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Previous studies have shown that the food plant species consumed by herbivorous insects affect their parasitism by parasitoid wasps or flies, but this phenomenon has only been observed in a limited number of systems. Here, we investigate how feeding on different plant species affects the survival of the rice armywormMythimna separata(Walker) (Lepidoptera: Noctuidae) and its successful parasitism by the larval endoparasitoidCotesia kariyai(Watanabe) (Hymenoptera: Braconidae). Survival rate and pupal weight of unparasitisedM.separatafed with daikonRaphanus sativusL. var.longipinnatuswas lower than with maizeZea maysL. In addition, caterpillars fed with daikon were less susceptible to parasitism byC.kariyaithan those fed with maize, and parasitisedM.separatalarvae fed with daikon had higher survival rates than those fed with maize. These results indicate that while daikon is not an optimal food for unparasitised caterpillars, it may protect the larvae from death byC.kariyaiparasitism. [ABSTRACT FROM PUBLISHER]

Asexual reproduction, including parthenogenesis in which embryos develop within a female without fertilization, is assumed to confer advantages over sexual reproduction, which includes a “cost of males.” Sexual reproduction largely predominates in animals, however, indicating that this cost is outweighed by the genetic and/or ecological benefits of sexuality, including the acquisition of advantageous mutations occurring in different individuals and the elimination of deleterious mutations. But the evolution of sexual reproduction remains unclear, because we have limited examples that demonstrate the relative success of sexual lineages in the face of competition from asexual lineages in the same environment. Here we investigated a sympatric occurrence of sexual and asexual reproduction in the pineapple mealybug, Dysmicoccus brevipes. This pest invaded southwestern Japan, including Okinawa and Ishigaki Islands, in the 1930s in association with imported pineapple plants. Our recent censuses demonstrated that on Okinawa sexually reproducing individuals can coexist with and even dominate asexual individuals in the presence of habitat and resource competition, which is considered to be severe for this nearly immobile insect. Molecular phylogeny based on partial DNA sequences in the mitochondrial and nuclear genomes, as well as the endosymbiotic bacterial genome, revealed that the asexual lineage diverged from a common sexual ancestor in the relatively recent past. In contrast, only the asexual lineage exhibiting obligate apomictic thelytoky was discovered on Ishigaki. Co-existence of the two lineages cannot be explained by the results of laboratory experiments, which showed that the intrinsic rate of increase in the sexual lineage was not obviously superior to that of the asexual lineage. Differences in biotic and/or abiotic selective forces operating on the two islands might be the cause of this discrepancy. This biological system offers a unique opportunity to assess the relative success of sexual versus asexual lineages with an unusual morphology and life cycle. [ABSTRACT FROM AUTHOR]

Reproductive biology including mating, adult longevity, fecundity and development of the tachinid fly Zenillia dolosa was investigated for optimizing rearing procedures using Mythimna separata as a host in the laboratory. Females lay microtype eggs containing a first instar larva on food plants of the host and then the eggs must be ingested by the host for parasitization. Mating success was 58.5% with mating duration of 80.7 min. Mating was most successful when day 0-1 females were kept with day 2-4 male flies. Female body size was positively correlated with its fecundity but not with longevity. However, females that survived longer produced more eggs during their lifetime. Parasitoids successfully developed in 4th to 6th instar host larvae. Host instars at the time of parasitoid egg ingestion significantly influenced development time of the immature parasitoid, but did not affect body size of the emerging parasitoid. We suggest that pairing newly emerged females with day 2-4 males should result in higher mating success and using the last instar hosts for parasitization should minimize development time of the parasitoid for rearing. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Some parasitoid flies exploit odors derived from plants as olfactory cues for locating the food plants of host insects, but the role of visual cues associated with plants remains largely unknown. The generalist tachinid Exorista japonica Townsend (Diptera: Tachinidae) is attracted to odors derived from maize plants [ Zea mays L. (Poaceae)] infested by the larvae of Mythimna separata (Walker) (Lepidoptera: Noctuidae). In this study, we examined the effects of visual parameters on the olfactory attraction of female flies to host-infested plants. A paper plant model of one of four colors (blue, green, yellow, or red) was placed in front of a host-infested plant, which was hidden behind a mesh screen in a wind tunnel. The landing rate of females was significantly higher on the green plant model than on the other three models. When an achromatic plant model of one of four gray scales (white, light gray, dark gray, or black) was tested, the response rate of females was significantly higher towards the white model and decreased as the brightness of models decreased. Few female flies responded to the green plant model without odors of the host-infested plants. When the four color plant models were placed together in a cage filled with odors of host-infested plants, females remained significantly longer on the green model than on the other three models. These results showed that E. japonica females preferred the color green when odors of the host-infested plants were present and suggest that E. japonica uses visual as well as olfactory cues to locate the host habitat. [ABSTRACT FROM AUTHOR]

The coconut hispine beetle Brontispa longissima ( Gestro) supposedly originated in Indonesia and Papua New Guinea. It is a serious invasive pest of the coconut palm Cocos nucifera L. in Southeast and East Asia. In Japan, it has established itself using Satakentia liukiuensis ( Hatushima) H. E. Moore as a main host on Ishigaki and Iriomote Islands where C. nucifera is rare. To assess the probability of further establishment of B. longissima in novel habitats where C. nucifera and S. liukiuensis are not available, we examined the suitability of four common palm species in Japan for oviposition and immature development of B. longissima: Chrysalidocarpus lutescens ( Bory) H. Wendl., Phoenix roebelenii O' Brien, S. liukiuensis and Washingtonia filifera ( Linden ex André) H. Wendl. When seedlings of the four palm species were placed in pots in an experimental field on Ishigaki Island, all four species were inhabited and infested by wild B. longissima adults. Oviposition and immature development were observed on P. roebelenii and S. liukiuensis but not on C. lutescens and W. filifera. When field-collected adults were released into mesh bags enclosing the potted seedlings, they oviposited on all four species. The eggs developed into adults on P. roebelenii, S. liukiuensis and W. filifera. On C. lutescens, however, hatched larvae died during the first or second instar. [ABSTRACT FROM AUTHOR]

To clarify the reproductive properties of the coconut pahn pest, Brontispa longissima (Gestro) (Coleoptera: Chrysomelidae), we investigated in the laboratory the diel periodicity in copulation, effect of adult age after emergence on copulation and ovarian development, reproductive development in relation to female age, and the possibility of multiple mating. The beetles used in this study were reared in the laboratory and were fed an alternative food plant, narrowleaf cattail, Typha domingensis Pers. (Typhaceae). Copulation occurred throughout the 24-h cycle but mostly occurred in the photophase with two peaks, one at the onset of lights-on and the other 8-12 h after lights-on, indicating that most copulation activity in B. longissima in the field occurs in the early morning and the afternoon. Females could copulate immediately after emergence, whereas males began copulating 3 wk after emergence. Ovaries of females started to develop in the absence of mating and were correlated with adult age. Mature males could copulate with females regardless of ovarian developmental stage, and females with undeveloped ovaries accepted copulation attempts. Our study showed that the tinting of copulation during the preoviposition period would not affect numbers of eggs laid, length of preoviposition period, or viability of eggs. B. longissima adults engaged in multiple mating. [ABSTRACT FROM AUTHOR]

The coconut hispine beetle Brontispa longissima has been causing serious damage to the coconut palm Cocos nucifera in the Pacific, and Southeast and East Asia. This beetle also attacks Satakentia liukiuensis, an endemic palm on Ishigaki and Iriomote Islands, Japan. To assess the potential impact of B. longissima on S. liukiuensis, we examined the development period, survival rate, egg production and body size of B. longissima on S. liukiuensis at 22-31°C and consumption of S. liukiuensis leaf at 28°C. We also examined these life history traits on C. nucifera at 28°C to compare with those on S. liukiuensis. Brontispa longissima completed their development and reproduced on S. liukiuensis at 22-30°C. Linear regression analysis was used to estimate the effective cumulative temperature ( k) as 891.2 degree-days, and the lower developmental threshold as 13.3°C. On the basis of these values and monthly average temperatures on Ishigaki Island, it was estimated that B. longissima has four generations per year on the island. Satakentia liukiuensis was less suitable for B. longissima than C. nucifera in terms of immature survival, development time, resultant adult size and reproduction. The low quality of S. liukiuensis as a host-plant may prevent the outbreak of B. longissima, which has not occurred yet on Ishigaki and Iriomote Islands. [ABSTRACT FROM AUTHOR]