Older Larvae Research Articles

Use of Starch Granules Enriched with Carvacrol for the Lesser Mealworm, Alphitobius diaperinus Control in Chicken House: Effects on Insects and Poultry.

The aim of this study was to investigate the effect of starch granules enriched with carvacrol and mixed with straw pellets (as poultry litter) on the mortality of larvae and adults of the lesser mealworm, Alphitobius diaperinus Panzer, a cosmopolitan pest inhabiting chicken houses in vast numbers worldwide. Additionally, the effect of starch granules on the growth parameters and survival of broiler chickens exposed to treated litter was examined. In this study, granules containing 3, 5, and 10% carvacrol was used. In a simulated chicken house bioassay, this material was mixed with pellets in three different proportions: 30/70%, 40/60%, and 50/50% (granules/pellets, respectively). On this medium, young larvae (approximately 10 days old), older larvae (last stage before pupa), and unsexed 7–10 days old adults of the lesser mealworm, with access to food, were colonized. Experiments were performed at 29°C in the dark. The study shows that poultry litter with the addition of starch granules enriched with 10% of carvacrol in the proportion of 40:60% (granules:pellets) appears to be the optimal medium applicable to broiler houses for A. diaperinus control. In this environment, all larvae and adults died within 3–4 days and the overall development of the experimental chickens was similar to that of the control. However, the feed conversion rate was slightly higher in the treated group (1.72) than in the control group (1.56). The average final body weight in the treated group was 100 g lower than that in the control group (the differences were not statistically significant).

A review of the pest status and natural enemy complex of Banana skipper Erionota torus evans in south India and its management

Huge outbreaks of the banana skipper Erionota torus Evans (Lepidoptera: Hesperiidae), considered as a minor pest of bananas and plantains in the northeast India, were witnessed in South India during 2012 16. It's present status as a pest of bananas in South India is briefly reviewed here with information on its natural enemies, seasonal incidence and varietal preference. Natural enemies of E. torus from South India were surveyed during 2015–18 and 14 parasitoids were observed on various stages of E. torus including five on eggs, seven on larvae and two on pupae. Most of the parasitoids observed in South India are known to parasitize E. torus in other parts of South and South East Asia, except Acropimpla sp. nr. nigroscutis (Hymenoptera: Ichneumonidae), which is reported here as a larval parasitoid of E. torus for the first time. Egg parasitism by Ooencyrtus pallidipes (Ashmead) and early larval parasitism by Elasmus brevicornis Gahan and heavy bird predation on older larvae were identified as major regulatory factors of E. torus in South India. At present, E. torus is mostly confined to parts of Western Ghats with cooler weather than the plains and its population is lower or absent in the plains of South India where outbreaks were reported earlier, possibly due to the influence of natural enemies and adverse abiotic factors. Other management options available for the pest are briefly discussed.

Larvicidal activity of Bacillus Thuringiensis Kurstaki against Tuta Absoluta (Lepidoptera: Gelechiidae)

A commercial formulation of Bacillus thurengiensis var Kurstaki (BTK) (IAB Bt) has been shown to be effective in controlling Tutaabsoluta Zeller larvae under laboratory conditions. Five concentrations are tested ((200, .350;500;650et800ppm)by ingestion, on the various larval stages (L1, L2, L3, L4 and L5). The larval mortality caused by BTK swelledwith increasing concentrations. The high concentrations of 650 and 800 ppm give 100% mortality rates for the early stages L1, L2, L3 and L4. Theacute toxicity (LC50) of BTK calculated for all larvae is 517 ppm. The lethal efficacy of BTK is noted 02 days, after the ingestion treatment, for the young stages (L1 and L2) and 04 at 6 days for the older larvae (L3 and L4) with a LT50, all larval stages combined equal to 2.6 days.

Effects of heat stress and exposure duration on survival characteristics of different developmental stages of Propylaea japonica, a dominant aphidophagous ladybeetle in China

Extreme high temperatures in summer become more and more universal. However, the effects of high temperature on fitness and performance of different developmental stages in most biological control agents are very limited. The purpose of this work was to evaluate the effects of heat stress and exposure duration on the survival characteristics of immature and adult stages of Propylaea japonica, a dominant aphidophagous ladybeetle in China. Here, we investigated the survival characteristics of different developmental stages in P. japonica when subjecting to high temperatures, 35, 37, 39, 41 and 43 °C for exposure durations of 1, 2, 4 and 6 h, respectively, and 25 °C is the control. The results indicated that egg survival greatly decreased only at 43 °C for 4 h or 6 h, and had no significant difference from 25 to 41 °C for any exposure duration. The younger larvae were the most vulnerable stage with the minimum survival exposure to high temperature but older larvae showed stronger resistance to heat stress. The survivals of pupae and adult stages rapidly decreased only at 43 °C for exceeding 2 h. These results suggest that different developmental stages of P. japonica possess different degrees of heat resistance, which ensures its survival in summer. Moreover, according to the heat resistance of several natural enemy insects in our previous reports and the present results, a comprehensive utilization strategy of aphid biological control was constructed to restrain aphid damage and population growth in challenging environment.

Characterization of Dendrolimus houi Lajonquiere (Lepidoptera: Lasiocampidae) Transcriptome across All Life Stages.

Dendrolimus houi Lajonquiere is a phytophagous caterpillar infesting many economically important coniferous tree species in China, causing serious economic and ecological environment losses. Based on previous research, it has one generation per year in South China and East China in contrast to two generations per year in Yunnan province in southwestern China. The species is potentially resilient to climatic extremes in these regions with the eggs and 1st instar larvae surviving in the winter (5 °C), older instar larvae and pupae surviving high temperatures in the summer (35 °C), suggesting some temperature stress tolerance during different developmental stages. However, little is known in this species at the genetic and genomic level. In this study, we used high throughput sequencing to obtain transcriptome data from different developmental stages (eggs, 1st–3rd instar larvae, 4th–5th instar larvae, 6th–7th instar larvae, pupae, male and female adults), which were collected from Fujian province. In total, we obtained approximately 90 Gb of data, from which 33,720 unigenes were assembled and 17,797 unigenes were annotated. We furtherly analyzed the differentially expressed genes (DGEs) across all stages, the largest number between the eggs and 1st instar larvae stage and gene expression varied significantly in different developmental stages. Furthermore, 4138 SSR genes and 114,977 SNP loci were screened from transcriptome data. This paper will be a foundation for further study towards improved integrated pest management strategies for this species.

Displaying enhancing factors on the surface of occlusion bodies improves the insecticidal efficacy of a baculovirus.

Baculoviruses provide long-lasting control of crop pests and are harmless to humans and non-target animals, making them attractive bioinsecticides. Autographa californica multiple nucleopolyhedrovirus (AcMNPV) has a wide-host range and is one such commercial bioinsecticide, but its low infectivity to older larvae and less-sensitive species precludes its large-scale application. We sought to improve the infectivity of AcMNPV. Two enhancing factors, the truncated enhancin from Agrotis segetum granulovirus and GP37 from Cydia pomonella granulovirus, were expressed in fusion with the N-terminal and middle domain of the polyhedrin envelope protein of AcMNPV. Western blotting and immunoelectron microscopy analysis indicated that the enhancing factors were expressed on the occlusion bodies of the resulting AcMNPV variants. Bioassays showed that the median lethal doses of the recombinant viruses were 3.9-fold to 7.4-fold lower than those of the wild-type virus against the second and fourth instar of Spodoptera exigua larvae. The yields of occlusion bodies from the two recombinants in S. exigua larvae were comparable with those of the wild-type virus both in vitro and in vivo. Further bioassays showed that the AcMNPV variants fusing the enhancing factors were incapable of infecting the second instar larvae of S. litura, Helicoverpa armigera, and Pyrausta nubilalis, which were not sensitive to the wild-type AcMNPV. These genetically modified AcMNPV variants exhibited an enhanced infectivity and may offer better baculovirus control of crop pests. © 2019 Society of Chemical Industry.

Control efficacy of fungus gnat, Bradysia impatiens, enhanced by a combination of entomopathogenic nematodes and predatory mites

Fungus gnat, Bradysia impatiens, is a serious soil pest of seedlings of various crops in the greenhouse and also in mushroom nurseries. Control with chemical pesticides may not be suitable because infestation mostly occurs indoors. Here, we determined the control efficacy of two biological agents: entomopathogenic nematodes (EPNs) and predatory mites, and investigated whether the combined treatments of these two agents improved the control efficacy of B. impatiens. Mortalities of various stages of B. impatiens maggots were determined in single treatments of two species of EPNs, Heterorhabditis indica and Steinernema carpocapsae, and two species of predatory mites, Androlaelaps casalis and Stratiolaelaps scimitus. EPNs were more effective in controlling the older larvae of B. impatiens and the effect was higher with H. indica than with S. carpocapsae. Predatory mites were more effective in controlling the younger larvae of B. impatiens and the effect was higher with S. scimitus than with A. casalis. Furthermore, the control efficacy was increased by the combination of EPNs and predatory mites, when compared with the single treatments. Particularly, the combination of H. indica and S. scimitus was higher than that of H. indica and A. casalis. Therefore, the combination of H. indica and S. scimitus can be used to improve the control efficacy of B. impatiens.

Effects of high-fat diet on feeding and performance in the tobacco hornworm, Manduca sexta

Nutritionally balanced diets are important for overall fitness. For insects, fat is vital for development due to its high-energy value. Little is known about how insects regulate dietary fat for storage, but research has shown conflicting results on how altering fat impacts development and performance. In this study, we sought to investigate how high-fat diets affect developing insects. To determine how insects respond to variation in dietary fat content, we reared Manduca sexta of different larval stages on diets containing varying concentrations of linseed oil in high (5.6%), medium (3.4%) or low (0.4%) fat. Young larvae reared on high-fat diets had 80% mortality and 43% lower body mass compared to those reared on medium- or low-fat diets. Older larvae showed no difference in mortality with increasing dietary fat content, but they were smaller than controls, suggesting a developmental shift in lipid metabolism. We measured mRNA expression of Apolipoprotein I and II (APO1 and 2), proteins responsible for transporting lipids, as a possible explanation of increased survival in older larvae. Levels of APO1 and 2 mRNA did not differ with dietary fat content. We then tested the hypothesis that the high-fat diet altered feeding, resulting in the observed decrease in body size. Caterpillars fed a high-fat diet indeed ate less, as indicated by a decrease in food consumption and the number and mass of fecal pellets produced. These results suggest that increased fat disrupted feeding and may indicate that there is a threshold for lipid storage, but further studies are needed to understand the underlying mechanism.

Nearshore environmental conditions influence larval growth and shape changes for a temperate rocky reef fish

Coastal upwelling and other oceanographic processes, exert influences on phenotypic traits of early life stages of marine fishes. However, it remains to elucidate the environmental effects on the morphology of fish larvae. Using geometric morphometrics and otolith microstructure of a temperate rocky reef fish, the labrisomid blenny Auchenionchus crinitus (Labrisomidae), we studied the larval growth, mortality and morphospace of four consecutive cohorts, hatched between austral winter and summer off central Chile. We hypothesize that coastal environmental conditions will influence early life traits of this cryptobenthic fish. The winter cohort, which inhabited colder and well-mixed nearshore waters, grew more slowly and had a more hydrodynamic head shape, while the summer cohort, which lived in warmer and stratified waters, grew faster, but had a more robust shape. Cohorts expressed less ontogenetic allometry as seasons progressed, suggesting that the seasonal increment in water temperature reduces the shape changes with size during larval development. Also, slower- and faster-growing larvae showed large variation from the consensus shape, e.g. had the largest shape disparity. Nonetheless, all cohorts showed similar mortality rates during the first month of life. Finally, increases in zonal wind stress (i.e. sea breeze) and decreases in the sea temperatures (i.e. upwelling events) increased the growth rates of older (> 15 days old) larvae. Therefore, for this cryptobenthic species, differences in growth rate and body shape are related to the seasonal increase in water temperature, and local-scale meteorological conditions.

Effects of Host Age and Density on the Performance of Apanteles hemara (Hymenoptera: Braconidae), a Larval Endoparasitoid of Spoladea recurvalis (Lepidoptera: Crambidae)

The amaranth leaf-webber, Spoladea recurvalis (Fabricius; Lepidoptera: Crambidae), is a serious pest of Amaranthus sp. in Africa and Asia. Apanteles hemara (Nixon; Hymenoptera: Braconidae) is by far the most important larval endoparasitoid of the amaranth leaf-webber. We examined the effects of host density and age on the biological characteristics of A. hemara. The regression model of the number of hosts supplied to A. hemara against the number of larvae parasitized resulted in a curve corresponding to type II functional response, with a significant increase in the number of hosts parasitized up to the density of 30 hosts before being constant up to 40 hosts. In contrast, the parasitism rate decreased linearly with increasing host densities. Development time, sex ratio, and adult longevity were not significantly affected by host density. The immature parasitoid mortality was significantly higher at higher host densities. Apanteles hemara did not parasitize 7-d-old larvae and beyond, while parasitism was significantly higher among 1- to 2-d-old compared with 3- to 4-d-old larvae. Immature parasitoid mortality was 2.6 times higher in 1- to 2-d-old larvae compared with 5- to 6-d-old larvae. The developmental period of the parasitoid from egg to adult was longest among 1- to 2-d-old larvae and least among 5- to 6-d-old larvae. Nonreproductive mortality was markedly higher among 1- to 2-d-old larvae compared with the older larvae. Adult female A. hemara were significantly larger on 3- to 4-d-old larvae compared with either 1- to 2-d-old or 5- to 6-d-old larvae. We discuss the implications of our results for the interpretation of functional response in parasitoids, mass rearing, conservation, and augmentative biological control of S. recurvalis.

Distribution of Hippoidea (Decapoda, Anomura) larvae off Veracruz, southern Gulf of Mexico: inferences about their migration route

Abstract The distribution and abundance of hippoid zoeal stages offshore Veracruz, southern Gulf of Mexico, and the migration routes of these larvae in the western Atlantic, were analysed. Samples were collected with a Bongo net and larval dispersal was analysed applying the HYCOM hydrodynamical model; particles (virtual larvae) originating from 35 sites were tracked for 77 days. Larvae of Albunea paretii Guérin-Méneville, 1853 were the most abundant, and dispersal simulations indicated that older larvae occurring off Veracruz might originate from Texas. However, a substantial proportion of self-recruitment (7.8%) can occur, mainly due to the seasonal changes in direction of currents over the shelf as well as the high variability in weather conditions. Results also suggest that several generations of A. paretii are needed for the species to reach Veracruz from South America. A hypothetical model regarding the migration routes of A. paretii larvae in the western Atlantic is proposed.

The Expression of agrp1, A Hypothalamic Appetite-Stimulating Neuropeptide, Reveals Hydrodynamic-Induced Starvation in a Larval Fish

AbstractLarval fish suffer dramatic mortality in the days following transition to autonomous feeding, with over 90% of larvae being eliminated within a period of few weeks. Recent work has shown that the hydrodynamic environment experienced by recently-hatched larvae impedes their feeding rates even under high prey densities. Here, we quantified starvation through early ontogeny in Sparus aurata larvae (8–18 days post-hatching; DPH) and tested whether the emerging ontogenetic pattern is consistent with that expected one based on the hydrodynamic environment that these larvae experience. We screened three candidate genes agrp1, npy, and hsp70, whose expression was previously shown to respond to starvation in fish. Of the three genes, agrp1 was identified as a suitable indicator for starvation. Localization of agrp1 mRNA by whole-mount in-situ hybridization confirmed that, in S. aurata larvae, agrp1 is expressed only in the hypothalamus. Quantification of agrp1 mRNA using real-time PCR revealed that the expression of this gene is elevated in starved compared to fed larvae, and in younger (8 DPH) compared to older larvae (18 DPH). Manipulating the water viscosity to simulate the hydrodynamic conditions during the onset of the critical period led to increased agrp1 expression. These findings suggest that the hydrodynamic constraints on larval feeding lead to the starvation of small larvae. Further, they provide a mechanistic explanation for the “safe harbor” hypothesis, which postulates that larvae should allocate resources toward rapid linear growth to escape detrimental effects of dwelling in an environment where viscous fluid forces dominate.

Interplay between age-based competitive asymmetries within the brood and direct competition between inbred and outbred offspring in a burying beetle.

Theory suggests that intraspecific competition associated with direct competition between inbred and outbred individuals should be an important determinant of the severity of inbreeding depression. The reason is that, if outbred individuals are stronger competitors than inbred ones, direct competition should have a disproportionate effect on the fitness of inbred individuals. However, an individual's competitive ability is not only determined by its inbreeding status but also by competitive asymmetries that are independent of an individual's inbreeding status. When this is the case, such competitive asymmetries may shape the outcome of direct competition between inbred and outbred individuals. Here, we investigate the interface between age-based competitive asymmetries within broods and direct competition between inbred and outbred offspring in the burying beetle Nicrophorus vespilloides. We found that inbred offspring had lower survival than outbred ones confirming that there was inbreeding depression. Furthermore, seniors (older larvae) grew to a larger size and had higher survival than juniors (younger larvae), confirming that there were age-based competitive asymmetries. Nevertheless, there was no evidence that direct competition between inbred and outbred larvae exacerbated inbreeding depression, no evidence that inbreeding depression was more severe in juniors and no evidence that inbred juniors suffered disproportionately due to competition from outbred seniors. Our results suggest that direct competition between inbred and outbred individuals does not necessarily exacerbate inbreeding depression and that inbred individuals are not always more sensitive to poor and stressful conditions than outbred ones.

Zophobas atratus (Fabricius, 1775) – new genus and species of darkling beetles (Coleoptera, Tenebrionidae) for the fauna of Ukraine

Darkling beetle Zophobas atratus (Coleoptera, Tenebrionidae) is recorded here for the first time as a new species for the fauna of Ukraine. Detailed study on morphology of preimaginal stages and biology of this species recently introduced to Ukraine, is given here. Zophobas atratus is an important species being easily reared in laboratory cultures and widely distributed in North and South America, Europe, and Asia. Detailed descriptions of all life stages, including egg, young and older larvae, pupa and adult of Z. atratus are required for further taxonomical study of the genus Zophobas, which isn’t yet definitively established. New identification keys for adults and larvae of the genera of tribe Tenebrionini are presented here, based on a comparative analysis of the taxonomic characters of adults and larvae of Z. atratus and species from the genera Tenebrio and Neatus. Comparative analysis of morphology of larva of Z. atratus and larvae of the tribe Cteniopodini of close subfamily Alleculinae was conducted here. The subfamily Alleculinae previously had the rank of family Alleculidae, but our analysis confirmed the reliability of its current taxonomic position as subfamily. The study of morphology of larvae of 1st and 2nd instars of Z. atratus revealed that they are characterized by special taxonomic structures that are not characteristic for oldest instars of larvae of Z. atratus. These characters include absence of spines on caudal segment, presence of a set of 4 setae at posterior margin of tergites of prothorax, metathorax, and 1st to 8th abdominal segments, strongly convex 2nd antennal segment and sensory zone in the form of an open ring on its apex, and etc. Moreover, structure of antenna of larvae of Z. atratus is similar to that of oldest larvae of most species of darkling beetles of the fauna of Ukraine. The most distinctive features of Z. atratus are: sexual dimorphism in structure of clypeus of adults; filiform sclerotized antenna of larva with a continuous sensory zone at apex of 2nd segment, weakly developed 3rd segment; fusion of sclerotized pleurites of 1st–8th abdominal segments with their tergites; sexual dimorphism in structure of 9th abdominal segment of pupa, and presence of two hooks on apex of its appendages. The data of original study of features of life cycle of Z. atratus are given. The pictures and photos of details of morphology of egg, larvae, pupa and adult of Z. atratus are presented. It was recored that life cycle of Z. atratus from laying of egg to the emergence of adult continues from 169 up to 181 days. Adults lived maximum up to 206 days. Maturation of eggs in female after copulation continues 10-11 days. Stage of egg continues 7 days, larva – up to 151 days, including pre-pupal period from 6 to 22 days, pupa – from 8 to 21 days. Twelve larval stages of Z. atratus were recorded in laboratory culture.

Adult oviposition preferences and larval performance of rice leaf folder, Cnaphalocrocis medinalis on rice and non-rice graminaceous plants

The rice leaf folder, Cnaphalocrocis medinalis Guenee (Lepidoptera: Pyralidae), occurs throughout southeast and northeast Asia, and has a broad host range including graminaceous crops and weeds. Unraveling the relationship between adult oviposition preference and offspring performance is central to understanding the evolution of plant–insect interactions. In the present study, we examined oviposition behavior and larval performance of the C. medinalis on rice plants and non-rice graminaceous plants. Using choice oviposition experiments, female C. medinalis moths preferred rice volatiles, and laid significantly more eggs on the leaves of rice plants than non-rice graminaceous plants. Larval performance, as assayed by host plant selection rate, and host suitability, were evaluated by using multi-choice experiments and life-table analysis, respectively. Larval host selection experiments showed that the younger C. medinalis larvae (1st and 2nd instar) exhibited a stronger ability to identify rice hosts compared to non-rice graminaceous plants than older larvae (3rd to 5th instar). The results of life-table studies showed that C. medinalis developed and grew faster on rice plants than on non-rice graminaceous plants. In particular, the graminaceous crop, sugarcane Saccharum officinarum, and graminaceous weeds Miscanthus sinensis and Setaria viridis, prevented the development and ovipositing of C. medinalis. Our results showed the strong preference that C. medinalis adults had to oviposit and larvae had to develop on rice and this was highly consistent within the population tested. This indicated that oviposition preference of female C. medinalis moths might play an important role in larval host identification between rice plants and non-rice graminaceous plants.

TIME - MORTALITY RELATIONSHIPS FOR THE LIFE STAGES OF RED FLOUR BEETLE, TRIBOLIUM CASTANEUM EXPOSED TO HIGH AND LOW TEMPERATURES, AND THEIR RELATION WITH FLOUR TECHNOLOGY

Temperature treatments of stored grains and grain products are the best physical method which successfully kills several life stages of insects. Survival of adults, pupae, younger larvae and older larvae of Tribolium castaneum exposed to 40, 50, 60, -5 and -10 oC at different exposure periods (15, 20, 25, 30, 40, 45, 60, 90 and 120 min) were investigated. Probit analysis was used to determine the lethal time required for 50 and 95% kill (LT50 and LT95) of the population of tested insect, results indicated that: Younger and older larvae were the most heat susceptible stages with LT50 and LT95 as compared the pupae and adult stages at the higher temp. (60 oC). Pupae and adult stages were the most heat tolerant stage at 60 oC. Exposing the beetles to 60 oC and -10 oC resulted in higher mortality than for beetles that were maintained at two previous tested temperature. The cold tolerance of different stages from lower to highest at -5 and -10 oC were older larvae < younger larvae < adult < pupae. Grain Technology studied were carried out on samples of wheat flour exposed to 60 oC for 120 min. and to -10 oC for 90 min. to determining chemical composition, Rheological properties and organoleptic characteristics of balady bread. Results indicated that No significant differences were observed between treated samples and untreated control. Finally, it could be concluded that the influence of both heat or cold treatments on the mortality rate of the tested insect was positively correlated with the time of exposure, the increase of heat or cold temperature and the stage of an insect.

Infection of a nucleopolyhedrovirus to Neodiprion zhejiangenis Zhou & Xiao (Hymenoptera: Diprionidae)

ABSTRACTNeodiprion zhejiangenis Zhou & Xiao 1981 (Hymenoptera: Diprionidae) nuclear polyhedrosis virus (NezhNPV) is a biocontrol factor with high development potential and application prospects. To study the insecticidal activity of NezhNPV against the larvae of N. zhejiangenis, the susceptibility of larvae at different instars to different NezhNPV concentrations was determined based on laboratory bioactivity. At 2.0 × 107 polyhedron inclusion body (PIB)/mL, the median lethal time required to kill 50% of the instar 2 and 3 larvae was approximately 5 d, whereas the median lethal time of the instar 4 and 5 larvae was 8–9 d. Interestingly, at the NezhNPV concentrations of 2.0 × 103 and 2.0 × 104 PIB/mL, the feeding ability of the surviving larvae was decreased by 57.4% and 76.4%, respectively, compared with the controls; the pupal weight at both concentrations was decreased by approximately 27%, and the adult emergence rate was decreased by 27.4% and 50.9%, respectively, with a significantly higher proportion of males than of females. The results showed that younger instar larvae of N. zhejiangenis were more susceptible to NezhNPV infection than older instar larvae. The larval mortality rate was dependent on the larval instar and NezhNPV concentration.

Cannibalistic behavior of aphidophagous coccinellid, Hippodamia variegata (Goeze, 1777) (Coleoptera: Coccinellidae)

The variegated lady beetle, Hippodamia variegata (Goeze, 1777) is widely distributed in different agroecosystems of Turkey. Cannibalism, intraspecific predation, where individuals of the same species feed upon each other, is a common phenomenon in most aphidophagous coccinellids including H. variegata. We investigated the cannibalistic behavior of various growth stages of H. variegata in the presence and absence of Acyrthosiphon pisum Harris, 1776 under laboratory conditions . The results for cannibalism of eggs and larvae by adults revealed that eggs and younger larvae were more vulnerable to cannibalism. Notably, egg cannibalism by adults was found to be higher even at high prey abundance. Whereas, larval cannibalism was found significantly lower. Cannibalism of eggs by larvae and within the larvae showed that older larvae consumed significantly higher number of eggs and younger larvae in the absence of A. pisum indicating that cannibalism was mainly influenced by scarcity of prey. However, all the larval instars, especially 4 th and 3 rd instars, also consumed a substantial number of eggs even in the presence of prey. Cannibalism within the same stage/age larvae showed a successive increase with the successive larval stage showing minimum cannibalism by 1 st instar larvae and maximum by 4 th instar larvae. The study found that scarcity of prey leads to cannibalism in H. variegata and that egg cannibalism occurs even at high prey densities.

Nonsensical choices? Fall armyworm moths choose seemingly best or worst hosts for their larvae, but neonate larvae make their own choices.

Selecting optimal host plants is critical for herbivorous insects, such as fall armyworm (Spodoptera frugiperda), an important maize pest in the Americas and Africa. Fall armyworm larvae are presumed to have limited mobility, hence female moths are presumed to be largely responsible for selecting hosts. We addressed host selection by fall armyworm moths and neonate and older (3rd-instar) larvae, as mediated by resistance and herbivory in maize plants. Thus, we compared discrimination among three maize cultivars with varying degrees of resistance to fall armyworm, and between plants subjected or not to two types of herbivory. The cultivars were: (i) susceptible, and deficient in jasmonic acid (JA) production and green leaf volatiles (GLV) emissions (inbred line B73-lox10); (ii) modestly resistant (B73), and; (iii) highly resistant (Mp708). The herbivory types were: (i) ongoing (= fall armyworm larvae present), and; (ii) future (= fall armyworm eggs present). In choice tests, moths laid more eggs on the highly resistant cultivar, and least on the susceptible cultivar, though on those cultivars larvae performed poorest and best, respectively. In the context of herbivory, moths laid more eggs: (i) on plants subject to versus free of future herbivory, regardless of whether plants were deficient or not in JA and GLV production; (ii) on plants subject versus free of ongoing herbivory, and; (iii) on plants not deficient in compared to deficient in JA and GLV production. Neonate larvae dispersed aerially from host plants (i.e. ballooned), and most larvae colonized the modestly resistant cultivar, and fewest the highly resistant cultivar, suggesting quasi-directional, directed aerial descent. Finally, dispersing older larvae did not discriminate among the three maize cultivars, nor between maize plants and (plastic) model maize plants, suggesting random, visually-oriented dispersal. Our results were used to assemble a model of host selection by fall armyworm moths and larvae, including recommendations for future research.

In Vivo Production of Agrotis ipsilon Nucleopolyhedrovirus for Quantity and Quality.

The black cutworm, Agrotis ipsilon (Hüfnagel) (Lepidoptera: Noctuidae), is a pest causing damage to a variety of plants including turf and row crops. A recently discovered baculovirus has the potential to be developed as a microbial-based biological pesticide to provide targeted control of this insect pest. In an effort to develop this baculovirus as a biological pesticide, experiments were conducted to determine parameters necessary to maximize in vivo production using cutworm larvae. Treatment combinations including three larval diets, larval age at infection (6- to 10-d old), and dosage of virus exposure (1 × 105 to 1 × 108 occlusion bodies [OBs]/ml) were evaluated. Production quantity and quality were measured as number of OBs produced and insecticidal activity of the virus, respectively. Generally speaking, insect diets that maximized larval growth resulted in a greater quantity of virus OBs. Less virus was produced when younger (small) larvae were exposed to higher dosages of virus resulting in rapid mortality and when older (large) larvae were exposed to low dosages of virus resulting in low levels of infection. Virus quality was measured as insecticidal activity (low LC50 representing high activity) and was highest for larger larvae exposed to minimal virus concentrations needed to initiate infections. When considering both quantity and quality measurements, maximum production was achieved for 8- to 9-d-old larvae fed a general purpose lepidoptera diet. These results will support the development of this baculovirus as an additional tool for the integrated control of the black cutworm.