Entomological Science最新文献

Rove beetles (Staphylinidae) are one of the largest families in Coleoptera. Although the ecological features of rove beetles are important subjects in terms of understanding their diversification processes, laboratory-rearing studies have only been conducted for a few species to date. In this study, we established a continuous rearing method for Anotylus amicus (Bernhauer, 1923) (Staphylinidae: Oxytelinae) using bell cricket food. In addition, its life cycle, behavior and morphological variations were investigated using the rearing technique. The mean duration of egg, first, second and third instars, prepupa and pupa were 4.3, 4.0, 4.0, 7.8, 1.7 and 4.7 days at 24°C, respectively. Adults and larvae used substrate, food and excrement for nesting. Mate guarding by males and associated male–male combat were observed. Head width and body size sexually varied; most males were larger than females, but some were comparable to females. Many individuals possessed undeveloped short hindwings, while some, especially large females, had long ones. As A. amicus can be reared simply, have a fairly short generation period, and exhibit interesting behavioral and morphological characteristics, A. amicus is suitable for clarifying the ecological aspects of rove beetles.

The importance of visual stimuli in a given behavior is often different, even between closely related species. Species of the genus Drosophila have been categorized into three classes according to their reproductive dependency on vision. Class I and II species reproduce in the darkness, whereas class III species never reproduce without vision. Therefore, in class III species, mutants at the white locus that are deprived of normal visual function are not able to be established as homozygous stocks. Drosophila prolongata is a species with a conspicuous body color pattern, suggesting that an increased importance of visual stimuli underlies the evolution of this species. In this study, to examine the behavioral dependency on visual stimuli in D. prolongata, we generated white gene-knockout (w⁻) mutants using the CRISPR/Cas9 system and examined their mating and fighting behaviors in light and dark conditions. The courtship and fighting activities of w⁻ males were extremely reduced regardless of the light condition. Furthermore, wildtype males did not perform any courtship or fighting behaviors in dark conditions. Our results showed that D. prolongata is a class III species that strongly relies on visual stimuli in both behaviors.

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.