Pupal Survival Research Articles

Trypsin inhibitor from Moringa oleifera flowers interferes with survival and development of Aedes aegypti larvae and kills bacteria inhabitant of larvae midgut

Moringa oleifera flower extract, with trypsin inhibitor activity, is a larvicidal agent on Aedes aegypti. This work reports the isolation of trypsin inhibitor (M. oleifera flower trypsin inhibitor (MoFTI)) and its effect on A. aegypti egg hatching, viability of newly hatched larvae, survival of pupae, and growth of inhabitant bacteria from midgut of fourth-instar larvae (L4). MoFTI (K i, 2.4 μM), isolated by affinity chromatography on trypsin-agarose column, was an 18.2 kDa polypeptide on sodium dodecyl sulphate-polyacrylamide gel electrophoresis. Flower extract (at concentrations of 8.5-17.0 mg/mL) reduced egg hatchability while MoFTI (0.05-0.5 mg/mL) did not affect the hatching rate. Mortality of newly hatched larvae ranged from 3.5 to 19.1 % in the presence of the extract (4.0-17.0 mg/mL) and was also promoted by MoFTI (LC50, 0.3 mg/mL). After 72 h, larvae incubated with extract at 13.0 and 17.0 mg/mL were at stages L2 and L1, respectively, while in control they reached L3 instar. In the presence of MoFTI, at all concentrations tested, the larvae did not pass the first instar. Flower extract and MoFTI did not interfere on pupae survival. The extract and MoFTI inhibited the growth of L4 gut bacteria (minimum inhibitory concentrations of 3.47 and 0.031 mg/mL, respectively) but only the inhibitor showed bactericide effect (minimum bactericidal concentration of 1.0 mg/mL). The findings reported herein indicate that MoFTI constitutes a larvicidal principle from M. oleifera flowers against A. aegypti newly hatched larvae and is an antibacterial agent active against the microbiota from L4 gut.

New artificial diet for continuous rearing of the bean pod borer, Maruca vitrata.

The bean pod borer, Maruca vitrata Fabricius (Lepidoptera: Crambidae), is a serious pantropical pest of grain legumes. A suitable artificial diet is desirable for producing uniform insects for commercial purposes or research. Three previously described artificial diets, 1 newly-developed artificial diet, and cowpea (Vigna unguiculata (L.) Walp. (Fabales: Fabaceae)), the natural hostplant of M. vitrata, were used for rearing M. vitrata, and the life parameters were examined. The results indicated that insects completed a full life cycle only when the larvae were fed cowpea or the diet reported by Onyango and Ochieng'-Odero (1993), called the “D-OO diet.” However, the rearing efficiency (i.e., larval and pupal survival, longevity of adults, and fecundity) on the D-OO diet was inferior to the rearing efficiency on cowpea. Subsequently, a new artificial diet was formulated based on soybean powder, Glycine max (L.) Merr. (Fabales: Fabaceae), and wheat germ, Triticum aestivum L. (Poales: Poaceae). The egg production, egg hatching, larval developmental duration, and pupal survival of the M. vitrata reared on the new artificial diet were found to be significantly improved relative to the D-OO diet, but were not significantly better than on the host-plant cowpea. The optimum rearing density was 15–25 larvae per box. There were no significant changes in reproductive potential after 8 successive generations of rearing on the new diet. These results indicated that the newly developed diet could serve as a viable alternative to cowpea plant for continuous rearing of M. vitrata.

No fitness costs associated with resistance of Busseola fusca (Lepidoptera: Noctuidae) to genetically modified Bt maize

A concern regarding planting of Bt crops is that their widespread cultivation could lead to evolution of insect resistance to Bt toxins. In South Africa, the noctuid maize stem borer (Busseola fusca [Fuller]), is resistant to Bt maize (Zea mays L.; MON810) which produces Cry1Ab protein. The presence of fitness costs in resistant populations could be a valuable component of resistance management since the non-Bt maize refuge may select against resistance. The aim of the study was to determine if there are fitness costs associated with Bt resistance of B. fusca. Life history parameters were compared between individuals of a Bt maize resistant B. fusca population when feeding on Bt or non-Bt maize. Similar comparisons were done using a control population. Field collected larvae as well as their F1-generation were used in the study. The following parameters were compared: pupal mass, moth longevity, fecundity, fertility, larval mass and survival, and sex ratio. Except for LT50-values, no fitness costs were associated with the resistance trait in the highly resistant B. fusca population. The absence of fitness costs and presence of resistant populations may promote the use of a multi-gene strategy which would be expected to impact negatively on fitness.

Effects of Compaction and Wetting of Laterite Cover Soil on Development and Survival of <I>Musca domestica</I> (Diptera: Muscidae) Immatures

Effects of laterite cover soil with different characteristics on survival of buried eggs, third instar larvae, and pupae of Musca domestica (L.) were studied experimentally. Soil treatments were loose dry soil, loose wet soil, compacted dry soil, and compacted wet soil (CWS). Eggs, third instar larvae, and pupae were buried under 30 cm of the different soil treatments and placed under field conditions until adults emerged. Rearing medium was provided for eggs and larvae, and control treatments of all stages were unburied immatures placed on soil surface. Egg and pupal survival to adult were significantly affected by the cover soil treatments, but third instars were more resilient. Wet soil treatments (loose wet soil and CWS) resulted in significantly reduced pupal survival, but increased survival of eggs. However, CWS significantly reduced adult emergence from buried eggs. Though emergence of house flies buried as eggs was significantly reduced, some were able to hatch and emerging first instar larvae developed to pupation. Although cover soil does not completely prevent fly emergence, it did limit development and emergence of buried house flies.

Out of sight but not gone: Sero-surveillance for cattle grubs, Hypoderma spp., in western Canada between 2008 and 2010

Despite the lack of evidence of clinically infected cattle in western Canada since the late 1990s there is persistent evidence from serological sampling that warble fly infections remain endemic. As part of a general survey of cattle parasites conducted on calves entering a feedlot in southern Alberta sera were tested for the presence of anti-Hypoderma antibodies using an established ELISA. Calves for the study were drawn from auction markets in Manitoba, Saskatchewan, Alberta and British Columbia and serum samples were collected, according to a randomization scheme, as the calves entered a single feedlot in October through December (Survey) of three consecutive years (2008–2010). In addition, a sub-sample of calves originating on a ranch in southeastern Alberta (Ranch 1) that had been the subject of previous surveillance was tested. Sero-prevalence of anti-Hypoderma antibodies of the Survey calves ranged from 0.0% to 100.0% depending on origin and overall varied among the three years with the sero-prevalence being 45.6%, 26.9%, 28.5% in 2008, 2009 and 2010 respectively. Sero-prevalence in Ranch 1 calves varied among years, with one year being much higher and was different from overall Survey sero-prevalence in two of three years (31.7%, 64.1%, 38.5% in 2008, 2009, 2010 respectively). In the Survey population there was a trend to lower sero-prevalence over the three years while on Ranch 1 there was no clear trend. In the samples with ELISA adjusted absorbance values above the positive cut-off an examination of the cumulative relative frequency showed that in all years approximately 90% of the samples were in the lower 3 of 14 bins in both populations and in two of three years in Ranch 1 population. The clustering of the positive ELISA data at the lower end of the range is suggestive of low level grub infestations. The increased frequency of high positive ELISA results from Ranch 1 in 2009 potentially indicate an ‘outbreak year’ in which pupal and adult fly survival was higher than for other years of this study resulting in more infested animals with higher burdens. Examination of precipitation and temperature profiles from the subject ranch support this suggestion.

Bitrophic toxicity of Cry1Ac to Cycloneda sanguinea, a predator in Brazilian cotton

AbstractInsect predators are exposed to the Cry1Ac toxin in Bt cotton fields through several pathways. In this study, we investigated the effects of activated Cry1Ac added to a diet on Cycloneda sanguinea (L.) (Coleoptera: Coccinellidae), which is one of the main predators of non‐target pests in Brazilian cotton. Direct bitrophic exposure of C. sanguinea to Cry1Ac was done by feeding beetles with Aphis gossypii (Glover) (Hemiptera: Aphidae) sprayed with 500 μg per ml Cry1Ac solution. Larval and pupal survival, development time, aphid consumption, and adult longevity were recorded daily. Couples within the same experimental treatment were paired and numbers of eggs laid and hatched per female were recorded daily. Net replacement rate was calculated for each female. During development, a C. sanguinea larva consumed on average 1.8 μg of activated Cry1Ac. No significant differences due to Cry1Ac were observed for any of the response variables, except aphid consumption. Larvae receiving Cry1Ac consumed more aphids than larvae receiving distilled water alone. Additional statistical analyses were conducted to evaluate independence of responses, and for the independent responses, a simple meta‐analysis was conducted to test the null hypothesis that all responses were zero. Nearly all of the response variables were statistically independent. Two pairs of responses were not independent, but the associated multivariate tests were not significant. The meta‐analysis suggested that all effects were not different from random variation around zero and no cumulative effects could be detected. Our results indicated that bitrophic exposure to activated Cry1Ac is likely to have little or no adverse ecological effect on C. sanguinea.

Effect of soil moisture on overwintering pupae in Spodoptera exigua (Lepidoptera: Noctuidae)

Spodoptera exigua Hubner (Lepidoptera: Noctuidae), can overwinter as pupae at depths of 0- to 5-cm beneath the ground. In order to understand the effect of soil moisture on the overwintering success of this species, we tested the supercooling point and survival of pupae, and the growth rate of prepupae that were exposed to different temperature and soil moisture in the laboratory. Results showed that supercooling points, body water contents, and survivals after the different pre-treatments were not significantly affected by the soil moisture. The developmental progress of prepupae, survival of prepupae and pupae were negatively correlated with soil moisture as well as the delay of exposure time, which supports the hypothesis that soil moisture acts as a developmental modulator. We presumed that the delay of pupation and lower prepupae survival under higher soil moisture was due to lack of a complete pupal chamber for protection at low temperatures. Low pupal survival was likely attributed to lack of oxygen in the soil, especially under the condition of higher soil moisture. We suggest that using strategies of irrigation and soil tillage during winter may decrease the overwintering population of S. exigua from the perspective of integrated pest management.

Costly leaf shelters protect moth pupae from parasitoids

Many caterpillars construct shelters by folding leaves and feeding from within. Many shelter-constructing species suffer high rates of parasitism as larvae or pupae. In spite of the likely significance, the effects of these shelters on the survival of pupae and the trade-off between feeding and constructing shelters have attracted little experimental attention. In both field and laboratory experiments, fern-feeding caterpillars [Herpetogramma theseusalis (Walker) (Lepidoptera: Crambidae)] invested heavily in shelters, losing weight and significantly delaying pupation rather than feeding or pupating in exposed locations. Experimentally thinning the walls of shelters in the field doubled the parasitism rate. Parasitism of pupae exceeded predation by an order of magnitude or more in both seasons of this study. Caterpillars constructed similarly sized shelters regardless of availability of fern fronds, resulting in incomplete shelters on especially small fronds, putting pupae at increased risk of parasitism. We suggest that similar interactions are common and merit more attention.

Ciclos de vida comparados de Aedes aegypti (Diptera, Culicidae) do semiárido da Paraíba

O presente trabalho teve como objetivo comparar os ciclos de vida entre amostras de populações de Aedes aegypti (Linnaeus, 1762) coletadas em dez municípios localizados no semiárido paraibano. Os ciclos de vida foram estudados a uma temperatura de 26 ± 2ºC, umidade relativa de 60 ± 10% e fotofase de 12 horas. Diariamente foram avaliados os períodos de desenvolvimentos e as viabilidades das fases de ovo, larva e pupa, bem como a razão sexual, longevidade, tamanho e fecundidade dos adultos. Foi realizada uma análise de agrupamento, utilizando-se uma matriz de distância euclidiana através do método da média não-ponderada. As durações e viabilidades para as fases de ovo, larva e pupa apresentaram respectivamente, uma variação média de 3,7 a 4,7 dias e 82,8% a 97,7%, 9,1 a 10,8 dias e 91,2% a 99,2% e de 2,1 a 2,5 dias e 93,5% a 98,4%. O comprimento alar foi de 5,13 a 5,34 mm para as fêmeas e de 4,18 a 4,25 mm para os machos. A menor fecundidade (153,6 ovos/fêmea) ocorreu na população de A. aegypti oriunda de Pedra Lavrada, enquanto que a maior fecundidade (310,6 ovos/fêmea) foi constatada para A. aegypti de Campina Grande. A análise de agrupamento com base na similaridade dos dados biológicos revelou a formação de dois grandes grupos distintos, onde as populações de A. aegypti de Serra Branca e Cuité apresentam maior similaridade entre si. As diferenças de ciclos biológicos verificadas entre as populações de A. aegypti demonstra a capacidade dessa espécie de sofrer variações na sua biologia e se adaptar às diferentes condições ambientais, favorecendo a permanência deste inseto nessas áreas com aumento do risco de transmissão do vírus da dengue.

Implications of saline concentrations for the performance and competitive interactions of the mosquitoesAedes aegypti(Stegomyia aegypti) andAedes albopictus(Stegomyia albopictus)

Aedes albopictus (Stegomyia albopictus) (Diptera: Culicidae) has probably supplanted Aedes aegypti (Stegomyia aegypti) throughout most of its historical range in the U.S.A., although Ae. aegypti still exists in large coastal cities in southern Florida. We measured salt concentrations in field containers along an axis perpendicular to the coast and examined intraspecific outcomes in these species under different salt concentrations in a factorial study using varying intra- and interspecific densities in different conditions of salinity to order to determine if salt could mitigate the documented competitive superiority of Ae. albopictus. Salt in field containers declined away from the coast, with maximal values similar to our lower salt concentrations. Egg hatching and short-term survival of pupae and late instars were not affected by salt concentrations; survival of early instars of both species decreased at higher concentrations. In high salt conditions, Ae. aegypti achieved higher survival. In the longterm experiment, both species displayed longer development times. Salt did not affect interactions for either species; Ae. aegypti survived in the highest salt conditions, regardless of density. The tolerance of Ae. aegypti to high salt concentrations may allow it to use coastal containers, although because salt did not mediate interspecific interactions between Ae. aegypti and Ae. albopictus, the ultimate effects of salt on the coexistence of these species or exclusion of either species remain unknown.

Pupal diapause development and termination is driven by low temperature chilling in Bactrocera minax

Bactrocera minax is a major citrus pest in China, Bhutan, and India. It is univoltine and exhibits pupal diapause during winter. To better understand pupal diapause in this pest, we investigated pupal survival and pupal developmental duration under field and laboratory conditions. Specifically, we tested if pupal chilling was required for diapause development and termination. Nearly all mature larvae collected at the end of the citrus season entered pupal diapause. For pupae exposed in the field, natural chilling for less than 3 months resulted in more than 70 % mortality. However, exposure to winter conditions for 3 months or more both decreased pupal mortality and developmental duration when pupae were returned to the laboratory and held under constant temperature (25 C). When pupae were gathered from the field in November and exposed to different chilling regimes in the laboratory, the chilling duration (30 vs 60 days) had significantly more impact on pupal survival than the specific chilling tem- perature (6, 8, 10, or 12 C constant). However, both chilling duration and chilling temperature impacted on the pupal developmental duration, with longer chilling dura- tion and higher temperatures decreasing pupal develop- mental duration. In conclusion, we demonstrated that pupal diapause development and termination in B. minax is strongly influenced by chilling conditions. Increasing cold exposure led to significantly and consistently faster adult eclosion and improved synchronization of adult emer- gence. This knowledge will help with the laboratory rear- ing of B. minax, an essential step in the long-term management of this pest.

THE INFLUENCE OF DIETARY α‐SOLANINE ON THE WAXMOTH Galleria mellonella L

Plant allelochemicals are nonnutritional chemicals that interfere with the biology of herbivores. We posed the hypothesis that ingestion of a glycoalkaloid allelochemical, α-solanine, impairs biological parameters of greater wax moths Galleria mellonella. To test this idea, we reared wax moths on artificial diets with 0.015, 0.15, or 1.5 mg/100 g diet of α-solanine. Addition of α-solanine to the diet affected survival of seventh-instar larvae, pupae, and adults; and female fecundity and fertility. The diet containing the highest α-solanine concentration led to decreased survivorship, fecundity, and fertility. The diets supplemented with α-solanine led to increased malondialdehyde and protein carbonyl contents in midgut and fat body and the effect was dose-dependent. Dietary α-solanine led to increased midgut glutathione S-transferase activity and to decreased fat body glutathione S-transferase activitiy. We infer from these findings that α-solanine influences life history parameters and antioxidative enzyme activities in the midgut and fat body of G. mellonella.

The efficacy of a combined larvicide–adulticide in ultralow volume and fumigant canister formulations in controlling the dengue vector Aedes aegypti (Diptera: Culicidae) in Northwest of Argentina

The efficacy of an ultralow volume formulation (ULV) and fumigant canister, containing both permethrin and pyriproxyfen, was compared with that of standard permethrin applications in a field assay conducted in Banda del Río Salí, Tucumán (north-western Argentina). Five treatment areas were established: first area was sprayed with a ULV formulation of 10% permethrin, a second area was treated using a fumigant canister containing 10% permethrin and 3% pyriproxyfen, the third area was sprayed with a ULV formulation of 10% permethrin and 3% pyriproxyfen, the fourth area with ULV formulation of 10% permethrin using a portable aerosol generator and the fifth area was a left untreated area. Immature and adult Aedes aegypti individuals placed in containers and sentinel cages were positioned within the treated and control areas. The effects of treatment and time on larval, pupal and adult survival were tested. We also investigated the effects of treatment and time on the numbers of larval and pupal deaths, on the proportion of larvae that metamorphosed into pupae and adults, and on the proportion of dead adults. Larval A. aegypti survivorship in 250mL containers revealed a significant treatment effect and significant treatment × time interaction 2 and 24h after the application of the ULV treatment with 10% permethrin using the portable aerosol generator. The number of dead larvae in 20L containers differed significantly by treatment and by time. ULV treatment with 10% permethrin and 10% permethrin plus 3% pyriproxyfen using the cold fogger truck mount ULV resulted in the greatest numbers of dead larvae; most larvae died 2weeks after application. Adult A. aegypti mortality in all treatments did not differ significantly 2 and 24h after application. In addition, we found no significant differences in adult mortality between cages exposed at 3m and those at 6m from the ULV application line. However, there was a significant difference in adult mortality between the 10% permethrin treatment applied with cold fogger truck mount ULV and that applied using the portable aerosol generator (P < 0.001). The larval index known as Breteau index (BI) was higher before treatment than after treatment in different areas. After the treatments, the lowest value of BI was observed in the area treated with the fumigant canister formulation, and a long-lasting effect was observed with the formulation of 10% permethrin and 3% pyriproxyfen.

Constant Versus Fluctuating Temperatures in the Interactions Between &lt;I&gt;Plutella xylostella&lt;/I&gt; (Lepidoptera: Plutellidae) and Its Larval Parasitoid &lt;I&gt;Diadegma insulare&lt;/I&gt; (Hymenoptera: Ichneumonidae)

Laboratory studies were conducted to determine the effects of constant temperatures (7, 22, and 30°C) and corresponding fluctuating temperatures (0-14, 15-29, and 23-37°C) on the development of diamondback moth, Plutella xylostella (L.), and its North American parasitoid Diadegma insulare (Hellén). Parasitized third-instar diamondback moth larvae were reared until adult mortality in individual thermal gradient cells at different temperature regimes. Larval mortality, parasitism success, pupal mortality, larval and pupal developmental time, adult longevity, and pupal and adult dry weight were recorded. Overall diamondback moth larval mortality was low. The pupal mortality of D. insulare increased with increasing temperature; however, diamondback moth did not show such a response. Greatest parasitism success (67%) was found at constant and fluctuating 22°C and fluctuating 7°C, and the lowest (30%) at fluctuating 30°C. Longer development times and greater pupal body masses occurred at lower temperatures for both insects. Significant differences occurred between constant and fluctuating temperature regimes for most parameters of both insects. Fluctuating compared with constant temperatures caused shorter development times, similar body mass, and higher adult longevity for both insects at optimal and lower temperature ranges. Both insects experienced 0°C at fluctuating 7°C (0-14°C) and survived. These results have important implications for extrapolating temperature effects on insects in laboratory studies with constant temperatures. Comparing successful parasitism capacity of the wasp and pupal survival and body mass of both host and parasitoid, we conclude that D. insulare is a more effective parasitoid at lower temperatures.

Improvement of survival of the house fly (Musca domestica L.) larvae under mass-rearing conditions

Two new approaches were examined, aimed at increasing survival of the house fly (Musca domestica L.) larvae under mass-rearing conditions of a biodegradation facility: modification of the larval substrate and dispersal of the eggs during inoculation. The two types of pig manure used in this study (manure with sawdust and manure without sawdust) differed in terms of larval survival and nutritional value for the house fly larvae. Larval survival in manure without sawdust in the control treatment was low (46.8±2.1%) and its nutritional value for the larvae were high. Addition of 5.7% of previously biodegraded manure did not significantly affect larval survival (52.3±1.9%), but larval development was faster and the pupae were significantly smaller (14.28±0.4mg) compared to the control (16.29±0.5mg). Using alternative substrate for incubation of eggs and first-instar larvae significantly increased larval survival (63.3±3.3%) and decreased the mean weight of produced pupae (14.39±0.71mg). Overall, the weight of recovered biomass in the alternative substrate treatment increased by 14.3kg ton-1 of manure compared to the control. Larval survival in manure with sawdust was generally higher than 70%, but its nutritional value for the larvae was lower than in manure without sawdust. Dispersal of eggs over the surface of manure with sawdust significantly affected larval survival and mean weight of pupae. Larval survival was significantly lower (59.2±4.0%) and pupae were significantly heavier (18.45±0.8mg) when eggs were applied to a small area on the manure surface (spot treatment), as compared to diagonal, Z-line and multiple zig-zag dispersal (72.5±2.4 to 74.6±3.0% and 14.76±0.6 to 15.97±0.6mg, respectively). No significant differences were observed in larval survival or mean weight of pupae when comparing the diagonal, Z-line and multiple zig-zag dispersal patterns. Implementation of the techniques which improve larval survival and increase the weight of produced fly biomass may decrease demand for production of house fly eggs and, therefore, reduce the maintenance costs of adult colony, as well as increase the revenue earned by selling the products.

Cold-acclimation increases the predatory efficiency of the aphidophagous coccinellid Adalia bipunctata

Ladybirds are used in integrated pest management and augmentative biological control programs all over the world. Typically, commercial rearing of the commonly used ladybird, Adalia bipunctata, takes place at a constant temperature (25°C) which maximizes reproductive output and survival in the laboratory. However, insects are known to acclimate via physiological adjustments to their thermal environment and performance is often higher at temperatures to which they are acclimated. Thus rearing A. bipunctata at 25°C may not be optimal if they are to effectively manage aphid pests under different thermal regimes. Here, we report on the effects of rearing temperature (15, 20 and 25°C) of A. bipunctata on aphid predation at similar test temperatures and under cold semi-natural conditions. Furthermore we assessed the upper thermal critical limit of ladybirds from the three rearing temperatures using a heat knock down assay as well as the effects of rearing temperature on pupal survival and adult mass. We demonstrate that ladybirds acclimated to a certain temperature consume more aphids at that temperature than ladybirds acclimated to other temperatures. Acclimating ladybirds to cold temperatures also increased their body-size but reduced pupal survival and heat resistance, suggesting costs associated with acclimation. Our findings have implications for the application of ladybirds as bio-control agents in different thermal environments. The results can be used to improve the efficiency of pest management in biological control programs.

Each life stage matters: the importance of assessing the response to climate change over the complete life cycle in butterflies

As ectothermic organisms, butterflies have widely been used as models to explore the predicted impacts of climate change. However, most studies explore only one life stage; to our best knowledge, none have integrated the impact of temperature on the vital rates of all life stages for a species of conservation concern. Besides, most population viability analysis models for butterflies are based on yearly population growth rate, precluding the implementation and assessment of important climate change scenarios, where climate change occurs mainly, or differently, during some seasons. Here, we used a combination of laboratory and field experiments to quantify the impact of temperature on all life stages of a vulnerable glacial relict butterfly. Next, we integrated these impacts into an overall population response using a deterministic periodic matrix model and explored the impact of several climate change scenarios. Temperature positively affected egg, pre-diapause larva and pupal survival, and the number of eggs laid by a female; only the survival of overwintering larva was negatively affected by an increase in temperature. Despite the positive impact of warming on many life stages, population viability was reduced under all scenarios, with predictions of much shorter times to extinction than under the baseline (current temperature situation) scenario. Indeed, model predictions were the most sensitive to changes in survival of overwintering larva, the only stage negatively affected by warming. A proper consideration of every stage of the life cycle is important when designing conservation guidelines in the light of climate change. This is in line with the resource-based habitat view, which explicitly refers to the habitat as a collection of resources needed for all life stages of the species. We, therefore, encourage adopting a resource-based habitat view for population viability analysis and development of conservation guidelines for butterflies, and more generally, other organisms. Life stages that are cryptic or difficult to study should not be forsaken as they may be key determinants in the overall response to climate change, as we found with overwintering Boloria eunomia larvae.

Evaluation of bioefficacy of three Citrus essential oils against the dengue vector Aedes albopictus (Diptera: Culicidae) in correlation to their components enantiomeric distribution

Laboratory experiments were conducted to study the bioefficacy against Ae. albopictus of three Citrus essential oils, derived from peels of Citrus sinensis, Citrus limon, and Citrus paradise and of their components. Chiral gas chromatography analysis revealed the dominant occurrence of R-(+)-limonene and (-)-β-pinene in all three essential oils while in the case of lemon oil γ-terpinene, neral, and geranial detected also among other components. The tested Citrus essential oils were toxic against mosquito larvae with LC(50) values ranging from 25.03 to 37.03 mg l(-1). Among citrus essential oils components tested, γ-terpinene was the most toxic (LC(50) = 20.21 mg l(-1)) followed by both enantiomeric forms of limonene (LC(50) = 35.99 and 34.89 mg l(-1), for R-(+)-limonene and S-(-)-limonene, respectively). The delayed toxic effects after exposure of larvae to sublethal (LC(50)) doses were also investigated for citrus essential oils and their major component R-(+)-limonene, indicating a significant reduction of pupal survival. In repellent bioassays, lemon essential oil, S-(-)-limonene, citral (mixture of neral\geranial) and (+)-β-pinene were the most effective compared with other citrus essential oils and components against adult mosquitoes. Repellent bioassays also revealed that limonenes and β-pinenes showed an isomer dependence repellent activity. Finally, according to enantiomeric distribution of limonene and α- and β-pinene, the repellency of lemon essential oil is possibly attributed to the presence of citral.

Do small mammals prey upon an invasive ectoparasite of cervids?

Predation is often considered an important factor for population regulation and in some cases for the invasion success of prey. Small mammalian predation may be a major force in the population regulation of many ground-dwelling invertebrate species. The deer ked ( Lipoptena cervi (L., 1758)) is an ectoparasitic fly of cervids. The species has a large distribution area and it has relatively rapidly spread in northern Europe during the previous four decades. The factors possibly regulating the distribution and invasion of this fly are poorly known. During the off-host stage of several months, pupae of deer ked are likely exposed to many ground-dwelling predators. To study whether small mammals would feed on deer keds, we conducted experiments by serving pupae of deer ked to wild-captured common shrews ( Sorex araneus L., 1758), bank voles ( Myodes glareolus (Schreber, 1780)), field voles ( Microtus agrestis (L., 1761)), and semi-wild bank voles, and assessed pupal survival. As a control, we provided alternative food including common nutrients used by small mammals in their natural habitats. The results show that variable amounts of pupae of deer ked are consumed by all small-mammal species studied. Surprisingly, insectivorous and most of the time food-constrained shrews consumed less pupae than granivorous–herbivorous voles.

Rapid induced resistance of silver birch affects both innate immunity and performance of gypsy moths: the role of plant chemical defenses

In this study we tested the effects of rapid induced resistance of the silver birch, Betula pendula, on the performance and immune defense of the gypsy moth, Lymantria dispar. We also measured the effects of defoliation on the concentrations of plant secondary metabolites, particularly on phenolics and terpenoids. It was found that severe natural defoliation (by moth larvae) of silver birch led to an increase in lipophilic flavonoids on the leaf surface. The concentration of some simple phenolics and monoterpenes (linalool and geraniol) also increased, while that of several glycosides of quercetin decreased. The female pupal weights and survival rates of moths decreased, and larval development time increased, when the insects fed on defoliated trees. However, the feeding of caterpillars with the leaves of defoliated trees led to an increase in lysozyme-like activity in their hemolymph, with an increase in their ability to encapsulate potential parasites. Our data show that the silver birch deploys a rapid chemical defense against gypsy moth larvae. We suggest that lipophilic flavonoids are important compounds in the direct silver birch defense against L. dispar caterpillars. The increased strength of immune defense of insects exposed to trees that had deployed a rapid induced resistance may be an adaptation of the herbivores to resist the rising density of parasites when host population density is high.