摘要: Although the Neotropical territorially dominant arboreal ant Azteca chartifex Forel is very aggressive towards any intruder, its populous colonies tolerate the close presence of the fierce polistine wasp Polybia rejecta (F.). In French Guiana, 83.33% of the 48 P. rejecta nests recorded were found side by side with those of A. chartifex. This nesting association results in mutual protection from predators (i.e., the wasps protected from army ants; the ants protected from birds). We conducted field studies, laboratory-based behavioral experiments and chemical analyses to elucidate the mechanisms allowing the persistence of this association. Due to differences in the cuticular profiles of the two species, we eliminated the possibility of chemical mimicry. Also, analyses of the carton nests did not reveal traces of marking on the envelopes. Because ant forager flows were not perturbed by extracts from the wasps' Dufour's and venom glands, we rejected any hypothetical action of repulsive chemicals. Nevertheless, we noted that the wasps scraped the surface of the upper part of their nest envelope using their mandibles, likely removing the ants' scent trails, and an experiment showed that ant foragers were perturbed by the removal of their scent trails. This leads us to use the term erasure hypothesis. Thus, this nesting association persists thanks to a relative tolerance by the ants towards wasp presence and the behavior of the wasps that allows them to contain their associated ants through the elimination of their scent trails, direct attacks, wing-buzzing behavior and ejecting the ants.

摘要: We tested the recent hypothesis that the fly factor phenomenon (food currently or previously fed on by flies attracts more flies than the same type of food kept inaccessible to flies) is mediated by bacterial symbionts deposited with feces or regurgitated by feeding flies. We allowed laboratory-reared black blow flies, Phormia regina (Meigen), to feed and defecate on bacterial Luria-Bertani medium solidified with agar, and isolated seven morphologically distinct bacterial colonies. We identified these using matrix-assisted laser desorption/ionization mass spectrometry and sequencing of the 16S rRNA gene. In two-choice laboratory experiments, traps baited with cultures of Proteus mirabilis Hauser, Morganella morganii subsp. sibonii Jensen, or Serratia marcescens Bizio, captured significantly more flies than corresponding control jars baited with tryptic soy agar only. A mixture of seven bacterial strains as a trap bait was more attractive to flies than a single bacterial isolate (M. m. sibonii). In a field experiment, traps baited with agar cultures of P. mirabilis and M. m. sibonii in combination captured significantly more flies than traps baited with either bacterial isolate alone or the agar control. As evident by gas chromatography-mass spectrometry, the odor profiles of bacterial isolates differ, which may explain the additive effect of bacteria to the attractiveness of bacterial trap baits. As generalist bacteria, P. mirabilis and M. m. sibonii growing on animal protein (beef liver) or plant protein (tofu) are similarly effective in attracting flies. Bacteria-derived airborne semiochemicals appear to mediate foraging by flies and to inform their feeding and oviposition decisions.

摘要: Reflex bleeding is an important antipredator defense mechanism in Coccinellidae. We examined the costs of reflex bleeding in larval and adult stages of the ladybird beetle Harmonia axyridis on offspring fitness and reproductive performance through the comparisons between bled and control larvae, reciprocal crosses of bled/control beetles, and early and late clutch phenotypes. Beetles bled during their larval stage spent a longer time in development and weighed less than controls. Egg fertility was reduced for crosses where either one or both parents had been bled during the larval or adult stage. Offspring crosses that included a parent bled during the larval stage suffered fitness costs in development and female body mass, while those bled during the adult stage suffered no transgenerational costs. Males that suffered bleeding during their larval stage accelerated progeny development of nonbled females in early clutches, suggesting a positive transgenerational effect of larval bleeding, while males that did not suffer bleeding accelerated progeny development of bled females in later clutches. As the underlying effects of bleeding on females' offspring in the early clutches were diminished in the late ones, suggesting another transgenerational effect. The strengths of maternal and paternal effects on progeny development of parents bled at the larval stage were higher in earlier clutches. This study suggests that H. axyridis adults are less affected than larvae by the frequent use of the defensive secretions in their stressful habitats.

摘要: Intraguild predation (IGP) has been commonly reported between predators and parasitoids used as biological control agents as predators consuming parasitoids within their hosts. However, the effect of parasitoid-mummy consumption on the fitness of the predator and subsequent oviposition site selection have not been well studied. In our study, we conducted two laboratory experiments to examine the influence of Aphidius gifuensis Ashmead (Hymenoptera: Braconidae) mummies as prey on fitness and subsequently oviposition site selection of Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Results indicate that when H. axyridis was reared on A. gifuensis mummies only, its larval development was prolonged, and body weight of the 4th instar larvae and newly emerged adults, and fecundity decreased. Moreover, H. axyridis did not exhibit oviposition preference on plants infested with unparasitized aphids or aphids parasitized for shorter than 9 days. However, compared with plants with mummies (parasitized >= 9 days), H. axyridis laid more eggs on plants with unparasitized aphids. In contrast, H. axyridis previously fed with A. gifuensis mummies did not show a significant oviposition preference between plants with unparasitized aphids and those with mummies (parasitized >= 9 days). Overall, our results suggest that mummy consumption reduced the fitness of H. axyridis. Although H. axyridis avoided laying eggs on plants with A. gifuensis mummies, prior feeding experience on A. gifuensis mummies could alter the oviposition site preference. Thus, in biological control practice, prior feeding experience of H. axyridis should be carefully considered for reduction of IGP and increase of fitness of H. axyridis on A. gifuensis.

摘要: Seminal gifts range from important material donations to items that provide little direct benefit to females. Promiscuous, female silk corn flies Euxesta eluta expel and consume male ejaculates immediately after mating. The evolution and function of this peculiar behavior are currently unknown. We performed a series of experiments aimed to: determine if females under different dietary regimes derive nutrients or water for survival and/or reproduction from ejaculate consumption, if males suffer a fitness cost from supplying females with ejaculates, and if females prefer to mate and/or are more likely to store sperm from well fed than nutritionally stressed presumably inferior males. Experiments revealed that protein deprived E. eluta females derive nutrients for ovarian development through consumption of ejaculates of protein fed males. No seminal products affecting survival appear to be transferred in the consumed ejaculate. However, ovarian development, in contrast to testes growth, occurs in detriment of longevity. Females preferred to mate with protein fed males, yet sperm retention in spermathecae was extremely rare after a single mating. This finding suggests that females could be exerting post copulatory control. A key question that remained to be addressed for the understanding of this puzzling and promiscuous mating system is what ecological factors or male traits drive females to retain sperm from one or several males in order to achieve and/or maximize fertilization potential.