1st Instars Research Articles

Studies on biology of mango leaf webber Orthaga exvinacea (Hampson)

The laboratory studies on biology of mango leaf webber was conducted at the Department of Entomology, College of Horticulture, Bagalkot during 2018-19. The studies revealed that the mean preoviposition, oviposition and postoviposition periods lasted for 2.60±0.52, 4.10±0.74 and 1.90±0.74 days, respectively. The larva moulted six times by passing through seven larval instars. The mean durations of 1st, 2nd, 3rd, 4th, 5th, 6th and 7th instar were 4.80±0.92, 4.65±0.90, 4.41±0.63, 4.16±0.87, 4.52±0.51, 5.20±0.42 and 6.50±0.53 days, respectively with mean total larval period of 42.54±2.53 days. The mean duration of male and female pupal stage were 11.80±0.63 days and 14.30±1.43 days respectively. The mean longevity of adult male and female were 4.10±0.74 days and 5.80±0.42 days, respectively. The total life cycle completed in 58.44±3.90days in male and 62.64±4.59 days in female.

Energy reserves in Brevicoryne brassicae (Lin.) (Homoptera: Aphididae) instars and their effect on predation and longevity of three coccinellid species under laboratory conditions

BackgroundContents of carbohydrates, protein, and lipids in tissues of insect prey constitute the required energy reserve utilized by their predators. Their amounts define the preference of the predator to certain prey on which its biological performance is the optimum. Feeding preferences and longevity of the 3 coccinellid beetles; Coccinella septempunctata L., C. undecimpunctata L., and Scymnus interruptus L. were studied in relation to energy reserve in tissues of the cabbage aphid, Brevicoryne brassicae (Lin.).Main bodyThe level of energy reserve increased with increasing of aphid nymphal instars showing the highest in 4th instar (0.10844 cal/mg). Lipids and carbohydrates represented the highest energy reserve average rate in B. brassicae adults (0.29139 and 0.07404 cal/mg), respectively. C. septempunctata larval stage recorded the highest efficiency in daily predation (89.42 prey), when fed on 1st instar nymphs of the aphid. It required 21 days when fed on the 3rd nymphal instar of B. brassicae. S. interruptus larval stage reflected the lowest consumption and longevity in predation where it consumed less than 69.25 prey/day and lasted a period less than 17.5 days. Generation time for C. undecimpunctata lasted the longest (20.89 days) when fed on B. brassicae 1st nymphal instar. It was decreased in S. interruptus recording (12.22 days) when fed on B. brassicae 3rd nymphal instar.ConclusionOnly C. septempunctata was efficient in predation and its biological performance was the best compared to the other tested coccinellid species. Use of C. septempunctata can be recommended when applying biological control programs in the field against the cabbage aphid.

Influence of Aquatain™, a monomolecular surface film on surface tension for controlling the filarial vector Culex pipiens (Diptera: Culicidae)

Surface tension is a phenomenon in the liquid media and plays an important part in the development and survival of aquatic animals. Influence of Aquatain™ monomolecular film on surface tension was determined against mosquito larvae and pupae at different temperatures (10, 15, 20, 25, 30 and 35 °C) and Aquatain™ doses (0.5, 1.0 and 2.0 ml/m2). In the laboratory, Aquatain™ showed larvicidal and pupicidal effects against the filarial vector Culex pipiens. Higher mortality was observed in late and more weighted instars/stages than young ones as well as in the pupal stage. The pupal mortality reached 76.2%, 86% and 93.3% after 12 h post-treatment at 0.5, 1.0 and 2.0 ml/m2, respectively, and it was completely eliminated (100%) within 24 h compared to 15.1%, 26.9% and 38.2% for 1st larval instar, respectively. Also, results showed at 0.5 ml/m2 with temperature range: 10, 15, 20, 25, 30 and 35 °C, the mortality reached 4.0, 6.7, 10.8, 17.3, 22.7, 29.3% and 32, 44, 54, 72, 84, 97.3% for 1st and 4th larval instar, respectively, where the surface tension (γ) was 65.6, 62.4, 58.0, 57.0, 54.2 and, 49.6 dyn/cm, while the Aquatain™ was more effective on mosquito larvae and pupae at high doses with the temperature range. On the other hand, without Aquatain™ dose, the mortality value ranged between 0.0 - 1.2%, and the surface tension (γ) was 74.5 dyne/cm, which is considered as an accidental death. Aquatain™ was effective against all aquatic phases of mosquitoes, especially against the last and weighted ones. Not only was the efficacy of Aquatain™ increased by increasing the dose, but it also increased with the increased temperature of the environment. This efficiency of Aquatain™ is due to its ability to reduce the surface tension of the water medium, preventing different stages of mosquitoes from reaching the surface for breathing thereby leading to suffocation and death. Therefore, we recommended Aquatain™ in programmes for mosquito control and other aquatic insects as a safe, cost-effective control agent.

Cuticular hydrocarbons as a tool for determining the age of Chrysomya rufifacies (Diptera: Calliphoridae) larvae.

Calliphoridae are one of the most important insect groups encountered as evidence collected from a crime scene. Age determination of the immature stages of these necrophagous flies is an important step toward estimating the time of colonization and inferring a minimum postmortem interval (PMImin ) in most instances. To determine if the cuticular hydrocarbons could be used to establish whether the development stages yield characteristics profiles, allowing for age estimation, hydrocarbons were extracted from 1st and 2nd, as well as feeding and post-feeding 3rd instar Chrysomya rufifacies, the hairy maggot blow fly. Extracted hydrocarbons were analyzed using gas chromatography coupled to mass spectrometry with the aim to investigate the changes in chemical profiles of each larval stage. A total of 23 compounds were identified with most of them being alkanes (65%) with carbon chain lengths of 9-33 carbons, alkenes (18%), and methyl-branched alkanes (17%). All the hydrocarbons except pentadecane (C15), hexadecane (C16), and nonacosane (C29) showed significant differences in their expression throughout larval development. For 1st instars, nonane was the most abundant (17% of the total hydrocarbons content) compound. Accounting for 11% and 10% of the cuticular hydrocarbons, tricosane and pentacosane, respectively, were the notable hydrocarbons in 2nd instars. For post-feeding 3rd instars, hentriacontane and tritriacontane were present with relative abundances 18% and 15%, respectively. On average, there was a shift from low to high molecular weight hydrocarbons as the larvae aged. These results indicate the change in hydrocarbons makeup as larvae age and could potentially be used to determine the age of immature C.rufifacies and hence aid in PMImin estimations. However, future research is needed to validate these results under natural conditions in the field.

Performance of the parasitoid species Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday)\xa0(Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae), using Myzus persicae (Sulzer) (Hemiptera: Aphididae) as host

Three parasitoid species viz. Aphelinus asychis Walker (Hymenoptera: Aphelinidae), Aphidius ervi (Haliday) (Hymenoptera: Braconidae) and Diaeretiella rapae (McIntosh) (Hymenoptera: Braconidae) parasitizing the aphid species Myzus persicae (Sulzer) (Hemiptera: Aphididae) in mid-hills of north India were studied. At different locations and times of the year, the parasitization by A. asychis, A. ervi, and D. rapae ranged from 7.53 to 37.58, 4.26 to 80.45, and 74.25 to 80.48%, respectively. All the 3 parasitoids successfully completed their development on different nymphal instars of the aphid host and the total developmental duration of A. asychis, A. ervi, and D. rapae ranged 10.4–14.6, 24.2–29.6, and 10.2–15.2 days, respectively. It was significantly longer on the 1st nymphal instar of the host. The longevity of the female parasitoids was significantly longer than their counterparts. Differences in host age significantly influenced the longevity of female parasitoids and it was more on 1 to 2-day-old nymphs than that on 4 to 5-day-old nymphs. Fecundity and ovipositional periods of the parasitoids on younger (1–2 days old) host age group were considerably prolonged than on the older ages of the aphid. Average total fecundity of A. asychis and D. rapae was significantly higher when parasitizing 1–2-day-old nymphs. In A. asychis, host feeding behavior was also observed by a total host feeding of 89.2 aphids (1–2 days old) and 43.4 aphids (4–5 days old) during its life span. It is concluded that A. asychis, A. ervi, and D. rapae can be mass reared using M. persicae as host and can be utilized successfully in augmentative biological control program.

Comparative toxicity of certain insecticides against Chrysoperla Spp. (Neuroptera: chrysopidae) under laboratory conditions

Toxicity of newer insecticides viz., chlorantraniliprole 18.5 SC, flubendiamide 20 WG, buprofezin 25 SC, lambda cyhalothrin 9.5 + thiamethoxam 12.6 ZC, lambda cyhalothrin 5 EC, azadirachtin 5 w/w, thiamethoxam 25 WG, thiachloprid 21.7 SC were tested against different larval stages of Chrysoperla spp. under laboratory conditions. The observations on percent mortality of 1st, 2nd and 3rd instar of C. spp. larvae were recorded after 24, 48 and 72 hrs of application. The results showed that lambda cyhalothrin + thiamethoxam was found toxic to all instars of Chrysopa larvae whereas azadirachtin was found safest insecticide against all instar of Chrysopa larvae at all treatment intervals. Considering ecofreindliness, it can be concluded that insecticides azadirachtin, buprofezin and flubendiamide were found most safer to all instars of C. spp. which can be taken successfully in the IPM programmes whereas, lambda cyhalothrin + thiamethoxam was found most harmful to all instars of larvae.

Biology, predatory potential and functional response of Mallada desjardinsi (Navas) on melon aphid, Aphis gossypii glover

This study evaluated the developmental biology, predatory potential, and functional response of Mallada desjardinsi (Neuroptera:Chrysopidae) larval instars fed on melon aphid, Aphis gossypii Glover. The experiment was carried out under laboratory conditions at 25 ± 1 °C, with 70 ± 5% R.H and 12:12 L:D photoperiod. The freshly emerged larvae were reared individually in the Petri plates containing moist blotting paper and cucumber leaves (6 × 6 cm) infested with assorted population of second and third instars of A. gossypii. The results showed that incubation, total larval, pre pupal and pupal periods of M. desjardinsi were 2.90, 12.50, 1.40 and 9.10 days, respectively. Pre oviposition, oviposition and post oviposition period of M. desjardinsi was 11.80, 32.40 and 2.76 days, respectively and each female laid an average of 128.58 eggs. The 1st, 2nd and 3rd instars of M. desjardinsi on an average consumed 30.98, 107.80 and 265.40 aphids, whereas total consumption during life cycle was 298.50 aphids/predator. All the three larval stages of the predator exhibited Type II functional response to the aphid. Based on Rogers’s random predator equation, the predator’s attack rate was the lowest (0.092) in the first instar, while the 3rd instar recorded the highest rate (0.118). Functional response parameters indicate that attack rate increased and handling time decreased with the advancement of the predator stage. From biological control point of view, our data suggest the successful use of M. desjardinsi third instar larvae as voracious feeders in IPM programmes against melon aphid.

Effect of gamma irradiation and subsequent cold storage on the development and predatory potential of seven spotted ladybird beetle Coccinella septempunctata Linnaeus (Coleoptera; Coccinellidae) larvae

Seven spot ladybird beetle, (Coccinella septempunctata) is a widely distributed natural enemy of soft-bodied insect pests especially aphids worldwide. Both the adult and larvae of this coccinellid beetle are voracious feeders and serve as a commercially available biological control agent around the globe. Different techniques are adopted to enhance the mass rearing and storage of this natural enemy by taking advantage of its natural ability to withstand under extremely low temperatures and entering diapause under unfavorable low temperature conditions. The key objective of this study was to develop a cost effective technique for enhancing the storage life and predatory potential of the larvae of C. septempunctata through cold storage in conjunction with the use of nuclear techniques, gamma radiations. Results showed that the host eating potential of larvae was enhanced as the cold storage duration was increased. Gamma irradiation further enhanced the feeding potential of larvae that were kept under cold storage. Different irradiation doses also affected the development time of C. septempuntata larvae significantly. Without cold storage, the lower radiation doses (10 and 25 GY) prolonged the developmental time as compared to un-irradiated larvae. Furthermore, the higher dose of radiation (50GY) increased the developmental time after removal from cold storage. This study first time paves the way to use radiation in conjunction with cold storage as an effective technique in implementation of different biological control approaches as a part of any IPM programs

Oral delivery of dsHvlwr is a feasible method for managing the pest Henosepilachna vigintioctopunctata (Coleoptera: Coccinellidae).

RNA interference (RNAi) techniques have emerged as powerful tools that facilitate development of novel management strategies for insect pests, such as Henosepilachna vigintioctopunctata (Coleoptera: Coccinellidae), which is a major pest of solanaceous plants in Asia. In this study, the potential of oral delivery of in vitro-synthesized and bacterially expressed double-stranded H. vigintioctopunctata lesswright (lwr) gene (dsHvlwr) to manage of H. vigintioctopunctata was investigated. Our results showed that the gene Hvlwr had a 480-bp open reading frame and encoded a 160-amino acid protein. Hvlwr expression levels were greater in the fat body than other tissue types. Hvlwr silencing led to greater H. vigintioctopunctata mortality rates and appeared to be time- and partially dose-dependent, likely as a result of the number of hemocytes increasing with dsRNA concentration, but decreasing with time. Bacterially expressed dsHvlwr that was applied to leaf discs caused 88%, 66%, and 36% mortality in 1st instars, 3rd instars, and adults after 10, 10, and 14 d, respectively; when applied to living plants, there was greater mortality in 1st and 3rd instars, but there was no effect on adults. Furthermore, dsHvlwr led to improved plant protection against H. vigintioctopunctata. Our study shows an effective dietary RNAi response in H. vigintioctopunctata and that Hvlwr is a promising RNAi target gene for control of this pest species.

Effect of Water Temperature on Survival, Growth and Molting Cycle During Early Crablet Instar of Mud Crab, Scylla paramamosain (Estampador, 1950)

This study aimed to determine the effect of rearing water temperature on survival, growth and molting cycle of the mud crab, S. paramamosain from Megalopa up to 1st crablet instar (Crablet 1) and from Crablet 1 to 2nd crablet instar (Crablet 2). Different water temperature regimes were implemented i.e. 20 °C, 24 °C, 28 °C, 32 °C, 36 °C and ambient temperature. The observed parameters were: successful molting from Megalopa to Crablet 1 and from Crablet 1 to Crablet 2, survival in Crablet 1 and Crablet 2, growth (carapace increment of crablets), Specific Growth Rate of carapace width (SGRCW) and, molting interval (in days) from Megalopa to Crablet 1 and from Crablet 1 to Crablet 2. The results showed that the highest survival rate from Megalopa to Crablet 1 was found at 24 and 28 °C where both could reach up to 100%. At water temperature of 32 °C and ambient temperature, the survival rate were 96.66%. The lowest survival rate was found at 20 °C and 36 °C treatments (p 0.05), but there were significant differences in molting intervals (p < 0.05) for both Megalopa to Crablet 1 and Crablet 1 to Crablet 2 phases. Treatment of ambient temperature (27–30 °C) had the fastest molting interval from Megalopa to Crablet 1 but its value not significantly different with treatment of 24, 28 and 32 °C. The fastest molting interval from Crablet 1 to Crablet 2 was found at 32 °C which was 2.96 days (p < 0.01). Based on this study, it is recommended that rearing from Megalopa to Crablet 1 should take place at a temperature of 28 °C while, in Crablet 1 to Crablet 2 phase, a temperature of 28 to 32 °C is recommended.

Impacts and evaluation of Hormoligosis of some insect growth regulators on Phenacoccus solenopsis (Hemiptera: Pseudococcidae)

Insects when exposed to sublethal applications of pesticides exhibit hormoligosis in their various biological activities. The present research was conducted to evaluate the hormoligosis impacts of IGR’s pesticides including pyriproxyfen (Priority 10.8 EC) and lufenuron (Ardent 5 EC) on cotton mealybug in laboratory conditions at IPM Laboratory, Department of Entomology University of Agriculture. The results revealed that concentration-dependent mortality in cotton mealybug of 1st instars and adults was observed that decrease after generations at sub-lethal dilutions of Priority ® and Ardent ® pesticide which retained development of resistance from G1 to G2. Maximum hormoligosis revealed at 3 days post treatments interval (PAI) Priority ® in fecundity at LC10 (0.07%) in G5 (63.17 crawlers/female) and at 7 days Priority ® in G5 (68.13 crawlers/female). At 7 days lufenuron of sub-lethal concentration of LC10 (0.01%) in G5 (73.18). At 3rd and 7th days post treatments interval Priority® and Ardent® demonstrated maximum hormoligosis in longevity at LC10 (0.07%) in G5 (57.29, 57.14 days), (54.07, 58.10 days) respectively, and hormoligosis of sex ratio was not determined against Priority® and Ardent®. We conclude that hormoligosis development is fast at sub-lethal dilutions of Ardent and Priority® at LC10, LC20 and LC30 with respect to mortality, fecundity, and longevity. While hormoligosis development was fast at sub-lethal dilutions of priority® and ardent® at LC30, LC40 and LC50 with respect to the mortality of adult female. In Pakistan, pesticide resistance in cotton mealybug can be achieved if the effective and different pesticides are used along with other Integrated Pest Management techniques in rotation and at the early stage of resistance improvement.

Efficacy of entomopathogenic nematodes against the cabbage butterfly (Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage under field conditions

Experiments were conducted to test the pathogenicity of entomopathogenic nematode, Heterorhabditis pakistanensis alone and in combination with the chemical insecticides, viz., Dichlorvos and Quinalphos and Neem product, viz., Azadirachtin against the cabbage butterfly, Pieris brassicae (L.) (Lepidoptera: Pieridae) infesting cabbage plants under laboratory and field conditions. In laboratory test, inoculum level of 200 infective juveniles (IJs) was most effective causing mortality to both 3rd and 4th instars larvae at 48 h. Nematode multiplication rate in insect cadaver was inversely proportional to the size of initial inoculum level of IJs, whereas IJs yield was directly proportional to the size of larva. The 4th instar larva resulted in a highest yield of IJs, followed by 3rd, 2nd, and 1st instars larvae at all the inoculum levels used in the study. IJs were found compatible with the chemical insecticides and Neem product at lower than half of the optimum single dose. The cumulative mean survival percentage of IJs recorded the highest (77.5%) in the combination of 100 IJs + Azadirachtin (0.25%) and lowest (70.6%) in 100 IJs + Dichlorvos 76 EC (0.05%). Under field conditions, H. pakistanensis (3.0 lakh IJs/m2) + Dichlorvos 76 EC (0.025%) resulted to the highest larval mortality (79.65%), followed by H. pakistanensis (3.0 lakh IJs/m2) + Azadirachtin (0.25%), where it was 76.22%. The larval mortality was the least (61.16%) in case of H. pakistanensis (3.0 lakh IJs/m2) when applied alone. H. pakistanensis + Dichlorvos resulted to the highest increase (31.42%) in cabbage yield over untreated control.

The Potency of Collecting Larvae of Oryctes rhinoceros L. (Coleoptera:Scarabaeidae) in the Oil Palm Plantation

The intensive and continuous collection of rhinoceros beetles, Oryctes rhinoceros L. (Coleoptera: Scarabaeidae), is an extraordinary strategy in IPM (Integrated Pest Management). This study was intended to evaluate the potency of people in collecting larvae and to determine the age structure of the beetle population. The study was conducted in Asahan Regency, North Sumatera Province. Adult men, adult women, adolescent girls, and adolescent boys collected beetles for 2 hours in each breeding site. Results showed that the beetle was more significant abundant in decomposed trunks at plots of immature and mature palms than at heaps of the empty fruit bunches namely 236, 221 and 93 individuals/2 hours. The population age-structure showed significantly predominant of 2nd and 3rd instars in all breeding sites, i.e. eggs, 1st instars, 2nd instars, and 3rd instars, pupae, adult males, and adult females were 2.02, 23.29, 21.39, 47.06, 3.17, 0.86, and 2.21%, respectively. Adult men, adult women, and adolescent boys had similar potency in collecting 3rd instar larvae while the least amount was collected by the adolescent girls viz. 70, 85, 60, and 38 larvae/2 hours, respectively. It is suggested that the study results support future efforts in the sustainable control of rhinoceros beetle through collecting larvae for commercial utilization.

Asymmetric intraguild predation of Harmonia axyridis (Pallas, 1773) (Coleoptera: Coccinellidae) on a native Coccinellidae guild

Abstract Harmonia axyridis is an exotic species that can cause serious impacts on native biodiversity in areas where it is introduced to act as a biological control agent. This predator is often involved with intraguild predation, in most cases with aphids predators. Here, we report the results of experiments designed to understand the outcome of the invasion of H. axyridis on native coccinellid aphidophagous guilds using intraguild predation as a theoretical framework. Tests were conducted to determine the interactions between 1st and 4th instars larvae and H. axyridis adults, with Cycloneda sanguinea, Cycloneda pulchella, Eriopis connexa and Hippodamia convergens larvae, as well as eggs predation rate. Two treatments were used: absence and presence of food, Cinara atlantica. The results showed that 1st and 4th instars larvae and H. axyridis adults are able to prey on larvae and eggs of four Coccinellidae species analyzed, and also their own eggs, showing that this exotic species is a dominant predator in this guild of aphidophagous coccinellids. Adding to these results, studies are recommended, especially the monitoring of these species in the field in the long run, reporting their abundance and diversity as well as their behavior and impact within aphidophagous guilds, especially in Coccinellidae species.

Biology of Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae) on eggplant and tomato

The study mainly focussed on monitoring different life stages viz., egg, nymphal instars, pupae and adults. The present investigation revealed that mean pre-oviposition, oviposition and post oviposition period were 1.50 and 3.70; 3.50 and 4.50 and 1.60 and 3.30 days on eggplant & tomato, respectively. Further, three nymphal instars were observed in the life history of B. tabaci with average duration of 3.50 and 5.70, 2.40 and 4.80 and 3.50 and 5.40 days for 1st, 2nd and 3rd instars on eggplant & tomato, respectively. The total mean nymphal period on eggplant and tomato was observed as 9.40 and 15.90 days respectively. In addition, the mean pupal period and adult longevity of B. tabaci on eggplant and tomato was 3.70 and 6.30 and 4.05 and 8.30 days respectively. The total life cycle from egg to adult ranged amid 16.5 to 22.5 days on eggplant while on tomato it lasted amid 29.5 to 38.0 days.

Infection of Ostrinia furnacalis (Lepidoptera: Pyralidae) by Endophytic Beauveria bassiana on Corn

The Asian corn borer, Ostrinia furnacalis Guenee (Lepidoptera: Crambidae), is one of the most important pests of corn. Control against this pest is attempted in several ways, including the biological control with entomopathogenic fungi, Beauveria bassiana. Infection of B. bassiana in different larval phases can cause differences in insect response. This study aims to examine the effect of different larva’s stages when they are inoculated with B. bassiana to the growth of O. furnacalis. This study was conducted by allowing different larval instars of the pest to feed on corn plants inoculated with different dosages of B. bassiana spores. The observed parameters were larval mortality, pupal weight, adult longevity, adult fecundity and number of eggs and larvae infected by B. bassiana. The results showed that B. bassiana caused mortality to the 1st and 2nd instars of the larvae. The sub-lethal effects of B. bassiana on O. furnacalis development included reduction in pupal weight, shorter longevity, decreased fecundity of about 50% and reduced number of eggs laid up to 72.3%. B. bassiana can be transmitted vertically to the next generation. Up to 88% and 75% of the eggs and larvae were infected by the fungus, respectively. Information provided by this study is very useful for B. bassiana conservation efforts in the corn ecosystem and for supporting integrated pest management of O. furnacalis.

Lifecycle of lesser meal worm Alphitobius sp. associated with italian honey bee colonies at Sabour

This study is on the lifecycle of the lesser meal worm Alphitobius sp., infesting the hives of the Italian honey bee Apis mellifera L. The results revealed that the incubation period lasts for 6.05 ± 0.98 days as observed during rainy season. A total of eight instars were observed in grub stages. The developmental period of 1st, 2nd, 3rd, 4th, 5th, 6th, 7th and 8th instars grub was 5.67 ± 0.68, 13.73 ± 0.84, 9.90 ± 1.12, 9.03 ± 0.46 days, 11.10 ± 0.45, 8.30 ± 0.43, 9.10 ± 0.27 and 5.13 ± 0.32 days, respectively. The pupal period of the female and male lasts for 2.58 ± 0.57 and 2.48 ± 0.55 days, respectively; while their lifespan lasts for 226.10 ± 19.86 and 265.90 ± 23.03 days, respectively, depending on favourable temperature and diets. Newly emerged adults started matting within weeks, and a female can lay 977.80 ± 94.68 eggs in her lifespan of 226.10 ± 19.86 days under laboratory conditions.

Geometrics of growth in four species of Spodoptera

Four species of Spodoptera (Noctuidae: Lepidoptera) viz., S. litura (F.), S. mauritia Boisduval, S. exigua (Hub.) and S. frugiperda (J.E. Smith) were reared on castor, rice, chickpea and on artificial diet, respectively under laboratory conditions during 2017–2019 at the Department of Entomology, College of Agriculture, PJTSAU, Rajendranagar, Hyderabad. The observations on the geometrics of growth in terms of width of head capsule (widest head width) confirming to Dyar's law were made. In S. litura the linear growth ratio was 1.45 confirming a regular geometrical progression in the consecutive larval instars. In S. mauritia and S. frugiperda it was 1.62 and 1.94, respectively; but in S. exigua it was observed to vary as 1.41 (between 1st and 2nd instars), 2.61 (2nd and 3rd instars), 1.05 (3rd and 4th instars) and 1.64 (4th and 5th), with a mean of 1.68, and slightly deviating from Dyar's law. In specific, it was of the ratio of 2.61 between 2nd and 3rd instars showing the maximum progression factor, and confirming the variation among the four species evaluated.

Biology of the cucurbit fruit fly, Bactrocera cucurbitae (Coq) on host bottle gourd, Lagenaria siceraria

We investigated the biology of the cucurbit fruit fly, Bactrocera cucurbitae (coq) on bottle gourd, Lagenaria siceraria, using variety ‘BARI-Lau 1’. The mean incubation period, larval (1st, 2nd and 3rd instars), pre-pupal, pupal and total developmental periods of B. cucurbitae were 1.69±0.28, (1.72±0.33, 1.41±0.31, 2.31±0.51), 0.74±0.28, 9.2±0.78 and 36±1.69 days, respectively. The mean adult longevity, with food and without food was 14.1±1.28 and 5.0±0.81 days, respectively. The lengths of all three larval instars were 1.1± 0.9, 3.03 ± 0.95 and 6.42 ± 0.90 mm, and the widths were 0.22 ±0.11, 1.12 ± 0.01 and 2.13 ± 0.20 mm, respectively. The length and width of the pre-pupa and the pupa were 5.86 ±0.48, 5.68± 0.26 mm and 1.94 ± 0.23, 2.39±0.20 mm respectively. The length of male and female were 6.61±0.59 and 8.28±0.52 mm. The widths of males and females with wingspan were 10.97 ± 0.43 and 13.02±1.28 mm respectively. The incidence of B. cucurbitae as maggot population in bottle gourd was higher in January during the study period from December 2018 to March 2019.

Feeding Delivery of dsHvSnf7 Is a Promising Method for Management of the Pest Henosepilachna vigintioctopunctata (Coleoptera: Coccinellidae).

RNA interference (RNAi) techniques have emerged as powerful tools in the development of novel management strategies for the control of insect pests, such as Henosepilachna vigintioctopunctata, which is a major solanaceous pest in Asia. Our results showed that levels of HvSnf7 expression were greater in larval midguts than in other tissues. Silencing of HvSnf7 led to greater H. vigintioctopunctata mortality rates and appeared to be time- and partially dose-dependent. Bacterially expressed dsHvSnf7 that was applied to detached plant leaves caused 98, 88, and 60% mortality in 1st and 3rd instars, and adults after 10, 12, and 14 d, respectively; when applied to living plants, bacterially expressed dsHvSnf7 led to mortality in 1st and 3rd instars, with no effect on adults. Bacterially expressed dsHvSnf7 led to improved plant protection against H. vigintioctopunctata. Ultrastructural changes caused by HvSnf7-RNAi in larval midguts showed extensive loss of cellular contents that indicate loss of membrane integrity. This study indicate that HvSnf7 potentially can be used as RNAi target gene for controlling of H. vigintioctopunctata.