Biology subjects

Abram, P. K.

Publications and source records attributed to Abram, P. K..

17 recordsLinked to original sources

bioRxiv2026

Rearing Istocheta aldrichi (Diptera: Tachinidae) from field-collected Japanese beetles (Popillia japonica): 1. Methods to improve insect collection and parasitoid pupariation

Istocheta aldrichi (Diptera: Tachinidae), a specialist parasitoid of the invasive Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae), was released to eastern North America in the 1920s as part of a classical biological control program. Further releases are being considered in different regions of North America and Europe where P. japonica is establishing. Successful releases of the biocontrol agent depend on identifying efficient techniques for collecting parasitized hosts from the field and rearing the parasitoid through diapause to obtain I. aldrichi adults. In this study, we evaluated how the collection date, the collection method (hand-picking vs. regular traps vs. modified traps) and rearing conditions (food provision and substrate type) of parasitized hosts influence I. aldrichi pupariation and emergence. The proportion of parasitized beetles yielding I. aldrichi puparia decreased considerably as the season progressed. Rearing conditions immediately after collection influenced both puparium yield and quality: withholding food from parasitized P. japonica slightly increased puparium yield but reduced puparium weight, while the effect of food provision on subsequent overwintering survival depended on rearing substrate. Finally, simple modifications to commercial traps (larger, ventilated, containers with added food source and substrate) collected more beetles than regular traps and promoted successful development of the parasitoid to the puparium stage. Our results are used to suggest basic guidelines for collecting and rearing I. aldrichi in experimental research and applied biological control of P. japonica.

ecology↗

bioRxiv2026

Rearing Istocheta aldrichi (Diptera: Tachinidae) from field-collected Japanese beetle (Popillia japonica): methods to improve overwintering, adult emergence and longevity

Istocheta aldrichi (Diptera: Tachinidae) is a specialist parasitoid of the invasive Japanese beetle, Popillia japonica (Coleoptera: Scarabaeidae). Research and releases for biological control depend on field collecting parasitized hosts and rearing the parasitoid through diapause to obtain I. aldrichi adults. This study investigated how rearing practices before, during and after the seasonal overwintering period affected the proportion of I. aldrichi pupae that emerged as adults, the timing of parasitoid emergence, and their longevity. Increasing cold exposure duration during overwintering increased adult I. aldrichi emergence from puparia and reduced development time after transfer to warm conditions. Adult I. aldrichi emergence from overwintered puparia depended on interactions between overwintering environment (indoors vs. outdoors), spring thermal regime, and the timing of host collection in the previous season. Burying puparia in the soil in late summer/early fall resulted in higher subsequent adult I. aldrichi emergence. Manipulating spring temperatures in controlled environments allowed parasitoid emergence to be staggered over several weeks without reducing emergence success. Emergence under outdoor spring conditions was unreliable. Adult longevity was affected by temperature and diet: cooler conditions extended lifespan, honey-water increased longevity relative to pollen alone or honey-water and pollen together. These results provide a foundation to further improve I. aldrichi rearing techniques for use in experimental research and applied biological control of P. japonica.

ecology↗

bioRxiv2025

The realized host specificity of Leptopilina japonica and Ganaspis kimorum, adventive larval parasitoids of the invasive Drosophila suzukii

The non-native larval parasitoid wasps Leptopilina japonica and Ganaspis kimorum (Hymenoptera: Figitidae), which attack larvae of the invasive pest Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), were unintentionally introduced to the Pacific Northwest of North America between 10 and 15 years ago, and are now well-established. Previous laboratory studies conducted to assess the ecological risk of classical biological control introductions suggested that G. kimorum is highly host-specific, whereas L. japonica can develop in several other drosophilid species. Information on realized host use of the parasitoids under field conditions in the context of host-parasitoid food webs in their non-native range is limited. A two-year field study in coastal British Columbia, Canada was conducted, using complementary sampling methods to document host-parasitoid associations and quantify parasitoid specificity with respect to drosophilid communities inhabiting ripe and rotting fruit. Consistent with previous laboratory findings, G. kimorum was reared exclusively from D. suzukii, while L. japonica emerged primarily from D. suzukii but also from D. melanogaster and, less frequently, from members of the D. obscura species group. Leptopilina japonica shared some host species with the resident parasitoid species L. heterotoma and Asobara cf. rufescens. A particularly striking result was the extent to which almost all drosophilid and parasitoid taxa in this studys host-parasitoid trophic webs were non-native, complicating the interpretation of non-target ecological effects of L. japonica. These results provide field-based evidence of realized host use by these two non-native larval parasitoids of D. suzukii that can inform their future use in classical and augmentative biological control programs.

ecology↗

bioRxiv2025

An introduced parasitoid facilitates host range expansion of a resident parasitoid

Invasive species can cause maladaptive behaviours in native consumers, with evolution of behavioural or physiological traits thought to be the main way out of these so-called evolutionary traps. However, shorter-term ecological processes resulting from biological invasions could provide other ways to escape evolutionary traps. Asobara cf. rufescens, a resident (i.e., possibly native or previously introduced) parasitoid of drosophilid fly larvae in North America, can rarely produce offspring on the invasive fruit pest Drosophila suzukii in the laboratory, but in often emerges from field-collected D. suzukii. We hypothesized that the successful development of A. cf. rufescens in D. suzukii in the field is facilitated by Leptopilina japonica, a recently introduced parasitoid of D. suzukii. In laboratory experiments, we found that A. cf. rufescens had more than 30-fold higher offspring emergence from D. suzukii when L. japonica was also present. This facilitation occurred most frequently when A. cf. rufescens parasitized D. suzukii after L. japonica, possibly because parasitism by L. japonica destroyed the hosts cellular immunity that would otherwise prevent A. cf. rufescens development. The recent arrival of L. japonica may have partially rescued A. cf. rufescens from the evolutionary trap set by D. suzukii and, consequently, resulted in an expansion of its host range.

ecology↗

bioRxiv2025

Island invasions by the non-native vinegar fly Drosophila suzukii and its parasitoid wasps

Understanding how island characteristics influence the establishment and impact of invasive species and their natural enemies could inform both island biogeography and biological control theory. We studied the occurrence and relative abundances of the globally invasive fruit fly, Drosophila suzukii, and its recently introduced larval parasitoids, Leptopilina japonica and Ganaspis kimorum, across islands with varying sizes and levels of human-mediated transport in the Gulf and San Juan Islands of British Columbia (Canada) and Washington State (USA). Across two years and 58 sites, we collected D. suzukii and its parasitoids from wild blackberry, Rubus armeniacus, fruit. We predicted that parasitoids were more likely to be present on larger islands with higher levels of human activity and higher D. suzukii densities, and that the less specialized parasitoid species (L. japonica) would be more likely to establish on islands. We detected D. suzukii across all islands, indicating widespread establishment of this invasive pest. In contrast, we observed parasitoids on fewer than half of the islands. Leptopilina japonica was the only parasitoid of D. suzukii detected on islands. Parasitoid presence was marginally positively associated with island area and host density, but not average annual vehicle-ferry traffic (an indicator of human-mediated propagule pressure). Parasitism levels were low throughout the study region and we did not observe lower relative abundances of D. suzukii on islands where parasitoids were present - in fact, the relative abundance of D. suzukii tended to be higher on islands where the parasitoid L. japonica was detected. These findings suggest that island characteristics, host density, and a consumers host specificity may be associated with early establishment of introduced consumers on islands, but that a consumers presence may not inevitably result in host population suppression, at least over the short term.

ecology↗

bioRxiv2025

Consistent thrips biological control by Orius insidiosus on cucumber plants despite different LED lighting regimes

Artificial lighting, particularly light-emitting diodes (LEDs), is widely used in controlled- environment agriculture (CEA) to enhance crop productivity. Yet, light also acts as a sensory cue, directly and indirectly affecting insect pests and their natural enemies. Despite growing interest, the impacts of LEDs on multitrophic interactions remain poorly understood. This study assessed how spectral photoperiod extension modulates top-down effects (predator effects on pest densities, pest-related damage to plants, and plant defense-related gene expression) and bottom-up effects (plant morphology, light assimilation, and defense as well as growth hormone-related gene expression) in a tri-trophic system involving a plant, Cucumis sativus (greenhouse cucumber), a pest insect, Frankliniella occidentalis (western flower thrips), and a predator used for biological control, Orius insidiosus. Plants were exposed for two weeks to a 12-hour artificial sunlight simulating a cloudy winter day, with or without an 8-hour extension of blue, blue-red, or blue-green-red LEDs. Orius insidiosus reduced thrips populations by 96% {+/-} 9%, regardless of light treatment, and decreased foliar damage due to thrips by 46% on average. Predators produced offspring under all lighting conditions, although total numbers of O. insidiosus were lower under blue-green-red lighting. Pest densities remained similar across all light treatments, suggesting that light supplementation did not benefit F. occidentalis. Blue and blue-red spectra improved plant light assimilation, and photoperiod extension generally increased dry biomass (8% {+/-} 11%). Defense-related phytohormones were only marginally affected; surprisingly, some jasmonic acid pathway-related genes were upregulated in the presence of predators, suggesting additional plant-mediated effects. Our results underscore the potential of O. insidiosus to provide biological pest control services under artificial lighting regimes already used in crop production. Key MessageO_LILighting in agriculture alters dynamics of pest and beneficial insects C_LIO_LIWe asked how LED spectra influence net biological control outcomes in a tri-trophic system C_LIO_LIO. insidiosus reduced pest numbers by 96% and foliar damage by 46% C_LIO_LIPredators increased the expression of some jasmonic acid-related genes C_LIO_LIO. insidiosus showed potential for pest suppression under different lighting regimes C_LI

ecology↗

bioRxiv2025

Different artificial lighting spectra change the mating behavior of generalist predator Orius insidiosus (Say), and photoperiod extension promotes its development

In protected cropping systems such as greenhouses and indoor farming, augmentative biological control depends on release rates, establishment, and reproduction of natural enemies. Light-emitting diodes (LEDs) are widely used to enhance plant growth in these systems and are increasingly implemented in mass-rearing facilities for natural enemies. However, the impacts of LEDs on the life cycle of beneficial predators remain insufficiently explored. This study examined the mating behaviors and developmental performance of generalist predator Orius insidiosus under light spectra previously shown to support its predation of the pest thrips Frankliniella occidentalis. In laboratory experiments, predator pairs were exposed to artificial light sequences starting with a 12h base light condition simulating a cloudy winter day, supplemented by 8h photoperiod extensions (blue, blue-red, or blue-green-red spectra), and a control without extension. Mating occurred under all tested conditions, but blue light reduced mating probability, frequency, and duration. Photoperiod extension improved fecundity, fertility, and second-generation numbers of O. insidiosus adults, with blue light favoring egg laying and hatching but not metamorphosis into adults. The second-generation sex ratio was unaffected by light sequence, maintaining population viability with a balanced proportion of females. Our findings demonstrate that O. insidiosus can successfully mate, reproduce, and develop under artificial lighting and highlight the potential of modulating light spectrum to optimize both mass-rearing and establishment in protected crops. HighlightsO_LIPhotoperiod extension enhances development of the predatory bug O. insidiosus. C_LIO_LIBlue light reduces O. insidiosus mating probability, frequency, and duration. C_LIO_LIPhotoperiod extension with blue light favors O. insidiosus fertility and fecundity. C_LIO_LIOrius insidiosus sex ratio is unaffected by photoperiod. C_LIO_LILEDs could enhance natural enemy establishment in protected crops. C_LI

animal behavior and cognition↗

bioRxiv2024

Artificial lighting affects the predation performance of the predatory bug Orius insidiosus (Say) against the Western flower thrips Frankliniella occidentalis (Pergande)

Protected crops, such as greenhouses and indoor farming environments, using light-emitting diodes (LEDs) enable the modulation of the light spectrum, intensity, and photoperiod for agronomic purposes. This creates dynamic artificial light conditions for insects and arachnids, including predators used in biological control. Despite increasing interest, the effects of LEDs on predator behavior and control performance remain poorly understood. In the laboratory, we examined the locomotion and predation behaviors of the generalist predator Orius insidiosus against the pest Frankliniella occidentalis under various light spectra and intensities. We tested narrowband blue, green, and red spectra, three ratios of red and blue light, and a spectrum combining all three colors across a gradient of light intensity in microcosms. Orius insidiosus was active and successfully attacked prey under all lighting conditions, with 70% of individuals engaging in predation during the observation period. The light spectrum significantly influenced all recorded behaviors, while light intensity had negligible effects. Narrowband spectra led to the highest attack probabilities, but the mixed blue-red spectrum with a higher proportion of red light yielded the highest prey capture rates. The spectrum with all three colors showed intermediate capture success. These trends were consistent regarding capture probability in more complex environments with cucumber plants, where thrips were exposed to 24-hour artificial light sequences before and during predator releases. However, thrips survival rates remained similar across all lighting treatments. Our results demonstrated that while lighting treatments affect predator behavior, Orius insidiosus retains its ability to capture prey under various light conditions. This paves the way for developing lighting strategies that balance plant productivity with effective biological control in protected crop environments.

animal behavior and cognition↗

bioRxiv2023

A method for sampling parasitized Drosophila suzukii puparia from soil

Methods to measure the diversity and biological control impact of parasitoids for the control of spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) are being developed in support of biological control programs around the world. Existing methods to determine parasitism levels and parasitoid species composition focus on sampling D. suzukii within fresh and rotting fruit. However, many D. suzukii pupate in the soil or in dropped fruit, where additional parasitism could occur and where their parasitoids are thought to overwinter. Here we introduce a method for extracting parasitized D. suzukii puparia from the soil through a sieve and flotation system, allowing for effective collection of puparia, from which parasitoids can then be reared. Although the method considerably underestimates the absolute number of puparia in soil samples, it nonetheless yields a high number of puparia relative to sampling effort and provides a robust estimate of the relative abundance of puparia among samples. Using this method, we confirmed that at least five species of parasitoids, including some that have rarely been detected in past studies, overwinter in their immature stages inside D. suzukii puparia in south coastal British Columbia, Canada. The ability to sample puparia from the soil will lead to a more comprehensive view of both D. suzukii and parasitoid abundance throughout the season, help confirm parasitoid establishment following intentional releases, and provide a way to measure the diversity of parasitoid species and potential interactions among parasitoids (e.g., hyper- or klepto-parasitism) that can often occur on the soil surface.

ecology↗

bioRxiv2023

Supplemental LED lighting improves plant growth without affecting biological control in a tri-trophic greenhouse system

Artificial lighting, including light-emitting diode (LED) illumination, is increasingly being optimized in protected agricultural systems to maximize plant yield and quality. However, it may also cause other top-down and bottom-up effects in these relatively simple ecological communities that also include insect pests and their natural enemies. While some effects of LED lighting on insects have been demonstrated to date, it is not known how they influence biological control of insect pests in practice. To examine potential top-down and bottom-up impacts of LED illumination on greenhouse biological control with parasitoids, we studied the effects of artificially lengthened days on a tri-trophic system in cages and in a greenhouse. We grew plants under a 12-hour photoperiod of white-supplemented light with 6 hours of additional 1) white light or 2) red and blue light, or 3) with no additional light. We exposed the plants to the pest aphid Myzus persicae (Hemiptera : Aphididae) with or without its parasitoid wasp Aphidius matricariae (Hymenoptera : Braconidae), or to no insects. The 18-hour light treatments increased mean plant dry mass by 127% compared with the 12-hour control without affecting the aphids population density or the parasitoids biological control efficacy under relatively low light conditions. This suggests that insect communities in protected agriculture can be resilient to even drastic changes in their light environment, and that adjusting crop lighting in a manner that affects plant growth does not necessarily compromise biological controls effectiveness.

ecology↗

bioRxiv2023

The effects of LED daylength extensions on the fecundity of the pest aphid Myzus persicae and the daily activity patterns of its parasitoid, Aphidius matricariae

Supplemental lighting, such as with LED lamps, allows greenhouse producers to maintain yields when natural light levels are low. Since both insect pests and their natural enemies are sensitive to light, both the duration and spectrum of LED daylength extensions could affect biological pest control in greenhouses. Longer days could allow for extended periods of reproduction for pests or foraging activity of biological control agents, possibly depending on the spectra used for these extensions. However, the effects of lengthening days with different LED spectra on the behaviour of biological control agents has mostly been studied in short-term experiments to date, and has not always included the context of the lights effect on their hosts reproduction. In growth chambers, we examined the locomotor activity of the parasitoid biocontrol agent Aphidius matricariae (Hymenoptera : Braconidae) as a predictor for foraging activity and the fecundity of its aphid host Myzus persicae (Hemiptera : Aphididae) over multiple days under different daylength extension regimes representative of those used in greenhouse vegetable production. We compared the effects of 14, 16, 18, and 20 h photoperiods, and 12 h days extended by 6 h with three different spectral qualities. The parasitoids adjusted how their activity was distributed throughout the lit period of the day (i.e., its total duration and peak timing) without changing the total amount of daily activity, regardless of the photoperiod or the light spectrum used for daylength extension. The aphids peak fecundity was not affected by photoperiod or spectral quality. Our results suggest that at least some behavioral and reproductive traits of these insects can be resilient to even drastic changes in their light environment.

ecology↗

bioRxiv2022

Protective geometry and reproductive anatomy as candidate determinants of clutch size variation in pentatomid bugs

Many animals lay their eggs in clusters. Eggs on the periphery of clusters can be at higher risk of mortality. We asked whether the most commonly occurring clutch sizes in pentatomid bugs could result from geometrical arrangements that maximize the proportion of eggs in the clusters interior. Although the most common clutch sizes do not correspond with geometric optimality, stink bugs do tend to lay clusters of eggs in shapes that protect increasing proportions of their offspring as clutch sizes increase. We also considered whether ovariole number, an aspect of reproductive anatomy that may be a fixed trait across many pentatomids, could explain observed distributions of clutch sizes. The most common clutch sizes across many species correspond with multiples of ovariole number. However, there are species with the same number of ovarioles that lay clutches of widely varying size, among which multiples of ovariole number are not over-represented. In pentatomid bugs, reproductive anatomy appears to be more important than egg mass geometry in determining clutch size uniformity. In addition, within this group of animals that has lost most of its variation in ovariole number, clutches with a broad range of shapes and sizes may still be laid.

ecology↗

bioRxiv2022

Partial refuges from biological control due to intraspecific variation in protective host traits: a case study with the egg parasitoid Trissolcus japonicus

Predicting how much of a host or prey population may be attacked by their natural enemies is fundamental to several subfields of applied ecology, particularly biological control of pest organisms. Hosts or prey can occupy refuges from natural enemy attack, but habitat or ecological refuges are challenging or impossible to predict in a laboratory setting - which is often where efficacy and specificity testing of candidate biological control agents is done. Here we explore how intraspecific variation in continuous traits that confers some protection from natural enemy attack - even after the natural enemy has encountered the prey - could provide partial refuges. The size of these trait-based refuges should depend on the relationship between trait values and host/prey susceptibility to natural enemy attack, and on how common different trait values are within a host/prey population. These can be readily estimated in laboratory testing of natural enemy impact on target or non-target prey or hosts as long as sufficient host material is available. We provide a general framework for how intraspecific variation in protective host traits could be integrated into biological control research, specifically with reference to non-target testing as part of classical biological control programs. As a case study, we exposed different host clutch sizes of target (pest) and non-target (native species) stink bug (Hemiptera: Pentatomidae) species to a well-studied exotic biocontrol agent, the egg parasitoid Trissolcus japonicus (Hymenoptera: Scelionidae). Although we observed several behavioural and reproductive responses to variation in host egg mass size by T. japonicus, they did not translate to increases in predicted refuge size (proportion host survival) large enough to change the conclusions of non-target testing. We encourage researchers to investigate intraspecific variation in a wider variety of protective host and prey traits and their consequences for refuge size.

ecology↗

bioRxiv2021

Adventive larval parasitoids reconstruct their close association with spotted-wing drosophila in the invaded North American range

Two species of larval parasitoids of the globally invasive fruit pest, Drosophila suzukii (Diptera: Drosophilidae), Leptopilina japonica and Ganaspis brasiliensis (both Hymenoptera: Figitidae), were detected in British Columbia, Canada in 2019. Both are presumed to have been unintentionally introduced from Asia, however; the extent of their establishment across different habitats with diverse host plants used by D. suzukii was unclear. In addition, there was no knowledge of the temporal dynamics of parasitism of D. suzukii by these two parasitoids. We repeatedly sampled the fruits of known host plants of D. suzukii over the entire 2020 growing season in British Columbia. We documented the presence of L. japonica and G. brasiliensis and estimated the apparent percentage of D. suzukii parasitized. Across a large region of southwestern British Columbia, both L. japonica and G. brasiliensis were found to be very common across a variety of mostly unmanaged habitats over the entire course of the season (May-October) in the fruits of most host plants known to host D. suzukii larvae. The two parasitoids were responsible for more than 98% of D. suzukii larval parasitism and usually co-existed. Parasitism of D. suzukii was variable among hosts plants and sites (0-66% percent parasitism) and appeared to be time-structured. Our study demonstrates that the close association between the two larval parasitoids and D. suzukii that exists in Asia has evidently been reconstructed in North America, resulting in the highest parasitism levels of D. suzukii yet recorded outside of its area of origin.

ecology↗

bioRxiv2021

Sticky Pi, an AI-powered smart insect trap for community chronoecology

In the face of severe environmental crises that threaten insect biodiversity, new technologies are imperative to monitor both the identity and ecology of insect species. Traditionally, insect surveys rely on manual collection of traps, which provide abundance data but mask the large intra- and inter-day variations in insect activity, an important facet of their ecology. Although laboratory studies have shown that circadian processes are central to insects biological functions, from feeding to reproduction, we lack the high-frequency monitoring tools to study insect circadian biology in the field. To address these issues, we developed the Sticky Pi, a novel, autonomous, open-source, insect trap that acquires images of sticky cards every twenty minutes. Using custom deep-learning algorithms, we automatically and accurately scored where, when and which insects were captured. First, we validated our device in controlled laboratory conditions with a classic chronobiological model organism, Drosophila melanogaster. Then, we deployed an array of Sticky Pis to the field to characterise the daily activity of an agricultural pest, Drosophila suzukii, and its parasitoid wasps. Finally, we demonstrate the wide scope of our smart trap by describing the sympatric arrangement of insect temporal niches in a community, without targeting particular taxa a priori. Together, the automatic identification and high sampling rate of our tool provide biologists with unique data that impacts research far beyond chronobiology; with applications to biodiversity monitoring and pest control as well as fundamental implications for phenology, behavioural ecology, and ecophysiology. We released the Sticky Pi project as an open community resource on https://doc.sticky-pi.com.

ecology↗

bioRxiv2021

DROP: Molecular voucher database for identification of Drosophila parasitoids

Molecular identification is increasingly used to speed up biodiversity surveys and laboratory experiments. However, many groups of organisms cannot be reliably identified using standard databases such as GenBank or BOLD due to lack of sequenced voucher specimens identified by experts. Sometimes a large number of sequences are available, but with too many errors to allow identification. Here we address this problem for parasitoids of Drosophila by introducing a curated open-access molecular reference database, DROP (Drosophila parasitoids). Identifying Drosophila parasitoids is challenging and poses a major impediment to realize the full potential of this model system in studies ranging from molecular mechanisms to food webs, and in biological control of Drosophila suzukii. In DROP (http://doi.org/10.5281/zenodo.4519656), genetic data are linked to voucher specimens and, where possible, the voucher specimens are identified by taxonomists and vetted through direct comparison with primary type material. To initiate DROP, we curated 154 laboratory strains, 856 vouchers, 554 DNA sequences, 16 genomes, 14 transcriptomes, and 6 proteomes drawn from a total of 183 operational taxonomic units (OTUs): 114 described Drosophila parasitoid species and 69 provisional species. We found species richness of Drosophila parasitoids to be heavily underestimated and provide an updated taxonomic catalogue for the community. DROP offers accurate molecular identification and improves cross-referencing between individual studies that we hope will catalyze research on this diverse and fascinating model system. Our effort should also serve as an example for researchers facing similar molecular identification problems in other groups of organisms.

genomics↗

bioRxiv2020

An effective cold storage method for stockpiling Halyomorpha halys eggs for field surveys and laboratory rearing of Trissolcus japonicus

An effective stockpiling method for egg masses of the invasive brown marmorated stink bug (Halyomorpha halys [St[a]l]; Hemiptera: Pentatomidae) would be useful for rearing and field studies of its egg parasitoid Trissolcus japonicus (Ashmead) (Hymenoptera: Scelionidae). The current method of stockpiling H. halys egg masses at sub-zero temperatures has lethal and sublethal fitness consequences for T. japonicus. We show that parasitoid emergence from egg masses refrigerated at 8{degrees}C for up to two months before parasitism is higher than from frozen egg masses and usually has minimal or no sublethal fitness effects (sex ratio, development time, activity, fecundity, longevity, and weight) on emerging T. japonicus. Only after two months of host egg refrigeration did the emergence of T. japonicus begin to decrease significantly (by 9.6% relative to untreated viable egg masses), whereas egg masses previously frozen at -80{degrees}C had a 58.8% reduction in parasitoid emergence after 14 days of storage. Refrigerated egg masses that were subsequently exposed to average field temperatures (warm: 22.9{degrees}C; cool: 13.2{degrees}C) were still suitable for T. japonicus parasitism after 7 days, while viable egg masses exposed to warm temperatures for 7 days before parasitism had 24.1% lower parasitoid emergence. Our results demonstrate that refrigeration at 8{degrees}C, while resulting in complete mortality of H. halys embryos after 10 days, are more suitable for T. japonicus parasitism than those stored at sub-zero temperatures. The quantity and quality of H. halys eggs that can be stockpiled with this method could facilitate T. japonicus laboratory colony maintenance, field monitoring, and releases.

ecology↗