Lepidoptera phyllophages have a significant impact on forest communities. The Siberian silkworm Dendrolimus sibiricus Tschetv. is a dangerous pest moth from the Lasiocampidae family, whose caterpillars feed on the foliage of conifers, mainly from the genera Abies, Pinus, Larix, Picea and Tsuga [1, 2].
Being widespread in Asia: Korea, China, Mongolia, Kazakhstan [3, 4, 5], it penetrated the territory of Siberia (Russia), from where it began to actively settle to the west of the country in the second half of the 20th century, having free access to host plants . Within 25 years, from 1932 to 1957, D. sibiricus damaged 7 million hectares of forests and destroyed 50% of trees in Western Siberia and the Chita region [3, 7]. For the period from 1994 to 1996, D. sibiricus damaged 700 thousand hectares of forest in the Krasnoyarsk Krai , and from 1954 to 1957, it destroyed more than 1.5 million hectares of pine in the area of the Ket and Chulym rivers . In 2001, the activity of the pest was recorded in the Khabarovsk Krai on an area of more than 750 thousand hectares . According to the research of Finnish scientists, the Siberian silkworm was recorded in the Perm Krai near the western foothills of the Ural Mountains . Thus, these data reflect the active migration of the pest, which is a natural way to expand its habitat.
The Komi Republic is located in the northeastern part of the East European Plain. It is bounded from the territory of Siberia by the Ural Mountains in the east. And in the south it borders on the Perm Krai and the Kirov Region, where the presence of the Siberian silkworm has been reliably confirmed . Most of the Komi Republic is covered with forest, the area of which is 28 667.4 thousand hectares. Of the total plantations, spruce stands (Picea sp.) account for 56.4%, pine (Pinus sp.) – 25.5%, other conifers: fir (Abies sp.), larch (Larix sp.), Siberian pine (Pinus sibirica) Du Tour.) – 1.4%, birch (Betula sp.) – 13.2%, aspen (Populus sp.) – 3.4%, other species – 0.1%. The stock of coniferous wood in the forests is 2 356.36 million m³ (83.3%) . The proximity to the Siberian silkworm habitat and the species composition of the Komi Republic forests have become key factors for conducting environmental surveys. The hazard is not limited only to the distribution of silkworms, but also to the formation of the population that gives outbreaks of numbers.
The rapid increase in the number of individuals in the population is due to the peculiarities of the preimaginal stage. Caterpillars usually have a two- or three-year development cycle, depending on the combination of factors [14, 15, 16]. Dry weather periods are largely a prerequisite for the increase in number [1, 17, 18, 19]. In the years of layering of the maturation of adults, an outbreak of the number of individuals occurs, followed by a massive release of caterpillars. Caterpillars of the Siberian silkworm, eating the needles, weaken the plant, and make it easily accessible for subsequent colonization by insects, mainly from the families (Cerambycidae, Buprestidae, Curculionidae)  and pathogenic microorganisms, whose vital activity reduces the quality of products from such wood. In case of severe damage, trees dry out, creating a threat of forest fire . Thus, the Siberian silkworm is a direct ecological threat to the species composition of the forest community and the appearance of upland forests, as well as economic losses due to the deterioration of wood quality and the cost of reforestation.
Being a dangerous defoliator insect, this species currently has a regulatory status and is recognized as a quarantine object [3, 21]. When establishing the scale of its distribution across Eurasia, I was guided by an interactive map from the official website of the European and Mediterranean Organization for Plant Protection (EPPO) (Fig. 1), according to which there is no information on the occurrence of the Siberian silkworm in the European northeast of Russia for 2020 .
At present, the study of the distribution of the Siberian silkworm in the European part of Russia is limited to studies of the more southern regions of the country [22, 23]. The Komi Republic is rich in boreal forests, which can potentially be used by the pest to create a stable population. Lack of attention to the problem of the silkworm dispersal can cause outbreaks of numbers that lead to environmental and economic damage, as is the case of Siberia, as well as further expansion of the species towards Europe.
The study of the dynamics of the number and distribution of the population of individuals is carried out under the Order №23 of the Ministry of Agriculture validating the Regulation on the procedure for monitoring of quarantine phytosanitary state of the territory of the Russian Federation, which approved the procedure for the monitoring of territories . The survey of the forest stands in the Komi Republic was carried out by the Federal Service for Veterinary and Phytosanitary Supervision in conjunction with the All-Russian Center for Plant Quarantine (FSBI «VNIIKR»). For the first time, 48 individuals of the Siberian silkworm were recorded in 2016 on the territory of 7 district forestries out of 12 surveyed . When examining the same sites in 2017, the silkworm was found in all forest districts in the amount of 258 individuals . In 2018, it was decided to expand the surveyed area to 14 district forestries. Analysis of 500 traps revealed 291 specimens of D. sibiricus .
Specially protected natural territories covering an area of 5.5 million hectares should be noted among other woodlands of the Komi Republic. The largest of them are Yugyd Va National Park and Pechora-Ilych Nature Reserve . The Virgin Forests of the Komi Republic are located on the designated areas. They are a UNESCO World Heritage Site and the largest massif of primary boreal forests in Europe, represented mainly by coniferous trees [28, 29]. The invasion of the Siberian silkworm into these ecosystems will cause irreversible catastrophic consequences.
The present study aimed at identifying and counting the number of D. sibiricus adults in the district forestries of the Komi Republic using the glue traps with synthetic sex pheromone in 2020.