Entomological Science最新文献

Bagworms constantly carry a portable bag with their prolegs inside, even when walking. Therefore, bagworms have a unique walking style. Bagworms construct footholds with silk and walk using only their thoracic legs. Bagworms build their bag immediately after hatching and carry them for the rest of their lives. Therefore, the only period when they move without a bag is immediately after hatching, when they move away from the hatched egg. We assessed their movement behavior in the period immediately after hatching when all legs were available, including prolegs. Our observations revealed that hatching Eumeta variegata (Japan's largest bagworm species) spun foothold silk threads even as they left the egg. From the moment the head broke out of the egg, larvae began spinning foothold silk threads. To do this, larvae twisted their anterior regions approximately 90° immediately before hatching. This finding indicates that larvae prepare to spin foothold silk threads during embryonic development.

Herbivore outbreaks cause serious damage to forest trees. In recent decades, outbreaks of the gall midge Schizomyia castanopsisae (Diptera: Cecidomyiidae) inducing inflorescence galls on Castanopsis sieboldii (Fagaceae) occurred in the Izu Islands, Tokyo, Japan. We investigated the gall density on the islands and estimated the larval population on Miyakejima Island. We also surveyed seasonal changes in larval age structure, presence of natural enemies, larval cold tolerance, and thermal effects on the adult emergence. In addition, we conducted molecular phylogenetic analyses of S. castanopsisae populations among different localities. The gall density was particularly high in southern parts (from Miyakejima to Aogashima) of the Izu Islands. The gall midge seemed to have been expanding its range toward northern parts in recent years. On Miyakejima, the larval population was estimated to be approximately 158 and 36 bn in 2017 and 2018, respectively. Parasitoids were not found in the dissection of galls. A cold temperature treatment did not affect the percentage of adult emergence. Developmental zero and thermal constant during the period from larval departure to adult emergence were estimated to be 4.7°C and 588.2°C-days in males and 7.4°C and 476.2°C-days in females, and the adults were predicted to emerge in April. Populations in Kyushu were genetically distinct from those in Okinawajima and the Izu Islands, but a common haplotype was found between the latter two localities. These imply that S. castanopsisae on the Izu Islands may be a recent invasion, and the absence of natural enemies causes its outbreaks.

The Argentine ant (Linepithema humile) is an invasive species that rapidly enters into new areas, causing worldwide ecological concern. Early assessment of its potential habitat could indicate areas that we need to pay attention to in advance, to prevent its invasion; therefore, in this study we aimed to predict the potential spatial distribution of the Argentine ant and analyze the climatic characteristics of its occurrence sites. The CLIMEX model was used to predict the spatial distribution of this ant species, while the probability density function was employed to extract climatic preferences in places where their main habitats are located. High climatic suitability was predicted in the eastern United States, eastern South America, central Africa, eastern Australia, and a few regions in India and China, suggesting the high possibility of its invasion worldwide. The frequency of occurrence was highest at approximately 20°C monthly average maximum temperature, 8°C monthly average minimum temperature, and 10 mm monthly precipitation. In addition, the occurrence records of Argentine ants were mostly shown to be above sub-zero temperatures. We expect that these results can be used to identify new areas exposed to the risk of Argentine ant invasion and for further application to establish monitoring strategies in advance.

Riptortus pedestris is one of the most destructive pests of leguminous crops in East Asia. In this study, we assessed the effect of different leguminous plant species, including soybean, wild soybean, white kidney bean, runner bean, pea, cowpea, adzuki bean, mung bean, faba bean, and lentil vetch, on the development and reproduction of R. pedestris. We found that leguminous plant species significantly affect the developmental duration and survivability of the nymphs, adult longevity, and oviposition and fecundity in R. pedestris. The nymphs completed their development on all of these plants. The developmental duration of nymphs was the shortest (16.24 ± 0.57 days) on soybean and the longest (31.33 ± 1.76 days) on faba bean. The rates of survival of nymphs on soybean and pea were 93.2% and 93.0%, respectively. Female adults survived the longest on soybean (64.67 ± 6.64 days) and the shortest (13.27 ± 3.67 days) on white kidney bean. The fecundity on faba bean (decorticated pods) (143.0 ± 28.04 eggs) and soybean (116.63 ± 12.76 eggs) was higher than those on other plants. The age-specific life table revealed that the population trend index values were all >1 except on wild soybean and faba bean, and the highest was on soybean (30.36), followed by pea (21.0). Soybean and pea were identified as the most suitable hosts for R. pedestris because of their shorter developmental duration, higher survivability, longevity and fecundity and greater population trend index on these hosts, while wild soybean and faba bean were relatively unsuitable host plants.

The ability of some organisms to manipulate the behavior, physiology, and morphology of other individuals to increase the chances of survival and reproduction is well known among animals with a parasitic lifestyle. In the present study we (i) report the interaction between the parasitoid wasp Eruga unilabiana and the host spider Eurymorion sp. (Linyphiidae) for the first time (plus Sphecozone sp. (Linyphiidae)), (ii) describe the normal and cocoon webs of Eurymorion sp. induced by larvae of the penultimate instar of E. unilabiana, (iii) quantify the differences between the structures of normal and cocoon webs of Eurymorion sp. and Sphecozone sp. spiders, and (iv) describe the behavior of two spider species under influence of the penultimate instar larvae of E. unilabiana. The cocoon webs built by parasitized Eurymorion sp. are structurally similar to those of Sphecozone sp. induced by the same parasitoid species. The areas of the sheets and the length of the interception threads of the cocoon webs were significantly smaller than those of normal webs. Several individuals of the two species of host spiders are induced to abandon their normal webs to build a cocoon web from scratch, a rare behavior in non-parasitized individuals.

Sexual dimorphism in timing of adult emergence is common in insects. In most insects, males emerge before female (protandry), however, some insects show earlier female emergence (protogyny). Here, I report the effects of photoperiod on protogyny in the lawn ground cricket (Polionemobius mikado). Upon exposure to different photoperiods at 26 °C, P. mikado females were found to emerge earlier than the males in the short-day photoperiod. However, no difference in the nymphal development duration was observed between the sexes in the long-day photoperiod. Protogynous development is expected to be more pronounced in the crickets that eclosed later in the year than those that eclosed earlier; therefore, its adaptive significance is closely associated with environmental seasonality that is encountered by the eclosed females.

This study examined the life history traits of Aphis coronillae Ferrari (Hemiptera: Aphididae) clones collected in Utsunomiya City, Tochigi Prefecture, eastern Japan. Results showed that the collected clones are classifiable into two life cycle forms: holocyclic and anholocyclic. No significant difference in nymphal development, fecundity, or adult longevity was observed between holocyclic and anholocyclic clones. Results also indicated that photoperiod and temperature affect sexual morph production in holocyclic clones.

We identified an alien praying mantis found in Japan as the giant Asian mantis Hierodula chinensis by observing the characteristics of male genitalia. Nymphs hatched from oothecae collected in Nara Prefecture, Japan, were reared in a breeding room and compared with nymphs of the native Japanese species H. patellifera. Different from H. patellifera, the H. chinensis individuals passed through 5–7 nymphal instars before emerging as adults. The body color of the H. chinensis nymphs was brownish gray in the first instar, whereas the second and later instars were green. Unlike H. chinensis, H. patellifera had mottled patterns all over its body during the first to third instar. The first to third instar nymphs of H. chinensis had mottled patterns on the femurs of their forelegs, which is a diagnostic characteristic that no native praying mantis species has. From the fourth instar, 7–10 dorsal spines were observed on the foreleg coxa of H. chinensis, whereas only 3 or 4 spines were observed in H. patellifera. These findings show that H. chinensis and H. patellifera can be distinguished in all nymphal instars.

Lithosiini (Lepidoptera: Erebidae: Arctiinae) is distinctive in having some species that feed on lichens, whereas the majority of moths feed on vascular plants. However, the larval diet of most Lithosiini species is poorly known. This study examines whether Lithosiini species, collected in a tropical rainforest of Borneo (nine species) and a temperate forest of Japan (eight species), feed on lichens as larvae, based on stable isotope analyses. As a result, the δ¹⁵N values for eight of nine Lithosiini species collected from Borneo were notably lower than those of nine co-occurring herbivorous non-Lithosiini species, and were similar to those of sympatric, lichen-feeding termites; however, δ¹³C and δ¹⁵N values of one Lithosiini species (Adites sp.) were significantly higher than those of the other moth species and similar to those of humus-feeding termites and predatory insects occurring at the same site. These results have suggested that the Lithosiini in the Southeast Asian tropical rainforests contain some species that feed on lichens as their larval main diet and at least one species whose larvae feed on humus or animal-derived materials. In contrast, the δ¹³C and δ¹⁵N values of all examined Lithosiini species (eight species) in the temperate forest have suggested that their larvae fed on plants and not on lichens. Our stable isotope ratio analysis presented quantitative evidence suggesting lichen-feeding by Lithosiini moths in a tropical rainforest without observation of feeding behavior during the larval stages.