Abstract Invasive ants pose a risk to human well-being and social/ecosystem stability. Linepithema humile Mayr is among the most damaging invasive ants worldwide. Most L. humile populations invade ports/wharfs isolated from surrounding landscapes, but unfortunately, a new population was discovered in an inland urban area (Nara Prefecture) of Japan in 2021. In this study, first, the supercolony type of the Nara L. humile population was identified via a hostility test, and then its distribution pattern was characterized. In aggression tests between L. humile from Nara and four supercolonies (haplotypes LH1, LH2, LH3, LH4), this ant showed extremely strong hostility against all supercolonies exept LH2, which was detected only in Japan in its introduced range. In Nara, L. humile was abundant in and around the urban river. Simulations revealed that using this environment for movement/dispersal increased the annual dispersal ability by 14 times compared with that achieved via ground (125 m), as mentioned in the literature. Therefore, river channels can serve as major pathways of long-distance dispersal for L. humile invading inland urban areas. Since applying chemical strategies around rivers is problematic, preventing L. humile from moving to rivers from initial invasion sites is crucial.

Four new saproxylic species of the genus Paranura from Nagasaki, Nara, and Niigata provinces of Japan are described and illustrated in this paper. Paranura tsushimaensis sp. nov. is characterized by a dark blue body color, Abd. V four times as long as Abd. VI, 3+3 eyes, three ocular chaetae on the head, four ordinary chaetae De on Th. III, two ordinary chaetae Di on Abd. V, and all dorsal chaetae of Abd. VI in a unique reticulated plate. P. nakamurai sp. nov. is identified by its yellowish white body color, 2+2 eyes, tubercle Af on the head with two reticulated tubercles, and tubercles Di on Abd. V fused. P. alpicola sp. nov. is characterized by its yellow body color, 3+3 eyes, presence of complete chaetotaxy in the central area of the head, Th. II–III with two and three ordinary chaetae De respectively, and tubercles Di on Abd. V separate. P. convallis sp. nov. is identified by its orange body color, 3+3 eyes, head without chaeta O, three mandibular teeth, and Th. II–III with three and four ordinary chaetae De respectively. A key for all species of the genus Paranura is provided.

Reliable identification of species is important for protecting native ecosystems against the invasion of non-native species. DNA barcoding using molecular markers, such as the mitochondrial cytochrome oxidase subunit 1 (COI) gene, helps researchers distinguish species. In this study, we focused on introduced veronicellid slugs in the Ryukyu Islands and some greenhouses on mainland Japan. Some veronicellids are medium-to-high risk pest species for humans. Identifying veronicellid species by their external morphology is difficult and unreliable because there is substantial overlap between intraspecific variation and interspecific differentiation. Therefore, internal morphologies such as male genitalia have been the primary traits used to distinguish veronicellids. To identify introduced veronicellid slugs in Japan to the species level, we used morphological assessment of male genitalia and DNA barcoding of the standard COI gene fragment. We also conducted species-delimitation analyses based on the genetic data. The results showed that five evolutionarily significant units, corresponding to four nominal species inhabit the Ryukyu Islands, of which two species were also found in the greenhouses of mainland Japan, including the first record of Sarasinula plebeia in Japan. The presence of non-native slug species could increase the transmission of parasites in Japan.

Strategic responses to invasive Latrodectus widow spiders are a global challenge due to the risks they pose to health and ecosystems. Chemical strategies involving the use of pyrethroids are effective against adult spiders, but as their populations rebound, chemical control becomes costly and unsustainable for eradication. A major obstacle is the inefficacy of insecticides against eggs, which are covered by a protective silk egg sac. Eradication of invasive spiders must focus on destroying progeny. Here, the responses of eggs in egg sacs of two invasive Latrodectus spiders in Japan (Latrodectus hasseltii (Thorell) and Latrodectus geometricus (C.L. Koch)) to short-term dry-heat exposure were examined. To test whether the dry-heat tolerance of the egg sacs of both spider species differed, lethal temperature (LT) was determined based on the hatching rate of eggs from egg sacs subjected to a range of temperatures. Hatching in both species failed completely when the egg sacs were exposed to temperatures of 55°C and above for 10 min, but the LT to reduce hatching by 90% (LT90) differed significantly between L. hasseltii (50. 9°C) and L. geometricus (52. 8°C). Our study highlights the efficacy of dry heat in suppressing hatching and thus shows the possibility for effective extermination of these noxious invasive pests. Further exploration and investigation of the effects of humidity and heat exposure time on egg sacs under field conditions are needed to guide Latrodectus spider control strategies.

The Argentine ant, Linepithema humile Mayr, has spread to almost all continents. In each introduced region, L. humile often forms a single large colony (supercolony), the members of which share the haplotype “LH1”, despite the presence of other supercolonies with different genetic structures. However, the mechanisms underlying the successful invasion of LH1 ants are unclear. Here, we examined whether diet breadth differs between more successful (LH1) and less successful (LH2, LH3, LH4) L. humile supercolonies in Japan to better understand the processes responsible for invasion success. The standard ellipse areas (SEAs) of δ¹³C and δ¹⁵N and their ranges (CR and NR) were used as diet breadth indices. The SEAs of LH1 were much larger than those of the less successful supercolonies despite no differences in the baseline SEAs of arthropods within the supercolony habitats, indicating that the invasion success of a supercolony is associated with its diet breadth. Furthermore, LH1 had a broader CR than the other supercolonies, suggesting that which might be derived from superior resource exploitation ability. Our study highlights the importance of focusing on intraspecific differences in diet breadth among supercolonies when assessing organisms that can potentially invade and become dominant in new habitats.

[Synopsis] We newly collected Dermestidae insects included four species of Dermestidae insects, Anthrenus tanakai, Orphinus japonicus, Thaumaglossa hilleri, and Trogoderma longisetosum from gypsy moth egg batch in Japan. This was the first report regarding these four Dermestidae species as the predators of gypsy moth egg batch.

[Synopsis] We studied the differences in the number of egg batch laid by gypsy moth in the uniform wooden shelters with or without lighting during their low-density periods from 2018 to 2020 in Nara campus of Kindai University. The egg batches were only observed in the shelters without lighting, and neither egg batch nor the field sign indicating the arrival of the female moth were found in the shelters with lighting among three years. We discuss the effect of lighting on the egg laying of gypsy moth during their low-density periods.

Prompt responses to invasive Latrodectus spiders introduced unintentionally are needed worldwide due to their medical and ecological importance. Latrodectus species are chemically controlled using pyrethroid insecticides despite concerns about the ecological impacts of these compounds on biodiversity/ecosystems. Here, the relative sensitivities (acute toxicity: 48-h LC50) of Latrodectus hasseltii Thorell and Latrodectus geometricus C.L. Koch from Japan to the conventional neurotoxic insecticide bifenthrin (pyrethroid) and a new candidate insecticide, fipronil (phenylpyrazole), were examined. Acute residual toxicity tests of these compounds in two nontarget spiders (Parasteatoda tepidariorum C.L. Koch (Araneae: Theridiidae), Badumna insignis L. Koch (Araneae: Desidae)) were conducted for comparison. To test whether bifenthrin and fipronil toxicities differed among the four spiders, corresponding species sensitivity distributions (SSDs) were compared, and hazardous concentrations were determined. Sensitivity (especially in the nontarget species) was two to four orders of magnitude higher for bifenthrin than for fipronil. The SSD patterns of the two insecticides differed significantly, with the spider communities being more sensitive to bifenthrin than to fipronil. The lethal bifenthrin concentration for Latrodectus may reduce spider populations by over 70-90%. If L. hasseltii (established throughout Japan) is targeted for effective population suppression rather than L. geometricus (with a limited distribution range) using the specified insecticide concentration (LC50 value) for fipronil, less than 20% of spider communities will be impacted. Chemical operations aimed at the effective population management and subsequent eradication of invasive Latrodectus spiders while supporting local biodiversity conservation would benefit from considerations of fipronil dosages and target species sensitivities.

Linepithema humile is one of the most damaging invasive species worldwide. Although chemical control strategies have proven effective for L. humile, the susceptibility of these invasive ants to the insecticide fipronil differs markedly among genetically different supercolonies. In Japan, five mitochondrial L. humile haplotypes were identified from eleven prefectural regions and cities as of 2010. In 2012, a new population was found in Okayama Prefecture. Here, we analyzed mitochondrial DNA from L. humile workers from the Okayama population to better understand the genetic structure of ants in Japan and develop effective control strategies. According to COI-COII and cytochrome b gene sequences, the L. humile Okayama population haplotype was consistent with the 'Japanese main' supercolony-the most invasive supercolony worldwide. Hence, we believe that the Okayama population (Japanese main supercolony) can be easily eradicated because of its early invasion stage, relatively limited distribution range and high sensitivity to fipronil.

The Argentine ant, Linepithema humile (Mayr Hymenoptera: Formicidae), is one of the world's most hazardous invasive species, and thus its eradication from Japan is important. Physical and chemical controls can be expensive and cause strong adverse effects on local terrestrial ecosystems regardless of their high efficacy. Here, presence/ absence of host-tree selection by Argentine ants was investigated to understand the ant-honeydew-producing insects interactions in order to develop new cultural controls compatible with biodiversity conservation. Abundance of Argentine ants and their tree utilization ratio was measured among dominant roadside trees (Cinnamomum camphora, Myrica rubra, Nerium indicum, Rhaphiolepis indica var. umbellata, Juniperus chinensis var. kaizuka) in two areas around Kobe, Japan. Almost all ants collected were Argentine ants suggesting that native ants would have been competitively excluded. Tree utilization of Argentine ants clearly differed among host trees. Abundance of both Argentine ants and honeydew-producing insects and tree utilization rate of the ants were significantly lower in especially C. camphora and J. chinensis. Few Argentine ants were observed trailing on C. camphora, J. Chinensis, and N. indicum, most probably due to low abundance of honeydew-producing insects on these trees with the toxic and repellent chemical components. On the other hand, high abundance of both Argentine ants and homopterans were found in M. rubra and especially R. indica. We suggest that reductions of R. indica and M. rubra would lead to a decrease in abundance of honeydew-producing insects, and thus effectively control populations of Argentine ants. At the same time, planting of C. camphora, J. Chinensis, and N. indicum may also play a role in restraint efficacy against invasion of the invasive ants.

Fipronil is one of the most effective insecticides to control the invasive ant Linepithema humile, but its effectiveness has been assessed without considering the genetic differences among L. humile supercolonies. We hypothesized that the susceptibility of the ant to fipronil might differ among supercolonies. If so, dosage and concentration of fipronil may need to be adjusted for effective eradication of each supercolony. The relative sensitivities of four L. humile supercolonies established in Hyogo (Japan) to fipronil baits were examined based on their acute toxicity (48-h LC50). Toxicities of fipronil to seven ground arthropods, including four native ant species, one native isopoda, and two cockroaches were also determined and compared to that of L. humile supercolonies using species sensitivity distributions. Marked differences in susceptibility of fipronil were apparent among the supercolonies (P < 0.008), with the 'Japanese main supercolony' (271 mu g L-1) being five to ten times more sensitive to fipronil than other colonies (1183-2782 mu g L-1). Toxicities to non-target species (330-2327 mu g L-1) were in the same range as that of L. humile, and SSDs between the two species groups were not significantly different (t = -1.389, P = 0.180), suggesting that fipronil's insecticidal activity is practically the same for L. humile as for non-target arthropods. Therefore, if the invasive ant is to be controlled using fipronil, this would also affect the local arthropod biodiversity. Only the 'Japanese main supercolony' can be controlled with appropriate bait dosages of fipronil that would have little impact on the other species.

As part of a clarification of the response mechanisms of beach ground arthropods to the 2011 Tohoku-oki tsunami, a pit-fall trap survey was conducted in August and September 2012 and 2013 on four relatively flat sandy beaches in northern Tohoku region (i.e., northern Iwate to southern Aomori Prefecture) in Japan. At each beach surveyed, eight clean plastic cups with no baits were put for two days on each of the five beach zones (i.e., wrack, non-vegetated, short-herbaceous, tallgrass, and shrub zones). Among the ground arthropods in this study, we report the differences in susceptibility of two sandhoppers (Trinorchestia trinitatis and T. longiramus), which dominate on the beaches and play an important role as prey for beach predators, to the tsunami, through monitoring their population dynamics. Although the abundance of the two species increased with time after the disturbance, T. trinitatis had a higher population growth rate than T. longiramus. In 2012, these two talitrid amphipods were collected mostly in the wrack zone, where the seaweed and driftwood accumulated, and on the non-vegetated zone near the shoreline, whereas they occurred in all beach zones in 2013. Since T. trinitatis burrows near the beach surface during its reproductive period in spring, this species might have suffered a large impact from the tsunami's coastal erosion. On the other hand, our findings suggest that Trinorchestia species rapidly recolonize coastal regions in a short period of time (within a year), due to their reproductive ability and the accumulation of sea wrack, which provides food and habitat to these sandhoppers.

In general, mycoviruses are transmitted through hyphal anastomosis between vegetatively compatible strains of the same fungi, and their entire intracellular life cycle within host fungi limits transmission to separate species and even to incompatible strains belonging to the same species. Based on field observations of the white root rot fungus, Rosellinia necatrix, we found two interesting phenomena concerning mycovirus epidemiology. Specifically, apple trees in an orchard were inoculated with one or two R. necatrix strains that belonged to different mycelial compatibility groups (MCGs), strains W563 (virus-free, MCG139) and NW10 (carrying a mycovirus-like double-stranded (ds) RNA element (N10), MCG442). Forty-two sub-isolates of R. necatrix, which were retrieved 23 years later, were all genetically identical to W563 or NW10: however, 22 of the sub-isolates contained novel dsRNAs. Six novel dsRNAs (S1-S6) were isolated: S1 was a new victorivirus; S2, S3, and S4 were new partitiviruses; and S5 and S6 were novel viruses that could not be assigned to any known mycovirus family. N10 dsRNA was detected in three W563 sub-isolates. These findings indicated that novel mycoviruses, from an unknown source, were infecting strains W563 and NW10 of R. necatrix in the soil, and that N10 dsRNA was being transmitted between incompatible strains, NW10 to W563.

Filenchus discrepans ingested hyphal contents of Botrytis cinerea without killing the hyphal cells that they fed on. Individuals of this nematode penetrated B. cinerea hyphae with their stylets, after which intense pulsation of the median bulb and dorsal gland duct followed (indicating salivation). In addition, light pumping of the median bulb (indicating food ingestion) was also observed. Fungal cells continued to show cytoplasmic streaming while the nematode ingested hyphal contents. Moreover, actively growing tips of the hyphae usually continued their growth during and after cytoplasm ingestion by the nematode. In less active, older hyphae the penetrated tip cells stopped growing during nematode feeding. However, the majority of the tip cells resumed growth after feeding by the nematode. The hyphal tips often exhibited an abnormal shape during nematode feeding and gradually regained normal shape and growth afterwards. The growth rate of hyphal tip cells decreased to less than 10% compared with the growth of intact hyphal tip cells during attack by F discrepans, which often fed on a hyphal cell for up to 3 h. Filenchus discrepans propagated well in B. cinerea cultures and their population growth rate ranged between six- and 11-fold 1 month after incubation. This is the first report of nonlethal ectoparasitism by a mycophagous nematode, showing that the nematode does not kill fungal cells during and after feeding.

A colony-print immunoassay (CPIA) using an anti-dsRNA antibody was developed to visualize the distribution of four unrelated mycoviruses with dsRNA genomes, a partitivirus (RnPV1), mycoreovirus (RnMyRV3), megabirnavirus (RnMBV1), and an unidentified virus (RnQV1), in mycelia of the white root rot fungus, Rosellinia necatrix. CPIA revealed different distribution patterns within single colonies for each virus. Both RnPV1 and RnMBV1 were distributed throughout single colonies, RnMyRV3 was absent from some colony sectors. and RnQV1 exhibited varied accumulation levels between sectors. RnMyRV3 and RnQV1 were transmitted to the recipient virus-free colonies of virus-infected and virus-free colony pairs more slowly than were RnPV1 or RnMBV1. The presence of RnMyRV3 in recipient colonies restricted horizontal transmission of RnPV1 and RnMBV1. These results imply that one or more mechanisms are present in host-virus and virus-virus interactions that restrict the spread of viruses within and between colonies. (C) 2010 Elsevier Inc. All rights reserved.

To evaluate the lethal effects of the violet root rot fungus, Helicobasidium mompa growing on potato dextrose agar on Collembola, three species of collembolans, Proisotoma minuta, Hypogastrura communis, Folsomia candida were introduced on the agar cultures of H. mompa. Proisotoma minuta showed the lowest survival rate in H. mompa culture, and we examined the numbers and gut contents of P. minuta released in H. mompa culture using the cellophane method to evaluate the lethal effects of non-volatile metabolites. These experiments revealed that mycelia of H. mompa growing on cellophane were weakly lethal (51-99% survival), while the PDA under the cellophane was highly toxic (3-21% survival) to P. minuta. Investigation of collembolan gut contents indicated that individuals on H. mompa mycelia fed on hyphae, while the majority of those on the PDA surface died without ingesting any agar. The present study suggests that the Collembola died from exposure to a toxic metabolite(s) produced by H. mompa that had accumulated in the agar media, in spite of this fungus' availability as their diet. They would absorb the toxic metabolite(s) by non-orally way through body contact with the agar media, possibly through the ventral tube.

Due to the abundance of wild mammals that are of the nocturnal type, elementary and junior high school students have generally not been able to study them through observation. Through a joint-partnership with various schools, we utilized sensor cameras to observe wild mammals. Many pictures of 17 mammal species were taken. From these pictures, the children were able to understand more about the wild mammals inhabiting the surrounding vicinity of their homes. They could also learn the ideas of bio-diversity, phenology and habitat use in relation to those mammal species. As the children observed and learned about the wild mammals, their interest in the natural environment and mammals grew exponentially. With the cooperation between the museum and schools, we utilized researching tools such as sensor cameras, making it possible for elementary and junior high school students to learn about wild mammals in a more effective way.

Two major volatiles produced by the mycelia and fruiting bodies of Tricholoma matsutake (1-octen-3-ol and methyl cinnamate) repel a mycophagous collembolan, Proisotoma minuta. Aggregation of the collembolans on their diet was significantly inhibited by exposure to 1 ppm methyl cinnamate or 10 to 100 ppm 1-octen-3-ol. The aggregation activity decreased dose-dependently upon exposure to 1-octen-3-ol at concentrations higher than 0.01 ppm. Aggregation in the presence of methyl cinnamate exhibited three phases: no significant effect at concentrations ranging from 0.001 to 0.1 ppm, significant inhibition from 1 to 100 ppm, and strong inhibition at 1,000 ppm. These results may explain why certain collembolan species do not prefer T. matsutake fruiting bodies. © 2007 The Author(s).

The purpose of the research is to clarify the relationship among the three factors; landscape quality, forest environment and forest stand composition with in a forest, by finding out what element of a forest environment generates comfort, and what composes within a forest environment. The forest paths of 90 years red pine forest stands (A & B) and 45 years red pine forest stand (C) (hereinafter called A, B and C) in Oshiba Park in Minami Minowa Village located in southern Nagano Prefecture, were surveyed as its research zone. B scored the highest comfort rating, and the evaluation factor leaned on the visual sense, which could be an easy-to-sense advantaged asthenia. And it has revealed that two important factors were the scenic attraction of the trees, and the random sunlight beaming through the leaves, which is appeared to be related to the fact that the kind and individual size of trees in B vary. As observed above, the two key factors have become apparent . 1.The forest environment, which governs the comfort level of an individual forest, depends on its forest stand composition.2. Although it is still used as the prime aesthesia, people value the conform level not only with their visual sense, but also with their all five senses.

We examined influences of trampling and wood-chip mulching on soil animal fauna in a Japanese beech forest with utilization as a sightseeing spot. Three study sites; a trampled area with wood-chip mulch, a trampled area with leaf litter, and a control area were settled in a beech forest. The hardness of soil and the soil fauna were compared among the three study areas on 7 September and 24 November in 2005. The hardness of the soil was significantly large in the order as the trampled area with wood-chip mulch, the trampled area with leaf litter and the control area. From the survey on soil fauna, Pseudoscopiones and Harpacticoida were not observed in both trampled areas on 7 September and 24 November in 2005. The number of families of oribatid mites and that of collembolan species were larger in the control area than those of trampled area. Diversity of collembolan species the soil was high in the order as the control area, the trampled area with leaf litter and the trampled area with wood-chip mulch.

The total number of collembolans collected from the hyphal mat of the ectomycorrhizal fungus Sarcodon scabrosus was less than half of that collected from the adjacent non-mat soil. The same was true of all families of collembolans except one, although not all differences were significant. The exception was the Hypogastruridae, with more individuals in the hyphal mat on the sampling day in the fruiting season these were also the most abundant collembolans on the fruiting bodies. These results indicate that most collembolans avoid the hyphal mat of S. scabrosus in a Japanese red pine forest. © 2007 The Mycological Society of Japan and Springer-Verlag.

The number of collembolans collected from hyphal mat soil of ectomycorrhizal fungus, Tricholoma matsutake was examined to investigate whether the ectomycorrhizal mat always includes larger numbers of collembolans than did the non-mat soil. The number of collembolans collected from hyphal mat soil did not differ significantly from that from the adjacent non-mat soil in most case. The temporarily aggregation of Isotomidae collembolans on hyphal mat of T. matsutake were observed on 2 December 2002, though the number of collembolans collected from the hyphal mat soil did not differ significantly from those collected from the adjacent non-mat soil because of a wide range of variety of the data. Fungal materials contained in the gut of the Isotomidae population consisted mostly of hyphal fragments of dematiaceous fungi and unknown basidiomycetes. Since the hyphae of T. matsutake seem to play a small role as a food resource for collembolans in the field, the existence of the hyphal mat of T. matsutake did not affect the number of collembolans inhabiting the soil. (c) 2006 Elsevier Masson SAS. All rights reserved.

Interaction between oribatid mites and ectomycorrhizal fungi has been observed in laboratory choice experiments but not in field. The author investigated on the interaction between oribatid mites and ectomycorrhizal fungi through the field surveys on abundance of oribatid mites inhabiting in the hyphal mat and fruit bodies of ectomycorrhizal fungi in a Japanese beech forest in Niigata prefecture. Among 8 fungal species, only Sarcodon scabrosus and Phellodon melaleucus (Telepholaceae) fruit bodies contained many oribatid mites, which were mostly comprised of Carabodidae (mainly Carabodes rimosus) individuals. The number of whole oribatid mites collected from the hyphal mats under the fruit bodies of S. scabrosus and P. melaleucus did not differ from the number collected from the adjacent non-mat soil. The average number of oribatid mites collected from the mat was less than half of that collected from the adjacent non-mat soil in most families except for Carabodidae and Oppiidae, though the decrease was not always statistically significant. The average number of Carabodidae did not decrease and Oppiidae only slightly decreased in the hyphal mats. It is concluded that Carabodidae and Oppiidae contained species associate with Telepholoid mycorrhizal fungi.

On the gill surfaces of agaric fruit bodies fed on by Collembola, the hymenium layer was consumed and many fecal pellets containing many basidiospores were observed. The hymenial area consumed by a collembolan (=Hypogatsrura denisana) varied from 1% to 92%, correlating with the density of collembolans on each fruit body among 11 agaric species. In Lactarius quietus, the hymenial area consumed by collembolans varied from 30% to 69% during the 5 days during which sampling took place. A weak correlation was found between the ratio of the hymenial area and the density of collembolans on the fruit bodies, and this fact suggested that other factors influenced the ratio of the hymenial area consumed by collembolans. © The Mycological Society of Japan and Springer-Verlag 2006.

Seasonal change in morphology was observed in the winter-active collembolan Hypogastrura bokusi from November to January in Central Japan. In December and January, all individuals of H. bokusi (1.0-1.6mm in body length) observed were dark purple, and the mucro had apical teeth prominently projecting forward. Two conspicuously high papilla-like granules were present near the distal end (winter form). In November, the color of the individuals with a body length less than 1.2mm in body length was brown while that of those more than 1.2mm in body length was dark purple. Their mucro lacked the apical teeth and the two high granules were not conspicuous (autumn form). Thus, a remarkable darkening in color, enlargement of granules of dens, and morphological change in mucro were cyclomorphic ones possibly an adaptation its snow surface activity.

Proturans (Acerentulus omoi Imadate and Yamatetomon yamato Imadate et Yosii) were collected from the ectomycorrhizal mat of Sarcodon scabrosus and Tricholoma matsutake and adjacent non-mat soil in a Japanese red pine forest. A small number of proturans was collected from the mat of S. scabrosus formed in the Ao layer, and the number differed significantly from that collected from adjacent non-mat soil. The numbers of proturans collected from the mat of T. matsutake and the Ao layer above the mat did not differ from those collected from the adjacent non-mat soil in most cases. These facts suggested that an ectomycorrhizal mat does not always provide a suitable habitat for proturans in the field.

Hypogastrura bokusi were observed to assemble on rotten plant materials fallen on snow such as bark, branches, seeds, and leaves. From fifty-two to eighty-eight percent of H. bokusi individuals examined had gut contents, and the gut contents consisted of the hyphal fragments and spores of fungi. From 13 January to 28 February (47 days) in 2003, the major size class of the population increased their size range from 1.0-1.2mm to 1.3-1.5mm (=body sizes of the adults), and the growth rate of this Collembola in this period is calculated 0.002mm to 0.011mm per day. The mycophagy of H. bokusi on snow is related to their growth in winter in Central Japan.

The numbers of the collembolans and the differences in the numbers among the mushrooms depending on their height from the ground surface. Takuo SAWAHATA (Outdoor Education Research Foundation, 5992-1 Yamamoto, Iida, Nagano, 395-0244 Japan), Hideyuki OZAWA, Kiyoshi SOMA^* and Masatake Ohmasa, (Faculty of Agriculture, Shinshu University, 8304 Minami-minowa, Nagano, 399-4598 Japan). We examined the composition of Collembola on shiitake mushrooms growing on bed-logs, the seasonal changes in the numbers of the collembolans and the differences in the numbers among the mushrooms depending on their height from the ground surface. Hypogastrurids occupied more than 99% of collembolan populations in the cases of the mushrooms growing on the bed-logs and those on the ground surface. Most of them were Hypogastrura denisana. Large numbers of H. denisana were observed on the mushrooms on the bed-logs and the ground surface in spring and especially in autumn. Lots of H. denisana were observed on the mushrooms growing at near the ground surface in spring. In autumn, a large number of H. denisana were observed on the mushrooms in higher places, even on one mushroom on 30 cm above the ground surface. More than half of the collembolan populations on the mushrooms were occupied by individual collembolans 0.4-0.7 mm in body length in spring and those more than 0.7 mm in body length in autumn.

幼生生殖とは、幼虫または蛹段階で卵巣が発達し、「母幼虫」または「母蛹」が「子幼虫」を産生するという特殊な繁殖様式であり、昆虫では甲虫目で1種とハエ目タマバエ科の複数種でしか確認されていない。 これまで日本国内では、海外産の菌糸由来とみられるきのこ栽培施設内でしか幼生生殖タマバエは確認されていなかった。本研究により、国内各地の土着きのこ類から幼生生殖性を示す様々なタマバエを発見し、多くの系統についてエノキタケ菌糸を用いた累代飼育に成功した。 これまでのところ、国内にはMycophila属, Heteropeza属、Leptopsyna属など、少なくとも５属のタマバエが生息していることが判明した。これらに加えて、未だ成虫が得られておらず、属の所属が未解明の種も確認されていることから、日本国内に多様な幼生生殖タマバエが生息しているという実態が明らかになってきた。 2021年度は、得られたタマバエ類の分類学的地位の精査、発育増殖特性の調査、モード転換機構の解明に向けた実験を進めた。 Mycophila属の一種に関しては、同属の既知種と形態的特徴を比較した結果、未記載種の可能性が高いことが判明した。また、温度別に飼育実験を行い、温度が発育増殖に及ぼす影響を明らかにした。本種は27℃付近でもっとも増殖速度が速いことや、30℃では発育遅延が生じることなどを明らかにした。また、幼生生殖時の世代期間、発育ゼロ点、有効積算音量などを産出した。

本研究は、2015年に鹿児島県口永良部島で発生した噴火直後の特異な現象、すなわち一次遷移の一般的な先駆植物に先立ってクロマツを主体とした「樹木」が広域に侵入したメカニズムを解明するにあたり、地上部－地下部の関係性から議論することを目指すものである。 研究2年目は、前年度に引き続き、撹乱跡地における植生（植物種子を含む）、菌根菌および種子・菌根菌散布者等の調査を実施した。なお、コロナ禍で当初計画を達成したとは言い難い。各項目の成果は以下の通りである。 1）植生（植物種子を含む）調査および地形測量： 森林域において、森林を対象として植生調査と埋土種子調査を行った。照葉樹二次林、スギ植林、火砕流跡地の各林分間で、植物の種組成と種多様性を比較した。結果、火砕流攪乱後の植生回復過程では、シカの不嗜好種である低木とシダ植物の優占度が著しく大きいことが明らかになった。同様の傾向は埋土種子集団でもみられ、火砕流による攪乱が種多様性、特に均等度の低下を引き起こしている可能性が示唆された． 2）菌根菌調査： 火山泥流跡地に生育する1-4年生クロマツの外生菌根菌群集を調査した。その結果、マツ科樹木に特異性の高いショウロ属・ヌメリイグチ属やアテリア科が高頻度で検出された。 3）種子・菌根菌散布者（主に節足動物）調査： 引き続き、火砕流跡地およびその周辺で土壌動物調査を行った。前年度と同様、火砕流跡地で土壌動物があまり得られなかったことから、火砕流跡地のような未成熟土壌は、土壌動物の生息環境としては不適、または侵入できても定着できにくい場である可能性が示唆された。 4）群集解析等： 口永良部島における既存の生物データを用いて、群集組成におよぼす噴火前の植生履歴と火山攪乱のタイプの効果について予備解析を行った。その結果、植生履歴と火山攪乱のタイプの双方が群集組成に影響をおよぼす可能性が示唆された。

(1) 局所スケールでのマイマイガおよび天敵の発生動態：2019年6月に、北海道美瑛町の市街地から山間部へと直線的に通る約25 kmの道路に沿って2 kmから6.7 kmごとに設定した6地点で個体数調査を実施した。マイマイガ幼虫は、山の麓にある中標高（地点5）、所謂「高原」で多く発生し、高標高の森林および低標高の市街地では少ないことが分かった。前年に比べ、2019年は個体数が全体的に少なかった。また天敵相のほとんどは寄生バエと寄生蜂であったが、地点5のみウイルス感染致死がみられた。 (2) 広域スケールでのマイマイガの発生動態： (1)の6地点それぞれに定点カメラを複数ヶ所設置したが、マイマイガの食害による落葉が観察できなかった。そこで、衛星画像データ解析による食害域・非食害域の識別が可能か調べるため、ドローンで撮影されたロシアでのマイマイガ大発生によるシラカバ林食害域周辺の斜め写真を基に、同時期に観測された衛星画像を解析した。この結果から、NDVI値の違いから食害の影響を識別できることが分かった。 (3) マイマイガの密度依存的な生態・生理的形質の変異：マイマイガ発生動態の不安定期における生態・生理的形質の変化を検出するため、室内で餌制限試験(通常の餌量の半分)と密度効果試験(異なる個体数で飼育)を行い、メスの各パラメータを計測した。またメス成虫の腹部につり糸を結び、羽ばたく時間を測定した。その結果、餌制限区では羽化後のメス成虫の体重が軽かったが、産卵後の体重には有意差がなかった。産卵数は餌制限区で対照区よりも有意に少なかった。一方、個体あたりの最大飛翔時間は餌制限区で長い傾向があった。密度効果試験の結果も同様であった。餌不足はマイマイガメスにおいて卵への投資を減少させ、より飛翔能力が高くなることにより、広域への分散を可能にしているかもしれない。