How many cooperators are too many? Foundress number, reproduction and sex ratio in a quasi-social parasitoid

In the parasitoid genus Sclerodermus, multiple foundresses produce and care for communal broods on large hosts, which can lead to greater reproductive success for group members than attempting to reproduce alone. We explore the consequences of foundress group size on the benefits of cooperative brooding and on brood sex ratios by providing groups of 10-55 foundresses with a single host and no alternative reproductive options. Within this range, increasing foundress group size leads to increasingly common failure in brood production and diminished per capita success. Group production of adult offspring declines once foundress number reaches around 25. Brood failure is usually at the early developmental stages, and current evidence suggests that there may be competition among foundresses for oviposition sites, possibly involving reproductive dominance and ovicide, which also delays initial brood production. Once broods become established, their rate of development is enhanced by large foundress numbers. The sex ratios of broods are very strongly female biased, irrespective of the foundress number. As this bias is not easily explained by standard models of local mate competition or by a recent model of local resource enhancement, we suggest an explanation based on control of sex allocation by a minority of dominant foundresses, which monopolise the production of adult males.Peer reviewe

Factors affecting the reproduction and mass-rearing of sclerodermus brevicornis (Hymenoptera: Bethylidae), a natural enemy of exotic flat-faced longhorn beetles (Coleoptera: Cerambycidae: Lamiinae)

© 2020 by the authors. Licensee MDPI, Basel, Switzerland. Many species of long-horned beetles are invasive pests causing significant economic damage in agro-forestry systems. They spend the majority of their life-cycle concealed inside natural wood or wooden packaging materials and are largely protected from adverse environmental conditions and pesticide sprays. Biological control via parasitoid natural enemies including members of the bethylid genus Sclerodermus, has proven effective against some long-horned beetles that are invasive in China. In Europe, the biocontrol potential of native Sclerodermus species is being evaluated with a view to developing efficient mass-rearing techniques and then actively deploying them against invasive Asian beetles. Here, we continue evaluations of S. brevicornis by establishing that groups of females that have already reared offspring to emergence are capable of reproducing subsequent hosts and by evaluating the lifetime reproductive capacity of individual females provided with successive hosts. Additionally, we assess the laboratory shelf-life of adult females stored for different times at different temperatures including cold storage, and then assess the post-storage reproductive performance of groups of females provided with a single host. We found that adult female longevity declines with increasing storage temperature and that most aspects of subsequent performance are negatively affected by high temperatures. The adaptability to low temperature storage enhances the suitability of S. brevicornis to mass-rearing programs and thus biocontrol deployment

Individual and group level sex ratios under local mate competition: consequences of infanticide and reproductive dominance

Extremely female-biased sex ratios of parasitoid wasps in multiple-foundress groups challenges evolutionary theory which predicts diminishing bias as foundress numbers increase. Recent theory based on foundress cooperation has achieved qualitative rather than quantitative success in explaining bias among parasitoids in the genus Sclerodermus. Here, we develop an explanation, expanding the theory of local mate competition, based on the observation that male production seems dominated by some foundresses within groups. Two sex ratio effects arise from such reproductive dominance: an immediate effect via suppression of male production, and a long-term evolutionary response to reproductive skew. We analyze the outcome of these effects at the individual and group level, the latter being more readily observable. Three model scenarios are analyzed: (1) random killing of developing sons in a group by all foundresses, without reproductive skew, (2) the development of reproductive dominance by some foundresses after sex allocation decisions by all foundresses have been implemented, and (3) reproductive dominance within foundress groups before sex allocation decisions are implemented. The 3 scenarios have subtly different implications for sex ratio evolution, with Models 2 and 3 being novel additions to theory, showing how reproductive dominance can alter the outcome of sex ratio evolution. All models match observations in their outcomes better than other recently proposed theory, but Models 2 and 3 are closest to observations in their underlying assumptions. Further, Model 2 shows that differential offspring mortality after parental investment can influence the primary sex ratio even when random with respect to parental and offspring characters, but targeted at entire clutches. The novel models are solved for both diploid and haplodiploid genetic systems, and confirmed with simulations. Overall, these models provide a feasible explanation for the extremely female-biased sex ratios produced by multi-foundress groups and expand the scope of local mate competition theory to consider reproductive dominance.Peer reviewe

Reproductive performance effects of rearing the quasi-social parasitoid, Sclerodermus brevicornis (Hymenoptera: Bethylidae), on a factitious host

Publisher Copyright: © The Author(s) 2023. Published by Oxford University Press on behalf of Entomological Society of America.Wasps in the genus Sclerodermus are ectoparasitoids that typically attack the larvae of woodboring coleopterans. Interest in these species is increasing as they are used in programs to control longhorn beetle pests of economic importance in China and have invasive pest control potential in Europe. Wasps may be mass reared for field release, but using the target host species can be time consuming and physically demanding. There is thus a need for factitious hosts with lower production costs and that are easier to rear. The present research focuses on Sclerodermus brevicornis, which was found in Italy in association with the invasive longhorn beetle, Psacothea hilaris hilaris, and can be laboratory reared on this longhorn beetle and on a factitious lepidopteran host, Corcyra cephalonica. As it is known that the biology of natural enemies can be influenced by the host they emerge from and that the behavior of S. brevicornis is relatively complex due to its degree of sociality (multiple foundress females cooperate to paralyze the host and produce offspring communally), we explored whether, and how, performance and behavioral traits of adult females are influenced by the host species on which they were reared, both when no choice or a choice of current host species was offered. We evaluated the survival of foundresses and their movements between offered hosts and their tendency to form groups with other foundresses according to kinship and host characteristics. We also evaluated the production of offspring and the timing of their development. We found that S. brevicornis reared from C. cephalonica do have some disadvantages compared with those that have developed on P. h. hilaris but also that they recognize, prefer, and can reproduce on P. h. hilaris. We conclude that the use of the more convenient factitious host for mass-rearing is unlikely to greatly compromise the potential of S. brevicornis to suppress longhorn beetle pests in the field.Peer reviewe

Microbial and chemical stability of Acheta domesticus powder during one year storage period at room temperature

The sustainability of food systems is of growing concern worldwide, so insects are a growing source of animal proteins for food and feed. Among insect species, the house cricket, Acheta domesticus, is a promising option from a sustainability point of view. This study aimed at evaluating both microbiological and chemical stability of A. domesticus powders during one year of storage at room temperature. Our study was conducted on cricket powders obtained by three different processes: drying at 80°C (P80), drying at 120°C (P120), and lyophilization (PL). Regarding microbiological profile, the pathogens Listeria monocytogenes and Salmonella were not detected, while total viable count and lactic acid bacteria tended to decrease during the storage period. Bacillus cereus was detected at low counts during the entire storage period, but only one replicate of P80 exceeded the limit set for A. domesticus by the European Commission Implementing Regulation 2017/2470. The measured protein contents of the cricket powders immediately after production ranged between 60.6 and 64.3%. The peroxide values were far higher than the limit established by the EU Regulation in all samples. Higher amounts of hexanal and pentanal were detected in P80 and P120 than in PL, indicating that oven drying could enhance lipid oxidation. In conclusion, a one year shelf-life can suitably be ascribed to the analyzed cricket powders from a microbiological point of view, but lacked chemical stability and had a clear early tendency toward rancidity. The samples dried at 120°C and lyophilized never exceeded the limit set by European Commission for B. cereus count in A. domesticus powder. In addition, lyophilized samples showed the lowest values of hexanal and pentanal, the aldehydes that are primarily responsible for the rancid smell. The oxidative status of the final products could be strongly influenced by the powder processing, so for this reason, edible insect species-specific post-rearing protocols should be implemented. These results open an interesting scenario for a long period of storage of insect powder in the absence of a cold chain, making the insect market an increasingly sustainable sector

Exploring the range expansion of the yellow‐spotted longhorn beetle Psacothea hilaris hilaris in northern Italy

1. Psacothea hilaris hilaris is an exotic cerambycid detected in Lombardy (northern Italy) in 2005 and now established and undergoing an expansion phase. The species constitutes a serious pest for Ficus spp. and Morus spp. 2. The aim of this work is to update the distribution area of the species in Italy, inves- tigating its expansion over 16 years. Data were acquired through the authors’ direct field records and community science, by data mining on national and international web platforms and social networks. Reports were analysed and GPS points plotted in ArcMap 10.8.1 to obtain distribution maps. 3. Of the records collected, 34% were acquired during field surveys, 22% via e-mail and 44% through on-line forums and social networks. 4. AdultsofP.h.hilarisshowedalongperiodofactivity,fromApriltothebeginningof December, with a peak of presence from June to September. The presence of the pest has been ascertained over six provinces in Lombardy covering an area esti- mated at more than 1750 km2 in 2021. New detections occurred within 2 km of a known infestation from the previous year in 41.6% of cases, and between 2 and 4 km away in 37.7% of cases. The mean rate of range expansion estimated from reported records was 3.17 ± 0.33 km/year from 2010 to 2021. After an initial phase of settlement, the insect is now spreading southward. 5. Giventherelevantphytosanitaryinterestthatthespeciesmayhaveforfigplantsin Italy and in the Mediterranean Basin, it is fundamental to deepen the knowledge about its flight biology, dynamics and active dispersal capabilities in order to esti- mate the future range expansion

Insect Biodiversity in a Prealpine Suburban Hilly Area in Italy

Human activities and habitat fragmentation are known to greatly influence biodiversity. The aim of this study was to update an entomological checklist of a prealpine area in Italy, and also to evaluate the influence of different habitats and the proximity to cities on the entomological fauna. This study included different areas of a local park in Northern Italy, covering about 4000 ha, and situated at altitudes between 190 and 960 m asl. The surveys were carried out between 2010 and 2013 using different monitoring techniques (pitfall traps, car mounted nets, light traps, direct catches on soil and vegetation, visual sampling, gall collection). Furthermore, to assess the effect of habitat and locality on the composition of epigeic beetles, pitfall traps were set and inspected from April to September. All captured specimens were classified to species level. A total of 409 species were recorded, belonging to 7 orders and 78 families. A total of 76.1% were represented by Coleoptera, 13% Lepidoptera, 9.4% Hymenoptera, followed by other orders. In particular, some species with peculiar characteristics, or whose presence in the area had not been previously reported, were detected, such as Atheta pseudoelongatula, Ocypus rhaeticus, Tasgius tricinctus, Euplagia quadripunctaria, Scotopteryx angularia, Elachista constitella, Parornix bifurca, Oegoconia huemeri, and Lasius (Lasius) alienus. It seems possible that the habitat affected the community more than the locality. The woods showed a reduced biodiversity, and a simplified community structure. The comparison of the same habitats in different localities did not show significant differences

Data_Sheet_1_Microbial and chemical stability of Acheta domesticus powder during one year storage period at room temperature.docx

The sustainability of food systems is of growing concern worldwide, so insects are a growing source of animal proteins for food and feed. Among insect species, the house cricket, Acheta domesticus, is a promising option from a sustainability point of view. This study aimed at evaluating both microbiological and chemical stability of A. domesticus powders during one year of storage at room temperature. Our study was conducted on cricket powders obtained by three different processes: drying at 80°C (P80), drying at 120°C (P120), and lyophilization (PL). Regarding microbiological profile, the pathogens Listeria monocytogenes and Salmonella were not detected, while total viable count and lactic acid bacteria tended to decrease during the storage period. Bacillus cereus was detected at low counts during the entire storage period, but only one replicate of P80 exceeded the limit set for A. domesticus by the European Commission Implementing Regulation 2017/2470. The measured protein contents of the cricket powders immediately after production ranged between 60.6 and 64.3%. The peroxide values were far higher than the limit established by the EU Regulation in all samples. Higher amounts of hexanal and pentanal were detected in P80 and P120 than in PL, indicating that oven drying could enhance lipid oxidation. In conclusion, a one year shelf-life can suitably be ascribed to the analyzed cricket powders from a microbiological point of view, but lacked chemical stability and had a clear early tendency toward rancidity. The samples dried at 120°C and lyophilized never exceeded the limit set by European Commission for B. cereus count in A. domesticus powder. In addition, lyophilized samples showed the lowest values of hexanal and pentanal, the aldehydes that are primarily responsible for the rancid smell. The oxidative status of the final products could be strongly influenced by the powder processing, so for this reason, edible insect species-specific post-rearing protocols should be implemented. These results open an interesting scenario for a long period of storage of insect powder in the absence of a cold chain, making the insect market an increasingly sustainable sector.</p