Insect Fecundity Research Articles

Evaluation of different diets for dsRNA-based gene silencing assays in brinjal shoot and fruit borer, <i>Leucinodes orbonalis</i>

The shoot and fruit borer of eggplant, Leucinodes orbonalis, is known to cause huge crop losses and reduce the marketability of the produce. In the current scenario of increased insecticide resistance in pests and concern for ecological sustainability, pest management using target-specific biomolecules such as double-stranded RNA (dsRNA) can be an efficient strategy. To conduct the preliminary lab studies using dsRNA, a diet used for bioassays is crucial as it should support insect growth and development while efficiently delivering the test material. The present study evaluated Artificial Diet (AD) and Potato Diet (PD) through a life table study. The stability of the dsRNA in the diets was assessed at 6, 12 and 24 h post mixing with the diets. The insect survival (62.6%), fecundity (65.48±3.15), sex ratio (1.3:1), and developmental parameters like net reproductive rate were found to be better for PD-reared individuals in comparison to AD-reared insects. The dsRNA was found to be stable for 24 h in AD, while it degraded at 12 h post mixing in PD. Therefore, the AD diet can be used for dsRNA oral feeding and can be replaced with a new diet at every 24 h, and for further rearing after dsRNA feeding, the PD can be used.

Physical and biochemical characteristics of cereal grains affect population growth parameters of Sitophilus oryzae (L.) (Coleoptera: Curculionidae)

The rice weevil, Sitophilus oryzae L. (Coleoptera: Curculionidae), is a significant pest of rice and other cereal grains. In this research, the effects of various grain species, including barley, maize, millet, rice, sorghum, and wheat, were assessed on biological properties and life history variables of S. oryzae under laboratory conditions. Data were analyzed based on the age-stage, two-sex life table method. Furthermore, various physicochemical properties of cereal grains, including protein content, starch content, humidity content, and seed hardness, were investigated to explore their correlation with the studied parameters of S. oryzae. The longest development time was observed on millet and sorghum hosts, while the shortest was on maize seed. The beetles reared on rice and millet species showed the maximum fecundity, whereas those reared on sorghum and millet grains showed the lowest. Maize grain had the highest intrinsic rate of increase (r), whereas millet and sorghum grains had the lowest. According to the correlation analysis, overall, seed protein content was negatively correlated with insect fecundity, R0 and r, but positively correlated with development time. Furthermore, starch content was positively correlated with insect fecundity, R0 and r, and negatively correlated with development time. The cluster results demonstrated that whereas sorghum and millet were comparatively resistant hosts for the growth of S. oryzae, maize and rice were relatively susceptible seeds. This information can be helpful in the development or improvement of integrated pest management (IPM) strategies against rice weevil. The findings of this research will also be helpful in introducing unsuitable hosts for the development of transgenic grains resistant to S. oryzae. The pest-resistant cereal grains identified in this study can potentially be utilized in combination with other pest control strategies for sustainable management of S. oryzae, which may help reduce the excessive use of chemical insecticides.

Effect of Guanylate Cyclase-22-like on Ovarian Development of Orius nagaii (Hemiptera: Anthocoridae).

This study identified and characterized the gene encoding recep tor-type guanylate cyclase-22-like (GCY-22; OnGCY) from the pirate bug Orius nagaii, an important biological control agent. The full-length cDNA of the GCY of O. nagaii was obtained by rapid amplification of cDNA ends (RACE); it had a total length of 4888 base pairs (bp), of which the open reading frame (ORF) was 3750 bp, encoding a polypeptide of 1249 amino acid residues. The physicochemical properties of OnGCY were predicted and analyzed by using relevant ExPASy software, revealing a molecular formula of C6502H10122N1698O1869S57, molecular weight of ~143,811.57 kDa, isoelectric point of 6.55, and fat index of 90.04. The resulting protein was also shown to have a signal peptide, two transmembrane regions, and a conserved tyrosine kinase (tyrkc). Silencing OnGCY by RNA interference significantly inhibited ovarian development and decreased fertility in female O. nagaii in the treated versus the control group. Additionally, OnGCY silencing significantly decreased the expression levels of other GCY and Vg genes. Thus, these results clarify the structure and biological function of OnGCY, which has an important role in insect fecundity. The results also provide a reference for agricultural pest control and future large-scale breeding of biological control agents.

Study of the Biology of the Cochineal Scale Insect, Dactylopius opuntiae

Alhousa, W., A.N. Basheer and Z. El-Naser. 2024. Study of the Biology of the Cochineal Scale Insect, Dactylopius opuntiae. Arab Journal of Plant Protection, 42(2): 143-148. https://doi.org/10.22268/AJPP-001240 Prickly pear cochineal Dactylopius opuntiae (Cockerell) is one of the most important pests of prickly pear Opuntia ficus-indica in different regions of the world. This study was conducted with the aim of investigating the biology of the insect on the Indian prickly pear plant. The work was carried out during the 2021 season, using a random design. Samples were collected from Qatana, Syria, and the biology of the insect was studied within a rearing room under controlled conditions (temperature 25±1°C, relative humidity 45±10%). The incubation period was evaluated in a cohort of 100 eggs and the life cycle was described from a cohort of 150 individuals. Individual females were used as experimental unit (n=40 females) to determine insect fecundity. The average egg laying period was 20.76±0.77 minutes, and the average period of the first nymph was 12.66±0.53 days in females, and 14.03±0.62 days in males, and the second nymph was 25.16±2.42 days for females, and 8.72±1.67 days for males. The average period for pre-pupal and pupal stage of males was 12.9±1.63 days, and the average period of one generation from egg laying until the appearance of the adult insect was 85.85±2.09 days for females, and 56.68±0.98 days for males. Average Fertility was 226.75 eggs/female, with daily egg laying average of 17.9±0.63 eggs/female. The maximum daily fertility average was 16.6±0.35 eggs, and the average hatching rate was 87.86±3.92%. Whereas, the average egg mortality rate ranged between 21.05 and 22.05% in the reptilian stage. Keywords: Biology, prickly pear, egg incubation, nymph, fertility.

Effect of four chitinase genes on the female fecundity in Sogatella furcifera (Horváth).

The white-backed planthopper (WPH), Sogatella furcifera (Horváth), is a destructive rice pest with strong reproductive capacity. To gain insights into the roles of chitinases in the reproductive process of this insect species, this study represents the first-ever endeavor to conduct an in-depth exploration into the reproductive functions of four chitinase genes. In this study, it was observed that four chitinase genes were expressed in female adults, with a relatively high expression level in the ovaries. SfCht2 and SfIDGF1 were highly expressed during later ovarian development. while SfENGase increased and then decreased with ovarian development. SfCht2, SfCht6-2 and SfENGase were highly expressed in fat body on the first and second days after eclosion, whereas SfIDGF1 highest on day 7. Compared with control group, Silencing four chitinase genes inhibited ovarian development and significantly shortened the oviposition period of S. furcifera, reducing egg-laying capacity but not affecting egg hatching. The detection demonstrated that the expression levels of SfVg, SfVgR and 70-90% juvenile hormone (JH) signaling pathway-related reproductive genes was significantly down-regulated. Moreover, SfCht6-2 and SfENGase significantly affected the expression levels of Target of Rapamycin (TOR) signaling pathway genes. SfENGase had the ability to impact nutrient signaling pathways and fatty acid metabolism, repressing vitellogenin synthesis and ultimately influencing ovarian development of S. furcifera. Overall, this study provides insight into the function of chitinases in insect fecundity and is of great significance for enriching the cognition of insect chitinase function. They will become the suitable target genes for controlling the most destructive rice planthoppers. © 2023 Society of Chemical Industry.

Juvenile hormone induces reproduction via miR-1175-3p in the red imported fire ant, Solenopsis invicta.

Juvenile hormone (JH) acts in the regulation of caste differentiation between queens and workers (i.e., with or without reproductive capacity) during vitellin synthesis and oogenesis in social insects. However, the regulatory mechanisms have not yet been elucidated. Here, we identified a highly expressed microRNA (miRNA), miR-1175-3p, in the red imported fire ant, Solenopsis invicta. We found that miR-1175-3p is prominently present in the fat bodies and ovaries of workers. Furthermore, miR-1175-3p interacts with its target gene, broad-complex core (Br-C), in the fat bodies. By utilizing miR-1175-3p agomir, we successfully suppressed the expression of the Br-C protein in queens, resulting in reduced vitellogenin expression, fewer eggs, and poorly developed ovaries. Conversely, decreasing miR-1175-3p levels led to the increased expression of Br-C and vitellogenin in workers, triggering the "re-development" of the ovaries. Moreover, when queens were fed with JH, the expression of miR-1175-3p decreased, whereas the expression of vitellogenin-2 and vitellogenin-3 increased. Notably, the suppression of fertility in queens caused by treatment with agomir miR-1175-3p was completely rescued by the increased vitellogenin expression induced by being fed with JH. These results suggest the critical role of miR-1175-3p in JH-regulated reproduction, shedding light on the molecular mechanism underlying miRNA-mediated fecundity in social insects and providing a novel strategy for managing S.invicta.

Impact of Plant Symbiotic Endophytic Fungus, Aspergillus terreus on Insect Herbivore Spodoptera litura (Fabricius) (Lepidoptera: Noctuidae).

Herbivorous insects are known to be resistant to fungal endophytes that asymptomatically inhabit plant tissues. The insecticidal ability of the endophytic fungus Aspergillus terreus isolated from Catharanthus roseus against Spodoptera litura (Fabricius) was assessed in the current study. The survival and growth of S. litura were adversely impacted by the ethyl acetate extract of endophytic A. terreus. Fungal extract supplemented diet caused 14 to 94% larval mortality in comparison to 2% in control. Additionally, retarded insect growth was observed after ingestion of supplemented diet. The fungal metabolites were also observed to have an inhibitory influence on the adult emergence and reproductive potential of adults. Phytochemical analysis revealed the presence of phenolic compounds in the crude extract of endophytic fungus which may be responsible for toxicity. It was also determined how endophyte-infected cauliflower plants affected S. litura's survival and growth. Endophyte-infected plants exhibited resistance to S. litura by causing 54% larval mortality and delaying development by 5.2days. In comparison to uninfected plants, adult emergence, lifespan, fecundity and egg hatchability of insects was significantly decreased on infected plants. There was a significant decrease in relative growth and consumption rates as well as in the efficiency of food conversion, which indicates toxic and antifeedant effect of the fungus on S. litura. This suggests that endophyte-inoculated plants exhibit antibiosis against S. litura. In conclusion, the endophytic fungi having insecticidal activity could be used to develop alternative ecologically safe control strategies.

Variations in the Biological and Ecological Attributes of Insects Due to Climate Change: A Review

Climate change is causing a shift in long-term weather patterns and altering parameters such as temperature, atmospheric CO 2 , and precipitation patterns. It is likely to be an indirect effect of greenhouse gases and their enhancement in the atmosphere largely induced by human activities. As poikilothermic animals, insects are highly dependent on environmental conditions, particularly temperature, which affects various aspects of their life. Climate change have a direct impact on insect pests by affecting their population dynamics, diurnal activity, growth rate and diapause. It may lead to a range expansion, increased overwintering survival, more generations per year, elevated risk of invasive insect species and insect-borne plant diseases, and changes in their interactions with host plants and natural predators. Indirectly, changes in climate can modify host plants and competitors, further complicating the effect on insect biology and phenology. Impact of elevated CO 2 levels on their host plants can affect growth rates, fecundity, and population densities of insects. Altered precipitation patterns, such as droughts and floods, affect insect survival and diapause. Further, there is significant implications of climate change on different aspects of insect ecology, including insect distribution, behavior, and communication. The climate changes are predicted to alter the geographic ranges and migration behavior of insect species, creating new ecological niches and removing low-temperature barriers. These changes can threaten food security and increase the latitudinal and altitudinal range of crop pests. It also affects natural enemies, which can decrease the plant defense system against insect pests. Additionally, climate change can affect pheromonal communication, including production to behavioral response, in insects that rely on long-range chemical signals for communication. The review paper highlights the potential impacts of climate change on insect biological, phenological and ecological aspects.

A ferritin protein is involved in the development and reproduction of the whitefly, Bemisia tabaci.

Ferritins are conserved iron-binding proteins that exist in most living organisms and play an essential role in the maintenance of cellular iron homeostasis. Although ferritin has been studied in many species, little is known about its role in the whitefly, Bemisia tabaci. In this study, we identified an iron-binding protein from B. tabaci and named it BtabFer1. The full-length cDNA of BtabFer1 is 1,043 bp and encodes a protein consisting of 224 amino acids with a deduced molecular weight of 25.26 kDa, and phylogenetic analysis shows that BtabFer1 is conserved among Hemiptera insects. The expression levels of BtabFer1 in different developmental stages and tissues were analyzed by real-time PCR, and results showed that BtabFer1 was ubiquitously expressed at all developmental stages and in all examined tissues. The RNAi-mediated knockdown of BtabFer1 caused a significant reduction in survival rate, egg production, and egg hatching rate of whiteflies. Knockdown of BtabFer1 also inhibited the transcription of genes in the juvenile hormone signal transduction pathway. Taken together, these results suggest that BtabFer1 plays a critical role in the development and reproduction of whiteflies. This study can broaden our understanding of ferritin in insect fecundity and development, as well as provide baseline data for future studies.

The carboxypeptidase B and carbonic anhydrase genes play a reproductive regulatory role during multiple matings in Ophraella communa.

Seminal fluid proteins (SFPs) are key factors in sexual reproduction and are transferred to females during mating with sperm. SFPs have a nutritional value because they protect and activate sperm storage and release to optimize fecundity. Multiple matings promote ovipositioning in several insect species. Therefore, insects may obtain more SFP through multiple matings to maximize reproduction, but this process has not yet been clearly confirmed. Here, the relationship between multiple matings and the SFPs in Ophraella communa (Coleoptera: Chrysomelidae), a biological control agent of the common ragweed Ambrosia artemisiifolia (Asterales: Asteraceae), was studied. Multiple matings significantly increased female fecundity and ovary egg deposition. Carboxypeptidase B (OcCpb) and carbonic anhydrase (OcCa) genes were identified as putative SFP genes in O. communa and they showed strong male-biased expression. Additionally, OcCpb and OcCa expression was upregulated in the bursa copulatrix of mating females compared to that in virgin females, but their expression gradually declined after copulation. Furthermore, OcCpb and OcCa knockdown in males led to a decrease in insect fecundity compared to that in the control. The reproductive tract of females mated with dsRNA-treated males was dissected and observed and, notably, the ovaries produced significantly fewer eggs. These data suggest that OcCpb and OcCa play regulatory roles during multiple matings in O. communa.

Diamide seed treatment may protect early soybean growth stages against Helicoverpa armigera

In intensive soybean cropping systems, early-season pest insects such as lepidopteran larvae can seriously compromise crop establishment. Using a polyphagous global pest ̶̶ the Old World bollworm Helicoverpa armigera (Lepidoptera: Noctuidae), we determined the potential of seed treatments with diamide or neonicotinoid-carbamate mixture for systemic plant protection and residual efficacy against noctuid larvae. In controlled edaphoclimatic conditions, we infested differently aged soybean plants and recorded plant damage and insect mortality, growth, development, and fecundity to assess lethal and sublethal post-exposure effects. The seed treatments reduced plant damage by 50% during 1–7 days after plant emergence. The lowest damage (<25% defoliation) occurred on plants treated with chlorantraniliprole or cyantraniliprole. These diamides caused larval mortality >80% until 14 days after soybean emergence, which was the window of residual control efficacy. Carbofuran or thiodicarb + imidacloprid caused less than 50% larval mortality and minor plant protection against the larvae. There were sublethal effects on the growth, development, and fecundity of the insects surviving on plants of the insecticide seed treatments. The diamide seed treatments reduced the overall insect fitness for a longer time after plant emergence than did the other treatments. Therefore, soybean seed treatment with chlorantraniliprole or cyantraniliprole is potentially efficacious against noctuid larvae in the VE–V1 soybean growth stages (emergence until the first trifoliate), causing lethal and sublethal effects on the insects. Judicious use and effective resistance management for these systemic compounds are relevant as they are helpful for seed treatment and foliar applications against diverse targets.

The N-terminal subunit of vitellogenin in planthopper eggs and saliva acts as a reliable elicitor that induces defenses in rice.

Vitellogenins (Vgs) are critical for the development and fecundity of insects. As such, these essential proteins can be used by plants to reliably sense the presence of insects. We addressed this with a combination of molecular and chemical analyses, genetic transformation, bioactivity tests, and insect performance assays. The small N-terminal subunit of Vgs of the planthopper Nilaparvata lugens (NlVgN) was found to trigger strong defense responses in rice when it enters the plants during feeding or oviposition by the insect. The defenses induced by NlVgN not only decreased the hatching rate of N.lugens eggs, but also induced volatile emissions in plants, which rendered them attractive to a common egg parasitoid. VgN of other planthoppers triggered the same defenses in rice. We further show that VgN deposited during planthopper feeding compared with during oviposition induces a somewhat different response, probably to target the appropriate developmental stage of the insect. We also confirm that NlVgN is essential for planthopper growth, development, and fecundity. This study demonstrates that VgN in planthopper eggs and saliva acts as a reliable and unavoidable elicitor of plant defenses. Its importance for insect performance precludes evolutionary adaptions to prevent detection by rice plants.

Response of the soft scale insect Parthenolecanium corni and its natural enemies on honeylocust trees to urban conditions

Urban habitats can alter tree physiology in ways that make trees more susceptible to insect pests. We examined how urban conditions (e.g., impervious surfaces and warming) affected the soft scale insect, European fruit lecanium, Parthenolecanium corni Bouché (Hemiptera: Coccidae) and the health of thornless honeylocust trees (Gleditsia tricanthos L. var. inermis) in Indianapolis, Indiana, USA. Hot and cool study sites were selected based on surface air temperatures obtained from thermal LANDSAT-8 images overlaid against a map of honeylocust tree locations. Based on temperature probe data, study trees located in hot sites had mean average daily temperatures up to 1.56 °C and 1.79 °C warmer than cool sites in 2019 and 2020, respectively. We hypothesized that abundance and fecundity of scale insects would be higher on trees in hot sites and those surrounded by more impervious surface cover within a 20 m radius. Although our data supported these hypotheses, impervious surface cover predicted more of the variation in abundance and fecundity of scale insects in hot sites compared to cool sites. Rates of parasitism were not affected by impervious surface cover or whether the site was from a hot or cool location. However, we found strong density dependence in parasitism of scale insects in both hot and cool sites when scale densities were at or below the levels present in cool sites. This suggests that lower densities of scale insects were associated with a positive numerical response of parasitoids, a necessary prerequisite for population regulation by top-down effects. In contrast, this numerical response was lacking at the higher densities of scales found on trees located in hot sites where, presumably bottom-up factors like water-stress increased the fecundity of scale insects. These findings add to a growing body of evidence linking rising global temperatures with increased pest abundance in ways that cannot be mitigated by local populations of natural enemies.

Capsaicin decreases fecundity in the Asian malaria vector Anopheles stephensi by inhibiting the target of rapamycin signaling pathway

BackgroundMosquito-borne diseases threaten human health, but mosquito control faces various challenges, such as resistance to chemical insecticides. Thus, there is an urgent need for more effective and environment-friendly control agents. Capsaicin can downregulate the mTOR signaling pathway of tumor cells. The TOR signaling pathway can mediate the expression of vitellogenin (Vg) to regulate the fecundity of insects. Whether capsaicin has the potential to inhibit fecundity of mosquitoes by regulating TOR pathway and Vg expression is currently unclear.MethodsAnopheles stephensi were fed with blood of mice administered capsaicin by gavage or sugar containing capsaicin followed by a blood feeding with normal mice. Then, the engorged female mosquitoes were tubed individually and underwent oviposition. The eggs and individuals in the subsequent development stages, including larvae, pupae, and emerging adults, were counted and compared between the capsaicin treatment and control groups. Additionally, total RNA and protein were extracted from the engorged mosquitoes at 24 h post blood feeding. Real-time PCR and western blot were performed to detect the transcriptional level and protein expression of the key fecundity-related molecules of mosquitoes. Finally, TOR signaling pathway was inhibited via rapamycin treatment, and changes in fecundity and the key molecule transcription and protein expression levels were examined to verify the role of TOR signaling pathway in the effect of capsaicin on mosquito fecundity.ResultsThe laid and total eggs (laid eggs plus retained eggs) of An. stephensi were significantly reduced by feeding on the blood of capsaicin-treated mice (P < 0.01) or capsaicin-containing sugar (P < 0.01) compared with those in the control group. Moreover, the transcription and protein expression or phosphorylation levels of fecundity-related molecules, such as Akt, TOR, S6K, and Vg, were significantly decreased by capsaicin treatment. However, the effects disappeared between control group and CAP group after the TOR signaling pathway was inhibited by rapamycin.ConclusionsCapsaicin can decrease the fecundity of An. stephensi by inhibiting the TOR signaling pathway. These data can help us to not only understand the effect of capsaicin on the reproductive ability of An. stephensi and its underlying mechanism, but also develop new efficient, safe, and pollution-free mosquito vector control agents.Graphical

Burkholderia gut symbiont induces insect host fecundity by modulating Kr-h1 gene expression.

Full-length cDNAs of the Broad-Complex (BR-C) from Riptortus pedestris were cloned. Moreover, Kr-h1 and BR-C expression levels in apo-symbiotic and symbiotic host insects were compared to verify whether they are modulated by Burkholderia gut symbionts. Interestingly, Kr-h1 expression level was significantly increased in symbiotic females. To determine how Kr-h1 affects fecundity in insects, the biosynthesis of two reproduction-associated proteins, hexamerin-α and vitellogenin, was investigated in R. pedestris females. Hexamerin-α and vitellogenin expression at the transcriptional and translational levels decreased in Kr-h1-suppressed symbiotic females, subsequently reduced egg production. These results suggest that Burkholderia gut symbiont modulates Kr-h1 expression to enhance ovarian development and egg production of R. pedestris by increasing the biosynthesis of the two proteins.

Genome-wide identification of FAR gene family and functional analysis of NlFAR10 during embryogenesis in the brown planthopper Nilaparvata lugens

Fatty acyl-CoA reductases (FARs) catalyze the synthesis of fatty alcohols from corresponding fatty acid precursors in organisms. However, the function of FARs in insect fecundity and embryogenesis remains largely unclear. Here, a total of 22 putative FAR proteins were identified in the brown planthopper Nilaparvata lugens, a hemipteran insect pest of rice, and most of them were highly expressed in embryonic stages. Among them, NlFAR10 was specifically and highly expressed in the later embryogenesis, but was promiscuously expressed in tissues of adults. The heterologously expressed NlFAR10 was able to produce the intermediate fatty acid alcohols from the corresponding acyl-CoA precursors. When NlFAR10 was silenced through RNAi in vivo, the embryogenesis was obviously inhibited, resulting in low hatching rates. Moreover, the metabolome analyses indicated that loss of NlFAR10 affected lipid metabolism and purine metabolism during embryogenesis. To the best of our knowledge, this is the first report of a FAR member affecting insect embryogenesis, thus providing a new target for future pest management.

Callosobruchus larval competition and its consequences for male and female adults

AbstractThe struggle for life is generally the most intense among individuals of the same species because they compete to access the same food, territory, and mates. In the current study, we used Callosobruchus maculatus to investigate how males and females respond to a competitor's presence inside a bean. We monitored males' and females' from egg to adult developmental time, adult emergence, copulation success, copulatory behaviors, fecundity, egg hatching percentage, and adult longevity. Our findings revealed that a competitor's presence during immature life did not influence developmental time and adult longevity in females and males. Also, the environmental condition of living with a potential competitor in the immature stages could not significantly affect adult beetle mating behaviors compared to beetles reared alone. However, female larvae were more likely to interfere with competitors than males. Females' neighbors died sooner (mainly in the larval stage) than males (primarily as pupae). Also, when we paired males and females whose competitors died in the larval stage, female adult longevity decreased compared to without competitor control pairs. However, male adult longevity in all examined pairs was similar and was not affected by their mate's conditions. A competitor's presence during larval development decreased the insect fecundity and, at the same time, increased egg hatching percentage in all treatments regardless of the competitor's sex, or if the competitor died, compared to the control (reared alone individuals). In all, females show more interference than males toward a potential competitor.

Flight Performance, Fecundity, and Ovary Development of Grapholita molesta (Lepidoptera: Torticidae) at Different Ages.

Simple SummaryNew environment-friendly strategies, such as the sterile insect technique (SIT), are urgently needed to manage populations of Grapholita molesta, a serious fruit pest. When mass-rearing the insect in a factory, assessments of various appropriate quality control parameters are essential. Flight ability, fecundity, and ovarian development are critical quality control parameters to be measured for moths being mass-produced. In this study, we found that that the flight performance, fecundity, and ovarian development of G. molesta moths changed with age. The fecundity of G. molesta at different ages was closely related to the ovarian development. G. molesta females began to lay eggs in large numbers from the third day after emergence. It is suggested that three-day-old males are the best option for releasing G. molesta for SIT. When mass-rearing and keeping the population of the moth in factory, female moths older than three days can be used for egg-laying.Grapholita molesta is one of the most serious pests in fruits orchards. Flight performance of male insects and fecundity of female insects are important quality control parameters when moths are mass-reared for use in environment-friendly control strategies such as the sterile insect technique (SIT). However, information about flight performance, fecundity, and ovary development of G. molesta at different ages is scarce. In this study, we used a flight mill information system to measure the flight ability of female and male adults of G. molesta at different ages, and evaluated fecundity and ovarian development of female adults at different ages. The results demonstrated that the flight parameters (cumulative flight distance, cumulative flight time, maximum flight distance and maximum flight duration) of female and male G. molesta varied with age. Six-day-old female moths and three-day-old male moths were the strongest fliers, whereas the fecundity of one-day and two-day-old female moths was significantly lower than that of three to seven-day-old females. Five-day-old females had the highest fecundity. Their ovaries demonstrated mature eggs in the lateral and middle oviducts as of the third day post-emergence. It is suggested that the optimal age for moths to be released in SIT programs is three days, and moths older three days can be used for mass-rearing in a factory.

Flight-Fecundity Trade-offs: A Possible Mechanistic Link in Plant-Herbivore-Pollinator Systems.

Plant–herbivore and plant–pollinator interactions are both well-studied, but largely independent of each other. It has become increasingly recognized, however, that pollination and herbivory interact extensively in nature, with consequences for plant fitness. Here, we explore the idea that trade-offs in investment in insect flight and reproduction may be a mechanistic link between pollination and herbivory. We first provide a general background on trade-offs between flight and fecundity in insects. We then focus on Lepidoptera; larvae are generally herbivores while most adults are pollinators, making them ideal to study these links. Increased allocation of resources to flight, we argue, potentially increases a Lepidopteran insect pollinator’s efficiency, resulting in higher plant fitness. In contrast, allocation of resources to reproduction in the same insect species reduces plant fitness, because it leads to an increase in herbivore population size. We examine the sequence of resource pools available to herbivorous Lepidopteran larvae (maternally provided nutrients to the eggs, as well as leaf tissue), and to adults (nectar and nuptial gifts provided by the males to the females), which potentially are pollinators. Last, we discuss how subsequent acquisition and allocation of resources from these pools may alter flight–fecundity trade-offs, with concomitant effects both on pollinator performance and the performance of larval herbivores in the next generation. Allocation decisions at different times during ontogeny translate into costs of herbivory and/or benefits of pollination for plants, mechanistically linking herbivory and pollination.

Population density modulates insect progenitive plasticity through the regulation of dopamine biosynthesis.

Insect fecundity is a quantitative phenotype strongly affected by genotypes and the environment. However, interactions between genotypes and environmental factors in modulating insect fecundity remain largely unknown. This study investigated the impact of population density on the fecundity of Nilaparvata lugens (brown planthopper; BPH) carrying homozygous high- (HFG) or low- (LFG) fecundity homozygous genotypes. Under low population densities, the fecundity and population growth rate of both genotypes showed similar increasing trends across generations, while the trends between HFG and LFG under high population densities were opposite. Through a combination of temporal analysis and weighted gene co-expression network analyses on RNA-seq data of HFG and LFG under low and high population densities in the 1st, 3rd, and 5th generations, we identified 2 gene modules that were associated with these density-dependent progenitive phenotypes. Four pathways related to the neural system were simultaneously enriched by the 2 gene modules. Furthermore, Nlpale, which encodes a tyrosine hydroxylase, was identified as a key gene. The RNA interference of this gene and manipulation of its downstream product dopamine significantly affected the basic and density-dependent progenitive phenotypes of BPH. These findings indicated that dopamine biosynthesis is the key regulatory factor that determines fecundity in response to density changes in different BPH genotypes. Thus, this study provides insights into the interaction of a typical environmental factor and insect genotype during the process of population regulation.