Applied Entomology and Zoology最新文献

Population models provide a logical knowledge base before conducting laborious and expensive field experiments. Historically, two types of population models have been developed: highly realistic simulations and simple analytical models. Highly realistic simulations comprise a complicated systems model, whereas simple analytical models comprise various analytical models that focus only on the fundamental structure of the target pest population. Although both approaches have contributed to pest management science, each has limitations, poor predictability, and lacks substantial connections to reality. Assimilation by state-space modeling, in which observation and process models are jointly incorporated, is a good compromise between a simple model and reality in nature. In the big data era, artificial intelligence (AI), specifically aimed at high predictability, has recently become popular. If vital physical and biological records are automatically censored in the field with high precision, AI will produce the most plausible predictions, providing the best practical solution given our current knowledge. AI can be a powerful tool in the contemporary world; however, deductive modeling approaches are still important when considering the behavior of AIs and may also provide important insights to detect deficient information in the data.

Among the hemocytes of Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae), oenocytoids are lysed very quickly after hemolymph collection. We clarified that the lysis of oenocytoids can be greatly inhibited by collecting hemolymph under the introduction of carbon dioxide (CO₂) gas. Since nitrogen and helium gasses were ineffective in inhibiting oenocytoid lysis, it was concluded that CO₂ itself was necessary to inhibit lysis. Insect anesthetization with CO₂ gas before bleeding was not necessary to prevent oenocytoid lysis, but CO₂ gas was required at and after the time of bleeding. When the hemolymph was collected in a Petri dish under CO₂ gas and sealed, oenocytoids remained present without lysis even after an hour at 25 °C. Oenocytoids were not irreversibly fixed since lysis occurred when this hemolymph was exposed to air. When the hemolymph was collected in air, granulocytes adhered to the bottom surface of the Petri dish, and plasmatocytes spread out on the bottom surface. However, when collected under CO₂ gas, both types of hemocytes remained spherical, and few cells were observed to spread out on the bottom surface. Thus, it was suggested that oenocytoid lysis inhibition by CO₂ gas is associated with the suppression of defensive reactions to foreign materials by hemocytes. This hemolymph collection method can be easily performed without special pretreatment of the hemolymph. Accordingly, this method is considered to be advantageous for studying the possible role of oenocytoids associated with host defense mechanisms in insects.

Diapause is a programmed stage-specific arrest or delay in reproduction or development and is commonly used to circumvent an adverse season. Some insect species exhibit maternal regulation of diapause, wherein environmental cues are perceived by the mother and subsequently determine the developmental fate of the offspring. Although maternal regulation of diapause is widespread, its endocrinological mechanisms remain largely unknown. In the band-legged ground cricket Dianemobius nigrofasciatus (Orthoptera: Trigonidiidae), embryonic diapause is maternally determined. Adult females under long-day conditions lay eggs that develop into nymphs without interruption, whereas those under short-day conditions lay diapause-destined eggs that arrest their development and enter diapause at a very early embryonic stage, the cellular blastoderm. How development is arrested at an early stage is a key area of interest. We hypothesized that juvenile hormone III (JH III) and 20-hydroxyecdysone (20E), the major insect hormones that regulate a wide variety of physiological processes, are involved not only in maternal decisions, but also in diapause entry in D. nigrofasciatus. The results showed that the hemolymph concentrations of JH III and 20E in adult females were lower under short-day conditions; however, the application of JH III and 20E to the mothers did not affect the diapause incidence of offspring. No differences were observed in the amounts of 20E between non-diapause and diapause-destined eggs, and JH III was not detected in these eggs. Thus, we found no evidence for the involvement of JH III and 20E in maternal decisions for embryonic diapause and diapause entry in D. nigrofasciatus.

Two stone leek leafminer Liriomyza chinensis (Kato) (Diptera: Agromyzidae) biotypes (A and B) were reared using the Japanese bunching onion Allium fistulosum L. cultivar, ‘Kujou futo’ and subjected to competition under laboratory conditions. Both biotypes were reared in single and mixed cultures in varying proportions. The present study aimed to determine the reproductive behavior of the two L. chinensis biotypes under laboratory conditions of 24.5 °C and a photoperiod of 15 h light: 9 h darkness. Therefore, 12 adult flies, consisting of 3 males and females from each biotype, were reared in mixed cultures. The results indicated that biotype B had a significantly higher number of eggs and more emerged adults in the next generation than those of biotype A. The proportion of F₁ adults was 1.6%. In the second experiment, six males and females from the different biotypes were subjected to inter-biotype mating for 2 days without oviposition substrates. Subsequently, a mature female from each biotype was allowed to lay eggs on A. fistulosum fresh leaves. The results revealed that no larvae hatched from the eggs of both biotypes. The number of eggs per plant from both biotypes was standardized to determine larval competition. The number of eggs and egg survival rates of biotype B were higher than those of biotype A, indicating that under 24.5 °C and 15 h light: 9 h darkness conditions, biotype B outcompetes biotype A.

The broad mite, Polyphagotarsonemus latus (Banks) (Acari: Tarsonemidae), has been a devastating pest of several important agricultural and horticultural crops. Studies on the molecular mechanisms of adaptation to extrinsic conditions, e.g. acaricide exposure and temperature stress could aid in revealing the mite’s xenobiotic metabolism and quick adaptation to rapidly changing environments, respectively. This is best studied by the gene expression patterns, which could be accomplished through real-time quantitative reverse transcription PCR (qRT-PCR). Since real-time qRT-PCR studies require the selection of one or more reference genes whose expression patterns might vary across treatments, it is indispensable to validate their expression stability. In this study, the expression stability of six candidate reference genes viz., actin, elongation factor (EF-1α), glyceraldehyde-3-phosphate-dehydrogenase (GAPDH), ribosomal protein 49 (RP49), ribosomal protein S18 (RPS18) and β-tubulin (TUB) was investigated through real-time qRT-PCR experiments. By integrating the results of geNorm, NormFinder, BestKeeper, comparative ΔCt and RefFinder algorithms, RPS18/RP49 and EF-1α/RPS18 were identified as highly suitable reference genes for acaricide treatment and temperature stress treatments, respectively. RPS18 was recognized as the most suitable reference gene for both treatments which will ensure the accuracy of target gene expressions in studies related to xenobiotic metabolism and stress tolerance in P. latus.

Although classical biological controls aim to permanently minimize numbers of invasive pests using exotic natural enemies, few long-term studies have been conducted on this subject. In this study, we investigated the population dynamics of the chestnut gall wasp Dryocosmus kuriphilus Yasumatsu (Hymenoptera: Cynipidae), and an introduced parasitoid, Torymus sinensis Kamijo (Hymenoptera: Torymidae), over 40 years (1982–2023) at a site at which the parasitoid was first released (Tsukuba City, Ibaraki Prefecture) in Japan. Because the gall formation rate per 100 chestnut buds, an indicator of pest density, had decreased from 42.5 to 0.7% in the first 10 years after the release, the biocontrol program was deemed successful. However, further research showed fluctuations in the pest density over the next 30 years. It usually remained at low levels but occasionally increased dramatically, with three peaks exceeding the economic injury level (30%). Simultaneously, an indicator of parasitoid density (the number of parasitoids emerging from 100 galls × the gall formation rate) also fluctuated, in synchronization with the pest density indicator. These results suggest that T. sinensis has played an important role in suppressing D. kuriphilus at the releasing site over 40 years.

Hydrogel baits are composed of an insecticide and sugar water solution that is sustained by a super-absorbent polymer. This novel bait formulation has been increasingly used for controlling invasive ant species, as they prefer liquid foods and bait stations, which can be both costly and wasteful, are not required. Despite usage trends, the preference of invasive ants for hydrogel baits when compared with other food sources has not yet been widely demonstrated. This study evaluated the recruitment of the invasive Argentine ant Linepithema humile (Mayr) to various food sources, including hydrogel bait formulations containing sugar and insecticides (thiamethoxam, clothianidin), sugar water, tap water, a commercial paste-type fipronil bait, and a shrimp-flavored snack. The hydrogel baits and sugar water had equal recruitment levels for L. humile, irrespective of the sugar and insecticide concentrations (average 100–500 ants to approximately 4 × 4 cm placement). The recruitment levels for the hydrogel baits were also equal to or greater than those for the commercial paste bait (50–150 ants). However, overall, the shrimp-flavored snack was the food source with the highest levels of recruitment (500–800 ants). The results suggest that in the field, L. humile is moderately to highly interested in hydrogel baits. Hydrogel baits may not be the most efficient bait formulation for recruiting L. humile, but they are a powerful control option due to their advantages such as low cost, which enables thorough treatment. The addition of attractants could help to improve this method in the future.

The brown marmorated stink bug Halyomorpha halys (Stål) (Hemiptera: Pentatomidae) is an agricultural pest with a unique odor, aggregating near human habitats during the cold season. In the present study, we evaluated the suitability of H. halys as an edible insect. We observed that the one-time administration of 2000 mg/kg raw stink bugs to female rats via oral gavage did not affect their weight or cause mortality, suggesting that the medium lethal dose of H. halys adults was > 2000 mg/kg for female rats. Moreover, the presence of microorganisms or heavy metals was not observed in heated and raw insects, respectively, except for cadmium, suggesting that they met food hygiene and safety standards. Nutrient composition analysis revealed that the levels of useful compounds in H. halys were comparable to those in general hemipterans. The ratio of polyunsaturated fatty acids in H. halys adults was 44.3%, whereas that of saturated fatty acids was 16.8%. Moreover, H. halys was rich in β-carotene, astaxanthin, lutein, and zeaxanthin. Therefore, H. halys is a potential edible carotenoid source. Consumption of this insect would become a solution to managing the pest and nuisance. Further studies are needed to ensure food safety and human consumption.