Entomologia Experimentalis et Applicata最新文献

Symbionts form intricate associations with their hosts. They can only establish when potential hosts are present, but in addition, their distribution is often influenced by microhabitat preferences, which may not overlap those of their hosts. This leads to a patchy local distribution of the symbiont, being present with some hosts and absent with others. We studied this effect of microhabitat preferences on symbiont distribution by examining the occurrence and density of the obligately ant-associated springtail Cyphoderus albinus Nicolet (Collembola: Paronellidae) across a mosaic of ant nests. Nest structure strongly varied both within and between ant species and included sand, dead wood, arboreal and thatch mound nests. We hypothesized that the symbiotic springtail would show the strongest preference for thermoregulated and organic-rich nests such as thatch mounds. The springtail was found in all thatch mound nests of red wood ants and in all arboreal nests of Lasius fuliginosus (Latreille). A high occurrence (75%) was recorded in the smaller thatch nests of Formica sanguinea Latreille. Lasius, Myrmica and Formica species exhibited variation in nest structures on the ground, establishing nests in both sand and wood. For each of these three host taxa, encountering the springtail was more likely in their wood nests (medium-to-high occurrence), than in their sand nests where the occurrence was low. Nest structure did not only impact springtail occurrence, but their densities as well. The densities within thatch nests were much higher than those in other nest types, achieving the highest densities (1148 individuals per litre of nest material) observed for a social insect symbiont. Our findings emphasize that host nests with wood structures and thatch material provide a more favourable habitat for the springtail compared with soil nests. Overall, this study underscores the role of microhabitat variation in the spatial distribution and density of a symbiotic species.

The ability to estimate the risk of pest infestation can help farmers to reduce pesticide application and provide guidance that would result in better management decisions. This study tested whether different combinations of spatial and temporal risk factors may be used to predict the damage potential of pea moth, Cydia nigricana Fabricius (Lepidoptera: Tortricidae), a major pest in field pea (Pisum sativum L., Fabaceae). Over four consecutive years, the abundance of pea moth was monitored by placing pheromone traps at various field pea-cultivation sites. We also assessed the phenological development stages and the percentage of damaged seeds per 100 pods collected from each growing pea field in a region of approximately 30 km in diameter. The study found the significant infestation risk indicators to be the time of flowering, the date on which male pea moths are first detected in the monitoring traps and the minimum distance to pea fields that were planted and harvested in the previous growing season. The combination of all three factors using a general additive model approach yielded the best results. The model proposed by this study accurately discriminated between low-infestation and high-infestation fields in 95% of cases.

Batocera horsfieldi (Hope) (Coleoptera: Cerambycidae) is an important pole borer pest. It causes serious harm to various hosts, particularly Juglans regia L. (Juglandaceae). In this study, headspace solid-phase microextraction (HS-SPME), gas chromatography–mass spectrometry (GC–MS), and electroantennogram (EAG) responses were combined to examine the mechanism by which B. horsfieldi adults locate their host, J. regia. The results showed that J. regia contained 65 volatile compounds in all, with 36 and 42 volatile substances in bark and leaves, respectively. Moreover, terpenes accounted for the largest relative content among the volatile compounds of bark and leaves, 43.4 and 78.9%, respectively. Ten of 19 selected volatile components elicited significant EAG responses in adult B. horsfieldi, which indicated that the pest may prefer certain volatile compounds when selecting a host. Sex and volatile concentration affected the responses of B. horsfieldi. Male adults had the strongest EAG responses to 1-octen-3-ol, whereas female adults had the strongest EAG responses to linalool. Host selection in B. horsfieldi was somewhat positively associated with the concentrations of the effective volatile compounds in the host. Furthermore, B. horsfieldi showed varying preferences for isomers. This work provided data support for the development of insect attractants, and laid a theoretical foundation for the ecological protection of local forestry.

In most ectotherms, several life-history traits, including body size, respond to environmental conditions through the temperature–size rule (TSR). The mechanisms underlying the TSR are still being debated, but studying idiobiont insect parasitoids, which develop with a fixed amount of resources, may shed light on this relationship. In this study, we conducted experiments to determine how the developmental temperature affects various characteristics of male and female Trichogramma euproctidis (Girault) (Hymenoptera: Trichogrammatidae), an idiobiont egg parasitoid of Lepidoptera. The study tested various hypotheses, including the cellular or oxygen diffusion hypotheses and the resource acquisition hypothesis, to understand whether T. euproctidis follows the TSR. The developmental time of both male and female T. euproctidis decreased with increasing temperature. Both males and females displayed a unimodal distribution for size, dry mass, and lipid content, with individuals at lower and higher temperatures being smaller, weighing less, and containing fewer lipids. Female lifetime fecundity increased from 13 to 24 °C and then decreased at 31 °C. Additionally, the number and size of gametes in male and female T. euproctidis displayed a unimodal distribution with increasing temperature. Trichogramma euproctidis deviates from the TSR as it follows a non-linear reaction norm with an optimal developmental temperature. This result supports the hypothesis that for species following TSR and having unlimited access to food resources, the resource acquisition hypothesis is a significant mechanism explaining the TSR. With climate change affecting temperature, understanding the TSR is crucial, and research on insect parasitoids may help reveal how the interplay between environmental temperature and resource allocation affects the TSR in natural populations.

The incidence of thrips in the High Plains of Texas (USA) was investigated using sticky traps during the 2021 and 2022 seasons. Yellow sticky traps were placed in wheat fields and collected and replaced weekly and thrips were counted under a dissecting scope. Weekly wheat reflectance measurements were taken using a hyperspectral radiometer from which normalized difference vegetation index (NDVI) was calculated for each measurement. Temperature (degree day) and NDVI values were then related to weekly thrips incidence using regression. Thrips incidence curvilinearly increased over time during each of the two seasons and reached a maximum in the middle of June, after which it declined sharply. There was a strong positive relationship between degree days and thrips incidence until the incidence reached a maximum, whereas the incidence was negatively related to NDVI values. Analysis of the thrips changes over time progress with the two variables together showed that degree day has greater impact on thrips incidence than NDVI. However, the steep decline in thrips abundance after its peak in mid-June suggests that senesced wheat fields with NDVI values near zero are not significant sources of thrips, signifying the importance of wheat growth stages in the seasonal population dynamics of thrips. Overall, the 2-year results were generally consistent in trends of thrips incidence during the season, which may need to be considered when choosing vegetable planting dates in the region.

The Asian Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) is a harmful invasive pest widespread throughout Argentinian fruit-producing regions. It coexists with both pests, the sub-Saharan African Ceratitis capitata (Wiedemann) and the Neotropical-native Anastrepha fraterculus (Wiedemann) (both Diptera: Tephritidae), in northwestern Argentina. The Neotropical-native parasitoid Ganaspis pelleranoi (Brèthes) (Hymenoptera: Figitidae) is frequently found in non-crop fruit infested by those frugivorous dipterans. The northwestern Argentinian region is known for producing and exporting berries and citrus, which are affected by those pests. Thus, eco-friendly control strategies are under assessment. This study mainly assessed the potential of the G. pelleranoi population lineage from Tucumán (Gp_Tuc) as a D. suzukii biocontrol agent. First, both the host-killing effectiveness and the reproductive success of Gp_Tuc on larvae of D. suzukii, C. capitata, A. fraterculus, and Drosophila melanogaster Meigen were compared in no-choice tests under laboratory conditions. Then, the Gp_Tuc host preference was evaluated in dual-choice tests (D. suzukii vs. C. capitata or A. fraterculus) under laboratory and field conditions. Naive parasitoid females were allowed to forage for 8 h on screen-covered Petri dishes filled with host larvae under laboratory conditions and for 48 h on peaches inoculated with host larvae under field conditions. Host puparia dissections were performed to determine the number and condition of parasitoid eggs, first and second instars, such as alive/dead, without/with melanization process, and proportions of parasitized, superparasitized, and dead puparia. Drosophila suzukii was not a suitable host for the successful development of Gp_Tuc immature stages as they did not overcome the host's immune system. However, Gp_Tuc performed efficiently regarding D. suzukii mortality, but parasitoid specificity was restricted to both tephritid species as only thriving offspring were achieved from them. Interestingly, the effectiveness of Gp_Tuc on D. suzukii increased when it co-occurred with C. capitata instead of A. fraterculus, the preferred host.

Overwintering conditions affect the physiological state of ectotherms, and therefore, their cold hardiness and survival. A measure of the lethal and sublethal impacts of overwintering conditions on pest populations is crucial to predict population dynamics and to manage pests the following spring. The impact of winter conditions can be most intense for invasive insects undergoing range expansion. Insect herbivores can display plastic host use behaviours that depend on their body condition following winter. The pea leaf weevil, Sitona lineatus L. (Coleoptera: Curculionidae), is an invasive pest of field peas, Pisum sativum L., and faba bean, Vicia faba L. (Fabaceae). Pea leaf weevil has expanded its range in North America to include the Prairie Provinces of Canada. This study investigated the effects of temperature and microhabitat on overwintering survival and cold hardiness of pea leaf weevil in its expanded range. Further, we investigated the sublethal effect of overwintering temperature and duration on post-overwintering survival, feeding, and oviposition of pea leaf weevil. We also investigated the role of juvenile hormone in modulating body condition of overwintering weevils. The overwintering survival of pea leaf weevil adults increased with soil temperature and varied with region and microhabitat. More weevils survived winters when positioned near tree shelterbelts compared to open alfalfa fields. The supercooling point of pea leaf weevil varied throughout its expanding range but did not differ for weevils held in the two microhabitats. The average threshold lethal temperature of pea leaf weevil at all three sites was −9.4 °C. Weevils that overwintered for a longer duration and at a higher temperature subsequently fed more on faba bean foliage and laid more eggs compared to those which overwintered for a shorter duration at a lower temperature. Our findings highlight that warm winters would increase overwintering survival and post-overwintering fitness, facilitating further pea leaf weevil invasion northward in the Prairie Provinces of Canada.

Frass, a byproduct of insect rearing, has become popular for its potential use in sustainable agriculture. The rapid growth of insect production results in an increased frass output. This study examined the effects of frass as soil amendment on plant growth and resistance to insect herbivory. In greenhouse experiments, Brassica rapa L. (Brassicaceae), was grown in unamended soil (NoFrass; control) or soil amended with frass (2 g kg⁻¹) from larvae of black soldier fly (BSFF), Hermetia illucens L. (Diptera: Stratiomyidae), or yellow mealworm (MWF), Tenebrio molitor L. (Coleoptera: Tenebrionidae). Frass was applied as raw, incubated, or composted frass before seed germination. Plant growth and performance were measured of larvae of root-feeding Delia radicum L. (Diptera: Anthomyiidae) and shoot-feeding Plutella xylostella L. (Lepidoptera: Plutellidae). Initially, raw BSFF and MWF reduced the growth of B. rapa and resulted in a smaller leaf area than NoFrass. However, over time, a notable trend emerged. Whereas the difference in leaf area between MWF and NoFrass disappeared, BSFF consistently resulted in a smaller leaf area than MWF and NoFrass. Raw BSFF reduced D. radicum larval survival and pupal biomass and larval survival of P. xylostella. In contrast, raw MWF increased larval survival and biomass of D. radicum and the survival of P. xylostella larvae. Interestingly, incubation of frass in the soil for 16 days before seed germination removed plant growth inhibition and increased plant leaf area, especially for MWF compared to NoFrass. In addition, composting MWF increased leaf growth. Therefore, frass may be used as a sustainable and natural alternative to conventional organic fertilisers, promoting plant growth and enhancing resistance to herbivory. Our results indicate that soil amendment with raw BSFF may negatively impact herbivore performance, whereas raw MWF may enhance herbivore performance.

Competition between parasitoids for available hosts is common in insects. These interactions are often negative and are believed to reduce the overall impact of top-down population regulation. In the spruce budworm, Choristoneura fumiferana (Clemens) (Lepidoptera: Tortricidae), two parasitoid species are very common and often interact during the period of low-density populations between outbreaks: the koinobiont endoparasitoid Tranosema rostrale (Brishke) (Hymenoptera: Ichneumonidae) and the idiobiont ectoparasitoid Elachertus cacoeciae (Howard) (Hymenoptera: Eulophidae). Data collected from field-implanted larvae of spruce budworm exposed in summer during a 35-year period between 1987 and 2022 were used to estimate the response of these two parasitoids to the density of their spruce budworm host, and the nature and importance of competitive interactions between them. It was found that both parasitoids are most effective at very low host population density, and that a strong, density-dependent, and negative correlation of frequencies exists between them. This negative correlation is evident both among and within years and indicates that the parasitoids have developed seasonal history and host choice behaviors that tend to minimize the negative impact of direct competition on their respective performance. It appears that the koinobiont T. rostrale manages, through those adaptive strategies, to avoid direct competition inside a larval host with the competitively superior idiobiont E. cacoeciae.

Regeneration has been a topic of interest across a range of taxa for centuries, and arthropods are no exception. Trade-offs associated with regeneration are likely to involve the reallocation of resources away from other metabolic activities such as growth, development or reproduction. This might be reflected in costs to some developmental traits of the organism, despite regeneration being advantageous. These associated costs might also differ with the stage of injury or amputation. Here, we hypothesise that the extent of regeneration and trade-offs associated with it may be stage-specific. To test this hypothesis, the right forelimb of four larval stages of the ladybird beetle Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae) was amputated. Amputated individuals were reared until adulthood, and all developmental transitions were recorded. Regenerated legs in all the treatments were smaller than the controls, which did not experience the amputation, and the regenerative potency of early larval stages was higher than that of late larval stages. Limb regeneration caused delays in post-amputation developmental duration in all the treatments, increasing their total developmental period. The length of the unamputated left foreleg as well as the wing and antenna size were also reduced in regenerated beetles, showing some internal trade-off. However, there were no significant differences observed between regenerated and control adults in their fresh body weight and body size. Thus, limb regeneration depends upon the stage of larval development at which the amputation was performed. Amputation also affects the development of other appendages. The delay in normal beetle development might have been observed because of extra resource requirement, their allocation as well as reprogramming of the expression of some genes during regeneration.