Entomological Science最新文献

The aquatic larvae of the family Hydrochidae (Coleoptera) have been considered ‘mystery larvae’, because ecological knowledge about them is lacking. We discovered that Hydrochidae larvae (Hydrochus japonicus Sharp) are benthic via laboratory rearing. The larvae have a terminal spiracular atrium, but we did not observe them breathing at the water surface. The larvae fed on Naididae worms that were collected from the same habitat.

Numerous delphacid planthopper species are major pests of economically important and widely cultivated crops (i.e. rice, corn, and sugarcane). These insects have the potential to become serious crop pests in areas where they have either naturally migrated or been newly introduced. The white-bellied planthopper, Stenocranus pacificus Kirkaldy, 1907, originally known from tropical South Pacific islands, appeared in tropical and subtropical Asia in the early years of the 21st century. Since then, S. pacificus has become a serious pest of corn in some Southeast Asian countries, although it also feeds on rice, sugarcane, sorghum, and other grasses. Here, we report the presence of S. pacificus in mainland Japan, representing the first record of this species in temperate Asia. Seven male and 17 female adult individuals collected in Kumamoto Prefecture in 2019 and 2020 were identified as S. pacificus based on their morphological characteristics and mitochondrial COI sequences. In addition, molecular phylogenetic analysis showed that S. pacificus formed a distinct clade from other Stenocranus species, indicating uncertainty in its generic assignment. Although crop damage by S. pacificus has not yet been reported from temperate regions, given its wide range of plant hosts and the potential for future range expansions, damaged crops in Asia, including in temperate regions, should be monitored for the presence of this species.

Various insect species lay tiny, thin- and soft-shelled eggs in a connected “egg mass”. Especially in several lepidopteran species, the structure of such clustered eggs is covered with complicated scale-like secretion, which has so far prevented analysis of individual embryos. However, few studies on methods to disperse egg clusters of such insects and to compare different methods have been carried out. To overcome these problems, we developed methods to separate egg masses into individual eggs, using two Tortricidae pests, Homona magnanima Diakonoff and Adoxophyes honmai Yasuda (Lepidoptera: Tortricidae). The eggs were successfully separated from each other using potassium hydroxide and sodium hypochlorite. Although the separated eggs no longer continued their embryogenesis, fixation with heptane–paraformaldehyde, permeabilization with heptane–methanol, and staining with several dyes enabled easy observation of embryogenesis. This protocol is expected to be applicable to other insect taxa and will facilitate further morphological and genetic studies in insects that lay egg masses.

Plant decomposition is an essential component of forest ecosystems. Wood-feeding cockroaches are responsible for the decomposition of rotten logs. However, the ecology of wood-feeding cockroaches is not well understood. To understand how they decompose rotten logs in the gallery inside the logs, it is necessary to observe them in laboratories. Here, I present an observable and cost-effective for rearing these log decomposers using a culture dish and an artificial fungal meal. The culture dish is traditionally used to cultivate fungi or bacteria with the lid on. The artificial fungal meal is a commercial product for stage beetle larvae, which are a kind of log decomposers. These let researchers easy to deal with wood-feeding cockroaches. In the course of keeping over 1,000 individuals of the wood-feeding cockroaches, I have developed effective techniques to rear them under the observable system for several years. I present these techniques along with several tips to keep the wood-feeding cockroaches healthy and observe them using video cameras. These techniques remove many of the limitations for study on the plant decomposers. When researchers use this observable rearing system, we can conduct rearing experiments easily and well understand the ecology of wood-feeding cockroaches and insects associating with them.

The sexually dimorphic dynastine centaurus beetle, genus Augosoma (Coleoptera: Scarabeidae), is endemic to tropical Africa where two species are found (A. centaurus and A. hippocrates). These beetles are consumed by rural populations, cause damage in plantations and are targets of insect collectors and traders. We present information on size differences and analyzed intersexual niche divergence and seasonality of A. centaurus in seven study sites in three West African countries (Ivory Coast, Togo and Nigeria). We recorded 711 light-attracted and/or opportunistically encountered individuals, as well as another 97 beetles in standardized transect surveys. In the latter, we found the adult sex ratio was equal, but was significantly skewed towards females in light-attracted and/or opportunistically encountered individuals. In a sample of 298 adult beetles, males were significantly larger than females, with almost no size overlap between sexes. Beetle activity was highly seasonal with most animals observed in November, active from 19:00 h to 24:00 h. Differences in habitat use were not significant between sexes, with most individuals observed in secondary forest. Males were found higher on vegetation than females and beetles of both sexes were found on Pandanus and raffia palms. Beetles were larger in sites with more vegetation cover, and there was a significant effect of tree species on body size of both sexes. Study area or country had no effect on any of the studied parameters. Our study confirms that transect surveys without light trapping can be an effective tool for understanding large-sized tropical beetles of similar ecological characteristics.

Many species of grasshoppers in subfamilies Oedipodinae, Gomphocerinae and Acridinae make sounds when they escape by flying. We carried out four kinds of experiments with the Chinese grasshopper, Acrida cinerea (Orthoptera: Acrididae: Acridinae), whose males often make sounds while flying, to examine the mechanism of sound production during flight by grasshoppers. First, we recorded high-speed video and audio of the tethered flight of the males and found that they produced sounds when they clapped their hindwings together at the end of the upstroke. Second, we recorded the tethered flights of the males when we prevented them from clapping their hindwings to clarify whether the hindwing clapping produced the sounds, and we found that the obstruction of clapping hindwings prevented sound production by the males. Third, we recorded the free flight of the males and determined whether the sound produced by clapping hindwings was not specific to the tethered condition. The males clapped their hindwings during free flight, and sounds were produced when they clapped their hindwings. Finally, we observed the tethered and free flights of the females because the possibility of crepitation flight by the females existed, and we found that sound was produced by females clapping their hindwings during flight. These results showed that male A. cinerea make sounds during flight by clapping their hindwings, and females also have the ability to make sounds by using the same mechanism. This study provides the first experimental evidence on the mechanism of sound production during flight through observing the behaviors of grasshoppers.

Phenology of insect abundance in less seasonal tropical regions is well recognized. Even in Bornean tropical forests in Malaysia, where there is no distinct dry season, there are insect species that behave as if their environments were highly seasonal. How such seasonal dynamics are shaped and what factors determine the seasonality remains largely unresolved. To elucidate the mechanisms underlying population dynamics in relatively stable tropical environments, we classified monthly samples collected with light traps at Lambir Hills National Park, Malaysia, and generated long-term time-series data for the family Passalidae (Coleoptera: Scarabaeoidea), which spend nearly their entire life cycle within or beneath decayed wood. Analyses of our data (20 species and 768 individuals) revealed that there were clear abundance peaks in April and October at the community level. We analyzed the data together with climate data using a nonlinear time-series analysis called convergent cross mapping. The causal relationship between adult population dynamics of the dominant species (Leptaulax planus) and temperature was detected, which shows that the population dynamics of L. planus are driven by cool temperatures approximately 1 month before emergence. Our study indicates that even in perpetually wet tropical rainforests in Southeast Asia, insect population dynamics respond to climatic factors and show seasonal population dynamics.

The aphid Colophina monstrifica forms woolly colonies with sterile soldiers on the secondary host Clematis uncinata in Taiwan. However, the gall or primary-host generation of C. monstrifica has not been found to date. We successfully induced galls of the species on Zelkova serrata by attaching its eggs to the trees, and also found a few naturally formed galls on another Z. serrata tree. The identity of the aphids was confirmed by examining their mitochondrial DNA sequences. First and second instar nymphs in the galls exhibited attacking behavior toward artificially introduced moth larvae. Observations with a scanning electron microscope revealed that the gall inner surface was densely covered with minute trichomes. This indicates the water repellency of the inner surface, and suggests that young nymphs of C. monstrifica dispose of honeydew globules outside the gall, as known in the congener Colophina clematis.

The effects of ovipositing female body size on the survival of the first and second offspring under self and conspecific superparasitism have not been determined. Here, we report the importance of the body size of ovipositing females for three intervals (0, 1, and 24 h) between first and second ovipositions using a semi-solitary ectoparasitoid, Echthrodelphax fairchildii, and fourth-instar nymphs of its host, the planthopper Laodelphax striatellus. We addressed the case in which the first and second parasitoid eggs were laid on different sides of the same host. The second ovipositing female killed the previous offspring using the sting, but when the oviposition intervals were 0 and 1 h, the elimination was unprofitable because both offspring often emerged under non-probing superparasitism. The survival rate of the second offspring decreased with increasing oviposition intervals under non-probing superparasitism, whereas that of the first offspring was independent of oviposition intervals. Under non-probing superparasitism, the survival rates of the first and second offspring were higher under conspecific superparasitism than under self superparasitism, especially when the first and/or second ovipositing females were small. Large mothers ensured high survival rates of their offspring under non-probing superparasitism, except the survival rate of the second offspring under conspecific superparasitism, which was negatively associated with the first female's size. Thus, the first offspring from small mothers were likely to lose the competition to the second offspring. Under probing superparasitism, the second offspring survival rate was positively associated with the mother's size, suggesting that offspring, not ovipositing females, release agents affecting the mother-size effect.