Influence of dietary alkaloids on survival and growth of Spodoptera littoralis

A total of 25 alkaloids including benzylisoquinoline, monoterpenoid indole, quinolizidine, tobacco and tropane alkaloids were studied for deleterious effects towards neonate larvae of the generalist herbivore Spodoptera littoralis. Alkaloids were incorporated into artificial diet at several concentrations including the respective natural concentration as present in planta as well as two arbitrarily chosen concentrations (0.1 and 0.2% g⁻¹ fresh wt.) for comparison of the bioactivities. After 5 days of exposure almost all of the alkaloids studied reduced larval growth compared to controls. Larval survival, however, was reduced by more than 50% compared to controls only in the presence of berberine, colchicine and nicotine. Several compounds including for example the Cinchona alkaloids quinidine, quinine or cinchonidine which showed little effect on larval survival after 5 days of exposure turned out to be considerably more active when insects were exposed to the respective alkaloids for their whole larval period. In the chronic exposure studies all of the latter alkaloids caused high larval mortality. The pupal weights were significantly lower than those of the controls. Dietary utilization studies indicated that feeding deterrency is important for the adverse effects caused for example by berberine, quinine or quinidine whereas the high larval mortality observed in the presence of cholchicine or nicotine seems to be primarily due to the acute toxicity of these latter alkaloids.     

Switchover in the sensitivity of the prothoracic glands to juvenile hormone in the cotton leafworm, Spodoptera littoralis

Switchover in the sensitivity of the prothoracic glands to juvenile hormone analogue during the last-larval instar of Spodoptera littoralis occurs in the middle of the third scotophase i.e. at the end of phagoperiod when the body weight is maximal and the ecdysteroid is increasing in the haemolymph. Application of the analogue to larvae neck-ligated before the switchover completely inhibits or delays metamorphosis due to an inhibitory effect on the prothoracic gland cells and is not mediated by the nervous system. This inhibition by the analogue is dose-dependent, and when complete inhibition of metamorphosis occurs, the prothoracic glands cells degenerate. Treatment of neck-ligated larvae with the analogue after the switchover stimulates metamorphosis by accelerating the appearance of an ecdysteroids peak in the haemolymph. The stimulatory effect of the analogue to the prothoracic glands in neck-ligated larvae is not direct one, and some unknown factors seem to play a role therein.

The probale role of prothoracicotropic hormone as a synchronizing factor in the switchover in the sensitivity of the prothoracic glands to juvenile hormone is discussed.     

Endocrine background of how 20-hydroxyecdysone agonist, RH 5849, influences diurnal pattern of pupation in shape Spodoptera littoralis

Under laboratory conditions (L16:D8, 24°C, r.h. 80%), applying of an ecdysone agonist, RH 5849, (1,2-dibenzoyl-1-tert-butylhydrazine) onto final instar larvae of Spodoptera littoralis (Boisd.), Noctuidae, Lepidoptera, delayed or advanced the time of pupation depending on the time of treatment. This response was dose-dependent. In addition, non-lethal doses of RH 5849, ranging from 0.05 to 10 µg/larva were used. Following treatment of S. littoralis larvae with 5 µg RH 5849 the endogenous ecdysteroid level was increased or decreased depending on the time of application. Based on the results presented, we suggest that potential users of non-steroidal ecdysone agonists should consider the proper circadian timing of application in the field.     

黄带犀猎蝽成虫对斜纹夜蛾幼虫的捕食功能反应

[目的] 探明黄带犀猎蝽成虫对斜纹夜蛾幼虫的捕食潜力。[方法] 在室内条件下,研究了黄带犀猎蝽对斜纹夜蛾2、3、4龄幼虫的捕食功能反应、搜寻效应和干扰反应。[结果] 黄带犀猎蝽成虫对斜纹夜蛾2、3、4龄幼虫的捕食功能反应模型均符合Holling II型,即其捕食量随猎物密度的增加而增加,其搜寻效应随猎物密度的增加而减小,HollingⅡ方程依次为：N_a=0.9750N/（1+0.0273N）、N_a=1.1654N/（1+0.0804N）,N_a=1.3058N/（1+0.1799N）;黄带犀猎蝽成虫自身密度干扰反应符合HasseⅡ型（E=0.337P^-0.565）,即随着自身密度的增加,平均捕食量逐渐减少,捕食作用率逐渐降低。[结论] 黄带犀猎蝽成虫对斜纹夜蛾幼虫有较好的防治潜力,可用于斜纹夜蛾的生物防治中。     

Age-dependent physiological responses of last instarHelicoverpa zea larvae to oral and topical application of precocene II

Newly-ecdysed last instar larvae ofH. zea grouped into 100-, 200-, 300-, or 400-mg categories were fed diet containing precocene II or given precocene II topically on the abdomen. The time for larvae to reach a maximal weight, time to pupation, growth rate, and the amount of precocene II excreted were calculated. Younger larvae of lower weights, which were fed or topically treated with precocene II required more time to reach their maximal weight, had a lower maximal weight, a lower growth rate, and required more time to pupate than control larvae. Older larvae represented by the largest weight category were less sensitive to precocene II, had a shorter delay in reaching maximal weight, and a shorter delay in the time to pupation than control larvae; larvae in the largest weight category that were fed precocene II also had smaller decreases in the growth rate. Growth rate declines for larvae given topical doses of precocene II, however, were largest for the oldest larvae. All larvae given a single topical dose excreted precocene II for several days and were most efficient at eliminating smaller doses; larger, older larvae excreted more precocene II than smaller, younger larvae. Age-dependent responses to precocene II indicate that growth and metabolic processes, as well as xenobiotic metabolism, change in last instar larvae.     

Treatment of larvae with repeated doses of precocene II induces precocious metamorphic changes in Spodoptera mauritia (Lepidoptera: Noctuidae)

In Spodoptera mauritia repeated daily treatments of larvae with 40 μg of precocene II throughout the fifth and sixth instar larval period had no effect on the larval-larval period but prolonged larval-pupal ecdysis. The resulting pupae showed precocious adult differentiation of mouth parts, wings, eyes, legs, and fat body.     

中国绮夜蛾属Acontia Ochsenheimer分类学修订（鳞翅目：夜蛾科：绮夜蛾亚科）

首次报道尺蛾科泽尺蛾属Zamarada Moore, 1887和超泽尺蛾Z. excisa Hampson, 1891在我国分布,给出了形态描述和特征图。     

RFLP analysis of genetic variation in North American populations of the fall armyworm moth Spodoptera frugiperda (Lepidoptera: Noctuidae)

A high level of genetic variability was detected in North American fall armyworm (FA W), Spodoptera frugiperda (J. E. Smith), populations by restriction fragment length polymorphism (RFLP) analysis of genomic DNA. In nearly all cases individual larvae could be differentiated using 22 probe-enzyme combinations. Laboratory colonies formed distinct groups based on RFLP analysis. Individuals from a colony of the previously determined ‘rice strain’ formed a group showing obvious deviation in RFLP patterns from the other five populations, which included a population from a ‘com strain’ colony. The results were consistent with previous studies using allozymes which indicated that there are two genetically differentiated forms of the fall armyworm. Diagnostic markers were also found that distinguish these two groups.     

甲维盐对斜纹夜蛾幼虫肠道细菌的影响

【目的】斜纹夜蛾幼虫属杂食性、高食量的害虫,通过分子生物学手段对经甲维盐处理后的斜纹夜蛾幼虫肠道微生物进行比对,研究肠道共生菌群受毒剂刺激后的代谢变化,探讨菌株的自身代谢与甲维盐的作用受体的相关性。【方法】基于Illumina MiSeq技术测序平台,对取食甲维盐和未取食甲维盐的斜纹夜蛾幼虫中肠细菌的16S rRNA可变区进行高通量测序,分析对比细菌群落结构多样性。【结果】肠杆菌属、根瘤菌属在斜纹夜蛾的肠道中占优势地位,经过甲维盐处理后两者的丰度大幅下降。沙雷氏菌属和黄单胞杆菌属在处理后减少到几乎为零,相反,原先不占据优势的棒状杆菌属和甲醇杆菌属,处理后丰度明显上升。【结论】甲维盐处理后的优势菌群以及丰富度均发生变化,表明斜纹夜蛾的肠道菌群结构可能与甲维盐毒理机制有关。     

Distribution and metabolism of exogenous ecdysteroids in the egyptian cotton leafworm Spodoptera littoralis (lepidoptera: noctuidae)

After ingestion of various amounts of either [³H]ecdysone or [³H]20-hydroxyecdysone (0.8 ng to 10 μg) by sixth instar larvae of the Egyptian cotton leafworm Spodoptera littoralis, apolar metabolites are rapidly detected in the gut and frass. Hydrolysis of the apolar products with Helix hydrolases releases solely [³H]ecdysone or [³H]20-hydroxyecdysone, respectively. This, coupled with the formation of chemical derivatives (acetonide and acetate) which cochromatograph with authentic reference compounds on hptlc and hplc demonstrates that these apolar metabolites consist of ecdysone or 20-hydroxyecdysone esterified at C-22 with common long-chain fatty acids. The major fatty acids have been identified by RP-hplc and their contribution to the mixture determined. In contrast, [³H]ecdysone injected into the haemolymph of S. littoralis is metabolized to yield 20-hydroxyecdysone, ecdysonoic acid, and 20-hydroxyecdysonoic acid. Thus, two different pathways exist for the metabolism of ecdysteroids in this species. In addition to an essentially polar pathway operating on injected and endogenous ecdysteroids, exogenous ecdysteroids entering the gut of S. littoralis are detoxified, yielding apolar ecdysteroid 22-fatty acyl esters which are rapidly excreted. The significance of these results in relation to the effects of ingested ecdysteroids on S. littoralis is discussed. Arch. Insect Biochem. Physiol. 34:329–346, 1997. © 1997 Wiley-Liss, Inc.     

Variability in the behavioural responses of three generalist herbivores to the most abundant coumarin in Daphne laureola leaves

We evaluated the responses of three generalist herbivores (Lepidoptera: Noctuidae) to the most abundant coumarin in young leaves of spurge-laurel, Daphne laureola L. (Thymelaeaceae), a perennial shrub consistently fed upon by several noctuid species. Pseudenargia ulicis Staud and Noctua janthe Borkhausen are natural herbivores of the species in southeastern Spain, whereas Spodoptera littoralis Boisduval is a model species frequently used to address the antifeedant role of secondary compounds. Discrimination between control and coumarin-coated D. laureola leaves was investigated by short-term choice experiments. We found species-specific behavioural responses to the treatment: P. ulicis preferred the control leaves, whereas S. littoralis did not discriminate between leaf treatments, although it clearly avoided coumarin when incorporated into an artificial diet, and N. janthe preferred the coumarin-coated leaves. Furthermore, N. janthe larvae reduced consumption when the proportion of treated leaves ingested increased and consumption of S. littoralis larvae was also reduced in coumarin-containing diet under no-choice conditions. Our results highlight that different herbivore species feeding simultaneously on the same host plant respond differently to a single chemical defence compound, likely constraining a directional response of the plant to selection.     

4种昆虫病原线虫对草地贪夜蛾的致死作用

【目的】探讨昆虫病原线虫对草地贪夜蛾幼虫的侵染效果。【方法】在室内条件下采用生测试验法,测定了小卷蛾斯氏线虫AⅡ、长尾斯氏线虫X-7、夜蛾斯氏线虫SN和嗜菌异小杆线虫H06等4种昆虫病原线虫对草地贪夜蛾2龄和5龄幼虫的致死作用。【结果】小卷蛾斯氏线虫AⅡ与草地贪夜蛾数量比为50∶1时,36 h后草地贪夜蛾2龄和5龄幼虫的死亡率分别为92%和100%。长尾斯氏线虫X-7与草地贪夜蛾数量比为50∶1时,36 h后草地贪夜蛾2龄幼虫的死亡率为80%;在数量比30∶1时,36 h后草地贪夜蛾5龄幼虫死亡率为100%。夜蛾斯氏线虫SN与草地贪夜蛾数量比为400∶1时,36 h后草地贪夜蛾2龄和5龄幼虫的死亡率分别为88%和85%。嗜菌异小杆线虫H06与草地贪夜蛾在400∶1时,36 h后草地贪夜蛾2龄和5龄幼虫的死亡率分别为32%和67.5%。【结论】小卷蛾斯氏线虫AⅡ具有较好的草地贪夜蛾生物防治潜质,其次是长尾斯氏线虫X-7。     

A comparative study of sex pheromone reception in the Hadeninae (Lepidoptera: Noctuidae)

Abstract A comparative study of the olfactory responses to pheromone compounds was performed in twenty-four species of Hadeninae. Electroantennograms (EAG) were recorded on male moths in response to thirty compounds and the response profiles of each species were analysed by factorial correspondence analysis. A limited number of molecules were found active and the most effective stimuli were Z9 tetradecenes and Z11 hexadecenes. The species of the Mythimna genus were most sensitive to aldehydes. Tholera decimalis did not respond to any of the molecules tested. The species belonging to the Mamestra and the Orthosia genera responded to a variety of molecules and no simple correlation was found between the genus and the EAG sensibility. Pheromone reception is discussed in relation to the taxonomy and the evolution of olfactory communication in Hadeninae.     

Characterization of eight microsatellite loci in the maize stalk borer Busseola fusca Fuller, 1901 (Lepidoptera: Noctuidae)

The noctuid stem borer Busseola fusca occurs throughout sub‐Saharan Africa, where it is considered as a major pest of corn and sorghum. To understand B. fusca phylogeography, we isolated and characterized eight microsatellite loci in this species. We investigated these loci for polymorphism on a subset sample of individuals from different geographic populations. All loci were polymorphic, showing between four and 10 alleles. Cross‐species amplification of four of these loci was tested on 11 other noctuid species.     

Ferritin acts as a target site for the snowdrop lectin (GNA) in the midgut of the cotton leafworm Spodoptera littoralis

The snowdrop lectin GNA (Galanthus nivalis agglutinin) has been shown to possess insecticidal activity to a range of economically important insect pests. However, the precise mechanism of insecticidal action of GNA against insects remains unknown. In this investigation, we attempted to purify and identify receptor(s) responsible for binding of GNA in the larval midgut of a major lepidopteran pest (the cotton leafworm, Spodoptera littoralis) to better understand its mode of action. Therefore, cytoplasmic as well as membrane proteins from 800 larval midguts were chromatographed on a column with immobilized GNA. Sodium dodecyl sulfate‐polyacrylamide gel electrophoresis analysis of the proteins eluted from the GNA column followed by sequencing of the GNA‐binding proteins and BLAST analyses revealed that the N‐terminal sequences of a 24 kDa polypeptide purified from the cytoplasmic and membrane protein fraction revealed sequence similarity to sequences encoding heavy chain homologs of ferritin from Manduca sexta (76% sequence identity), Calpodes ethlius (80% sequence identity) and Bombyx mori (61% sequence identity). Furthermore, the N‐terminal sequence of a 31 kDa polypeptide from the membrane protein fraction showed sequence similarity to a light chain homolog of ferritin from Manduca sexta (88% sequence identity).     

Visual feedback in the control of pheromone-mediated flight ofHeliothis virescens males (Lepidoptera: Noctuidae)

MaleHeliothis virescens (F.) (Lepidoptera: Noctuidae) were made to fly into a uniformly white and translucent tube within a large wind tunnel while responding to sex pheromone. Different visual patterns placed within the tube greatly affected the ability of the male moths to maintain upwind progress or remain oriented to the wind while in contact with the plume. Over 89% of males attempting to fly through a blank tube, lacking visual patterns, became disoriented, the males gaining or losing altitude and repeatedly hitting the sides of the tube. Patterns of 20–40 dots placed on the sides of the tube at or slightly above plume level resulted in high levels of sustained upwind flight (47–74%) relative to patterns placed directly below (30–40%), directly above (35%), or slightly below the level of the flight path (26–44%). Optimal upwind progression in pheromone-responding males occurred when image motion could be resolved both transversely (T), orthogonally to the longitudinal axis of the body relative to the horizontal plane of the environment, and longitudinally (L), along the body axis. Even very sparse patterns (single rows of dots) could elicit high levels of sustained upwind flight (53–63%) when positioned within the tube such that the males' movements would create both L and T image motion. However, successful negotiation of the tube was also unexpectedly facilitated by patterns apparently providing no horizontal transverse component for flying males but providing longitudinal flow while centering the moth in the plume through a symmetrical left-right input (4–40%).     

Acylamines enhance the infection of a baculovirus of the armyworm, Pseudaletia unipuncta (Noctuidae,Lepidoptera)

The acylamines (cationic detergents) enhance the infection of a nuclear polyhedrosis virus (NPV) in larvae of the armyworm, Pseudaletia unipuncta. Those with 6 carbons (hexylamine) or 12 carbons (dodecylamine) in the acyl group are more effective in enhancing the NPV than those with 4, 8, or 10 carbons. Hexylamine and dodecylamine increase the rate of infection beyond the 50% level (ID₅₀) by 10 to 100 times when based on the concentration of the virus polyhedra (inclusion bodies).     

斜纹夜蛾抗药性监测及茚虫威对其解毒代谢酶的影响

【目的】斜纹夜蛾Spodoptera litura (Fabricius)是主要的农业害虫之一。本研究旨在明确该害虫在湖南省5个主要蔬菜种植区的抗药性水平,并探讨该害虫对茚虫威的抗性与解毒代谢酶活性之间的关系,为斜纹夜蛾有效防控及抗性治理提供依据。【方法】采用浸叶法测定了2014-2016年湖南5地斜纹夜蛾田间种群对10种杀虫剂的抗性水平;将斜纹夜蛾敏感种群3龄幼虫在死亡率40%~70%的选择压下用茚虫威进行汰选,比较了斜纹夜蛾敏感种群和抗茚虫威种群的羧酸酯酶、谷胱甘肽S-转移酶和多功能氧化酶对硝基苯甲醚O-脱甲基活性。【结果】湖南5地斜纹夜蛾田间种群对有机磷类杀虫剂产生了26.9~220.2倍的抗性,对氨基甲酸酯类杀虫剂产生了68.3~890.8倍的抗性,对拟除虫菊酯类杀虫剂产生了21.0~267.2倍的抗性,对相对较新型杀虫剂（甲维盐、阿维菌素、茚虫威和溴虫腈）产生了5.2~53.4倍的抗性。经茚虫威汰选后第14代[抗性倍数(resistance ratio, RR)=26.43]斜纹夜蛾羧酸酯酶、谷胱甘肽S-转移酶和对硝基苯甲醚O-脱甲基酶活性分别上升2.86, 1.01和1.83倍。【结论】斜纹夜蛾对多种药剂产生了不同水平的抗性,斜纹夜蛾幼虫羧酸酯酶和对硝基苯甲醚O-脱甲基活性增强可能是斜纹夜蛾对茚虫威的抗性上升的重要因素。     

Location of ecdysteroid 22-O-acyltransferase in the larvae ofHeliothis virescens

Larvae of the tobacco budworm,Heliothis virescens, are resistant to high levels of ingested 20-hydroxyecdysone which could cause potential inhibition to the development of many other lepidopteran species. This resistance is attributed to the ability of the larvae to metabolize this molting hormone to its 22-acyl ester forms. When tobacco budworm larvae were fed large quantities of 20-hydroxyecdyone, the hormonal metabolites were found in gut and fat body tissues. When incubated with 20-hydroxyecdysone gut tissue converted 20-hydroxyecdysone into its 22-acyl ester metabolites. Lumen site of the midgut was found to be the major location of this bio-transformation. In contrast, fat body tissue failed to convert 20-hydroxyecdysone to 22-acyl ester metabolitesin vitro. After the oral injection of³H-ecdysone, the major metabolites formed were ecdysone 22-acyl esters whereas the majority of³H-ecdysone was transformed to polar metabolites after it was injected into the hemocoel of the larvae. Similar distributions of ecdysteroid 22-O-acyltransferase and alkaline phosphatase activity in subcellular fractions demonstrates the co-localization of these enzymes in plasma membrane of the gut epithelial cells. These results suggest that gut brush border membrane is the major site of ecdysteroid 22-acyl ester formation inH. virescens larvae.     

Suitability ofBusseola fuscaandSesamia calamistis(Lepidoptera: Noctuidae) for the Development of Two Populations ofCotesia sesamiae(Hymenoptera: Braconidae) in Kenya

The suitability ofSesamia calamistisHampson andBusseola fusca(Fuller) for the development of two geographical populations ofCotesia sesamiae(Cameron) was examined in the laboratory. One population of the parasitoid was collected from the coast of Kenya and the other from the inland. Both populations of the parasitoid could develop onS. calamistis.OnB. fusca,the inland population ofC. sesamiaewas able to develop, while the population from the coastal area of Kenya was encapsulated. Mating studies revealed that the two parasitoid populations were partially reproductively isolated. Unidirectional incompatibility, possibly caused by theWolbachiainfection, was observed when males from the infected coastal population were mated with females from the uninfected inland population.