Fourth Instars Research Articles

Evaluation of the Efficiency of some Methods in Biological Control of Phlebotomus Papatasi (Diptera:Psychoididae).

The research studies the biological efficiency of the fungus Verticillium lacanii and the alcoholic extract leaves Nerium sp Capparis sp and Lawsonia sp against fourth larval instar and adults of male and female Phlebotomus papatasi. The study was conducted at the laboratory condition at a temperature of 25±2°C, relative humidity. 65 ± 5% and a period of illumination of 12 hours / day . The suspension of Verticillium lacanii at a concentration of 1×810 spores / ml gave the highest mortality 86.74% for the fourth larval instar after 24 hours of treatment, while the suspension of Verticillium lacanii at concentration of 1×810 spores / ml gave the highest mortality of 78.16% for the male Phlebotomus papatasi after after 24 hours of treatment, the suspension of Verticillium lacanii at a concentration of 1 x 810 spores/ml gave the highest mortality rate of 46.75 % for female after 24 treatment. Alcoholic extract of Capparis gave highest mortality 89.57.% for the fourth larval instar, 76.18% for males, and 87.71% for the female Phlebotomus papatasi after 24 hours at concentration 0.07 mg/l . The alcoholic extract of Lawsonia sp showed the lowest mortality was 43.01 % for the fourth larval instar, 29.21% for males, 31.86% for female sand fly Phlebotomus papatasi after 24 hours of treatment at concentration 0.01 mg/l respectively.

Biology and Life Table of Fall Armyworm Spodoptera Frugiperda (J.E. Smith) on Maize at Laboratory Conditions in Nepal

The biology and life table of Spodoptera frugiperda (J.E. Smith) was studied at 27±2 °C temperature and 75±10% relative humidity at a Laboratory in the National Entomology Research Center, Lalitpur, Nepal from June to October, 2021.The main purpose of the study is to determine life cycle and to prepare stage specific life table of the insect on the preferred host maize. The mean incubation, larval and pupal periods were found to be 2.79, 14.04 and 9.49 days, respectively. The adult longevity of male and female moths was recorded at 15.39 days and 16.16 days. Pre-oviposition, oviposition and post-oviposition periods of female moths were 3.27 days, 5.39 days and 6.85 days with the fecundity of 1712 eggs per gravid female. The width of head capsules of the first, second, third, fourth and fifth larval instars was observed to be 0.31 mm, 0.51 mm, 0.81 mm, 1.30 mm and 1.95 mm, respectively. The highest apparent mortality (13.39) and indispensable mortality (10.02) were recorded in the insect’s egg stage. Among larval instars, the maximum apparent mortality (7.1) and indispensable mortality (4.72) were recorded in the first instar.

Larvicidal Activities of Merremia dissecta (Jacquin) Hallier f. and Peltrophorum pterocarpum (DC.) Backer ex k. Heyne Leaves against Aedes aegypti (Diptera: Culicidae)

Aim: Aedes aegypti is the principal vector of Dengue, Chikungunya, Zika. The burden of these diseases is typically highest in tropical and subtropical areas, affecting the most impoverished populations. This laboratory study accessed the larvicidal and pupicidal activities of ethanol, methanol, acetone leaf extracts of Merremia dissecta and Peltrophorum pterocarpum against the Ae. aegypti.
 Study Design: Conventional bioassay.
 Place and Duration of Study: Department of Zoology, Government Arts College, Coimbatore – 641018, Tamil Nadu, India, between July 2021 July 2022.
 Methodology: Larvae and pupae were exposed to various concentrations of plant leaf extracts for 24 hrs. at the laboratory. The probit analyses were used to analyze the data.
 Results: Results revealed that the plant extracts recorded the highest larval mortality at 0.421% and 0.634% ethanol, acetone leaf extracts of M. dissecta; 0.713%. and 0.621% methanol and ethanol leaf extract of P. pterocarpum against fourth instar of Ae. aegypti after 24 hrs.
 Conclusion: The results suggest that this plant extracts can be used as an good larvicidal and pupicide against the dengue and zika virus vector Ae. aegypti.

Impacts of short-term feeding by spotted lanternfly (Lycorma delicatula) on ecophysiology of young hardwood trees in a common garden.

Spotted lanternfly (SLF; Lycorma delicatula White; Hemiptera: Fulgoridae) invaded the US from Asia and was first detected in 2014; currently, populations have established in 14 states primarily in the Northeast and Mid-Atlantic. It feeds voraciously on phloem sap from a broad range of host plants, with a preference for tree of heaven (Ailanthus altissima [Sapindales: Simaroubaceae]), grapevines (Vitis spp. [Vitales: Vitaceae]), and several common hardwood tree species. We evaluated the impacts of fourth instars and adults confined to a single branch or whole trees on gas exchange attributes (carbon assimilation [photosynthetic rate], transpiration and stomatal conductance), selected nutrients, and diameter growth using young saplings of four host tree species planted in a common garden. In general, the effects of adults on trees were greater than nymphs, although there was variation depending on tree species, pest density, and time post-infestation. Nymphs on a single branch of red maple (Acer rubrum [Sapindales: Sapindaceae]), or silver maple (Acer saccharinum [Sapindales: Sapindaceae]) at three densities (0, 15, or 30) had no significant effects on gas exchange. In contrast, 40 adults confined to a single branch of red or silver maple rapidly suppressed gas exchange and reduced nitrogen concentration in leaves; soluble sugars in branch wood were reduced in the fall for silver maple and in the following spring for red maple. Fourth instars confined to whole silver maple trees reduced soluble sugars in leaves and branch wood, and reduced tree diameter growth by >50% during the next growing season. In contrast, fourth instars in whole tree enclosures had no effects on black walnut (Juglans nigra [Fagales: Juglandaceae]). SLF enclosed on tree of heaven at 80 adults per tree suppressed gas exchange after two weeks of feeding, but did not alter non-structural carbohydrates, nitrogen concentrations, or tree growth. Results suggest that moderate to heavy feeding by SLF on young maple saplings may impair tree growth, which could have implications for production nurseries and forest managers.

Phenology and Voltinism of Emerald Ash Borer (Coleoptera: Buprestidae) in Central North Carolina.

The emerald ash borer, Agrilus planipennis Fairmaire (Coleoptera: Buprestidae), has killed millions of ash (Fraxinus spp.) trees across North America. Classical biological control using introductions of parasitoid wasps may provide a sustainable approach to managing this invasive insect. However, the establishment of parasitoids in the southern United States has been difficult. The phenology of emerald ash borer was studied in central North Carolina to inform biological control efforts that better align with the seasonal availability of susceptible emerald ash borer life stages in the warm climate of this region. Biweekly emerald ash borer life stage assessments were conducted in stands of infested green ash (Fraxinus pennsylvanica Marshall, Lamiales: Oleaceae) over 26 consecutive months (June 2019 through August 2021). Adult trapping was also conducted in these stands in the spring and summer of 2019, 2020, and 2021. Based on these collections, emerald ash borer exhibits a univoltine (1-yr) life cycle. Parasitoid-susceptible larvae (third and fourth instars in galleries) are present from late June through October (~1,100-3,000 degree days base 10ºC) and are mostly absent during the remainder of the year. Parasitoid release timings and the life history of selected parasitoid species should be aligned with this window of host availability to be effective. This characterization of emerald ash borer phenology and voltinism will help improve the timing and effectiveness of management efforts as this forest pest continues to spread in southern North America.

Influence of Effective Microorganisms on Some Biological and Biochemical Aspects of Spodoptera littoralis (Boisduval) (Lepidoptera: Noctuidae).

The cotton leafworm, Spodoptera littoralis (Bosid.), is a major pest in African and Asian nations that attacks a wide variety of host plants. This study was conducted to assess the effectiveness of effective microorganisms (EMs) on the biological and physiological features of S. littoralis larvae. Five concentrations (100, 200, 300, 400, and 500 ppm) of EMs were tested. Antifeedant activity, food consumption index, the efficiency of converting digested food, the efficiency of converting ingested food, relative growth rate, and approximate body tissue of the fourth larval instar of S. littoralis were determined. Moreover, carbohydrate enzyme activities (amylase, trehalose, and invertase), total protein, and total lipids of S. littoralis larvae were measured to elucidate the mode of action of the tested agent in the S. littoralis's larval stage. The EMs at 500 ppm had a substantial impact on antifeedant activity, nutritional indices, egg deposit reduction, and hatchability in S. littoralis during the five days. All concentrations interrupted S. littoralis's life cycle and developmental phases. Furthermore, all concentrations were quite useful in lengthening the developmental stages of S. littoralis. In addition, Ems affected the biochemical activities of larvae, leading to disturbances in carbohydrate, lipid, and protein levels. From this study, EMs can be used as a bioinsecticide alternative to traditional insecticides against S. littoralis and may be compatible with integrated pest management approaches.

Vinegaroons (Uropygi: Mastigoproctus tohono) in a multi-predator/multi-prey system: Prey, predators, and cannibalism

Vinegaroons are members of a guild of apex arthropod predators in the high desert grasslands of southeastern Arizona. Despite their importance as major predators in the ecosystem, almost nothing is known about their potential prey, predators, or competitors. We evaluated predator-prey relationships of vinegaroons and 30 species of potential prey, 27 species of potential predators, and the detailed interactions among three taxa of their apex predator guild. With few exceptions, vinegaroons overpowered and preyed on most potential prey within a suitable size range, were almost immune to predation, and appeared to be the dominant species in interactions with other predator guild members. Their most vulnerable life stages were the first two free-living instar stages, whereas adults and fourth instar individuals were not preyed on by any predators active in the same areas and times as vinegaroons. Third instar individuals were a crucial transition stage in which they had a few predators but also were large enough that they required capturing many prey items to grow sufficiently to molt to the fourth instar. In interactions among arthropod predators, the general observation was that when predation occurred, the larger individual usually prevailed irrespective of taxon. Cannibalism among adult and fourth instar vinegaroons does not occur under natural conditions in contrast to when they are placed together in artificial stressful situations. Cannibalism of the three smallest instars appears likely and might partially explain why they are solitary and spend minimal time foraging.

Morphological and physiological changes induced by Achyranthes aspera-mediated silver nanocomposites in Aedes aegypti larvae.

Aedes aegypti is responsible for the global spread of several ailments such as chikungunya, dengue, yellow fever, and Zika. The use of synthetic chemicals is the primary intervention in mosquito management. However, their excessive utilization resulting in the spread of toxic ingredients in the environment and posing threats to beneficial organisms has prompted the recommendation for the use of biologically synthesized nanocomposites as a promising approach for vector control. Silver nanocomposites were synthesized using leaf (AL-AgNCs) and stem (AS-AgNCs) extracts of Achyranthes aspera. The early fourth instars of A. aegypti were exposed to lethal doses of these nanocomposites to evaluate their effects on larval development, behavior, morphology, and mid-gut histoarchitecture. The cellular damage and deposition of nanocomposite residues in the mid-gut were studied using light and transmission electron microscopy. The A. aspera silver nanocomposite (AA-AgNC)-exposed larvae exhibited dose-dependent extended duration of development and diminished adult emergence, but did not exhibit modified behavior. Intense damage to the cuticle membrane and slight contraction in the internal membrane of anal papillae were noticed. Morphologically, the mid-gut appeared disorganized, darkly pigmented, and shrunk. Histological investigations of the mid-gut revealed significantly disordered internal architecture with lysed cells, damaged peritrophic membrane and microvilli, disintegrated epithelial layer, and a ruptured and displaced basement membrane. Visualization of the larval mid-gut through TEM showed severe cellular damage and aggregation of black spots, indicating the deposition of silver particles released by AA-AgNCs. The investigations revealed the bio-efficacy of A. aspera-mediated AgNCs against A. aegypti inducing stomach and contact toxicity in the larvae. The utilization of AA-AgNCs is recommended for A. aegypti management as a safe and effective intervention.

Stage Specific food consumption and utilization by the Mexican beetle, Zygogramma bicolorata Pallister (Coleoptera: Chysomelidae) on Parthenium hysterophorus Linnaeus

The food is the foremost need for the existence of all living organisms and the fluctuations in its availabilitystrongly affects the population dynamics of both the primary and secondary consumers. In the presentstudy we have investigated the effect of food (Parthenium weed) resource fluctuations, in terms of quality,on the feeding attributes of the Parthenium beetle, Zygogramma bicolorata Pallister (Coleoptera: Chrysomelidae).Quantitative food utilization indices were measured in different larval instars and physiological ages ofadult Zygogramma bicolorata Pallister. Among the larval and adult stages of the beetle, third instar larvaeand egg laying females ingested maximum food. Various growth parameters like relative consumptionrate (RCR), relative growth rate (RGR) and approximate digestibility (AD) were relatively higher in thefirst, third and fourth instar and egg laying females. Efficiency of conversion of ingested food (ECI) andefficiency of conversion of digested food (ECD) were maximum in first, third and fourth instar larvae anddecreasing trend was observed in second instar larvae. During pre-oviposition stage adult, these parametersincreased tremendously in contrast to senescent stage. However, the fourth instars had higher feedingattributes than the adult females, proving them to be the better bio-control agents of Parthenium weed thanthe adult females. However, field based studies are still needed to validate the present findings.

Biofabricated selenium nanoparticles mediated from Goniothalamus wightii gains biomedical applications and photocatalytic degrading ability

Selenium nanoparticles (SeNPs) have attracted recently in different biomedical applications due to its unique role of metabolic function prevents cellular damage and other severe disease of human. In this study, biosynthesis of SeNPs from Goniothalamus wightii (Gw-SeNPs) and characterization were performed on UV–vis spectroscopy showed at 265 nm, it was primarily confirmed the biosynthesis of SeNPs. The XRD pattern revealed that peaks at 29.98 (101), 33.22 (111), 47.42 (200), 65.38 (220) and 77.40 (311)) exhibited a highly crystalline structure. The FE-SEM image proved that the formation of Gw-SeNPs which were polygonal shape. Zeta potential and DLS value of SeNPs recorded as −17.6 mV and 20–110 nm. The results described the synthesized SeNPs have good antibacterial potential on both strains of gram-positive as well as gram-negative pathogens. In vitro antioxidant ability of biogenic Gw-SeNPs has been assessed the inhibition of DPPH free radical scavenging ability with IC50 value was reported as 75.62 (µg/mL) and ABTS inhibitory concentration at 50% was 74.12 (µg/mL). The present findings provide important evidence on cytotoxic effects of Gw-SeNPs on MCF-7 cells. Dye degradation ability of Gw-SeNPs against reactive dyes over the 97% in 150 min in methylene blue dye degradation, the experiment was done under the direct sunlight. Finally, the larvicidal activity against fourth instars mosquito larvae was also executed. In this study, the data indicate that biosynthesis of Gw-SeNPs strongly performed a significant and multifunctional role in biomedical and environmental field.

Candidate chemosensory receptors in the antennae and maxillae of Spodoptera frugiperda (J. E. Smith) larvae.

Although most of the damage caused by lepidopteran insects to plants is caused by the larval stage, chemosensory systems have been investigated much more frequently for lepidopteran adults than for larvae. The fall armyworm Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) is a polyphagous and worldwide pest. To understand the larval chemosensory system in S. frugiperda, we sequenced and assembled the antennae and maxillae transcriptome of larvae in the sixth instar (larval a-m) using the Illumina platform. A total of 30 putative chemosensory receptor genes were identified, and these receptors included 11 odorant receptors (ORs), 4 gustatory receptors (GRs), and 15 ionotropic receptors/ionotropic glutamate receptors (IRs/iGluRs). Phylogeny tests with the candidate receptors and homologs from other insect species revealed some specific genes, including a fructose receptor, a pheromone receptor, IR co-receptors, CO2 receptors, and the OR co-receptor. Comparison of the expression of annotated genes between S. frugiperda adults and larvae (larval a-m) using RT-qPCR showed that most of the annotated OR and GR genes were predominantly expressed in the adult stage, but that 2 ORs and 1 GR were highly expressed in both the adult antennae and the larval a-m. Although most of the tested IR/iGluR genes were mainly expressed in adult antennae, transcripts of 3 iGluRs were significantly more abundant in the larval a-m than in the adult antennae of both sexes. Comparison of the expression levels of larval a-m expressed chemosensory receptors among the first, fourth, and sixth instars revealed that the expression of some of the genes varied significantly among different larval stages. These results increase our understanding of the chemosensory systems of S. frugiperda larvae and provide a basis for future functional studies aimed at the development of novel strategies to manage this pest.

Shift of Host Range for the Immature Stages of the Lanternfly, Pyrops watanabei (Matsumura) (Hemiptera, Fulgoridae) Native to Taiwan.

Simple SummaryPyrops watanabei is a lanternfly species native to Taiwan, and the adults are frequently on Triadica sebifera in summer. Compared to adult longevity, the developmental duration of immature stages from eggs to adult emergence is much longer. Although few records exist, the plants preferred by the immature stages had not been determined prior to this study. Thus, a one-year investigation was conducted to verify the oviposition site preference, determine the plants preferred by nymphs, and examine the change of host ranges with time and development. We establish that Heptapleurum heptaphyllum is not only the preferred egg-laying site, but the main host plant for nymphs from September to the next April, according to our investigations in northern Taiwan. Moreover, the preferred host plant for the nymphs shifts to Triadica sebifera from May onwards to adult emergence. Although Pyrops watanabei is a species native to Taiwan, many fundamental aspects of the species are still poorly documented. Populations of the lanternfly in locations of northern Taiwan were found in abundance and were suitable for the conduction of an investigation from 1 July 2021 to 30 June 2022. We established the shift in the main host plants with different developmental stages. The occurrence of immature individuals on Heptapleurum heptaphyllum increased with age from eggs to nymphs in the third instar; however, it declined from the fourth instar onwards due to a shift in preference to Triadica sebifera. In 2021, the earliest detection of an egg mass was on 1 July. More eggs were recorded in August, and some could be found in September and October of the same year. In 2022, we found an egg mass on 28 June. In August 2021, nymphs in the first and second instars were detected. Then, nymphs in the third and fourth instars appeared after September and October 2021, respectively. Furthermore, nymphs in the fifth instar were sighted as late as March 2022. Finally, this study will provide a basis for further evaluation of the impact of invasion of Pyrops candelaria on the ecology of Pyrops watanabei.

Impact of egg-quality and its laying pattern on the fate of egg-cannibalism and intraguild predation in ladybirds

We investigated the impact of egg-quality and its laying pattern on the incidence of cannibalism and intraguild predation in ladybirds. We manipulated quality by using two species of ladybirds’ eggs and the pattern of egg-laying by arranging the eggs singly or in cluster and using second, third and fourth instar larva of two ladybird species, Coccinella septempunctata L. and Menochilus sexmaculatus (Fabricius), as predators. We found that second instars of both ladybird species indulged in egg-cannibalism, whereas third and fourth instars were potential intraguild predators and consumed heterospecific eggs. On the other hand, linearly arranged and clustered eggs of M. sexmaculatus were least protected by higher instars of C. septempunctata, while clustered eggs of C. septempunctata got a refuge from M. sexmaculatus higher stage larvae due to aposematism in eggs. It is concluded that C. septempunctata was an intraguild predator of eggs of M. sexmaculatus in starved conditions, and the egg-quality and pattern of egg-laying can affect the fate of egg-cannibalism and intraguild predation.

Evaluation of mosquitocidal potency of leaves and fruits extracts of Phyllanthus acidus L. against filarial vector Culex quinquefasciatus Say

The present piece of work was done to carry out larvicidal, pupicidal, adulticidal, and repellent activities of crude extracts of mature leaf and fruit extract of Phyllanthus acidus against filarial vector Culex quinquefasciatus. The percentage mortality of 1st instar stages of Cx. quinquefasciatus at 0.7% concentration was considerably higher (p < 0.05), followed by second, third and fourth instars larvae. Whereas crude extract of fruits showed 100% mortality at 0.9% concentration in case of first instar larvae of Cx. quinquefasciatus after 24 h of contact. The lowest LC50 value observed was 0.26 ml and 0.34 ml against the first instar larval stages of Cx. quinquefasciatus after exposure of 24 hours in crude leaf and fruit extract of P. acidus, respectively. In pupicidal bioassay, the crude leaves extract of P. acidus exhibited pupicidal potency with LC50 values of 7.463% after 24 h. The extract from fresh leaves of P. acidus revealed repellency against the mature females of Cx. quinquefasciatus with 94% protection. In adulticidal activity, after 24 h of exposure there is 93.3% death of adult mosquitoes of Cx. quinquefasciatus observed. ANOVA (three-way factorial) was done for both the crude extracts of plant parts and it showed a substantial variance in larval mortality (p

Larvicidal activities of ethanolic extracts of Hyptis suaveolens Linn (Lamiaceae) and Azadirachta indica (Meliaceae) leaves and their phytochemical properties in malaria vector control in Dogbo district in South-western Benin, West Africa

The use of chemical insecticides causes important damages to environment and human health and there is a need to search for alternative solutions. This study aims to investigate on phytochemical properties of Hyptis suaveolens Linn (Lamiaceae) and Azadirachta indica (Meliaceae) leaves and to evaluate their larvicidal activities in the malaria vector control in couffo department in south-western Republic of Benin. Larvae of Anopheles gambiae s.l mosquitoes were collected from breeding sites using the dipping method from April to July 2022 during the great rainy season in Dogbo district. A batch of twenty (20) larvae of fourth instar were exposed to ethanolic extracts of Hyptis suaveolens Linn and Azadirachta indica leaves with different concentrations of 1 mg/liter, 2mg/liter, 3 mg/liter, 4 mg/liter and 5 mg/liter in some glass jars or plastic test cups of same dimensions covered with small cutting untreated net and in some control jars containing no trace of these ethanolic extracts. Larval mortality was recorded after 24 hours, 48 hours and 72hours exposure. The results showed that the optimal concentration of ethanolic extract of Hyptis suaveolens Linn which kills 100% of Anopheles gambiae s.l. larvae was 4 mg/liter whereas the optimal concentration of ethanolic extract of Azadirachta indica which kills 100% of Anopheles gambiae s.l. larvae was 2 mg/liter. Hyptis suaveolens Linn and Azadirachta indica leaves possess some phytochemical properties with larvicidal activities on larvae of Anopheles gambiae sensu lato.

Batkoa major infecting the invasive planthopper Lycorma delicatula

The entomopathogenic fungi Batkoa major and Beauveria bassiana caused co-epizootics in populations of invasive spotted lanternflies, Lycorma delicatula, in 2018 in northeastern North America. Although first described from North America in 1888, the biology and ecology of Batkoa major had not been studied since that time. This entomophthoralean fungus found infecting L. delicatula in 2018 produces conidia and rhizoids similar in appearance to the original description. We conducted laboratory bioassays to investigate infection of different ages and sexes of these planthoppers, inoculating via showered conidia. All nymphs, and male and female adults were susceptible, dying in 4.3-6.7 days. Adult males died more quickly than adult females or fourth instars. Batkoa major grew out of cadavers of adult males more frequently than adult females or fourth instar nymphs. Rhizoids that provide attachment of cadavers to substrates were produced from adult cadavers more frequently than conidia. Resting spores were not observed in vivo or in vitro in the lab, or in the field.

Efficacy of Rauvolfia tetraphylla Leaf extracts against the Vector of Lymphatic Filariasis Culex quinquefasciatus

The Rauvolfia tetraphylla leaf extract with different solvents n-hexane, chloroform, acetone and methanolwere tested for larvicidal, ovicidal, oviposition attractant/deterrent activities. Their effect on larval nutritionalreserve against Culex quinquefasciatus was also studied. Larval mortality was observed after 24 hoursexposure. The LC50 values for n-hexane, chloroform, acetone, methanol extracts are 16.80, 91.56, 214.85,44.68 ppm, respectively. The mean percentage hatchability of the ovicidal activity was observed 48 hourspost treatment. For R. tetraphylla, methanolic extract exhibited 56 % egg hatchability at 125 ppm. The effectiveoviposition repellency was 100 % at 320 ppm and the oviposition activity index value -1 was shown by nhexaneextract of R. tetraphylla. The fourth instar of C. quinquefasciatuswhere exposed to LC50 concentrationof extracts and its on larval nutritional reserves was checked. All extracts showed moderate effect on larvalnutritional reserves, i.e. changes in total concentration of sugar, glycogen, lipid and protein. The averagevalues of total sugar, glycogen, lipid and protein are 9.47, 32.32, 54.50, 183.35 μg/larvae was found infourth instar larvae of C. quinquefasciatus. From the all-leaf extracts, the methanol extract affects the totalsugar, lipid; n-hexane extract to glycogen and acetone extract to protein of fourth instar larvae of the mosquitoand decreases up to 3.39, 20.71, 11.18, 91.05 μg/larvae, respectively. These results reveal that the R. tetraphyllaleaf extracts have the control potential against C. quinquefasciatus.

Feeding behaviour of Coccinella septempunctata and Coccinella transversalis

The mass production of coccinellids at the Biocontrol Laboratory of Chandra Shekhar Azad University of Agriculture and Technology, Kanpur included laboratory studies on the predatory behaviour of Coccinella septempunctata L. and C. transversalis (f.) (Coleoptera: Coccinellidae). The study was done with the natural food, Lipaphis erysimi and Brevicoryne brassicae (Hemiptera: Aphididae). The predatory efficiency of the larvae and adults was determined by quantitative method of aphids consumed. The results revealed that the feeding rate increased gradually from the first to fourth larval instar, irrespective of the aphid host, with the first instars being less voracious than later ones.

Gut Endosymbiont Disruption through Antibiotics Influences the Metabolic Homeostasis in Spodoptera frugiperda (Lepidoptera: Noctuidae) Larvae

Fall armyworm as a polyphagous voracious feeder reported causing yield losses in most agriculturally important crops. As this insect had developed resistance against most of the insecticides, there is a need for an alternate approach to management. Gut endosymbiotic bacteria play a significant role in host feeding, digestion, and defense response throughout the life stages of insects. In the present study, we have isolated and identified the gut endosymbiotic bacteria of fall armyworm and the larvae were treated with antibiotics. The results showed that the maximum bacterial population was observed in the fourth instar of field-caught larvae and the least population was observed in the fourth instar artificially reared population. Based on the biochemical results the isolated gut endosymbiotic bacteria mainly comprised of Bacillus sp, Enterococcus sp., and Enterobacter sp. Based on the susceptibility of gut bacteria to different antibiotics, 6 antibiotic treatments with one insecticide treatment were administered to an artificial diet reared with third instar larvae and their dietary indices were evaluated. Among the antibiotic treatment, there was a reduction in the dietary indices in the larvae treated with Ciprofloxacin CIP5 (45.33%) and Cefotaxime CTX30 (41.73%) and an increase in dietary indices in the larvae treated with Nalidixin NA30 (31.58%), Doxycycline DO30 (8.82%), Vancomycin VA30 (22.05). Elimination of gut bacteria with a suitable antibiotic will affect the insect’s feeding and dietary indices subsequently decreasing the relative growth rate and insect’s physiology. Hence, gut bacteria-based green control measures might be used as an alternative approach for insecticides for the effective management of fall armyworm.

Properties of nucleopolyhedrovirus occlusion bodies from living and virus-killed larvae of Spodoptera frugiperda (Lepidoptera: Noctuidae)

Previous studies report that the pathogenicity of nucleopolyhedrovirus occlusion bodies (OBs) is reduced if OBs are collected from living infected insects compared to virus-killed insects. We compared the production and characteristics of SfMNPV OBs collected from living and virus-killed fourth instars of Spodoptera frugiperda at 3–4 days, 5 days and 6–7 days post-inoculation. Cumulative virus-induced mortality increased from 10.5 % at 3 days to 99.6 % at 7 days post-inoculation. The production of OBs/mg larval weight increased significantly between the first and second samples, but did not increase thereafter. The total number of OBs produced in living and virus-killed larvae increased at each sample time. The size (cross-sectional area) of OBs increased significantly during the experiment, probably due to OB maturation. The median prevalence of immature OBs decreased over time from 25 to 44 % in the first samples to 9 % in the final sample. OB pathogenicity was compared in second instars that consumed a discriminating concentration of inoculum (2 × 104 OB/ml). Virus-induced mortality increased markedly in larvae that consumed OBs collected later (6–7 days) compared to OBs from earlier samples, but was similar for OBs from living or virus-killed insects at each time point. We conclude that the pathogenicity of OB samples was sensitive to the prevalence of immature OBs rather than the viral genome content of OBs, which did not differ over sample times or in OBs from living or virus-killed insects. These findings can inform decisions on the production of biological insecticides and laboratory studies on the insecticidal properties of OBs.