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Many ladybird species are known to have an elytral colour polymorphism, which indicates geographical variation. The ladybird beetle Cheilomenes sexmaculata (Fabricius) exhibits elytral colour polymorphism and has expanded its distribution from 33°N to 36°N in Japan over 100 years since 1900. The mitochondrial COI gene haplotypes were integrated into two haplotype groups, with one group existing at higher frequencies in lower latitudes, the other group appearing at higher frequencies in higher latitudes. In addition, the dark morph types of this species increase with latitude, whereas the light types appear at higher relative frequencies in lower latitudes. In the present study, we first determined the morph types of individuals and examined the mitochondrial DNA COI gene. Second, we investigated the relationship between the genetic population structure based on the mitochondrial DNA COI gene and the morph types’ geographical variation. Results indicated that the mtCOI genetic structure was associated with the morph types by latitude; specifically, the haplotype group existing at higher frequencies in lower latitudes tended to be light morph types. In contrast, the haplotype dominant in higher latitudes more frequently exhibited dark morph types, indicating that dark morph types in the higher latitude genetic group may have led the distributional expansion toward higher latitudes since 1900 rather than the lower latitude light morph types.

Inspired by the system of ordinary differential equations in Agusto et al. (2017) that models Zika virus dynamics by taking into account of both sexual and vector-borne transmissions, we furthermore add diffusive terms in order to capture the movement of human hosts and mosquitoes, considering the unique threat of the sexual transmission route of Zika virus. We conduct complete theoretical analysis. In particular, we show that every initial data that is continuous and non-negative admits a unique continuous and non-negative solution for all positive times. Moreover, we derive the basic reproduction number and when it is beneath one, we prove that the disease-free-equilibrium is globally attractive. Finally, when the basic reproduction number is above one, and any of the exposed males or the exposed females or the exposed mosquitoes is not identically zero, we prove the existence of a positive asymptotic lower bound for every component of the solution which in particular implies the uniform persistence of the disease, as well as the existence of at least one positive steady state.

Phenotypic polymorphisms are found in a wide array of taxa, and unravelling the mechanisms that maintain them is of great interest to evolutionary and ecological biologists. Temporal environmental heterogeneity may play a role in the maintenance of polymorphisms but is poorly understood. In the present study, we analysed trends in intergenerational elytral colour morph frequencies in relation to changes in fitness and life history traits (i.e. body size, mortality, fecundity, hatching rate and mate preference) in the ladybird beetle Cheilomenes sexmaculata (Coleoptera: Coccinellidae). A long-term field survey spanning nine years showed that the frequency of dark morphs increases over winter and then decreases in spring. Dark morphs may have an advantage in winter due to their higher tolerance of low temperatures compared with light morphs. Light-morph females were heavier in winter than dark-morph females. They also mated more frequently and had higher hatching rates, potentially causing an increase in light morphs in spring. These results suggest that fluctuations in morph frequencies resulting from the conflicting directions of selection pressures between overwintering and spring generations may help to maintain genetic polymorphism.

Yamazaki, Kazuo (2018): The Picture of Dorian Gray: shell corrosion allows freshwater and brackish-water gastropods to masquerade as empty shells. Journal of Natural History 52 (35-36): 2331-2338, DOI: 10.1080/00222933.2018.1537408, URL: http://dx.doi.org/10.1080/00222933.2018.1537408

The ladybird beetle, Menochilus sexmaculatus (Fabricius), has a remarkable elytral colour polymorphism composed of black and red. In the present study, we investigated the effect of temperature on growth from the first instar larva to the pupal stage, as well as maternal morph types on the phenotypic expression of the elytral colour morph in a polymorphic population from Osaka, Japan. Female individuals of three different elytral colour morphs were collected from a wild population, and hatchlings from each female were divided into three groups, which were reared at three constant temperatures: 20 °C, 25 °C, and 30 °C. The phenotypic frequency of F 1 adults indicated that the elytral morph type was determined by genetic factors, but not by growth temperatures. Namely, type A (almost black morph) was the most abundant in F 1 from type A mothers (Male: 52.6%; Female: 32.3%); and types B (four small-dotted morph) and F (four medium-dotted morph) were the most abundant from type B (Male: 56.7%; Female: 53.3%) and type G (four larger-dotted morph) mothers (Male: 33.3%; Female: 31.3%), respectively. Therefore, the expression of elytral colour polymorphism in the Osaka, Japan population is likely to have a genetic basis contingent on parental morphs, rather than a phenotypic plasticity associated with growth temperatures.

Many insects masquerade as parts of plants, such as bark or leaves, or mimic poisonous organisms in order to defend themselves against predators. However, recent studies indicate that plants may mimic insects and other arthropods to deter herbivores. Here, I report visually similar white structures of plants and arthropods in Japan and suggest they are part of a mimicry complex. Young shoots covered with white trichomes or waxy substances may mimic wax-producing insects, such as woolly aphids, coccids and caterpillars, potentially resulting in reduced herbivory. Since wax-producing insects would reduce plant quality and quantity, be distasteful and attract natural enemies, herbivorous insects and mammals may avoid such white shoots. Furthermore, fungus-infected insects, gregarious braconid cocoons, spider egg sacs and froth made by froghopper nymphs or blasticotomid sawfly larvae are also conspicuously white and impose risks for herbivorous insects. Thus, these white structures may be mimicry models for white shoots and are likely to be part of a defensive mimicry complex. Although this study focuses on defence against herbivores, there are simultaneous physiological roles for white colouration that will not be discussed in depth here.

Differences in the time of occurrence of both sexes of adult ladybirds, which reflect differences in the longevity and reproductive strategies of the sexes, is important from the perspective of applied entomology, including biological control, as well as basic entomology. Nevertheless, there is little field census data on this topic. We investigated the seasonal occurrence of both sexes of Cheilomenes sexmaculata (Fabricius) in Osaka City, central Japan, from 2003 to 2011. Female adults tended to appear earlier than males after hibernation or aestivation. That males never appeared earlier than females during the nine year period of this study indicate that protogyny occurs after hibernation and aestivation in this species.

Plant galls, induced by arthropods and various other organisms have an intimate relationship with host plants, and gall-inducers have limited mobility. In addition to their own photosynthesis, galls are resource sinks rich with nutrients, with neighboring plant organs commonly serving as external photosynthate sources. Galls, if not well defended, may therefore be attractive food sources for herbivores. Galls produced by some aphids, jumping plant lice, thrips, and gall midges in Japan, Palearctic region and in the Middle East visually resemble lepidopteran caterpillars. I propose that such visual resemblance may reduce herbivory of galls and surrounding plant tissues, resulting in an increase in galler survival due to reduced gall damage and in enhanced galler growth due to improved nutrient inflow to the galls, when herbivores avoid colonizing or consuming plant parts that look as if they have been occupied by other herbivores. Potential predators and parasitoids of caterpillars may be attracted to the caterpillar-like galls and then attack real caterpillars and other invertebrate herbivores, which would also be beneficial for both gallers and their hosts.

The alien moth Epiblema sugii (Lepidoptera: Tortricidae) induces stem galls on an invasive alien weed, Ambrosia trifida. During summer, along riverbanks in central Japan, the native insects Protaetia brevitarsis, P. orientalis submarumorea (Coleoptera: Scarabaeidae: Cetoniinae), and Camponotus vitiosus (Hymenoptera: Formicidae) feed on the sap exuded from the galls. The cetoniine beetles are highly aggregated among the galls and make wounds on the galls to facilitate sap exudation. Feeding on gall sap may be beneficial to the beetles due to the efficient intake of water and sugar, and the beetles’ inflicting wounds and feeding on the sap seem to have little effect on the gallers. This is a unique finding, where alien plant–galler interaction provides a feeding site for native insects.

The ladybird beetle, Cheilomenes sexmaculata (Fabricius), has been extending its distribution in and around urban areas at higher latitudes in Japan over the past 100 years. Between 2003 and 2011, we investigated the seasonal occurrence, aphid prey and population dynamics of this species in an urban park in Osaka City, central Japan. We found that C. sexmaculata completes three generations a year in Osaka. Overwintered adults emerge in March or April and produce two (or rarely one) generations by summer. Second-generation adults aestivate and subsequently produce another generation in autumn. This species feeds on five species of aphids that infest planted shrubs and alien weeds throughout the vegetative season. We analyzed the association between accumulated temperature and when overwintered adults first emerged. In addition, we determined the association between their time of emergence, peak abundance and last occurrence, and meteorological conditions. There was no association between the sum of effective temperatures and termination of adult overwintering. There was, however, an association between first occurrence and peak abundance, and climatic conditions, such as warm temperatures or low humidity. This species maintained a stable population in an urban park by becoming quiescent when climatic conditions were unfavourable or prey was scarce. We discussed these findings in relation to urban environmental factors, such as climate, food conditions and vegetation.

The ladybird beetle Cheilomenes sexmaculata (Fabricius) is widely distributed throughout the intermediate latitudinal and equatorial regions. It exhibits elytral colour polymorphism with a geographical cline showing increased prevalence of melanic morphs with increasing latitude. Over the past 100 years, this species has extended its distribution towards higher latitudes in Japan because of climatic warming. In this study, long-term changes in the frequency of different morphs and adult body size of this species during this range extension were analyzed based on a survey of specimens in collections. First, we examined specimens collected from areas that were colonized (34-36°N) during the period of range extension (1949-1989) and when it ceased (1990-2005). Chronologically, both the proportions of melanic morphs increased and body size decreased significantly. Next, specimens were examined from newly colonized regions and the former range of distribution (32-34°N); these specimens were collected during period when range extension had ceased. In newly colonized regions, the frequency of melanic morphs was higher and the body size was smaller than in the former range of distribution. These two findings indicate that the smaller, melanic morphs may have undergone a positive-selection driven range extension to higher latitudes.

Long-term changes in the collection season of Menochilus sexmaculatus (Fabricius) were analysed based on 265 specimens collected from the Kansai district, central Japan, during 1949–2004. Results show that collection records in the summer months, July and August, decreased during this period, and that there were no summer records from 2000 to 2004. Concurrently, the annual mean and summer temperatures tended to increase and summer humidity decreased during this period in the Kansai district. Thus, the activity of M. sexmaculatus would be limited in summer because of the recent climate warming.

Predation has led to the evolution of defensive armor in prey species. The dense and long hairs of caterpillars (i.e., lepidopteran larvae) are generally believed to play an important role as a physical defence against predators. However, few studies have been undertaken to investigate how hairs protect caterpillars from a predator’s weapons. To determine the importance of caterpillar hairs as a defensive armor, we observed adults of Calosoma maximowiczi (Carabidae) attacking 5 caterpillar species with different hairiness under laboratory conditions. Carabids used their mandibles to catch caterpillars and thereafter fed on them. Almost all the larvae of 3 smooth species and a short-haired species were easily caught by carabids during their first attack. However, 53.2% of larvae in a long-haired species Lemyra imparilis (Erebidae: Arctiinae) were able to escape from carabid attacks. Even when Lemyra larvae were finally eaten, carabids required a larger number of attacks to catch Lemyra larvae. Dorsal hairs of Lemyra larvae were much longer than the mandible length of carabid adults for any body size, suggesting that the dorsal hairs can function as a physical barrier against carabid attacks. To test the hypothesis, we cut the dorsal hairs of Lemyra larvae shorter than the carabids’ mandibles. Cutting the dorsal hairs of Lemyra larvae resulted in fewer carabid attacks with higher success rates. Therefore, we conclude that long hairs can protect Lemyra larvae from carabid mandibles. This is the first study to clarify the adaptive significance of caterpillar hair length as a morphological defence.

Anti-herbivory animal mimicry by plants has been paid scant attention, and as a result additional types are expected to be recognized. Lycium chinense plants growing in Japan have dark axils, and many leaf-eating beetles leave faeces on host plants or use their faeces as defence. The dark axils of Lycium chinense mimic poisonous faeces or faeces-covered larvae of the leaf beetle Lema decempunctata, which may result in reduced herbivory by mammalian and insect herbivores. Field work in the very different flora of Israel revealed that the same morphology/colouration exists in various wild plant species, both monocotyledons and dicotyledons. We therefore propose a new type of beetle and beetle faeces defensive plant mimicry, and suggest that this type of putative defensive mimicry against mammalian and insect herbivores is probably a widespread but overlooked phenomenon. Moreover, such mimicry may also attract visually oriented enemies that can attack various invertebrate herbivores that occupy these plants.

We study the reaction–diffusion Ebola PDE model that consists of equations that govern the evolution of susceptible, infected, recovered and deceased human individuals, as well as Ebola virus pathogens in the environment, with diffusive terms in all except the equation of the deceased human individuals. Under the setting of a spatial domain that is bounded, we prove the global well-posedness of the system; in contrast to the previous work on similar models such as cholera, avian influenza, malaria and dengue fever, diffusion coefficients may be different. Moreover, we derive its basic reproduction number, and under the condition that the diffusion coefficients of the susceptible and infected hosts are same, we prove the global stability of the disease-free-equilibrium, and uniform persistence in cases when the basic reproduction number lies beneath and above one, respectively. Again, we do not require that the diffusion coefficients of the recovered hosts be the same as the diffusion coefficients of the susceptible and infected hosts, in contrast to previous work on other models of infectious diseases. Another technical difficulty in our model is that the solution semiflow is not compact due to the lack of diffusion in the equation of the deceased human individuals; we overcome this difficulty using functional analysis techniques concerning Kuratowski measure of non-compactness.

The distributional expansion of the ladybird beetle Cheilomenes sexmaculata (Fabricius) in Japan was analyzed based on literature surveys and observations of 1,312 individual specimens collected from 1918 to 2005. An expansion toward higher latitudes, from Kyushu (33°N) to central Honshu (36°N), was observed between 1910 and the early 1990s. Multiple regression analysis showed that the presence of this beetle was associated with an annual mean temperature but not with the mean minimum temperature in the coldest month, and 95 % occurrence probability of this beetle was obtained in a locality at 15.1 °C annual mean temperature. The northward expansion of this species synchronizes with increasing areas where an annual mean temperature is more than 15 °C. Therefore, climatic warming over the past 100 years is considered as a major factor influencing the northward expansion of this species.

The geographical variation in elytral color polymorphism in Cheilomenes sexmaculata (Fabricius) was analyzed based on data from specimen surveys. In all, 1549 individuals collected from different latitudes throughout Indonesia to Japan were categorized into 20 morph types of elytra. Results show that the morph types have a geographical cline: dark types increased with latitude, although the light types showed higher relative frequency in lower latitudes, which suggests that the geographic variation in elytral color polymorphism in C. sexmaculata is a product of selection by climate. The darker morph types might be advantageously able to make fuller use of insolation at higher latitudes, whereas the lighter morph types were likely to reduce heat stress at lower latitudes. In most areas across Southeast and South Asia, all specimens were of the lightest type, which may imply either: (i) the saturation of genes expressing light morph types, which have less solar absorption, due to tropical climate; or (ii) an enhanced warning function of bright red against predators. On Miyako Island of Japan, a unique frequency of morph types was found compared to the adjacent areas.

Goldenrod stems whose apices nod are shown to have architectural resistance against some herbivorous insects that attack terminal buds. In Japan and other regions, many other plant species including herbs, climbers, shrubs and trees have similar ducking stems during young developing stages. Several herbivorous insects that attack young shoots cause stems to droop, resulting in an appearance similar to ducking stems. Thus, I postulated that ducking stems of many plants may also function to deter some phytophagous insects in addition to preventing photoinhibition, and that insects, especially stem-borers that induce stem drooping, may achieve fitness gains by reducing predation, parasitism and attacks on infested stems by other herbivores. Alternative mechanisms causing stem-ducking and experimental tests of the hypotheses and future directions are discussed.

Red colouration is common in young and old leaves of broadleaf woody species. Assuming that leaf colours are adaptive, we examined, by comparing the colouration in young versus old leaves, the possibility that different selection agents may have operated on spring versus autumn leaf colouration. We observed spring versus autumn colouration in three very different woody floras (Finland, Japan and Israel) in order to allow for a broad ecological and evolutionary spectrum. The null hypothesis was that if the same selective agents operated in spring and autumn, it is expected that when spring leaves are red, they should always be red in autumn, and when spring leaves are green, they should be green or yellow in autumn. We found that green spring leaves are almost exclusively associated with yellow leaf colour at senescence in autumn. Species with red autumn leaves almost always have at least some red colouration in their spring leaves. However, about half of the species with red spring leaves have yellow autumn leaves. Brown autumn leaves were not common in the species we studied. As about half of the species with red spring leaves have yellow autumn leaves but not vice versa , we conclude that there are many cases in which the selecting agents for spring versus autumn leaf colour were not the same.

Plants employ various defensive tactics against herbivores but are rarely considered to use rapid movements to resist predation. However, the aboveground parts of plants are often forcefully moved by wind and rain. This passive movement has been overlooked as an anti-herbivore trait. The leaves of many plant species, such as aspens, Indian sacred fig, bamboos, and palms, tremble even in a slight breeze. Leaves that are easily moved by gentle winds can sometimes resist strong winds and may have other benefits as well. In the present study, it is proposed that the movement of such plant leaves physically deters arthropod herbivory and pathogen infection by repelling colonization and oviposition by herbivorous insects. This leads to herbivores and pathogens being dislodged from the plants, and the ensuing death of the herbivores on the ground or at least their recolonization to other plants, as well as the interruption of feeding, intraspecific communication and the mating behaviour of herbivores, thus lowering their performance on the plant or increasing enemy attack of the herbivores. In addition, passive leaf movements may undermine herbivore camouflage and expose them to predation, and may also allow plant volatiles to diffuse efficiently to repel herbivores and attract natural enemies. Thus, the mechanistic properties of these leaves may have anti-herbivore effects in the wind and rain. This hypothesis can also be applied to aquatic plants that tremble in gentle water currents. In addition, genetic manipulation of the tendency for leaf movement may be beneficial for the management of pest insects and pathogens with reduced pesticides in forestry and agriculture. © 2011 The Linnean Society of London, Biological Journal of the Linnean Society, 2011, 104, 738–747.

Seasonal relationships among stranded wrack quantity, seaweed fly abundances, and parasitism at the pupal stage were studied along three sandy beaches in central Japan. The seasonal occurrence patterns of puparia of seaweed flies Coelopa frigida and Fucellia spp. generally corresponded to seaweed deposition, which peaked in May–July and October–December. Parasitoids use fly puparia in these seasons. However, the occurrence of seaweed flies and their parasitoids varied among the three sandy beaches and did not correspond to the wrack amounts. These findings suggest that populations of seaweed flies and their parasitoids are seasonally, but not spatially, regulated by bottom-up processes. The parasitoid assemblage of fly puparia was composed of two Aleochara (Coleoptera: Staphylinidae), two Trichopria (Hymenoptera: Diapriidae), and five pteromalid species (Hymenoptera), but the rate of parasitism was less than 20% and might have had little effect on fly populations.

Leaf-mining insects produce conspicuous and distinct leaf mines on various types of plant leaves. The diversity of leaf-mine morphology has typically been explained by several factors, such as selective feeding on plant tissues, improvement of microclimate, faecal disposal, reduction in the efficiency of parasitoid search behaviour and leafminer phylogeny. Although these factors are certainly associated with mining patterns, masking the mines, rather than making them conspicuous, appears to be more advantageous for deterring parasitoids and predators of leafminers. However, here, I propose that prominent leaf mines may serve to signal or cue herbivores to avoid feeding on the mined leaves. Because most leafminers are sessile and complete their development within a single leaf, herbivory of mined leaves is detrimental to leafminer survival. Other herbivores appear to avoid consuming mined leaves for a variety of reasons: leaf mines mimic leaf variegation or mottling; mined leaves induce chemical and physical defences against herbivores; and leaf mines mimic fungal infection, animal excrement, and necrosed plant tissues. Hence, natural selection may have favoured leafminers that produce conspicuous mines because of the increased survival and fecundity of thereby reducing herbivory on mined leaves.

The prevalence of obligate parasitic fungi may depend partly on the environmental conditions prevailing in the habitats of their hosts. Ectoparasitic fungi of the order Laboulbeniales (Ascomycetes) infect arthropods and form thalli on the host's body surface. Although several studies report the incidence of infection of certain host species by these fungi, quantitative data on laboulbenialean fungus-host arthropod interactions at the host assemblage level are rarely reported. To clarify the effects of host habitats on infection by ectoparasitic fungi, the incidence of infection by fungi of the genus Laboulbenia (Laboulbeniales) of overwintering carabid beetles (Coleoptera: Carabidae) in three habitats, a riverside (reeds and vines), a secondary forest and farmland (rice and vegetable fields), were compared in central Japan. Of the 531 adults of 53 carabid species (nine subfamilies) collected in the three habitats, a Laboulbenia infection of one, five and one species of the carabid subfamilies Pterostichinae, Harpalinae and Callistinae, respectively, was detected. Three species of fungus were identified: L. coneglanensis, L. pseudomasei and L. fasciculate. The incidence of infection by Laboulbenia was higher in the riverside habitat (8.97% of individuals; 14/156) than in the forest (0.93%; 2/214) and farmland (0%; 0/161) habitats. Furthermore, the incidence of infection by Laboulbenia in the riverside habitat ranged from 0 to 33.3% and differed significantly in the ten microhabitats (riverbank, edge of track, tall reeds, kudzu vines, slope of a hollow, rotten wood, vine reeds, under stones, the shoulder of a terrace and marshy ground) where the carabid beetles overwintered. These results suggest that host habitats and microhabitats are closely associated with successful infection by laboulbenialean fungi.

Toxicum funginum Lewis, 1894 (Coleoptera: Tenebrionidae) is a medium-sized, horned species that lives in Japan and Taiwan and feeds on bracket fungi. Intraspecific behavioral interactions among adults were examined in the laboratory. Males engaged in combat with other males using paired horns located between their compound eyes. The contact surfaces of the horns bore curled brown hair, possibly to absorb physical impact. Larger males with longer horns won more frequently than smaller individuals with shorter horns. Smaller males rarely engaged in combat. Females pushed away approaching males violently with their heads.

Plant galls are induced by physicochemical interactions between plants and gall-inducing organisms, such as insects, mites, nematodes, fungi, bacteria and viruses. Organisms that are unable to create galls on plants, but feed on gall tissues induced by other species, are referred to as gall-attackers (gall-feeders) and include various insect orders (Thysanoptera, Hemiptera, Lepidoptera, Coleoptera, Diptera, and Hymenoptera). Gall-attacking weevils (Coleoptera) and moths (Lepidoptera) may have acquired their gall-feeding habits independently (i.e. cecidophages), whereas other gall-attacking insects, such as inquiline gall wasps (Hymenoptera) and gall midges (Diptera) may have evolved these habits from gall-inducing ancestors (i.e., inquilines). Most species of gall-attacking weevils feed only on galls (obligate cecidophages), while most gall-attacking moths feed on galls and also on ungalled or normal plant tissues (facultative cecidophages). Weevils may have acquired their gall-attacking habits independently from other types of feeding habits, such as leaf mining, seed-feeding, and bud-feeding, while moths may have acquired them from leaf-chewing and wood-boring. Studies on the effects of gall-attacking weevils on gall-inducing arthropods report a higher proportion of lethal effects than studies on effects from gall-attacking moths. Weevil larvae rarely move around food resources because they have no legs, while moth larvae can actively move among food resources using their prolegs. This difference in mobility between weevils and moth larva may be related to their differential gall-attacking behaviors and effects on gall-inducers. Cecidophages provide a model system for investigating the evolution of feeding habits and the ecology of species interactions.

The bacterium Pantoea agglomerans pv. millettiae (=Erwinia herbicola pv. millettiae) induces galls on the trunks and twigs of Wisteria floribunda (Fabaceae) in central Japan. We sampled bacterium galls from wisteria at six sites and report a diverse arthropod community, composed of 48 species, representing 33 families and 11 orders, associated with the galls. Dominant arthropods were the larvae of Matsumuraeses falcana (Lepidoptera: Tortricidae) and Synanthedon tenuis (Lepidoptera: Sesiidae) as facultative cecidophages, and Eudigraphis takakuwai takakuwai (Diplopoda: Polyxenidae) as a scavenger. The number of species, abundance of each feeding guild, and overall arthropod abundance were positively correlated with gall diameter.

Our aim was to clarify the factors providing selective pressures on the choice of oviposition sites in phytophagous insects. To this end, we examined the spatial distribution of eggs of the sawfly leaf miner, Profenusa japonica. The study was conducted over five consecutive years on three subpopulations found in riverbeds in central Japan. Profenusa japonica lays eggs on leaflets of Rosa multiflora, and its larvae mine a single leaflet for the entire larval stage. The egg distribution among leaflets was uniform (regular) at all sites examined in each year. The distribution within leaflets was also uniform, and it appeared that females avoided ovipositing on areas of the leaf that already contained eggs. Few parasitoids were found in eggs or larval stages, despite intensive examination. Larval mortality increased, mainly as a result of exploitative competition, when there were two or three larvae per leaflet. Starvation caused by resource competition for leaflet tissues was an important mortality factor. Therefore, we suggest that P. japonica females avoided ovipositing on areas of the leaflet that already contained eggs to prevent exploitative competition among larvae sharing the same leaflet. © 2007 The Linnean Society of London, Biological Journal of the Linnean Society, 2007, 92, 641–650.

The slug caterpillar Parasa lepida (Lepidoptera: Limacodidae) is an introduced pest to urban trees in western Japan. The spatial distribution pattern of P. lepida cocoons was examined on cherry trees along an urban coastal avenue with reference to the effects of distance from the sea, dieback of trees, and avian predation. Stepwise multiple regression analysis revealed that cocoon density increased and tree dieback decreased with distance from the sea. These results suggest that salt spray from the sea and the resulting plant stress may negatively affect the moth. Avian predation rate increased with cocoon density per tree, suggesting density-dependent predation. Also, the predation rate was higher on cocoons between 0.5 and 1.5 m above ground, where the twigs were cleared and prop wood was fixed. These spatial distribution patterns are discussed with regard to pest control.

Gall-forming insects usually have very restricted host ranges, but plant traits affecting patterns of host use have rarely been examined. The sawfly Phyllocolpa sp. (Hymenoptera: Tenthredinidae) forms leaf-roll galls on three of seven Salix (Salicaceae) species that occur together on riverbanks in central Japan. We have attempted to explain this host-use pattern by invoking three plant traits: synchrony of leaf flush with the oviposition period of the sawfly, intrinsic leaf quality as a potential larval food, and leaf morphology. Two Salix species frequently used by the sawfly, Salix eriocarpa and Salix pierotii, had similar leaf traits suitable for larval survival. The third species, Salix serissaefolia, was used relatively less often and the sawfly frequently stopped laying eggs on the plant during oviposition, suggesting ovipositional selection. S. serissaefolia had the smallest leaves, and survival of sawfly larvae was lower on S. serissaefolia than on S. eriocarpa and S. pierotii, because of gall destruction, by other herbivorous insects, and leaf-size restrictions. Among the four unused species, Salix chaenomeloides had a late leaf-flush phenology, Salix gracilistyla had inferior leaf quality, and Salix gilgiana had linear leaves; these seemed to be critical factors for non-use. Salix subfragilis was also unused, but the reason for this could not be explained by the three leaf traits studied.

To elucidate the specific associations of insects with glandular plants, the relationship between a plant bug and a wild azalea was examined. The plant bug Orthotylus gotoi Yasunaga (Hemiptera: Miridae) was found only on shrubs of Rhododendron macrosepalum Maxim. (Ericaceae) in Kyoto, central Japan. R. macrosepalum has leaves, stems, and sepals with dense stalked glands that trap and kill many arthropods. However, nymphs and adults of O. gotoi are able to move freely on R. macrosepalum. O. gotoi frequently fed on carcasses of various arthropods trapped on R. macrosepalum, whereas it rarely fed upon plant tissues. In laboratory experiments, O. gotoi nymphs mainly fed on the carcasses of insects, which resulted in enhanced rates of growth and metamorphosis, and adult O. gotoi lived longer when they were provided with insect carcasses. These observations and experiments suggest that O. gotoi is a scavenger. Therefore, if O. gotoi mainly feeds on carcasses of arthropods, this may result in a specific dependence on the glandular plant. © 2006 The Linnean Society of London, Biological Journal of the Linnean Society, 2006, 88, 593–602.

Mordellid galls were collected from stems of Japanese mugwort, Artemisia indica var. maximowiczii (Nakai) H. Hara, in early spring at three riverbeds in the Kinki district, central Japan, and reared in the laboratory. Adults of two mordellids, Mordellistena brevilineata Nomura (96.2% of the total number of individuals) and M. fuscosuturalis Nomura (3.8%), emerged from the galls. The galls were simple fusiform swellings in the stems. We could not distinguish the 2 species by gall morphology. Mortality of the immatures mostly could not be determined, but parasitoids (Eupelmus sp., Entedon sp., and braconids, etc.) accounted for about 25% of the total mortality observed. Survival of immatures tended to be higher and the concomitant parasitism lower in thicker rather than thinner galls, and the galls became thick when they were formed in larger diameter stems. Oviposition and larval establishment in thick stems appeared to be advantageous for the completion of development and avoidance of parasitoid attack.

The plant-pathogenic fungus Claviceps paspali infects florets of the dallisgrass Paspalum dilatatum and induces the plant to produce honeydew (containing massive amounts of conidia), which in turn attracts insects for dispersal of the fungal spores. In Japan, the association between C. paspali and its host plant is common, although both P. dilatatum and C. paspali are introduced species. To determine the dispersal agents of the introduced C. paspali, we examined which insects sapped the P. dilatatum honeydew produced by C. paspali. The study was conducted from September to October 2003 in central Japan. Adults of 48 moth species and two lacewing species visited infected spikelets of P. dilatatum and sapped the honeydew at night. The dominant moths, which carried C. paspali conidia on their proboscises, migrate long distances every year. Therefore, migratory moths may transmit C. paspali spores from diseased to healthy host plants and may have spread C. paspali to other areas in Japan where C. paspali did not previously exist.

Seven species of parasitoids and two species of moths emerged from bud galls induced by two species of gall midges (Asteralobiasoyogo (Kikuti) and A. sasakii (Monzen)) (Diptera: Cecidomyiidae) on four species of trees of the genus Ilex (I. pedunculosa Miq., I. crenata Thunb., I. chinensis Sims, and I. integra Thunb.) (Aquifoliaceae). Larvae of the moth Rhopobota ustomaculana (Curtis) (Lepidoptera: Tortricidae) bored into bud galls induced by A. soyogo and A. sasakii on I. pedunculosa and I. crenata, respectively. Rhopobota ustomaculana larvae fed on leaves as well as gall tissues of I. pedunculosa, suggesting that R. ustomaculana is a facultative cecidophage. To clarify consequences of gall tissues as a food resource for cecidophagous moths, we compared the chemical properties of galls with those of normal plant tissues (leaves) of I. pedunculosa. Bud galls of I. pedunculosa had higher water content and lower nitrogen, carbon, and polyphenol (a chemical associated with plant insect defenses) contents than leaves. Therefore, bud galls may be a richer food resource for R. ustomaculana larvae because of the higher water content and lower carbon and polyphenol contents, although they are a poorer resource in terms of nitrogen content.

The feeding ecology of Scarites aterrimus Morawitz (Coleoptera: Carabidae), an endangered shore-inhabiting species, was studied by field observations and laboratory experiments. S. aterrimus adults fed on a dead Anisolabis maritima (Bonelli) earwig and dead Armadillidium vulgare (Latreille) pill bug on a beach at night in central Japan. In the laboratory, the adults frequently fed on the carcasses of an earwig, the maggots of the fly species Phaenicia sericata (Meigen), the sandhopper Platorchestia joi Stock & Biernbaum and the pill bug A. vulgare. Predatory behavior was restricted to live fly larvae and pill bugs, occasionally live earwigs and sandhoppers. Similar results were obtained for S. aterrimus larvae. S. sterrimus seems to be a scavenger of various invertebrates and also a predator of slow-moving, less-defended invertebrates.

1. Most lepidopteran larvae use all of their legs (thoracic legs and abdominal prolegs) when walking on solid substrates. When caterpillars involuntarily or intentionally drop from the tree canopy, they can regain their original position by climbing silk lifelines spun out from the head spinnerets. However, the taxonomic distribution of this climbing behaviour in the Lepidoptera is unknown. 2. Here, lifeline-climbing behaviour is reported in 13 lepidopteran species belonging to different taxa (five superfamilies and six families: Zygaenidae, Drepanidae, Geometridae, Lymantriidae, Noctuidae, and Nymphalidae). Caterpillars usually used only the three pairs of thoracic legs to climb lifelines, although they use different methods to walk on solid substrates, according to their taxonomic grouping and number of prolegs. 3. Results suggest that lifeline-climbing behaviour using only the thoracic legs is common among various lepidopteran taxa. The majority of species (12 of 13) climbed lifelines by alternating movement of the left and right set of thoracic legs, aided by side-to-side body movements. Only one of the 13 species, the geometrid Naxa seriaria (Motschulsky), climbed lifelines by drawing them down with its thoracic legs, aided by abdominal looping movements. While side-to-side movement of the abdomen was previously reported in lifeline climbing, this is the first report of the use of looping movements.

We observed epizootics and behavioral alteration in the arctiid caterpillar Chionarctia nivea after infection by an entomopathogenic fungus, Entomophaga aulicae, in April at a riverbank in Kyoto Prefecture, central Japan. The density of arctiid cadavers infected with E. aulicae was 1.31 individuals/m2. The critically ill caterpillars crawled up the dead stems of grasses and herbs such as the common reed Phragmites communis and the Japanese mugwort Artemisia indica var. maximowiczii to die at and near the highest parts of the stems, while the healthy larvae usually wandered on the ground and fed on the leaves of small herbs. This behavioral difference could be caused by infection with E. aulicae to enhance dispersal of conidia by active discharge in Entomophthorales with the aid of wind and rainfall.

Herbivory in the syconia of six Ficus (Moraceae) species (F. superba, F. varieagata, F. virgata, F. irisana, F. bengutensis and F. septica) was examined in March 2002 on Iriomote Island, south-western Japan. Larvae of two lepidopteran species, Pachybotys spissalis (Guenee) (Pyralidae: Pyraustinae) and Stathmopoda sp. (Stathmopodidae) were observed to bore into the Ficus syconia. The attack rate by the moths varied from 0 to 38.5% across Ficus trees. The interiors of the syconia were heavily grazed by the moth larvae. Because figs (syconia) can be regarded as galls and seeds, according to sex and developmental stage, the moth larvae could be considered as gall or seed herbivores, and predators of fig wasps. Moth attack in the Ficus syconia could cause the destruction of fig wasp populations, as fig wasps develop in the syconia.

Gall midge larvae are associated with specific fungal symbionts in ambrosia galls. We found that the weevil Wagnerinus costatus (Hustache) (Coleoptera: Curculionidae: Ceutorhynchinae) frequently attacked ambrosia galls formed by the midge Asphondylia diervillae Felt (Diptera: Cecidomyiidae: Asphondyliini) on the buds of Weigela hortensis (Sieb. et Zucc.) (Caprifoliaceae) in three locations in central Japan. From late April to early May, female weevils laid single eggs in fully developed ambrosia galls, and upon hatching weevil larvae bored into these galls. The rate of parasitism by weevils was consistently high, from 90.2 to 94.5% in each gall midge population. Weevil larvae fed on the hyphae of fungal symbionts as well as on gall tissue. In most cases, parasitism by weevils did not influence the survivorship of A. diervillae or its parasitoids, because oviposition and feeding by the weevil occurred when gall midges had already developed into mature larvae or pupae within hard chambers surrounde...

The host plant, oviposition behavior and larval ecology of Profenusa japonica Togashi are reported for the first time. Adults of P. japonica mated and oviposited on a polyantha rose, Rosa multiflora (Rosaceae), in April. Each female adult laid an egg on the edge of a leaflet. Hatched larvae consumed the parenchymatous layer of leaflets and in so doing created a mine. The larval stage comprised five instars. On average, 70.6% of the total area of a leaflet was consumed by one larva. Female adults of P. japonica laid eggs singly, probably to avoid larval competition for food.

Few spittlebug species are gall formers, but the Homoptera as a whole contain many gall-forming species in many families. Nymphs of a spittlebug, Aphelaenus nigripectus (Aphrophoridae, Auchenorrhyncha, Homoptera), were observed to induce leaf-roll galls on cherry trees (Prunus speciosa, P. × yedoensis and P. pendula cv. pendula (Rosaceae)) in late April in Kyoto, Japan. Aphelaenus nigripectus nymphs aggregated on the ventral surface of the young leaves, fed on the ventral (abaxial) midvein, and excreted masses of froth in the rolled leaves. In a field experiment, it was discovered that feeding of A. nigripectus nymphs can induce rolling of the cherry leaves, and that the rolled leaves may provide protection from desiccation to A. nigripectus nymphs. This is the first record of gall-forming habits in Japanese spittlebugs.

To clarify assemblage patterns of overwintering ground beetles (Coleoptera: Carabidae) and other insect predators in farmland habitats for the purpose of proper land management to enhance beneficial predators, we collected carabid and other insect predators at eight plots including arable and fallow rice and vegetable fields and a bank of an adjacent irrigation pond in central Japan. In total, 159 adults and 268 larvae of 33 carabid species, and 178 individuals of at least 17 species of other insect predators were collected by the quadrat sampling method. In rice fields, both the number of species and no. of individuals of overwintering carabid beetles increased as the soil became dry and vegetational succession proceeded, whereas in fallow vegetable fields carabids decreased according to succession. Similar trends were confirmed in other insect predators. Variations of carabid species richness and abundances among the plots might be attributed to soil water content, vegetation and prey availability. In early-successional fallow vegetable fields, the larvae of the carabid genus Harpalus overwintered with high density; this appeared to be because the fingergrass Digitaria ciliaris (Poaceae), whose seeds were a potential food for Harpalus, were densely vegetated there. In a dry fallow rice field and early-successional vegetable fields, beneficial predators such as Dolichus halensis (Coleoptera: Carabidae), Agrypnus binodulus (Coleoptera: Elateridae), and soldier beetle (Coleoptera: Cantharidae) larvae hibernated with high densities. For proper farmland management to augment insect predators, it is desirable to maintain fallow rice and vegetable fields as relatively dry habitats and at early successional stages. Ploughing fallow fields in winter may reduce overwintering predacious insect larvae.

Plants defend themselves using various physical structures, including spines and thorns. However, some herbivorous insects can make use of defensive structures as food sources. A tortricid moth larva in the genus Cydia bores into thorns of the endangered Japanese honey locust Gleditsia japonica. The larva may escape predation by using the thorns as protection. A survey of sharp plant structures was proposed.

Some spiders are well-known to mimic flowers or other plant surfaces in order to be cryptic to both their prey and their predators. We propose that dense, thread-like white trichomes of some plants from Estonia, Greece, Israel and Japan visually mimic spider webs, lepidopteran and spider-mite web nests and plant-pathogenic fungi, and that it may result in reduced herbivory, since various herbivores avoid spider- or other arthropod webs to circumvent predation or toxic attacks, or refrain from colonizing plants that have already been occupied by other herbivores and pathogens. Spiders and other web-forming arthropods are also the prey of certain vertebrate predators and wasps, and therefore such predators may be attracted to these web-like plant structures and prey on the invertebrate herbivores occupying them. We do not dismiss the possibility that these web-like structures may also have other defensive or physiological functions or that they are not classic mimics but rather exploit the herbivore׳s perceptual state concerning the avoidance of potentially risky objects.

An exotic leaf beetle, Ophraella communa, originating from the Nearctic region, is a multivoltine oligophagous herbivore and was discovered in Japan in 1996. The host-use of the leaf beetle in the field with adult feeding choice and larval performance on some asteraceous plants in the laboratory were surveyed. O. communa showed a hierarchy of food-plant use: The leaf beetle first used Ambrosia artemisiifolia, on which adults preferred to feed and larvae developed well, and its population increased markedly until defoliating this food-plant. Then, the leaf beetle migrated to Am. trifida and Xanthium spp. In the laboratory, Am. trifida was not as preferred by adults as Am. artemisiifolia, although larval performance on Am. trifida was superior. Xanthium was inadequate both in terms of adult feeding choice and larval performance. Neither eggs nor larvae were found on the plant species on which no larvae completed their growth in the laboratory. These findings suggest that the exotic beetle has great mobility and host-discriminating ability. The finding, that Am. trifida was less used than Am. artemisiifolia despite Am. trifida being suitable for larvae, may be attributable to the fact that adutls tend to oviposit on Am. trifida subsequently to feeding.