Insect Populations Research Articles

Widespread annual occurrence of pesticides within designated critical habitats for endangered prairie butterflies

Insect declines have become pronounced in prairie ecosystems, particularly in areas of agricultural intensification. Non-target pesticide exposure has been raised as a key concern for prairie remnant health. Over seven years, we screened grass and soil samples for the presence and quantities of hundreds of pesticides from five prairies in Minnesota and South Dakota that are designated as Critical Habitat for two globally endangered butterflies: Poweshiek skipperling and Dakota skipper. We documented dozens of pesticides across all sites and years on their larval host grasses. Interiors of prairies were not less likely to have detectable pesticides than along prairie-agriculture edges. Broad-spectrum organophosphate and pyrethroid insecticides were common in late season. Chlorpyrifos quantities were higher at sites where both endangered species have been extirpated. Neonicotinoid insecticides, which have been frequently attributed to declines in insect pollinators, did not present a significant exposure signal in these prairie habitats. Few pesticides were detected in soil or early season grass samples. The prevalence and quantities of pesticides we observed are likely underestimates, and additional research is needed on the landscape of risk at small and large scales. Implications for Conservation: Protected prairies are not immune to the risk of pesticide exposure, which may impact efforts to re-establish lost populations of imperiled prairie insects, including endangered butterflies.

Impact of Nitrogen and Silicon Amendments on Hopper Population in Rice

Present study showed that total dry weight values of rice plants were significantly higher in the plant with high nitrogen (N) application (100kg/ ha) as compared to low nitrogen (30 kg/ ha) treatment whereas the silicon (Si) amendment had very little effect on biomass accumulation but both the elements are associated with hopper pest population densities in rice. Here the correlation coefficient values were high- r= 0.759 to 0.999 and r= 0.726 to 0.996 for brown planthopper Nilaparvata lugens (Stål) and green leafhopper Nephotettix virescens (Dist.) respectively when the calculation was made between insect population and plant biomass after application of nitrogen 0 to 100 kg/ ha. However, when calcium silicate was added 140 kg/ ha or above with high doses of nitrogen the N. lugens and N. virescens incidence reduced in comparison to others. Consequently, the interaction between nitrogen and silicon play a significant role in resistance to these hopper pests.

Pesticide Pressure on Insect and Human Population: A Review

It is estimated that the current 7 billion world population would increase by 70 million people year, or 30%, to reach 9.2 billion by 2050. It is anticipated that this increased population density will result in a 70% rise in the demand for food production. This increase is mostly attributable to shifts in emerging countries' dietary trends toward higher-quality foods, such as increased consumption of meat and dairy products and the growing use of cereals for animal feed. There isn't much more agricultural land available. Any growth will primarily come at the price of forests and other natural ecosystems that support wildlife, wild cousins of crops, and organic pest adversaries. Additionally, rather than producing food, more agricultural land will be used to create bio-based commodities like fiber and biofuel. As a result, we must produce food on even less area, with even less water, and with less energy, pesticides, and fertilizer than we do now. There is an urgent need for sustainable production at elevated levels in light of these constraints. Reducing the present output losses resulting from pests is a significant obstacle to agricultural productivity. This review covers pest-related crop losses worldwide, estimates of productivity linked to pesticide use, costs and benefits of pesticide use, chemical yield loss reduction strategies, biological and recombinant pest control methods, and the difficulties facing the crop protection sector. In deciding how pesticides will be used in agriculture in the future, the general public plays a crucial role. However, the external issues related to the impacts of pesticides on human and environmental health must also be addressed as long as there is a need for pesticide-based solutions to pest management issues and food security concerns.

From buzzes to bytes: A systematic review of automated bioacoustics models used to detect, classify and monitor insects

Abstract Insects play vital ecological roles; many provide essential ecosystem services while others are economically devastating pests and disease vectors. Concerns over insect population declines and expansion have generated a pressing need to effectively monitor insects across broad spatial and temporal scales. A promising approach is bioacoustics, which uses sound to study ecological communities. Despite recent increases in machine learning technologies, the status of emerging automated bioacoustics methods for monitoring insects is not well known, limiting potential applications. To address this gap, we systematically review the effectiveness of automated bioacoustics models over the past four decades, analysing 176 studies that met our inclusion criteria. We describe their strengths and limitations compared to traditional methods and propose productive avenues forward. We found automated bioacoustics models for 302 insect species distributed across nine Orders. Studies used intentional calls (e.g. grasshopper stridulation), by‐products of flight (e.g. bee wingbeats) and indirectly produced sounds (e.g. grain movement) for identification. Pests were the most common study focus, driven largely by weevils and borers moving in dried food and wood. All disease vector studies focused on mosquitoes. A quarter of the studies compared multiple insect families. Our review illustrates that machine learning, and deep learning in particular, are becoming the gold standard for bioacoustics automated modelling approaches. We identified models that could classify hundreds of insect species with over 90% accuracy. Bioacoustics models can be useful for reducing lethal sampling, monitoring phenological patterns within and across days and working in locations or conditions where traditional methods are less effective (e.g. shady, shrubby or remote areas). However, it is important to note that not all insect taxa emit easily detectable sounds, and that sound pollution may impede effective recordings in some environmental contexts. Synthesis and applications: Automated bioacoustics methods can be a useful tool for monitoring insects and addressing pressing ecological and societal questions. Successful applications include assessing insect biodiversity, distribution and behaviour, as well as evaluating the effectiveness of restoration and pest control efforts. We recommend collaborations among ecologists and machine learning experts to increase model use by researchers and practitioners.

Morpho-molecular study of entomopathogenic fungi associated with citrus orchard pests in Northern Iran.

Entomopathogenic fungi play a significant role in regulating insect populations in nature and have potential applications in pest management strategies in different regions. Citrus spp. are among the important horticultural products in northern Iran, and the orchards are affected by different insect pests, especially mealybugs. This study aimed to isolate and identify entomopathogenic fungi associated with citrus orchard pests in northern Iran, focusing on Akanthomyces and Lecanicillium species on mealybugs. Through the samples collected from different regions within Guilan province, 12 fungal isolates were collected and identified based on the combination of morphological characteristics and molecular data. Akanthomyces lecanii, A. muscarius, Engyodontium rectidentatum, Lecanicillium aphanocladii and Lecanicillium rasoulzarei sp. nov. were identified. Of these, A. muscarius on Lepidosaphes sp., E. rectidentatum on Coccidae, and L. aphanocladii on Tetranychus urticae are reported as new fungal-host records from Iran. Moreover, a new species, Lecanicillium rasoulzarei, is illustrated, described, and compared with closely related species.

Fragmentation and Connectivity in dehesa Ecosystems Associated with Cerambyx spp. Dispersion and Control: A Graph-Theory Approach

Xylophagous insects play a crucial role in forest ecosystems, contributing to population dynamics. The “Cerambyx complex” (CC) constitutes an emerging pest in Mediterranean oak woodlands. We studied the fragmentation and connectivity of holm and cork oak stands in Andalusia (Spain), and the relationships with the current dispersion of CC, as well as the effect on the connectivity and dispersion patterns with the implementation of nests of a predator bird (Garrulus glandarius) to reduce insect populations in highly connected areas. The Kernel Density Estimation (KDE) was used to assess the spatial distribution of CC. Connectivity was assessed using graphs theory (Graphab 2.6) to characterize the importance of patches and linkages for contributing to dispersal. We selected the Eurasian jay (G. glandarius) as a reference bird species to generate “barriers” to the dispersion of the CC. We used the probability of connectivity (PC) and the flux (F) to compare the effect of the introduction of Eurasian jay nets. Results showed an increasing trend in the distribution and incidence of CC during the period 2001–2016, resulting in 7.3% and 13.1% mortality rates for Q. ilex and Q. suber, respectively. The connectivity model using only Q. ilex and Q. suber forests as reference habitats was not enough to explain the distribution of CC. The value of PC and F metrics decreased by 38.09% and 20.59% by introducing 300 nests of Eurasian jay. Our methodology provides a pest management tool using connectivity metrics, which can be integrated with other variables to control pest outbreaks and pest dispersion.

Key roles of insulin receptor InR1 in initiating reproductive diapause in males of the cabbage beetle Colaphellus bowringi (Coleoptera: Chrysomelidae).

Reproductive diapause serves as a valuable strategy enabling insects to survive unfavorable seasonal conditions. However, forcing insects into diapause when the environment is conducive to their well-being can cause them to miss out on seasonal opportunities for reproduction. This outcome not only reduces insect populations but also minimizes crop losses caused by insect feeding. Therefore, altering the timing of diapause initiation presents a potential strategy for managing pests. In this study, we examined the possible role of the Insulin Receptor 1 (InR1) in controlling reproductive diapause entry in the male cabbage beetle, Colaphellus bowringi. Compared to short-day (SD) conditions, long-day (LD) conditions led to reproductive diapause of C. bowringi males, characterized by arrested gonad development, increased Triglyceride (TG) accumulation, and upregulated expression of diapause protein 1 and genes associated with lipogenesis and stress tolerance. Upon employing RNA interference to knock down InR1 under SD conditions, males destined for reproduction were compelled into diapause, evidenced by arrested gonadal development, accumulation of TG, and elevated expression of diapause-related genes. Intriguingly, despite the common association of the absence of juvenile hormone (JH) with reproductive diapause in females, the knockdown of InR1 in males did not significant affect the expression of JH biosynthesis and JH response gene. The study highlight InR1 is a key factor involved in regulating male reproductive diapause in C. bowringi. Consequently, targeting insulin signaling could be a viable approach to perturb diapause timing, offering a promising strategy for managing pests with reproductive diapause capabilities. © 2024 Society of Chemical Industry.

Detection and Differentiation of Entomopathogenic Serratia spp. to Inform Reintroduction of the Critically Endangered Lord Howe Island Stick Insect Dryococelus australis.

Once rodents have been successfully eradicated from Lord Howe Island, Australia, the critically endangered Lord Howe Island stick insect (Dryococelus australis (Montrouzier)) may be reintroduced, a century after it was thought to have become extinct. In captive populations of D. australis, elevated mortalities have been associated with bacterial pathogens. To better define the infectious risk posed by entomopathogens to the reintroduction program, we investigated the bacteria isolated from captive D. australis kept at Melbourne Zoo and on Lord Howe Island and from environmental samples and free-living invertebrates collected on various parts of the island. At Melbourne Zoo, Serratia and Pseudomonas spp. were the bacteria most frequently isolated between 2013 and 2019. Serratia spp. were also the organisms most frequently isolated from insects sampled in April 2019 from the captive population on Lord Howe Island. In addition, Serratia spp. were isolated from a range of environmental samples collected on Lord Howe Island during March-April 2019. These environmental isolates had a broader range of biochemical and molecular characteristics than those obtained from the captive insect populations. A large proportion of these isolates were urease positive and had biochemical profiles previously not described for Serratia spp. This study highlights the need for better surveillance for potential pathogens in understudied regions and sites. We conclude that infections caused by Serratia spp. might pose a problem to the captive breeding program for D. australis but that the risk of introducing novel pathogens to Lord Howe Island through infected insects is low. Our study explores some of the potential risks involved in captive breeding and provides a valuable example of using pathogen surveillance to better inform an invertebrate conservation program.

Seasonal syndromic surveillance by sentinel system of ILI, ARI, SARI and pneumonia in Romania – season 2023/2024

Syndromic surveillance was initially developed for early detection compared to traditional methods of an epidemiological event with an impact on public health, but as it was applied by more countries it was observed that it can provide information on the size, dynamics of the spread with an emphasis on the potential for national, regional and global evolution, the severity and the most affected population groups, but also to the development of a quick, specific response. Globalization, which involves the intensification of the movement of people (including sick or incubating infectious diseases), live animals, or products of animal origin in and from any part of the planet, but also climate change and pollution, amplifies the danger of the spread of communicable infectious diseases from areas so-called “specific” diseases in new areas, unknown to populations and healthcare systems. In this context, the One Health initiative needs efficient surveillance methods to help promote the health of people, animals, the environment, and ultimately the planet Earth. Recently, there have been substantial changes in the surveillance and control of infectious diseases with an impact on public health aimed at assessing the risks of the emergence of infectious agents with epidemic and pandemic potential by identifying and analyzing favorable factors related to the infectious agent (virulence, variability, transmissibility, etc.), the host organism (immunity, physiological factors, vaccination status, associated chronic diseases, nutritional status, living conditions, etc.), demographic factors (birth rate, mortality, population agglomerations), climatic factors and insect populations vectors, rodents and wild animals (including birds) and last but not least domestic animal populations (including birds). Among these methods, syndromic surveillance stands out, which in addition has the quality of using automatic data acquisition and generating statistical alerts, monitors disease indicators in real-time or near real-time to detect disease outbreaks earlier than would be possible with conventional methods traditional public health. In this context, we will present the Romanian experience regarding the syndromic surveillance of ILI, ARI and SARI in Romania through the national sentinel system season 2023/2024.

High temporal resolution data reveal low bat and insect activity over managed meadows in central Europe

Increasing agriculture and pesticide use have led to declines in insect populations and biodiversity worldwide. In addition to insect diversity, it is also important to consider insect abundance, due to the importance of insects as food for species at higher trophic levels such as bats. We monitored spatiotemporal variation in abundance of nocturnal flying insects over meadows, a common open landscape structure in central Europe, and correlated it with bat feeding activity. Our most important result was that insect abundance was almost always extremely low. This was true regardless of management intensity of the different meadows monitored. We also found no correlation of insect abundance or the presence of insect swarms with bat feeding activity. This suggests that insect abundance over meadows was too low and insect swarms too rare for bats to risk expending energy to search for them. Meadows appeared to be poor habitat for nocturnal flying insects, and of low value as a foraging habitat for bats. Our study highlights the importance of long-term monitoring of insect abundance, especially at high temporal scales to identify and protect foraging habitats. This will become increasingly important given the rapid decline of insects.

Patch exploitation behaviour by a parasitoid of a forest pest: The influence of host cues and intra‐ and interspecific interactions

Abstract For parasitoids, host foraging is the most significant activity for their reproductive success, as it directly translates into offspring production. Therefore, foraging behaviour and patch‐use decisions by parasitoids still attract research interest, especially when the studied species are biological control agents. In laboratory conditions, we studied the patch exploitation behaviour of Megarhyssa nortoni (Hymenoptera: Ichneumonidae), a larval–pupal parasitoid of several woodwasps (Hymenoptera: Siricidae), exposed to intra‐ and interspecific interactions. It is known that M. nortoni females are attracted to the symbiotic fungus carried by its hosts, which support host larval development inside the wood. Additionally, in the introduced range where the species has been released in biocontrol programs aimed at managing invasive Sirex noctilio populations, Megarhyssa nortoni coexists with the egg–larval parasitoid Ibalia leucospoides. First, we investigated whether host–fungal symbiont cues and direct presence of conspecific females affected patch time allocation and oviposition behaviour of M. nortoni, as both stimuli could provide information on concealed hosts. Second, we studied the influence of prior parasitism by I. leucospoides on patch time allocation decisions and oviposition behaviour. The main results showed that females modulated their responses to the fungal cues when foraging simultaneously with conspecifics. Also, patch‐leaving tendencies and patch residence times were not affected when females foraged patches previously exploited by I. leucospoides; indeed, they probed these patches more frequently. Our study contributes to the understanding of patch‐use decisions made by parasitoids and their impact on the biological control of damaging insect populations, particularly in a context of two parasitoid species and one host.

Estimation of genetic parameters for the implementation of selective breeding in commercial insect production

BackgroundThere is a burgeoning interest in using insects as a sustainable source of food and feed, particularly by capitalising on various waste materials and by-products that are typically considered of low value. Enhancing the commercial production of insects can be achieved through two main approaches: optimising environmental conditions and implementing selective breeding strategies. In order to successfully target desirable traits through selective breeding, having a thorough understanding of the genetic parameters pertaining to those traits is essential. In this study, a full-sib half-sib mating design was used to estimate variance components and heritabilities for larval size and survival at day seven of development, development time and survival from egg to adult, and to estimate correlations between these traits, within an outbred population of house flies (Musca domestica), using high-throughput phenotyping for data collection.ResultsThe results revealed low to intermediate heritabilities and positive genetic correlations between all traits except development time and survival to day seven of development and from egg to adulthood. Surprisingly, larval size at day seven exhibited a comparatively low heritability (0.10) in contrast to development time (0.25), a trait that is believed to have a stronger association with overall fitness. A decline in family numbers resulting from low mating success and high overall mortality reduced the amount of available data which resulted in large standard errors for the estimated parameters. Environmental factors made a substantial contribution to the phenotypic variation, which was overall high for all traits.ConclusionsThere is potential for genetic improvement in all studied traits and estimates of genetic correlations indicate a partly shared genetic architecture among the traits. All estimates have large standard errors. Implementing high-throughput phenotyping is imperative for the estimation of genetic parameters in fast developing insects, and facilitates age synchronisation, which is vital in a breeding population. In spite of endeavours to minimise non-genetic sources of variation, all traits demonstrated substantial influences from environmental components. This emphasises the necessity of thorough attention to the experimental design before breeding is initiated in insect populations.

Open paleoenvironment and dry climate in south India immediately before the Youngest Toba Tuff eruption (~75 ka) are suggested by Vondrichnus structures at the Jwalapuram locality, Jurreru valley

Abstract The Younger Toba Tuff (YTT) eruption is regarded as one of the largest of its time and possibly responsible for changing past climate and vegetation from C3 to C4 in the Indian subcontinent. A paleosol constituting a Toba pre-tephra horizon at the Jwalapuram locality, exhibits the preservation of biogenic structures identified as Vondrichnus planoglobus and Vondrichnus obovatus. This study investigated their paleoecological and paleoenvironmental significance. These structures are hard and compact, rounded to sub-rounded, spherical to sub-spherical bodies with empty chambers, surrounded by carbonate layers, and preserved in close proximity to termite pipes and nests and rhizolith structures. Their occurrence in the Jwalapuram area is significant, as the locality has been well documented as suitable for reconstruction of past climate and vegetation in light of the impact of the YTT eruption. Based on the present findings, we assume that the investigated locality would likely have an insect population and bush to scrub vegetation, indicating a dry environment immediately before the YTT eruption.

Survival and alterations in reproductive organs of the cotton boll weevil, Anthonomus grandis grandis, fed alternative food

AbstractThe cotton boll weevil, Anthonomus grandis grandis Boheman (Coleoptera: Curculionidae), is one of the most important insect pests of cotton, causing significant yield losses. This insect completes its life cycle only on the flower structures of some Malvaceae species, with cotton being its preferred host. However, during the cotton off‐season, the boll weevil enters a reproductive dormancy state, in tropical regions, with important alterations in their reproduction organs. During this period, a remaining insect population survives feeding on a variety of other food sources, but the insects do not reproduce. We hypothesized that these alterations in the insect's reproductive organs are associated with the nutritional levels provided by alternative food sources during the cotton off‐season. To test our hypothesis, we first investigated food sources that sustain insect survival for long periods, such as weed species and fruits of cultivated crops. Then, we evaluated how various food sources affect the reproductive organs and reproductive capacity of the boll weevil. Among the alternative food sources tested, insect longevity was highest on banana (Musa paradisiaca L.), mango (Mangifera indica L.), papaya (Carica papaya L.), milkweed (Euphorbia heterophylla L.), and lilac tasselflower (Emilia sonchifolia L.). However, only banana and mango resulted in greater longevity than cotton squares. Banana was the preferred food and resulted in the highest levels of nutrients in the insects. Additionally, insects previously fed on banana made more oviposition punctures on cotton squares than those fed only on cotton squares, which resulted in a significantly higher number of emerged adults. Histological analysis of the insects' reproductive organs showed that feeding on papaya resulted in morphological changes and testicle degradation. In conclusion, we present evidence that boll weevils fed on alternative food sources (other than cotton squares or similar‐quality food) display a nutritional imbalance, associated with substantial alterations in the reproductive tissues of this insect, which may trigger the reproductive dormancy state.

Population Abundance and Frequency of Visits Forcipomyia spp. (Diptera: Ceratopogonidae) on Cocoa Plantations in Lima Puluh Kota District, Indonesia

Forcipomyia spp. is a pollinator insect on cacao plants that belongs to the Ceratopogonidae Family, Diptera Order. The objectives of this research were to determine the abundance of the insect population of Forcipomyia spp. in Lima Puluh Kota District and to determine the frequency of visits of those insects to cacao flowers. This research was conducted on a small smallholder plantation in Sungai Talang Village, Lima Puluh Kota District. Then, the samples obtained were identified at the Andalas University Laboratory. This research was conducted using a survey method and purposive sampling technique. Five cacao plants were selected in each plot of land, and then three flower beds per plant were selected to bloom. Sampling was carried out by installing yellow sticky traps. The insects obtained were put into a collection bottle filled with 96% alcohol to preserve those insects, and then the abundance of Forcipomyia spp. Insects were calculated. The research results showed that the highest insect abundance was in Jorong Guguak Nunang: 1.260 individuals, then in Jorong Bukik Apik: 1.061 individuals and the lowest was in Jorong Boncah: 1.045 individuals. The highest frequency of visits was in the morning, with an average of 648 individuals/60 minutes. The insect diversity index based on the Shannon-Wienner Diversity Index in Jorong Guguak Nunang was 1,97; in Jorong Boncah, it was 2,21; in Jorong Bukik Apik was 1,88, and all of it is in the medium diversity level category.

Comparative Efficacy of different Funnel Diameters in Light Traps against Major Phototactic Insect Pests of rabi Season

Light traps have been long used to reduce and manage insect populations. Although there are numerous types and designs of insect light traps. Four distinct light traps were employed for the study and positioned within the BSP Unit Adhartal, JNKVV Jabalpur from mid-November 2022 to mid-April 2023 for the study of the efficiency test of different funnel diameters of light traps based on performance. Comparative studies of light trap catches revealed that 50 cm funnel diameter light traps have given higher response in following species for Helicoverpa armigera (13.91%), Agrotis ipsilon (14.36%), Creatonotus gengis (13.97%), Gryllus bamaculatus (22.26%), Gryllotalpa orientalis (45.30%), Nezara viridula (9.82%), Amata cyssea (13.35%), Asota ficus (7.01%), Perina nuda (21.78%), and Thysanoplusia orichalcea (22.75%). There was a statistically significant increase in trap catches in the 50 cm funnel diameter light traps compared to the 40 cm funnel diameter traps. However, there was a statistically non-significant difference between the 40 cm and 50 cm funnel diameter traps for Spodoptera litura and Theretra oldenlandiae species, although the trap catches were numerically higher in the 50 cm funnel diameter traps because 50 cm funnel diameter provide large catchment area for insects.

Study of yellow leaf virus disease on eggplant (Solanum melongena L.) in West Sumatra

Yellow leaf virus disease, accompanied by vector insect attacks, was the leading cause of the current decline in eggplant production. Yellow leaf virus disease spreads more quickly due to the influence of insect vectors. The research aims to determine the type of insect vector that spreads yellow leaf virus disease and the incidence and severity of yellow leaf virus disease on eggplants in West Sumatra. This research method uses a survey method for five months in 2023. The sample was taken diagonally with five observation points. At each point, five plant samples were taken randomly. Observations were carried out three times at four locations representing the centers of eggplant production areas in West Sumatra, namely in Kuranji District, Pauh District, Batang Anai District, and Sitoga District. Five different vector insect species were discovered, along with their corresponding population sizes, according to the observations: Bemisia tabaci (5846 individuals), Amrasca sp. (1199 individuals), Thrips sp. (176 individuals), Paracoccus sp. (43 individuals), and Aphids gosypii (34 individuals). The incidence of the disease reached 90% with the severity of the disease being 42.45% in Sitoga District. The highest disease severity was 43.94% in Kuranji District, with an incidence of the disease of 70%. This research helps implement strategies to control yellow leaf virus disease by determining the threshold for the influence of the number of vector insect populations in increasing the incidence and severity of yellow leaf virus disease in eggplants.

Host plant-mediation of viral transmission and its consequences for a native butterfly.

Pathogens play a key role in insect population dynamics, contributing to short-term fluctuations in abundance as well as long-term demographic trends. Two key factors that influence the effects of entomopathogens on herbivorous insect populations are modes of pathogen transmission and larval host plants. In this study, we examined tritrophic interactions between a sequestering specialist lepidopteran, Euphydryas phaeton, and a viral pathogen, Junonia coenia densovirus, on its native host plant, Chelone glabra, and a novel host plant, Plantago lanceolata, to explore whether host plant mediates viral transmission, survival, and viral loads. A two-factor factorial experiment was conducted in the laboratory with natal larval clusters randomly assigned to either the native or novel host plant and crossed with either uninoculated controls or viral inoculation (20% of individuals in the cluster inoculated). Diapausing clusters were overwintered in the laboratory and checked weekly for mortality. At the end of diapause, all surviving individuals were reared to adulthood to estimate survivorship. All individuals were screened to quantify viral loads, and estimate horizontal transmission postmortem. To test for vertical transmission, adults were mated, and the progeny were screened for viral presence. Within virus-treated groups, we found evidence for both horizontal and vertical transmission. Larval clusters reared on the native host plant had slightly higher horizontal transmission. Survival probability was lower in clusters feeding on the native host plant, with inoculated groups reared on the native host plant experiencing complete mortality. Viral loads did not differ by the host plant, although viral loads decreased with increased sequestration of secondary compounds on both host plants. Our results indicate that the use of a novel host plant may confer fitness benefits in terms of survival and reduced viral transmission when larvae feeding on it are infected with this pathogen, supporting hypotheses of potential evolutionary advantages of a host range expansion in the context of tritrophic interactions.

Monitoring of the species composition and number of insects and mites on the apple trees in the Right Bank Forest Steppe of Ukraine

Goal. To monitor the species composition and abundance of insects and mites on apple trees in the Right-Bank Forest-Steppe of Ukraine.
 Methods. Field, laboratory, microscopic, mathematical, statistical and calculation methods. The research was carried out according to generally accepted methods in entomology and plant protection, starting in early spring (late April — early May before harvest).
 Results. Monitoring of the number of insect pests and mites on apple trees in three types of plantations was carried out: a young orchard on stunted rootstocks with an intensive protection system; an old orchard on tall rootstocks with a protection system; an old orchard without treatments (long-term control).
 Conclusions. Monitoring of species composition and dynamics of pests number makes it possible to study and substantiate the patterns in the structure of insect and mite populations, to predict their harmfulness and to improve the protection system of apple trees or its individual components.

Divergent dynamics of sexual and habitat isolation at the transition between stick insect populations and species

Speciation is often viewed as a continuum along which populations diverge until they become reproductively-isolated species. However, such divergence may be heterogeneous, proceeding in fits and bursts, rather than being uniform and gradual. We show in Timema stick insects that one component of reproductive isolation evolves non-uniformly across this continuum, whereas another does not. Specifically, we use thousands of host-preference and mating trials to study habitat and sexual isolation among 42 pairs of taxa spanning a range of genomic differentiation and divergence time. We find that habitat isolation is uncoupled from genomic differentiation within species, but accumulates linearly with it between species. In contrast, sexual isolation accumulates linearly across the speciation continuum, and thus exhibits similar dynamics to morphological traits not implicated in reproductive isolation. The results show different evolutionary dynamics for different components of reproductive isolation and highlight a special relevance for species status in the process of speciation.