Insect Population Dynamics Research Articles

Adaptability of Toxoptera aurantii (Hemiptera: Aphididae) to Different Tea Cultivars

The adaptability of phytophagous insects to different host plants is a key determinant of their population propagation. Understanding the feeding behaviour and population dynamics of insects is crucial for elucidating host adaptability and screening for insect-resistant germplasms. Here, we investigated Toxoptera aurantii (Hemiptera: Aphididae) adaptability using electropenetrography and assessed its population growth on seven tea cultivars: Huangjinya (HJY), Qianmei601 (QM601), Fudingdabaicha (FD), Longjing43 (LJ43), Qiancha1 (QC1), Qiancha8 (QC8) and Qiancha10 (QC10). The results showed that the feeding behaviour of T. aurantii differed significantly depending on the tea cultivars. The initial probing of T. aurantii on HJY was the earliest among the seven host plants. Aphids on QC1 and QC10 displayed an increased duration of stylet probing and decreased ingestion of phloem sap, whereas a contrasting trend was observed for aphids on HJY. In addition, the mechanical resistance of T. aurantii fed on HJY and QM601 during the probing phase was significantly lower than that of aphids fed on other cultivars. Population dynamic parameters revealed that the growth rate of T. aurantii reared on HJY was the fastest, and its population quantity within 15 days was markedly higher than that of aphids fed on other cultivars. These findings demonstrate that HJY is the most suitable host plant, whereas QC1 and QC10 are less suitable hosts for T. aurantii, although the aphids successfully survived on all the selected tea cultivars. Our results provide valuable information for the biological control of T. aurantii using resistant tea varieties.

Forensic entomology as an advanced tool in crime investigation

The use of research on insects and other arthropods in court proceedings is known as forensic entomology. When forensic insects are discovered on a human body or at the crime scenes, their biodiversity, biology, ecology, and behavior can reveal details about the period since death and occasionally even the reason of the death. The forensic insects have been utilized in criminal investigations from decades, they have only recently become a very well-known and separate field in forensic investigations. Knowledge of local insect assemblages and population dynamics is crucial in medico-legal entomology for a successful criminal investigation when monitoring and analyzing insects on a corpse. Forensic entomology comprises three subspecialties, namely urban, stored goods, and medico-legal. The insects that colonize corpses provide valuable insights into the decomposition process. In cases where traditional methods for determining the time since death are limited, Calliphoridae, a family of flies, provides crucial evidence. Two well-established approaches for estimating the post-mortem interval rely on the development of maggots and the succession patterns of insect species. Forensic entomology has gained significant popularity among criminal investigators and forensic entomologists, leading to the emergence of various related fields.

Impact of climate change on insect biology, ecology, population dynamics, and pest management: A critical review

The purpose of this paper is to review and assess published literature on impact of climate change on insects. A systematic approach was used to accumulate research works of literature on “Impact of climate change on insects.” A total of forty-three (43) research papers published between the years 1908 to 2023 were accumulated and used for this review. Tables were used to present all results. A subjective approach was used to select the topics: impact of climate change and insects. In this paper, twenty-three (23) possible impacts of climate change on insects were evaluated and presented. Impact of extreme weather conditions on insects, challenges faced with pest management and strategies to mitigate the effects of climate change were also discussed. The published papers established that temperature, increasing level of carbon dioxide gas (CO2) in the atmosphere and precipitation all contribute to the changing climate that are affecting insect biodiversity, geographical distribution, behavioural preferences and pests’ outbreaks that are negatively impacting the agriculture sectors in many countries. This review highlights that more studies should be done in neotropical countries since there is a dearth and demand for research and published data in these biodiversity rich regions.

Monitoring the abundance of flying insects and atmospheric conditions during a 9-month campaign using an entomological optical sensor

Monitoring the dynamics of insect populations is key to assessing the impact of human activities on insect populations. However, traditional methodologies relying on physical traps have inherent limitations in accurately monitoring insect abundance. Here, we present findings from a 9-month campaign conducted in New Jersey, USA, utilizing a near-infrared optical sensor known as eBoss. From April to December 2022, the eBoss derived the aerial density (insect/m3) and biomass density (mg/m3) with a 1-min resolution from a total of 302,093 insect observations. The data collected were analyzed in relation to air temperature, relative humidity, and wind speed. The results revealed that the abundance of flying insects exhibited an initial increase from April to June, reaching a peak of 0.094 insect/m3 and 1.34 mg/m3, followed by a subsequent decline towards the end of the year. Our investigation showed a surge in insect abundance above 12.5 °C, with particularly high levels observed between 19 and 31 °C. The impact of relative humidity and wind speed on insect populations was also explored. Overall, this campaign demonstrated the efficacy of photonic sensors in gathering novel and extensive data for the field of entomology, paving the way for improved understanding and management of insect populations.

Estimation and analysis of insect population dynamics parameters via physiologically based models and hybrid genetic algorithm MCMC methods

Decision support systems are gaining importance in several fields of agriculture, forest, and ecological systems management. Their predictive potential, entrusted to mathematical models, is of fundamental importance to set up opportune strategies to control pests and adversities that may occur and that may seriously compromise the natural equilibria. Among the others, population dynamics is one of the crucial challenges in the field. Despite the scientific community in recent years providing valuable models that faithfully represent terrestrial arthropods populations, such as insects, one of the main concerns is still represented by the parameter estimation. Parameters, in fact, characterise the species and their estimation are often entrusted to dedicated laboratory experiments that require specific equipment and highly qualified personnel. In this study we propose a novel method to estimate the model parameters directly from field data, where experimental activities are less expensive and less time consuming. In this study we propose a combination of least squares methods via genetic algorithms to preliminary evaluate the best parameter values and Markov Chain Monte Carlo approach to obtain their distribution. The algorithm has been tested in the special case of Drosophila suzukii, to quantify part of the parameters of an almost validated model in two steps: i) a first pseudo-validation using perturbed numerical solutions, and ii) a validation using real field data. The results highlighted the potentialities of the algorithm in estimating model parameters and opened several perspectives for further improvements from both the computational and experimental point of view.

Quantifying long-distance dispersal of an outbreaking insect species using trap capture data and phenology

Long-distance dispersal plays an important role in insect population dynamics and is a key factor in insect outbreaks. However, accurately measuring the dispersal distance of insect species can be challenging. We present a simple and reliable method to quantify dispersal capacity using insect phenology and time-series of field-capture data. This open-source method is developed in R and tested using data collected on the eastern spruce budworm (Choristoneura fumiferana). Empirical data were collected in the summer of 2014 in Québec, in forest areas defoliated during the ongoing outbreak. Sampling dates were informed by BioSIM phenological models and government of Canada weather data where adult moths were sampled before, during, and after expected flying periods. A sensitivity analysis showed that the uncertainty of these models due to weather station interpolation did not affect general trends. Individuals sampled outside of their expected phenological window were assumed to be migrants. Pairwise Euclidean distances were measured between the sampling locations of these migrants and all potential areas of origin as predicted by BioSIM at the time of their sampling. The shortest distances were then selected to generate dispersal kernels. According to the dispersal kernels derived using this method, most flying individuals captured outside of their phenological window travelled up to 450 km, matching previous work on eastern spruce budworm dispersal. Here, we were able to demonstrate that with known phenology of a species and relatively simple to collect data (presence of flight capable individuals), it is possible to characterize insect dispersal using a relatively simple algorithm and spatial model. This method can be easily applied to other outbreaking species and used to inform management decisions in a variety of systems where outbreaks represent a risk to resources of interest.

The influence of habitat properties on sex determination in cavity-nesting Hymenoptera

Unravelling the relationships between insect population dynamics and habitat properties is often complex. Established theoretical concepts, which predict an influence of available resources on sex determination, have often not been tested with quantitative field data. Cavity-nesting Hymenoptera are suitable to assess the influence of habitat properties on reproductive parameters, as haplodiploidy enables direct responses to local conditions. We hypothesize that with increasing resource availability, the population sex ratio (share of females per site), sex allocation preference per individual offspring (the probability of producing either a male or a female offspring per brood cell) and resource allocation per individual offspring will be favouring towards females. We sampled offspring of Osmia cornuta, Osmia caerulescens and Trypoxylon figulus and their resource provisions using trap nests on 30 study sites in an agricultural landscape in southwest Germany, from March to August 2020. The potential influence of resource availability, landscape variables, temperature, seasonal progression, and nesting opportunities on sex and resource provisions was tested. Population sex ratio was not related to habitat properties. Sex allocation preference in the three species, however, depended on several variables including cavity size and seasonal progression, with pronounced differences amongst species. Individual resource provisioning mainly differed between sexes, as male larvae received less provisions than female larvae. As there was no influence of resource availability, we conclude that the sex ratio of established populations was balanced at the selected study sites by available resources in the landscape. At the individual scale, sex and resource allocation were influenced in species-specific ways. As such, sex determination and resource allocation are essential life history properties of sexually reproducing organisms.

Seasonal diversity and dynamics of entomofauna associated with the decomposition of pig (Sus scrofa domesticus L.) carcasses in a Peri-urban area of Central Burkina Faso, West Africa.

This study aimed to determine the effects of seasons on the diversity and dynamics of insects associated with pig carrion in Gampela, Plateau Central Region, Burkina Faso, West Africa. Pig carcasses (Sus scrofa domesticus L.) were exposed in an open area to monitor their decomposition process and their colonization by insects during a warm and dry period (March-April 2015), a warm and wet period (August-September 2015) and a cool and dry period (December 2015-January 2016). Monitoring and entomological data collection occurred for 60days for each study period. The decomposition process always included five stages (fresh, bloating, putrefaction, postputrefaction, and skeletal), which varied in duration depending on the study period. In sum, 118,761 insects belonging to 4 orders, 12 families, 17 genera, and 21 species were collected during the three study periods, with approximately 61% of the individuals collected during the warm and wet period. The dynamics of insect populations associated with the pig carcasses included two peaks at each study period. Formicidae was the most abundant insect family in each study period, but Musca domestica was the most abundant species. The listed species were found to belong to four trophic groups with a predominance of predators/carnivores followed by necrophagous insects. The orders, families, and trophic groups reported in this study were significantly more abundant during the warm and wet period. The results show prospects for the use of Calliphoridae, Muscidae, and Dermestidae in criminal investigations, depending on seasonal variations in Sudano-Sahelian areas.

Post-glacial colonization of the Fennoscandian coast by a plant parasitic insect with an unusual life history.

Species that exhibit very peculiar ecological traits combined with limited dispersal ability pose a challenge to our understanding of ecological and evolutionary mechanisms. This is especially true when they have managed to spread over long distances, overcome physical barriers, and colonize large areas. Climate and landscape changes, trophic web relations, as well as life history all interact to shape migration routes and present-day species distributions and their population genetic structures. Here we analyzed the post-glacial colonization of northern Europe by the gall midge Contarinia vincetoxici, which is a monophagous parasite on the perennial herb White swallowwort (Vincetoxicum hirundinaria). This insect not only has a narrow feeding niche but also limited dispersal ability and an exceptionally long dormancy. Gall midge larvae (n = 329) were collected from 16 sites along its distribution range in Denmark, Sweden, and Finland. Using microsatellite loci and knowledge of the species and the regions' history, we investigated the role of landscape change, host plant distribution, insect population dynamics, and life history in shaping the population genetic structure of the insect. We devoted particular interest to the role of the insect's presumed poor dispersal capacity in combination with its exceptionally extended diapause. We found significant levels of local inbreeding (95% highest posterior density interval = 0.42-0.47), low-level within-population heterozygosity (mean H E = 0.45, range 0.20-0.61) with private alleles in all populations except two. We also found significant (p < .001) regional isolation-by-distance patterns, suggesting regularly recurring mainly short-distance dispersal. According to approximate Bayesian computations, C. vincetoxici appears to have colonized the study area via wind-aided flights from remote areas approximately 4600-700 years before present when the land has gradually risen above the sea level. Extremely long dormancy periods have allowed the species to "disperse in time", thereby aiding population persistence despite generally low census population sizes.

Spatiotemporal dynamics of forest insect populations under climate change.

Effects of climate on forest insect populations are complex, often involving drivers that are opposing, nonlinear, and nonadditive. Overall, climate change is driving an increase in outbreaks and range shifts. Links between climate and forest insect dynamics are becoming clearer; however, the underlying mechanisms remain less clear. Climate alters forest insect population dynamics directly through life history, physiology, and voltinism, and indirectly through effects on host trees and natural enemies. Climatic effects on bark beetles, wood-boring insects, and sap-suckers are often indirect, through effects on host-tree susceptibility, whereas climatic effects on defoliators are comparatively more direct. We recommend process-based approaches to global distribution mapping and population models to identify theunderlying mechanisms and enable effective management of forest insects.

Habitat Modification Alters Food Web Interactions with Focus on Biological Control of Aphids in Apple Orchards

To date, direct interactions between pests and natural enemies are often considered in biocontrol programs. Recently there has been an increase of evidence for the importance of third-party mediated indirect interactions in determining the population dynamics of insects. Predicting the strength of such interactions remains a central challenge in biocontrol assessments. Here, two field experiments were performed in two years to investigate to which extent Dysaphis plantaginea Passerini, Aphis pomi De Geer, and Myzus cerasi Fabricius might indirectly interact through shared natural enemies and ants. We first studied the population dynamics of target insects in isolated orchards of apples and cherries. Secondly, we investigated how the spatial coexistence of aphid-infested cherries can indirectly affect the population dynamics of apple aphids via natural enemies and ants. In the first experiment, nine parasitoid species were recorded on apple and cherry aphids, among them were three species in common. Six predatory families were found on cherry and apple aphids, while only one ant species, Lasius niger L., was found associating with these aphids. In the second experiment, temporal variation in the natural enemy-mediated apparent competition between M. cerasi and apple aphids was found. The cherry aphid is likely to be an important source of natural enemies that attack apple aphids early in the season. Significantly reduced numbers of ants associating with apple aphids in the intercropping habitat were found. Our results emphasize the importance of considering indirect interactions in the designing of pest management strategies.

Stage Specific Life Table of Rice Leaffolder, Cnaphalocrocis medinalis (Guen.) at Different Temperature Regimes

The change in air temperature will influence the insect behavior, physiology and population dynamics of insects as they are poikilothermic. Global temperature has increased by 1.09°C during 2001-2020 when compared to 1850-1900. It is projected that the temperature will further increase by 5.7°C under high emission scenario, if mitigation strategies are not adopted. Increase in temperature would affect the physiology and population dynamics of the insects. A study was undertaken to understand the effect of different temperature regimes on rice leaffolder. Survival fraction decreased with increasing temperatures as more successful development was at lower temperature regimes. Apparent mortality increased towards the higher temperature regimes as the insects cannot tolerate high temperature stress. The Mortality Survivor Ratio (MSR) revealed that the population increase would be more at higher temperature regimes as the MSR remained higher at higher temperature regimes. The Indispensable Mortality was lesser under higher temperature regimes as the number of adults emerged in the high temperature regime was less. Generally, K - values increased with increasing temperature. It indicates that the insects which happened to live under higher temperature regimes were reproduction oriented as most of the energy was spent in reproduction rather than for living longer time.

Spatio-Temporal Connectivity of the Long-Term Dynamics of the Forest Phyllophagus Insects’ Abundance

The study was conducted regarding the conjugation of the population dynamics of different forest insects species under different landscape conditions on the territory of the Krasnoturansky pine forest (South of the Krasnoyarsk Territory). The population dynamics conjugation indicates the presence of an ecological mechanism that leads to the coordination of the temporal series of different species’ population dynamics in one habitat or one species in different habitats. This means that using the conjugation indicators of insect dynamics one can indirectly assess the influence of various factors affecting these populations. To assess the spatio-temporal synchronization of the population dynamics of insects in different landscape conditions, the data of the phyllophagous insects counts for the period from 1979 to 2016 were used. According to the phases of dynamics, although the periods of cyclic fluctuations of phyllophages’ populations in different stows are close, the characteristics of the phyllophagous insects number dynamics still differ in both the absolute values and the phases of dynamics, even when the distance between the test sites is relatively small. The “memory” of the system, expressed in the order of the autoregressive model of the population dynamics, is fairly large for the studied complexes of phyllophagous species: the current value of the phyllophagous populations density can be influenced by the population density values from as far as four years before the counts. Such values of “memory” lead to an increase in the populations’ stability margin, and a decrease in the risks of developing insect outbreaks. The determination coefficients close to 1 for the phyllophages dynamics models in the stows of the Krasnoturansky pine forest indicate a weak influence of modifying factors (such as weather) on the population dynamics.

Habitats and parasitoid abundance influence spatial density dependence patterns, rendering an asilid fly as a potential biological controller of white grubs

The behavioral response of a parasitoid shows the effect on host parasitism patterns at a given host distribution. As a result, an increase or decrease in parasitism intensity according to local host densities is found. This relationship could be proportional, positive, or negative, as a consequence of host foraging.Mallophora ruficaudais a parasitoid fly that parasitizesCyclocephala signaticollisscarab beetle larvae. Females search and place egg clusters overground in open grasslands. Larvae actively search hosts underground following chemical cues arising from the host itself. The parasitism patterns are a result of this complex host-searching strategy that is shared between both stages of the fly. In this work, we carried out a study at four spatial scales in apiaries located in the Pampas region of Argentina. We aimed to assess the potential ofM. ruficaudaas a control agent of white grubs. We found that parasitism has an inverse density-dependent in relation to low female activity and a direct density-dependent in relation to high female activity at the larger spatial scale. We found an inverse density-dependent pattern at the intermediate spatial scale. Parasitism is inversely density-dependent at both smaller spatial scales, associated with oviposition substrate availability and distance. Additionally,M. ruficaudadoes not select the oviposition substrates according to the abundance ofC. signaticollisinhabiting underground. We determined thatM. ruficaudacould act as a natural biological controller ofC. signaticollis. This work shows the importance of a proper scale for the analysis of factors that influence population dynamics of entomophagous insects and for evaluating their potential as biological control agents, and how environmental characteristics mold the parasitism patterns of this dipteran parasitoid.

Temperature-dependent development of Agrotis ipsilon (Lepidoptera: Noctuidae) and its stage transition models

The black cut worm Agrotis ipsilon (Hufnagel) is a destructive crop pest worldwide and a typical cut worm damaging plant parts below the soil surface, which requires a thorough phenological prediction of the target stage for proper management. Temperature is an essential factor affecting the phenology and dynamics of insect populations. So, this study was conducted to evaluate the temperature-dependent development of A. ipsilon fed on Kimchi cabbage (Brassica campestris) in a wide range of temperatures (10 to 40 ℃) in the laboratory. The linear and nonlinear relationship between temperature and development rate (1/development time) was analyzed. The lower threshold temperatures (LT) for eggs, larvae, and pupae were estimated to be 12.1 °C, 9.6 °C, and 11.2 °C, respectively, with thermal constants (degree days for development completion) of 31.3, 342.2, and 181.3 DD at each stage, respectively. Additionally, the thermal constant for tracking the phenology of each stage was determined using a common LT of 10.4 ℃: 40.3 DD for eggs, 315.6 DD for larvae, and 199.6 DD for pupae. Consequently, we provided newly the stage transition models for all stages of A. ipsilon using two basic components of the nonlinear development rate and distribution models to simulate the proportion of individuals shifted from one stage to the next stage. These models in their current form will be useful for constructing a population model for A. ipsilon in the future. Furthermore, the variation in the development time of A. ipsilon reported in previous studies was discussed using 95% confidence limits of the estimated line of our nonlinear models.

Effect of Silicon Fertilization on Eggplant Growth and Insect Population Dynamics

Effect of Silicon Fertilization on Eggplant Growth and Insect Population Dynamics

Weather-Based Fruit Fly Population Dynamics Prediction Model for the Mid-Hills of Eastern Himalayan Region of India

Across the globe, it is widely observed that current change in climate or weather pattern has marked effect on insect population dynamics and behavior, though with varied aspects and intensity. Understanding the correlations of insect population dynamics with weather parameters is the fundamental first step in formulating an effective integrated pest management programme. In the major citrus growing mid-hill regions of Arunachal Pradesh, fruit fly, Bactrocera dorsalis, is one of the chief reasons for heavy loss leading to pre-harvest fruit drop in citrus. The current study aims to determine how changes in weather parameters influence the population dynamics of fruit flies and to develop an optimized weather-based population prediction model for fruit flies infesting citrus in the mid-hills of Arunachal Pradesh. The population was monitored through standard methyl eugenol para-pheromone traps and a model was developed using stepwise multiple regression technique. The study revealed that the population was highest during the fruit development and ripening stage and it was found that the number of flies per trap and meteorological parameters (temperature and humidity) is positively correlated with appreciable statistical significance. The optimized regression model was developed with variables temperature and humidity, and was found to be 79 percent accurate in the study site. This model will serve as an important tool in pre-estimation of the fruit fly population in the citrus growing mid-hills of Arunachal Pradesh and for formulation of effective preventive management strategies.

Natural Occurrence and Analysis of Nosema sp. Infection in the Adult Population of Western Bean Cutworm in Michigan.

An understanding of population dynamics and insect biology is important for effective crop management strategies. Biotic factors such as pathogens play a large role on the fitness and dynamics of insect populations. Microsporidia are obligate intracellular parasites that infect more than 150 insect species and range from sublethal and chronic to fast acting and deadly. The western bean cutworm, Striacosta albicosta (Smith) (Lepidoptera: Noctuidae), is a pest of both corn (Zea maize L. [Poales: Poaceae]) and dry beans (Phaseolus sp L. [Fabales: Fabaceae]) that is infected by a microsporidian parasite from the genus Nosema (Microsporidia: Nosematidae). Unfortunately, little is known about the interactions between the Nosema sp. (Microsporidia: Nosematidae) infecting the western bean cutworm and its prevalence and effects on the host population. This is especially true for the western bean cutworm population that has settled in the Great Lakes region over the last two decades. Using field caught samples and phase contrast microscopy, no consistent trends in pathogen load were observed over the course of the western bean cutworm flight season. A weak, but statistically significant relationship was observed between male body weight and pathogen load. Overall, we found a 100% prevalence of infection in the adult western bean cutworm population in Michigan.

Linking remotely sensed ecosystem resilience with forest mortality across the continental United States.

Episodes of forest mortality have been observed worldwide associated with climate change, impacting species composition and ecosystem services such as water resources and carbon sequestration. Yet our ability to predict forest mortality remains limited, especially across large scales. Time series of satellite imagery has been used to document ecosystem resilience globally, but it is not clear how well remotely sensed resilience can inform the prediction of forest mortality across continental, multi-biome scales. Here, we leverage forest inventories across the continental United States to systematically assess the potential of ecosystem resilience derived using different data sets and methods to predict forest mortality. We found high resilience was associated with low mortality in eastern forests but was associated with high mortality in western regions. The unexpected resilience-mortality relation in western United States may be due to several factors including plant trait acclimation, insect population dynamics, or resource competition. Overall, our results not only supported the opportunity to use remotely sensed ecosystem resilience to predict forest mortality but also highlighted that ecological factors may have crucial influences because they can reverse the sign of the resilience-mortality relationships.

Population dynamics of herbivorous insects in polluted landscapes.

Environmental pollution is one cause of insect decline in the Anthropocene, but the underlying mechanisms remain obscure due to a paucity of pollution-impact studies on insects that address density-dependent processes. Long data series (19-26 years) are available only for a few species monitored around two industrial polluters in north-western Russia. A particularly exciting current finding is that industrial pollution determines the relative strength of rapid (stabilising) and delayed (destabilising) density dependence operating on a herbivore population. Most studies address acute effects of traditional pollutants (e.g. sulphur dioxide and trace elements) and nitrogen deposition on agricultural pests, whereas the effects of realistic concentrations of ozone, particulate matter and emerging pollutants on insects feeding on noncultivated plants are unknown. The accumulated evidence remains insufficient to predict the effects of pollutants of global concern on the population dynamics of herbivorous insects.