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The genus Anastatus comprises a large group of parasitoids, including several biological control agents in agricultural and forest systems. The taxonomy and phylogeny of these species remain controversial. In this study, the mitogenome of A. fulloi Sheng and Wang was sequenced and characterized. The nearly full-length mitogenome of A. fulloi was 15,692 bp, compromising 13 protein-coding genes (PCGs), 2 rRNA genes, 22 tRNA genes and a control region (CR). The total A + T contents were 83.83%, 82.18%, 87.58%, 87.27%, and 82.13% in the whole mitogenome, 13 PCGs, 22 tRNA genes, 2 rRNA genes, and CR, respectively. The mitogenome presented negative AT skews and positive GC skews, except for the CR. Most PCGs were encoded on the heavy strand, started with ATN codons, and ended with TAA codons. Among the 3736 amino acid-encoding codons, TTA (Leu1), CGA (Arg), TCA (Ser2), and TCT (Ser2) were predominant. Most tRNAs had cloverleaf secondary structures, except trnS1, with the absence of a dihydrouridine (DHU) arm. Compared with mitogenomes of the ancestral insect and another parasitoid within Eupelmidae, large-scale rearrangements were found in the mitogenome of A. fulloi , especially inversions and inverse transpositions of tRNA genes. The gene arrangements of parasitoid mitogenomes within Chalcidoidea were variable. A novel gene arrangement was presented in the mitogenome of A. fulloi . Phylogenetic analyses based on the 13 protein-coding genes of 20 parasitoids indicated that the phylogenetic relationship of 6 superfamilies could be presented as Mymaridae + (Eupelmidae + (Encyrtidae + (Trichogrammatidae + (Pteromalidae + Eulophidae))). This study presents the first mitogenome of the Anastatus genus and offers insights into the identification, taxonomy, and phylogeny of these parasitoids.

Although the release of egg parasitoids has proven to be an effective strategy for the control of the fall armyworm (FAW), a single egg parasitoid, however, has exposed some deficiencies in practice, and it is worthwhile to explore whether the combination of multiple parasitoid species released can be used to control FAW by adopting an inter- or intra-specific relationship. In this study, we released compound parasitoid balls of Te. remus and Tr. chilonis in maize fields to explore the effects of combinations in different proportions of these two egg parasitoids on the control of the FAW. The results showed that the release of compound parasitoid balls improved the control effect on the FAW compared to the release of only Te. Remus (100%) and only Tr. Chilonis (100%). The treatments released with compound parasitoid balls significantly increased the egg parasitism rate against the FAW, reduced its populations, and alleviated its damage to maize as compared to the treatment with only Tr. chilonis (100%) released, whereas there was no significant difference in the egg parasitism rate and FAW populations between the treatments with the release of only Te. remus (100%) and that of compound parasitoid balls. Among the compound parasitoid balls with different proportions of egg parasitoids, the treatment with 80% Te. remus and 20% Tr. chilonis and that with 20% Te. remus and 80% Tr. chilonis could still retain more than 50% of the control effect against the FAW after 15 days of release and given the higher cost of production of Te. Remus, our results suggested that the combination of 20% Te. Remus and 80% Tr. Chilonis is a more cost-efficient ratio for the control of the FAW. Our findings may provide a new perspective for the sustainable control of the FAW.

T. chilonis is a commonly used biological agent, but its existing host eggs have shown some problems in the breeding of T. chilonis, and the search for more suitable host eggs is imminent. Here, we focused on S. c. ricini, an intermediate host that was used in the past for Trichogramma spp. but has since received less attention. We attempted to understand the effects of developmental temperature and duration on its longevity and egg production, evaluated the functional response of T. chilonis to S. c. ricini egg, and screened for a suitable wasp-to-egg ratio for the production of T. chilonis. Our results showed that the developmental temperature and duration after the emergence of T. chilonis significantly affected adult longevity and oviposition, that 25–28 °C is a suitable temperature range for the survival and e-g laying of S. c. ricini, and that a developmental duration of at least 24 h was required to obtain more qualified S. c. ricini eggs. T. chilonis demonstrated a type II functional response to S. c. ricini eggs; different wasp-to-egg ratios significantly affected the propagation efficiency of T. chilonis reproduction from S. c. ricini eggs, and the best reproduction efficiency was achieved with wasp-to-egg ratios of 1:2 and 1:3, Considering that there were no significant differences in most parameters between the two treatments, as well as cost concerns, we concluded that wasp-to-egg ratios of 1:2 are an important parameter that could be applied. Our results may provide some valuable insights into the mass rearing of T. chilonis.

Parasitoid wasps are rapidly developing as a model for evolutionary biology. Here we present chromosomal genomes of two Anastatus wasps, A. japonicus and A. fulloi , and leverage these genomes to study two fundamental questions—genome size evolution and venom evolution. Anastatus shows a much larger genome than is known among other wasps, with unexpectedly recent bursts of LTR retrotransposons. Importantly, several genomic innovations, including Piwi gene family expansion, ubiquitous Piwi expression profiles, as well as transposable element-piRNA coevolution, have likely emerged for transposable element silencing to maintain genomic stability. Additionally, we show that the co-option evolution arose by expression shifts in the venom gland plays a dominant role in venom turnover. We also highlight the potential importance of non-venom genes that are coexpressed with venom genes during venom evolution. Our findings greatly advance the current understanding of genome size evolution and venom evolution, and these genomic resources will facilitate comparative genomics studies of insects in the future. Parasitoid wasps are rapidly developing as a model for evolutionary biology. Here, the authors analyze the genomes of two Anastatus wasps, revealing genomic innovations related to maintenance of genomic stability, and rapid turnover of venom genes.

Light is a crucial environmental factor implicated in the temporal regulation of important biological events of insects, and some insects are usually sexually active in dark periods. However, the effects of light during dark periods on the growth, development, and fecundity of Spodoptera frugiperda, an important agricultural pest, remain unknown. In this study, we evaluated the effects of lighting in dark periods on the biological parameters of S. frugiperda in laboratory conditions. Our results showed that lighting in dark periods significantly prolonged the pre-adult stage and reduced the pupal survival and emergence rate. Moreover, the results indicated that the adult stage is the photoperiod-sensitive stage of S. frugiperda, and the fecundity and longevity of adults significantly reduced under lighting in dark periods, and the number of eggs per female moth decreased by 99% compared with the control. The mean generation time (T) of S. frugiperda population was the longest, and the intrinsic rate of natural increase (r) and finite rate of increase (λ) were the smallest under lighting in dark periods, and the population growth of S. frugiperda was significantly limited. Our findings may provide valuable insights to develop effective integrated pest management strategies to control S. frugiperda.

Trichogramma is a kind of egg parasitoid wasp that is widely used to control lepidopterous pests. Temperature is one of the main factors that determines the various life activities of this species, including development, reproduction and parasitism efficiency. Heat shock proteins (HSPs) are highly conserved and ubiquitous proteins that are best known for their responsiveness to temperature and other stresses. To explore the potential role of HSPs in Trichogramma species, we obtained the full-length cDNAs of six HSP genes (Tchsp10, Tchsp21.6, Tchsp60, Tchsp70, Tchsc70-3, and Tchsp90) from T. chilonis and analyzed their expression patterns during development and exposure to temperature stress. The deduced amino acid sequences of these HSP genes contained the typical signatures of their corresponding protein family and showed high homology to their counterparts in other species. The expression levels of Tchsp10, Tchsp21.6 and Tchsp60 decreased during development. However, the expression of Tchsc70-3 increased from the pupal stage to the adult stage. Tchsp70 and Tchsp90 exhibited the highest expression levels in the adult stage. The expression of six Tchsps was dramatically upregulated after 1 h of exposure to 32 and 40°C but did not significantly change after 1 h of exposure to 10 and 17°C. This result indicated that heat stress, rather than cold stress, induced the expression of HSP genes. Furthermore, the expression of these genes was time dependent, and the expression of each gene reached its peak after 1 h of heat exposure (40°C). Tchsp10 and Tchsp70 exhibited a low-intensity cold response after 4 and 8 h of exposure to 10°C, respectively, but the other genes did not respond to cold at any time points. These results suggested that HSPs may play different roles in the development of this organism and in its response to temperature stress.

Trichogramma is a useful species that is widely applied in biocontrol. Temperature profoundly affects the commercial application of T. chilonis. Different developmental transcriptomes of prepupae and pupae of T. chilonis under 10, 25, and 40°C were obtained from our previous study. In this study, transcriptomic analysis was further conducted to gain a clear understanding of the molecular changes in the prepupae of T. chilonis under different thermal conditions. A total of 37,295 unigenes were identified from 3 libraries of prepupae of T. chilonis, 17,293 of which were annotated. Differential expression analysis showed that 408 and 108 differentially expressed genes (DEGs) were identified after heat and cold treatment, respectively. Under heat stress, the pathway of protein processing in endoplasmic reticulum was found to be active. Most of the genes involved in this pathway were annotated as lethal (2) essential for life [l(2)efl] and heat shock protein genes (hsps), which were both highly upregulated. Nevertheless, most of the genes involved in another significantly enriched pathway of starch and sucrose metabolism were downregulated, including 1 alpha‐glucosidase gene and 2 beta‐glucuronidase genes. Under cold stress, no significantly enriched pathway was found, and the significantly enriched GO terms were related to the interaction with host and immune defenses. Together, these results provide us with a comprehensive view of the molecular mechanisms of T. chilonis in response to temperature stresses and will provide new insight into the mass rearing and utilization of T. chilonis. Transcriptomic responses to thermal stresses were characterized in prepupal Trichogramma chilonis. Two pathways were significantly enriched after heat treatment which may be important for heat tolerance in T. chilonis. A few DEGs were significantly enriched into GO terms related to interactions with host and immune defenses after cold treatment.

The predatory stink bug Eocanthecona furcellata belongs to the subfamily Asopinae of Pentatomidae. In the current study, the complete mitochondrial genome of E. furcellata is determined. This mitogenome is 16,085 bp in size and comprises of 13 protein-coding genes, 22 transfer RNA genes, two ribosomal RNA genes, and a control region. Gene order is identical to that of the putative ancestral arrangement of insects. Nucleotide composition is biased toward A and T, which together made up 75.5% of the entire genome. All tRNAs have the clover-leaf structure except for the tRNA Ser(AGN) and the length of them ranges from 61 to 73 bp. The monophyly of Pentatomidae is highly supported by the phylogenetic tree and E. furcellata is very close to other carnivorous species of the remaining Pentatomidae species.

Anastatus japonicus Ashmead is a widely used biological control agent against stink bugs that can be successfully reared using the large eggs of the Chinese silkworm. In this study, environmental factors responsible for the induction of diapause in A. japonicus were investigated on host eggs of the Chinese silkworm. A. japonicus exhibited a facultative, mature larval diapause within its host eggs. Second–third instar larva are the most sensitive stages to diapause stimuli. The accumulation of diapause stimuli during all the larval stages maximized the diapause response. A short photoperiod of 10L:14D and temperature of 17 °C led to the occurrence of the highest diapause response, while a long photoperiod (14L:10D) and low temperatures (11 and 14 °C) prevented the diapause. A specific exposure period was required to reach high diapause incidence. Diapausing mature larvae had a significantly higher survival rate after 180 days storage at 10 °C than that of nondiapausing mature larvae. Taken together, results suggest methods that could be exploited in the developmental regulation, field-release pretreatment technology, and long-term storage of A. japonicus.

The oriental fruit fly, Bactrocera dorsalis Hendel, causes serious losses to fruit production and is one of the most economically important pests in many countries, including China, Spalangia endius Walker is a pupal parasitoid of various dipteran hosts, and may be considered a potentially important ectoparasitic pupal parasitoid of B. dorsalis. However, lack of genetic information on this organism is an obstacle to understanding the mechanisms behind its interaction with this host. Analysis of the S. endius transcriptome is essential to extend the resources of genetic information on this species and, to support studies on S. endius on the host B. dorsalis. We performed de novo assembly RNA-seq of S. endius. We obtained nearly 10 Gbp of data using a HiSeq platform, and 36319 high-quality transcripts using Trinity software. A total of 22443 (61.79%) unigenes were aligned to homologous sequences in the jewel wasp and honeybee (Apis florae) protein set from public databases. A total of 10037 protein domains were identified in 7892 S. endius transcripts using HMMER3 software. We identified expression of six gustatory receptor and 21 odorant receptor genes in the sample, with only one gene having a high expression level in each family. The other genes had a low expression level, including two genes regulated by splicing. This result may be due to the wasps being kept under laboratory conditions. Additionally, a total of 3727 SSR markers were predicted, which could facilitate the identification of polymorphisms and functional genes within wasp populations. This transcriptome greatly improves our genetic understanding of S. endius and provides a large number of gene sequences for further study.