Affect Insect Development Research Articles

Current status of innate immune responses in Malpighian tubules of insects: A review focusing on the Toll signaling pathway

AbstractInnate immunity is the immediate and exclusive defense mechanism in invertebrates. It acts against foreign agents and pathogens. In insects, this defense mechanism involves a combination of humoral and cellular responses, orchestrated by specific recognition receptors and the activation of various signaling pathways. Remarkably, Toll and Toll‐related proteins play a pivotal role in insect immunity by inducing the production of antimicrobial peptides (AMPs) in response to pathogen attacks. Toll receptors, which are type I transmembrane proteins, significantly affect insect development and the innate immune response, primarily via the nuclear factor kappa‐B signaling pathway. The Malpighian tubules of insects play a crucial role in waste elimination, hemostasis maintenance, and immune defense. The Toll signaling pathway in Malpighian tubules is mainly involved in the production of AMPs. This review provides valuable insights into the mechanisms of the Toll signaling pathway and the morphological and physiological attributes of Malpighian tubules. Moreover, it discusses the classification and functionalities of AMPs synthesized in Malpighian tubules in response to pathogens, thereby contributing to our understanding of innate immunity in insects.

The Effects of Temperature on the Development and Survival of Bathycoelia distincta (Hemiptera: Pentatomidae), a Significant Pest of Macadamia in South Africa.

Temperature is the most influential condition affecting insect development and population dynamics. Understanding its impact and other important factors, such as diet, could provide fine-scale predictions of species abundance and distribution in space and time. The two-spotted stink bug, Bathycoelia distincta Distant (Hemiptera: Pentatomidae), is a significant pest of macadamia in South Africa for which limited information on developmental biology exists. Here, for the first time, variations in key developmental parameters of the B. distincta biology were studied systematically. The developmental duration, survival rate, development rate, lower developmental threshold (Tmin), optimum developmental threshold (Topt), upper developmental threshold (Tmax), and thermal constant were quantified for each developmental stage of B. distincta. In addition, the effect of diet (macadamia nut and sweetcorn) on the developmental duration and survival rate were quantified. This study was conducted at five constant temperatures (18, 21, 22, 25, and 29 °C) with relative humidity (RH) variations. The developmental duration from egg to adult decreased significantly with increased temperature: 21 °C (±60 days) to 29 °C (±32 days). The survival rate was significantly different for instar 2 between temperatures. Nymphs (instars 2 and 4) developed faster on the sweetcorn diet than on a macadamia diet, but the total developmental time did not differ significantly between the diets. Development from egg to adult required 783 degree days (DD), with a Tmin of 13.5 °C, Topt of 29.5 °C, and Tmax of 38 °C. Ongoing global warming will increase the population growth of B. distincta through increased development rate, resulting in more damage to macadamia nuts. Understanding the developmental biology and thresholds for the DD model of B. distincta is fundamental for predicting its phenology and outbreaks in macadamia orchards.

Wolbachia dominance influences the Culex quinquefasciatus microbiota

Microorganisms present in mosquitoes and their interactions are key factors affecting insect development. Among them, Wolbachia is closely associated with the host and affects several fitness parameters. In this study, the bacterial and fungal microbiota from two laboratory Culex quinquefasciatus isolines (wild type and tetracycline-cured) were characterized by metagenome amplicon sequencing of the ITS2 and 16S rRNA genes at different developmental stages and feeding conditions. We identified 572 bacterial and 61 fungal OTUs. Both isolines presented variable bacterial communities and different trends in the distribution of diversity among the groups. The lowest bacterial richness was detected in sugar-fed adults of the cured isoline, whereas fungal richness was highly reduced in blood-fed mosquitoes. Beta diversity analysis indicated that isolines are an important factor in the differentiation of mosquito bacterial communities. Considering composition, Penicillium was the dominant fungal genus, whereas Wolbachia dominance was inversely related to that of Enterobacteria (mainly Thorsellia and Serratia). This study provides a more complete overview of the mosquito microbiome, emphasizing specific highly abundant components that should be considered in microorganism manipulation approaches to control vector-borne diseases.

Identification of chitinase genes and roles in the larval-pupal transition of Leptinotarsa decemlineata.

Insect chitinases play crucial roles in degrading chitin in the extracellular matrix, affecting insect development and molting. However, our understanding of the specific functions of various chitinases in Leptinotarsa decemlineata is limited, hindering the deployment of novel gene-targeting technologies as pest management strategies. We identified and characterized 19 full-length complementary DNA (cDNA) sequences of chitinase genes (LdChts) in Leptinotarsa decemlineata. Despite having varying domain architectures, all these chitinases contained at least one chitinase catalytic domain. Phylogenetic analysis classified the chitinase proteins into ten distinct clusters (groups I-X). Expression profiles showed the highest expression in chitin-rich tissues or during specific developmental stages from the larva-to-pupa transition. Gene-specific RNA interference (RNAi) experiments provided valuable insight into chitinase gene function. Silencing of group II LdCht10 prevented larval-larval molting, larval-prepupal, and prepupal-pupal processes. Moreover, our study revealed that LdCht5, LdCht2, LdCht11, LdCht1, and LdCht3 from groups I and VII-X were specifically essential for the transition from prepupal to pupal stage, whereas LdIDGF2 from group V was necessary for the larval-prepupal metamorphic process. The chitinase gene LdCht7 from group III and LdIDGF4 from group V were involved in both the larva-to-prepupa and the prepupa-to-pupa shift. Additionally, our findings also shed light on the exclusive expression of nine chitinase genes within group IV in the digestive system, suggesting their potential role in regulating larval body weight and larva-to-pupa transition. Our results provide a comprehensive understanding of the functional specialization of chitinase genes during the molting process of various stages and identify potential targets for RNAi-based management of Leptinotarsa decemlineata. © 2023 Society of Chemical Industry.

Defence Responses Associated with Elicitor-Induced, Cultivar-Associated Resistance to Latania Scale in Kiwifruit.

Latania scale insect is a pest of global significance affecting kiwifruit. The sessile insect (life stage: settled crawler—mature adult) is covered with a waxy cap that protects it from topical pesticides, so increasingly, a selection of resistant cultivars and application of elicitors are being used in pest control. Thus far, the application of a salicylic acid (SA) phytohormone pathway elicitor, acibenzolar-S-methyl (ASM), has been shown to reduce insect development (as indicated by cap size) on one kiwifruit cultivar (‘Hayward’). To investigate how cultivar-associated resistance is affected by the ability to respond to different elicitors, we measured phytohormones (by LCMS) and gene expression (by qPCR and NanoString) on latania scale-tolerant ‘Hort16A’ and susceptible ‘Hayward’ kiwifruit over two seasons. Potted plants in the presence/absence of settled latania scales were treated with ASM (0.2 g/L) or methyl jasmonate (MeJA, 0.05% v/v), representing elicitors of the SA and JA signalling pathways, respectively. ‘Hort16A’ cultivar resistance to latania scale was associated with elevated expression of SA and SA-related defence genes (PR1 and two PR2 family genes) in the ASM treatment. MeJA treatments did not significantly affect insect development in ‘Hayward’ (latania scale did not survive on ‘Hort16A’) and did not correlate with phytohormone and gene expression measurements in either cultivar. ‘Hayward’ had greater concentrations than ‘Hort16A’ of inert storage forms of both SA and JA across all treatments. This information contributes to the selection of tolerant cultivars and the effective use of elicitors for control of latania scale in kiwifruit.

Biologically active toxin from macroalgae Chaetomorpha antennina Bory, against the lepidopteran Spodoptera litura Fab. and evaluation of toxicity to earthworm, Eudrilus eugeniae Kinb

BackgroundSeaweeds harbour a wide array of bioactive compounds shown to be effective in support of sustainable agricultural practices. The green seaweed Chaetomorpha antennina found in abundance in coastal areas of India has been reported with various bioactivities. Owing to the requirement of alternative and economical natural pest control method to be applied in sustainable agronomic strategies, the current study attempts to evaluate the efficacy of chemical toxins from C. antennina, as insecticidal agents, by inspecting their effects on the physiology, biochemistry, immune system, and histology of one of the most important insect pests of agricultural crops in the Asian tropics, the polyphagous lepidopteran Spodoptera litura.ResultsThe active fraction 5 isolated from C. antennina using methanol extraction produced significant mortality rates of S. litura among all the other fractions obtained. GC–MS analysis revealed the presence of various pesticide compounds. The toxin compounds (active fraction 5) were found to negatively influence the pest’s immune system performance at sub-lethal concentrations (LC50 38.73and LC90 53.60 ppm), affecting insect development, reducing the haemocyte count (69.24%) and reduced the activity of major defence enzyme phenoloxidase decreased post-treatments. Digestive phosphatase enzymes, acid phosphatase, ACP, alkaline phosphatase, ALP, and ATPase were demodulated by 37.5, 39, and 23.9% compared with untreated. Increase in detoxification enzymes coupled with mid-gut collapse are indicative of the toxicity of the compounds. Earthworms exposed to seaweed compounds displayed no debarring effects.ConclusionExtracted seaweed compounds produced significant lethal effect on the insect larvae, affecting the immune as well as digestive systems of the pest. However, no such toxicity was observed in earthworms treated with the seaweed fraction supporting their environmentally benign nature. Since the insect immune system is responsible for the development of resurgence against pesticides, suppression of immunological activities by seaweed toxins indicate the long-term applicability of these compounds as prospective pesticides. The results support the potential of chemicals from C. antennina for biopesticide development to manage economically important agricultural pests.

New insights on the effects of spinosad on the development of Helicoverpa armigera

Helicoverpa armigera (cotton bollworm) is one of the most destructive pests worldwide. Due to resistance to Bacillus thuringiensis and conventional insecticides, an effective management strategy to control this pest is urgently needed. Spinosad, a natural pesticide, is considered an alternative; however, the mechanism underlying the developmental effects of sublethal spinosad exposure remains elusive. In this study, the mechanism was examined using an insect model of H. armigera. Results confirmed that exposure to sublethal spinosad led to reduced larval wet weight, delayed larval developmental period, caused difficulty in molting, and deformed pupae. Further investigation demonstrated that exposure to sublethal spinosad caused a significant decrease in 20E titer and increase in JH titer, thereby leading to the discordance between 20E and JH titers, and consequently alteration in the expression levels of HR3 and Kr-h1. These results suggested that sublethal spinosad caused hormonal disorders in larvae, which directly affect insect development. Our study serves as a reference and basis for the toxicity evaluation of spinosad on molting and pupation in insect metamorphosis, which may contribute to identifying targets for effective control of cotton bollworm.

Effect of Different Plants on the Growth and Reproduction of Thrips flavus (Thysanoptera: Thripidae).

Simple SummaryThrips flavus Schrank (Thysanoptera: Thripidae) is a worldwide phytophagous pest in Palearctic Asian and European countries. T. flavus feeds on a wide spectrum of host plants. Thus, understanding its host plant preferences is important for pest control. We tested the development duration, population parameters, and population growth of T. flavus on five species of plants. The intrinsic rate of increase and fecundity was the highest on Cucumis sativus, followed by Glycine max and Capsicum annuum. However, Solanum melongena and Brassica rapa var. glabra were not suitable host plants. These results help to improve our understanding of the population dynamics of T. flavus and should lead to positive measures to control thrips in the field.Host plants play an important role in affecting insect development and reproduction. Understanding the host plant preferences is important for pest control. Thrips flavus Schrank (Thysanoptera: Thripidae) is a worldwide phytophagous pest in Palearctic Asian and European countries. We used a life table analysis to study the development duration, population parameters, and population growth of T. flavus on five plant species, including Solanum melongena (Solanaceae), Capsicum annuum (Solanaceae), Glycine max (Leguminosae), Brassica rapa var. glabra (Cruciferae), and Cucumis sativus (Cucurbitaceae). The results showed that T. flavus can survive and reproduce on Cu. sativus and G. max, which were two potentially suitable host plants. T. flavus preferred to oviposit on Cu. sativus with a shorter duration of development (17.8 days) at 25 °C. Therefore, the host plant was an important factor influencing the development and fecundity of T. flavus populations. These results will improve our understanding of the population dynamics of T. flavus and facilitate the development of more scientific and efficient measures to control thrips.

Resistance of rice genotypes to fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae)

The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important rice pest which consumes leaf area during all phases of plant development. The objective of this study was to identify rice genotypes that provide antixenosis and antibiosis to fall armyworm. Antixenosis was investigated by measuring non-preference in free-choice and no-choice tests while antibiosis was determined by measuring biological parameters and nutritional indices of S. frugiperda in twelve rice genotypes. The genotype Miúdo Branco showed antixenosis to S. frugiperda, whereas the genotypes IR 64 and Bacaba Branco showed antibiosis to S. frugiperda by affecting insect development and prolonging insect life cycle. Insects that fed on Bacaba Branco genotype demonstrated the lowest nutritional indices. Since Miúdo Branco, IR 64 and Bacaba Branco showed moderate resistance, rice producers could use these genotypes as part of a control strategy for S. frugiperda.

Resistance of rice genotypes to fall armyworm Spodoptera frugiperda (Lepidoptera: Noctuidae)

ABSTRACT The fall armyworm, Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae), is an important rice pest which consumes leaf area during all phases of plant development. The objective of this study was to identify rice genotypes that provide antixenosis and antibiosis to fall armyworm. Antixenosis was investigated by measuring non-preference in free-choice and no-choice tests while antibiosis was determined by measuring biological parameters and nutritional indices of S. frugiperda in twelve rice genotypes. The genotype Miudo Branco showed antixenosis to S. frugiperda, whereas the genotypes IR 64 and Bacaba Branco showed antibiosis to S. frugiperda by affecting insect development and prolonging insect life cycle. Insects that fed on Bacaba Branco genotype demonstrated the lowest nutritional indices. Since Miudo Branco, IR 64 and Bacaba Branco showed moderate resistance, rice producers could use these genotypes as part of a control strategy for S. frugiperda.

Prediction of annual generations of the tomato leaf miner Tuta absoluta on tomato cultivations in Egypt

BackgroundTomato crop is the first vegetable crop in Egypt; it covers about 3% of Egypt’s total planted area. The tomato leaf miner Tuta absoluta is a polyphagous insect pest which feeds on several solanaceous plant species and preferentially on tomato causing high losses in productivity. This study aims to predict the annual generations and expected times for moth emergence in order to select the best time for the pest management.MethodsSpecimens of T. absoluta were collected from infested tomato field and reared under controlled temperatures to calculate the thermal requirements for development and completing the whole generation. The duration of different developmental stages of this insect and the life table parameters were estimated. The data were used to calculate the thermal constant and developmental zero for different developmental stages using the formula of Jasic (Bihemoslov 72:383-390, 1975) mathit{mathsf{y}}=mathit{mathsf{n}} left(mathit{mathsf{t}}-mathit{mathsf{x}}right) .ResultsEcological studies were performed to evaluate the adverse effects of climatic changes on insect populations based on accumulation of the thermal requirements for development. The developmental zero was 5.79 °C and the thermal constant was 171 DDs to complete the pupal stage development. Based on these values, the pupae development can be repeated 36 times during 2012 when the mean annual temperature was 22.8 °C. In Giza governorate, the average life cycle duration during 2012 was 52.44 days when the mean annual temperature was 22.8 °C, the number of annual generations was 8.05, and the timing of the first generation was 11.66 days in April 2012 while the 8th generation cycle was obtained after 28.2 days of January 2013. In Qena governorate, the mean annual temperature was increased to be 26.04 °C, so the annual generations increased to 9.52. The first generation was recorded by the end of April 2012 while the 9th generation was completed on 24.4 days of December 2012. In Merssa-Matrouh governorate, the mean annual temperature was 20.53 °C and the number of the annual generations was found to be 7 during 2012. The first generation occurred on the day 19.86 of April 2012 while the 7th generation cycle was detected after 30.98 days of January 2013. This means that there must be successive emergence of the adults but with variations during the different months and locations in correlation with variation of temperatures.ConclusionThe accumulated thermal requirements appeared to be a very critical factor affecting insect development to complete the annual generations of T. absoluta in Egypt. This helps in designing the effective program and the best time for the pest management.

Structural and Functional Characterization of PR-4 SUGARWINs From Sugarcaneand Their Role in Plant Defense.

SUGARWIN1 and 2 are defense proteins from sugarcane. Their gene expression is known to be induced in response to wound and Diatraea saccharalis damage. Although the recombinant SUGARWIN protein does not affect insect development, it promotes significant morphological and physiological changes in Fusarium verticillioides and Colletotrichum falcatum, which lead to fungal cell death via apoptosis. In this study, we deepen our understanding of the role of SUGARWINs in plant defense and the molecular mechanisms by which these proteins affect fungi by elucidating their molecular targets. Our results show that SUGARWINs play an important role in plant defense against opportunistic pathogens. We demonstrated that SUGARWINs are induced by C. falcatum, and the induction of SUGARWINs can vary among sugarcane varieties. The sugarcane variety exhibiting the highest level of SUGARWIN induction exhibited a considerable reduction in C. falcatum infection. Furthermore, SUGARWIN1 exhibited ribonuclease, chitosanase, and chitinase activity, whereas SUGARWIN2 exhibited only chitosanase activity. This variable enzymatic specificity seems to be the result of divergent amino acid composition within the substrate-binding site.

Larval mannitol diets increase mortality, prolong development and decrease adult body sizes in fruit flies (Drosophila melanogaster).

ABSTRACTThe ability of polyols to disrupt holometabolous insect development has not been studied and identifying compounds in food that affect insect development can further our understanding of the pathways that connect growth rate, developmental timing and body size in insects. High-sugar diets prolong development and generate smaller adult body sizes in Drosophila melanogaster. We tested for concentration-dependent effects on development when D. melanogaster larvae are fed mannitol, a polyalcohol sweetener. We also tested for amelioration of developmental effects if introduction to mannitol media is delayed past the third instar, as expected if there is a developmental sensitive-period for mannitol effects. Both male and female larvae had prolonged development and smaller adult body sizes when fed increasing concentrations of mannitol. Mannitol-induced increases in mortality were concentration dependent in 0 M to 0.8 M treatments with mortality effects beginning as early as 48 h post-hatching. Larval survival, pupariation and eclosion times were unaffected in 0.4 M mannitol treatments when larvae were first introduced to mannitol 72 h post-hatching (the beginning of the third instar); 72 h delay of 0.8 M mannitol introduction reduced the adverse mannitol effects. The developmental effects of a larval mannitol diet closely resemble those of high-sugar larval diets.This article has an associated First Person interview with the first author of the paper.

Toxic effect of Canavalia ensiformis seed coat on larval development of Callosobruchus maculatus

The outer-covering of seeds is known as the seed coat, and this is the seed's first protective barrier against the penetration of insects. In this sense, seed coat toxicity can affect insect development. In this work, we study the influence of the Canavalia ensiformis seed coat on embryonic and larval development of Callosobruchus maculatus. Oviposition of C. maculatus was negatively affected by the seed coat, while embryonic development occurred without any morphological or biochemical alterations. During larval development, physiological changes comprising delay in body weight, the inability of larvae to penetrate the C. ensiformis seed coat, and decreases in biochemical parameters, such as contents of glucose, proteins, and triglycerides, were recorded. Although larvae survived until 17 days after oviposition, they could not penetrate the C. ensiformis seed coat. A dose-dependent effect was observed on female oviposition, mass, and survival of larvae of C. maculatus. Cysteine protease, α-amylase and α-glucosidase activities decreased while aspartic protease activity increased with increases in ingestion of seed coat flour. Larval post-embryonic development was affected by C. ensiformis seed and this interference is related with a toxic seed coat which reduced activities of several key digestive enzymes, resulting in severe weight loss.

The retardant effect of 2-Tridecanone, mediated by Cytochrome P450, on the Development of Cotton bollworm, Helicoverpa armigera.

BackgroundPlant allelochemicals act as toxins, inhibitors of digestion, and deterrents that affect the fecundity of insects. These compounds have attracted significant research attention in recent decades, and much is known about the effects of these xenobiotic plant secondary metabolites on insect development. To date, although ecological interactions between xenobiotic plant secondary chemicals that retard insect growth have been observed in many species, it remains unclear how particular allelochemicals influence insect development in a life stage-dependent manner.ResultsWe found that 2-tridecanone can affect insect development; this effect appears similar to the symptoms induced by the physiological imbalance between juvenile and molting hormones in cotton bollworm. We later detected that a decrease in the concentration of 20-hydroxyecdysone occurred alongside the observed symptoms. We next identified the transcriptome of Helicoverpa armigera and eightdigital gene expression libraries for shading light on how 2-tridecanone retarded the development of cotton bollworm. The expression of CYP314A1, CYP315A1, CYP18A1, CYP307A1, and CYP306A1 (unigenes 16487, 15409, 40026, 41217, 35643, 16953, 8199, 13311, and 13036) were found to be induced by 2-tridecanone; these are known to be related to the biosynthesis or metabolism of 20-hydroxyecdysone. Expression analysis and RNA interference studies established that the retardant effect of 2-tridecanone on the development of cotton bollworm is mediated by P450 genes.ConclusionsThe candidate P450 gene approach described and exploited here is useful for identifying potential causal genes for the influence of plant allelochemicals on insect development.Electronic supplementary materialThe online version of this article (doi:10.1186/s12864-016-3277-y) contains supplementary material, which is available to authorized users.

Development and validation of a GC–MS method for nicotine detection in Calliphora vomitoria (L.) (Diptera: Calliphoridae)

Entomotoxicology is the application of toxicological methods and analytical procedures on necrophagous insects feeding on decomposing tissues to detect drugs and other chemical components, and their mechanisms affecting insect development and morphology and modifying the methodology for estimation of minimum time since death. Nicotine is a readily available potent poison. Because of its criminal use, a gas chromatography–mass spectrometry (GC–MS) method for the detection of nicotine in Calliphora vomitoria L. (Diptera: Calliphoridae) was developed and validated. Furthermore, the effect of nicotine on the development, growth rate, and survival of this blowfly was studied. Larvae were reared on liver substrates homogeneously spiked with measured amounts of nicotine (2, 4, and 6ng/mg) based on concentrations that are lethal to humans. The results demonstrated that (a) the GC–MS method can detect both nicotine and its metabolite cotinine in immature C. vomitoria; (b) the presence of nicotine in the aforementioned three concentrations in food substrates did not modify the developmental time of C. vomitoria; (c) during the pupation period, larvae exposed to nicotine died depending on the concentration of nicotine in the substrate; and (d) the resultant lengths of larvae and pupae exposed to 4 and 6ng/mg concentrations of nicotine were significantly shorter than those of the control.

Effect of Over-Tree Evaporative Cooling in Orchards on Microclimate and Accuracy of Insect Model Predictions.

Orchard design and management practices can alter microclimate and, thus, potentially affect insect development. If sufficiently large, these deviations in microclimate can compromise the accuracy of phenology model predictions used in integrated pest management (IPM) programs. Sunburn causes considerable damage in the Pacific Northwest, United States, apple-producing region. Common prevention strategies include the use of fruit surface protectants, evaporative cooling (EC), or both. This study focused on the effect of EC on ambient temperatures and model predictions for four insects (codling moth, Cydia pomonella L.; Lacanobia fruitworm, Lacanobia subjuncta Grote and Robinson; oblique-banded leafroller, Choristoneura rosaceana Harris; and Pandemis leafroller, Pandemis pyrusana Kearfott). Over-tree EC was applied in July and August when daily maximum temperatures were predicted to be ≥30°C between 1200-1700 hours (15/15 min on/off interval) in 2011 and between 1200-1800 hours (15/10 min on/off interval, or continuous on) in 2012. Control plots were sprayed once with kaolin clay in early July. During interval and continuous cooling, over-tree cooling reduced average afternoon temperatures compared with the kaolin treatment by 2.1-3.2°C. Compared with kaolin-treated controls, codling moth and Lacanobia fruitworm egg hatch in EC plots was predicted to occur up to 2 d and 1 d late, respectively. The presence of fourth-instar oblique-banded leafroller and Pandemis leafroller was predicted to occur up to 2 d and 1 d earlier in EC plots, respectively. These differences in model predictions were negligible, suggesting that no adjustments in pest management timing are needed when using EC in high-density apple orchards.

Experimental study of Lucilia sericata (Diptera Calliphoridae) larval development on rat cadavers: Effects of climate and chemical contamination

Household products such as bleach, gasoline or hydrochloric acid have been used to mask the presence of a cadaver or to prevent the colonization of insects. These types of chemicals affect insect development and alter the forensic entomology analysis. This study was designed to test the effects of six household products (bleach, mosquito repellent, perfume, caustic soda, insecticide and unleaded gasoline) on blowfly (Lucilia sericata, Diptera: Calliphoridae) larval development. Furthermore, the effects of climate (rain or dry conditions) on larval development were analyzed. For each replication, 100 first instars were placed on a rat cadaver on which one household product was spilled. We observed a decrease in the survival rates of the larvae but no significant effect on their development times or the adult size. The same trends were observed under rainy conditions. However, the rain altered the effects of some tested household products, especially gasoline. These results demonstrate for the first time the successful development of necrophagous larvae on chemically contaminated cadavers, and provide evidence for the range of possible effects to expect.

Destruction of peritrophic membrane and its effect on biological characteristics and activity of digestive enzymes in larvae of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae)

The mid gut in insects is usually lined with a peritrophic membrane (PM), which protects it from microbial infections and physical contact with ingested food. Calcofluor is an optical brightener that has strong chitin-binding properties, which disrupt the chitin-protein structure of PM. In this study, we investigated the effects of calcofluor on the structure of the PM, activity of some common digestive enzymes and biological characteristics of the Indian meal moth, Plodia interpunctella (Lepidoptera: Pyralidae). Twenty hours after feeding on a calcofluor-containing diet, the PM was completely eliminated. We recorded significant effects of calcofluor on the activity of digestive enzymes in the mid and hindguts of larvae. In both these regions of the gut, in particular, there were significant increases in the activity of α-amylase, α-galactosidase and trypsin. The activities of α-glucosidase and β-glucosidase in the midgut of treated larvae were lower than in the control, but were significantly higher in the hindgut of treated larvae. The larvae that fed on on calcofluor for 20 h, took longer to complete their larval and pupal stages, were lighter in weight and fewer reached maturity and laid fewer eggs. Results of this and previous studies highlight the crucial role of PM in enzyme recycling and digestion. PM disruption may negatively affect insect development on the one hand, by decreasing the efficiency of food digestion and, on the other, by increasing the costs associated with an increased enzyme demand and disrupted enzyme recycling mechanism.

Comparison of the effects of cereal and legume proteinaceous seed extracts on α-amylase activity and development of the Sunn pest

The Sunn pest, Eurygaster integriceps Puton (Hemiptera: Scutelleridae), is a significant limiting factor in the production of wheat and barley in many areas of the world. In the current study, the effect of semi-purified proteinaceous extracts of seeds on digestive enzymes, and the growth and development of the Sunn pest were studied. The results showed that the purified α-amylase inhibitor from Triticum aestivum (type І) and rice semi-purified seed extract did not significantly affect the Sunn pest α-amylase activity. However, bean and cowpea seed extracts significantly affected α-amylase activity in vitro. For example, the bean seed extract at concentrations of 0.125 and 2.0mg·mL−1 inhibited α-amylase activity of the pest by 15% and 45%, respectively, while the cowpea seed extract, at the same concentrations, inhibited α-amylase activity of the pest by 9% and 40%, respectively. Further, incorporation of the seed extracts into the insect diet showed that the rice seed extract did not affect insect development time, while bean and cowpea seed extracts at high concentrations (e.g., 3.0%) significantly affected nymphal development time and survivability (P>0.05). These results show that semi-purified seed extracts affect α-amylase activity, developmental time, and survivability but not the adult weight of the Sunn pest.