Influence of larval food consumption on the fecundity of the lacewingChrysoperla carnea

The effects of food consumption on larval growth and development and adult fecundity of the common green lacewing,Chrysoperla carnea (Stephens), were studied on two populations of larvae derived from either a laboratory colony or from field-collected adults. The number of eggs of the Mediterranean flour moth,Anagasta kuehniella (Zeller), provided to individual lacewing larvae was varied to produce three food-supply treatments: low, intermediate, and high. Food-supply was found to influence larval growth and development and adult fecundity. Lacewing larvae provided with an overabundance of moth eggs developed faster than larvae provided with fewer moth eggs than they could have consumed. Adult females that developed from the high feeding treatment had a substantially shorter preoviposition period, a later decline in egg deposition, and a significantly higher fecundity than adults arising from the other feeding classes. Unrestricted feeding by adult lacewings on an artificial diet did not compensate for prior low feeding regimes. The overall performance of the lacewings derived from the laboratory colony was substantially poorer than that of the lacewings derived from field-collected adults. This effect was accentuated when the larvae were given a low food-supply. This overall decrease in vigor is attributed to inbreeding of the laboratory culture over a one year period. These finds are relevant to mass rearing programs for this biological control agent.     

Influence of spinosad on immature and adult stages of <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> (Stephens) (Neuroptera: Chrysopidae)

Toxicity of spinosad to immature stages of Chrysoperla carnea (Stephens) (Neuroptera: Chrysopidae) and its effect on the reproduction and survival of adult stages after direct spray and ingestion treatments were evaluated. Spinosad was harmless to C. carnea eggs and pupae irrespective of concentrations or method of treatments. Direct spray of spinosad to first instar caused significant reduction in rate of pupation and L1-adult survival, but did not affect the rate of adult emergence. Third-instar bioassay revealed significant difference in L3-adult survival. When C. carnea first instars were fed upon spinosad-treated-Brevicoryne brassicae (L.), significant differences in investigated parameters were not observed among different treatments. The weight of third instar and pupae were comparable regardless of tested spinosad concentrations. Also, feeding on spinosad treated-B. brassicae had no negative impact on fecundity and fertility. Furthermore, ingestion of spinosad contaminated-B. brassicae significantly prolonged larval and larval + pupal periods. The larval feeding capacity of C. carnea did not differ significantly between larvae fed on spinosad-treated and untreated aphids with the exception of first instar. When C. carnea adults were allowed to oviposit on spinosad treated-substrate, total number of eggs laid, percent of eggs laid on the treated substrate and egg hatching did not differ from those of control. However, when adults were fed on spinosad-treated artificial diet, negative effects on adult survival and fecundity were observed.

Biological and biochemical characteristics for quality control of Harmonia axyridis (Pallas) (Coleoptera, Coccinellidae) reared on a liver-based diet

Biological and biochemical parameters of a flightless strain of Harmonia axyridis, fed on a pork liver-based artificial diet and on Ephestia kuehniella eggs as controls, were compared. The diet-grown larvae showed a significantly longer developmental time and a lower adult emergence rate compared to control larvae. The weights of the newly emerged adults were significantly higher for adults fed E. kuehniella eggs during their larval stages than fed the artificial diet. In contrast, larval food source had no effect on the duration of the pre-oviposition period or adult longevity. For adults fed on E. kuehniella eggs as larvae, a significantly longer pre-oviposition period, lower daily weight gain and fecundity were found for the diet-fed females compared to those fed on E. kuehniella eggs throughout the life span. The adult food source had no significant effect on longevity and fertility. Lower amino acid and fatty acid contents (in particular C16:1 and C18:3n-3) were found for the prepupae and newly emerged females obtained from diet-reared larvae compared to controls. Deficiencies in fatty acids C16:1 and C18:3n-3 were also observed in females obtained from E. kuehniella egg-reared larvae and fed on diet from adult emergence. The analyses of the foods showed deficiencies in artificial diet, especially for some amino and fatty acids. The results suggest a non-optimal composition of the artificial diet and some possibilities for its improvement. However, this polyphagous predator could be reared from first instar larvae to fully reproductive adults on a pork liver-based artificial diet.     

Effects of pesticides commonly used in peach orchards in Brazil on predatory lacewing <Emphasis Type="Italic">Chrysoperla carnea</Emphasis> under laboratory conditions

Effects of the maximum field recommended concentration of five pesticides currently used on peaches in Brazil; abamectin, deltamethrin, methoxyfenozide, phosmet and trichlorfon were tested on the predator Chrysoperla carnea (Stephens) (Neuroptera, Chrysopidae). Dimethoate was used as positive standard. Three analytical laboratory tests, based on IOBC—working group pesticides and beneficial organisms guidelines were used: (1) exposure to fresh pesticide residue on glass plates of (a) larvae (susceptible life stage) and (b) adults (less susceptible life stage); (2) direct spraying of eggs and pupae; (3) exposure of larvae and adults to pesticide residues on plant leaves at different intervals after application (persistence). In tests 1, abamectin was slightly harmful to C. carnea larvae and phosmet and trichlorfon were slightly harmful and moderately harmful to C. carnea adults, respectively. After direct spraying of eggs and pupae, all the pesticides were harmless. In the persistence tests, abamectin and trichlorfon were classified as short lived and therefore they could be considered for use in Integrated Pest Management (IPM) programs under special conditions (i.e. reduced direct contact). Phosmet, however, caused between 56.3 and 75.0% mortality up to 30 days after treatment and it was rated as persistent. No sublethal effects were detected in the reproductive behaviour of adults (fecundity and fertility) compared with the control in any treatment. In conclusion, the insecticides with little or no toxicity to C. carnea such as abamectin, deltamethrin and methoxyfenozide could be considered as IPM-compatible, subject to further field studies.     

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。     

Evaluation of factors influencing augmentative releases of Chrysoperla carnea for control of Scirtothrips perseae in California avocado orchards

Weekly releases of Chrysoperla carnea for control of Scirtothrips perseae were evaluated in replicated field plots in two commercial avocado orchards in southern California, USA. Two release techniques and rates commonly employed by commercial pest control advisors who routinely use this generalist predator for S. perseae control were assessed. Release technique one utilized C. carnea eggs glued to paper squares that were stapled to leaves of experimental trees at a rate of 41,000 eggs per ha. Release technique two used a motorized backpack sprayer to apply a dry mixture of lacewing eggs and larvae to trees at a rate of 514,501 per ha. Pest populations were monitored by making bi-weekly population counts of S. perseae larvae and adults on leaves, and adult densities were simultaneously monitored in each experimental plot with yellow sticky cards. In the laboratory, degree-day accumulation until death of immature C. carnea was determined at temperatures representative of field conditions when predators were provisioned with varying amounts of food or different food types. Preference for S. perseae instars by first, second, and third instar C. carnea was assessed in the laboratory, and intraguild predation towards larvae and adult females of a co-occurring generalist predatory thrips, Franklinothrips orizabensis, was investigated along with intraspecific predation rates. Both release strategies failed to significantly reduce S. perseae populations in comparison to non-treated control plots. Approximately 35–96% of C. carnea eggs and larvae applied with the motorized sprayer landed on the ground. C. carnea larvae lived for approximately 1–2 days when provisioned with either no food, an avocado leaf or avocado pollen. Longevity was extended to 14–15 days when prey was provided. C. carnea larvae showed no preference for first or second instar S. perseae, all predator instars attacked first instar F. orizabensis, but only second and third instar C. carnea managed attacks on second instar F. orizabensis larvae. No adult female F. orizabensis were attacked and no attacks by F. orizabensis on C. carnea were recorded. Second instar C. carnea engaged in the highest levels of intraspecific predation.     

Assessing the utilization of a carbohydrate food source and the impact of insecticidal proteins on larvae of the green lacewing, Chrysoperla carnea

A concern with the widespread use of insecticidal transgenic crops is their potential to adversely affect non-target organisms, including biological control agents such as larvae of the green lacewing, Chrysoperla carnea (Neuroptera: Chrysopidae). Since the insecticidal proteins expressed by the current transgenic plants are active only after ingestion, dietary bioassays are required to test direct effects on non-target organisms. After showing that C. carnea larvae utilize carbohydrate foods, we exposed them to insecticidal proteins dissolved in a sucrose solution. Feeding on snowdrop lectin (Galanthus nivalis agglutinin, GNA) as a model compound, the larvae were negatively affected in a number of life-table parameters. Interestingly, GNA caused a prolongation in first instar development, but had no effect on subsequent utilization of prey resulting in an increased weight of second instars. Comparable studies with avidin, a biotin-binding protein, revealed strong effects on C. carnea survival at the concentration tested. Despite the fact that the proteolytic digestion of C. carnea larvae is reported to be dominated by serine proteases, ingestion of soybean trypsin inhibitor (SBTI) did not cause any detrimental effects. Similarly, two Cry proteins derived from Bacillus thuringiensis (Cry1Ac and Cry1Ab) did not cause negative effects on C. carnea, what is consistent with earlier studies. The here presented bioassay provides a valuable tool to assess direct impacts of insecticidal proteins to C. carnea larvae and other predators that are known to feed on carbohydrate solutions.     

Are fecundity and longevity of female Aphelinus abdominalis affected by development in GNA‐dosed Macrosiphum euphorbiae?

Abstract. Snowdrop lectin ( Galanthus nivalis agglutinin, GNA) confers partial resistance to several aphid species when incorporated into an artificial diet and/or expressed in transgenic potato. First-tier laboratory-scale experiments were conducted to assess the potential effect of GNA on the longevity and fecundity of female parasitoid Aphelinus abdominalis (Dalman) that had developed in Macrosiphum euphorbiae (Thomas) fed artificial diet containing 0.1% GNA (w/v). In a previous study it was shown that GNA ingested by A. abdominalis larvae is not acutely toxic. It was also shown that GNA has a host-size mediated effect on parasitoid sex ratio and larval development, but no apparent direct effect.         In this study, we report that A. abdominalis larvae that developed in GNA-dosed aphids that were smaller than control aphids of the same age, produced smaller adults with a reduced longevity and fecundity. Aphelinus abdominalis larvae that developed in GNA-dosed aphids older than the control but of the same size, produced adults of similar size that lived as long as the control but had a reduced fecundity.         Our results suggest that GNA fed to aphids in artificial diet has both a host-mediated effect (via aphid-size) and a direct effect on adult parasitoid fecundity. It is not known how GNA affects parasitoid larval development and subsequently adult fecundity, but it is hypothesized that GNA acted as an antifeedant to parasitoid larvae, thus disturbing nutrient assimilation and conversion necessary for egg maturation.     

Susceptibility of larval Crepidula fornicata to predation by suspension-feeding adults

The slipper shell snail Crepidula fornicata forms dense assemblages along much of the European coast, where it co-occurs with oysters. We examined the susceptibility of slipper shell larvae to predation by suspension-feeders, including adults of their own species. In particular, we compared filtration rates on phytoplankton with those on larvae, and determined the extent to which consumption of larvae varied with adult size, larval size, and with the presence of alternative food (phytoplankton). We also examined the ability of competent larvae to metamorphose successfully in the presence of feeding adults. For each experiment, adults were held in plastic jars with seawater or phytoplankton suspension and allowed to graze on larvae (101 larvae per jar) for 4-6 h at room temperature (21-23 °C); larvae were kept in circulation with gentle aeration. Adults of C. fornicata ingested substantial numbers of larvae over the complete range of sizes tested, about 450-850 μm shell length. Ingestion rates were reduced by 43-50% in the presence of phytoplankton, and were not correlated with adult shell length. The rates at which larvae were removed by adult slipper shells were generally lower than predicted from the rates at which the same adults ingested phytoplankton, suggesting either some ability of larvae to avoid capture or some difficulty of adults in consuming larvae entrained into their feeding currents. Slipper shell larvae were also readily consumed by adult oysters (Ostrea edulis and Crassostrea gigas), and indeed oysters consumed larvae at faster rates than predicted from their phytoplankton ingestion rates. Nevertheless, substantial numbers of competent larvae managed to metamorphose successfully during the test periods, either on the sides of the jars they were in or on the adults' shells, suggesting that recruitment probably continues in the field even when suspension-feeding adults are at high concentrations in the benthos.     

Use of maize pollen by adult Chrysoperla carnea (Neuroptera: Chrysopidae) and fate of Cry proteins in Bt-transgenic varieties

We investigated the use of maize pollen as food by adult Chrysoperla carnea under laboratory and field conditions. Exposure of the insects to insecticidal Cry proteins from Bacillus thuringiensis (Bt) contained in pollen of transgenic maize was also assessed. Female C. carnea were most abundant in a maize field when the majority of plants were flowering and fresh pollen was abundant. Field-collected females contained an average of approximately 5000 maize pollen grains in their gut at the peak of pollen shedding. Comparable numbers were found in females fed ad libitum maize pollen in the laboratory. Maize pollen is readily used by C. carnea adults. When provided with a carbohydrate source, it allowed the insects to reach their full reproductive potential. Maize pollen was digested mainly in the insect's mid- and hindgut. When Bt maize pollen passed though the gut of C. carnea, 61% of Cry1Ab (event Bt176) and 79% of Cry3Bb1 (event MON 88017) was digested. The results demonstrate that maize pollen is a suitable food source for C. carnea. Even though the pollen grains are not fully digested, the insects are exposed to transgenic insecticidal proteins that are contained in the pollen.     

The fate of vicilins, 7S storage globulins, in larvae and adult Callosobruchus maculatus (Coleoptera: Chrysomelidae: Bruchinae)

The fate of vicilins ingested by Callosobruchus maculatus and the physiological importance of these proteins in larvae and adults were investigated. Vicilins were quantified by ELISA in the haemolymph and fat body during larval development (2nd to 4th instars), in pupae and adults, as well as in ovaries and eggs. Western blot analysis demonstrated that the majority of absorbed vicilins were degraded in the fat body. Tracing the fate of vicilins using FITC revealed that the FITC-vicilin complex was present inside cells of the fat body of the larvae and in the fat bodies of both male and female adult C. maculatus. Labelled vicilin was also detected in ovocytes and eggs. Based on the results presented here, we propose that following absorption, vicilins accumulate in the fat body, where they are partially degraded. These peptides are retained throughout the development of the insects and eventually are sequestered by the eggs. It is possible that accumulation in the eggs is a defensive strategy against pathogen attack as these peptides are known to have antimicrobial activity. Quantifications performed on internal organs from larvae of C. maculatus exposed to extremely dry seeds demonstrated that the vicilin concentration in the haemolymph and fat body was significantly higher when compared to larvae fed on control seeds. These results suggest that absorbed vicilins may also be involved in the survival of larvae in dry environments.     

Insecticidal Properties of Bistrifluron,Benzoylphenylurea Insecticide,against Cotton Caterpillar,Palpita indica (Lepidoptera: Pyralidae)

In this study, we assessed the insecticidal properties of bistrifluron on the insect life stages of the cotton caterpillar, Palpita indicaa, with the primary emphasis on hatching rate, mortality, and susceptibility to chemicals, in addition to the preoviposition period, longevity, and fecundity. Bistrifluron exerted no effects on the egg. However, the larvae hatching from the eggs evidenced 100% mortality within 24 hrs. The susceptibility of P. indica to bistrifluron evidenced similar results at each larval stage. When bistrifluron was applied to the pupal stage, the chemicals significantly affected the longevity and fecundity of the normally emerging adults. The application of high concentrations of bistrifluron (50 ppm) to young adults delayed their pre-oviposition periods. In addition, the longevity, fecundity and hatching rate were attenuated.     

Characterizing indirect prey-quality mediated effects of a Bt crop on predatory larvae of the green lacewing, Chrysoperla carnea

There is increasing evidence that insecticidal transgenic crops can indirectly cause detrimental effects on arthropod predators or parasitoids when they prey on or parasitize sublethally affected herbivores. Our studies revealed that Chrysoperla carnea is negatively affected when fed Bt-susceptible but not Cry1Ac-resistant Helicoverpa armigera larvae that had fed Bt-transgenic cotton expressing Cry1Ac. This despite the fact that the predators ingested 3.5 times more Cry1Ac when consuming the resistant caterpillars. In order to detect potential differences in the nutrient composition of prey larvae, we evaluated the glycogen and lipid content plus the sugar and free amino acid content and composition of caterpillars fed non-Bt and Bt cotton. The only change in susceptible H. armigera larvae attributable to Bt cotton feeding were changes in sugar concentration and composition. In case of the Cry1Ac-resistant H. armigera strain, feeding on Bt cotton resulted in a reduced glycogen content in the caterpillars. The predators, however, appeared to compensate for the reduced carbohydrate content of the prey by increasing biomass uptake which caused an excess intake of the other analyzed nutritional compounds. Our study clearly proves that nutritional prey-quality factors other then the Bt protein underlie the observed negative effects when C. carnea larvae are fed with Bt cotton-fed prey. Possible factors were an altered sugar composition or fitness costs associated with the excess intake of other nutrients.     

Laboratory evaluation of the chemosterilant lufenuron against the fruit flies Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons

Four species of tephritid fruit flies, Ceratitis capitata, Bactrocera dorsalis, B. cucurbitae, and B. latifrons were evaluated for toxic, developmental, and physiological responses to the chemosterilant lufenuron. No significant mortality of laboratory strains of the first three species was observed after their exposure up to 50 μg/mL of lufenuron in agar adult diet, whereas B. latifrons adults fed with 50 μg/mL of lufenuron in the diet caused significant mortality compared to the control. Fertility of C. capitata adults fed on 50 μg/mL lufenuron-fortified diet between 7 and 12 days of age was approximately 46% of the no lufenuron control. Fertility of B. dorsalis and B. latifrons adults fed on 50 μg/mL lufenuron-incorporated diet was about 45% and 62% of the control, respectively. Lufenuron did not significantly affect fertility of B. cucurbitae adults. Lufenuron did not affect fecundity of C. capitata and B. dorsalis. Fecundity of B. cucurbitae and B. latifrons was not evaluated due to difficulty to count the eggs laid deep in the agar diet. Larvae fed on a liquid larval diet with ≤ 0.1 μg/mL of lufenuron were also evaluated. Pupal recovery, adult emergence, adult fliers, mating, egg hatch, and egg production of C. capitata were significantly decreased, while for B. dorsalis, pupal recovery, larval duration and adult emergence were affected. No effect of lufenuron on B. cucurbitae larvae was observed. B. latifrons was not performed because shortage of eggs at the time of this research. Lufenuron is a potential agent for management and control of C. capitata and B. dorsalis.     

Comparative Prey Suitability ofOstrinia nubilalisEggs andAcyrthosiphon pisumforColeomegilla maculata

The effects ofOstrinia nubilalis(Hübner) (Lepidoptera: Pyralidae) eggs andAcyrthosiphon pisum(Harris) (Homoptera: Aphididae), when provided as single prey species and in combination, on life history characteristics ofColeomegilla maculataDeGeer (Coleoptera: Coccinellidae) larvae and adults were quantified. Preimaginal development was not influenced by the larval prey regime; development at 26 ± 1°C was completed in approximately 13.5 days onO. nubilaliseggs,A. pisum,orA. pisumalternated daily withO. nubilaliseggs. The resulting adults weighed 13.0, 10.7, and 12.5 mg when reared onO. nubilaliseggs,A. pisum,andA. pisumalternated daily withO. nubilaliseggs, respectively. Eighteen percent of the individuals died when reared onA. pisum,28% died when reared onO. nubilaliseggs, and 22% died when fedA. pisumalternated daily withO. nubilaliseggs. Seven adult diet combinations, based on diet regimes of larvae and adults, did not cause significant differences in preoviposition period, interoviposition period, and the number of days on which eggs were laid. Total fecundity was influenced both by larval and adult diet. The diet that resulted in highly fecund females wasA. pisumalternated daily withO. nubilaliseggs for larvae andO. nubilaliseggs for adults. FemaleC. maculatafedO. nubilaliseggs had the highest intrinsic rate of increase and net reproductive rate.     

Relationship of flight and reproduction in beet armyworm, Spodoptera exigua (Lepidoptera: Noctuidae), a migrant lacking the oogenesis-flight syndrome

The beet armyworm, Spodoptera exigua, undertakes long-distance migration. We used flight mills to investigate the interaction between flight and reproduction in this species given the apparent absence of the oogenesis-flight syndrome. This syndrome, common in many migratory insects, is characterized by a suite of traits including migration during the pre-oviposition period followed by a switch to oogenesis. No negative effects of inter-ovipositional flight on lifetime fecundity were observed. Instead, adult reproductive output suffered when female flight was initiated the first day after eclosion and before oviposition, suggesting that migratory flight overlaps with the oviposition period rather than being confined to the pre-oviposition period. Mating status of both females and males had no negative influence on their flight performance except that flight distance and flight duration of 7-day-old mated females were significantly less than in unmated females. Furthermore, the number of eggs produced and mating frequency of females less than 7 days of age were not significantly correlated with flight performance, suggesting reproductive development paralleled and was independent of migratory behavior. This independent relationship between flight and reproduction of adults is consistent with the very short pre-oviposition period in this species, and suggests that resources are partitioned between these activities during pupal development. Together, our results uncovered neither obvious trade-offs nor mutual suppression between flight and reproduction in S. exigua, which indicates the lack of an oogenesis-flight syndrome for coordination of these two energy-intensive processes. We propose a conceptual model of migration for this species based on the current and previous studies.     

Interference and competitive behaviour of the aphid predators,Chrysoperla carnea andCoccinella septempunctata in the laboratory

Interference and competition betweenChrysoperla carnea (Stephens) andCoccinella septempunctata L. was investigated in the absence and presence of aphid prey. When larvae of similar vigour encountered each other,C. carnea larvae were superior toC. septempunctata. Otherwise the larger of 2 individuals always killed the smaller. In the absence of preyC. carnea adults were attacked by their own 2nd and 3rd instar larvae as well as by 3rd instar larvae ofC. septempunctata. In all encounters the adults ofC. septempunctata were superior. Since the eggs ofC. carnea are protected to some extent by being on egg stalks, they were less susceptible to cannibalism and predation thanC. septempunctata eggs which are deposited in batches directly on plant leaves. In the presence of prey cannibalism and predation were reduced, especially between larvae. Only eggs and 1st instar larvae were endangered. In the present experimentsC. carnea showed a slight superiority overc. septempunctata. Paper presented at the 17th International Congress of Entomology held in August 20–26 1984 in Hamburg, F.R. Germany.     

The consequences of egg cannibalism inAdalia bipunctata [Coleoptera: Coccinellidae]

When eggs ofAdalia bipunctata L. are offered to larvae of their own species, these larvae are able to develop to adults. Reducing the daily egg supply results in decreased larval survival and pupal weight and especially fecundity of the adult females. The duration of larval development is significantly increased, the longevity of adults is shortened.     

Functional response of Chrysoperla carnea (Neuroptera: Chrysopidae) to Helicoverpa armigera (Lepidoptera: Noctuidae): Effect of prey and predator stages

Abstract Understanding predator–prey interactions has a pivotal role in biological control programs. This study evaluated the functional response of three larval instars of the green lacewing, Chrysoperla carnea (Stephens), preying upon eggs and first instar larvae of the cotton bollworm, Helicoverpa armigera Hübner. The first and second instar larvae of C. carnea exhibited type II functional responses against both prey stages. However, the third instar larvae of C. carnea showed a type II functional response to the first instar larvae of H. armigera, but a type III functional response to the eggs. For the first instar larvae of C. carnea, the attack rate on H. armigera eggs was significantly higher than that on the larvae, whereas the attack rate of the second instar C. carnea on H. armigera larvae was significantly higher than that on the eggs. For the third instar larvae of C. carnea, the attack rate on the larvae was 1.015 ± 0.278/h, and the attack coefficient on the eggs was 0.036 ± 0.005. The handling times of the third instar larvae on larvae and eggs were 0.087 ± 0.009 and 0.071 ± 0.001 h, respectively. The highest predation rate was found for the third instar larvae of C. carnea on H. armigera eggs. Results of this study revealed that the larvae of C. carnea, especially the third instar, had a good predation potential in controlling H. armigera eggs and larvae. However, for a comprehensive estimation of the bio‐control abilities of C. carnea toward H. armigera, further field‐based studies are needed.     

Cholesterol oxidase: an oöstatic and larvicidal agent active against the cotton boll weevil,Anthonomus grandis

The enzyme cholesterol oxidase (E.C. 1.1.3.6), purified from Streptomyces culture filtrate was previously found to have oral insecticidal activity on neonate larvae of the boll weevil (Anthonomus grandis grandis Boheman) from a laboratory population. In the present study, second instar larvae were also controlled by the enzyme at diet concentrations similar to those which control neonates (12 day LC₅₀ = 2.4 μg.ml^?1 in diet). Larvae from field-collected adults were similarly susceptible to cholesterol oxidase in the diet. When ingested by adult females during the mating/pre-oviposition period, cholesterol oxidase greatly reduced subsequent oviposition (83% reduction in eggs laid as compared to controls) and larval survival (97% reduction from controls). Dissection of treated adult females revealed poorly developed ovaries and few developing oöcytes. These studies were conducted to further evaluate the utility of cholesterol oxidase in a program to establish boll weevil-resistant transgenic cotton.