Adult Longevity Research Articles

Thiamethoxam-Induced Intergenerational Sublethal Effects on the Life History and Feeding Behavior of Rhopalosiphum padi

Thiamethoxam, a second-generation neonicotinoid insecticide is widely used for controlling sap-sucking insect pests including Rhopalosiphum padi. The current study aimed to investigate the life-history parameters and feeding behavior of R. padi following treatments with sublethal concentrations of thiamethoxam. The lethal concentration 50 (LC50) value of thiamethoxam against adult R. padi was 11.458 mg L−1 after 48 h exposure. The sublethal concentrations of thiamethoxam (LC5 and LC10) significantly decreased the adult longevity, fecundity, and reproductive days in the directly exposed aphids (F0 generation). In the progeny R. padi (F1), the developmental durations and total prereproductive period (TPRP) were decreased while the adult longevity, fecundity, and reproductive days (RPd) were increased at both thiamethoxam concentrations. The demographic parameters including the net reproductive rate (R0), intrinsic rate of increase (r), and finite rate of increase (λ) were prolonged only at the LC5 of thiamethoxam. The EPG results indicated that the sublethal concentrations of thiamethoxam increases the total duration of non-probing (Np) while reducing the total duration of E2 in directly exposed aphids (F0). Interestingly, the E2 were significantly increased in the progeny generation (F1) descending from previously exposed parental aphids (F0). Overall, this study showed that thiamethoxam exhibited high toxicity against directly exposed individuals (F0), while inducing intergenerational hormetic effects on the progeny generation (F1) of R. padi. These findings provided crucial details about thiamethoxam-induced hormetic effects that might be useful in managing resurgences of this key pest.

Sublethal effect and detoxifying metabolism of metaflumizone and indoxacarb on the fall armyworm, Spodoptera frugiperda

The fall armyworm (FAW), Spodoptera frugiperda (J.E. Smith) (Lepidoptera, Noctuidae), is a highly polyphagous invasive pest that damages various crops. Pesticide control is the most common and effective strategy to control FAW. In this study, we evaluated the toxicity of metaflumizone and indoxacarb against third-instar FAW larvae using the insecticide-incorporated artificial diet method under laboratory conditions. Both metaflumizone and indoxacarb exhibited substantial toxicity against FAW, with LC50 values of 2.43 and 14.66 mg/L at 72 h, respectively. The sublethal effects of metaflumizone and indoxacarb on parental and F1 generation FAW were investigated by exposing third-instar larvae to LC10 and LC30 concentrations of these insecticides. Sublethal exposure to these two insecticides significantly shortened adult longevity, extended pupal developmental times and led to reduced pupal weight, pupation rates, and adult fecundity in the treated parental generation and F1 generation at LC10 or LC30 concentrations, in comparison to the control group. The larval developmental times were shortened in the parental generation but prolonged in the F1 generation, after being treated with sublethal concentrations of metaflumizone. Furthermore, larvae exposed to LC10 or LC30 concentrations of indoxacarb exhibited elevated activity levels of cytochrome P450 monooxygenase and glutathione S-transferase, which coincides with the observed synergistic effect of piperonyl butoxide and diethyl maleate. In conclusion, the high toxicity and negative impact of metaflumizone and indoxacarb on FAW provided significant implications for the rational utilization of insecticides against this pest.

Prey stage preference of Amblyseius paraaerialis (Acari: Phytoseiidae) on varied life stages of the spider mites Tetranychus urticae, Tetranychus macfarlanei and Oligonychus biharensis (Acari: Tetranychidae) and exploring the mass rearing possibilities of this predatory mite on alternative diets.

Spider mites Tetranychus urticae, Tetranychus macfarlanei and Oligonychus biharensis are considered to be highly polyphagous in nature and causes severe damage to a wide range of plants around the world. Amblyseius paraaerialis is an efficient phytoseiid predator of spider mites with a potential to survive on both natural and alternative diets. Evaluation of predatory potential and prey stage preference provides valuable information on the efficacy of the predatory species in controlling mite population. Feeding experiments were conducted on mulberry leaf discs under the laboratory conditions of 30 ± 2 °C and 70 ± 5% relative humidity (RH). After 24h of feeding experiment, the adult female predator exhibited a significant preference in feeding towards the eggs of T. macfarlanei (42.6%) and the larval stages of T. urticae (46%) and O. biharensis (25.3%). The mass rearing possibilities of A. paraaerialis was tested by tracking and comparing the developmental duration of individual life stages on varied food sources like, honey, castor (Ricinus communis) pollen, honey-pollen mixture and mixed life stages of T. urticae. The predator was failed to complete its development on honey and pollen when supplied separately. However it was successfully developed on honey-pollen mixture and mixed life stages of T. urticae. The developmental studies unravelled a shortest developmental duration and an extended adult longevity and lifespan of A. paraaerialis when reared on the alternative diet, thus opened up the mass rearing possibility of the predatory species under laboratory conditions.

Hormetic effects of thiamethoxam on Schizaphis graminum: demographics and feeding behavior

In agroecosystems, insects contend with chemical insecticides often encountered at sublethal concentrations. Insects’ exposure to these mild stresses may induce hormetic effects, which has consequences for managing insect pests. In this study, we used an electrical penetration graph (EPG) technique to investigate the feeding behavior and an age-stage, two-sex life table approach to estimate the sublethal effects of thiamethoxam on greenbug, Schizaphis graminum. The LC5 and LC10 of thiamethoxam significantly decreased longevity and fecundity of directly exposed adult aphids (F0). However, the adult longevity, fecundity, and reproductive days (RPd)—indicating the number of days in which the females produce offspring – in the progeny generation (F1) exhibited significant increase when parental aphids (F0) were treated with LC5 of the active ingredient. Subsequently, key demographic parameters such as intrinsic rate of increase (r) and net reproductive rate (R0) significantly increased at LC5 treatment. EPG recordings showed that total durations of non-probing (Np), intercellular stylet pathway (C), and salivary secretion into the sieve element (E1) were significantly increased, while mean duration of probing (Pr) and total duration of phloem sap ingestion and concurrent salivation (E2) were decreased in F0 adults exposed to LC5 and LC10. Interestingly, in the F1 generation, total duration of Np was significantly decreased while total duration of E2 was increased in LC5 treatment. Taken together, our results showed that an LC5 of thiamethoxam induces intergenerational hormetic effects on the demographic parameters and feeding behavior of F1 individuals of S. graminum. These findings have important implications on chemical control against S. graminum and highlight the need for a deeper understanding of the ecological consequences of such exposures within pest management strategies across the agricultural landscapes.

The association between body height and longevity: evidence from a national population sample.

A wealth of research suggests that taller individuals are healthier and live longer than their shorter counterparts, although conflicting results have been reported. This study aims to investigate whether taller individuals in Poland exhibit greater longevity compared to their shorter counterparts. Data on declared height were collected from 848,860 adults who died in the years 2004-2008 in Poland. To eliminate the cohort effects, Z-values were computed. Pearson's correlation coefficients were calculated independently for males and females. Subsequently, one way ANOVA was performed. The correlation between adult height and longevity was negative and statistically significant in both men and women. After eliminating the effects of secular trends in height, the correlation was very weak (r = -0.0044 in men and r = -0.0038 in women) but significant (p = 0.023 and p = 0.022, respectively). Despite the significant correlation observed between the two variables, it should be noted that the relationship between height and longevity is very weak and tenuous. Overall, these results do not support the hypothesis that taller individuals have a longevity advantage. Further research is warranted to identify the underlying biological mechanisms driving this phenomenon as well as to explore additional variables affecting human longevity.

Demographic analysis of the biological parameters of Spodoptera frugiperda after sublethal exposure to insecticides

Spodoptera frugiperda (JE Smith) is one of the most destructive pests, causing serious yield losses of corn on all continents except Europe. Low-lethal concentrations of insecticides may affect not only the survival rate but also the demographic parameters of a pest. To understand the effect of low-lethal concentrations of insecticides on S. frugiperda, the developmental parameters after low-lethal concentrations treatment by three different modes of action pesticides tetrachlorantraniliprole, spinetoram, and lufenuron were analyzed. For F0 generation, the pupal length and weight of FAW after insecticide treatment were significantly longer and heavier than that of control. For the F1 generation, the adult longevity and egg hatching rate after spinetoram and lufenuron treated was significantly shorter and lower than that of the control. While no significant effect was observed for the intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) of S. frugiperda, the net reproductive rate (R0) significant decreased after the spinetoram and lufenuron treatment. Results showed tetrachlorantraniliprole, spinetoram, and lufenuron negatively affect larval survival rate, but spinetoram and lufenuron caused early maturity, and all three insecticide treatments increased egg reproduction. The results of this study suggest that low-lethal concentration exposure to insecticides negatively impacts the life table parameters of S. frugiperda, and those three insecticides from different modes of action cannot cause FAW resurgence and can be recommended as insecticides to control FAW. Those results will be helpful for researchers working on S. frugiperda management using chemical pesticides in an integrated pest management program.

Intergenerational Effects of Sublethal Lambda-Cyhalothrin Exposure on Aphis gossypii Glover (Hemiptera: Aphididae) Reproduction and Development.

Aphis gossypii Glover, a widespread insect, presents a substantial danger to global agriculture. Lambda-cyhalothrin is a pyrethroid insecticide that has been widely studied for its effects on arthropods. Studies have reported that sublethal doses of insecticides can produce various consequences on arthropod reproduction. Hence, the objective of this research was to examine the potential effects of a sublethal dose of lambda-cyhalothrin (LC30, 1.15 mg/L) on A. gossypii, for which we created life tables and conducted qPCR analysis. Adult longevity, fecundity, net reproductive rate (R0), body length, width, weight, and the expression of vitellogenin (Vg) and vitellogenin receptor (VgR) genes were not significantly altered by lambda-cyhalothrin treatment at LC30 concentration in the F0 generation of A. gossypii adults. The intrinsic rate of increase (r) and finite rates of increase (λ) decreased significantly, while the mean generation time (T) increased. In addition, Vg and VgR gene expression levels were significantly higher in the F1 and F2 generations, whereas body length, width, and weight were notably reduced. The developmental duration, longevity, r, and λ did not differ significantly from those of the control group. Thus, the sublethal and intergenerational stimulatory effects of lambda-cyhalothrin were observed in A. gossypii, and the alterations in Vg and VgR in A. gossypii were strongly associated with sublethal effects. The results of this research offer valuable knowledge regarding the indirect impacts of lambda-cyhalothrin on A. gossypii, which can be utilized as a theoretical foundation for the prudent utilization of insecticides to combat this pest and devise strategies for managing resistance.

Lethal and sublethal effects of fluralaner on the citrus red mite, Panonychus citri (McGregor).

The citrus red mite, Panonychus citri (McGregor) is a globally distributed agricultural pest. Of late, resistance to common acaricides has raised concerns that chemical control of P. citri is an inefficient means of control. Fluralaner, a highly toxic isoxazoline insecticide used to treat various ectoparasites, presents one potential alternative. However, little information has been reported about the effect of fluralaner on the citrus red mite. This study aims to evaluate the toxicity, sublethal and transgenerational effects of fluralaner on P. citri. In both laboratory and field populations of P. citri, we found fluralaner to be more toxic than conventional alternatives, including fenpropathrin, bifenazate, azocyclotin and chlorpyrifos. Interestingly, fluralaner proved more toxic to female adults than to the eggs of P. citri, with median lethal concentrations (LC50) of 2.446 and 122.7 mg L-1, respectively. Exposure to sublethal concentrations of fluralaner (LC10, LC20 and LC30) significantly reduced the fecundity and longevity of female adults P. citri individuals. Although concentrations of fluralaner applied to the parental female adults (F0) led to some changes in the developmental parameters, there were no significant changes in most of the life table parameters or population growth of the F1 generation. Our results indicate that fluralaner is highly toxic to P. citri, and a significant sublethal effect on F0 could suppress the population growth of P. citri, but not for F1. Fluralaner may be considered as a pesticide for the future management of the citrus red mite. © 2024 Society of Chemical Industry.

Toxicity evaluation of novel imidacloprid nanoribbons, using somatic mutation and fitness indexes in Drosophila melanogaster

ABSTRACT Nanoribbons of imidacloprid, a systemic and chloronicotinyl insecticide, were successfully synthesized by laser-induced fragmentation/exfoliation of imidacloprid powders suspended in water, with widths ranging from 160 to 470 nm, lengths in the micron scale, and thickness of a few atoms layers. The aim of the present study was to examine the effects of acute and chronic exposure to imidacloprid (IMC) bulk and compare its effects with synthesized imidacloprid nanoribbons (IMCNR) on larval and adult viability, developmental time, olfactory capacity, longevity, productivity, and genotoxicity in Drosophila melanogaster. Larvae or adults were exposed at 0.01, 0.02, or 0.03 ppm to IMC or IMCNR. Results demonstrated that IMCNR produced a significant reduction in viability and olfactory ability. IMC did not significantly alter viability and olfactory ability. Similarly, marked differences on longevity were detected between treatment with IMC and IMCNR where the lifespan of males treated with IMC was significantly higher than control while IMCNR produced a reduction. As for productivity, developmental time, and genotoxicity, no marked differences were found between both forms of IMC.

Effects of thiamethoxam on physiological and molecular responses to potato plant (Solanum tuberosum), green peach aphid (Myzus persicae), and parasitoid (Aphidius gifuensis).

To improve integrated pest management (IPM) performance it is essential to assess pesticide side effects on host plants, insect pests, and natural enemies. The green peach aphid (Myzus persicae Sulzer) is a major insect pest that attacks various crops. Aphidius gifuensis is an essential natural enemy of M. persicae that has been applied effectively in controlling M. persicae. Thiamethoxam is a neonicotinoid pesticide widely used against insect pests. The current study showed the effect of thiamethoxam against Solanum tuberosum, M. persicae, and A. gefiuensis and the physiological and molecular response of the plants, aphids, and parasitoids after thiamethoxam application. Thiamethoxam affected the physical parameters of S. tuberosum and generated a variety of sublethal effects on M. persicae and A. gefiuensis, including nymph development time, adult longevity, and fertility. Our results showed that different thiamethoxam concentrations [0.1, 0.5, and 0.9 μm active ingredient (a.i.)/L] on different time durations (2, 6, and 10 days) increased the antioxidant enzyme activities SOD, POD, and CAT of S. tuberosum, M. persicae, and A. gefiuensis significantly compared with the control. Our results also showed that different thiamethoxam concentrations (0.1, 0.5, and 0.9 μm a.i./L) on different time durations (2, 6, and 10 days) increased the expression of superoxide dismutase (SOD), peroxidase (POD), catalase (CAT), acetylcholinesterase (AChE), carboxylesterase (CarE) and glutathione-S-transferase (GST) genes of S. tuberosum, M. persicae, and A. gefiuensis compared with the control. Our findings reveal that using thiamethoxam at suitable concentrations and time durations for host plants and natural enemies may enhance natural control through the conservation of natural enemies by overcoming any fitness disadvantages. © 2024 Society of Chemical Industry.

Effect of X-ray irradiation on the biological parameters of Xestia c-nigrum.

The sterile insect technique (SIT) is widely used to control Lepidopteran pests by inducing inherited sterility. The noctuid moth Xestia c-nigrum is a polyphagous pest whose subterranean larvae severely injure cereals and some vegetables. The goals of this study were to assess the impact of X-ray irradiation on the development and survival of X. c-nigrum and use the data to select suitable sterilizing doses for potential future use in pest management. Batches of male pupae were exposed to 0 (control), 10, 30, 50, 100, 200, 300, or 400Gy of X-rays, approximately 24h before adult emergence. Exposure of late-stage pupae to 10-200Gy of radiation had no significant effect on adult emergence, but all doses (10-400Gy) reduced adult longevity, the number of spermatophores in mated females, and the number of eggs laid per female in the irradiated parental generation compared with the controls. Exposure to 10 and 30Gy had no significant effects in the F1 generation on 1) the rate of egg hatch, 2) the duration of larval or pupal development, or 3) adult longevity. However, exposure to 50Gy reduced the rate of egg hatch in the F1 generation, and when male pupae were exposed to 100Gy only 1% of the F1 eggs hatched. Also at 100Gy, the developmental durations of larvae and pupae were significantly prolonged, and longevity of adult moths was reduced. There were no significant differences between the control group and any treatments in 1) the sex ratio of the F1 adults, 2) the duration of F1 pre-oviposition or oviposition periods, or 3) the number of eggs laid per F1 female. Our findings indicate that a dose of 100Gy can effectively slow pest development and reduce larval survival in the F1 generation. In addition, F1 adults from lines treated with 100Gy were able to mate and lay eggs, but all F2 eggs failed to hatch. Our results suggest that use of X-ray irradiation has potential to control this polyphagous pest at the regional level.

Characterization of Spodoptera littoralis (Lepidoptera: Noctuidae) resistance to indoxacarb: inheritance mode, realized heritability, and fitness costs.

Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae) is a major economic pest attacking a variety of crops in Egypt and other Mediterranean countries. S. littoralis has developed resistance to both traditional and novel insecticides. The current study investigated S. littoralis resistance to indoxacarb regarding inheritance mode, realized heritability (h2), and fitness costs. An indoxacarb-resistant strain (Indoxa-SEL) was obtained by selecting a field strain with indoxacarb. Indoxa-SEL strain outperformed the susceptible one (Indoxa-S) by 29.77-fold after 16 consecutive generations of selection. Based on the LC50 values of the progenies of reciprocal crosses F1 (R♂ × S♀) and F1' (R♀ × S♂), S. littoralis resistance to indoxacarb was found to be autosomal and partially recessive. Chi-square tests for goodness-of-fit between observed and expected mortalities of self-bred F1 and resistant strain reciprocal crosses revealed that the resistance was controlled by multiple genes. The resistant strain had a relative fitness of 0.80, with significantly increased total preovipositional period of females, egg, larvae, pupae, preadult, adult, and total longevity period. The estimated realized heritability value in the Indoxa-SEL strain was 0.21. The current study will contribute to sustaining indoxacarb efficacy and designing effective resistance management programs against S. littoralis.

Bioactivity and Sublethal Effects of Ageratina adenophora (Asteraceae) on Bactrocera dorsalis (Diptera: Tephritidae)

Abstract Local fruit orchards have incurred heavy losses due to invasive insects, including the oriental fruit fly, Bactrocera dorsalis (Hendel) (Diptera: Tephritidae), in Guizhou Province, China. In our efforts to manage this invasive pest, a laboratory study was conducted to evaluate the response of adult B. dorsalis to an extract of Ageratina adenophora (Spreng.) R.M. King & H. Rob (Gunneridae: Asteraceae). We evaluated the contact toxicity and oviposition-deterrent activity of the extract on adult B. dorsalis, as well as the sublethal effects on survival and reproduction. We found that the A. adenophora extract has significant insecticidal activity, with the 24-h median lethal concentration (LC50) for adults being 26.014 mg/ml. The extract of A. adenophora also showed oviposition inhibition. A residual deterrent effect (28.16%) was evident up to 5 d after treatment. Exposure to the LC25 concentration of the A. adenophora extract caused significant differences in preoviposition and fecundity, decreased adult longevity in the F0 generation, and decreased egg and pupa survival in the F1 generation. The levels of carboxylesterase enzyme activity in adults treated with the extract were significantly lower than those in the untreated controls at 12 h and 24 h. This latter phenomenon could perhaps be an adaptive response to the extract that might reduce its toxic effects in B. dorsalis.

Lysine-36 of Drosophila histone H3.3 supports adult longevity.

Aging is a multifactorial process that disturbs homeostasis, increases disease susceptibility, and ultimately results in death. Although the definitive set of molecular mechanisms responsible for aging remain to be discovered, epigenetic change over time is proving to be a promising piece of the puzzle. Several post-translational histone modifications have been linked to the maintenance of longevity. Here, we focus on lysine-36 of the replication-independent histone protein, H3.3 (H3.3K36). To interrogate the role of this residue in Drosophila developmental gene regulation, we generated a lysine-to-arginine mutant that blocks the activity of its cognate-modifying enzymes. We found that an H3.3BK36R mutation causes a significant reduction in adult lifespan, accompanied by dysregulation of the genomic and transcriptomic architecture. Transgenic co-expression of wild-type H3.3B completely rescues the longevity defect. Because H3.3 is known to accumulate in nondividing tissues, we carried out transcriptome profiling of young vs aged adult fly heads. The data show that loss of H3.3K36 results in age-dependent misexpression of NF-κB and other innate immune target genes, as well as defects in silencing of heterochromatin. We propose H3.3K36 maintains the postmitotic epigenomic landscape, supporting longevity by regulating both pericentric and telomeric retrotransposons and by suppressing aberrant immune signaling.

Low concentrations of cyantraniliprole negatively affects the development of Spodoptera frugiperda by disruption of ecdysteroid biosynthesis and carbohydrate and lipid metabolism

In addition to the acute lethal toxicity, insecticides might affect population dynamics of insect pests by inducing life history trait changes under low concentrations, however, the underlying mechanisms remain not well understood. Here we examined systemic impacts on development and reproduction caused by low concentration exposures to cyantraniliprole in the fall armyworm (FAW), Spodoptera frugiperda, and the putative underlying mechanisms were investigated. The results showed that exposure of third-instar larvae to LC10 and LC30 of cyantraniliprole significantly extended larvae duration by 1.46 and 5.41 days, respectively. Treatment with LC30 of cyantraniliprole significantly decreased the pupae weight and pupation rate as well as the longevity, fecundity and egg hatchability of female adults. Consistently, we found that exposure of FAW to LC30 cyantraniliprole downregulated the mRNA expression of four ecdysteroid biosynthesis genes including SfNobo, SfShd, SfSpo and SfDib and one ecdysone response gene SfE75 in the larvae as well as the gene encoding vitellogenin (SfVg) in the female adults. We also found that treatment with LC30 of cyantraniliprole significantly decreased the whole body levels of glucose, trehalose, glycogen and triglyceride in the larvae. Our results indicate that low concentration of cyantraniliprole inhibited FAW development by disruption of ecdysteroid biosynthesis as well as carbohydrate and lipid metabolism, which have applied implications for the control of FAW.

Demographic Parameters of Anthocoris minki Dohrn (Hemiptera: Anthocoridae) Reared on Common Bean (Phaseolus vulgaris L.), Faba Bean (Vicia faba L.) and Pea (Pisum sativum L.) as Egg Laying Media.

Anthocoris minki Dohrn (Hemiptera: Anthocoridae) is used as a biological control agent of various agricultural pests. This study determined the effect of different egg laying materials, i.e., faba bean, common bean, and pea on population parameters of A. minki using age-stage, two-sex life table. The longest (34.45 d) and the shortest (21.32 d) adult longevity was noted on common bean and pea, respectively. Likewise, the highest (92%) and the lowest (69%) preadult survival rate was recorded on faba bean and pea, respectively. The highest fecundity (93.74 eggs/female) was noted on faba bean followed by common bean (43.95 eggs/female) and pea (48.69 eggs/female). Oviposition period remained unaffected, while higher oviposition days (22 d) were noted on faba bean compared with common bean (10 d) and pea (14 d). The shortest and the longest adult pre-oviposition period and total pre-ovipositional period were calculated for common bean and pea, respectively. The highest intrinsic rate of increase (r) (0.1159 d-1) and finite rate of increase (λ) (1.1229 d-1) were noted on common bean, while the lowest (r = 0.0939 d-1; λ = 1.0985 d-1) were noted on pea. Paired bootstrap analyses indicated that the highest net reproductive rate (R0) (43.12 offspring) was recorded on faba bean. Egg hatching rate significantly differed among plants (P < 0.01) and it was 80.50%, 71.10%, and 38.90% on common bean, faba bean and pea, respectively. It is concluded that faba bean would be the most suitable host for mass rearing of A. minki, while pea proved unsuitable.

Chemotaxis response and age-stage, two-sex life table of the Cheilomenes sexmaculata (Fabricius) (Coccinellidae: Coleoptera) against different aphid species.

The Cheilomenes sexmaculata (Fabricius) (Coleoptera: Coccinellidae), is one of the most beneficial and identifiable predators of numerous soft-bodied and sucking insect pests of several crops. Biological parameters and olfactory response of C. sexmaculata were investigated under laboratory conditions by providing three different aphid species i.e., mustard aphid (Lipaphis erysimi Kaltenbach), citrus black aphid (Toxoptera citricida Kirkaldy), and peach aphid (Diuraphis noxia Kurdjumov) as a food source. The developmental period of immature stages of C. sexmaculata was shorter on D. noxia as compared to other aphid species. The adult longevities were longer on D. noxia and T. citricida while shorter on L. erysimi. Female fecundity was highest on D. noxia while lowest on L. erysimi. Life table parameters i.e., intrinsic rate of increase (r), finite rate of increase (λ), net reproductive rate (Ro), and gross reproductive rate (GRR) were maximum on D. noxia while minimum on L. erysimi. The mean generation time C. sexmaculata was 20.90, 23.69, and 26.2 days on D. noxia, L. erysimi, T. and citricida, respectively. These findings were further confirmed from the olfactory experiment where D. noxia proved to be the most preferred prey. This study provides necessary information for mass-rearing of C. sexmaculata.

Effect of Elevated Temperature on the Bionomics of &lt;i&gt;Aenasius arizonensis&lt;/i&gt; Girault

An experiment was conducted to know the effect of thermal stress on the biological attributes of the parasitoid Aenasius arizonensis Girault of the cotton mealybug Phenacoccus solenopsis Tinsley. The results revealed that temperature showed a significant effect on the biological fitness traits of the A. arizonensis; when exposed to 32°C, parasitisation, fecundity, female sex ratio and adult longevity. At 32°C these viz., parasitisation (77%), sex ratio (63.46) and days taken from oviposition to mummy formation (6.4) were found to be the highest. Other fitness traits like fecundity (142.8) and developmental duration (11.2 - males, 12.6 - females) were found to be the highest at 27°C. These parameters gradually decreased with increasing temperature, indicating a negative relationship. Morphometrics of adults revealed that mean length and breadth of mummies, total length and breadth of adult male and females, total width of head, total length of antenna and total hind tibial length were maximum at 27°C as compared to those observed with high temperature treatments. Thus high temperature was observed to have an adverse effect on the growth and development of the parasitoid.

Host‐dependent larval migration and parasitism risk in a polyphagous moth

AbstractFemale herbivorous insects are expected to oviposit on the host plant providing the best performance of the offspring. However, in some insects the larvae are mobile and are not totally dependent on the mother's choice. They can change host plant when conditions for development or exposure to natural enemies vary between individual plants within a patch. Here we study larval migration and preference between two host plants, cotton and alfalfa, in the Egyptian leafworm, Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae). Previous studies have shown that although larval performance is better on cotton, females prefer to oviposit on alfalfa, and this preference corresponds to a higher survival of the eggs. In this study, S. littoralis larvae showed directed movement between host plants and were found to prefer alfalfa over cotton in field test in Egypt, as well as in laboratory selection of feeding site assays. To determine effects by natural enemies, the parasitism rates and various life‐history traits were measured for one larval parasitoid, Microplitis rufiventris Kokujev (Hymenoptera: Braconidae), on several host plants including cotton and clover (equivalent host plant to alfalfa). Overall, parasitism was higher on cotton and parasitoid performance (cocoon mass, adult longevity, and female egg load) was better on cotton compared to clover. This fact suggests an enemy‐free space on clover and alfalfa, as parasitism rate is higher on cotton, and the parasitoid performance is also better on cotton‐fed larvae.

Biology and Morphometry of Gram Pod Borer Helicoverpa armigera Hubner Infesting Gram Cicer arietinum L.

Aims: To investigate the biology and morphometry of gram pod borer Helicoverpa armigera Hubner infesting gram Cicer arietinum L.&#x0D; Place and Duration of Study: The investigation was conducted in the PG Research Laboratory, Department of Entomology, Navsari Agricultural University, Navsari, Gujarat, India under laboratory conditions at 26.7±1.66°C temperature and 51.11±6.35 per cent relative humidity during 2021-22.&#x0D; Methodology: The Helicoverpa armigera was reared from eggs to the adult stage under laboratory conditions. Twenty-five samples of eggs, larval instars, pre-pupa, pupa, and adults were used for morphometrics measurement and fifty samples of each stage were used for determining the biological parameters.&#x0D; Results: The Helicoverpa armigera female laid eggs singly or in batches of 2 to 3 during nighttime. The incubation period was 2.84±0.58 days with 58.39±4.22 per cent hatching. The larvae passed through six different instars having durations, 2.54±0.50, 4.04±0.88, 4.04±0.88, 4.24±0.77, 4.50±0.51, and 4.92±0.80 days of first, second, third, fourth, fifth, and sixth instars, respectively. The mean larval, pre-pupal, pupal, pre-oviposition, oviposition, and post-oviposition periods were 23.12±1.83, 1.64±0.69, 13.40±1.25, 2.60±0.49, 6.94±0.82, and 1.62±0.49 days, respectively. The lengths of egg, first, second, third, fourth, fifth, and sixth instar larvae, prepupa, pupa, and male and female adults, were 0.49±0.05, 1.56±0.12, 4.27±0.38, 8.47±0.70, 13.50±0.95, 21.84±0.97, 32.58±0.99, 25.03±0.97, 19.95±0.96, 17.25±0.56, and 20.32±0.95mm, respectively. Whereas, the breadths were 0.50±0.04, 0.46±0.03, 0.72±0.04, 2.45±0.03, 2.72±0.07, 3.22±0.11, 4.12±0.16, 3.88±0.39, 5.26±0.31, 34.44±1.09, and 39.86±1.03mm, respectively. The lengths of head capsules of first, second, third, fourth, fifth, and sixth instar larvae were 0.23±0.01, 0.45±0.01, 0.63±0.02, 1.12±0.01, 2.19±0.02, and 2.61±0.04, respectively which was not studied before. Whereas, the breadths were 0.26±0.01, 0.50±0.01, 0.73±0.01, 1.28±0.01, 2.22±0.01, and 2.70±0.05, respectively. The sex ratio of male to female was 1:0.76±0.05. The fecundity of gravid females was 544.85±63.89 eggs/female. The adult longevity was 9.04±0.78 and 10.54±0.99 days in males and females, respectively. The total life span was recorded as 47.20±2.57 and 48.70±2.79 days in males and females, respectively&#x0D; Conclusion: The Helicoverpa armigera adults completed their life cycle in 43 to 56 days. The adult longevity was higher in females than males. The males were smaller than the females. The sex ratio was male-biased. The various biological parameters would be useful in the planning of integrated management strategy under field conditions.