morphological features were compared among 80 Formica japonica colonies collected in Japan. Although a few morphological differences were found in workers among the colonies, four different types of cuticular hydrocarbon composition were observed. This was supported by a principal component analysis. We further compared the cuticular hydrocarbons among a total of approximately 400 F. japonica colonies, and categorized the hydrocarbon components into four types based on the result of discriminant analyses for the first 80 colonies. Type 1 was observed in colonies mainly collected in southern Honshu, Shikoku, and Kyushu. Types 2, 3, and 4 were from colonies with primary collections in Southern Honshu, central and Pacific coast northern Honshu, and the Sea of Japan coasts of northern Honshu and Hokkaido, respectively. The occurrence of four distinct types of CHC composition suggests that the colonies that produce them are separate species.     

A new timeframe for the diversification of Japan’s mammals

Aim The main Japanese islands are land‐bridge islands divided by the biogeographic division Blakiston’s Line and represent two natural laboratories for studying land‐bridge diversification. Colonization of the current mammal fauna has been dated to the middle to late Pleistocene using fossil evidence. The purpose of this paper is to apply a molecular clock to the genetic divergences between Japanese mammalian taxa and their sister mainland taxa to test the late Pleistocene land‐bridge colonization hypothesis. Location The main Japanese islands (Kyushu, Shikoku, Honshu and Hokkaido). Methods I used mitochondrial DNA (cytochrome b) and a species tree approach to estimate the divergence times of 24 Japanese non‐volant terrestrial mammal taxa and their mainland sister taxa using the program *beast . I then tested for evidence of non‐simultaneous divergence among these taxon‐pairs by controlling for expected coalescent stochasticity using the program Ms Bayes . Results Divergence events between taxa on Japan and their mainland sister taxa were significantly older than expected under the current paradigm, which is based on fossil data. Consistent with the land‐bridge colonization hypothesis, there was evidence of multiple divergence events. Main conclusions These results implicate a colonization timeframe that is older than posited by the current paradigm based on fossil evidence. However, these results are still consistent with the land‐bridge colonization hypothesis. Multiple periods of land‐bridge connectivity may account for the current mammalian fauna in Japan. In addition, half of the divergence time estimates in the Honshu–Shikoku–Kyushu region were clumped around 2.4 Ma, which might suggest a dramatic interchange period, concordant with a period of significant global cooling, when the first land bridge may have connected Japan to the mainland.     

SYSTEMATICS AND PHYLOGEOGRAPHY OF THE INVASIVE RED ALGA, POLYSIPHONIA HARVEYI

Polysiphonia harveyi Bailey was first described from Connecticut in 1848 and morphologically similar species, such as P. japonica and P. strictissima , have subsequently been described many times from different localities such as Japan and New Zealand, placing the taxonomy and nomenclature of this morphologically variable species in confusion. Polysiphonia harveyi is regarded as an alien in the British Isles and the north-eastern North Atlantic and is reported to be spreading rapidly. The first confirmed collection of P. harveyi from the British Isles was in 1908; the source of the British introduction remains unknown. In conjunction with breeding data, rbc L sequences for samples of P. harveyi , P. strictissima , P. japonica and P. akkeshiensis collected from New Zealand, Atlantic and Pacific North America, Japan and Europe, reveal that P. harveyi, P. japonica and P. akkeshiensis constitute a single biological species. The correct name for this is P. harveyi , whilst P. strictissima from New Zealand is a sibling species, distinct from P. harveyi. The center of genetic diversity of P. harveyi is in Japan. The original source of the introduced P. harveyi in the British Isles, Europe and Nova Scotia appears to be Hokkaido, Japan. Separate introductions from a single source population into New Zealand and Pacific and Atlantic North America from Honshu, Japan, apparently have occurred.     

New records and distributions of two North American branchiobdellidan species (Annelida: Clitellata) from introduced signal crayfish, <Emphasis Type="Italic">Pacifastacus leniusculus,</Emphasis> in Japan

This is the first report of two North American branchiobdellidans, Sathodrilus attenuatus Holt, 1981, and Xironogiton victoriensis Gelder and Hall, 1990, on the signal crayfish, Pacifastacus leniusculus (Dana, 1852) introduced into Japan from the Columbia River system, northwestern North America. Signal crayfish from 12 localities in eastern and northern Hokkaido, Japan, were examined and each supported S. attenuatus. In addition, an individual of this species was found on preserved material from Ishikawa Prefecture, central Honshu. All of these branchiobdellidans reported in Hokkaido most probably came from the original population of signal crayfish introduced into Lake Mashu, Hokkaido, Japan, in 1930. It is suggested that the use of non-pathogenic branchiobdellidans, when present, provides an easy method for tracing the spread of crayfishes around Japan and could also be applied in other countries and continents. Specimens of X. victoriensis were only found on crayfish in a stream at Akashina in Nagano Prefecture, central Honshu, Japan. Although the signal crayfish appears to be displacing the endemic Japanese crayfish, C. japonicus, no native branchiobdellidans were found on any of the introduced signal crayfish examined.     

Allozyme Variation among Populations of Rana pirica (Amphibia: Anura)

Genetic variation of Rana pirica , an east Asian brown frog of the R. temporaria group, was elucidated by analysing 140 specimens from 11 populations from Hokkaido and Sakhalin, both locating near the eastern coasts of the Asian continent, and 12 specimens of R. ornativentris from Honshu, Japan mainland, as an outgroup, through horizontal starch gel electrophoresis. Rana pirica shows relatively low genetic differentiation, and high genetic affinities are found between Hokkaido and Sakhalin populations. Populations from these islands are morphologically somewhat differentiated but should be regarded as conspecific. Degree of genetic divergence among populations of amphibian species from Hokkaido, including R. pirica , is not so extensive as that reported for species from Japan mainland and relatively recent formation of amphibian fauna in Hokkaido is suggested.     

Virulence and fitness of the fungal pathogen Entomophaga maimaiga in its host Lymantria dispar, for pathogen and host strains originating from Asia, Europe, and North America

In this study, we tested (1) whether non-North American gypsy moth strains are susceptible to North American isolates of Entomophaga maimaiga and (2) the potential for erosion in the efficacy of E. maimaiga in controlling gypsy moth. We used bioassays to assess the variability in virulence (measured as time to death) as well as fitness of the pathogen (measured as spore production) in four gypsy strains challenged with six E. maimaiga isolates, using host and pathogen strains originating from Asia, Europe, and North America. We found that all E. maimaiga isolates tested were pathogenic to all strains of Lymantria dispar, regardless of the geographical origin of the fungal isolate, with at least 86% mortality for all combinations of fungal isolate and gypsy moth strain. We therefore conclude that Asian gypsy moths are susceptible to North American strains of E. maimaiga. No significant interactions between fungal isolates and gypsy moth strains with regard to time to death were found, indicating that each fungal isolate had the same overall effect on all the gypsy moth strains tested. However, fungal isolates differed significantly with regard to virulence, with a Russian isolate being the slowest to kill gypsy moth (5.1+/-0.1 days) and a Japanese isolate being the overall fastest to kill its host (4.0+/-0.1 days). Fungal isolates also differed in fitness, with variability in types of spores produced. These differences in virulence and fitness were, however, not correlated with geographical origin of the fungal isolate. Gypsy moth strains had no or only little effect on fungal virulence and fitness. Based on our studies with laboratory-reared gypsy moth strains, erosion of successful control of gypsy moth by E. maimaiga seems unlikely.     

Molecular phylogeny and historical biogeography of the Holarctic wetland leaf beetle of the genus Plateumaris

Leaf beetles of the genus Plateumaris inhabit wetlands across the temperate zone of the Holarctic region. To explore the phylogeographic relationships among North American, East Asian, and European members of this genus and the origin of the species endemic to Japan, we studied the molecular phylogeny of 20 of the 27 species in this genus using partial sequences of mitochondrial cytochrome oxidase subunit I (COI) and the 16S and nuclear 28S rRNA genes. The molecular phylogeny revealed that three species endemic to Europe are monophyletic and sister to the remaining 11 North American and six Asian species. Within the latter clade, North American and Asian species did not show reciprocal monophyly. Dispersal-vicariance analysis and divergence time estimation revealed that the European and North America-Asian lineages diverged during the Eocene. Moreover, subsequent differentiation occurred repeatedly between North American and Asian species, which was facilitated by three dispersal events from North America to Asia and one in the opposite direction during the late Eocene through the late Miocene. Two Japanese endemics originated from different divergence events; one differentiated from the mainland lineage after differentiation from the North American lineage, whereas the other showed a deep coalescence from the North American lineage with no present-day sister species on the East Asian mainland. This study of extant insects provides molecular phylogenetic evidence for ancient vicariance between Europe and East Asia-North America, and for more recent (but pre-Pleistocene) faunal exchanges between East Asia and North America.     

Natural enemies and environmental factors affecting the population dynamics of the gypsy moth

The population densities of the gypsy moth (Lymantria dispar; Lepidoptera: Lymantriidae) may reach outbreak levels that pose considerable economic and environmental impacts to forests in Europe, Asia, Africa and North America. Compared with the situation in its native European range feeding damage by gypsy moth is often found to be more severe in North America and other parts of the world. Thus, the release from natural enemies can be interpreted as an important cause for high feeding damages. Natural enemies, especially parasitoids, can cause delayed density‐dependent mortality, which may be responsible for population cycles. In North America where only few parasitoids have been introduced and the parasitism rates are considerably lower than in Europe, generalist predators play a larger role than in Europe. Many other factors seem to influence the population dynamics of the gypsy moth such as the host plants and weather. Nevertheless, much of the variability in population densities of the gypsy moth may be attributed to interacting effects of weather conditions and attack by natural enemies. In spite of the considerable number of studies on the ecology and population dynamics of the gypsy moth and the impact of their natural enemies, more quantitative information is required to predict the population dynamics of this pest species and to control its economic and ecologic impact.