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Wolbachia endosymbionts may be acquired by horizontal transfer, by introgression through hybridization between closely related species, or by cladogenic retention during speciation. All three modes of acquisition have been demonstrated, but their relative frequency is largely unknown. Drosophila suzukii and its sister species D. subpulchrella harbor Wolbachia, denoted wSuz and wSpc, very closely related to wRi, identified in California populations of D. simulans. However, these variants differ in their induced phenotypes: wRi causes significant cytoplasmic incompatibility (CI) in D. simulans, but CI has not been detected in D. suzukii or D. subpulchrella. Our draft genomes of wSuz and wSpc contain full-length copies of 703 of the 734 single-copy genes found in wRi. Over these coding sequences, wSuz and wSpc differ by only 0.004% (i.e., 28 of 704,883 bp); they are sisters relative to wRi, from which each differs by 0.014%-0.015%. Using published data from D. melanogaster, Nasonia wasps and Nomada bees to calibrate relative rates of Wolbachia versus host nuclear divergence, we conclude that wSuz and wSpc are too similar-by at least a factor of 100-to be plausible candidates for cladogenic transmission. These three wRi-like Wolbachia, which differ in CI phenotype in their native hosts, have different numbers of orthologs of genes postulated to contribute to CI; and the CI loci differ at several nucleotides that may account for the CI difference. We discuss the general problem of distinguishing alternative modes of Wolbachia acquisition, focusing on the difficulties posed by limited knowledge of variation in absolute and relative rates of molecular evolution for host nuclear genomes, mitochondria, and Wolbachia.

Simple Summary: The brown marmorated stink bug, Halyomorpha halys, native to Asia, is now an insect pest in several countries. The sterile insect technique (SIT), involving the sterilization of insects by ionizing radiation and field release, is one method to control insect pest. This study examines the ultrastructure of H. halys spermiogenesis in both irradiated and wild males. Typical hemipteran sperm features were observed, such as mitochondrial derivative–axoneme bridges, the absence of accessory bodies, crystalline inclusions in mitochondrial derivatives, an acrosome with packed tubules, and a plaque-shaped microtubular organizing center (MTOC) in the centriolar region. Occasionally, two centrioles were observed in spermatids, with one disappearing later—a novel feature for insect spermiogenesis. In irradiated adults, cysts exhibited inconsistent radiation effects, including disorganized sperm arrangement, incomplete sperm cell divisions, multiple organelle copies within cells, failure to reabsorb cytoplasm, and a lack of axonemes. Additionally, rod-shaped viruses or virus-like particles were found in vasa deferentia, regardless of irradiation. Halyomorpha halys (Heteroptera: Pentatomidae) is an insect pest native to Asia that has spread over the last two decades to most of the North America, parts of South America, Europe and North Africa. Its impact is significant as it can feed on more than 300 host plants, rendering affected fruits and vegetable crops unsellable or of lower quality. Various chemical and biological methods have been used to control this pest, with varying degrees of success. The sterile insect technique (SIT) is a pest control method involving the sterilization of insects via ionizing radiation and their subsequent mass release into the field. In the present contribution, the spermiogenesis of H. halys was studied from an ultrastructural point of view in both irradiated and non-irradiated adult males. In both cases, we observed ultrastructural characteristics typical of hemipteran sperm cells: bridges connecting the mitochondrial derivatives and the axonemal microtubules, the absence of accessory bodies, and the presence of two or three crystalline inclusions within the mitochondrial derivatives, an acrosome composed of tightly packed tubules, and an atypical, plaque-shaped microtubular organizing center (MTOC) in the centriolar region. Moreover, in the same region, we seldom observed the presence of two centrioles in the spermatids, one of which disappeared at a later stage of maturation. This feature is a novelty for insect spermiogenesis. The cysts of irradiated adults were not all uniformly affected by the radiation. However, irradiated cysts sometimes exhibited a general disorganization of sperm arrangement, incomplete divisions of sperm cells resulting in multiple copies of the same organelle within the same cell, failure to reabsorb the cytoplasm, and the lack of axonemes. Finally, rod-shaped viruses or virus-like particles were observed in vasa deferentia independently of irradiation. [ABSTRACT FROM AUTHOR]

Drosophila suzukii causes economic damage to berry and stone fruit worldwide. Laboratory-generated datasets were standardized and combined on the basis of degree days (DD), using Gompertz and Cauchy curves for survival and reproduction. Eggs transitioned to larvae at 20.3 DD; larvae to pupae at 118.1 DD; and pupae to adults at 200 DD. All adults are expected to have died at 610 DD. Oviposition initiates at 210 DD and gradually increases to a maximum of 15 eggs per DD at 410 DD and subsequently decreases to zero at 610 DD. These data were used as the basis for a DD cohort-level population model. Laboratory survival under extreme temperatures when DD did not accumulate was described by a Gompertz curve based on calendar days. We determined that the initiation of the reproductive period of late dormant field-collected female D. suzukii ranged from 50 to 800 DD from January 1. This suggests that D. suzukii females can reproduce early in the season and are probably limited by availability of early host plants. Finally, we used the DD population model to examine hypothetical stage-specific mortality effects of IPM practices from insecticides and parasitoids at the field level. We found that adulticides applied during the early season will result in the largest comparative population decrease. It is clear from model outputs that parasitism levels comparable to those found in field studies may have a limited effect on population growth. Novel parasitoid guilds could therefore be improved and would be valuable for IPM of D. suzukii.

Temperature-dependent fecundity and survival data was integrated into a matrix population model to describe relative Drosophila suzukii Matsumura (Diptera: Drosophilidae) population increase and age structure based on environmental conditions. This novel modification of the classic Leslie matrix population model is presented as a way to examine how insect populations interact with the environment, and has application as a predictor of population density. For D. suzukii, we examined model implications for pest pressure on crops. As case studies, we examined model predictions in three small fruit production regions in the United States (US) and one in Italy. These production regions have distinctly different climates. In general, patterns of adult D. suzukii trap activity broadly mimicked seasonal population levels predicted by the model using only temperature data. Age structure of estimated populations suggest that trap and fruit infestation data are of limited value and are insufficient for model validation. Thus, we suggest alternative experiments for validation. The model is advantageous in that it provides stage-specific population estimation, which can potentially guide management strategies and provide unique opportunities to simulate stage-specific management effects such as insecticide applications or the effect of biological control on a specific life-stage. The two factors that drive initiation of the model are suitable temperatures (biofix) and availability of a suitable host medium (fruit). Although there are many factors affecting population dynamics of D. suzukii in the field, temperature-dependent survival and reproduction are believed to be the main drivers for D. suzukii populations.

Simple Summary: The sterile insect technique (SIT) is an eco-friendly control strategy, but to implement it effectively, the insects that are subject to sterilization through irradiation should have fitness levels that are comparable to wildtype individuals. This study aims to evaluate the potential use of this technique for the control of Bagrada hilaris by investigating the efficacy of courtship in pairs of insects with untreated females and males irradiated at 60 and 100 Gy under laboratory conditions, with a focus on vibrational communication. Males irradiated at 60 Gy and the controls (unirradiated males) exhibit reproductive behaviors and mating abilities that are similar to each other, while insects irradiated at 100 Gy show a severe decrease in the quality of sexual performance. The painted bug, Bagrada hilaris, is an agricultural pest in its original areas (Africa, South Asia, and the Middle East), and it has recently been recorded as an invasive species in southwestern part of the US, Chile, Mexico, and two islands in the Mediterranean basin. Its polyphagous diet causes severe damage to economically important crops. The control of this pest is primarily achieved by means of synthetic pesticides, which are often expensive, ineffective, and harmful to the ecosystem. Recent physiological bioassays to assess its potential control through the sterile insect technique demonstrated that mating between untreated females and males irradiated at doses of 64 and 100 Gy, respectively, resulted in 90% and 100% sterility of the eggs produced by the females. In this study, the mating abilities of virgin males irradiated at 60 and 100 Gy with virgin females were measured through a study of short-range courtship mediated by vibrational communication. The results indicate that males irradiated at 100 Gy emit signals with lower peak frequencies, mate significantly less than unirradiated males do, and do not surpass the early stages of courtship. Conversely, males irradiated at 60 Gy present vibrational signal frequencies that are comparable to those of the control and successfully mated males. Our findings suggest that B. hilaris individuals irradiated at 60 Gy are good candidates for the control of this species, given that they retain sexual competitiveness regardless of their sterility, through an area-wide program that incorporates the sterile insect technique. [ABSTRACT FROM AUTHOR]

The brown marmorated stink bug, Halyomorpha halys, is an invasive agricultural and urban pest capable of feeding on over 100 species of host plants. The antennae of this bug play an important role not only in detecting food and mates but also in short-range location of conspecifics when aggregating for diapause. The morphology and distribution of antennal sensilla of H. halys were investigated at an ultrastructural level using scanning and transmission electron microscopy approaches. Adults have 5-segmented antennae, made up of a scape, a 2-segmented pedicel and two flagellomeres, while 5th instar nymphs have shorter, 4-segmented antennae, with only one pedicel segment. Five types of sensilla are distinguished, based on their shape, length and basal width and the presence of basal socket and pores: sensilla basiconica (types A, B, C, D and E), sensilla coeloconica, sensilla trichoidea and sensilla chaetica (types A and B). Sexual dimorphism was not observed in this species, with respect to the morphological features and abundance of sensilla. The most abundant sensory structures are sensilla trichoidea showing characteristics typical of olfactory sensilla, whereas the least abundant are sensilla coeloconica which may be involved in thermo- and hygro-reception. Basiconic sensilla type A are solely identified on the antennae of 5th instar nymphs, where they presumably have a dual mechanosensorygustatory role. The putative function of the remaining sensilla are herein discussed. [ABSTRACT FROM AUTHOR]