Duration Of Larval Stages Research Articles

Effects of Some Heavy Metals on the Life-Table Parameters of Anopheles stephensi (Liston) (Diptera: Culicidae)

1 Asst. Prof. and Head, Zoology Department, N.M.S.N. Dass (P.G.) College, Budaun 243 601 INDIA 2 Former Professor and Head, Department of Animal Science, M.J.P. Rohilkhand University, Bareilly 243 007 INDIA Abstract The exposure sub lethal doses of three heavy metals, Cd, Fe and Mn as solutions of CdCl2, FeCl3 and MnCl2 resulted a variable increase in mortalities of various life stages (L1-L4, pupa), adult emergence and generation morality (k-factor). On the other hand, the developmental duration of various larval stages was declined significantly in early or late instars. Beside toxic and adverse effects of Cd, Fe and Mn salts on survival and longevity, stress of these heavy metals was found as accelerating factor for the larval development.

Egg Hatch and Survival and Development of Beet Webworm (Lepidoptera: Crambidae) Larvae at Different Combinations of Temperature and Relative Humidity.

To understand the role that temperature and humidity play in the population dynamics of the beet webworm, Loxostege sticticalis L. (Lepidoptera: Crambidae), egg hatch, survival of first-fifth instars, survival of the full larval stage, survival curves, and larval development rates were investigated at combinations of four temperatures (18, 22, 26, and 30°C) and five relative humidities (RH; 20%, 40%, 60%, 80%, and 100%). We found that greatest egg hatch rate, survival rates of the first and second instars, and survival rate of the complete larval stage occurred at 22°C and 60-80% RH; the lowest values for these parameters were observed at 30°C and 20% RH. Survival of first instars was significantly affected by the interaction of temperature and relative humidity. However, survival of third and fourth instars was neither affected by temperature nor relative humidity, and that of fifth instars was significantly affected only by relative humidity level. The survival curve for larvae was well described by a type III Weibull distribution. Duration of larval stage decreased as temperature increased, but was not affected by relative humidity. We therefore conclude that eggs and early instars are the most critical stages for survival to the pupal stage, and 22-26°C and 60-80% RH are the optimum conditions for their survival and development. These findings confirm that temperature and relative humidity are the critical environmental factors affecting the population growth of L. sticticalis, with temperature being more important.

Comparison of Population Genetic Structure of Two Seashore-Dwelling Animal Species, Periwinkle Littorina brevicula and Acorn Barnacle Fistulobalanus albicostatus from Korea

The genetic structure of marine animals that inhabit the seashore is affected by numerous factors. Of these, gene flow and natural selection during recruitment have strong influences on the genetic structure of seashore-dwelling species that have larval periods. Relative contributions of these two factors to the genetic structure of marine species would be determined mainly by the duration of larval stage. The relationship between larval period and genetic structure of population has been rarely studied in Korea. In this study, genetic variations of cytochrome oxidase subunit I (COI) were analyzed in two dominant species on rocky shore habitats in the Korean peninsula: periwinkle Littorina brevicula and acorn barnacle Fistulobalanus albicostatus. Both species are not strongly structured and may have experienced recent population expansion. Unlike periwinkle, however, barnacle populations have considerable genetic variation, and show a bimodal pattern of mismatch distribution. These results suggest that barnacle populations are more affected by local adaptation rather than gene flow via larval migration. The bimodal patterns of barnacle populations observed in mismatch distribution plots imply that they may have experienced secondary contact. Further studies on seashore-dwelling species are expected to be useful in understanding the evolution of the coastal ecosystem around Korean waters.

Post-embriononic development of Chrysomya putoria(Diptera: Calliphoridae) on a diet containing ampicillin in different concentrations.

Here we evaluate the effects of different concentrations of the antibiotic ampicillin on the growth and development of Chrysomya putoria. Third-generation, first instar larvae (L1) reared on 60 grams of homogenate+agar 65% were treated with ampicillin sodium. The experiment consisted of four replicates (40 larvae/replicate) of each antibiotic concentration tested (T1: 466µg/mL ; T2: 81.33 mg/mL and T3: 166.66mg/mL) and a T4: control. The body mass of the mature larvae, after they abandoned the diet, were recorded in batches of five. The variation between the mean body mass of larvae and the duration of larval and pupal stages, and overall duration of the development, viability and normal rates were analyzed by ANOVA. There were no significant differences between the four treatments in the following parameters: body mass of larvae that discontinued the diet as well as the duration of larval, pupal, and total development. The sex ratios found in the four treatments did not differ from those expected. Normality rates were 100% for all treatments. There were no significant differences between treatments for larval and overall viability, but pupal viability differed significantly between T1 and the control, T1 and T2, and between the control and T3. The antibiotic did not appear to significantly alter the development of C. putoria.

Malpighia emarginata DC. bagasse acetone extract: Phenolic compounds and their effecton Spodoptera frugiperda(J.E. Smith) (Lepidoptera: Noctuidae)

Annually, several tons of residues that are rich in phenolic compounds are produced during the processing of acerola (Malpighia emarginata DC.) juice. Adding value to these residues is of great interest, since they can be a viable solution in the search for natural substances with insecticidal action and low impact on the environment and humans. Taking into account the economic losses from the attacks by the fall armyworm Spodoptera frugiperda (J.E. Smith) (Lepidoptera: Noctuidae) in different crops, the objective of this study was to evaluate the effect of the extract of acerola bagasse flour (ABF) against this insect and determine the phenolic compounds in this extract. Bagasse of acerola (BRS238 or Frutacor clon) generated after juice production, was frozen and lyophilized. To obtain the extract, 6 g ABF was mixed with 60 mL acetone:water solution (7:3 v/v), and the extract was lyophilized. Spodoptera frugiperda caterpillars, 48 h-old, obtained by the maintenance breeding, were transferred to glass tubes supplied with an artificial diet containing the ABF extract at 0, 250, 500, 1000, and 2000 mg L-1 diet. The following variables were evaluated: duration and survival of larval and pupal stages, pupal weight, sex ratio, adult longevity, oviposition period, number of egg masses, and total number of eggs. The ABF extract contained several phenolic compounds including gallic acid, epigallocatechin gallate, catechin, p-coumaric acid, salicylic acid, and quercetin. The extract was toxic to S. frugiperda, prolonging the pre-pupal stage and increasing the mortality of caterpillars.

Identification of single nucleotide polymorphisms in soybean associated with resistance to common cutworm (Spodoptera litura Fabricius)

Common cutworm (CCW; Spodoptera litura Fabricius) is a major leaf-eating insect that affects soybean crops in central and southern China. Understanding CCW-associated traits in soybean will provide insights for improved breeding strategies for resistance. The purpose of this study was to explore the genetic mechanisms underlying resistance to CCW. In this study, one natural population consisting of 219 soybean landraces from a wide geographic range was employed. Three traits, namely larval weight (LW), duration of larval stage (DLS) and pupal weight (PW) were evaluated as indicators for CCW resistance. Using 1536 single nucleotide polymorphisms (SNPs), a genome-wide association analysis was conducted to identify genomic regions associated with LW, DLS and PW in this natural population. Seven SNP-trait associations were identified using a mixed linear model (MLM). Four SNPs were co-associated with two traits. Three loci were significantly associated with CCW-resistance. Most of the detected loci were located within genomic regions previously identified as quantitative trait loci (QTLs) for these traits. The region on chromosome 6, which co-associated with LW and DLS, included several QTLs for reaction to disease or insect, such as Fusarium virguliforme, corn earworm and bean pyralid. On chromosome 7, two SNPs have been reported to associate with CCW, corn earworms, soybean aphid and bean pyralid moth infestations. Two putative genes (MYC2-like and JAM2-like) on chromosome 7 that may be associated with resistance to CCW were identified. These markers, located in previously reported QTLs, are consistent with previous findings and may represent important targets for the identification of CCW resistance-related genes. These results may provide a profound understanding of the genetic basis for resistance to CCW in soybean and the foundation for resistance to biotic stress through marker-assisted selection breeding strategies for CCW.

FECUNDIDAD Y PRIMERAS FASES DEL DESARROLLO LARVAL DE LA ASCIDIA ECTEINASCIDIA TURBINATA (ASCIDIACEA: PEROPHORIDAE) EN CUBA

Zooids (the total amount of ovocytes, embryos, and larvae in larval release stage zooids), colonial (zooids mean fecundity per number of mature zooids on resorption or releasing larvae colonies) fecundity and the characteristics and duration of the early larval stages of the ascidian Ecteinascidia turbinata (Ascidiacea: Perophoridae) are given. The ascidian colonies were collected from non-estuarine mangroves in the NW region of Cuba. An average of 41 ± 12 ovocytes, embryos, and larvae were counted in 200 zooids of 17- 31 mm length from 20 colonies gathered during different months and sites. Ascidian colonies of 163 mm length and 252 zooids average produced 10590 larvae as average per colony during each generation-degeneration cycle that lasts about 40 days. Zooids and colonial fecundity were very variable in zooids and colonies with similar reproductive stage, but a high correlation (r = 0.84) between colonial fecundity and number of zooids per colony was found. Ascidian colonies prior to larvae release stage were placed in 10-liter glass aquaria. The experiments were carried out on September and November, 2000. Water temperature ranged between 23 and 30 ºC. The biggest larval release took place between 10:00 and 14:00 h. Average total length (TL) of larvae leaving the parental zooid was 2.7 mm. The larvae planktonic stage lasted 4 to 8 hours, attaining 3.1 mm (TL). Metamorphosis and larvae settlement lasted 8 to 12 hrs, and exogenous feeding began at 19 hrs. The juvenile zooid measured between 1.3 and 2.05 mm, and 9 % of the larvae completed the metamorphosis.

Effects of Temperature Stress on Pre-imaginal Development and Adult Ptero-fitness of the Vector Mosquito, Culex quinquefasciatus (Diptera: Culicidae)

Day-old first instar larvae of Culex quinquefasciatus mosquitoes were cultured to imago eclosion, at constant temperatures of 30.00, 32.00, 34.00°C and ambient water temperature (28.00±0.02°C, Control). The duration and survivorship of larval and pupal life stages were monitored daily. The wings of adult mosquitoes were measured for length and fluctuating asymmetry. The results indicated significant (p<0.05) effects of water temperature on developmental indices investigated. The duration of larval and pupal stage was significantly shortened from 10.82±1.02 days (28.00±0.02°C) to 7.65±2.15 days (34.00°C) and 2.04±0.70 (28.00±0.02°C) to 1.19±0.27 days (34.00°C), respectively. Survivorship of immature stages showed inverse relationship with increasing water temperature; with survivorship of the pupae significantly higher than those of the larvae at all the temperatures tested. Wing length and fluctuating asymmetry were also affected by rise in temperature. The findings of this study indicate limited thermal adaptation of Cx. quinquefasciatus to relatively warm areas; this information should help in developing effective environmental mosquito-vector control against the species by the discouragement of ecological settings that may reduce micro-climatic temperatures around breeding habitats of the mosquito species.

Immature stages of Spodoptera cosmioides (Lepidoptera: Noctuidae): developmental parameters and host plants

The goal of this study was to detail the temporal and morphological parameters of the immature stages of Spodoptera cosmioides (Walker, 1858) and to gather information about their larval host plants. Larvae were reared on artificial diet and under controlled conditions (25 ± 1°C, 70 ± 10% RH and 14 hour photophase). The viability of eggs, larvae (pre-pupae period inclusive) and pupae were 98.97, 97.33, 97.95 and 94.76%, respectively. The average duration of egg, larval, pre-pupal and pupal stages was 3.82, 19.24, 3.20 and 14.81 days, respectively. A small proportion of females (9.48%) passed through seven instars, and female development was significantly slower than male development. The female larvae that developed through six and seven instars exhibited a mean growth rate of 1.63 and 1.49, respectively. Overall, female pupae were significantly larger, exhibiting slower development than males. One hundred and twenty six plants belonging to 40 families are listed as hosts of S. cosmioides , mainly including Solanaceae, Fabaceae, Asteraceae and Poaceae.

Hierarchical analysis of the population genetic structure in Concholepas concholepas, a marine mollusk with a long‐lived dispersive larva

AbstractFor most marine invertebrate species, dispersal is achieved mainly or exclusively by pelagic larvae. When the duration of the pelagic larval stage is long, genetic homogeneity over large geographic scales is expected. However, genetic structure has often been reported over small spatial scales, suggesting that more complex processes occur than a simple positive relationship between pelagic larval duration and gene flow. Concholepas concholepas has a larval stage that can last up to 3 months in the water column with a wide distributional range covering from 6°S to 56°S. We used a hierarchical sampling technique to test if the genetic homogeneity of this highly dispersive species is maintained throughout its total geographic range in spite of environmental heterogeneity. In the three studied regions (Antofagasta Bay, Valdivia and Patagonia), a spatial pattern of isolation by distance in conjunction with a spatial genetic structure was observed. Within each region, different spatial genetic patterns were detected. In Antofagasta Bay and Valdivia there was evidence of substantial gene flow among populations, whereas in Patagonia, populations showed genetic structure and a unique, genetically isolated location was identified. These results revealed the existence of spatial differences in the genetic patterns among regions with different coastal topographies in C. concholepas, and give us new insights into the inter‐relationships of larval dispersal potential, actual larval dispersal and physical processes. Regarding the sustainable management of C. concholepas, two important issues are derived from this study: (i) to highlight the need for a regional context in the management of C. concholepas, (ii) to determine the distinctiveness of the most austral population and to focus on the conservation efforts due to the relevance of this area.

Biological Studies of Earias insulana (Boisd.) Field Strains at Different Constant Temperature Degrees

Earia insulana (Boisd.) (Lepidoptera: Noctuidae) larvae and/or pupae (cocoons) were collected from five different cotton varieties (Giza 45, Giza 86, Giza 87, Giza 88, and Giza 92) have been grown in Sakha, Kafr El-Sheikh-Governorate at the end of cotton season 2014. Some biological aspects of these populations were investigated under laboratory conditions at three constant temperatures (25, 27 and 30˚C). The present results concluded that, the tested temperatures had main effect on stages durations, survival, adult emergence percentages, sex ratio, and fecundity of field SBW strain. Regardless the variety of cotton general trend of results indicated that, the highest, moderate and lowest percentage of emerged moths were recorded at 25oC, 30oC and 27oC, respectively. In addition, sex ratio were almost 1:1 but tend to females at 25oC while in reverse to male at 30oC. At 27oC sex ratio was 2♀: 1♂. Moreover, the fecundity of developed female from tested varieties recorded its highest values at 25oC and sharply decreased at 27oC. While, at 30oC, the emerged female lost its fecundity except females of Giza 45 deposited 169.0 eggs / female. Furthermore, the tested temperature may be reliable for one developed stage of spiny bollworm and not reliable for another of same population. Also, cotton variety had highly significant effect on the studied biological aspects on its pest SBW, as well as, the interaction between cotton variety and temperature. Regardless temperature, duration of larval stage was 29 & 25.0 days on cotton varieties Giza 45 and Giza 87 at 25oC, respectively. Although, the respective duration of generation in both cases acquire 50 days and 39.1 days, the reproductive capacity of SBW of Giza 45 equal ten times of that when fed on Giza 87. In addition, the larval mortality was higher in population of Giza 87. Depending on the aforementioned conclusion, cotton variety Giza 45 is more susceptible to SBW infestation. The authors arranged the susceptibility of tested cotton varieties to SBW infestation in descending order as follow: Giza 45, Giza 88, Giza 87, Giza 92 and Giza 86. These composite relations need to further vision to study the insect ecology, biology, physiology and economic damage. However, the use of less susceptible cultivars can be considered as a part of IPM control program.

Study of some biological aspects of the blowfly Chrysomya albiceps (Wiedemann 1819) (Diptera: Calliphoridae) in Jeddah, Saudi Arabia

We reared Chrysomya albiceps (Wiedemann 1819) unadult stages (first larval instar, second larval instar, third larval instar and pupal stage) under four constant temperatures. Results proved that increasing temperature from 20 to 25, 30 and 35°C reduced total larval stage duration (9–6, 4.83 and 4.75days, respectively) and pupal duration (7, 5.5, 4 and 1.5days, respectively). C. albiceps larvae at first instar reached adult stage in the longest time at 20°C (16days), and in the shortest time at 35°C (6.25days). The accumulation degree-day (ADD) at 20, 25, 30, 35°C for first larval instar were 8.86, 13.86, 18.86, 23.86 DD, for second larval instar were 10.5, 12, 17, 22 DD and for third larval instar were 35.88, 42.08, 43.97, 56.43 DD. Heat requirements for larval stage at different temperatures; 20, 25, 30 and 35°C (49.68, 63.12, 75.01 and 97.47 DD) were more than the pupal requirements at the same temperatures (39.78, 58.76, 62.73 and 31.02 DD). Total heat requirements for C. albiceps to develop from the first larval instar to adult eclosion were the lowest at 20°C (89.46 DD) and the highest at 30°C (129.138 DD). Decreasing of temperature increased larval body length at the same age. The development curves for C. albiceps were established at four constant temperatures using larval length and the time since egg hatching.

Identifying the key biophysical drivers, connectivity outcomes, and metapopulation consequences of larval dispersal in the sea.

BackgroundPopulation connectivity, which is essential for the persistence of benthic marine metapopulations, depends on how life history traits and the environment interact to influence larval production, dispersal and survival. Although we have made significant advances in our understanding of the spatial and temporal dynamics of these individual processes, developing an approach that integrates the entire population connectivity process from reproduction, through dispersal, and to the recruitment of individuals has been difficult.We present a population connectivity modelling framework and diagnostic approach for quantifying the impact of i) life histories, ii) demographics, iii) larval dispersal, and iv) the physical seascape, on the structure of connectivity and metapopulation dynamics. We illustrate this approach using the subtidal rocky reef ecosystem of Port Phillip Bay, were we provide a broadly-applicable framework of population connectivity and quantitative methodology for evaluating the relative importance of individual factors in determining local and system outcomes.ResultsThe spatial characteristics of marine population connectivity are primarily influenced by larval mortality, the duration of the pelagic larval stage, and the settlement competency characteristics, with significant variability imposed by the geographic setting and the timing of larval release. The relative influence and the direction and strength of the main effects were strongly consistent among 10 connectivity-based metrics.ConclusionsThese important intrinsic factors (mortality, length of the pelagic larval stage, and the extent of the precompetency window) and the spatial and temporal variability represent key research priorities for advancing our understanding of the connectivity process and metapopulation outcomes.Electronic supplementary materialThe online version of this article (doi:10.1186/s40462-015-0045-6) contains supplementary material, which is available to authorized users.

Bionomy of two flies of sanitary and forensic importance: Peckia (Sarcodexia) lambens (Wiedemann) and Oxysarcodexia amorosa (Schiner) (Diptera, Sarcophagidae)

This study aims to elucidate the bionomy of Peckia (Sarcodexia) lambens and Oxysarcodexia amorosa to provide data for medical, veterinary and forensic entomology analyses. We analyzed larval stage duration (L1–L3), weight of the mature larvae (L3), pupal stage duration, L1–adult duration, adult emergence and viability of larvae and adults of both species. Larval viability of P. (S.) lambens was 82% and the mean duration of the larval stage was 3.51±0.99 days. The mature larvae had a mean weight of 33.67±7.13mg. The mean duration of the pupal stage was 8.26±0.93 days and the mean duration of the L1–adult was 11.53±1.22 days. Mean lifespan for females and males was 39.33±1.52 and 57.33±4.72 days, respectively. Larval viability of O. amorosa was 76% and mean duration of larval stage was 3.51±0.64 days. Mature larvae had a mean weight of 28.28±3.38mg. Mean duration of the pupal stage was 10.14±0.63 days and mean duration of the L1–adult was 13.60±0.69 days. Mean lifespan for females and males was 83.66±15.94 and 84.00±19.97 days, respectively. Oxysarcodexia amorosa showed a L1–adult stage longer than P. (S.) lambens; however both species showed low viability. O. amorosa laid more larvae than P. (S.) lambens, this fact may occur because O. amorosa had longer life duration.

Ectopic expression of ecdysone oxidase impairs tissue degeneration in Bombyx mori.

Metamorphosis in insects includes a series of programmed tissue histolysis and remolding processes that are controlled by two major classes of hormones, juvenile hormones and ecdysteroids. Precise pulses of ecdysteroids (the most active ecdysteroid is 20-hydroxyecdysone, 20E), are regulated by both biosynthesis and metabolism. In this study, we show that ecdysone oxidase (EO), a 20E inactivation enzyme, expresses predominantly in the midgut during the early pupal stage in the lepidopteran model insect, Bombyx mori. Depletion of BmEO using the transgenic CRISPR/Cas9 (clustered regularly interspaced short palindromic repeats/RNA-guided Cas9 nucleases) system extended the duration of the final instar larval stage. Ubiquitous transgenic overexpression of BmEO using the Gal4/UAS system induced lethality during the larval-pupal transition. When BmEO was specifically overexpressed in the middle silk gland (MSG), degeneration of MSG at the onset of metamorphosis was blocked. Transmission electron microscope and LysoTracker analyses showed that the autophagy pathway in MSG is inhibited by BmEO ectopic expression. Furthermore, RNA-seq analysis revealed that the genes involved in autophagic cell death and the mTOR signal pathway are affected by overexpression of BmEO. Taken together, BmEO functional studies reported here provide insights into ecdysone regulation of tissue degeneration during metamorphosis.

Extratos aquosos de inhame (Dioscorea rotundataPoirr.) e de mastruz (Chenopodium ambrosioides L.) no desenvolvimento da lagarta-do-cartucho-do-milho Spodoptera frugiperda (J.E. Smith, 1797)

RESUMO:Estudou-se o efeito de extratos aquosos de inhame (0; 5; 10; e 20% p/p) e de mastruz (0; 2; 4; 6; 8 e 10% p/p) na biologia da lagarta-do-cartucho. Secções de folhas de milho foram mergulhadas por 30 segundos em soluções de cada concentração; após a secagem, colocou-se em cada secção uma lagarta recém-eclodida. Foram avaliadas a viabilidade e a duração das fases larval e pupal, peso e comprimento das lagartas e pupas. Em relação ao extrato de inhame, a concentração de 20% causou maior influência na fase larval, sendo a viabilidade reduzida para 12%, com duração de 7 dias, diferindo da testemunha com 17 dias. O extrato da mesma planta a 10% causou 48% de mortalidade. Em todas as concentrações esse extrato também afetou a fase de pupa; na testemunha, 85% das pupas foram viáveis, enquanto nos demais tratamentos a viabilidade não excedeu a 25%. Para o peso e comprimento das lagartas, os resultados não foram significativos. Para o mastruz, o extrato a 20% causou influência na fase larval com baixa viabilidade e mortalidade logo nos primeiros seis dias de avaliação. Outras concentrações de mastruz não deferiram entre si nas fases larval e pupal. Verificou-se que a alimentação das lagartas com folhas tratadas com mastruz diminuiu o peso das pupas.

Larval and juvenile growth of chub mackerel Scomber japonicus in relation to recruitment in the western North Pacific

To detect indices of recruitment intensity of the Pacific stock of chub mackerel Scomber japonicus, the relationship between the growth rate during early life and recruitment variability and the effects of temperature on annual change of the growth rate were examined. Growth-trajectories in larval and juvenile stages were back-calculated by otolith microstructure analysis using juveniles collected in the Kuroshio–Oyashio transition region of the western North Pacific in May and June from 2002 to 2011. A total of 532 otoliths were analysed. Hatch dates were distributed from mid-March to mid-May and most chub mackerel hatched in April. Mean daily growth rates ± standard deviation (SD) of the April cohort in larval and juvenile stages ranged between 1.03 ±0.10 (2006) and 1.52 ±0.23 mm day−1 (2009). The mean daily growth rate and larval stage duration were significantly related to recruitment which had been estimated by virtual population analysis. The results indicated the growth rate of the April cohort was an important index of year-class strength. There was a significant correlation between sea surface temperature experienced by each fish and the mean daily growth rate during the larval period. Higher water temperature led to faster growth and shorter larval stage duration of the April cohort of the Pacific stock of chub mackerel.

Combining the sterile insect technique with the incompatible insect technique: I-impact of wolbachia infection on the fitness of triple- and double-infected strains of Aedes albopictus.

The mosquito species Aedes albopictus is a major vector of the human diseases dengue and chikungunya. Due to the lack of efficient and sustainable methods to control this mosquito species, there is an increasing interest in developing and applying the sterile insect technique (SIT) and the incompatible insect technique (IIT), separately or in combination, as population suppression approaches. Ae. albopictus is naturally double-infected with two Wolbachia strains, wAlbA and wAlbB. A new triple Wolbachia-infected strain (i.e., a strain infected with wAlbA, wAlbB, and wPip), known as HC and expressing strong cytoplasmic incompatibility (CI) in appropriate matings, was recently developed. In the present study, we compared several fitness traits of three Ae. albopictus strains (triple-infected, double-infected and uninfected), all of which were of the same genetic background (“Guangzhou City, China”) and were reared under the same conditions. Investigation of egg-hatching rate, survival of pupae and adults, sex ratio, duration of larval stages (development time from L1 to pupation), time to emergence (development time from L1 to adult emergence), wing length, female fecundity and adult longevity indicated that the presence of Wolbachia had only a minimal effect on host fitness. Based on this evidence, the HC strain is currently under consideration for mass rearing and application in a combined SIT-IIT strategy to control natural populations of Ae. albopictus in mainland China.

Different diets affecting biology and digestive physiology of the Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae)

The Khapra beetle, Trogoderma granarium Everts (Coleoptera: Dermestidae), is a serious pest of grain and other stored products through the world. In this research, effect of five host diets including barley, rice, rye, wheat and walnut was studied on some of biological traits, nutritional indices and digestive enzymatic activity of T. granarium at 33 ± 1 °C, 65 ± 5% RH and a photoperiod of 14:10 (L:D) h. The Khapra beetle larvae reared on walnut had the highest number of larval instar and longest duration of larval and pupal stages (91.30 ± 0.4 days). The heaviest pupal weight of T. granarium was on rye (4.22 ± 0.01 mg) and the lightest weight was on rice (3.99 ± 0.01 mg) and walnut (4.00 ± 0.01 mg). The highest realized fecundity and fertility were recorded for the females reared on rye (45.88 ± 1.08 eggs/female and 69.39 ± 0.68%, respectively) and wheat (49.02 ± 1.55 eggs/female and 67.54 ± 0.69%, respectively), and the lowest ones were observed for the females came from larvae fed walnut (15.45 ± 0.71 eggs/female and 34.55 ± 0.82%, respectively). Also, the results showed that T. granarium larvae reared on walnut had the lowest values of the efficiency of conversion of ingested food (7.67 ± 0.04%) and relative growth rate (0.044 ± 0.0002 mg/mg/day). The lowest midgut amylolytic (0.044 ± 0.0005 and 0.047 ± 0.0005mU/individual, respectively) and proteolytic (0.015 ± 0.0004 and 0.016 ± 0.0001mU/individual, respectively) activity of the sixth instar was detected on walnut and rice. The highest inhibition of amylase (53.37 ± 0.75%) and protease activity (48.54 ± 0.96%) was estimated by incubating midgut extracts from the last instars with wheat and barley proteinaceous extracts, respectively. The results indicated that walnut was the most unsuitable diet for feeding and development of T. granarium.

Lack of fitness costs and inheritance of resistance to Bacillus thuringiensis Cry1Ac toxin in a near-isogenic strain of Plutella xylostella (Lepidoptera: Plutellidae).

Resistance to Bacillus thuringiensis (Bt) formulations in insects may be associated with fitness costs. A lack of costs enables resistance alleles to persist, which may contribute to the rapid development and spread of resistance in populations. To assess the fitness costs associated with Bt Cry1Ac resistance in Plutella xylostella, life tables were constructed for a near-isogenic resistant strain (NIL-R) and a susceptible strain in this study. No fitness costs associated with Cry1Ac resistance in NIL-R were detected, based on the duration of egg and larval stages, the survival of eggs and larvae, adult longevity, fecundity, net reproductive rate, gross reproduction rate, finite rate of increase and mean generation time. Based on log dose-probit lines, resistance in NIL-R is incompletely recessive and results from a single, autosomal, recessive locus; the degree of dominance was estimated to be -0.74 and -0.71 for F1 (resistant ♀ × susceptible ♂) and F1 ' (susceptible ♀ × resistant ♂) progeny respectively. Assessment of near-isogenic Cry1Ac-resistant and Cry1Ac-susceptible strains of P. xylostella indicated that resistance is not accompanied with fitness costs, and that resistance is incompletely recessive. These findings should be useful in managing the development of Bt Cry1Ac resistance.