Biological and immune response of Galleria mellonella (Lepidoptera: Pyralidae) to sodium tetraborate

Inorganic insecticides are commonly used in urban pest management because of their low mammalian toxicity. We tested the effects of sodium tetraborate (ST) on life parameters of greater wax moth, Galleria mellonella (L.) (Lepidoptera: Pyralidae), to determine its sublethal toxicity on the insect. Survival, development, adult longevity, and fecundity of the wax moth were investigated by rearing larvae on artificial diets containing ST at concentrations of 0.005, 0.1, 0.2, or 0.3%. Larvae reared on medium at the highest concentration of ST (0.3%) had significantly decreased survival to the seventh instar and prolonged time required to reach the seventh instar. This concentration reduced pupa and adult yields to 12.5%, and it also prolonged development by 5 d. ST did not significantly influence adult longevity. Dietary ST led to significant decreases in fecundity and egg viability. Oviposition of survivors at the highest ST concentration (0.3%) was completely inhibited. Lysozyme content was decreased in larval hemolymph and fat body at high dietary ST concentrations. Fat body lysozyme content was significantly increased two-fold for larvae reared on diet at the lowest concentration of ST (0.005%). However, the highest concentration (0.3%) dramatically decreased fat body lysozyme content from 0.12 +/- 0.013 to 0.006 +/- 0.003 mg/ml in seventh instars. We infer that sublethal levels of dietary ST substantially influence life history parameters and immunocompetence in G. mellonella.     

The effects of boric acid-induced oxidative stress on antioxidant enzymes and survivorship in Galleria mellonella

Larvae of the wax moth, Galleria mellonella (L.), were reared from first instar on a diet supplemented with 156, 620, 1,250, or 2,500 ppm boric acid (BA). The content of malondialdehyde (MDA, an oxidative stress indicator), and activities of the antioxidant enzymes [superoxide dismutase (SOD), catalase (CAT), glutathione S-transferase (GST), and glutathione peroxidase (GPx)] were determined in the fat body and hemolymph in the 7th instar larvae and newly emerged pupae. Relative to control larvae, MDA was significantly increased in larval hemolymph, larval and pupal fat body, but decreased in the pupal hemolymph. Insects reared on diets with 156- and 620-ppm BA doses yielded increased SOD activity but 1,250- and 2,500-ppm doses resulted in decreased SOD activity in larval hemolymph. SOD activity was significantly increased but CAT was decreased in the larval fat body. High dietary BA treatments led to significantly decreased GST activity. However, they increased GPx activity in larval hemolymph. Dietary BA also affected larval survival. The 1,250- and 2,500-ppm concentrations led to significantly increased larval and pupal mortality and prolonged development. In contrast, the lowest BA concentration increased longevity and shortened development. We infer that BA toxicity is related, at least in part, to oxidative stress management.     

Malathion-induced oxidative stress in a parasitoid wasp: effect on adult emergence, longevity, fecundity, and oxidative and antioxidative response of Pimpla turionellae (Hymenoptera: Ichneumonidae)

Effects of an organophosphorus insecticide, malathion, on survivorship and lipid peroxidation of the greater wax moth, Galleria mellonella (L.), pupae were investigated by rearing the newly hatched larvae on an artificial diet containing 0.01, 0.1, 1, 10, and 100 ppm of the insecticide. As bioindicators of long-term physiological stress responses, the adult emergence rate, longevity, and fecundity associated with lipid peroxidation level and antioxidant enzyme activity in the endoparasitoid Pimpla turionellae (L.) (Hymenoptera: Ichneumonidae) were determined by rearing the parasitoid on a factitious host, G. mellonella pupae treated with malathion. At 100 ppm, malathion significantly decreased pupation rate of G. mellonella larvae and the rate of adult emergence of the parasitoid from these pupae. This concentration resulted in a significant increase in the lipid peroxidation product malondialdehyde (MDA) in both the host and the parasitoid. Malathion at 1 and 10 ppm significantly increased pupation rate and lipid peroxidation level of G. mellonella pupae. The adult emergence rate of P. turionellae was significantly decreased from 63.7 to 20% by these concentrations, whereas MDA content was increased by two- and three-fold, respectively, compared with the control (45.3 +/- 3.2 nmol/ g protein). The longevity of adults was significantly extended from 52.5 +/- 5.7 to 75.7 +/- 6.3 d when the parasitoids emerged from host pupae exposed with 0.1 ppm malathion. At low concentrations (0.01 and 0.1 ppm), malathion significantly increased the number of eggs laid per female per day. However, the lowest concentration (0.01 ppm) had no significant effect on hatchability, whereas 0.1 ppm of the insecticide resulted in significant decrease in egg hatch compared with the control. A significant increase in total superoxide dismutase (SOD) activity for low concentrations of malathion (0.01-1 ppm) was found compared with the control. There was a significant positive correlation of SOD activities with adult longevity and fecundity. This study suggested that malathion-induced oxidative stress was causative factor in the deterioration of biological fitness and that increased SOD activities may have resulted in decreased oxidative damage, which retarded the rate of deteriorative physiological changes in P. turionellae in response to sublethal doses of malathion.     

Penicillin-induced oxidative stress: effects on antioxidative response of midgut tissues in instars of Galleria mellonella

Penicillin and other antibiotics are routinely incorporated in insect culture media. Although culturing insects in the presence of antibiotics is a decades-old practice, antibiotics can exert deleterious influences on insects. In this article, we test the hypothesis that one of the effects of dietary penicillin is to increase oxidative stress on insects. The effects of penicillin on midgut concentrations of the oxidative stress indicator malondialdehyde (MDA) and on midgut antioxidant enzyme (superoxide dismutase [SOD], catalase [CAT], glutathione S-transferase [GST], and glutathione peroxidase [GPx]) and transaminases (alanine aminotransferase and aspartate aminotransferase) activities in greater wax moth, Galleria mellonella (L.), were investigated. The insects were reared from first instars on artificial diets containing 0.001, 0.01, 0.1, or 1.0 g penicillin per 100 g of diets. MDA content was significantly increased in the midgut tissues of each larval instar reared in the presence of high penicillin concentrations. Activities of antioxidant and transaminase enzymes did not show a consistent pattern with respect to penicillin concentrations in diet or age of larvae. Despite the increased penicillin-induced oxidative stress in gut tissue, antioxidant and transaminase enzymes did not correlate with oxidative stress level or between each other in larvae of other age stages except for the seventh instar. We found a significant negative correlation of MDA content with SOD and GST activities in seventh instars. SOD activity was also negatively correlated with CAT activity in seventh instars. These results suggest that exposure to dietary penicillin resulted in impaired enzymatic antioxidant defense capacity and metabolic functions in wax moth larval midgut tissues and that the resulting oxidative stress impacts midgut digestive physiology.     

THE INFLUENCE OF DIETARY α‐SOLANINE ON THE WAXMOTH Galleria mellonella L

Plant allelochemicals are nonnutritional chemicals that interfere with the biology of herbivores. We posed the hypothesis that ingestion of a glycoalkaloid allelochemical, α‐solanine, impairs biological parameters of greater wax moths Galleria mellonella. To test this idea, we reared wax moths on artificial diets with 0.015, 0.15, or 1.5 mg/100 g diet of α‐solanine. Addition of α‐solanine to the diet affected survival of seventh‐instar larvae, pupae, and adults; and female fecundity and fertility. The diet containing the highest α‐solanine concentration led to decreased survivorship, fecundity, and fertility. The diets supplemented with α‐solanine led to increased malondialdehyde and protein carbonyl contents in midgut and fat body and the effect was dose‐dependent. Dietary α‐solanine led to increased midgut glutathione S‐transferase activity and to decreased fat body glutathione S‐transferase activitiy. We infer from these findings that α‐solanine influences life history parameters and antioxidative enzyme activities in the midgut and fat body of G. mellonella.     

INSECTICIDAL AND OXIDATIVE EFFECTS OF AZADIRACHTIN ON THE MODEL ORGANISM Galleria mellonella L. (LEPIDOPTERA: PYRALIDAE)

The insecticidal effects, specifically, changes in hemolymph total protein and malondialdehyde (MDA) levels, and antioxidant enzyme activities of azadirachtin (AZA) given to the wax moth, Galleria mellonella L. (Lepidoptera: Pyralidae) larvae via force feeding were investigated. Bioassays showed that the LD₅₀ and LD₉₉ (lethal dose) values of AZA were 2.1 and 4.6 μg/larva, respectively. Experimental analyses were performed with five doses of AZA (0.5, 1, 1.5, 2, and 3 μg/larva). Total protein level in larval hemolymph increased at all AZA doses at 24 h whereas a considerable decrease was observed at 2 and 3 μg/larva doses, and only an increase displayed at 1.5 μg/larva at 72 h. The level of MDA increased at 2 and 3 μg/larva doses at 24 h compared with controls. This trend was also observed at 1.5, 2, and 3 μg/larva doses at 72 h and MDA levels were lower when compared with those of 24 h at all doses except for 1.5 μg/larva dose. Catalase activity decreased at 1, 1.5, and 2 μg/larva doses at 24 h whereas increased at all doses except for 0.5 μg/larva at 72 h compared with controls. AZA led to a decline in superoxide dismutase activity at all experimental doses at 24 and 72 h except for 3 μg/larva doses at 72 h. An increase in glutathione‐S‐transferase (GST) activity was evident at all AZA doses at 24 h. AZA displayed 68% decline in GST activity at 72 h post treatments when compared to 24 h. Consequently, We infer that the toxicity of AZA extends beyond its known actions in molting processes to redox homeostasis.     

Biochemical stress indicators of greater wax moth exposure to organophosphorus insecticides

Although acetylcholinesterase (AChE) is the primary target of organophosphorus insecticides (OPs), increasing evidence regarding their secondary effects suggests that OPs disturb homeostasis of insects by generating free radical intermediates that trigger lipid peroxidation. We therefore investigated alterations in lipid peroxidation product, malondialdehyde (MDA) content, and alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activities, in conjunction with AChE activity as biochemical stress indicators in greater wax moth, Galleria mellonella (L.) larvae for OPs methyl parathion (MP) and ethyl parathion (EP). The effects of MP and EP were first investigated by rearing the young larvae on an artificial diet containing 0.01, 0.1, 1, 10, and 100 ppm of each insecticide. Second, the mature larvae were injected with 0.05, 0.5, 5, 50, and 500 ng of insecticides for determining the changes in biochemical stress responses. The diet with lowest level of MP significantly decreased the activities of all measured enzymes, whereas it increased MDA content. However ALT and AST were significantly higher in the larvae reared with the diet with high levels of MP than in control larvae. All tested levels of MP resulted in a decrease in AChE activity. The lowest level of EP in diet (0.01 ppm) significantly increased ALT activity, whereas it reduced that of AChE. This insecticide at 0.1 ppm resulted in reduced AST activity, but 1 ppm in diet elevated AST activity and MDA content. EP at 0.1 ppm and higher levels in the diet reduced ALT activity. All dietary EP levels significantly decreased AChE activity. ALT, AST, and AChE were lower in larvae fed with the diet containing 100 ppm ethyl parathion compared with larvae on control diet. MP at 50 ng per larva increased ALT and AST activities from 35.42 +/- 0.74 and 26.34 +/- 0.83 to 203.57 +/- 1.09, and 122.90 +/- 1.21 U/g, respectively, when the mature larvae were injected. All injected doses of EP dramatically reduced both ALT and AST activities, but only the lowest and highest levels of this insecticide decreased AChE activity. The lowest level of this insecticide also significantly increased MDA content in larvae. High levels of both insecticides increased MDA content. We observed a significant higher increase in MDA content in the larvae reared with 10 ppm EP (102.16 +/- 1.57 nmol/g protein) than the control group (30.28 +/- 1.42 nmol/g protein). These results suggest that OPs caused the metabolic and synaptic dysfunctions in greater wax moth and alter its biochemical physiology in response to oxidative stress.     

Effects of potassium levels over the range occurring in host plants on the growth of an insect herbivore (Manduca sexta)

Third instar tobacco hornworms (Manduca sexta L.: Sphingidae) on low dietary potassium had a lower relative growth rate than individuals on diets with potassium concentrations reflecting those in host-plants, due to decreased consumption rate, lower efficiencies of conversion of ingested and digested food (ECI and ECD), and a prolonged growth/feeding phase. Furthermore, these larvae, when placed on a diet with a moderate potassium concentration through the fourth stadium, ended up being smaller due to lower ECI and less biomass gained, and had a prolonged growth phase, which suggest an irreversible cost of the previous low potassium diet. Third instar hornworms on high potassium diets had lower ECI and ECD, and they had a prolonged growth phase. These individuals, when placed on a moderate potassium diet in the fourth stadium, gained less biomass, than those previously offered hostplant-like-potassium diets. Body potassium concentrations (% dw) at the end of the third stadium were similar among treatment groups. With increasing potassium concentrations in the diet, utilization efficiencies of potassium decreased and potassium concentrations in the frass increased. Correspondingly, water content (% fw) of the newly-molted fourth instar larvae declined with increasing potassium, indicating a passive loss of water during potassium excretion. Low and high dietary potassium reduced survivorship of third instar larvae; fourth instar caterpillars previously fed the low potassium diet also had poor survivorship. We conclude that, within the normal range of potassium concentrations in the hostplants, caterpillar performance is largely unaffected by potassium concentration, but that potassium-poor and potassium-rich diets, such as those hornworms may sometimes experience, can reduce growth and survivorship.     

POTATO LEAF EXTRACT AND ITS COMPONENT, α‐SOLANINE,EXERT SIMILAR IMPACTS ON DEVELOPMENT AND OXIDATIVE STRESS IN Galleria mellonella L.

Plants synthesize a broad range of secondary metabolites that act as natural defenses against plant pathogens and herbivores. Among these, potato plants produce glycoalkaloids (GAs). In this study, we analyzed the effects of the dried extract of fresh potato leaves (EPL) on the biological parameters of the lepidopteran, Galleria mellonella (L.) and compared its activity to one of the main EPL components, the GA α‐solanine. Wax moth larvae were reared from first instar on a diet supplemented with three concentrations of EPL or α‐solanine. Both EPL and α‐solanine affected survivorship, fecundity, and fertility of G. mellonella to approximately the same extent. We evaluated the effect of EPL and α‐solanine on oxidative stress in midgut and fat body by measuring malondialdehyde (MDA) and protein carbonyl (PCO) contents, both biomarkers of oxidative damage. We evaluated glutathione S‐transferase (GST) activity, a detoxifying enzyme acting in prevention of oxidative damage. EPL and α‐solanine altered MDA and PCO concentrations and GST activity in fat body and midgut. We infer that the influence of EPL on G. mellonella is not enhanced by synergistic effects of the totality of potato leaf components compared to α‐solanine alone.     

Boric acid-induced effects on protein profiles of Galleria mellonella hemolymph and fat body

The dietary effects of boric acid (BA) on the protein profiles of greater wax moth, Galleria mellonella (L.), were investigated in hemolymph and fat body of final instar (VIIth) and pupae. The insects were reared from first-instar larvae on an artificial diets containing 156, 620, 1250 or 2500 ppm of BA. We detected many undetermined protein fractions (6.5-260 kDa) in addition to well-defined protein fractions such as lipophorins and storage proteins in the tissues by using sodium dodecyl-sulphate polyacrylamide gradient gel electrophoresis. A marked quantitative change in the 45 kDa protein fraction of the hemolymph was observed in the VIIth instar larvae reared on 2500 ppm dietary BA.     

Effect of the Host Plant on the Antioxidative Defence in the Midgut of Lymantria dispar L. Caterpillars of Different Population Origins

THE RESPONSES OF GYPSY MOTH LARVAE ORIGINATING FROM TWO POPULATIONS (OAK FOREST, LOCUST FOREST) TO FAVORABLE (OAK) AND UNFAVORABLE (LOCUST) HOST PLANTS WERE MONITORED AT THE LEVEL OF MIDGUT ANTIOXIDATIVE DEFENCE: the activities of superoxide dismutase (SOD), catalase (CAT), glutathione-S-transferase (GST), glutathione reductase (GR), glutathione peroxidase like ('GSH-Px like') and glutathione content (GSH). Short-term change of the diet (3 days) to locust leaves of the 5th instar larvae (oak population) provoked an increase in GST and 'GSH-Px like' activities as well as in the amount of GSH. On the contrary, transferring the gypsy moth larvae (locust population) to oak leaves was followed by a decrease in GST, 'GSH-Px like' activities, and in the amount of GSH. Feeding gypsy moth larvae from hatching on an unfavorable host plant such as locust, led to increases in GST and SOD activities and GSH content, as well as to a decrease in CAT activity in all instars studied (4th, 5th, 6th). The locust leaf diet caused changes in other components of antioxidative defence dependent on larval instar and population origin, a feature which could be ascribed to trophic adaptation of the gypsy moth to an unfavorable host plant.     

紫茎泽兰粗提物对草地贪夜蛾生长发育及繁殖的影响

为明确紫茎泽兰粗提物对草地贪夜蛾生长发育及繁殖的影响,在实验室条件下分别利用4个不同稀释浓度（20、15、10、5倍）的紫茎泽兰粗提物处理玉米叶片后喂养草地贪夜蛾初孵幼虫,记录各虫态的发育历期、存活率、重量、成虫寿命以及后代性比、F2代卵孵化率、F2代卵的发育历期。结果表明,随着紫茎泽兰粗提物浓度的升高,草地贪夜蛾各虫态的发育历期延长,5倍稀释液处理下蛹的发育历期最长,达20.27 d,10倍稀释液处理下幼虫的发育历期最长,为21.46 d;随着处理浓度的增加,各虫态的重量逐渐降低,且存活率呈下降趋势,其中粗提物对蛹存活率的影响最大,对1~3龄幼虫存活率的影响较小;随着处理浓度的升高成虫的寿命均缩短,且雌成虫寿命长于雄成虫;随着处理浓度的升高,草地贪夜蛾的产卵前期和F2代卵发育历期延长,产卵期缩短;单雌产卵量、后代性比和卵的孵化率降低。总的来说,紫茎泽兰粗提物对草地贪夜蛾的生长发育及繁殖均造成消极影响。5倍稀释液对草地贪夜蛾的生长发育及繁殖的影响最显著,可作为草地贪夜蛾防治研究中的重要植物源杀虫剂材料。     

Changes of the Antioxidant Status and System of Generation of Free Radicals in Hemolymph of Galleria mellonella Larvae at Microsporidiosis

Changes of superoxide dismutase (SOD) and glutathione-S-transferase (GST) activities as well as of the content of SH-containing compounds were revealed in hemolymph of the native and the Vairimorpha ephestiae microsporidian-infected greater wax moth Galleria mellonella larvae. The SOD and GST activities in hemolymph of infected insects decreased at the stage of merogony, whereas during massive sporulation the enzymatic antioxidant activity in host tissues was higher than in control. By the ESR spectroscopy method, using the 1-hydroxy-3-carboxy-pyrrolidinespin-trap, generation of free radicals in hemolymph of infected insects was shown to decrease only at the stage of sporogony. The phenoloxidase activity in lymph was lower at acute microsporidiosis than in native larvae. The hemolymph concentration of thiol-containing proteins in infected insects did not differ from that in control. We suggest that decrease of generation of free radicals in hemolymph of the greater wax moth larvae at the stage of sporogony is due to a suppression of the prophenoloxidase system and an elevation of the antioxidant activity.     

Venturia canescens parasitizing Galleria mellonella and Anagasta kuehniella: differing suitability of two hosts with highly variable growth potential

Venturia canescens (Grav.) (Hymenoptera: Ichneumonidae) is a solitary larval koinobiont endoparasitoid, ovipositing in several larval instars of different pyralid moth species that are pests of stored food products. After oviposition, the host larva continues to feed and grow for at least several days, the precise time doing so depending on the stage attacked. We examined the relationship between host stage and body mass on parasitoid development in late second to fifth instars of two hosts with highly variable growth potential: the wax moth, Galleria mellonella (L) and the flour moth, Anagasta kuehniella (Zeller)(Lepidoptera: Pyralidae). G. mellonella is the largest known host of V. canescens, with healthy larvae occasionally exceeding 400mg at pupation, whereas those of A. kuehniella rarely exceed 40 mg at the same stage. Parasitoid survival was generally higher in early instars of G. mellonella than in later instars. By contrast, percentage adult emergence in A. kuehniella was highest in late fifth instar and lowest in late second instar. A. kuehniella was the more suitable host species, with over 45% adult emergence in all instars, whereas in G. mellonella we found less than 35% adult emergence in all instars. Adult parasitoid size increased and egg-to-adult development time decreased in a host size- and instar-specific manner from A. kuehniella. The relationship between host size and stage and these fitness correlates was less clear in G. mellonella. Although both host species were parasitized over a similar range of fresh weights, the suitability weight-range of A. kuehniella was considerably wider than G. mellonella for the successful development of V. canescens. However, in hosts of similar weight under 5 mg when parasitized, larger wasps emerged from G. mellonella than from A. kuehniella. Parasitoid growth and development is clearly affected by host species, and we argue that patterns of host utilization and resource acquisition by parasitoids have evolved in accordance with host growth potential and the nutritional requirements of the parasitoid.     

六种昆虫生长调节剂对葱蝇生长发育和繁殖力的影响

用灭蝇胺、氟铃脲等6种昆虫生长调节剂和对比药剂辛硫磷LC_40-50浓度处理葱蝇1龄和3龄幼虫,观察对其生长发育和繁殖的影响;并且研究了葱蝇成虫取食药剂对其繁殖力的控制效应。结果表明：6种药剂中除虫酰肼外,其余都对葱蝇幼虫发育历期、化蛹率、成虫产卵前期、成虫寿命、产卵量有很大影响,对其生长发育和繁殖表现出显著不利性。其中灭蝇胺和氟铃脲处理1龄幼虫后,存活幼虫的历期和成虫产卵前期各延长3天,化蛹率降低26.7%～30.0％,成虫寿命缩短22.3～24.3天,产卵量降低35.5％～49.9％;处理3龄幼虫主要导致产生畸形蛹,且正常羽化的成虫寿命降低18.0～20.67天,产卵量降低45.7%～57.8％。成虫连续取食用牛奶稀释的２ 000倍的药液,能导致产卵前期延长、产卵量减少、卵孵化率降低,幼虫死亡率极高,达95%以上。结果提示,利用成虫补充营养的特性,将灭蝇胺和氟铃脲等混入牛奶或糖水中诱集成虫取食,可有效降低成虫的繁殖力,有助于实现对葱蝇的无公害治理。     

EFFECT OF TEMPERATURE ON THE DEVELOPMENT AND REPRODUCTION OF BEMISIA TABACI B BIOTYPE (HOMOPTERA: ALEYRODIDAE)

Abstract The development, survivorship and reproduction of Bemisia tabaci B biotype on eggplant at seven constant temperatures (17, 20, 23, 26, 29, 32 and 35°C) were studied. The developmental periods from egg to adult varied from 48.7 days at 17°C to 13.9 days at 29°C and the developmental threshold estimated for a generation by linear regression was 12.4°C. The optimum temperature for B. tabaci population growth was 26°C, both extremely low (< 17°C) and high temperature (> 32°C) delayed the development. Survivorships from egg to adult was 67.3% at 26°C, 27.6% and 29.0% at 35°C and 17°C respectively. The average longevity of females ranged from 39.6 days at 20°C to 12.8 days at 35°C. Oviposition per female varied from 164.8 eggs at 20°C to 78.5 eggs at 32°C. Both the longevity and oviposition of B. tabaci females at different temperatures were significantly different ( P < 0.05), and the intrinsic rate of natural increase ( r _m) for B. tabaci at 29°C was the highest.     

High temperature determines the ups and downs of small brown planthopper Laodelphax striatellus population

Small brown planthopper, Laodelphax striatellus (Fallén) numbers usually drop sharply in the summer and revive quickly in the autumn. However, it is unclear whether and how the high temperature plays a role in this process. The effects of durations of heat exposure (33°C) on life‐history traits were examined here. Exposure of adults for 1 day during the oviposition stage led to a very low survival of nymphs. The average longevity of L. striatellus exposed for 1–31 days from oviposition was significantly longer than that of the control (27°C). Short‐term (1–5 days) heat exposure of the third instar nymphs did not significantly influence eclosion, but exposure of the fourth instar nymphs significantly increased eclosion. Lifespan from egg to adult was significantly lengthened when the third instar nymphs were exposed to heat for 2–15 days, or the fourth instar were exposed for 10 days. The preoviposition period was prolonged by heat exposure of the third or fourth instar nymphs. Short‐term heat exposure of less than 3 days of the third or fourth instar nymphs did not restrict fecundity, but when the exposure duration exceeded 5 days the total eggs per female and hatchability decreased. Exposure to high temperature increased the brachypter rate of adults. In summary, low survival and slowing development under heat exposure resulted in population decline in the summer, and the relatively high fecundity and brachypter rate led to quick revival in autumn. Temperature in the summer determines the rise and fall in numbers of L. striatellus.     

Insecticidal activities of garlic substances against adults of grain moth,Sitotroga cerealella (Lepidoptera: Gelechiidae)

Abstract The angoumois grain moth, Sitotroga cerealella (Olivier), is one of the most serious stored grain pests around the world. In attempts to reduce the losses caused by the moth and to suppress its populations, the fumigant activities, behavioral influence and ovipositional inhibition of garlic (Allium sativum) essential oil and its two major components, diallyl disulfide and diallyl trisulfide, were investigated against the adult grain moth. Their effects on reduction in survival of first instar larvae to adult emergence were also evaluated. Results showed that these three materials (garlic essential oil, diallyl disulfide and diallyl trisulfide) had significant fumigant activity with 50% lethal concentration values at 1.33, 0.99, and 1.02 μL/L air space, respectively; meanwhile, the three materials possessed high behavioral deterrent activities against adults in the Y‐tube olfactometer. When applied to rice grains, these materials reduced adult longevity and inhibited oviposition, with ovipositional inhibition above 70% at a concentration of 1.5 μL/25 g in either no‐choice or two‐choice tests. In short, the study showed that both diallyl disulfide and diallyl trisulfide, like garlic essential oil, acted as fumigants, produced behavioral deterrence and inhibited oviposition against angoumois grain moth. Our work here indicates that diallyl disulfide and diallyl trisulfide may serve as potential alternatives for grain protectants since both of them can be prepared easily from readily available chemicals.     

亚麻荠对小菜蛾幼虫取食和成虫行为反应的影响

亚麻荠是一种很少有害虫危害的油料作物。用室内生测和Y 型嗅觉仪研究了亚麻荠对小菜蛾Plutella xylostella幼虫取食和成虫行 为反应的影响。以甘蓝作对照,用亚麻荠叶片喂养的小菜蛾初孵幼虫3天后校正死亡率为79 .2%,显示了较强的致死作用;喂养小菜蛾3龄幼虫至化蛹,其存活率、化蛹率、蛹重及成 虫寿命都显著降低,表明亚麻荠对小菜蛾幼虫的生长发育有不利影响。在幼虫的取食选择实 验中,有甘蓝叶供选择时,小菜蛾幼虫不取食亚麻荠;在无可选择的情况下,小菜蛾幼虫也 取 食亚麻荠叶片,但取食量很小,与取食甘蓝叶的量相比,差异极显著。行为反应测试表明, 小菜蛾成虫对甘蓝和亚麻荠植株的挥发物都有明显的趋性反应,与对照（净化空气）相比, 差异极显著,而在甘蓝和亚麻荠之间无选择性。说明小菜蛾成虫对亚麻荠植株的挥发物具有 较强的定向反应。     

七星瓢虫雌成虫卵巢发育不同阶段体内保幼激素的含量

本文以大蜡螟Galleria mellonella(L.)为生测昆虫,应用蜡测定法(Wax test)测定了取食天然食物及人工饲料的七星瓢虫雌成虫在不同卵巢发育阶段体内保幼激素(JH)的含量。取食蚜虫者羽化后8日左右(卵巢管内出现第三卵母细胞,卵黄大量沉积即将排卵),雅虫JH含量达到高峰(593.3G.U.),但一经开始排卵(羽化后约10日左右)保幼激素的含量猛然下降。直至持续产卵达10次的雌虫(羽化后约25日)JH含量仍保持在比较平稳的状态。取食人工饲料者卵巢发育缓慢,羽化30日后不产卵个体的JH水平仍很低,仅及取食蚜虫组高峰的1/6。这一结果证实了JH对七星瓢虫雌成虫卵巢发育及排卵的调控,也指出了取食人工饲料的雌虫产卵率及产卵量明显偏低的重要原因。 在应用蜡测法的过程中肯定了JH浓度与大蜡螟蛾中胸背板保持的部分蛹皮面积之部的关系。