Use of different dry materials to control the moisture in a black soldier fly (Hermetia illucens) rearing substrate.

Background: Controlling the substrate moisture is a significant challenge in black soldier fly (BSF) farming. Many substrates have a high moisture content, which results in a low BSF biomass and a high mortality. One potential solution involves incorporating dry substrates into the food mix to mitigate the excessive moisture. However, little information about the types and quantities of dry substrates is available. Methods: Six different dry materials-rice husk (RH), rice bran (RB), rice husk ash (RHA), coconut coir dust (CC), rubberwood sawdust (RSD), and spent coffee grounds (SCGs)-were evaluated by combining with pure minced mixed vegetables in varying proportions (0%, 5%, 10%, 15%, 25%, and 50% by weight). This study encompassed both small-scale and medium-scale experiments to comprehensively assess the effects of the addition of each of these different dry substrates and their quantities on aspects of the development of BSF, such as BSF biomass, larval duration, mortality rates, adult sex ratio, and the moisture removal efficiency of each substrate mixture. Results: Each dry substrate had specific properties. Although RB emerged as a favorable dry substrate owing to its nutritional content and substantial water-holding capacity, excessive use of RB (>15% by weight) resulted in elevated temperatures and subsequent desiccation of the substrate, potentially leading to larval mortality. In contrast, RH demonstrated the ability to support improved larval duration and growth, permitting its utilization in higher proportions (up to 50%). On the other hand, CC, RHA, and SCG are better suited for inclusion in BSF larval substrates in smaller quantities. Discussion: Some dry substrates require a pretreatment process to eliminate toxic substances prior to their incorporation into substrate mixtures, such as CC and SCG. A potential alternative solution involves employing a combination of various dry substrates. This approach aims to enhance the substrate moisture control and subsequently improve the BSF rearing performance.

Behavioral responses of different reproductive statuses and sexes in Hermetia illucens (L) adults to different attractants.

Background: The odor of various fermented organic materials acts as an attractant for oviposition by gravid females of the black soldier fly (BSF) to find larval food sources. Females display oviposition site selection on various organic materials, but little work has been done on the response to substrate attractants under caged conditions similar to those in a BSF farm production system. Methods: Fifty of each reproductive status (mated and virgin) and sex (males and females) of BSF adults were marked and then exposed to one of five different oviposition attractants in a transparent acrylic chamber: no substrate (control) plus pineapple, mixed vegetables, okara, and fermented fish to represent fruit-, vegetable-, plant protein-, and animal protein-based substrates, respectively. The frequency of the perching activity on the oviposition apparatus and flying behavior under the LED illumination, including the laid egg weight, were recorded. Results: The sexually-related activities of BSF adults were clearly observed. A majority of the females preferred to perch on the oviposition apparatus and fly around the illuminated area compared to the very low activities of the mated males. The BSF adults displayed different behavioral responses to the different tested attractants. While active flying was common when using plant protein- and animal protein-based substrates, mated females showed the greatest perching preference for plant-based substrates (fruit and vegetables) and this correlated with the laid egg weight. Discussion: Egg-laying was more likely to happen on the plant-based substrate than on the animal protein-based substrate. However, the strong smell of the animal protein-based substrate could strongly trigger lekking behavior, which is an important part of mating behavior. This knowledge can support egg trapping in nature and also improve the efficiency of egg production in mass-rearing facilities.

Use of fermented spent coffee grounds as a substrate supplement for rearing black soldier fly larvae, Hermetia illucens (L), (Diptera: Stratiomyidae).

Background: Spent coffee grounds (SCG), an increasingly abundant waste product with environmental disposal problems, has been used as a dietary supplement for many animals and have the potential to be used as a dietary supplement for black soldier fly (BSF) larvae; however, its effective use is still under scrutiny. To date, no studies have considered the use of SCG after microbial fermentation (fSCG) and its effects on BSF life history. Methods: A mixture of fruit and vegetable pulp residue supplemented with one of six different fSCG percentages (0%, 20%, 40%, 60%, 80%, and 100% by weight) were provided as a diet substrate in order to evaluate the effect of the fSCG quantity on BSF growth, yield, and conversion ability. Results: The addition of fSCG to the pulp diet prolonged larval development times, while 100% fSCG affected the larval survival rate and resulted in a male-biased adult sex ratio. The 20-40% fSCG and 40-60% fSCG treatments supported the largest prepupal and mature larval sizes, respectively. The highest waste reduction efficiency and feed conversion rate by BSF larvae was found with 20% fSCG, similar to the control (0% fSCG). Discussion: From the short rearing time, high yield, and high bioconversion efficiency, a 20% fSCG supplementation of the mixed pulp was recommended for rearing BSF larvae. These data are valuable for coffee by-product waste management in urban areas.

Identification of potential candidate genes involved in the sex determination cascade in an aquatic firefly, Sclerotia aquatilis (Coleoptera, Lampyridae).

Sexual differentiation, dimorphism, and courtship behavior are the downstream developmental programs of the sex determination cascade. The sex determination cascade in arthropods often involves key genes, transformer (tra), doublesex (dsx), transformer-2 (tra2), and fruitless (fru). These genes are conserved among insect taxa; however, they have never been reported in fireflies. In this study, the candidate genes for these key genes were identified for the first time in an aquatic firefly, Sclerotia aquatilis using transcriptome analysis. A comparative protein-protein interaction (PPI) network of sex determination cascade was reconstructed for S. aquatilis based on a network of a model insect, Drosophila melanogaster. Subsequently, a sex determination cascade in S. aquatilis was proposed based on the amino acid sequence structures and expression profiles of these candidates. This study describes the first efforts toward understanding the molecular control of sex determination cascade in fireflies.

Reconstruction of insect hormone pathways in an aquatic firefly, Sclerotia aquatilis (Coleoptera: Lampyridae), using RNA-seq.

Insect hormones: ecdysteroids and juvenile hormones have crucial functions during the regulation of different developmental pathways in insects. Insect metamorphosis is one of the primary pathways regulated by these hormones. The insect hormone biosynthetic pathway is conserved among arthropods, including insects, with some variations in the form of hormones used among each group of insects. In this study, the candidate genes involved in the insect hormone pathways and their functional roles were assessed in an aquatic firefly, Sclerotia aquatilis using a high-throughput RNA sequencing technique. Illumina next-generation sequencing (NGS) was used to generate transcriptome data for the different developmental stages (i.e., larva, pupa, and adult) of S. aquatilis. A total of 82,022 unigenes were generated across all different developmental stages. Functional annotation was performed for each gene, based on multiple biological databases, generating 46,230 unigenes. These unigenes were subsequently mapped using KEGG pathways. Accordingly, 221 protein-encoding genes involved in the insect hormone pathways were identified, including, JHAMT, CYP15A1, JHE, and Halloween family genes. Twenty potential gene candidates associated with the biosynthetic and degradation pathways for insect hormones were subjected to real-time PCR, reverse transcriptase PCR (RT-PCR) and sequencing analyses. The real-time PCR results showed similar expression patterns as those observed for transcriptome expression profiles for most of the examined genes. RT-PCR and Sanger sequencing confirmed the expressed coding sequences of these gene candidates. This study is the first to examine firefly insect hormone pathways, facilitating a better understanding of firefly growth and development.

Continental-scale suppression of an invasive pest by a host-specific parasitoid underlines both environmental and economic benefits of arthropod biological control.

Biological control, a globally-important ecosystem service, can provide long-term and broad-scale suppression of invasive pests, weeds and pathogens in natural, urban and agricultural environments. Following (few) historic cases that led to sizeable environmental up-sets, the discipline of arthropod biological control has-over the past decades-evolved and matured. Now, by deliberately taking into account the ecological risks associated with the planned introduction of insect natural enemies, immense environmental and societal benefits can be gained. In this study, we document and analyze a successful case of biological control against the cassava mealybug, Phenacoccus manihoti (Hemiptera: Pseudococcidae) which invaded Southeast Asia in 2008, where it caused substantial crop losses and triggered two- to three-fold surges in agricultural commodity prices. In 2009, the host-specific parasitoid Anagyrus lopezi (Hymenoptera: Encyrtidae) was released in Thailand and subsequently introduced into neighboring Asian countries. Drawing upon continental-scale insect surveys, multi-year population studies and (field-level) experimental assays, we show how A. lopezi attained intermediate to high parasitism rates across diverse agro-ecological contexts. Driving mealybug populations below non-damaging levels over a broad geographical area, A. lopezi allowed yield recoveries up to 10.0 t/ha and provided biological control services worth several hundred dollars per ha (at local farm-gate prices) in Asia's four-million ha cassava crop. Our work provides lessons to invasion science and crop protection worldwide. Furthermore, it accentuates the importance of scientifically-guided biological control for insect pest management, and highlights its potentially large socio-economic benefits to agricultural sustainability in the face of a debilitating invasive pest. In times of unrelenting insect invasions, surging pesticide use and accelerating biodiversity loss across the globe, this study demonstrates how biological control-as a pure public good endeavor-constitutes a powerful, cost-effective and environmentally-responsible solution for invasive species mitigation.

Further studies on south eastern Asian Luciolinae: 1. Sclerotia Ballantyne, a new genus of fireflies with back swimming larvae 2. Triangulara Pimpasalee, a new genus from Thailand (Coleoptera: Lampyridae).

Sclerotia Ballantyne gen. nov. is established for seven species. Sclerotia aquatilis (Thancharoen, 2007), Scl. brahmina (Bourgeois, 1890), Scl. carinata (Gorham, 1880), Scl. flavida (Hope, 1845), Scl. seriata (Olivier, 1891), and Scl. substriata (Gorham, 1880) are transferred from Luciola Laporte. Sclerotia fui sp. nov. from China is described as new. Luciola cingulata Olivier, 1885 is synonymised with Luciola substriata Gorham. Luciola formosana Pic, 1916 is removed from synonymy with Luciola substriata and newly synonymised with Luciola flavida (Hope). Males are characterised by linear elytral punctation, a set of three sclerites surrounding the aedeagal sheath and a light organ in ventrite 7 with emarginated anterior margin. Associated females lack bursa plates. Larvae associated for three species are back swimmers, having heavily sclerotised exoskeleton and a metapneustic respiratory system. Males and associated females are keyed. Analysis of molecular evidence for Chinese populations of three species indicates monophyly of Sclerotia Ballantyne gen. nov. and distinct separation from other genera.Triangulara Pimpasalee gen. nov. is described from Tri. frontoflava Pimpasalee gen. et sp. nov. from Thailand. It is superficially similar to Sclerotia gen. nov. but larger, and specimens in collections appear to have been confused with the similarly coloured Scl. substriata (Gorham) comb. nov. Males differ in having an elongate triangular light organ in ventrite 7 and are without sclerites around the aedeagal sheath. Larvae are not reliably associated but may be aquatic.

TiLIA: a software package for image analysis of firefly flash patterns.

As flash signaling patterns of fireflies are species specific, signal-pattern analysis is important for understanding this system of communication. Here, we present time-lapse image analysis (TiLIA), a free open-source software package for signal and flight pattern analyses of fireflies that uses video-recorded image data. TiLIA enables flight path tracing of individual fireflies and provides frame-by-frame coordinates and light intensity data. As an example of TiLIA capabilities, we demonstrate flash pattern analysis of the fireflies Luciola cruciata and L. lateralis during courtship behavior.