Multivoltine Species Research Articles

Foliage-browsing Lepidoptera (Insecta) in deciduous forests of Ukraine for the last 70 years

As insect development depends on temperature, so the change in biology, behavior habits, frequency, and severity of outbreaks of foliage-browsing insects considered pests can follow the climate change. The reactions of species to the same climate changes can be specific, therefore, an unpredictable change in their ratio in the community will affect the consequences of climate change.
 The details of such changes must be studied to quantitatively assess future trends and the threats to deciduous forests. The aim of this research was to evaluate the representation in deciduous forests the foliage-browsing lepidopterous insects if different groups of size, lifestyle, voltinism, trophic relations, and ability to mass propagation in different periods of assessment for recent 70 years.
 In the analysis, we used a list of 118 lepidopterous species of foliage-browsing insects of deciduous forests, compiled on the basis of archival data from 1940–1975, and in the course of our own field research from 1975 to the present in the forests of Ukraine. Following trends were expected to be confirmed for these time intervals: to increase the number of species of small size, the number of species with hidden lifestyle, multivoltine species, polyphagous species, and so-called indifferent species. For each species, all these parameters were identified and proportions of species of each category for certain time intervals (1940–1950, 1960–1970, 1980–1990, and 2010–2020). Their distribution for size, voltinism, lifestyle, trophic features, and outbreak potential at these time intervals was compared using χ2-test.
 Among lepidopterous foliage-browsing insects of deciduous forests of Ukraine, the increase for recent 70 years was proved for the proportion of indifferent species (do not able to mass propagation), small species (with wingspan below 20 mm), as well as species with hidden (leaf-miners) and semi-hidden lifestyle (leaf-rollers). All trends are expressed the most obviously in 1940–1950 and further periods. The hypothesis about decrease the proportion of the univoltine and monophagous species for this period is not supported statistically.

Inter-sexual and inter-generation differences in dispersal of a bivoltine butterfly

In organisms with discrete generations such as most insects, life-history traits including dispersal abilities often vary between generations. In particular, density-dependent differences in dispersal of bi- and multivoltine species may be expected because subsequent generations are usually characterized by a drastic increase in individual abundance. We investigated the inter-sexual and inter-generation differences in dispersal of a bivoltine butterfly, Lycaena helle, testing the following hypotheses: (1) male emigration is higher in spring generation, as males are prone to leave their natal habitat patches when the density of mating partners is low; (2) female emigration is higher in summer generation, when it helps to reduce intraspecific competition between offspring. The outcome of our analyses of dispersal parameters showed that females of the summer generation emigrated from their natal patches considerably more often than those of the spring generation, whereas an opposite trend was detected in males. These findings offer a novel perspective for our understanding of the advantages of voltinism for metapopulation functioning. The spring generation dispersal mainly improves the random mating opportunities favoured by the increase in male emigration. In turn, the dispersal of females of the summer generation appears the key to long-term metapopulation persistence.

The hotter the better? Climate change and voltinism of Spodoptera eridania estimated with different methods

Substantial increases in global temperature are projected for the coming decades due to climate change. Considering that temperature has a strong influence on insect voltinism (i.e., number of generations per year), climate change may affect the population growth of insects, with potential consequences for food production. The southern armyworm, Spodoptera eridania, is a multivoltine species native to the American tropics that causes severe damage to several crops. In this context, this study evaluated the impacts of climate change on the voltinism of S. eridania in southern Brazil. Current and future daily temperature data were combined with non-linear and degree-day models to estimate the voltinism of this pest. Under current climate conditions, the voltinism of S. eridania ranged from 2.9 to 9.2 generations, with fewer cohorts in colder regions and more in warmer ones. A higher number of generations was predicted for the future climate scenarios evaluated, reaching up to 12.1 annual generations in certain regions by 2070. Most of the variation in voltinism was explained by location (87.7%) and by the interaction between location and mathematical model (3.0%). The degree-day model estimated an increase in the number of generations in the entire study area, while the non-linear model predicted a decrease in voltinism in the warmer regions under future climate change scenarios. Given these differences between the predictions provided by degree-day and non-linear models, the selection of the best method to be used in climate change studies should be carried out carefully, considering how species respond to temperature. A considerable increase in the number of generations of S. eridania was projected for most of the study area under the climate change scenarios evaluated, suggesting a possible rise in pest incidence levels in the coming decades.

Species traits affect phenological responses to climate change in a butterfly community

Diverse taxa have undergone phenological shifts in response to anthropogenic climate change. While such shifts generally follow predicted patterns, they are not uniform, and interspecific variation may have important ecological consequences. We evaluated relationships among species’ phenological shifts (mean flight date, duration of flight period), ecological traits (larval trophic specialization, larval diet composition, voltinism), and population trends in a butterfly community in Pennsylvania, USA, where the summer growing season has become warmer, wetter, and longer. Data were collected over 7–19 years from 18 species or species groups, including the extremely rare eastern regal fritillary Speyeria idalia idalia. Both the direction and magnitude of phenological change over time was linked to species traits. Polyphagous species advanced and prolonged the duration of their flight period while oligophagous species delayed and shortened theirs. Herb feeders advanced their flight periods while woody feeders delayed theirs. Multivoltine species consistently prolonged flight periods in response to warmer temperatures, while univoltine species were less consistent. Butterflies that shifted to longer flight durations, and those that had polyphagous diets and multivoltine reproductive strategies tended to decline in population. Our results suggest species’ traits shape butterfly phenological responses to climate change, and are linked to important community impacts.

Nesting Biology of the Solitary Wasp Pisoxylon amenkei (Hymenoptera, Crabronidae, Trypoxylini) in a Neotropical Hotspot of Southern Brazil.

Pisoxylon amenkei is a specie of solitary wasp that builds its nests in pre-existing cavities; it has only been recorded nesting in the Araucaria forest, one of the Atlantic forest phytophysiognomies and a biodiversity hotspot. So far, the only information on the biology of the genus Pisoxylon is based on one species. In addition, the genus has many similarities to Trypoxylon, showing an increased need for studies on the biology of these species of wasps. In the present study, we introduce unpublished information about Pisoxylon amenkei nesting biology and described many aspects of its natural history. Research was carried out between August 2017 and August 2019, in a rural area of Guarapuava municipality, Paraná, Brazil. Pisoxylon amenkei nested only in fragmented parts of Araucaria forest, during summer and autumn. It is a multivoltine species, and thus remains in diapause, in the pre-pupa phase during winter and spring. Their nests had an interior design similar to that of Pisoxylon xanthosoma and some Trypoxylon species, such as Trypoxylon lactitarse and Trypoxylon agamenon. Moreover, the sex ratio of P. amenkei was 1: 1, which can be linked to an equal cost in the production of females and males. Like other species of Pisoxylon, P. amenkei nests primarily in forest areas. In southern Brazil, it nests in fragments of Araucaria forest, which are threatened. Therefore, more efforts are needed to preserve these remaining fragments; a failure to do so could have devastating results, considering the number of threatened species that these forests house. We conclude that further studies should focus on the phylogeny of the group and use molecular analyses to clarify the hypothesis of Antropov (1998), that Pisoxylon should be classified as a subgenus of Trypoxylon.

Summer seasonal prevalence of Culicoides species from pre-alpine areas in Switzerland.

Biting midges (Diptera: Ceratopogonidae) are arthropods of veterinary importance since they can transmit pathogens and cause severe allergic dermatitis in horses. Very little is known about the species at higher altitudes and their seasonal dynamics. In this work, adult Culicoides were collected with Onderstepoort UV-light suction traps (OVI) from June to September 2016 at two areas situated at around 1600 m asl (pre-alpine area I, 2 farms) and 2030 m asl (pre-alpine area II, 1 farm) in the Canton of Grisons (south-east Switzerland). Overall, 17 049 Culicoides were collected, including 871 parous females. A total of 50 individuals/trap/night (n=1050) were identified to species (17 species) by matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS) or by polymerase chain reaction (PCR) and sequencing. The remaining 15 128 Culicoides were classified to species groups' level. Culicoides obsoletus (Meigen, 1818), a multivoltine species, was mainly present at 1600 m asl, whereas at high altitudes (2030 m asl), C. grisescens Edwards, 1939 I&II were the most abundant species. In particular, C. grisescens II, which seems to be univoltine, occurred later in the season but significantly increasing over time. Species diversity was higher at pre-alpine I area (n=16 species) compared to pre-alpine II (n=10 species).

Pest categorisation of Diabrotica undecimpunctata howardi.

The EFSA Panel on Plant Health performed a pest categorisation of Diabrotica undecimpunctata howardi (Coleoptera: Chrysomelidae) for the EU. This subspecies occurs in North and Central America. Adults oviposit on annual plants in the families Asteraceae, Chenopodiaceae, Cucurbitaceae, Fabaceae, Poaceae, Polygonaceae and Solanaceae. Adults feed on tender plant parts in hosts in 40 additional botanical families. Preimaginal development takes place on the roots of the host plant, where larvae feed and pupate. D. undecimpunctata howardi is a multivoltine species. Overwintering adults, which may enter a facultative diapause, abandon crops in autumn and reinvade them in spring. D. undecimpunctata howardi is not known to occur in the EU and is regulated in Annex IIA of Commission Implementing Regulation 2019/2072. This species is a competent vector of Erwinia tracheiphila (Smith) Bergey et al., which can cause bacterial wilt, a serious disease of cucurbits. The bacterium, which is restricted to temperate midwestern and eastern North America, is not regulated in the EU. Within Commission Implementing Regulation 2019/2072, potential entry pathways for D. undecimpunctata howardi, such as Asteraceae, Poaceae and Solanaceae plants for planting with foliage and soil/growing medium, and soil/growing media by themselves can be considered as closed. However, plants for planting of the families Chenopodiaceae, Cucurbitaceae, Fabaceae and Polygonaceae are not specifically regulated. Should D. undecimpunctata howardi arrive in the EU, climatic conditions and availability of susceptible hosts provide conditions suitable for establishment and further spread. Economic impact is anticipated in maize and outdoor cucurbit production. D. undecimpunctata howardi satisfies the criteria that are within the remit of EFSA to assess for this species to be regarded as a potential Union quarantine pest. This species does not meet the criteria of being present in the EU, nor plants for planting being the main pathway for spread, for it to be regarded as a potential regulated non‐quarantine pest.

Changes in flight period predict trends in abundance of Massachusetts butterflies.

Phenological shifts are well-documented in the ecological literature. However, their significance for changes in demography and abundance is less clear. We used 27years of citizen science monitoring to quantify trends in phenology and relative abundance across 89 butterfly species. We calculated shifts in phenology using quantile regression and shifts in relative abundance using list length analysis and counts from field trips. Elongated activity periods within a year were the strongest predictor of increases in relative abundance. These changes may be driven in part by changes in voltinism, as this association was stronger in multivoltine species. Some species appear to be adding a late-season generation, whereas other species appear to be adding a spring generation, revealing a possible shift from vagrant to resident. Our results emphasise the importance of evaluating phenological changes throughout species' flight period and understanding the consequences for such climate-related changes on viability or population dynamics.

Population dynamic of <i>Diclidophlebia irvingiae</i>, Burckhardt et al. (Hemiptera: Psylloidea), psyllid pest of <i>Irvingia gabonensis</i> Baill (Irvingiaceae, Rutales) in Bamenda, North-West region of Cameroon

Diclidophlebia irvingiae is a sap-sucking insect of Irvingia gabonensis inducing important damage to its host plant which has medicinal and nutritional importance in Africa particularly in Cameroon. The aim of the survey was to study numerical variation of the pest during the year and impact of biotic and abiotic factors on numerical variation. The study was carried in Bamenda from March 2018 to March 2019 where larvae and adults of D. irvingiae were collected monthly. The study permitted us to record 3290 individuals 1341 males, 1396 females and 553 larvae. Population fluctuation of the pest during the year showed five periods of individual outbreak corresponding to the generation number of the pest. As most tropical and sub-tropical psyllid species D. irvingiae is a multivoltine species with five annual generations. The outbreak periods depend principally on the phenology of host plant. The statistical test showed that the numerical individual variation of D. irvingiae is not directly related to climatic factors because they do not show significant probability.Keywords: Impact, Biotic, Abiotic, Factors, Insect, Faunistic.

Tracking Community Timing: Pattern and Determinants of Seasonality in Culicoides (Diptera: Ceratopogonidae) in Northern Florida.

Community dynamics are embedded in hierarchical spatial–temporal scales that connect environmental drivers with species assembly processes. Culicoides species are hematophagous arthropod vectors of orbiviruses that impact wild and domestic ruminants. A better sense of Culicoides dynamics over time is important because sympatric species can lengthen the seasonality of virus transmission. We tested a putative departure from the four seasons calendar in the phenology of Culicoides and the vector subassemblage in the Florida panhandle. Two years of weekly abundance data, temporal scales, persistence and environmental thresholds were analyzed using a tripartite Culicoides β-diversity based modeling approach. Culicoides phenology followed a two-season regime and was explained by stream flow and temperature, but not rainfall. Species richness fit a nested pattern where the species recruitment was maximized during spring months. Midges were active year-round, and two suspected vectors species, Culicoides venustus and Culicoides stellifer, were able to sustain and connect the seasonal modules. Persistence suggests that Orbivirus maintenance does not rely on overwintering and that viruses are maintained year-round, with the seasonal dynamics resembling subtropical Culicoides communities with temporal-overlapping between multivoltine species. Viewing Culicoides-borne orbiviruses as a time-sensitive community-based issue, our results help to recommend when management operations should be delivered.

Biology, ecology, and impact of Cryptonevra nigritarsis Duda, a potential biological control agent against the giant reed Arundo donax

Arundo donax (L.), commonly known as giant reed, is an invasive weed in riparian habitats worldwide. The chloropid fly Cryptonevra nigritarsis Duda infests young shoots of A. donax in its native range and has been considered for a long time as a potential biological control agent. This study was designed to investigate the biology and field ecology of C. nigritarsis and document its impact on A. donax. Populations of A. donax were monitored in ten field sites for a full year and sticky traps were used to assess C. nigritarsis abundance. Young A. donax shoots with signs of infestation were dissected monthly, and a DNA-based diagnosis method was developed to assess the prevalence of C. nigritarsis among the larvae and pupae collected. Finally, a manipulative experiment was performed to evaluate the impact of water stress on A. donax vulnerability to C. nigritarsis. Results showed that C. nigritarsis is likely to be a multivoltine species overwintering mainly as pupa. Only 6.3% of the A. donax shoots monitored were infested and the overall prevalence of C. nigritarsis among the larvae and pupae collected was 54.3%. C. nigritarsis was found in shoots of all diameters and was the predominant species in very thin and very thick shoots. Thicker shoots had a greater probability of infestation by chloropid flies in general. The manipulative experiment showed that mortality of A. donax shoots in the presence of C. nigritarsis was higher is water-stressed plants, but overall shoot mortality and infestation were low. These results shed light on some important aspects on the biology and ecology of C. nigritarsis and help in evaluating its potential as a biological control agent.

Biology, Ecology, and Management of Eastern Grape Leafhopper (Hemiptera: Cicadellidae), a Key Pest of Vineyards in North America

AbstractEastern grape leafhopper, Erythroneura comes (Say), is a key pest of grapes (Vitales: Vitaceae) in the central and northeastern United States and eastern Canada. This native insect uses its piercing-sucking mouthparts to puncture the mesophyll cells of leaves and suck out the contents, thereby reducing the quality and quantity of fruit. Eastern grape leafhopper has been reported as a vineyard pest for nearly 200 yr and is one of several Erythroneura spp. that feed on grapes in North America. Overwintered adults become active in early spring and may feed on grasses, weeds, and other plants before feeding on grapevines. Although eastern grape leafhopper has an extensive host range, it is only known to oviposit on wild and cultivated grapes. This multivoltine species can outbreak periodically, which has generated much research into improved monitoring and integrated pest management strategies employed throughout its native range. In this review, we describe the biology, life history, population dynamics, and phenology of eastern grape leafhopper and provide a historical account of monitoring and management strategies for this important vineyard pest.

Butterfly phenology in Mediterranean mountains using space-for-time substitution.

Inferring species' responses to climate change in the absence of long‐term time series data is a challenge, but can be achieved by substituting space for time. For example, thermal elevational gradients represent suitable proxies to study phenological responses to warming. We used butterfly data from two Mediterranean mountain areas to test whether mean dates of appearance of communities and individual species show a delay with increasing altitude, and an accompanying shortening in the duration of flight periods. We found a 14‐day delay in the mean date of appearance per kilometer increase in altitude for butterfly communities overall, and an average 23‐day shift for 26 selected species, alongside average summer temperature lapse rates of 3°C per km. At higher elevations, there was a shortening of the flight period for the community of 3 days/km, with an 8.8‐day average decline per km for individual species. Rates of phenological delay differed significantly between the two mountain ranges, although this did not seem to result from the respective temperature lapse rates. These results suggest that climate warming could lead to advanced and lengthened flight periods for Mediterranean mountain butterfly communities. However, although multivoltine species showed the expected response of delayed and shortened flight periods at higher elevations, univoltine species showed more pronounced delays in terms of species appearance. Hence, while projections of overall community responses to climate change may benefit from space‐for‐time substitutions, understanding species‐specific responses to local features of habitat and climate may be needed to accurately predict the effects of climate change on phenology.

Fifty Shades of the Harlequin Ladybird and a Sexually Transmitted Fungus.

The ectoparasitic fungus Hesperomyces virescens was studied on its invasive host, the harlequin ladybird Harmonia axyridis, in the Czech Republic. A primary aim was to examine the relationship between fungal infection and elytral coloration of the ladybird. Furthermore, the role of host sex and mating status of females were analyzed. Beetles (n = 1,102) were sampled during autumn migration, and then sexed, weighed, and screened for infection. Females were dissected for detection of sperm in their spermathecae. Ladybirds were sorted according to color form and absorbance spectrophotometry was used to quantify carotenoid contents in their elytra. In individuals of the nonmelanic succinea form, the degree of melanization was measured using digital photographs and putative age groups were estimated based on background color of elytra. Sexual differences in infection patterns indicated transmission during copulation: males were infected mostly on elytra and venter, and females had infection almost exclusively on elytra. Mated females had higher infection rate than virgins. There was no influence of genetic color form on the fungal infection. Putative age groups (visual sorting to yellow, orange, and red) correlated with fungal infection. Infected individuals had elevated elytral carotenoid levels in comparison to uninfected individuals, which could be explained by host age. Infection-free succinea beetles were extensively melanized because they emerged later in the season at lower temperatures which induced melanization. Overall, we highlight that H. axyridis is a multivoltine species whose age, if not taken into account in ecophysiological studies, might present a considerable confounding factor.

Climate-induced phenology shifts linked to range expansions in species with multiple reproductive cycles per year

Advances in phenology (the annual timing of species’ life-cycles) in response to climate change are generally viewed as bioindicators of climate change, but have not been considered as predictors of range expansions. Here, we show that phenology advances combine with the number of reproductive cycles per year (voltinism) to shape abundance and distribution trends in 130 species of British Lepidoptera, in response to ~0.5 °C spring-temperature warming between 1995 and 2014. Early adult emergence in warm years resulted in increased within- and between-year population growth for species with multiple reproductive cycles per year (n = 39 multivoltine species). By contrast, early emergence had neutral or negative consequences for species with a single annual reproductive cycle (n = 91 univoltine species), depending on habitat specialisation. We conclude that phenology advances facilitate polewards range expansions in species exhibiting plasticity for both phenology and voltinism, but may inhibit expansion by less flexible species.

Delineating the Asphondylia prosopidis Complex (Diptera: Cecidomyiidae): Possible Biological Control Agents of Honey Mesquite.

The Asphondylia prosopidis Cockrell complex with its fungal associate produces four distinct bud galls on honey mesquite (Prosopis glandulosa). They are considered as potential biological control agents to reduce seed production of invasive mesquites. Previous studies suggest that the complex may consist of more than one gall midge species or biotype. Therefore, before conducting host specificity tests, it is essential to understand the relationships among the gall midges in the complex. Each gall type was collected from sympatric regions in Arizona, New Mexico, and Texas for four years. Here we show that midges producing each gall type were clearly separated based on phylogenetic analysis using DNA sequences in the cytochrome oxidase subunit I region. Furthermore, we confirmed that morphological differences between pupae from each gall type were discernible, although variable, using a scanning electron microscope. Based on these differences, we suggest that the A. prosopidis complex consists of four different gall midge species, three of which are cryptic species. Among them, Asphondylia species producing a barrel gall type and A. prosopidis producing the original gall type are potential biological control agents of P. glandulosa because they are multivoltine species with four to five generations per year that complete their annual life cycle exclusively on flower buds of mesquite.

A population model for diapausing multivoltine insects under asymmetric cannibalism

AbstractPupa‐eating cannibalism occurs naturally in several insect species. Byasa alcinous is a multivoltine species of Red‐bodied Swallowtail butterfly found in East Asia, which diapauses as pupa over the winter and whose larvae cannibalize eggs and pupae. We investigate the effects on population dynamics of increasing the asymmetric cannibalistic attack rate of a general insect species in different environmental conditions. We do this by theoretically formulating a generalized system of univoltine and bivoltine larvae over two generations in the spring and summer months. We predict that a lack of resources over the summer can force the population to become entirely univoltine, unless the second‐generation bivoltine larvae increase their cannibalistic attack rate, and consume the diapausing pupae from the first generation. The model shows that under extreme environmental conditions, the persistence of univoltine larvae is favoured when faced with the threat of extinction. The model also predicts the conditions for the coexistence of both univoltine and bivoltine larvae, and the degree to which they can both coexist, which decreases as the resource in the second generation increases. This work provides the grounding for future theoretical and experimental consideration of the role of cannibalism in determining insect voltinism.

Does the Tachet trait database report voltinism variability of aquatic insects between Mediterranean and Scandinavian regions?

Labile traits are those that are not constrained by phylogeny and should respond directly to the environment through local adaptation or phenotypic plasticity. For example, voltinism (number of generations per year) is a labile trait that has been consistently related to latitude and, in particular, to temperature and photoperiod changes. Current trait databases include several labile traits that, at best, are coarsely coded to include potential intraspecific trait variability obtained from different literature sources. Given that these databases are used across large regions with contrasting environmental conditions or in small regions with particular environmental conditions, the reliability of these studies could be compromised at least for labile traits because of interpopulation variability. Based on a review of the literature on the life cycles of 317 aquatic insect species, we compared their types of voltinism in two regions with contrasting environmental conditions (the Mediterranean Basin and Scandinavia) with the information published by Tachet et al. (Invertebres d’eau douce: systematique, biologie, ecologie, 3rd edn. CNRS Editions, Paris, 2010) (i.e., potential number of generations per year). We found the expected higher prevalence of multivoltine life cycles in the Mediterranean Basin, whereas univoltine and semivoltine life cycles showed trends of prominence in Scandinavia. In addition, the life-cycle profiles of the genera included in the Tachet et al. database (hereafter TAC) were situated between those found in the Mediterranean Basin and Scandinavia, suggesting that this database properly represents voltinism variability across Europe. However, the use of this database exclusively for the northern or southern regions may be challenging because TAC is not able to accurately represent the life cycles of the species in these regions, especially for univoltine and multivoltine species. Future studies in stream ecology should thus put efforts into quantifying and understanding the role of intra-taxon trait variability in community assembly, at least for labile traits, to better understand trait-environment relationships.

Short-distance dispersal of Hypothenemus hampei (Ferrari) females (Coleoptera: Curculionidae: Scolytidae) during the coffee tree fruiting period.

The coffee berry borer (CBB), Hypothenemus hampei (Ferrari), is a multivoltine species closely associated with coffee crops worldwide, causing severe damage to the bean. In Mexico, as in all tropical regions, CBB survives during the inter-harvest period in residual berries on the ground or in dry berries remaining on the branches, and then disperses in search of the first suitable berries. In this study, we investigated how CBB dispersed from the first infested nodes during the fruiting period of Coffea canephora Pierre, which provides a favourable trophic level for this insect. Forty-five branches equally distributed in 15 coffee trees, with one infested node and four uninfested nodes, were selected. The branches were subjected to three treatments over nine weeks: 1) glue between nodes with full protection, 2) glue between nodes without protection, and 3) no glue and no protection. In addition, 45 CBB-free branches were selected and subjected to the same three treatments. CBB colonization can occur in three ways: 1) from an infested node to an uninfested node on the same branch, 2) from infested berries to uninfested berries within the nodes, 3) from branches to other branches. We also found that CBB dispersal between nodes of the same branches never occurred by walking but by flying. Thus, in this context of coffee berry development and ripening, and unlike the phenological situation of the inter-harvest period, CBB continuously travels very short distances, thus limiting its control.

Day-night temperature differential, rather than mean temperature, determines age of sexual maturation in Straicosta albicosta (Noctuidae)

While pheromone traps have been effectively used to monitor the recent range expansion of the western bean cutworm (WBC), very little is known about the pheromone mediated reproductive biology of this species. The age at which females initiated calling (the behaviour associated with the release of the sex pheromone), and the pattern of calling on the first three nights following sexual maturation were determined for virgin females held under four temperature regimes (25:20; 25:15; 20:15; 20:10 °C L:D and 16L:8D photoperiod), and two RH (60 and 80%). Regardless of the rearing conditions the pre-calling period (PCP) was always several days post emergence, supporting the hypothesis that WCB is a migrant species. However, surprisingly the length of the PCP was not directly related to mean temperature but rather to the temperature differential between the photophase and the scotophase. The duration of calling increased with female age, but unlike in other moths was not affected by the abiotic factors tested. The relative insensitivity to temperature and humidity, when compared with many other moth species, may be related to the WBC being a univoltine species with a mid-summer flight period. Consequently, there would not be strong selection pressure for plasticity in calling behavior when compared with the case of multivoltine species that experience a wide range of environmental conditions during different seasonal flight periods.