Air-Fluidized Aggregates of Black Soldier fly Larvae

Black soldier fly larvae are a sustainable protein source and play a vital role in the emerging food-waste recycling industry. One of the challenges of raising larvae in dense aggregations is their rise in temperature during feeding, which, if not mitigated, can become lethal to the larvae. We propose applying air-fluidization to circumvent such overheating. However, the behavior of such a system involves complex air-larva interactions and is poorly understood. In this combined experimental and numerical study, we show that the larval activity changes the behavior of the ensemble when compared to passive particles such as dead larvae. Over a cycle of increasing and then decreasing airflow, the states (pressure and height) of the live larva aggregates are single-value functions of the flow speed. In contrast, dead larva aggregates exhibit hysteresis characteristic of traditional fluidized beds, becoming more porous during the ramp down of airflow. This history-dependence for passive particles is supported by simulations that couple agent-based dynamics and computational fluid dynamics. We show that the hysteresis in height and pressure of the aggregates decreases as the activity of simulated larvae increases. To test if air fluidization can increase larval food intake, we performed feeding trials in a fluidization chamber and visualized the food consumption via x-ray imaging. Although the food mixes more rapidly in faster airflow, the consumption rate decreases. Our findings suggest that providing moderate airflow to larval aggregations may alleviate overheating of larval aggregations and evenly distribute the food without reducing feeding rates.

Gregarines modulate insect responses to sublethal insecticide residues

Throughout their lifetime, insects face multiple environmental challenges that influence their performance. Gregarines are prevalent endoparasites in most invertebrates that affect the fitness of their hosts, but are often overlooked in ecological studies. Next to such biotic factors, a current common challenge is anthropogenic pollution with pesticides, which causes a major threat to non-target organisms that are readily exposed to lethal or sublethal concentrations. In a laboratory study, we investigated whether the presence of gregarines modulates the food consumption and life history traits of a (non-target) leaf beetle species, Phaedon cochleariae, in response to sublethal insecticide exposure. We show that the larval food consumption of the herbivore was neither affected by gregarine infection nor sublethal insecticide exposure. Nevertheless, infection with gregarines led to a delayed development, while insecticide exposure resulted in a lower body mass of adult males and a reduced reproduction of females. Individuals exposed to both challenges suffered most, as they had the lowest survival probability. This indicates detrimental effects on the population dynamics of non-target insects infected with naturally occurring gregarines that face additional stress from agrochemical pollution. Moreover, we found that the infection load with gregarines was higher in individuals exposed to sublethal insecticide concentrations compared to unexposed individuals. To counteract the global decline of insects, the potential of natural parasite infections in modulating insect responses to anthropogenic and non-anthropogenic environmental factors should be considered in ecological risk assessment.

Effect of Larval Food Amount on in vitro Rearing of Indo-Malayan Stingless Bee Queen, Heterotrigona itama (Hymenoptera: Apidae; Meliponini)

The demand for stingless bee colonies in Malaysia has considerably increased due to the rapid advance of meliponiculture in using the stingless bees as agricultural pollinators, as well as the commercialization of stingless bee products (i.e. honey, bee bread and propolis). Thus, in vitro queen rearing for a large scale and rapid colony multiplication must be developed in order to fulfil the public requirements in a short period. Little is known about the in vitro rearing of native stingless bee queen, Heterotrigona itama. Therefore, in this study, we investigated the amount of larval food required by H. itama queen by comparing three different amounts of larval food, viz., 100 µL, 120 µL and 150 µL. All treatments were controlled under 100% relative humidity for the first 6 days, and 75% relative humidity for the rest of larval development until queen adult emergence, under 30 °C incubator temperature. The results showed that larvae of H. itama treated with the highest amount of larval food (150 µL) led to 78% of the queen’s emergence, whereas larvae treated with 120 µL and 100 µL of larval food resulted in 40% and 0% of queen emergence. The dynamic survival curve showed that most of the larvae died before the pupation phase and reached constant stability afterward. The queen’s body and abdominal length were significantly greater than wild workers. Microscopy analysis showed that in vitro queen had well-developed reproductive system with a huge ovary and spermatheca, whereas wild worker had much smaller ovary without spermatheca. Outcomes from this study could help increase the number of colonies on a large scale, allowing for their use both ecologically and economically, and contribute to conservation efforts in native species of stingless bees.

Metagenomic Survey of the Highly Polyphagous Anastrepha ludens Developing in Ancestral and Exotic Hosts Reveals the Lack of a Stable Microbiota in Larvae and the Strong Influence of Metamorphosis on Adult Gut Microbiota

We studied the microbiota of a highly polyphagous insect, Anastrepha ludens (Diptera: Tephritidae), developing in six of its hosts, including two ancestral (Casimiroa edulis and C. greggii), three exotic (Mangifera indica cv. Ataulfo, Prunus persica cv. Criollo, and Citrus x aurantium) and one occasional host (Capsicum pubescens cv. Manzano), that is only used when extreme drought conditions limit fruiting by the common hosts. One of the exotic hosts (“criollo” peach) is rife with polyphenols and the occasional host with capsaicinoids exerting high fitness costs on the larvae. We pursued the following questions: (1) How is the microbial composition of the larval food related to the composition of the larval and adult microbiota, and what does this tell us about transience and stability of this species’ gut microbiota? (2) How does metamorphosis affect the adult microbiota? We surveyed the microbiota of the pulp of each host fruit, as well as the gut microbiota of larvae and adult flies and found that the gut of A. ludens larvae lacks a stable microbiota, since it was invariably associated with the composition of the pulp microbiota of the host plant species studied and was also different from the microbiota of adult flies indicating that metamorphosis filters out much of the microbiota present in larvae. The microbiota of adult males and females was similar between them, independent of host plant and was dominated by bacteria within the Enterobacteriaceae. We found that in the case of the “toxic” occasional host C. pubescens the microbiota is enriched in potentially deleterious genera that were much less abundant in the other hosts. In contrast, the pulp of the ancestral host C. edulis is enriched in several bacterial groups that can be beneficial for larval development. We also report for the first time the presence of bacteria within the Arcobacteraceae family in the gut microbiota of A. ludens stemming from C. edulis. Based on our findings, we conclude that changes in the food-associated microbiota dictate major changes in the larval microbiota, suggesting that most larval gut microbiota is originated from the food.

Distribution, phenology, and land cover preference risk assessments of four South-Central US milkweeds (Asclepias spp.) important for monarch butterflies

South-Central US milkweeds (Asclepias spp.) are critical adult nectar and larval food resources for producing the first spring and last summer/fall generations of declining eastern migratory monarch butterflies (Danaus plexippus). MaxEnt niche models were developed for North American ranges of four important South-Central US milkweeds: Asclepias asperula ssp. capricornu, A. viridis, A. oenotheroides, and A. latifolia. Twelve models per species utilized subsets of six to eight of 95 edapho-topo-climatic variables chosen by a random subset feature selection algorithm. Milkweed weekly phenology was compared between early and late season periods of monarch activity. Novel land cover preference risk assessments were developed for milkweeds through land cover utilization-availability analyses, incorporating a novel sample bias reduction method for citizen science data before calculation of relativized electivity index (E*) land cover preference. Asclepias a. ssp. capricornu and A. viridis occurred more frequently during early season monarch activity, while A. oenotheroides and A. latifolia occurred more frequently during late season monarch activity. Milkweed utilization of roadsides varied from 6–31%. Developed-Open Space and Grassland Herbaceous land classes generally had highest benefit among milkweeds. Cultivated Crops and Shrub/Scrub had high risk. Combined milkweed high Ei* kernel density estimation surfaces resolved interior and coastal corridors of milkweed land cover preference providing functional connectivity for the monarch spring and fall migrations. A potentially critical gap in milkweed land cover benefit connectivity was identified in South Texas. Milkweed land cover preference risk assessments can be used to prioritize milkweed habitat conservation for enhancing monarch migration connectivity across the South-Central US.

Two new species of Gelechiidae (Lepidoptera) from Korea, with some biological data including larval host plants

In this study, two new species of the family Gelechiidae are described from Korea. The new species are Teleiodes juglansivora Park & Byun, sp. nov. and Encoplata najuensis Park & Byun, sp. nov. For the new species, some biological data concerning on their larval food plants are given.

Larval Diet Abundance Influences Size and Composition of the Midgut Microbiota of Aedes aegypti Mosquitoes

The midgut microbiota of the yellow fever mosquito Aedes aegypti impacts pathogen susceptibility and transmission by this important vector species. However, factors influencing the composition and size of the microbiome in mosquitoes are poorly understood. We investigated the impact of larval diet abundance during development on the composition and size of the larval and adult microbiota by rearing Aedes aegypti under four larval food regimens, ranging from nutrient deprivation to nutrient excess. We assessed the persistent impacts of larval diet availability on the microbiota of the larval breeding water, larval mosquitoes, and adult mosquitoes under sugar and blood fed conditions using qPCR and high-throughput 16S amplicon sequencing to determine bacterial load and microbiota composition. Bacterial loads in breeding water increased with increasing larval diet. Larvae reared with the lowest diet abundance had significantly fewer bacteria than larvae from two higher diet treatments, but not from the highest diet abundance. Adults from the lowest diet abundance treatment had significantly fewer bacteria in their midguts compared to all higher diet abundance treatments. Larval diet amount also had a significant impact on microbiota composition, primarily within larval breeding water and larvae. Increasing diet correlated with increased relative levels of Enterobacteriaceae and Flavobacteriaceae and decreased relative levels of Sphingomonadaceae. Multiple individual OTUs were significantly impacted by diet including one mapping to the genus Cedecea, which increased with higher diet amounts. This was consistent across all sample types, including sugar fed and blood fed adults. Taken together, these data suggest that availability of diet during development can cause lasting shifts in the size and composition of the microbiota in the disease vector Aedes aegypti.

10-hydroxy-2E-decenoic acid (10HDA) does not promote caste differentiation in Melipona scutellaris stingless bees

In bees from genus Melipona, differential feeding is not enough to fully explain female polyphenism. In these bees, there is a hypothesis that in addition to the environmental component (food), a genetic component is also involved in caste differentiation. This mechanism has not yet been fully elucidated and may involve epigenetic and metabolic regulation. Here, we verified that the genes encoding histone deacetylases HDAC1 and HDAC4 and histone acetyltransferase KAT2A were expressed at all stages of Melipona scutellaris, with fluctuations between developmental stages and castes. In larvae, the HDAC genes showed the same profile of Juvenile Hormone titers—previous reported—whereas the HAT gene exhibited the opposite profile. We also investigated the larvae and larval food metabolomes, but we did not identify the putative queen-fate inducing compounds, geraniol and 10-hydroxy-2E-decenoic acid (10HDA). Finally, we demonstrated that the histone deacetylase inhibitor 10HDA—the major lipid component of royal jelly and hence a putative regulator of honeybee caste differentiation—was unable to promote differentiation in queens in Melipona scutellaris. Our results suggest that epigenetic and hormonal regulations may act synergistically to drive caste differentiation in Melipona and that 10HDA is not a caste-differentiation factor in Melipona scutellaris.