Functional response in coccinellid beetles (Coleoptera: Coccinellidae) is modified by prey-density experience

In the present study, we assessed functional response curves of two generalist coccinellid beetles (Coleoptera: Coccinellidae), specifically Menochilus sexmaculatus and Propylea dissecta, using fluctuating densities of aphid prey as a stimulus. In what may be the first such study, we investigated how the prey density experienced during the early larval development of these two predatory beetle species shaped the functional response curves of the late instar–larval and adult stages. The predators were switched from their rearing prey-density environments of scarce, optimal, or abundant prey to five testing density environments of extremely scarce, scarce, suboptimal, optimal, or abundant prey. The individuals of M. sexmaculatus that were reared on either scarce- and optimal- or abundant-prey densities exhibited type II functional response curves as both larvae and adults. However, individuals of P. dissecta that were reared on scarce- and abundant-prey densities displayed modified type II functional response curves as larvae and type II functional response curves as adults. In contrast, individuals of P. dissecta reared on the optimal-prey density displayed type II functional response curves as larvae and modified type II functional response curves as adults. The fourth-instar larvae and adult females of M. sexmaculatus and P. dissecta also exhibited highest prey consumption (T/Th) and shortest prey-handling time (Th) on the scarce-prey rearing density. Thus, under fluctuating-prey conditions, M. sexmaculatus is a better biological control agent of aphids than P. dissecta is.

How Filipino Fishers Use Traditional Knowledge in Identifying Species of Juvenile Mangrove Crabs for Grow-out Culture

Mangrove crab growers in the Philippines still rely on wild-caught late instar to early juvenile mangrove crablets, as supplies from hatcheries are limited. Any batch of crablets caught from the wild is a mix of the three native species under the genus Scylla. Scylla species have different growth rates. Since grow-out culture depends heavily on species' growth, growers should be able to distinguish the species as early as the juvenile stage, which is taxonomically difficult. This study was done to consolidate low-cost traditional identification techniques for juvenile Scylla from fishers of the Philippines for future validation. Focused group discussions were done in fishing communities from Bataan, Pangasinan, and Cagayan on the island of Luzon. The study was continued through online surveys, as travel was restricted due to the Covid-19 pandemic. Results indicate that 70.58% of respondents identify the species of crabs by looking at their claws and 55.88% observe the color of the crabs. Almost half, or 41.17% of respondents, consider the width and size of the carapace. Unique methods in certain Philippine regions include observation of the behavior patterns, carapace texture, rate of weight gain, and seasonality. Validation of the traditional practices identified in this study would result in a reliable "at-a-glance" method of identifying juvenile Scylla in the Philippines, which would shorten the culture period, improve production gains, and manage local populations.

Microbiota Variation Across Life Stages of European Field-Caught Anopheles atroparvus and During Laboratory Colonization: New Insights for Malaria Research

The potential use of bacteria for developing novel vector control approaches has awakened new interests in the study of the microbiota associated with vector species. To set a baseline for future malaria research, a high-throughput sequencing of the bacterial 16S ribosomal gene V3-V4 region was used to profile the microbiota associated with late-instar larvae, newly emerged females, and wild-caught females of a sylvan Anopheles atroparvus population from a former malaria transmission area of Spain. Field-acquired microbiota was then assessed in non-blood-fed laboratory-reared females from the second, sixth, and 10th generations. Diversity analyses revealed that bacterial communities varied and clustered differently according to origin with sylvan larvae and newly emerged females distributing closer to laboratory-reared females than to their field counterparts. Inter-sample variation was mostly observed throughout the different developmental stages in the sylvan population. Larvae harbored the most diverse bacterial communities; wild-caught females, the poorest. In the transition from the sylvan environment to the first time point of laboratory breeding, a significant increase in diversity was observed, although this did decline under laboratory conditions. Despite diversity differences between wild-caught and laboratory-reared females, a substantial fraction of the bacterial communities was transferred through transstadial transmission and these persisted over 10 laboratory generations. Differentially abundant bacteria were mostly identified between breeding water and late-instar larvae, and in the transition from wild-caught to laboratory-reared females from the second generation. Our findings confirmed the key role of the breeding environment in shaping the microbiota of An. atroparvus. Gram-negative bacteria governed the microbiota of An. atroparvus with the prevalence of proteobacteria. Pantoea, Thorsellia, Serratia, Asaia, and Pseudomonas dominating the microbiota associated with wild-caught females, with the latter two governing the communities of laboratory-reared females. A core microbiota was identified with Pseudomonas and Serratia being the most abundant core genera shared by all sylvan and laboratory specimens. Overall, understanding the microbiota composition of An. atroparvus and how this varies throughout the mosquito life cycle and laboratory colonization paves the way when selecting potential bacterial candidates for use in microbiota-based intervention strategies against mosquito vectors, thereby improving our knowledge of laboratory-reared An. atroparvus mosquitoes for research purposes.

Efficacy of Two Neonicotinoid Insecticides against Invasive Wood Borer Aromia bungii Larvae in Dietary Toxicity Test

In recent years, insecticide trunk injection was put into practical use for controlling wood boring pests. However, few studies have investigated the dose–response relationships between insecticides and wood–boring pests in detail. This study used two commercial formulations of the neonicotinoid insecticides thiamethoxam and dinotefuran and investigated their dose–response relationships with invasive wood borer Aromia bungii (Coleoptera: Cerambycidae) larvae. Neonates and late instar larvae were reared with an artificial diet containing different insecticide concentrations (0.01–100 ppm) in the laboratory, and their diet excavation activity, survival rate, and weight change were recorded. Diet excavation immediately dropped in larvae exposed to high concentrations of thiamethoxam or dinotefuran (≥1 ppm in neonates and ≥10 ppm in late instar larvae). The weight and survival rate gradually declined over 12 weeks in late instar larvae. These results suggest that the two neonicotinoids intoxicate and debilitate A. bungii larvae gradually to death. In practical use, rapid suppression of A. bungii wood boring damage can be expected by trunk injection of neonicotinoid insecticides. However, a relatively long-term retention of the insecticides may be required to kill large larvae. Neonates may be controlled with lower insecticide dosage and shorter exposure than larger larvae.

16S rRNA Amplicon Sequencing of Bagworm Metisa plana Walker (Lepidoptera: Psychidae)

The bagworm Metisa plana is one of the major pests in the oil palm plantation in Malaysia, with infestation that results in huge economical loss. Currently, the exact cause of the infestation is still undetermined. Studying the bacterial community of M. plana could provide insight on the problem as the bacteria associated with insects often provide numerous benefits to the insect itself. Using 16S rRNA amplicon sequencing, the study was conducted to compare the composition of the bacterial communities of two larval stages (early instar stage and late instar stage) from outbreak area, as well as comparing the late instar stage larvae from non-outbreak and outbreak areas. Generally, the bacterial community was dominated by Proteobacteria and Actinobacteria phyla while the Enterobacteriaceae was found to be the dominant family. When comparing between the early and late instar stage, Proteobacteria phylum was found to be more abundant in the late instar stage (82.36%) than in the early instar stage (82.28%). At the family level, the Enterobacteriaceae was slightly more abundant in late instar stage (75.46%) than in early instar stage (75.29%). The instar stage was observed to have no significant impact on the bacterial variability and showed similar bacterial community structure. When comparing between the non-outbreak area and outbreak, Proteobacteria was significantly more abundant in the outbreak area (82.02%) than in the non-outbreak area (20.57%). However, Actinobacteria was significantly more abundant in the non-outbreak area (76.29%) than in the outbreak area (14.16%). At the family level, Enterobacteriaceae was more abundant in outbreak area (75.41%) than in non-outbreak area (11.67%). Microbacteriaceae was observed to be more abundant in the non-outbreak area (70.87%) than in the outbreak area (12.47%). Although the result showed no significant difference in bacterial variability between different areas, it the bacterial community structure was significantly different.

Developmental and reproductive effects of clothianidin exposure in monarch butterflies (Lepidoptera: Nymphalidae)

Neonicotinoid insecticides are used to reduce crop damage caused by insect pests, but sublethal levels could affect development and reproduction in nontarget insects, such as monarch butterflies (Danaus plexippus) (Lepidoptera: Nymphalidae). To investigate the impact of field-realistic concentrations of the neonicotinoid clothianidin on monarch butterflies, we grew swamp milkweed (Asclepias incarnata) (Apocynaceae) in either low (15 ng/g of soil) or high (25 ng/g of soil) levels of clothianidin, or in a control (0 ng/g), then raised monarchs on the milkweed. Morphological traits of monarch caterpillars were measured during development and, once they eclosed, were mated as adults to quantify egg size and mass and the number of eggs laid. Although the effects of the treatment had complex effects on caterpillar length, width and volume of late-instar caterpillars were negatively affected. Fifth-instar caterpillars from the high-dose insecticide treatment had lower mass than other groups. Adult monarch butterflies raised on treated milkweed were larger than controls, but clothianidin exposure did not affect the number of eggs laid or egg size. Although the magnitude of the effect depends on clothianidin concentration, our results suggest that exposure to clothianidin during early life can impact monarch caterpillar development but is unlikely to reduce female reproductive output.

Dietary zinc enrichment reduces the cadmium burden of mealworm beetle (Tenebrio molitor) larvae

The industrial production of Tenebrio molitor L. requires optimized rearing and processing conditions to generate insect biomass with high nutritional value in large quantities. One of the problems arising from processing is a tremendous loss in mineral accessibility, affecting, amongst others, the essential trace element Zn. As a feasible strategy this study investigates Zn-enrichment of mealworms during rearing to meet the nutritional requirements for humans and animals. Following feeding ZnSO4-spiked wheat bran substrates late instar mealworm larvae were evaluated for essential micronutrients and human/animal toxic elements. In addition, growth rate and viability were assessed to select optimal conditions for future mass-rearing. Zn-feeding dose-dependently raised the total Zn content, yet the Znlarvae/Znwheat bran ratio decreased inversely related to its concentration, indicating an active Zn homeostasis within the mealworms. The Cu status remained stable, suggesting that, in contrast to mammals, the intestinal Cu absorption in mealworm larvae is not affected by Zn. Zn biofortification led to a moderate Fe and Mn reduction in mealworms, a problem that certainly can be overcome by Fe/Mn co-supplementation during rearing. Most importantly, Zn feeding massively reduced the levels of the human/animal toxicant Cd within the mealworm larvae, a technological novelty of outstanding importance to be implemented in the future production process to ensure the consumer safety of this edible insect species.

Observations on co-existing late-instar caterpillars of the Orange-tip butterfly, Anthocharis cardamines (Linnaeus) (Lepidoptera: Pieridae)

Co-existence between late instar larvae of Anthocharis cardamines on multiple occupied Lunaria annua plants was monitored in a suburban Edinburgh garden and a stand-off between final instar larvae on Sisymbrium officinale in countryside near Leipzig was recorded photographically. Occupation of mauve-flowered Lunaria plants was significantly higher than white-flowered ones. The notion that the resting behaviour of final instar larva along the top of seed pods camouflages them is challenged. Although not part of that argument, a major predation event by Vespula vulgaris was seen on Lunaria.

Larval description of Limnephilus atlanticus Nybom 1948, morphological comparison with Limnephilus affinis Curtis 1834, (Trichoptera: Limnephilidae) and additional notes on their ecology in Azores Islands

This study presents the first morphological description and illustration of the late instar larva of Limnephilus atlanticus Nybom 1948, an endemic caddisfly from the Azores. Taxonomic comparisons with a recently recorded limnephilid species, Limnephilus affinis (Limnephilidae), and notes of their ecology and distribution in the Azores are also provided.

Larvicidal Activity of Inorganic Salts Against Anopheles Stephensi and Culex Quinquefasciatus

Mosquitoes transmit serious human diseases, causing millions of deaths worldwide every year and the development of resistance to chemical insecticides resulting in rebounding vectorial capacity. In this study, the larvicidal bioassays for activities of aqueous solutions of weak acid [(NH4)2SO4 and NaH2PO4] and weak base (Na2CO3 and NaHCO3) inorganic salts against late instar larvae of disease vectors Anopheles stephensi and Culex quinquefasciatus were carried out under laboratory settings. The four inorganic salts showed varied levels of larvicidal activities after 24 h-exposure on Anopheles stephensi and Culex quinquefasciatus larvae in a dose-dependent fashion. However, the larvicidal activities were relatively higher in Na2CO3 (LC50 = 3162 and 447 ppm) and NaHCO3 (LC50 = 5623 and 398 ppm) solutions as compared to those in (NH4)2SO4 (LC50 = 7943 and 1995 ppm) and NaH2PO4 (LC50 = 7943 and 7120 ppm). The present study showed that the inorganic salts Na2CO3, NaHCO3, (NH4)2SO4 and NaH2PO4 could serve as potential larviciding agents considering their low toxicity. Therefore, this study provides a first report on the larvicidal activity of the inorganic salts on mosquito larvae of disease vectors.