Applied Entomology and Zoology最新文献

Insect growth is affected by various factors, and the elucidation of these factors is important from both basic and applied perspectives. This study examined the effects of temperature and diet on larval development of the endangered carabid beetle Pterostichus (Nialoe) isumiensis in laboratory rearing experiments. Three temperatures (10, 15, and 20 °C) and three diets (mealworms, dipteran larvae, and mealworms + dipteran larvae) were used in a 3 × 3 factorial design, and the survival rate and developmental duration of pre-overwintering stages (first and second instars) were compared. Survival was higher at lower temperatures, and the mealworm diet was associated with lower survival than other diets at lower temperatures. The developmental duration was shorter at high temperatures; at the same temperature, the mealworm diet was associated with a longer developmental duration. These results provide basic information useful for ex situ conservation of this endangered species, which may be required in future, and also inform several working hypotheses on the effects of temperature, diet, and their interaction on larval development in the Carabidae.

We examined the predation of two synanthropic jumping spiders, Hasarius adansoni (Araneae: Salticidae) and Plexippus paykulli (Araneae: Salticidae), on Tribolium castaneum (Herbst) (Coletptera: Tenebrionidae), a grain storage pest, that is sometimes found with these species to determine whether the predatory success of synanthropic and grassland jumping spiders on T. castaneum differs. We examined the predation of two synanthropic and three grassland jumping spiders on T. castaneum adults and larvae. We found that the two synanthropic species preyed on T. castaneum adults and larvae, while the three grassland species never attacked T. castaneum adults. The success or failure of predation on T. castaneum adults also depended on the body size of the jumping spiders.

The stinkbug Plautia stali develops a midgut symbiotic organ that harbors a specific bacterial symbiont indispensable for its growth and survival. Being maintainable in laboratory and tractable experimentally, P. stali is recently highlighted as a model system to investigate the mechanisms underpinning insect-microbe symbiotic interactions. In this study, we reared newly emerged adult insects of P. stali under different temperature conditions for 8 days and monitored how their symbiotic organs and symbiotic bacteria are affected. While all insects survived at temperatures from 25 to 37 °C, some insects died at 38 °C, 39 °C, and 40 °C, wherein mortality rates increased as temperature elevated. While the symbiotic organs of the normal insects exhibited vivid yellow color, the symbiotic organs of the insects reared at 35 °C or higher frequently exhibited abnormal colors, such as pale yellow, yellowish white, or white, the extent of which became more severe as temperature elevated. Symbiont quantification revealed that, while the symbiont titers were almost constant for 8 days at 25 °C and 30 °C, the symbiont titers on the 8th day drastically declined to 1/100 at 35 °C and 1/10000 at 37 °C and 39 °C. Based on these results, we propose that rearing at 37 °C for a week is a recommended treatment regime by which the symbiont is effectively suppressed with minimal damage to the host insect.

The small size and extensive polymorphisms of aphids make it difficult to identify larvae and adults solely based on their morphology. Here, we present an identification tool for the developmental stages of Acyrthosiphon pisum (Hemiptera: Aphididae) based on deep learning as a proof of concept. You Only Look Once (YOLO) algorithm is one of the most effective deep learning techniques for object detection. Although several studies have been conducted using deep learning technology for the detection and counting of tiny pests, the type of light source and size of the images were the limiting factors, as training was highly focused on uniform datasets and small insects. One way to overcome this problem is to introduce many types of datasets obtained from various light sources and microscopic magnifications. This strategy minimizes errors and omissions in aphid detection across all developmental stages in aphid individuals to the greatest extent possible. The experimental results showed that our modified YOLOv8 model could obtain over 95.9% and 99% accuracy for mean average precision (mAP) and recall, respectively, under various light sources, such as yellow, white, and natural light, and stereomicroscope magnifications. This study showed an improved accuracy of aphid recognition at all developmental stages. The study presents a novel deep learning model utilizing the YOLO algorithm to identify developmental stages of A. pisum. This model achieves high accuracy across various light sources and magnifications, thereby enhancing aphid biology studies.

Acrobasis nuxvorella Neuzing (Lepidoptera: Pyralidae) is a monophagous pest of Carya illinoinensis (Wangenh) K. Koch, a plant rich in tannins. When the tannins degrade, high concentrations of gallic acid are released, which are harmful to some insects. However, Acrobasis nuxvorella larvae are not affected by feeding on the plant when gallic acid is released. Therefore, it may be expected that Acrobasis nuxvorella larval gut microbiota may produce the enzyme laccase, enabling them to biotransform gallic acid into other useful molecules. Thus, the intestinal content of the insect was recovered. Among 175 bacterial isolates, 8 showed laccase activity in the range of 0.52–3.9 U/µg of protein. The isolates with laccase activity were identified as the Bacillus species: Bacillus pumilus, Bacillus safensis, Bacillus altitudinis, and Bacillus xiamenensis through 16S ribosomal RNA gene sequencing. In addition, the cotA gene coding for the laccase enzyme was found in the genomic DNA of these eight Bacillus isolates.

Entoria okinawaensis Shiraki, 1935 (Phasmatodea: Phasmatidae) is a stick insect originally distributed among the subtropical islands of Japan. This species, after introduction into the southernmost regions of Kyushu Island, became established there. After insects were collected for this study from Ibusuki city, Kagoshima prefecture, Japan, their eggs were used for experimentation. Embryonic development was fundamentally temperature dependent. At 25 °C, many eggs hatched approximately 2 months after oviposition. However, hatching was observed continuously until the end of the 240-day experiment. Findings from egg dissection suggest that a small number of eggs arrest development at the early embryonic stages. Fluorescence observation of DAPI-stained eggs reveals that eggs show arrested development at the very attenuated blastoderm period. This study proves the existence of embryonic diapause in E. okinawaensis, although the incidence of diapause eggs is small. If future changes in the incidence and duration of diapause as adaptations to local climate occur, then the domestic-introduced subtropical stick insect might expand its distribution range farther north.

Abstract

The challenge of dengue control due to the unavailability of a specific medication stresses the importance of releasing Wolbachia-carrying mosquitoes through vector control programs. This study investigated the sustainability and frequency of Wolbachia in Wolbachia-dengue-carrying mosquitoes in two dengue hotspot localities in Selangor. A modified sticky ovitrap was used to collect adult mosquitoes in two Wolbachia-releasing areas in Selangor, Kelana Puteri and Kelana D'Putera condominiums. All mosquito samples were subjected to PCR using wsp-specific primers for Wolbachia detection. Dengue virus was detected using RT-PCR, followed by multiplex-PCR. Out of the 80 Aedes spp. collected, Ae. aegypti was the most predominant species. More than one-third of Ae. aegypti were positive for Wolbachia, with 22.9% being superinfected with both Wolbachia A and B strains. About 61.4% of the species were uninfected with Wolbachia. Ae. aegypti carrying the Wolbachia A strain was also identified, which has previously never been reported. This strain was similar to the one found naturally in Ae. albopictus. None of the Ae. aegypti and Ae. albopictus were positive for dengue virus. This study could serve as a model for local researchers or health authorities to design and plan an effective field release and monitoring of Wolbachia-infected mosquitoes.

The sterile insect technique (SIT) is a pest control method that releases a large number of sterile pests into the field to inhibit mating between wild pests, ultimately resulting in the eradication of wild pest populations. It has often been discussed whether releasing one sex (mainly males) of sterile insects enhances the pest control efficiency of SIT compared to releasing both sexes (bisexual release). The control efficiency of sterile females may be negatively affected by their release, because sterile males lose the opportunity to mate with wild females. In this study, we investigated whether sterile females have a positive effect on the control efficiency of SIT and whether there is an additive or synergistic effect of releasing both sexes using two weevil species, Cylas formicarius and Euscepes postfasciatus, which are serious pests of the sweet potato Ipomoea batatas and targets of SIT in Okinawa. The results showed that in both species, the reproduction rate of wild pests was significantly suppressed in the case of the sterile female-only release. Interestingly, the most effective method varied between male-only and bisexual release depending on the density of sterile individuals and weevil species. Synergistic effects of both sexes on bisexual release were observed but varied with the density of sterile individuals and weevil species. High-density bisexual release was most effective for the SIT of at least two weevil species.

Subterranean termites primarily use decaying wood as both nest material and food, and the worker caste is responsible for searching for new wood. Because brown-rotted wood contains (Z,Z,E)-3,6,8-dodecatrien-1-ol, which is a trail pheromone component in Reticulitermes termites, it is considered that this compound attracts termite workers. However, while the trail pheromone allows passing workers to continue to move along it, it is unlikely to attract them from a distance. Therefore, workers should use other attractants derived from decaying wood as cues to locate it. In this study, we found that an aromatic abietane diterpenoid in termite culture medium made from brown-rotted Japanese red pine (Pinus densiflora) attracted workers of the Japanese subterranean termite Reticulitermes speratus (Kolbe) (Isoptera: Rhinotermitidae). Gas chromatography analyses and behavioral assays revealed that the n-hexane extract of the medium contains dehydroabietic acid, which is a resin component of various conifers, and this compound attracts workers. These results strongly suggest that R. speratus workers mainly use this compound as a cue to locate brown-rotted pinewood in nature. Our study contributes to the understanding of the mechanisms of wood detection in termites.