Larval Development Time Research Articles

Effect of larval density and additional anchoring surface on the life-history traits of a laboratory colonized Anopheles funestus strain.

Optimal rearing conditions, inclusive of larval rearing density, are critical for sustained mosquito productivity. There is limited information on favourable conditions for the larval rearing of Anopheles funestus, the dominant malaria vector in east and southern Africa. This work investigated the effects of larval rearing densities and additional anchoring surface on An. funestus development using a life table approach. Larval cohorts were reared at four different larval densities using the same rearing surface area, larval food concentrations and temperature conditions. Rearing larvae at high densities extended the larval developmental time and reduced adult productivity. Adding an extra larval anchoring surface when rearing larvae at high density resulted in extended larval developmental time, increased larval survivorship and produced bigger adults. These findings improve our understanding of the relationship between larval density and developmental traits in An. funestus and provides baseline information for An. funestus rearing under laboratory conditions.

Influência do regime de chuvas do bioma Cerrado na manutenção das armadilhas de larvas e na morfologia dos adultos de Myrmeleon brasiliensis (Navás) (Neuroptera: Myrmeleontidae)

ABSTRACT Seasonality in the Cerrado biome of Brazil is characterized by a dry season and a rainy season, affecting the availability of water and generating nutritional limitations. Thus, plants and animals have developed adaptive mechanisms in order to survive in this environment. Insects known as antlions (Neuroptera: Myrmeleontidae) occur in areas of the Cerrado and build traps in dry soil to capture prey items. In the rainy season, these insects are unable to forage due to the waterlogged soil. The aim of this study was to investigate the influence of the rainfall regime in the Cerrado on aspects of trap-building behavior, larval development and morphological characteristics of adult antlions. Larvae of the antlion Myrmeleon brasiliensis (Návas, 1914) were observed and collected in an area of the Cerrado biome in the municipality of Aquidauana (MS), Brazil. Observations were performed in the rainy and dry seasons to determine the abundance of traps built by M. brasiliensis larvae. In the laboratory, experiments were performed involving the manipulation of the frequency of simulated rain on the traps. The results revealed that variations in rainfall due to seasonality in the Cerrado affect M. brasiliensis larvae, with greater foraging observed in the dry season. The laboratory experiments demonstrated that differences in the frequency of rains affect the mortality of the larvae, larval development time and the size of the adults. Thus, variations in rainfall patterns can lead to variations in the characteristics of the population structure of M. brasiliensis in areas of the Cerrado biome in Brazil.

Effect of different diet on the survivorship, life cycle, and fecundity of eri silkworm Samia cynthia ricini Boisduval (Lepidoptera: Saturniidae)

Abstract Cassava (Euphorbiaceae), castor (Euphorbiaceae), and tropical almond (Combretaceae) have been suggested as three different possible natural diet sources for Samia cynthia ricini (Drury, 1773) (Lepidoptera: Saturniidae), a species of silkworm that is reared in Indonesia because it is able to produce good-quality silk. This research aims to study the effect of the types of diet on the survivorship, development time, and fecundity of S. c. ricini. The research was conducted by giving the three types of diet to S. c. ricini. The survival rate, development time, and adult fecundity were observed. The results showed that S. c. ricini had a high survival rate when fed on cassava and castor. However, S. c. ricini larvae died when fed tropical almond. A significant difference in the total larval development time occurred when S. c. ricini was fed on cassava and castor. Larvae developed more quickly when fed on the castor diet compared to the cassava diet. Moreover, the total development time is also faster when they fed castor. The pupal weight and fecundity of adult female S. c. ricini reared on castor were higher than those of adult females reared on cassava. This study implies that castor is the more suitable diet for S. c. ricini and cassava can be used as an alternate diet.

Determination of Almond Saw Fly (Cimbex quadrimaculata Müller, 1766, hymenoptera: cimbicidae)’s larval development time in controlled conditions

The study was conducted to compare the larval development stages, cocoon knitting and cocoon completion of Cimbex quadrimaculata (Müller, 1766) (Hymenoptera: Cimbicidae) in climate cabinets where 65% humidity, 25C ± 2 °C and 30C ± 2 °C temperature and 16:8 illumination conditions are provided. A statistically significant difference was found between 25 ºC and 30 ºC in terms of larval development times. It has been determined that as the temperature increases, the duration of the advanced larval stages shortens, and at 30 ºC, it has been observed that the larval development stages, cocoon knitting and full cocoon time are statistically shorter. These data have the characteristics of being the basis study for determining the biology of the pest under controlled conditions. The data of the study is important in terms of the bioecology and control of the pest.

Nutritional phenotype underlines the performance trade-offs of Drosophila suzukii on different fruit diets

Animals confined to different dietary conditions often exhibit distinct, sometimes contrasting, nutritional phenotypes and performance outcomes. This is especially true for many oviparous insects whose developmental diets can vary depending on the mother's egg-laying site selection. Much research on the relationship between preference and performance in insects has focused on larval success, which overlooks the complexities of dietary effects on diverse performance parameters across life stages and potential trade-offs between those parameters. Furthermore, the connection between diet-induced nutritional phenotype and performance trade-offs is not well understood. Here, using Drosophila suzukii, we quantify multiple performance indices of larvae and adults reared on five host fruits of different protein-to-sugar ratios (P:S) which have previously been shown to differ in attractiveness to fly foraging and oviposition. Our results demonstrate robust diet-specific performance trade-offs, with fly fecundity, larval development time, pupal size, and adult weight superior in flies reared on the high P:S raspberry diet, in contrast to the low P:S grape diet; but the reverse was found in terms of adult starvation resistance. Notably, the contrasting performance trade-offs are readily explained by the fly nutritional phenotype, reflected in the protein and energy (glucose and lipid) contents of flies reared on the two fruits. Together, our results provide experimental evidence for metabolic plasticity of D. suzukii reared on different fruits and the possibility of using adult nutritional phenotype as a marker for diet and performance outcomes.

Evaluating the effects of Bt protein Vip3Aa on immature Propylea japonica (Thunberg) (Coleoptera: Coccinellidae)

BackgroundGenetically modified (GM) crops have become a common tool for managing insect pests of economic importance. However, before their commercialization, bio-safety evaluation on non-target arthropods such as pollinators and biological control agents is a pre-requisite to save services rendered by them in agro-ecosystem.ResultsIn the present experiment, the potential adverse effects of Bt protein (Vip3Aa) were studied on the life table parameters (pupation and emergence rates, 7-day larval weights, larval development time, and adult weight) of a predatory beetle, Propylea japonica (Thunberg) (Coleoptera: Coccinellidae) in the laboratory. P. japonica was exposed to Bt protein incorporated in synthetic diet at the rate of 200 µg/g of fresh weight of diet. Temporal stability, bioactivity and the uptake of insecticidal protein were confirmed by enzyme-linked immunosorbent assay and a sensitive insect bioassay. The results indicated that pupation and adult emergence rates did not differ significantly from that of negative control (pure synthetic diet). Similarly, the fresh weight of male and female adults emerged in Vip3Aa treatment (2.87 mg and 3.86 mg, respectively) did not vary significantly from that of the negative control treatment (2.66 mg, 3.75 mg). However, the time taken by the larvae to complete their development (12.70 days) was significantly extended than that of the negative control (10.21 days). In contrast, the tested life-table parameters of P. japonica were adversely affected when fed on synthetic diet containing boric acid (positive control) indicating experimental fitness to detect adverse effects.ConclusionsOn the basis of the results, it is suggested that GM crops expressing Bt protein (Vip3Aa) are safe for non-target insects such as P. japonica and are compatible with other biological programs for the integrated management of insect pests.

Response of Spodoptera frugiperda (Lepidoptera: Noctuidae) to salt‐stressed maize plants

AbstractSalt‐stressed maize is an economically important crop in many arid and semi‐arid regions of the world where soil salinization is most common, and the invasive fall armyworm (FAW) Spodoptera frugiperda threatens global maize production. It thus poses a puzzle of whether FAW populations feeding on salt‐stressed maize plants are becoming more or less invasive. Here, we evaluated the FAW response to salt‐stressed maize plants by examining effects of salt‐stressed maize plants on FAW survival, development and fecundity. We found a longer larval development time (salt‐stressed, 12.9 ± 0.8 d; non‐stressed, 11.3 ± 0.4 d), but unaffected survival rate and pupal mass accumulation in FAW feeding on salt‐stressed maize plants. Moreover, the lifetime egg production of FAW females feeding on salt‐stressed maize plants (633.5 ± 62.7 eggs) was reduced by nearly half compared with those feeding on non‐stressed maize plants (1255.9 ± 70.3 eggs). Overall, FAW showed a negative response to salt‐stressed maize plants. Due to limited population increase potential, FAW populations feeding on salt‐stressed maize plants should pose less of a problem than ones feeding on non‐stressed maize plants do. In practice, salt‐stressed maize plants are quite common in arid and semi‐arid regions where the relatively high‐salinity groundwater is often used to irrigate maize plants, potentially limiting FAW population size. Thus, salt‐stressed maize plants would contribute to practical applications of integrated pest management (IPM) strategies in controlling FAW.

Copper and zinc impact on stress biomarkers and growth parameters in a model organism, Galleria mellonellalarvae.

The objective of the present study was to investigate the impact of zinc and copper on some biomarkers in a model organism Galleria mellonella L. We investigated the effects of Cu and Zn (10, 50, and 100mg/100 g diets) on different biomarkers such as oxidative stress parameters (SOD and CAT activities and MDA levels), energy resources (protein, lipid and glycogen levels), electrolyte contents (Ca, Na, and K levels), total hemocyte count (THC), and growth and development of G. mellonella. Additionally, the accumulation levels of the used metals were also studied. Cu caused a significant decrease in protein, lipid and glycogen levels. SOD and CAT activities significantly increased at all concentrations of Cu, while they significantly increased at only high concentrations of Zn (50 and 100mg). Lipid peroxidation levels (MDA) significantly elevated at high concentrations of both metals. It was determined that the Cu and Zn accumulation increased depending on the increase of the concentration. Zn caused an alteration in Ca level at the concentrations of 50 and 100mg, and K and Na levels at all concentrations. While, THC significantly reduced at all Cu concentrations, this reduction was observed only at higher Zn concentrations (50 and 100mg). Larval and pupal development time significantly extended at the highest concentration (100mg) of Cu, and females' lifespan significantly shortened at all concentrations of Cu. Zinc caused an extension in larval development time at the highest concentration (100mg), and caused a shortening in females and males' lifetime at all concentrations.The observed changes in biomarkers can be used as the illustration of potential toxic effects of high levels of Cu and Zn in organisms.

A bioenergetic approach for a novel aquaculture species, the giant barnacle Austromegabalanus psittacus (Molina, 1788): Effects of microalgal diets on larval development and metabolism

Acorn barnacle aquaculture is a new activity based on species that possess potential due to several production advantages (e.g., no selective filters and rapid growth at very high densities). Extensive cultures have been developed in Chile and Portugal, but its settler (early juvenile) supply shows a high seasonal variability, which promotes the development of settler supplies from hatchery production. The effect of culture conditions on naupliar stages, cyprid and newly metamorphosed juvenile are key for hatchery production. Using the giant barnacle Austromegabalanus psittacus as model, we examined the effects of microalgae diets (Isochrysis galbana, Chaetoceros gracilis and a Mix 1:1 ratio) and concentration (2 × 105, 4 × 105 and 6 × 105 cells mL−1) on developmental time, mortality and metabolism (oxygen consumption, ammonia excretion and O:N ratio) from naupliar stages (NII-NVI) to cyprid stage. A bioenergetic approach was suggested to quantify how culture conditions influenced net growth efficiency for naupliar stages, as well as energy losses from cyprid and to newly metamorphosed juvenile. Nauplii fed with I. galbana did not fully complete naupliar stages, reaching a 100 % mortality at NIV stage. Overall, the shortest larval development time was observed at C. gracilis/2 × 105 cells mL−1 treatment along naupliar stages. The highest cyprid mortality was found in larvae fed during their development as nauplius with mixed diet at 2 × 105 cells mL−1. No differences in respiration and ammonia excretion rates between the treatments of each larval stage were found, with exception of cyprid from mix/2 × 105 cells mL−1. The highest dry weight of the cyprid and highest lipid content was obtained in C. gracilis/6 × 105 cells mL−1. The energy content provided by lipids and proteins for cyprid was significantly affected by diet and concentration. Outcomes from this study demonstrated that microalgae type and concentration have an important influence on larval development, survival and energy accumulation in A. psittacus.

Balance between larval and pupal development time in carrion blowflies

Several studies have highlighted the impact of environmental factors such as food type or larval density on the development of blowfly larvae. We investigated how changes in development speed (due to larval density and group composition) are divided among feeding and post-feeding stages. Even if these parameters impinge only on feeding larvae, they may ultimately also affect their subsequent development, and especially metamorphosis duration. Therefore, this study analysed the effect of larval density and group composition on the rhythm of necrophagous blowfly development. Based on laboratory studies, we highlighted that Calliphora vicina individuals with a fast development during their feeding phase developed slower in the later post-feeding phase (i.e., they had a compensatory effect). Lucilia sericata, a calliphorid species also frequently found on carrion at the same time as C. vicina, showed a different developmental strategy by not making its post-larval development speed dependent on the larval development speed. Finally, while a compensatory effect may exist, variations in the development rate more often accumulate through life-stages and resulted in a larger variability for later development instars. In this respect, the inclusion of detailed development duration covering all life stages, including post-feeding, is recommended in future studies, especially those dedicated to forensic entomology.

Sensitivity of midgut physiological parameters of Lymantria dispar L. larvae to benzo[a]pyrene in populations with different multigeneration contact to environmental pollutants

Accumulation of organic pollutants in the environment calls for sensing physiological parameters adequate to indicate the presence of contaminants and their effects on ecosystems. Evidence points to the importance of insect adaptations in their habitats for the assessment of sensitive biomarkers so we examined the influence of origin and multigenerational adaptations of the Lymantria dispar larvae to chronic benzo[a]pyrene (B[a]P) treatment under laboratory conditions. The main aim was to compare reactions of larvae from unpolluted and polluted forests using alkaline phosphatase (ALP), acid phosphatase (ACP), and carboxylesterase (CE) specific activities in the midgut, including electrophoretic isoform patterns; midgut expression levels of Hsp70, larval development time (DT), and midgut mass (MM), after chronic exposure to 5 and 50 ng of B[a]P/g dry food weight. The biomarker potential of these parameters regarding larval pre-exposure history to pollution was estimated by principal component analysis (PCA). B[a]P treatment resulted in inhibition of ALP activity, a rise of CE activity, and reduction of MM in larvae from the unpolluted forest, while the population from the polluted forest showed significant elevation of Hsp70 expression in the midgut, prolonged DT, and reduction of MM. PCA confirmed variations in responses of the selected parameters regarding population origin. The obtained results provide insight into insect population variability concerning physiological responses to pollutants. It is indicative that all investigated physiological parameters of L. dispar larvae showed origin-dependent responses to long-term presence of B[a]P, which may be of great importance in ecotoxicological research.

Strain matters: strain effect on the larval growth and performance of the yellow mealworm,Tenebrio molitor L.

Much research has been directed towards the optimisation of the mass rearing of the yellow mealworm,Tenebrio molitor, in terms of diet and rearing conditions. However, an issue that has not been thoroughly investigated to date is the strain effect on the larval growth and performance ofT. molitor. To close this gap, the plasticity in growth and development, as well as the feed conversion efficiency and the nutritional composition of larvae of sevenT. molitor strains of different geographic origins (Greece, Italy, Germany, Turkey, Spain and USA) were comparatively evaluated in the present study. Based on the results, there were considerable differences in the performance of the strains tested. Larval weight at harvest was the highest for a strain originated from Germany; however, the higher final body mass was at the cost of longer development time and higher feed intake, the latter having a negative impact in the overall performance and productivity of the strain. No significant differences were detected in the larval nitrogen and lipid content among the strains tested. In overall, the Italian strain II had the best growth performance in terms of survival, larval biomass production, development time and feed utilisation. The present study aims to highlight the need for selection of strains with enhanced performance and production traits for mass-production, which will boost the overall productivity of insect farming systems.

Fitness comparison of Plutella xylostella on original and marginal hosts using age-stage, two-sex life tables.

The diamondback moth, Plutella xylostella, is an important agricultural pest that severely damages cruciferous vegetables. Although previously considered a threat only to Brassica species, P. xylostella has been observed to feed on noncruciferous vegetables. Here, we established a population of P. xylostella on the pea Pisum sativum (PxP population). We compared this PxP population's performance on the pea host plant to a population (PxR) reared on the original host plant radish (Raphanus sativus) for several generations using an age‐stage, two‐sex life table and analyzed the correlations between different fitness parameters. In the 1st generation of the PxP population, survival rate of immature stage was 17%, while the survival rate of PxR was 68%; the duration of the 4th larval instar (5.30 d) and mortality (25%) of this generation were significantly longer (2.8 d) and higher (1%) than that of PxR, respectively (both p < .001). Upon long‐term acclimation, the PxP fitness improved significantly, especially that the survival rate of immature stages increased to approximately 60% in the 15th, 30th, and 45th generations. However, PxP feeding on pea exhibited poorer fitness with longer larval developmental time, shorter total life span, lighter pupa, and lower fecundity in different generations compared with PxP feeding on radish. PxP feeding on pea also showed a significantly lower intrinsic rate of increase (r), net reproduction rate (R 0), finite increase rate (λ), and longer mean generation time (T) than PxP feeding on radish in all generations tested. Significant positive correlations were observed between pupal weight and female fecundity in pea‐fed populations, and between female longevity and female fecundity in pea‐fed and radish‐fed populations. Our findings suggest that P. xylostella adaptation to pea does not improve overall fitness compared with the original host radish, making pea a marginal host for P. xylostella.

The effects of adaptation to urea on feeding rates and growth in Drosophila larvae.

A collection of forty populations were used to study the phenotypic adaptation of Drosophila melanogaster larvae to urea‐laced food. A long‐term goal of this research is to map genes responsible for these phenotypes. This mapping requires large numbers of populations. Thus, we studied fifteen populations subjected to direct selection for urea tolerance and five controls. In addition, we studied another twenty populations which had not been exposed to urea but were subjected to stress or demographic selection. In this study, we describe the differentiation in these population for six phenotypes: (1) larval feeding rates, (2) larval viability in urea‐laced food, (3) larval development time in urea‐laced food, (4) adult starvation times, (5) adult desiccation times, and (6) larval growth rates. No significant differences were observed for desiccation resistance. The demographically/stress‐selected populations had longer times to starvation than urea‐selected populations. The urea‐adapted populations showed elevated survival and reduced development time in urea‐laced food relative to the control and nonadapted populations. The urea‐adapted populations also showed reduced larval feeding rates relative to controls. We show that there is a strong linear relationship between feeding rates and growth rates at the same larval ages feeding rates were measured. This suggests that feeding rates are correlated with food intake and growth. This relationship between larval feeding rates, food consumption, and efficiency has been postulated to involve important trade‐offs that govern larval evolution in stressful environments. Our results support the idea that energy allocation is a central organizing theme in adaptive evolution.

No influence on population dynamics of spider mites in cotton fields of intercropping with walnut, a poor-quality host

Intercropping is a common agricultural practice used to improve crop yields and profits; however, the intercrop species and its quality as a host for the main crop's key pests can affect the pests' population dynamics under intercropping conditions. Fruit trees - cotton intercropping systems are commonly applied in Xinjiang of China, and previous studies have confirmed that intercropping of cotton with species (e.g., jujube and apple) that are good spider mite hosts can increase the spider mite density in cotton. In this study, the effect of intercropping cotton with walnut, which is a poor host for the key spider mite pest Tetranychus truncatus, was examined. For this spider mite, feeding on walnut leads to significantly longer development time for larvae + nymphs and a short oviposition period which leads to a lower total fecundity, lower survival rate and lower intrinsic growth rate (rm) compared to cotton. Correspondingly, in the two-year, multiple-scale field study, we found that the population dynamics of spider mites in cotton did not significantly differ in the field plots between a walnut-cotton intercropping system and monocultural cotton. Similar trends of spider mite density were also observed in commercial fields. Based on previous work and the current study on fruit tree-cotton intercropping systems, we concluded that while intercropping cotton with intercrop species that are suitable spider mite hosts increase the spider mite population in intercropped cotton, the use of a poor host plant such as walnut has no significant effect on spider mites populations in cotton. Hence, our study results improved the understanding of pest management and monitoring in intercropped cotton systems.

Characterization of life-history parameters of an Anopheles funestus (Diptera: Culicidae) laboratory strain.

The colonization of the African malaria vector Anopheles funestus has been hampered by inadequate knowledge of its mating and development under laboratory conditions. Life-tables are routinely used to provide baseline biological characteristics needed for colonization. This study characterized age-specific life-table attributes of an existing An. funestus laboratory strain to gain insight into factors that are critical for its colonization. To achieve this, the An. funestus laboratory strain was reared from eggs to adulthood under standard insectary conditions, monitoring and characterizing each developmental stage. The mean insemination rate of females was 74.8% with an average egg load of 67.1 eggs/female and a mean fertility of 86.7%. The mean developmental time from 1st instar larvae (L1) to pupation was 16.4 days. The mean proportion of L1 that survived to pupation was 72.9%. On average, 78.8% of the pupae successfully eclosed as adults. The median longevity for adult males and females was 44 and 28 days, respectively. This work constitutes the first report on life-table characterization of an An. funestus strain. The larval developmental time was within the range reported for wild An. funestus while adult longevity was higher compared to survivorship observed in wild populations. These data demonstrate that the colonized An. funestus strain has potential to be re-colonized under standard insectary conditions. The study provides base-line information for further studies on identifying critical parameters for the maintenance of An. funestus under artificial conditions.

Disparate genetic variants associated with distinct components of cowpea resistance to the seed beetle Callosobruchus maculatus.

Polygenic genome-wide association mapping identified two regions of the cowpea genome associated with different components of resistance to its major post-harvest pest, the seed beetle Callosobruchus maculatus. Cowpea (Vigna unguiculata) is an important grain and fodder crop in arid and semi-arid regions of Africa, Asia, and South America, where the cowpea seed beetle, Callosobruchus maculatus, is a serious post-harvest pest. Development of cultivars resistant to C. maculatus population growth in storage could increase grain yield and quality and reduce reliance on insecticides. Here, we use a MAGIC (multi-parent, advanced-generation intercross) population of cowpea consisting of 305 recombinant inbred lines (RILs) to identify genetic variants associated with resistance to seed beetles. Because inferences regarding the genetic basis of resistance may depend on the source of the pest or the assay protocol, we used two divergent geographic populations of C. maculatus and two complementary assays to measure several aspects of resistance. Using polygenic genome-wide association mapping models, we found that the cowpea RILs harbor substantial additive-genetic variation for most resistance measures. Variation in several components of resistance, including larval development time and survival, was largely explained by one or several linked loci on chromosome 5. A second region on chromosome 8 explained increased seed resistance via the induction of early-exiting larvae. Neither of these regions contained genes previously associated with resistance to insects that infest grain legumes. We found some evidence of gene-gene interactions affecting resistance, but epistasis did not contribute substantially to resistance variation in this mapping population. The combination of mostly high heritabilities and a relatively consistent and simple genetic architecture increases the feasibility of breeding for enhanced resistance to C. maculatus.

Insecticide resistance exerts significant fitness costs in immature stages of Anopheles gambiae in western Kenya

BackgroundDespite increasing documentation of insecticide resistance in malaria vectors against public health insecticides in sub-Saharan Africa, there is a paucity of information on the potential fitness costs of pyrethroid resistance in malaria vectors, which is important in improving the current resistant management strategies. This study aimed to assess the fitness cost effects of insecticide resistance on the development and survival of immature Anopheles gambiae from western Kenya.MethodsTwo-hour old, first instar larvae (L1) were introduced and raised in basins containing soil and rainwater in a semi-field set-up. Each day the number of surviving individuals per larval stage was counted and their stage of development were recorded until they emerged as adults. The larval life-history trait parameters measured include mean larval development time, daily survival and pupal emergence. Pyrethroid-resistant colony of An. gambiae sensu stricto and susceptible colony originating from the same site and with the same genetic background were used. Kisumu laboratory susceptible colony was used as a reference.ResultsThe resistant colony had a significantly longer larval development time through the developmental stages than the susceptible colony. The resistant colony took an average of 2 days longer to develop from first instar (L1) to fourth instar (L4) (8.8 ± 0.2 days) compared to the susceptible colony (6.6 ± 0.2 days). The development time from first instar to pupa formation was significantly longer by 3 days in the resistant colony (10.28 ± 0.3 days) than in susceptible colony (7.5 ± 0.2 days). The time from egg hatching to adult emergence was significantly longer for the resistant colony (12.1 ± 0.3 days) than the susceptible colony (9.6 ± 0.2 days). The pupation rate (80%; 95% (CI: 77.5–83.6) vs 83.5%; 95% (CI: 80.6–86.3)) and adult emergence rate (86.3% vs 92.8%) did not differ between the resistant and susceptible colonies, respectively. The sex ratio of the females to males for the resistant (1:1.2) and susceptible colonies (1:1.07) was significantly different.ConclusionThe study showed that pyrethroid resistance in An. gambiae had a fitness cost on their pre-imaginal development time and survival. Insecticide resistance delayed the development and reduced the survivorship of An. gambiae larvae. The study findings are important in understanding the fitness cost of insecticide resistance vectors that could contribute to shaping resistant management strategies.

Flower diet enhances Adalia bipunctata larval development significantly when prey is limited

AbstractPredaceous coccinellids can feed on non‐prey food, but the ecological value of this feeding to maintain a coccinellid population is not well understood. Prey density can vary greatly in the field, whereas non‐prey food sources such as pollen and nectar are more predictable. In the present study, Adalia bipunctata L. (Coleoptera: Coccinellidae) larval performance on pure and mixed diets of a high‐quality non‐prey food with varying amounts of prey was investigated. Rosy apple aphid, Dysaphis plantaginea Passerini (Hemiptera: Aphididae), served as prey in the experiment and was given to A. bipunctata larvae either ad libitum as a surplus diet or as a limited diet, the amount of which was selected so that it would limit larval development, according to a pilot study. Flowers of buckwheat, Fagopyrum esculentum L. (Polygonaceae), a high‐value floral diet, served as the non‐prey food. Newly hatched A. bipunctata larvae were reared on each of five diets: (1) flowers only, (2) limited prey only, (3) limited prey plus flowers, (4) surplus prey only, (5) surplus prey plus flowers. Larval survival, developmental time, and adult dry weight were measured. The addition of floral diet had a significant positive impact on A. bipunctata larval survival and development when prey diet was limited, survival ratio was 6× higher and developmental time was 25% shorter. In conclusion, A. bipunctata immature development can benefit from a floral diet supplemented to a prey diet, which indicates that the use of flowers in cropping systems can help to enhance biocontrol services by A. bipunctata.

زیست شــناسی مگـس مینـوز خـار پنبــه Pegomya terebrans (Diptera: Anthomyiidae) در منطــقة ارومــیه، ایــران

Field and laboratory surveys were carried out to study the biology of cotton thistle leaf miner, Pegomya terebrans (Rondani) in Urmia region. The results showed that the host plant species of this fly are restricted to three species of plants belonging to tribe Cynareae (Asteraceae), including Italian thistle Carduus pycnocephalus L. and two species of cotton thistle namely Onopordum acanthium L. and O. leptolepis DC.. The species has only one generation per year and hibernates as adults. After overwintering, adults become active and mate in late March. Fertile females begin oviposition in early April. The eggs are laid either singly or in groups of up to five in irregular shape under the leaves of the host plants. Depending on the daily temperature, they hatch within 6-10 days and young larvae immediately bores into the leaf and begins consumption in tissues between the leaf surfaces. The species has three larval instars and larval developmental time is 21 to 27 days in natural conditions. The full grown third instar larvae fall to the ground and pupate in the soil at a depth of 1 to 3 cm which its period lasts 4 to 5 months. The emergence of flies begins in mid-October and continues until late-November. They remain inactive for about five months in autumn and winter and become active in early spring, again. The larvae of P. terebrans were parasitized by Biosteres spinaciae (Thomson) in the studied region. Parasitic association between B. spinaciae and P. terebrans is reported for the first time.