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Many aphidophagous ladybird beetles lay clusters of eggs and sibling cannibalism occurs at hatching. Larvae that hatch early tend to cannibalize undeveloped eggs and those that hatch late. The cannibalized eggs, especially those that are sterile, represent a maternal investment in the cannibal and are regarded as "trophic" eggs, which increase their chances of surviving. The characteristics of cannibalized eggs, however, are poorly studied. In this study, I determined the sizes of eggs that developing and undeveloped eggs within egg clusters of Harmonia axyridis (Coleoptera: Coccinellidae). Developing eggs were significantly larger (on average 3.45% larger) than the undeveloped sterile ones, which were mainly small. Furthermore, the hatchability of eggs was also significantly associated with their size, inclusive of the maternal effects. These results indicate that the production of relatively small sterile eggs functions as circumstance-dependent maternal investment in improving the survival of the first instar larvae to hatch in each egg cluster.

In central Japan, Harmonia yedoensis is a specialist ladybird that is confined to pine tree habitats, whereas its sibling species Harmonia axyridis is a generalist that feeds on a wide range of aphid species in nature. Interestingly, H. axyridis is not distributed in the Ryukyu Archipelago, southern Japan. We hypothesized that the ecological niche of H. yedoensis should be wider in the Ryukyu Archipelago, where its competitor species in central Japan, H. axyridis, is absent. We undertook fieldwork and a survey of published works to examine habitat utilization by H. yedoensis in the Ryukyu Archipelago. We found that H. yedoensis adults in the Ryukyu Archipelago visited several kinds of deciduous trees, including wild tamarind, Chinese hibiscus, Taiwan cherry and Malayan banyan, as well as pine trees. These observations suggest that habitat generalization has occurred in H. yedoensis in the Ryukyu Archipelago, where it does not compete with H. axyridis.

Various strategies exist to manage agriculture pests with few or without conventional pesticides. Farmers can rely on ecosystem services delivered by agro-biodiversity or use biotechnologies and biological plant protection products (PPP). Integrated Pest Management (IPM) has developed as an approach that combines these tools. The adoption of IPM has been supported by the European Union (EU) in the recent years. In parallel, EU Common Agricultural Policy (CAP) has strengthened its agri-environmental incentives to further protect biodiversity in agricultural landscapes. These evolutions have been presented as the “greening” of the CAP. We argue that this “greening” aims at strengthening agricultural competitiveness while preserving biodiversity. Hence, we suggest that the EU policy is entrenched in a green productivism paradigm, which objective is to produce more with less to achieve green growth within capitalism. Nonetheless, this worldview does not content all European farmers. We explain that those who reject productivism treasure a sufficiency paradigm by refusing the use of biotechnologies and biological PPP to consolidate their autonomy, especially regarding markets. By producing enough, and not more with less, they achieve complementary objectives, notably meeting their consumers’ expectations and perpetuating their productive resources. We based our arguments on discussions with farmers, participation to various meetings between 2013 and 2017 where these issues were debated, and the analyses of the EU policies, scientific studies, as well as the farmer unions’ and the companies’ publications.

Predaceous ladybird beetles are known to consume alternative foods from flowers, especially when prey is scarce. Flower-rich semi-natural habitats in agroecosystems generally host a diversity of natural enemies, including predaceous ladybird beetles, suggesting that the availability of flowers may have a positive role in their fitness traits. In this study, we test whether feeding on flowers of Perilla frutescens (Lamiaceae) increases longevity and fecundity in Harmonia axyridis Pallas (Coleoptera: Coccinellidae). The longevity of H. axyridis females and males fed with five flowers was significantly greater than those fed with one flower and in the control group (no food), although the provision of flowers had no positive effect on the increase of body weight in males and females. The number of eggs and oviposition frequency in H. axyridis fed with flowers plus prey, as well as with prey only, were significantly larger than those fed with only flowers, whereas no significant difference was observed between individuals fed with the mixed diet and those with only prey. However, on the first day of the diet assignment, the number of eggs from individuals with the mixed diet was significantly higher than of those with only prey and those with only flowers. The results show that flowers of P. frutescens, mixed with prey, have a positive effect on H. axyridis survival and early reproduction, suggesting that flowers may play an important role in increasing fitness in H. axyridis. The possibility of P. frutescens sown in fields to support populations of the predator toward conservation biological control is discussed.

This paper presents a method with accuracy to estimate instars for insects which have large number of instars, especially at long growth period. We clarified the colony composition of the wood-feeding cockroach Panesthia angustipennis spadica Shiraki (Blaberidae) in a field, estimating the instars of field-collected individuals through a cluster analysis using field and laboratory data. Overall, 84.8% sampled units contained multiple individuals, and the largest colony consisted of 65 individuals. The colonies were composed of adults and nymphs (43.5%), or nymphs without adults (52.2%). The number of instars in this species was estimated as ca. ten. Furthermore, some colonies contained an adult pair and nymphs at multiple developmental stages, whereas other colonies contained only small nymphs (estimated instars 1–3). These results demonstrate that the social structure of P. angustipennis spadica varies widely, and that colonies containing both adults and nymphs may indicate the origin of subsociality in cockroaches.

In agricultural fields, wildflower strips can be sown to enhance conservation biological control of insect pests. However, issues remain regarding the composition of flower mixtures to effectively attract and support large communities of natural enemies. Trait-based approaches are promising for this purpose. In the present study, conducted in an agricultural field of Belgium in 2014 and 2015, 15 flower mixtures were considered to explore the relation between the abundance of trapped generalist predators (i.e. lacewings [Neuroptera: Chrysopidae], ladybeetles [Coleoptera: Coccinellidae] and hoverflies [Diptera: Syrphidae]) and the community-weighted means of seven flower traits. Through a redundancy analysis, it was found that the presence/absence of flower ultra-violet pattern and the morphology of the corolla (that determines the accessibility of floral resources) were the traits that significantly affected the abundance of the generalist predators in the flower mixtures. The ladybeetles Harmonia axyridis and Propylea quatuordecimpunctata as well as the lacewings Chrysoperla carnea were more abundant in mixtures with a high cover of flowers showing an ultra-violet pattern, while the opposite was observed for the ladybeetle Coccinella septempunctata. As for hoverflies, Episyrphus balteatus and Eupeodes corollae were more abundant in mixtures with a high cover of flowers with open nectar. These results bring new knowledge regarding how a range of natural enemy species reacts to flower cues in diversified plant communities and should help in elaborating flower mixtures that enhance conservation biological control.

The wood-feeding cockroach Panesthia angustipennis spadica Shiraki (Blaberidae) is a gregarious species, and its groups containing both nymphs and adults have often been observed in the field. To clarify the effects of aggregation with a parent and siblings on nymphal development in P. angustipennis spadica, we raised nymphs of this species in the laboratory under the following three experimental categories: (a) aggregate with a female adult; (b) aggregate without a female adult; and (c) solitary. Survival rates did not significantly differ among the three categories. Unexpectedly, our results clearly showed that nymphs raised in aggregates with a female adult were smaller, lighter, and reached a lower instar than those raised without a female adult. These results indicate that the presence of a female adult does not positively affect nymphal development; i.e. there may be no direct parental care in this species as indicated by previous studies. Moreover, solitary nymphs grew faster and larger than nymphs in aggregates, showing that the aggregation with siblings also has no positive effect on nymphal development. Thus, it seems likely that external factors, e.g. predation and environmental conditions, may drive aggregating behavior in P. angustipennis spadica.

We dissected the trunk of a Quercus serrata Murray tree that had suffered from Japanese oak wilt, measured the gallery diameters of ambrosia beetles, and recorded the related insect fauna in the galleries of ambrosia beetles. In total, 545 individuals of nine species were captured from 494 galleries; these belonged to nine species [Cossoninae sp. (Curculionidae), Litargus japonicus Reitter (Mycetophagidae), Platypus calamus Blandford (Platypodidae), Platypus quercivorus (Murayama) (Platypodidae), Ambrosiodmus lewisi (Blandford) (Scolytidae), Ambrosiophilus atratus Eichhoff (Scolytidae), Xyleborus sp. (Scolytidae), Bitoma siccana Pascoe (Zopheridae), and Gempylodes ornamentalis (Reitter) (Zopheridae)]. The diameter of the gallery entrance on the surface of a debarked log may serve as a cue for species estimation of major ambrosia beetles in Q. serrata trees suffering from Japanese oak wilt in this study area. From the relationships between the body width and the gallery diameter, the distribution pattern within the tree, and the taxonomical analogy, a zopherid species, G. ornamentalis, was inferred as a possible predator and/or parasitoid of a causal agent in Japanese oak wilt, P. quercivorus.

We mainly examined the community structure and seasonal population trends of scolytid and platypodid species captured via ethanol-baited traps in a natural cool-temperate forest in Japan. The scolytid species in the tribe Xyleborini represented more than 70 % of individuals captured in ethanol-baited traps, although the platypodid species could be abundant in this study area. These results indicate that the scolytid species in tribe Xyleborini might have higher sensitivity to ethanol-baited traps than others and the ethanol-baited trapping method could target the limited number of scolytid and platypodid species. Therefore, analysis based only on the ethanol-baited trapping method may lead to misunderstanding the community structure of scolytid and platypodid species. The analysis of the seasonal changes in number of scolytid and platypodid species, using a generalized linear model (GLM) showed that the ethanol-baited traps appeared to function more effectively in spring than in other seasons. Hence, the trapping season should be considered when analyzing the data obtained from ethanol-baited trapping census, especially with scolytid and platypodid species.

Geographical variation of elytra color pattern in two sibling ladybird species, Harmonia yedoensis and H. axyridis (Coleoptera: Coccinellidae), was examined. The two species are distributed sympatrically in central Japan; however, only H. yedoensis and H. axyridis occur in the Ryukyu Islands (southern Japan) and Hokkaido island (northern Japan), respectively. The frequency of elytra color patterns was significantly different between the two species in all sympatric locations and our results were inconsistent with the classical theory on Mullerian mimicry. The most dominant pattern of H. axyridis was the least dominant of H. yedoensis in all sympatric populations. Furthermore, the frequency of the non-melanic form (red ground color with or without black spots) increased towards the south in H. yedoensis. This tendency was in contrast to the known geographical cline in H. axyridis in which the melanic form (black ground color with red spots) was gradually displaced with the non-melanic form northwards in the Japanese archipelago. We discuss possible selective factors including predator avoidance, thermal adaptation and reproductive character displacement, all of which might contribute to the maintenance of the color polymorphism in the two Harmonia species.

In predatory ladybirds male embryos in clutches of eggs infected with male-killing bacterial endosymbionts do not hatch and are consumed by female hatchlings. Moreover, it is predicted that infection with male-killing bacteria should be prevalent in a ladybird population if the fitness advantage to female ladybirds due to the resulting reallocation of resources is high. We compared male-killer bacterial prevalence in two sibling species of the ladybird genus Harmonia that use different host ranges. Harmonia yedoensis feeds mostly on the highly elusive pine aphid and its hatchlings can greatly enhance their ability to capture prey and thus their survival by consuming un-hatched eggs in the clutch. In contrast, Harmonia axyridis feeds on a wide range of prey and consumption of un-hatched eggs by the hatchlings does not necessarily increase their foraging success. In the study area where these two species of ladybird occur sympatrically 14 of the 22 females of H. yedoensis (64%) laid clutches of eggs of which approximately only a half hatched and did not produce male offspring, whereas only one of 12 of the females of H. axyridis (8%) exhibited symptoms indicating infection with male-killing bacteria. In the H. yedoensis that exhibited symptoms of being infected with male-killing bacteria, the total allocation of resources to each hatchling, which was provided by laying larger eggs and eating the un-hatched eggs in the clutch, was considerable. These results suggest that the difference in the prevalence of infection with male-killing bacteria in these two species of ladybird may reflect differences in the quality of their prey and their foraging behaviour.

Ambrosia beetles (many Scolytinae and all Platypodinae) are one of the most important insect pests for forestry worldwide, but little is known about the community structure of ambrosia beetles in terms of their vertical variations and resource utilization. We clarified the community structure and seasonal population trends of ambrosia beetles on 11 living and three newly dead Fagus crenata Blume trees using individual tube traps placed up to 10 m high from May to November in 2007 and 2008. We captured seven scolytine species (Ambrosiodmus lewisi (Blandford), Euwallacea validus (Eichhoff), Trypodendron proximum (Niisima), Xyleborinus saxeseni (Ratzeburg), Xyleborus atratus Eichhoff, Xylosandrus brevis (Eichhoff) and Xylosandrus germanus (Blandford)) and three platypodine species (Crossotarsus niponicus Blandford, Platypus hamatus Blandford and Platypus severini Blandford). The ambrosia beetles were suggested to breed at species-specific height ranges, with the equal host resource use per individual among the species. Of the three major species, C. niponicus, P. hamatus and P. severini, two (C. niponicus and P. hamatus) had male-biased sex ratios, which is considered a reproductive strategy to increase maternal fitness. Morphological characteristics of the mandibles may play an important role in the difference of sex roles on reproduction in the three major species.

The range and quality of prey species differ greatly among closely related species of predators. However, the factors responsible for this diversified niche utilization are unclear. This is because the predation and resource competition do not always prevent species coexistence. In this paper, we present evidence in support of reproductive interference as a driver of niche partitioning, focusing on aphidophagous insect. Firstly, we present closely related generalist and specialist species pairs in aphidophagous lacewings to compare the reproductive interference hypothesis with two other hypotheses that have been proposed to explain niche partitioning in lacewings and sympatric speciation through host race formation and sexual selection. Secondly, we present a case study that shows how reproductive interference can drive niche partitioning in sibling ladybird species. Thirdly, we show that many ladybird genera include species inhabiting the same region but having different food and habitat preferences, raising the possibility that reproductive interference might occur in these groups. Finally, we show that intraguild predation cannot always explain the niche partitioning in aphidophagous insects including hoverflies and parasitoids. On the basis of the evidence presented, we urge that future studies investigating predator communities should take account of the role of reproductive interference.

The trade-off hypothesis posits that increased performance on a given resource comes at the cost of decreased performance on other resources, and that this trade-off is a driving force of food specialization in both predators and herbivores. In this study, we examined larval survival and performance in two sibling ladybird species, Harmonia yedoensis Takizawa and Harmonia axyridis Pallas (Coleoptera: Coccinellidae), fed on one of four prey species. Harmonia yedoensis is a specialist predator that preys mostly on pine aphids in the field, whereas H. axyridis is a generalist predator with a broad prey range. We experimentally showed in the laboratory that larval survival and performance were not higher when H. yedoensis was fed on pine aphids, compared with the other prey species. Rather, prey suitability was similar in both ladybird species, and H. yedoensis larvae developed as well or even better on prey species that they never utilize in nature. These results suggest that the host range in H. yedoensis may not be limited by the intrinsic suitability of the aphid species per se. Moreover, as shown by our previous study, the pine aphid is a highly elusive prey that is difficult for small ladybird hatchlings to capture, which means that the cost of utilizing this prey is high. Therefore, we conclude that some factor other than prey suitability is responsible for the observed food specialization in H. yedoensis.

The toxic ectomycorhizal fungi Amanita muscaria (Agaricales: Amanitaceae) was first recorded in New Zealand in 1937, and it is now widespread throughout the country. We collected decaying fruiting bodies of the mushroom in 2005 and 2006 and placed them in enclosed emergence traps to determine use by fungivorous insects. This study clarified that the endemic species Mycetophila fagi, M. filicornis (Diptera: Mycetophilidae) and Zedura curtisi (Diptera: Trichoceridae), as well as exotic Drosophila busckii (Diptera: Drosophilidae), utilised the exotic A. muscaria in various vegetation types in the North and South Islands of New Zealand. A significant difference was observed in the number of fungivorous insects found on the mushrooms between North and South Islands; the endemic M. fagi was dominant in South Island, while Psychodidae sp. dominated North Island. A significant difference was observed in the number of fungivorous insects between the exotic and endemic vegetation inhabited by A. muscaria. Furthermore, the biodiversity of fungivorous insects on A. muscaria within endemic Nothofagus vegetation was more than three times greater than that within the exotic Betula , Pinus, Pseudotsuga and tsuga vegetation. These observations suggest that the greater diversity of fungivorous insects on A. muscaria in natural Nothofagus forests may reflect the higher diversity found in natural forests compared with plantation forests.

In Hymenoptera and Heteroptera, the absence of micropyles is one criterion for categorizing an egg as trophic. Undevel- oped eggs are observed in more than 90% of the egg clusters of the ladybird beetle Harmonia axyridis Pallas. Traditionally, these undeveloped eggs are regarded as "trophic eggs." The surfaces of the eggs of H. axyridis were examined using scanning electron microscopy and the presence of micropyles in the shells of developing and undeveloped eggs determined. Micropyles are circularly distributed around the top of eggs and present in both developing and undeveloped eggs. The number of micropyles in the shells of developing and undeveloped eggs did not differ significantly. Our results indicate that the undeveloped eggs of H. axyridis have micropyles, suggesting that the mechanisms regulating the production of undeveloped eggs in H. axyridis differ from those resulting in the production of trophic eggs by Hymenoptera and Heteroptera.

The sibling species H. yedoensis Takizawa coexists sympatrically and simultaneously with H. axyridis only on pine trees in Japan. To elucidate the mechanisms enabling coexistence of these two sympatric sibling species, a laboratory experiment was per- formed that focused on differences in their maternal investment through eggs and the role of sibling cannibalism. The egg size (vol- ume) of H. yedoensis was 24.91% larger than that of H. axyridis. Cluster size in H. axyridis was significantly larger than that in H. yedoensis; however, the total number of eggs and oviposition cost (by volume) per female in H. yedoensis were not significantly dif- ferent from those in H. axyridis, although total number of clusters tended to be slightly higher in H. yedoensis than in H. axyridis. The percentage of undeveloped eggs per cluster in H. yedoensis was not significantly different from that in H. axyridis, whereas the percentage of developed eggs with delayed hatching per cluster was significantly larger in H. yedoensis than in H. axyridis. Moreo- ver, the cost of sibling cannibalism per hatched larval cluster in H. yedoensis (worth 4.43 sibling eggs) was 3.36 times larger than that in H. axyridis.Therefore, maternal investment through egg and sibling cannibalism in developed eggs with delayed hatching are more intense in H. yedoensis than in H. axyridis, implying a higher larval survival rate through higher ability of prey capturing at the first instar. The results in this study suggest that the higher survival rate and accelerated development in H. yedoensis by the two maternal investments, i.e., a large egg and intense sibling cannibalism of developed eggs with delayed hatching, may play an impor- tant role in sympatric coexistence with the aggressive aphidophagous ladybird beetle H. axyridis.

The genusDioscoreaL. (Dioscoreaceae) is widely distributed throughout Africa and Asia and includes 500 to 650 species (Burkill 1960; Miège and Lyonga 1982), almost all of which are dioecious (Terauchi 1990). Pollination of species in this genus has received little attention because many of the cultivated species are propagated vegetatively from tubers. Insect visitors to flowers have been reported for two species,D. alataL. from India (Abraham and Nair 1990) andD. rotundataPoir. from Nigeria (Pitkin 1973; Segnouet al.1992; Bournier 1994).Dioscorea japonicaThunb. is found throughout Japan, Korea, and China (Ohwi and Kitagawa 1983), but insect visitors to the flowers have not previously been reported. We investigated the insect visitors to flowers ofD. japonicabecause the insect fauna associated with one species of a genus often differs from that associated with other species of the genus and may vary within a single species between different geographic regions (Kobayashiet al.1999).

The ladybird beetle Harmonia axyridis Pallas was investigated under laboratory conditions to clarify the relationship between food abundance or scarcity and ovarian development or oosorption. Four conditions were used: (1) fully fed for 24 h, (2) 24-h starvation, (3) 48-h starvation, and (4) 24-h starvation followed by 24-h re-feeding. Body length and initial body weight were not significantly related to the number of ovarioles per female. Both starvation conditions significantly increased the percentage of oosorptive individuals and ovarioles per female, and significantly decreased the percentage of mature ovarioles per female. Re- feeding for 24 h after a 24-h starvation resulted in a significantly higher percentage of mature ovarioles per female; however, the per- centage of mature ovarioles remained lower than in the fully fed condition. Oosorption mainly occurred during the intermediate developmental stage of the ovarioles. The rates of ovarian development and oosorption in predatory H. axyridis were much faster compared with those in herbivorous ladybird beetles. Body length, initial body weight, and the number of ovarioles were signifi- cantly correlated with the number of eggs laid during the last 24 h of each experimental condition. From an analysis of the weight loss and the number of eggs laid during the last 24 h of each experimental condition, it appears that the realized weight of the eggs may be directly determined by the amount of food digested by the adult. The ovarian development and oosorption were asymmetric in the right and left ovaries. These may be important strategies for oviposition in H. axyridis, because selective provision of maturing ovarioles in the right or left ovary with digested nutrients would favor their development. In addition, the energy loss through oosorption during the intermediate developmental stage of oocytes would be less than the energy loss resulting from the resorption of mature oocytes. Therefore, one role of the ovary in H. axyridis, in addition to egg production, might be as a kind of energy storage system for increasing reproductive success. An immediate start of ovarian development under favorable feeding conditions and rapid oosorption during food scarcities may be an adaptive ovipositional and survival strategy for female adults of H. axyridis in response to heterogeneous and fluctuating resource conditions.

Most central Honshu populations of the ladybird beetle, Coccinella septempunctata L., pass the winter as quiescent adults. However, variations in life cycle within populations have been observed: hibernating and reproductive adults simultaneously coexist in the same habitat in winter. We studied microhabitat use patterns of this beetle in winter on a sunny slope of a southeast-facing riverbank. We found that, even though natural substrates were available, the beetle preferred to use artificial substrates such as metal cans (iron or aluminum), papers, and wooden materials discarded on the slope as oviposition and pupation sites. The artificial substrates were relatively easily warmed by solar radiation and were therefore used as thermal microhabitats by the beetle. Although ambient winter air temperatures of this region were not high enough for the beetles to complete their development, the use of thermal microhabitats enabled them to do so by thermal conduction. Prey aphids were also abundant during the winter. Thermal microhabitat use enables these beetles to complete an additional generation in winter.

I hypothesized that sibling cannibalism is one of maternal investment in that a female controls sibling cannibalism. To test the hypothesis, I conducted a laboratory experiment and field observations to investigate sibling cannibalism in relation to cluster size and cluster site in the ladybird beetle, Harmonia axyridis Pallas. In the laboratory experiment, cluster size significantly affected the number of cannibalized eggs per cluster (R2 = 0.516), while cluster size was significantly affected by the oviposition interval. Furthermore, there was a marginally significant positive relationship between cluster size and the percentage of sibling cannibalism per cluster. In the field, cluster size and the direct distance from a cluster site to an aphid colony (an indicator of intensity of non-sibling cannibalism) significantly affected the number of cannibalized eggs per cluster (R2 = 0.472). Furthermore, there was a significant positive relationship between the direct distance from a cluster to the nearest aphid colony and cluster size. However, there was not a significant relationship between the distance and the percentage of sibling cannibalism. These results may be caused by the weakness of the female's power to control sibling cannibalism. Thus, a female H. axyridis controls cluster size through the intensity of non-sibling cannibalism, which may be one of oviposition strategies in this species.

To elucidate the temporal response of parasitoids to their host density, we investigated the temporal relationship between the density of the leafroller moth, Eudemis gyrotis (Lepidoptera, Tortricidae), and larval and pupal parasitism in the Þeld. E. gyrotis had overlapping-generations, and the density of larvae and pupae of E. gyrotis varied seasonally. Analysis of the temporal relationship between the density of E. gyrotis and the percentage parasitism revealed a tendency toward positive density-dependent attack by the parasitoid Apanteles sp. (ater-group) (Braconidae) on early-stage E. gyrotis larvae, and inverse density-dependent attack by Goniozus japonicus (Bethylidae) in late-stage larvae. However, no temporal density-dependent attack was observed by the pupal parasitoids Brachymeria excarinata (Chalcididae), B. lasus, and Itoplectis alternans spectabilis (Ichneumonidae). These different responses to host density by the parasitoid species were discussed in terms of the mode of parasitism, the host stages attacked, host-searching behavior, and the effect on the host population.