Univoltine Species Research Articles

Mating disruption of pea moth (Cydia nigricana) in organic peas (Pisum sativum)

We appraised mating disruption (MD) to control pea moth, Cydia nigricana (Fabricius) (Lepidoptera: Tortricidae), by assessing male attraction to monitor traps, larval pod infestation, and larval age structure in pheromone-treated and untreated grain pea fields [Pisum sativum L. (Fabaceae)], over a 5-year period. Cellulose pheromone dispensers were manually attached to the top shoots of pea plants and released 540 mg ha−1 day−1 synthetic pheromone E8,E10-dodecadien-1-yl acetate in a first test series (2000–2001) and ca. 4 200 mg pheromone ha−1 day−1 in a second series (2004–2006). The dispensers had a half-life of about 30 days. Although male attraction to pheromone monitoring traps was largely suppressed at the edges and within MD fields in both test series, MD treatments did not reduce pod infestation in the open field in 2000 and 2001. In the 2004–2006 series, larval damage reduction was achieved in the majority of the trials but overall MD efficacy in the open field was only 61% and not significant. In contrast, in field cages placed within the experimental sites and supplied with unmated pea moths, MD control was consistently high and significant. There were no obvious differences in the larval age distribution in all MD and control treatments, suggesting that infestations started and developed further similarly. As a univoltine species, C. nigricana larvae stay in the soil of pea fields for hibernation and pupate. The following year, emerging adults disperse and fly to the closest pea crop. Combined emergence site and pea crop treatments were conducted over 2 years to include this early migration phase of C. nigricana adults. However, the emergence site treatments did not enhance MD-control efficacy. We conclude that mating activity was only prevented in cage tests, whereas substantial mating occurred during the transit phase outside the pheromone-treated fields either within non-crop vegetation and/or at the edges of pheromone-treated pea fields orientated upwind. Thus, resulting gravid female entry can be regarded as the major constraint to reliable MD control.

Seasonal dynamics of the flower head infestation of Smallanthus maculatus by two nonfrugivorous tephritids.

Seasonal dynamics of the capitula infested by Dictyotrypeta sp. and Rhynencina spilogaster (Steyskal) (Diptera: Tephritidae) was evaluated throughout the flowering cycle of their host plant the sunflower, Smallanthus maculatus (Cavanilles) Robinson (Asterales: Asteraceae). In central Veracruz, Mexico, along 16 consecutive weeks, a total of 1,017 mature capitula were collected, recording the presence and abundance of immature stages (larvae and pupae) and their related parasitoids. Both fly species were present throughout the entire season, with overall infestation of 51.5% of the capitula examined. However, Dictyotrypeta sp. infested 11.3%, representing about one-fifth of them, and R. spilogaster was most abundant infesting four times as many capitula (42.9%), whereas both species were found together in only 2.6% of the capitula examined. Based on the temporal occurrence of larvae and pupae into flower heads as well as their associated parasitoids and times of emergence, Dictyotrypeta sp. had two yearly generations, and it seems that the second generation could enter a seasonal diapause; in contrast, R. spilogaster was a univoltine species that entered diapause that lasted until the next year.

Supercooling capacity and cold hardiness of band-winged grasshopper eggs (Orthoptera: Acrididae).

The band-winged grasshopper, Oedaleus asiaticus Bei-Bienko, is one of the most dominant and economically important grasshopper species in the steppe grasslands and farming-pastoral ecotone in northern China. It is a univoltine species and overwinters as eggs in soil. The cold hardiness of its eggs was examined in the laboratory. Water content in soil significantly affected the supercooling points (SCPs), water content and fat content of prediapause eggs. With the increase of water content in soil, the SCP, and water content of prediapause eggs rose whereas the fat content declined. There was a significant relationship between the SCP and water content or fat content of prediapause eggs. The SCPs of prediapause and diapause eggs varied from −7.6 to −28.4°C and the SCPs of eggs 30 d after oviposition could be divided into two groups. The means of high SCP group (−11.0 to −11.9°C) were much higher than those of low SCP group (−21.8 to −21.9°C), and the majority belonged to the latter (90.48–93.33%). The SCPs of prediapause eggs and early-diapause eggs 30 d after oviposition were significantly higher than those of deep-diapause eggs 60 d after oviposition. The survival rates of diapause eggs were significantly different among different temperature treatments. The survival rate was higher than 88% at greater than −20°C and declined significantly to 57% at −25°C, and suddenly dropped to zero at −30°C. The lower lethal temperature (Ltemp50) for 12 h exposure was −25.3°C and the lower lethal time (Ltime50) at −20°C was 32.8 d. As the mean SCPs of diapause eggs were similar to their Ltemp50, the SCP of eggs can be considered as a good indicator of cold hardiness for O. asiaticus and that this grasshopper is a freeze-intolerant insect.

Description of Rhagoletis cerasi (Diptera: Tephritidae) pupal developmental stages: indications of prolonged diapause.

The European cherry fruit fly, Rhagoletis cerasi (L.) (Diptera: Tephritidae), is the key pest of sweet and sour cherries in many European countries and west Asia. It is a univoltine species of the west Palaearctic zone that undergoes obligatory pupal diapause. In this study, the development of R. cerasi pupae that were brought to an optimum temperature for postdiapause development following a long chilling period is described. The six most representative developmental stages within the puparium are illustrated, and the developmental progression among the stages after the end of the chilling period is quantified. Within 20 d postchilling, there was a gradual progress from stage I to pharate adult. However, ∼30% of the pupae remained at the transitional stage II, after 20 d at 25°C (optimum temperature for development). This suggests that a proportion of pupae remain at an intermediate developmental stage for an extended period of time that goes beyond 20 d postchilling. The pupal stage II might be related to diapause termination and responsiveness to environmental cues. It may also define the time before developmental progress to pharate adult. This finding agrees with previous studies proposing that a number of R. cerasi pupae undergo prolonged diapause, though the morphological characteristics of these pupae have never been described before.

Life history of Kermes quercus (LINNAEUS) (Hemiptera: Kermesidae) in Poland

ABSTRACT This research complements the results of a study of the life cycle of Kermes quercus (L.) performed in Poland in 2008-2009. The latest observations were carried out in 2010 from the beginning of March until the end of November. They showed that K. quercus overwintered as 2nd-instar nymphs. These developed into adults at the beginning of May. Reproduction began at the beginning of June. The 1st-instar nymphs of the new generation appeared in mid-June. They then developed for about 5 months, after which they entered the winter diapause. All the observations, carried out in 2008-2010, showed that, under the climatic conditions of Poland, K. quercus is not a univoltine species. One generation develops over two years. In the first year it overwinters as 1st-instar nymphs and in the second year as 2nd-instar nymphs.

The Auchenorrhyncha fauna of peat bogs in the Austrian part of the Bohemian Forest (Insecta, Hemiptera)

The first overview on the Auchenorrhyncha fauna of peat bogs of the Austrian Bohemian Forest is presented. Seven oligotrophic peat bog sites were studied in 2011 by suction sampler (“G-Vac”) and 93 Auchenorrhyncha species (with 7465 adult specimens) were recorded. Eleven species (about 18 % of the individuals) are tyrphobiontic or tyrphophilous. The relative species abundance plot is not very steep; the six most abundant species represent 50 % of the individuals. The most common species is Conomelus anceps (17 % of the individuals). Compared to the whole Austrian Auchenorrhyncha fauna, the fauna of peat bogs comprises distinctly more univoltine species and more species hibernating in nymphal stage. Densities of adult Auchenorrhyncha in peat bogs are low in spring (about 10–60 individuals per m²) and high in July, with up to 180 (±50) individuals per m². Disturbed peat bogs have higher species numbers and higher Auchenorrhyncha densities in total, but lower numbers and densities in peat bog specialists.

The study of ontogenetic trajectory reveals the timing of reproductive events in Ancylus fluviatilis (Gastropoda: Planorbidae)

We analysed ontogenetic shape change in the planorbid limpet Ancylus fluviatilis (Müller, 1774) in two rivers in Southern Italy. We developed a new method to discriminate among different cohorts in Ancylus, based on principal component analysis. The method is useful when shape change during growth is allometric, as in our study model. We discovered that bivoltinism occurs in Ancylus in Southern Italy, contrary to previous accounts, which invariably describe A. fluviatilis as a semelparous and univoltine species, although acknowledging difficulty in discriminating among cohorts. The methods presented here may potentially help research in reproductive traits in many other mollusc populations where shape change during ontogeny is demonstrated to be allometric.

Prolonged pupal dormancy is associated with significant fitness cost for adults of Rhagoletis cerasi (Diptera: Tephritidae)

In temperate areas, dormancy (diapause and/or quiescence) enables herbivorous insect species to persist and thrive by synchronizing growth and reproduction with the seasonal phenology of their host plants. Within-population variability in dormancy increases survival chances under unpredictable environmental changes. However, prolonged dormancy may be costly, incurring trade-offs in important adult fitness traits such as life span and reproduction. We used the European cherry fruit fly, Rhagoletis cerasi, a stenophagous, univoltine species that overwinters in the pupal stage for usually one or more years to test the hypotheses that prolonged dormancy of pupae has trade-offs with body size, survival and reproduction of the resulting adults. We used two geographically isolated populations of R. cerasi to compare the demographic traits of adults obtained from pupae subjected to one or two cycles of warm–cold periods (annual and prolonged dormancy respectively). Regardless of population, adults from pupae that experienced prolonged dormancy were larger than counterparts emerging within 1year. Prolonged dormancy did not affect adult longevity but both lifetime fecundity and oviposition were significantly decreased. Extension of the life cycle of some individuals in R. cerasi populations in association with prolonged dormancy is likely a bet-hedging strategy.

The role of the North Atlantic Oscillation in controlling U.K. butterfly population size and phenology

1. The North Atlantic Oscillation (NAO) exerts considerable control on U.K. weather. This study investigates the impact of the NAO on butterfly abundance and phenology using 34 years of data from the U.K. Butterfly Monitoring Scheme (UKBMS).2. The study uses a multi-species indicator to show that the NAO does not affect overall U.K. butterfly population size. However, the abundance of bivoltine butterfly species, which have longer flight seasons, were found to be more likely to respond positively to the NAO compared with univoltine species, which show little or a negative response.3. A positive winter NAO index is associated with warmer weather and earlier flight dates for Anthocharis cardamines (Lepidoptera: Pieridae), Melanargia galathea (Lepidoptera: Nymphalidae), Aphantopus hyperantus (Lepidoptera: Nymphalidae), Pyronia tithonus (Lepidoptera: Nymphalidae), Lasiommata megera (Lepidoptera: Nymphalidae) and Polyommatus icarus (Lepidoptera: Lycaenidae). In bivoltine species, the NAO affects the phenology of the first generation, the timing of which indirectly controls the timing of the second generation.4. The NAO influences the timing of U.K. butterfly flight seasons more strongly than it influences population size.

Laboratory Rearing ofLaricobius nigrinus(Coleoptera: Derodontidae): A Predator of the Hemlock Woolly Adelgid (Hemiptera: Adelgidae)

Coleopteran species are biological control agents of numerous invasive pests.Laricobius nigrinus(Coleoptera: Derodontidae), a predaceous, univoltine species, spends the summer aestivating but is active for the rest of the year.Laricobius nigrinuspossesses many essential attributes for effective biological control of the hemlock woolly adelgid (Hemiptera: Adelgidae). The predator must be reared in large numbers for field releases. We describe some of the studies that led to the successful procedures currently used for mass rearingL. nigrinus.

Response to “traits and stress: keys to identify community effects of low levels of toxicants in test systems” by Liess and Beketov (2011)

Response to “traits and stress: keys to identify community effects of low levels of toxicants in test systems” by Liess and Beketov (2011)

The long summer: Pre-wintering temperatures affect metabolic expenditure and winter survival in a solitary bee

The impact of climate change on insect populations depends on specific life cycle traits and physiological adaptations. The solitary bee Osmia lignaria winters as a pre-emergent adult, and requires a period of cold temperature for winter diapause completion. It is a univoltine species, and diapause induction does not depend on photoperiod. To understand the potential effects of longer summers on O. lignaria populations, we exposed individuals to three treatments simulating early, mid and late winter arrivals, and measured respiration rates, metabolic expenditure, weight loss, fat body depletion, lipid levels and winter mortality. The early-winter treatment disrupted diapause development, but had no apparent negative effects on fitness. In contrast, late-winter bees had a greater energetic expenditure (1.5-fold), weight (1.4-fold) and lipid (2-fold) loss, greater fat body depletion, and a 19% increase in mortality compared to mid-winter bees. We also monitored adult eclosion and arrival of winter temperatures under natural conditions in four years. We found a positive correlation between mean degree-day accumulation during pre-wintering (a measure of asynchrony between adult eclosion and winter arrival) and yearly winter mortality. Individually, bees experiencing greater degree-day accumulations exhibited reduced post-winter longevity. Timing of adult eclosion in O. lignaria is dependent on the duration of the prepupal period, which occurs in mid-summer, is also diapause-mediated, and is longer in populations from southerly latitudes. In a global warming scenario, we expect long summer diapause phenotypes to replace short summer diapause phenotypes, effectively maintaining short pre-wintering periods in spite of delayed winter arrivals.

Habitat isolation shapes the recovery of aquatic insect communities from a pesticide pulse

Summary1. The role of spatial processes in ecotoxicology is largely ignored. Yet, together with species‐specific sensitivities to the pollutant, spatial processes may determine community recovery and the resulting community composition after a pollution event.2. We investigated the isolation‐specific potential for internal recovery by reproduction and external recovery by dispersal after a pesticide pulse in experimental aquatic insect communities along an isolation gradient.3. External recovery was important in the univoltine species and in a multivoltine species that went locally extinct but only when a source population was nearby. Internal recovery occurred in all multivoltine species and was unexpectedly stronger in more isolated communities, probably because of release from a dispersal‐limited key predator.4. As a result, community recovery and resulting changes in composition strongly depended on isolation and species differences in the potential for external recovery through dispersal and internal recovery through reproduction.5. Synthesis and applications. Our results indicate that while the immediate impact of a toxicant on natural communities is shaped by species sensitivities, their recovery is primarily dependent on the degree of isolation. Risk assessment and the protection of communities under toxicant threat may improve greatly from considering the spatial context: isolated communities and communities with poor dispersers should receive extra protection to safeguard their member species. Ideally, land use planning should strive to remediate isolation of natural communities under threat in agricultural landscapes. Where this is not possible, spatial regulation of pesticide application may considerably improve protection of extant diversity.

Traits and stress: keys to identify community effects of low levels of toxicants in test systems

Community effects of low toxicant concentrations are obscured by a multitude of confounding factors. To resolve this issue for community test systems, we propose a trait-based approach to detect toxic effects. An experiment with outdoor stream mesocosms was established 2-years before contamination to allow the development of biotic interactions within the community. Following pulse contamination with the insecticide thiacloprid, communities were monitored for additional 2 years to observe long-term effects. Applying a priori ecotoxicological knowledge species were aggregated into trait-based groups that reflected stressor-specific vulnerability of populations to toxicant exposure. This reduces inter-replicate variation that is not related to toxicant effects and enables to better link exposure and effect. Species with low intrinsic sensitivity showed only transient effects at the highest thiacloprid concentration of 100 μg/l. Sensitive multivoltine species showed transient effects at 3.3 μg/l. Sensitive univoltine species were affected at 0.1 μg/l and did not recover during the year after contamination. Based on these results the new indicator SPEAR mesocosm was calculated as the relative abundance of sensitive univoltine taxa. Long-term community effects of thiacloprid were detected at concentrations 1,000 times below those detected by the PRC (Principal Response Curve) approach. We also found that those species, characterised by the most vulnerable trait combination, that were stressed were affected more strongly by thiacloprid than non-stressed species. We conclude that the grouping of species according to toxicant-related traits enables identification and prediction of community response to low levels of toxicants and that additionally the environmental context determines species sensitivity to toxicants.

VERY HIGH POPULATION ESTIMATES AND LIMITED MOVEMENT OF SNAIL-KILLING FLIES (DIPTERA: SCIOMYZIDAE) ON AN IRISH TURLOUGH (TEMPORARY LAKE)

Sciomyzid flies (Diptera) have potential as biological control agents of intermediate hosts of snail-borne trematode diseases and as bioindicators of habitat condition and quality (particularly hydrology and vegetation structure). Standard area sweep net sampling of these flies in a single vegetation zone across ten turloughs in summer 2004 highlighted the importance of vegetation structure (standing height and outstretched length) on the abundance and species richness of Sciomyzidae. A mark-recapture study was initiated in the summer of 2005 with the aim of quantifying absolute populations at one site where sciomyzid abundance was particularly high (Cregaclare South, Co. Galway). The total abundance of Sciomyzidae at the site was estimated at 3512 flies over an area of 600 square metres. This density (6.08 flies per square metre) is consider ably higher than densities previously reported in two studies of a sciomyzid species in the USA, but is in line with estimates from the 2004 wider study. Specific markings were used in the 2005 mark-recapture study to monitor any adult fly movements within the habitat. Females in two out of the three univoltine species showed a positive correlation in the proportion of gravid individ uals caught over time. Multivoltine species showed no such relationship. Additionally, multivariate procedures were used to investigate the effect of date of sampling and spatial position on sciomyzid assemblage composition.

Use of Food and Space by Tunneler Dung Beetles (Coleoptera; Scarabaeinae) During Reproduction

At two temperate pasturelands in northern Mexico, we explored possible competition for food and space under pats during the simultaneous nesting periods of the univoltine species Dichotomius colonicus (Say), Phanaeus quadridens (Say), and Copris sierrensis Matthews. To simulate unlimited resources, 50 5-kg cow dung pats were placed at regular distance intervals in each pastureland. After building trenches around the pats, the number and depth of each nest, as well as larval development status, were documented once for a period of 1-8 mo. Analyses of variance and association tests were used to make a between-site comparison of dung pat occupation, nests occupied per species, nests per dung pat, and nest depth below each pat. The proportion of pats occupied by each species differed significantly between sites. C. sierrensis colonizing most pats at one site and D. colonicus at the other. There were no differences between sites in the frequency of pats occupied by more than one species. The association test and Ochiai index showed that each species colonized dung pats independently. The results suggest that pat occupation depended on their location by beetles and the relative abundance of each species. The species tended to dig nests at different depths, possibly reducing interspecific competition for space. It can therefore be concluded that, when food resources seem to be unlimited, they are shared following a "lottery dynamic" model if there is spatial differentiation among species.

Crustacean and rotifer seasonality in a Mediterranean temporary pond with high biodiversity (Lavajo de Abajo de Sinarcas, Eastern Spain)

A follow-up study was made of planktonic and periphytic crustaceans and rotifers during two hydroperiods of consecutive years in a Mediterranean temporary pond. The pond is relatively large with quite long hydroperiods in wet years (6-8 months) and it has a very rich community (4 large branchiopods, 12 cladocerans, 9 copepods, 36 rotifers). Three phases in faunal composition, quite consistent fram year to year, were distinguished: (1) Filling phase in autumn-winter is dominated by anos­tracans (endemic Branchipus cortesi, with low proportions of Branchipus schaefferi) and diaptomids, two univoltine species (Hemidiaptomus ingens inermis, Diaptomus cyaneus intermedius) and one muItivoltine (Mixodiaptomus laciniatus atlantis). (2) Middle phase in spring dominated by cladocerans (Ceriodaphnia n.sp., Simocephalus vetulus, Ephemeroporus pinthoni­cus, Chydorus sphaericus, Alona azorica) in this phase is also abundant the conchostracan Maghrebestheria maroccana and the notostracan Triops cancriformis. A shift toward insects occurs in the later part of this phase. (3) Desiccation phase in sum­mer with lower diversity (Moina micrura, Alona rectangula and cyclopoids). Rotifers showed a low contribution to biomass and were more important in the middle phase. These phases are also marked by an increase of nutrients and phytoplankton chlorophyll in the filling and desiccation phases and a decrease of these variables in the middle phase, resulting in phytoplank­ton cIearance and greater water transparency, concurrent with macrophyte growth. Interannual variability was outstanding in shaping these phases. The year 2007 was preceded by a wetter autumn, whereas 2008 was preceded by a very dry autumn thus, in this second year the main hydroperiod was shorter and the first phase was merged with the middle phase. In this shorter hydroperiod the open water microinvertebrate community reached lower biomass but attained a similar diversity since rotifers became relatively more abundant and richer in species than in the 2007 main hydroperiod, when the community was fully dominated by crustaceans.

Seasonal dynamics in corixids (Heteroptera: Corixidae): A study from managed fishponds in South Bohemia

The 27 managed fishponds were investigated in South Bohemia from October 2006 to October 2008. Eleven species of the family Corixidae were collected. Sigara lateralis, S. falleni and Paracorixa concinna were the most abundant and the most frequent species. Samples were more abundant at localities of smaller area. The life cycles of both bivoltine and univoltine species were studied, and together with data on the development in female genitalia showed a certain shift in the start of vitellogenesis during the investigated period.

Circannual pupation rhythm in the varied carpet beetle Anthrenus verbasci under different nutrient conditions

Abstract Anthrenus verbasci pupates in spring and the timing of pupation is controlled by a circannual rhythm. Although A. verbasci is considered to be a univoltine species in Japan, it is assumed that larval development in its natural habitats, including bird nests, varies with nutrient availability, and that the life cycle often takes two or more years to complete. In the present study, larval development and pupation times were compared under constant and outdoor conditions in larvae provided a diet of either high‐nutrient bonito powder or low‐nutrient pigeon feathers. Although a circannual pupation rhythm was observed irrespective of the diet used, larval development was slower on feathers than on bonito powder. The pupation times on feathers varied over three years or more under both constant and outdoor conditions. Under outdoor conditions, larvae grown on feathers needed three years to approach the weight gained within a year by larvae grown on bonito powder. It is considered that life cycle length in A. verbasci is often two years or more in nutritionally unstable natural habitats, and that this species has probably evolved a circannual rhythm as a seasonal adaptation to nutrient‐poor environments.

Biology and host specificity ofAulacobaris fallax(Coleoptera: Curculionidae), a potential biological control agent for dyer’s woad,Isatis tinctoria(Brassicaceae) in North America

Dyer’s woad, Isatis tinctoria, a plant of Eurasian origin is a problematic weed in western North America against which a classical biological weed control programme was initiated in 2004. Three European insect species were selected as candidate agents to control this invasive species, including the root-mining weevil Aulacobaris fallax. To determine its suitability as an agent, the biology and host specificity of A. fallax were studied in outdoor plots and in the field between 2004 and 2006 in its native European range. Aulacobaris fallax is a univoltine species that lays its eggs from March to August into leaf stalks and roots of dyer’s woad. Larvae mine and pupate in the roots and adults emerge from August to October. Up to 62% of the dyer’s woad plants at the field sites investigated were attacked by this weevil. In no-choice host-specificity tests, A. fallax attacked 16 out of 39 species and varieties within the Family Brassicaceae. Twelve of these are native to North America. In subsequent multiple-choice tests, seven species, all native to North America, suffered a similar level of attack as dyer’s woad, while none of the European species were attacked. Our results demonstrate the importance of including test plant species that have not co-evolved with the respective candidate agent. In sum, we conclude that the risk of non-target effects is too high for A. fallax to be considered as a biological control agent for dyer’s woad in the United States.