Moth Abundance Research Articles

Saproxylic moths reveal complex within-group and group-environment patterns

We investigated saproxylic moths of the family Tineidae, a neglected group inhabiting wood-decaying fungi and dead wood, within the Bialowieza Primeval Forest in Poland. Study data were obtained from the collection of 280 fruiting bodies of wood-decaying fungi and the subsequent rearing of adults. Spatial and statistical distribution of saproxylic moths, relationship among species and the influence of environment reflected by interaction with tree and fungal species together with tree and stand level characteristics were studied. Fifteen species and 533 individuals of saproxylic moths were reared. The fungal species, number of fruiting bodies and standing position of a tree influenced species richness. Moth abundance was influenced by fungal species, coniferous trees, increasing tree diameter, number of fruiting bodies and brown rot. Moth abundance was also enhanced by standing dead trees located in managed forests with higher canopy closure. Analyses indicate that several moth species favor a particular rot type and that some fungi host a richer fauna than others. Furthermore, our results indicate mutually independent fungal colonization events by saproxylic moth species, and thus a possible mechanism exists for competition avoidance with other saproxylic moths. Saproxylic moths revealed complex within-group patterns that responded differently to environmental variables. Thus, potential conservation of these organisms requires various approaches including ecosystem management, especially in the context of addressing their diverse habitat requirements.

The dark side of street lighting: impacts on moths and evidence for the disruption of nocturnal pollen transport.

Among drivers of environmental change, artificial light at night is relatively poorly understood, yet is increasing on a global scale. The community-level effects of existing street lights on moths and their biotic interactions have not previously been studied. Using a combination of sampling methods at matched-pairs of lit and unlit sites, we found significant effects of street lighting: moth abundance at ground level was halved at lit sites, species richness was >25% lower, and flight activity at the level of the light was 70% greater. Furthermore, we found that 23% of moths carried pollen of at least 28 plant species and that there was a consequent overall reduction in pollen transport at lit sites. These findings support the disruptive impact of lights on moth activity, which is one proposed mechanism driving moth declines, and suggest that street lighting potentially impacts upon pollination by nocturnal invertebrates. We highlight the importance of considering both direct and cascading impacts of artificial light.

Estimation of the Predictive Ability of Ecological Models

The conventional criteria for predictive model selection do not indicate the absolute goodness of models. For example, the quantity of Akaike Information Criterion (AIC) has meanings only when we compare AIC of different models for a given amount of data. Thus, the existing criteria do not tell us whether the quantity and quality of data is satisfactory, and hence we cannot judge whether we should collect more data to further improve the model or not. To solve such a practical problem, we propose a criterion RD that lies between 0 and 1. RD is an asymptotic estimate of the proportion of improvement in the predictive ability under a given error structure, where the predictive ability is defined by the expected logarithmic probability by which the next dataset (2nd dataset) occurs under a model constructed from the current dataset (1st dataset). That is, the predictive ability is defined by the expected logarithmic probability of the 2nd dataset evaluated at the model constructed from the 1st dataset. Appropriate choice of error structures is important in the calculation of RD. We illustrate examples of calculations of RD by using a small dataset about the moth abundance.

The role of abiotic and biotic factors in determining coexistence of multiple pollinators in the yucca–yucca moth mutualism

The determinants of a species' geographic distribution are a combination of both abiotic and biotic factors. Environmental niche modeling of climatic factors has been instrumental in documenting the role of abiotic factors in a species' niche. Integrating this approach with data from species interactions provides a means to assess the relative roles of abiotic and biotic components. Here, we examine whether the high host specificity typically exhibited in the active pollination mutualism between yuccas and yucca moths is the result of differences in climatic niche requirements that limit yucca moth distributions or the result of competition among mutualistic moths that would co‐occur on the same yucca species. We compared the species distribution models of two Tegeticula pollinator moths that use the geographically widespread plant Yucca filamentosa. Tegeticula yuccasella occurs throughout eastern North America whereas T. cassandra is restricted to the southeastern portion of the range, primarily occurring in Florida. Species distribution models demonstrate that T. cassandra is restricted climatically to the southeastern United States and T. yuccasella is predicted to be able to live across all of eastern North America. Data on moth abundances in Florida demonstrate that both moth species are present on Y. filamentosa; however, T. cassandra is numerically dominant. Taken together, the results suggest that moth geographic distributions are heavily influenced by climate, but competition among pollinating congeners will act to restrict populations of moth species that co‐occur.

Patterns of an elevational gradient affecting moths across the South Korean mountains: effects of geometric constraints, plants, and climate

AbstractWe investigated elevational richness patterns of three moth groups (Erebidae, Geometridae, and Noctuidae) along four elevational gradients located on one northern and three southern mountains in South Korea, as well as the effects of plants and climatic factors on the diversity patterns of moths. Moths were collected with an ultraviolet light trap at 32 sites from May through October, 2013. Plant species richness and mean temperatures for January and June were acquired. Observed and estimated moth species richness was calculated and the diversity patterns with null models were compared. Species richness along four elevational gradients peaked at mid‐elevations, whereas deviations occurred at elevations below mid‐peak in the southern mountains and elevations higher than mid‐peak on the northern mountain. Species richness curves of three moth groups also peaked at mid‐elevations throughout South Korea. However, the species richness curves for Erebidae were positively skewed, indicating that a preference for lowlands, whereas curves of the Geometridae were negatively skewed, indicating a preference for highlands. The mid‐peak diversity pattern between plants and moths on the Korean mountains showed an elevational breadth that overlapped between 800 and 900 m. Multiple regression analysis revealed that plant species richness and January mean temperature significantly influenced moth species richness and abundance. The rapid increase in mean annual temperature in the Korean peninsula and the unimodal elevational gradients of moths across the country suggest that an uphill shift in peak optimum elevation and changes in the highest peak of the curve will occur in the future.

Climate association with fluctuation in annual abundance of fifty widely distributed moths in England and Wales: a citizen-science study

Variation in annual abundance of 50 widespread moths in England and Wales was assessed from the area under the log10(moth count + 1) versus time curve (abundance index) for adult moth count data reported between 2003 and 2013 to the UK and Ireland Garden Moth Scheme; a citizen science project. Associations between abundance index and the abundance index of the previous generation, with inward migration, and with UK Met Office data for rainfall, mean temperature and sunshine were sought by multiple linear regression. Sixty-eight generations from univoltine or bivoltine species were analysed with a median range in abundance index between equivalent generations of 98 %. Significant (P < 0.05) single or multiple relationships were identified for all species. In 66 of the 68 generations, there was an association to one or more climate variable, four to the previous generation, and one to a measure of inward migration. Most frequently, moth abundance was increased by colder winters, a warm and sunnier spring, and wetter summers, though contrary conditions favoured some species. The time period over which significant climate variables were operating included some that were effective on generations during the preceding season, over the winter, and before and during the adult flight season. A significant difference in frequency of the different climate variables was identified between life-cycle stages in the winter and between larval food plants during the spring and summer. Unknown factors driven by variations in climate were responsible for 72 % of the annual variance in moth abundance in urban gardens.

Are woodland creation schemes providing suitable resources for biodiversity? Woodland moths as a case study

Woodland, like many habitats throughout the world, has been severely affected by habitat loss and fragmentation. Woodland restoration programmes aimed at reversing habitat loss have been in place in many countries over the last 100 years. In particular, agri-environment schemes (AES) to increase the amount and quality of woodland on agricultural land have operated in Europe and Australia for decades (nearly 30 years in the United Kingdom). However, to date there has been very little assessment of their value to biodiversity. We assessed the potential benefits to biodiversity of woodlands planted during 1988–1991 under a woodland grant scheme (WGS in Scotland), according to local and landscape-level habitat characteristics. Specifically, we (1) performed a linear discriminant analysis to compare the characteristics of 24 WGS sites to those of more mature semi-natural woodlands (34 sites >60 years old), and (2) used existing information on the influence of woodland characteristics on a biologically diverse group (i.e. moths) to quantify the benefits of WGS sites to biodiversity. The creation of new WGS patches increased woodland extent and connectivity in the landscape; however, planting that took place adjacent to previously existing woodland did not usually increase connectivity. WGS sites were mainly composed by broadleaved native tree species, but non-native species were also present. In general, WGS sites had lower tree species richness, proportion of native trees, tree basal area and amount of understory, and higher tree densities and canopy cover than more mature semi-natural woodlands. Overall, WGS sites were predicted to have lower moth abundance and species richness than older semi-natural woodlands. However, the magnitude of these differences depended on the habitat specificity and dispersal abilities of different moth groups, suggesting that WGS sites are better at providing suitable resources for generalist species and for species less limited by dispersal. Our findings have important implications for the way in which current woodland creation and management schemes operate in many countries and suggest that: (1) the creation of new woodlands should focus on planting native species, (2) woodland creation schemes are likely to be more beneficial for biodiversity if certain management practices (e.g. thinning to enhance structural diversity and accelerate the transition to later successional stages) accompany the provision of these grants, and (3) spatially-targeted woodland creation would further increase the contribution of AES woodlands to enhance biodiversity.

A stepwise algorithm to detect significant time lags in ecological time series in terms of autocorrelation functions and ARMA model optimisation of pest population seasonal outbreaks

A central issue in population ecology is to determine the structure of negative feedback-density depend process which regulates population dynamics and seasonal fluctuations. In this work the incidence of population density dependences and seasonality was examined in fruit orchards of three closely related pest species (Adoxophyes orana, Anarsia lineatella and (Grapholita) Grapholitha molesta). Analysis included 13 moth population time series during 2003–2011. Additionally, considering that time lags and seasonality are fundamental characteristics of ecological organisation and pest management, the work aimed to introduce a step wise algorithm to detect significant population feedbacks, moth seasonality and population synchronisation of nearby locations. In the proposed procedure, each population-time series was first analysed on the basis of autocorrelation and partial autocorrelation. Moreover, assuming that each of the ecological variable, observed at successive time points, consist of a stochastic process, autoregressive moving average ARMA(p,q) models and seasonal autoregressive moving average models SARMA(p,q)x(P,Q) S were fitted on data. The Akaike information criteria was further used by the stepwise algorithm for parameter optimization and model improvement. Model construction is accompanied by a presentation of the fitting results and a discussion of the heuristic benchmarks used to assess the forecasting performance of the models. Life cycles of populations belonging to same species appeared to synchronise by terms of their autocorrelation functions. Delayed density dependence and order was in most cases of lag:1 and 2, while lag >3 was not found more frequently as expected by chance. In A. orana and A. lineatella moth species lag = 1 delayed density dependence was significantly more frequent and in particular in nearby locations. However, the structure of the fitted models varied with respect to species and observation region. In some cases, seasonal models were considered to be more accurate in simulating moth population dynamics. Finally, to provide means in forecasting moth emergence and abundance, utile in pest management, the models were trained using 2003–2009 data sets and their forecasting performance were validated for each case using data sets of 2010–2011. In most cases, the constructed stochastic linear autoregressive models simulated the population outbreaks very well. Describing and forecasting stochastic population fluctuations is a basic tenet of theoretical and applied ecology, while detecting the relative roles of exogenous and endogenous mechanisms can partly describe the phenomenological behavior of pest population time series data and improve pest management.

Community Patterns in Urban Moth Assemblages

ABSTRACT. In order to gain a better understanding of the effects of urbanization on insect biodiversity we compared moth assemblages between residential yards and urban woodlots in East Lansing, Michigan. We surveyed 36 sites over six trapping nights, for a total of 24 hours of nighttime light-trapping at each site. We captured over 2700 macromoth individuals and over 4000 micromoth individuals; more than 97% of macromoth individuals were identified to species. We analyzed differences in life history traits such as body size and feeding guild between residential moths and urban woodlot moths. Urban woodlots had a higher overall abundance of moths and higher species richness than residential yards. Residential yards were found to have a high proportion of “tourist species.” Urban woodlot moth species were significantly larger than residential moth species, leading us to hypothesize that larger moths may be more prone to predation in open habitats. The woodlot moth assemblage was also characterized by a hig...

Bottom-up impact of soils on the network of soil, plants, and moths (Lepidoptera) in a South Korean temperate forest

AbstractThe influence of soil properties on the diversity of plants and moths (Lepidoptera) were examined in two South Korean high mountain forest localities (Mount Hallasan and Mount Jirisan) and one seashore mountain forest locality (Mount Seungdalsan). Six sites at each locality were included in the study. Soil physical and chemical properties and plant data were obtained from 20×20 m quadrats at every moth sampling site. Moth community data were obtained from the 18 sites. Stepwise regression analysis identified total tree basal area and tree species richness as significant determinants of moth species richness, and plant diversity index as a significant determinant of moth abundance. Total tree basal area was closely related to organic matter (OM), clay content, NaCl concentration, and pH, and plant diversity was closely related to clay content. Nonmetric multidimensional scaling ordination between plant and moth species across 18 sites and 17 soil variables showed that soil fertility factors (OM, total nitrogen content, and cation exchange capacity) were major variables. Our results indicate that soil, plants, and moths communities in temperate forests form a close, interacting network that is primarily affected by the bottom-up impact of soil fertility.

The importance of natural habitats to Brazilian free-tailed bats in intensive agricultural landscapes in the Winter Garden region of Texas, United States

The conversion of natural lands to agriculture is a leading cause of the worldwide loss of biodiversity. In particular, cropland monocultures alter insect abundance and diversity compared to adjacent natural habitats. While agricultural lands can provide large numbers of insect pests as prey items to predators such as bats, insect pest population size vary greatly throughout growing seasons. This study assesses the importance of land use and corn earworm moth availability as spatial and temporal drivers of bat activity. We quantified spatial variation in land use patterns at fifteen sites located within the Winter Garden region in south central Texas and used bat detectors and insect pheromone traps to monitor nightly bat activity and corn earworm moth abundance across the landscape and throughout most of the year. Our temporal analyses show that bat activity was positively correlated with moth abundance, but only early in the growing season when moth abundance is at its peak. The key result from this study is a positive relationship between bat activity and natural habitat cover during late summer months, corresponding to periods of low moth abundance and a peak in bat activity. During the late summer period, bats were more active at sites containing a larger percentage of natural habitats than those containing a larger percentage of agricultural land. Our results strongly suggest that intensive agricultural practices create systems providing bats with inconsistent resource supply, but the persistence of natural habitats provides consistency in food supply though time. Taken together, these findings illustrate the importance of protecting and restoring natural habitats for the conservation for bats and the pest-suppression services they provide in agricultural ecosystems.

Pest control service provided by bats in Mediterranean rice paddies: linking agroecosystems structure to ecological functions

Pest control through integrated pest management systems stands as a very convenient sustainable hazard-free alternative to pesticides, which are a growing global concern if overused. The ability of the soprano pipistrelle bat (Pipistrellus pygmaeus) to control the rice borer moth (Chilo supressalis), which constitutes a major pest of rice around the world, was studied in the Ebre Delta, Northeastern Iberia. Evidence was found on the ability of this particular bat species to control borer infestations: (a) the moth was consumed during at least the last two peaks of the moth activity, when most crop damage is done; (b) the activity of bats significantly increased with moth abundance in the rice paddies; (c) the pest levels have declined in the study area (Buda Island, Eastern Ebre Delta) after the deployment of bat boxes and their subsequent occupation by soprano pipistrelles. The value of the ecosystem service provided by bats was estimated at a minimum of 21€ per hectare, equivalent to the avoided pesticide expenditure alone. We suggest that this natural service can be enhanced by providing bat populations with artificial roosts in rice paddies were some key ecosystem features are present.

Timing is Everything: Temporal Variation in Floral Scent, and its Connections to Pollinator Behavior and Female Reproductive Success in Phlox divaricata

The study of floral traits and pollination for the plant genus Phlox has historically been focused on either surveys of general pollinator affinities across the genus or detailed research on pollinator-mediated evolution of floral color in a single species (Phlox drummondii). The purpose of this study was to explore a different kind of trait – floral scent – in Phlox divaricata, a species noted for its strong scent. Specifically, we predicted the diel emission patterns of floral scent might covary with the daily abundance of diurnal moths, identified in a previous study as the most important pollinators in a Konza Prairie population of P. divaricata. Consistent with this prediction, we documented peaks in median floral scent emissions at 1000–1200 and 1930–2130, coinciding with peaks in moth visitation and resulting seed production. Two groups of scent compounds contributed to this pattern; linalool and its associated lilac aldehyde/alcohol compounds (especially lilac aldehyde B) contributed a greater proportion to scent at 1000–1200, while aromatic compounds (including benzaldehyde and benzyl acetate) contributed a greater proportion to scent at 1930–2130 and other afternoon time periods. These volatiles are known floral attractants for several lepidopteran pollinators, including noctuid moths. However, there is an additional peak in pollinator abundance (Hemaris diurnal hawkmoths) and seed set at a time when scent production is relatively low (1400–1600) suggesting additional factors mediate both pollinator behavior and floral volatile emissions. Future studies of P. divaricata should test for the presence of destructive floral enemies that might be attracted by floral volatiles during mid-afternoon periods, as well as the importance of visual floral traits (color, shape) in attracting diurnal moths, an important functional group of pollinators that has received minimal attention in North America.

Weather-driven dynamics in a dual-migrant system: moths and bats.

Animal migrations generate large spatial and temporal fluctuations in biomass that provide a resource base for many predator-prey interactions. These interactions are often driven by continent-scale weather patterns and are difficult to study. Few studies have included migratory animals on more than a single trophic level or for periods spanning multiple entire seasons. We tracked migrations of three species of agricultural pest noctuid moths over the 2010-2012 autumn seasons as the moths travelled past a large colony of migratory Brazilian free-tailed bats (Tadarida brasiliensis) in Texas. Increases in moth abundance, mass of bats and duration of bat activity outside of the cave were correlated with passage of cold fronts over the study area and related increases in northerly wind. Moth responses to weather patterns varied among species and seasons, but overall moth abundances were low in late summer and spiked after one or more cold front passages in September and October. Changes in bat mass and behaviour appear to be consequences of bat migration, as cave use transitioned from summer maternity roost to autumn migratory stopover sites. Weather-driven migration is at considerable risk from climate change, and bat and moth responses to that change may have marked impacts on agricultural systems and bat ecosystem services.

Stacking the odds: light pollution may shift the balance in an ancient predator–prey arms race

Summary Artificial night lighting threatens to disrupt strongly conserved light‐dependent processes in animals and may have cascading effects on ecosystems as species interactions become altered. Insectivorous bats and their prey have been involved in a nocturnal, co‐evolutionary arms race for millions of years. Lights may interfere with anti‐bat defensive behaviours in moths, and disrupt a complex and globally ubiquitous interaction between bats and insects, ultimately leading to detrimental consequences for ecosystems on a global scale. We combined experimental and mathematical approaches to determine effects of light pollution on a free‐living bat–insect community. We compared prey selection by Cape serotine bats Neoromicia capensis in naturally unlit and artificially lit conditions using a manipulative field experiment, and developed a probabilistic model based on a suite of prey‐selection factors to explain differences in observed diet. Moth consumption by N. capensis was low under unlit conditions (mean percentage volume ± SD: 5·91 ± 6·25%), while moth consumption increased sixfold (mean percentage volume ± SD: 35·42 ± 17·90%) under lit conditions despite a decrease in relative moth abundance. Predictive prey‐selection models that included high‐efficacy estimates for eared‐moth defensive behaviour found most support given diet data for bats in unlit conditions. Conversely, models that estimated eared‐moth defensive behaviour as absent or low found more support given diet data for bats in lit conditions. Our models therefore suggest the increase in moth consumption was a result of light‐induced, decreased eared‐moth defensive behaviour. Policy implications. In the current context of unyielding growth in global light pollution, we predict that specialist moth‐eating bats and eared moths will face ever‐increasing challenges to survival through increased resource competition and predation risk, respectively. Lights should be developed to be less attractive to moths, with the goal of reducing effects on moth behaviour. Unfortunately, market preference for broad‐spectrum lighting and possible effects on other taxa make development of moth‐friendly lighting improbable. Mitigation should therefore focus on the reduction of temporal, spatial and luminance redundancy in outdoor lighting. Restriction of light inside nature reserves and urban greenbelts can help maintain dark refugia for moth‐eating bats and moths, and may become important for their persistence.

Guild-specific responses of forest Lepidoptera highlight conservation-oriented forest management – Implications from conifer-dominated forests

The loss of biodiversity in forest ecosystems has led to a discussion on conservation-oriented forest management, particularly in intensively managed coniferous forest of the northern hemisphere. Two conservation-oriented management strategies, namely advancement of multi-layered forests stands and benign neglect of naturally disturbed stands, are currently being promoted over conventional management strategies of single-layered stands and salvage logging after natural disturbances. However, the effect of these conservation-oriented strategies on nocturnal Lepidoptera has not yet been assessed, despite the high contribution of this order to biodiversity. Here we used full assemblage data of forest-dwelling micro-moths and macro-moths to compare species densities and relative abundance of moths of the larval feeding guilds in single-layered and multi-layered stands, and in naturally disturbed salvaged or unsalvaged stands. We demonstrate that forest moth assemblages are sensitive to conservation-oriented forest management strategies. The relative abundance of moths of the saproxylic and detritus-feeding larval guilds was higher in naturally disturbed unsalvaged stands and in multi-layered stands, whereas that of moths of the moss-feeding larval guild was lower in multi-layered stands. These results corroborate the benefit of a benign-neglect strategy in the management of naturally disturbed stands in conserving saproxylic and detritus-feeding moths and in using natural disturbance to guide the enhancement of stand complexity. Our results demonstrate both the power of functional approaches to reveal slight changes in species communities and the importance of including micro-moths (a frequently disregarded group) in studies aimed at developing management implications for forest managers.

Spatial and temporal dynamics of Aroga moth (Lepidoptera: Gelechiidae) populations and damage to sagebrush in shrub steppe across varying elevation.

Spatial and temporal variation in the density of the Aroga moth, Aroga websteri Clarke (Lepidoptera: Gelechiidae), and in its damage to its host plant, big sagebrush (Artemisia tridentata Nuttall), were examined at 38 sites across a shrub steppe landscape in mountain foothills of northern Utah. Sites were sampled from 2008 to 2012 during and after an outbreak of the moth, to assess whether and how local variation in moth abundance, survivorship, and damage to the host plant was accounted for by sagebrush cover, elevation, slope, aspect, or incident solar radiation. As moth numbers declined from a peak in 2009, individual sites had a consistent tendency in subsequent years to support more or fewer defoliator larvae. Local moth abundance was not correlated with sagebrush cover, which declined with elevation, and moth survivorship was highest at intermediate elevations (1,800-2,000 m). North-facing stands of sagebrush, characterized by lower values of incident solar radiation, were found to be especially suitable local habitats for the Aroga moth, as reflected in measures of both abundance and feeding damage. This high habitat suitability may result from favorable microclimate, both in its direct effects on the Aroga moth and in indirect effects through associated vegetative responses. North-facing sites also supported taller and more voluminous sagebrush plants in comparison to south-facing sites. Thus, the moth is reasonably predictable in the sites at which it is likely to occur in greatest numbers, and such sites may be those that in fact have most potential to recover from feeding damage.

Numerical and functional responses of forest bats to a major insect pest in pine plantations.

Global change is expected to modify the frequency and magnitude of defoliating insect outbreaks in forest ecosystems. Bats are increasingly acknowledged as effective biocontrol agents for pest insect populations. However, a better understanding is required of whether and how bat communities contribute to the resilience of forests to man- and climate-driven biotic disturbances. We studied the responses of forest insectivorous bats to a major pine defoliator, the pine processionary moth pityocampa, which is currently expanding its range in response to global warming. We used pheromone traps and ultrasound bat recorders to estimate the abundance and activity of moths and predatory bats along the edge of infested pine stands. We used synthetic pheromone to evaluate the effects of experimentally increased moth availability on bat foraging activity. We also evaluated the top-down regulation of moth population by estimating T. pityocampa larval colonies abundance on the same edges the following winter. We observed a close spatio-temporal matching between emergent moths and foraging bats, with bat activity significantly increasing with moth abundance. The foraging activity of some bat species was significantly higher near pheromone lures, i.e. in areas of expected increased prey availability. Furthermore moth reproductive success significantly decreased with increasing bat activity during the flight period of adult moths. These findings suggest that bats, at least in condition of low prey density, exhibit numerical and functional responses to a specific and abundant prey, which may ultimately result in an effective top-down regulation of the population of the prey. These observations are consistent with bats being useful agents for the biocontrol of insect pest populations in plantation forests.

Incomplete control of the diamondback moth, Plutella xylostella, by the parasitoid Cotesia vestalis in a cabbage field under tropical conditions

Immature Plutella xylostella (Lepidoptera: Plutellidae) and parasitoids were sampled for 39 months in an unsprayed cabbage field near Cotonou, Benin, to determine how and when host-parasitoid interactions influence the population dynamics of the moth in a tropical environment. Eighty-three samples were taken at approximately two-week intervals. There were no seasonal patterns in the abundance of immature moths, which was not correlated with weather variables, although heavy rainfall during the principal rainy season may have temporarily affected the population. The host-parasitoid system consisted almost exclusively of P. xylostella and its larval parasitoid Cotesia vestalis (Hymenoptera: Braconidae), both species occurring at similar levels of abundance (on average 7.5 ± 0.3 and 7.2 ± 0.3 individuals per plant, respectively). The tendency for host-parasitoid dynamics to cycle was apparent in the field. P. xylostella and C. vestalis showed coupled oscillations in abundance, with a time lag of about two weeks between host and parasitoid peaks. High parasitoid abundance resulted in significant decreases in moth abundance over several weeks. However, the parasitoid population in turn decreased, could not prevent the moth from rebounding, and there was no stable control of the pest. We conclude that under tropical conditions in which P. xylostella populations grow rapidly, combined with a high probability of recolonization from surrounding areas, biological control by a well-established specialist parasitoid reaches its limits and additional control measures are necessary.

Spatial and temporal determinants of golden sun moth Synemon plana distribution

AbstractIn this study we examined the spatial and temporal variation in a population of the critically endangered golden sun moth Synemon plana over four years in a conservation reserve in south‐eastern Australia. We found golden sun moth spatial distribution and abundance dramatically declined from a peak in extent and abundance from 2008–2009 to 2011–2012 due to a shift from drought to above average rainfall. Autoregressive correlative models indicated that a northerly aspect and landscape position were key predictors of abundance over time, and golden sun moth distribution shifted from wet to dry locations in the landscape. We conclude that: our data provide a counterpoint to conclusions that golden sun moth has been known to persist in very small areas and suggest that distribution can change quite markedly (from large connected populations to small patches) at a local scale, and this will be due to dispersal and survivorship; the variability in the data may have implications for adequate detection of the species over time, especially when populations have contracted and species have a naturally restricted activity and breeding period; and long‐term weather patterns and landscape configuration (aspect, wet or dry position) interact to significantly affect local distribution and abundance over time. This has implications for the species under global change; increased variability in rainfall, temperature, productivity and exotic pasture growth may all alter and interact to either reduce or enhance persistence of golden sun moth populations over time.