Entomologia Experimentalis et Applicata最新文献

Fluctuations in food availability and larval density play pivotal roles in shaping the characteristics of Aedes (Stegomyia) aegypti (L.) (Diptera: Culicidae) mosquito populations through intraspecific competition. Competition for limited resources drives density-dependent effects, influencing survival rates, time to pupation, and the size and lifespan of adult mosquitoes. Our study aimed to investigate the effects of competition, driven by variations in food and larval density, on the development and life cycle of A. aegypti. We examined the outcomes of nine distinct combinations of aquatic larval density and resource availability—measured in terms of per capita food and individual space—on key developmental metrics, including larval mortality, time to pupation, adult size, and lifespan. Our findings indicate that food availability had a more pronounced effect on larval mortality and development time than did larval density. Notably, intermediate levels of food availability and density were more conducive to higher survival rates and larger adult sizes than either low-density conditions or an excess of resources. The density-dependent effects, particularly, had a significant impact on adult size, often outweighing the influence of food availability. Furthermore, alleviation from competition among larvae emerged as a more critical factor in extending adult lifespan than the direct influence of resources or density alone. In conditions where food resources were scarce or competition was intense, larvae experienced prolonged development times and a higher likelihood of failing to pupate, resulting in smaller adults with reduced lifespans. These combined stressors significantly diminish the fitness (i.e., mortality and developmental parameters) of A. aegypti, highlighting the complex interplay between resource availability and intraspecific competition in determining the population dynamics of this species.

The wheat midge, Sitodiplosis mosellana (Géhin) (Diptera: Cecidomyiidae), poses a threat to spring wheat in North America. Larvae feed on the developing kernels, causing decreased grain quality and yield loss. The resistance gene Sm1, a single, naturally occurring gene that results in larval mortality, is important for managing this pest. However, relying on a single resistance gene may result in the evolution of virulent pest biotypes. To identify possible alternative mechanisms of resistance, mechanical deterrence against wheat midge oviposition was evaluated using doubled haploid spring wheat lines (DH lines) with different combinations of awns and hairy glumes. Adult wheat midges were introduced to cages containing 12 preanthesis wheat spikes consisting of combinations of the presence or absence of awns with either hairy or smooth glumes, and oviposition on these phenotypes was recorded. In addition, kernel damage of five lines per phenotype was assessed under field conditions. The presence of awns on wheat spikes reduced oviposition in the laboratory choice cages, but not all wheat lines with awns reduced damage in the field. Hairy glumes did not reduce midge oviposition or grain damage. Independent of the awned and hairy-glumed phenotypes, egg numbers and damage varied among the DH lines. Four wheat lines exhibited wheat midge deterrence and are promising candidates as sources of novel resistance to combine with Sm1 to pyramid resistance.

Counterattacks against predators are reported in several web-nesting spider mites (Acari: Tetranychidae) that display communal sociality. For example, adults of Stigmaeopsis longus (Saito) kill phytoseiid larvae that invade their nests. We recently found similar defensive behaviours in various life stages of Schizotetranychus brevisetosus Ehara, a specialist of evergreen oak Quercus glauca Thunb. (Fagales: Fagaceae), which attack larvae of Feltiella acarisuga (Vallot) (Diptera: Cecidomyiidae) in groups outside the nest. However, due to the limited number of observations, we could not establish the factors inducing this counterattack or its efficiency against general predators. We conducted two experiments to evaluate the degree of S. brevisetosus female attacks against abiotic substances and living organisms. First, we assessed the behaviours towards predator-mimicking glass beads (50–400 μm in diameter) randomly spread over the leaf surface. Second, we monitored the 24-h survival of phytoseiid eggs (Amblyseius swirskii Athias-Henriot, Acari: Phytoseiidae) evenly placed near S. brevisetosus nests under various experimental conditions, including the presence or absence of adult mites, intact or removed webs, and the presence or absence of a phytoseiid larva to stimulate females (because phytoseiid larvae easily enter web nests, their presence may provoke counterattacks). In the first experiment, females responded immediately to the glass beads of all sizes, although their activity gradually declined over the subsequent 3-day period. Three types of behaviours were observed: patrolling around the nest, pecking the glass beads, and grasping them. In the second experiment, approximately 20% of phytoseiid eggs died when females were present, whereas no eggs died in their absence. There was no effect of webs and phytoseiid larvae on the mortality of eggs. These results demonstrated that physical stimuli play a role in evoking counterattacks in S. brevisetosus females and thereby reduce potential predation risks.

Herbivorous insects can interact with plants in ways that go beyond nutrition, with plant specialized (secondary) metabolites (PSMs) mediating complex non-nutritional relationships. While PSMs often function as anti-herbivore defenses, many insects have evolved strategies to counteract and even exploit these compounds, using them for purposes such as their own defense against antagonists, enhanced mating success, or self-medication. This review explores pharmacophagy, where insects actively seek and acquire specific PSMs from both food and non-food plants for benefits unrelated to nutrition, across different insect orders such as Orthoptera, Lepidoptera, Hymenoptera, Coleoptera, Diptera, and Neuroptera. Key examples are provided for species taking up PSMs of different compound classes, including pyrrolizidine alkaloids, cardiac glycosides, neo-clerodane diterpenoids, cucurbitacins, raspberry ketone, methyl eugenol, and other metabolites such as ethanol or resin. The insect species demonstrate unique adaptive uses of these non-nutritional plant chemicals. We discuss the intra- and intergenerational transfer of pharmacophagously acquired PSMs among conspecifics and the methods for identifying and testing pharmacophagy, emphasizing the importance of interdisciplinary approaches that combine field observations, behavioral studies, and chemical analyses. The evolutionary pathways leading to pharmacophagy are considered, highlighting selective pressures such as predation, parasitism, and sexual selection. We also address the costs associated with pharmacophagy, including energetic demands and potential toxicity. Extending the discussion to non-insect taxa suggests that pharmacophagy may be a broader ecological phenomenon. By establishing a comprehensive framework for understanding pharmacophagy, we aim to stimulate further research into this intriguing aspect of plant–insect interactions and highlight its potential applications in pest management, conservation, and human health.

The swallowtail butterfly Battus polydamas L. (Lepidoptera: Papilionidae) is a specialist on Aristolochia (Aristochiaceae). Larvae sequester secondary compounds, such as aristolochic acids (AAs), from their host plants and transfer them to adults through the pupae. In this study, we evaluated the performance of B. polydamas larvae fed from 1st instar through pupation on two host plants with distinct chemical compositions, Aristolochia ringens Vahl. (which has several diterpenes) and Aristolochia gigantea Mart. (which has acyclic monoterpenoids and sesquiterpenoids, but no diterpenoids or AAs). Differential gene expression in gut and fat body tissues in response to two larval host plants was evaluated in 5th-instar larvae. We found significant differences in the survival of larvae feeding on the two host plants; the survival in A. gigantea is significantly higher than survival in A. ringens. In A. gigantea, 46% of the larvae persisted until pupation, whereas none of the larvae feeding on A. ringens survived until the end of larval development. Upregulated and downregulated contigs comprise genes encoding ribosomal proteins, protein farnesyltransferase, phosphomevalonate kinase, dolichyl-phosphate-mannose-protein mannosyltransferase 4, and O-glucosyltransferase (possibly involved in AA metabolization), as well as genes encoding superoxide dismutase, P450s, UGTs, glutathione S-transferase, and many proteases. As expected, larvae of B. polydamas were strongly influenced by host plants containing different compounds, leading to worse larval performance on key fitness components, such as life cycle performance attributes and larval survival. We suggest that there is a threshold of toxicity in the host plant that larvae can tolerate, and above such a threshold, the impact of plant secondary chemicals is no longer beneficial for the larvae but negative, disrupting their detoxification mechanism.

The sex pheromones of moths consist of multiple components that serve as chemical signals emitted by female individuals to attract male counterparts for mating purposes. Desaturases, which are key enzymes involved in creating unsaturated bonds on fatty acid chains, play a critical role in producing specific sex pheromone components. In this study, the Old World bollworm, Helicoverpa armigera Hübner (Lepidoptera: Noctuidae), was used as a model to identify a desaturase gene called Hades11, which showed a high level of expression in the pheromone glands. RNA interference-mediated knockdown of Hades11 led to a significant decrease in the production of the main sex pheromone components (Z11-16:Ald and Z9-16:Ald). However, the ratio of sex pheromone components remained unchanged, indicating that Hades11 specifically affects sex pheromonal compound biosynthesis rather than their release ratio. Furthermore, inhibiting the expression of Hades11 also caused a notable reduction in the total number of eggs laid by female moths, without affecting the hatching rate. Importantly, it was found that the expression level of Hades11 may be indirectly regulated by pheromone biosynthesis activating neuropeptide (PBAN) and PBAN receptors in H. armigera.

Herbivores consume large quantities of plant tissues while excreting excess elements to compensate for mismatches between the element content in their food plants and their physiological needs. This energetically costly excretion process decreases the fitness of herbivorous insects, yet how stoichiometric mismatches with food plants vary during their development remains poorly understood. In this study, we reared 4th- and 5th-instar caterpillars of Micromelalopha sieversi (Marumo) and Clostera anachoreta (Denis & Schiffermüller) (both Lepidoptera: Notodontidae) on fresh poplar leaves to investigate changes in carbon: nitrogen ratio in their bodies during development. We measured the weight of the caterpillars and analyzed the carbon (C) and nitrogen (N) contents in their bodies, frass, and consumed plants. Results showed that the 5th-instar caterpillars gained three times more body mass, absorbed and assimilated two times more N and three times more C than the 4th instar. C content in the caterpillar body increased, while N content decreased as the caterpillars developed. Consequently, a greater stoichiometric mismatch with host plants was observed in the 4th instar than in the 5th, as plant quality remained constant throughout development. In addition, N content in frass significantly increased from 4th- to 5th-instar caterpillars, indicating that caterpillars excrete more N in later development stages. Our study clearly revealed the decreasing extent of nutrient imbalance in the later stage of herbivorous insects, highlighting the need to incorporate changes in element contents during organismal development in studies of ecological stoichiometry.

The insect-resistant rice variety mfb-MH3301-1, expressing Cry1Ab, has demonstrated robust resistance against Lepidopteran pests. However, its potential effects on non-target organisms warrant further investigation. This study evaluated the effects of mfb-MH3301-1 in comparison with the parental rice variety MH3301 (Oryza sativa L.) on the development of the insect pest Nilaparvata lugens (Stål) (Homoptera: Delphacidae). The results showed that there were no significant differences in female longevity, male longevity, lifespan, and mean generation time (T) between brown planthoppers fed on either mfb-MH3301-1 or MH3301. However, N. lugens individuals fed on mfb-MH3301-1 exhibited significantly higher fecundity, intrinsic rate of increase (r), finite rate of increase (λ), and net reproductive rate (R₀) compared to those fed on MH3301. The study provides valuable insight into the management of N. lugens in the future cultivation of Bt rice, and attention should be paid to the population dynamics of N. lugens in the field.

There is growing interest in trait selection for the improvement of insect biological control. Constraints from the Nagoya Protocol for sourcing novel biocontrol agents (BCAs) make optimization of accessible populations a higher priority. However, the effectiveness of selection programs remains unclear. This requires knowing whether biocontrol traits are heritable and whether captive populations have sufficient genetic variation for selection. To address this knowledge gap, we systematically reviewed reported values of broad-sense heritability (H²), narrow-sense heritability (h²), and evolvability (CV_a) for insect biocontrol traits, providing an overview of the potential for their genetic improvement while identifying the irregularities in the reporting of heritability data across studies. Our algorithmic search string focused on studies working with arthropod BCAs widely used in augmentative biocontrol and/or permitted for use in the EPPO region (European and Mediterranean Plant Protection Organization). Five thousand two hundred and nine initial search hits from the CAB Abstracts (n = 2321) and BIOSIS (n = 3442) databases recovered 277 relevant papers after screening, 94 of which included estimation methods and reported biocontrol traits as being heritable. However, over half (52) of these papers did not report any H², h², or CV_a values. There was strong indication of genetic variation (e.g., h² > 0.2) for numerous traits. Most data focused on pest suppression ability and mass reproduction, while little was reported on abiotic/biotic adaptation or ecological risk, despite their importance for biocontrol success. Contrary to expectations, heritabilities for complex life-history traits were equally high as those for morphology, whereas the heritability of insecticide resistance was relatively low. Despite relatively few data points and a large value range, this review demonstrates good potential for artificial selection of biocontrol traits and provides a single resource for collated data. We make recommendations for more consistent and expansive collection and repository of biocontrol trait data and to revise the Nagoya Protocol to facilitate breeding programs.

Myzus persicae (Sulzer) (Hemiptera:Aphididae) aphids feed on a wide range of host plants but exhibit strong preferences for plants from some families, particularly Brassicaceae. Previous studies demonstrate local adaptation of M. persicae populations, where populations collected on a given host plant have increased performance on this host, highlighting the potential for plant preferences and fitness to shift through cross-generational changes or rearing on different plants within generations. Endosymbionts living within aphid cells can have substantial impacts on aphid fitness and also influence host plant responses. Rickettsiella is a facultative endosymbiont that shows potential biocontrol applications due to its host fitness costs, but it is unclear if costs change when aphids are reared on different host plants across generations. In experiments with two M. persicae lines (one carrying a transinfection of Rickettsiella) we show that maintenance for 15 generations on leaf discs of three different host plants (bok choy, clover and potato) had little effect on fitness when reciprocally tested on each host plant. Fitness was mainly influenced by the host plant used for testing compared with cross-generational effects. In two-choice Petri dish experiments involving bok choy and clover, maintenance for 15 generations on either plant had no effect on plant preferences, but aphids acclimated to clover shifted their preference towards clover. The transinfected endosymbiont Rickettsiella was stable in all lines, where its deleterious effects and body colour alterations were not dramatically modified by the host plant used for maintenance or testing. This study highlights the adaptability of M. persicae to diverse host plants, stable transinfected endosymbiont effects and the importance of within-generational host plant effects for fitness, with implications for the use of endosymbionts for pest management.