Age-dependent fecundity and life-fertility tables for Podisus nigrispinus (Dallas) (Het., Pentatomidae)

Abstract: The reproductive potential and longevity of Podisus nigrispinus (Dallas) were determined under laboratory conditions at a constant temperature of 25°C. The data were used to calculate life-fertility tables and rates of increase. The fecundity plateau of P. nigrispinus lasted 18 days, and during this period mean fecundity was 8.89 eggs per female per day. It started at the eighth day of age and ended at the 18th day of age. The declining fecundity period started at 18 days of age and ended with the death of the females. The female of P. nigrispinus oviposited a mean of 188.54 eggs, and had a mean longevity of 31.21 days. The gross reproductive rate (GRR) was 104.374 females/female; the net reproductive rate ( R _o) was 31.945 females/female; the generation time was 47.390 days; the doubling time was 9.480 days; the intrinsic rate of increase ( r _m ) was 0.073, and the finite rate of increase ( λ ) was 1.076. The predator population increased by 16.61 adult progeny per female per generation in the laboratory.     

Intrinsic rate of population increase of Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) according to climatic conditions and bean cultivar

Data on adult longevity, reproduction and intrinsic rate of population increase of insect parasitoid Amitus fuscipennis MacGown and Nebeker (Hym., Platygasteridae) were obtained under different climatic conditions on two bean cultivars. The insect host was the greenhouse whitefly Trialeurodes vaporariorum (Westwood) (Hom., Aleyrodidae). On cv. Chocho, at 19°C, 75 ± 5% RH and at 22°C, 70 ± 5% RH, mean longevity of adult Amitus females on the host insect was 9.3 and 5.7 days; mean fertility was 64.1 eggs and 52.7 eggs; and r_m values were 0.102 day^–1 and 0.144 day^–1 for the respective conditions. On cv. ICA-Pijao, at 19°C, 75 ± 5% RH, mean longevity was 15.2 days; mean fertility was highest (162.8 eggs); and r_m value was 0.117 day^–1. The r_m values of Amitus were higher than those of its host under the same test conditions. This parasitoid may therefore be a suitable candidate for use in inoculative or seasonal inoculative control programs against T. vaporariorum .     

Rearing and life table of reduviid predator Rhynocoris marginatus Fab. (Het., Reduviidae) on Spodoptera litura Fab. (Lep., Noctuidae) larvae

The tobacco armyworm, Spodoptera litura Fab., a serious pest of many cultivated crops was evaluated as prey for the reduviid predator, Rhynocoris marginatus Fab. The development, sex ratio, fecundity, hatchability and adult longevity of R. marginatus were investigated in the laboratory. Moreover, a life table was constructed for this predator. Observations clearly indicated that total developmental period of this predator was 46.71±1.58 days. In sex ratio, no significant difference was observed between male and female predators. The pre-oviposition period lasted for 18.64±0.76 days and it was 6.31 times shorter than the oviposition period. Female predators lived longer (128.04±8.48 days) than males (82.84±11.09 days). The total number of eggs laid per female predator in its life span was 405.28±22.15 eggs and the incubation period lasted for 6.81±0.10 days. Life-table studies showed that the intrinsic rate of increase was 0.063 female/day. The population multiplied 292.28 times in the cohort generation time of 103.933 days.     

Influence of temperature on life-table parameters of Stethorus gilvifrons (Mulsant) (Coleoptera: Coccinellidae) fed on Tetranychus urticae Koch

The influence of temperature on life-table parameters, fecundity and survivorship of the predatory ladybird, Stethorus gilvifrons , fed on Tetranychus urticae was determined at seven constant temperatures of 15°C, 20°C, 25°C, 28°C, 30°C, 35°C and 40°C. No development was observed at 40°C, thus being regarded as the threshold for the development of S. gilvifrons . The results indicate a significant decrease in male and female longevity with increasing temperature from 15°C to 35°C. The longest and shortest longevity were 18.40 and 12.75 days for males and 17.40 and 8.80 days for females, respectively. The intrinsic rate of natural increase ( r _m ) and the net reproductive rate ( R ₀) of S. gilvifrons linearly increased with increasing temperatures from 15°C to 35°C, while the mean generation time ( T ) and doubling time (DT) decreased linearly within this temperature range. The highest values of r _m (0.240 females/female/day) and R ₀ (59.27 females/female) and the lowest mean generation time (17.01 days) and DT (2.88 days) were recorded at 35°C. The maximum (185.50 eggs) and minimum (25.50 eggs) measurement of total fecundity was also recorded at 35°C and 15°C, respectively. The results indicate that temperature greatly affected fecundity, survivorship and life-table parameters of S. gilvifrons , and that 35°C is a suitable temperature for population growth of this predator.     

Age-specific survival and fecundity and their effects on the intrinsic rate of increase of Aphelinus gossypii (Hym., Aphelinidae), a parasitoid of Aphis gossypii (Hom., Aphididae)

Abstract: The age-specific survival and fecundity of female adults of the aphidophagous parasitoid, Aphelinus gossypii Timberlake (Hym., Aphelinidae), were determined at a host density of 50 Aphis gossypii Glover (Hom., Aphididae) per leaf of Ageratum houstonianum Mill each day at 25°C. The age-specific mummy production, emergence rate and sex ratio of progeny were calculated. The implication of these results in terms of potential population growth of A. gossypii and related species is discussed. The age-specific survival curve ( l _x ) of females exhibited a Type I pattern, which resulted in little difference between Σ m _x and Σ l _x   m _x . The l _x curve of males exhibited a Type II pattern, and their survival time was much shorter than that of females. Each mated female produced on average 598.9 ± 64.0 aphid mummies, and preyed on 87.9±6.2 aphids. Most of the biological performance parameters were not different significantly between mated and virgin females. The highly female-biased sex ratio of offspring produced by mated females soon after their emergence resulted in a high fecundity rate ( m _x ) during the early reproductive period. Therefore, although the sex ratio of progeny was male-biased during the entire reproductive period, the intrinsic rate of increase estimated using age-specific sex ratios was larger than that estimated using a constant sex ratio of 0.5. These results indicate that the high survival and the adaptation of producing mostly female offspring during the early reproductive period contribute much to the population increase potential of this parasitoid.     

Effect of temperature on life table parameters of Podisus nigrispinus (Het., Pentatomidae) fed with Alabama argillacea (Lep., Noctuidae) larvae

Abstract: The influence of temperature on life table parameters of Podisus nigrispinus (Dallas) (Het., Pentatomidae) fed with Alabama argillacea (Hübner) (Lep., Noctuidae) larvae was studied. This predator was kept at constant temperatures of 20, 23, 25, 28, 30 and 33±0.2°C, at relative humidity of 60±10% and photoperiod of L : D 14 : 10. Gross (GRR) and net ( R ₀) reproductive rates of P. nigrispinus ranged from 1.6 to 366.6 and from 0.02 to 189.5 females/female at temperatures of 33 and 28°C, respectively; generation time ( T  ) ranged from 33.3 (33°C) to 85.5 (20°C) days; doubling time ( D ) from 0.82 (33°C) to 17.8 (20°C) days; intrinsic rate of increase ( r _m ) from −0.13 (33°C) to 0.12 (28°C) per day; and the finite rate of increase ( λ ) from 0.88 (33°C) to 1.12 (28°C) females/female added to the population per day. The ideal age to release P. nigrispinus should be when this predator presents higher reproductive values (VR _x ); that is, its adults are about 7 days old, independent of prevailing temperature. Population growth of P. nigrispinus was affected by temperature with maximum numerical response between 28 and 30°C. The negative population growth shown at 33°C may not occur in natural conditions due to milder microclimate in the cotton agroecosystem and due to oscillations of temperature in the course of the day.     

Life history traits of Aphis gossypii Glover (Hom., Aphididae) reared on four widely distributed weeds

Variation in the life history traits of cotton aphids, Aphis gossypii Glover, reared on four widely distributed weeds, Ageratum houstonianum Mill., Bidens pilosa L. var. radiata Sch. Bip., Solanum nigrum L. and Spermacoce latifolia Aubl., were investigated. Cotton aphids were reared in the laboratory at 25°C. Each host plant had a distinct effect on aphid life history traits. Cotton aphids reared on S. nigrum had a significantly shorter developmental period, and age-specific fecundity peaked early. In contrast, cotton aphids reared on S. latifolia had a long developmental period and low age-specific fecundity. Cotton aphids that fed on B. pilosa and A. houstonianum displayed intermediate rates of growth and age-specific fecundity. Because the curves of age-specific fecundity ( m_x ) and age-specific net maternity ( l_x  m _x ) on each host plant were close together, development time and the pattern of age-specific fecundity were the major factors determining the population growth potential of the cotton aphid on each weed. As a result, the intrinsic rate of population growth for aphids reared on S. nigrum was significantly higher ( r_m =0.527 ± 0.011) than it was for aphids reared on S. latifolia ( r_m =0.194 ± 0.012).     

Side-effects of three neem (Azadirachta indica A. Juss) products on the predator Macrolophus caliginosus Wagner (Het., Miridae)

The side-effects of three neem formulations (Neem-Amin EC, Stardoor and B.P. 20/S) were tested on the mirid predator Macrolophus caliginosus Wagner in the laboratory. Direct toxicity tests on 1st instar nymphs exposed to fresh dry residues on glass plates at different doses demonstrated that all the products are harmful to the insects with LD₅₀ values much lower than the maximum recommended rate (1.217, 0.264, 1.083 mg a.i./l instead of 15, 31.5 and 80 mg a.i./l for Neem-Amin EC, Stardoor and B.P. 20/S, respectively). Moreover a reduction of fecundity of the surviving females was assessed with Neem-Amin EC and B.P. 20/S. Persistence tests were carried out on sharp pepper plants treated at the maximum recommended rate. High mortality was recorded when the insects were introduced onto the plants just after the treatment, but no significant differences compared with the controls were observed 5 days after the treatment and any consequence on the fecundity of surviving females was detected. Our experiments showed how azadirachtin can be noxious to M. caliginosus , but the short persistence makes this active ingredient a promising solution in integrated pest management programmes, when a lapse of time is guaranteed between the treatment and the introduction of the predator.     

Quality of two aphid species (Rhopalosiphum padi and Sitobion avenae) as food for the generalist predator Tachyporus hypnorum (Col., Staphylinidae)

Abstract:  The quality of two aphid species ( Rhopalosiphum padi and Sitobion avenae ) as food for the staphylinid generalist predator Tachyporus hypnorum was investigated. Fruit flies ( Drosophila melanogaster ) were used as prey for comparison. T. hypnorum has been reported to prey on aphids, to consume large quantities and to show a high preference for aphids. This study showed that compared with fruit flies aphids are not high-quality prey for neither adult females nor larvae of T. hypnorum . Larvae were less able to utilize aphids than adult females. Reproduction was affected by both aphid species; a diet of S. avenae reduced fecundity, and a diet of R. padi reduced egg hatching success and prolonged the time spent in the egg stage compared with a fruit fly diet. For the T. hypnorum larvae pure diets of both S. avenae and R. padi resulted in high larval mortality. Overall ranking of the three prey types based on several fitness parameters differed between larvae and adults. The adult fitness parameters gave rather conflicting rankings of all three prey types though the two aphid species were of approximately the same overall value, whereas the larval fitness parameters gave identical rankings: D. melanogaster  >  S. avenae  >  R. padi . In the larval stage survival was greatly reduced by both aphid diets, while this was not the case for the adult females.     

The biology of the mud-wasp Zeta abdominale (Drury) (Hymenoptera: Eumenidae)

The adult female nesting behaviour and biology of the neotropical mud-wasp Zeta abdominale (Drury) was studied in Jamaica. The cell-building behaviour was generally similar to that of Eumenes, but Zeta closed the apical funnel of the cell by moistening and re-moulding it into a plug. Each nest was built by a solitary female, who often built several small, mostly one-celled nests. Females efficiently used mud in cell-building, and small nests were advantageous, in needing less mud per cell and incurring a lower rate of predation than larger nests. Cellwall construction and provisioning were each completed in < 3 h, but a long pause between these activities, probably for feeding, delayed cell completion to 2.33 ± 1.0 days.
The number of active nesting females during a 10-h cycle was influenced by the time of day and weather. A relatively dense population had about 6.4 females ha^-1, whose age distribution, longevity and fecundity were estimated.     

Biological parameters of Thripobius semiluteus Bouček (Hym., Eulophidae), a larval endoparasitoid of Heliothrips haemorrhoidalis (Bouché) (Thysan., Thripidae)

Abstract:  The endoparasitoid Thripobius semiluteus Bouček was recently introduced to Italy from Israel for the biological control of Heliothrips haemorrhoidalis (Bouché). In this study, some aspects of the biology of T. semiluteus were determined in the laboratory. Developmental time (egg to adult), potential fecundity, realized fecundity, progeny, daily rate of deposition of eggs and several demographic growth parameters were evaluated. Studies of the longevity of fed and starved adults at seven temperatures (3, 10, 15, 20, 23, 25 and 30 ± 1°C) showed that fed T. semiluteus lived longest at 15°C (36.45 days) and shortest at 3°C (1.45 days). Longevity was reduced significantly at higher and lower temperatures than 15°C and when honey was not provided. Development time was measured at six temperatures. Pupae did not complete development at 10°C. The lower theoretical temperature threshold was 9.0°C; the optimum developmental temperature and the upper lethal threshold were 28.0°C and 34.1°C respectively. The most rapid development was found at 30°C, but waSPS suffered significantly higher mortality at this temperature than at other temperatures. Ovigeny index showed that T. semiluteus is synovigenic, with a mean realized fecundity of 78.8 eggs per female. The mean progeny was 68.2 adults per female on fed adults.     

Effect of delayed first feeding on development and feeding ability of Paralabrax maculatofasciatus larvae

The impact of delayed feeding early in development on late feeding ability and development of spotted sand bass Paralabrax maculatofasciatus larvae was examined. Larvae were sampled from hatching until day 19 after delayed feeding for zero (control), 1, 2, or 3 days. Feeding incidence was evaluated as the percentage of larvae with food in the gut and feeding intensity was measured by direct counting of prey after dissection of the gut. Delayed feeding effects due to starvation were observed early in development. By day 5, significant differences ( P  < 0·05) were observed between controls and larvae submitted to degrees of delayed feeding, including total length ( L _T), eye diameter, and the size of the head, liver, gut, muscles and body. Differences were still apparent in L _T, and body, liver and muscle heights at the end of the studied period. Larvae under total starvation did not survive beyond day 5. Initial feeding incidence was 35, 60, 90 and 10% for larvae first fed on day 2, 3, 4 or 5, respectively. Mean ±  s . d . feeding intensity was 3·6 ± 0·8, 2·8 ± 1·3, 5·2 ± 0·3, and 10·2 ± 1·5 rotifers per larva depending on whether larvae were initially fed on day 2, 3, 4 or 5, respectively. The point of no return occurred between 4 and 5 days after hatching.     

Evaluation of Serangium n. sp. (Col., Coccinellidae), a predator of Bemisia tabaci (Hom., Aleyrodidae) on cassava

Abstract  The potential of a new, previously unidentified Serangium species (Col., Coccinellidae) to control the high Bemisia tabaci (Gennadius) (Hom., Aleyrodidae) populations on cassava was evaluated. Field and laboratory studies were carried out to determine the abundance and feeding capacity of this Serangium species feeding on B. tabaci on cassava. Serangium nymphs and adults were most abundant in cassava fields late in the season, rising sharply from 5 months after planting (MAP) to a peak at 7–8 MAP. Pre-imaginal development averaged 21.2 days and was longest in eggs and shortest in the L₁ instar. Mean total prey consumption of immature Serangium increased with the stage of development with the lowest consumption in the L₁ instar and highest in the L₄ instar. Mean daily consumption was lowest on the first day after hatching in the L₁ instar and rose to a peak on the 13th day after hatching in the L₄ instar. Each Serangium larva consumed a mean of over 1000 nymphs during its entire development. These results have demonstrated the potential of this Serangium species to control B. tabaci populations on cassava.     

Development and reproduction of ‘B＇ biotype Bemisia tabaci （Gennadius） （Homoptera： Aleyrodidae） on four ornamentals

Abstract Effects of four commercial ornamentals on the development, survivorship and reproduction of the whitefly B biotype Bemisia tabaci (Gennadius) were studied in the laboratory (temperature 26 ± 1 °C; relative humidity 75%–90%; L: D 14:10). The total survivorship from egg to adult on hibiscus ( Hibiscus rosa-sinensis L.), poinsettia ( Euphorbia pulcherrima Will), cottonrose hibiscus ( Hibiscus mutabilis L.) and variegated leafcroton ( Codiaeum variegatum'Aucubaefolium' ) were 33.69%, 40.55%, 79.11%, and 29.39%, respectively. The developmental periods from egg to adult varied from 23.12 days on cottonrose hibiscus to 32.13 days on hibiscus. The average longevity of adult females ranged from 6.87 days on variegated leafcroton to 21.07 days on poinsettia. The average numbers of eggs laid per female were 9.20, 25.13, 54.45, and 26.79 on the above respective hosts. The intrinsic rates of natural increase ( r_m ) for B biotype B. tabaci on cottonrose hibiscus was the highest. Based on life table analyses of whitefly populations, cottonrose hibiscus was the most suitable host for B biotype B. tabaci in this study.     

Effects of Bt-toxin Cry1Ac on Propylaea japonica Thunberg (Col., Coccinellidae) by feeding on Bt-treated Bt-resistant Helicoverpa armigera (Hübner) (Lep., Noctuidae) larvae

Abstract:  Propylaea japonica is an important predatory insect of common cotton pests. To assess the ecological effects of transgenic Bt cotton, expressing Cry1Ac toxin, on this predator, we examined the life history parameters of P. japonica for two generations by feeding them with Bt-resistant Helicoverpa armigera . After ingesting Bt-treated Bt-resistant H. armigera larvae in the third and fourth instar, the body mass and body length of adult P. japonica decreased, a combined effect of poor prey quality and Cry1Ac Bt-toxin may account for these effects. However, larval survivorship and development in these two instars, pupal mortality, fecundity and adult longevity of P. japonica were not affected in both the generations. These results suggest that ingesting Bt-toxin Cry1Ac-treated pests in advanced larval stage might have no significant effect on the fitness of predator P. japonica .     

Effects of toxins from two strains of Verticillium lecanii (Hyphomycetes) on bioattributes of a predatory ladybeetle, Delphastus catalinae (Col., Coccinellidae)

Abstract:  The aim of this study was to test the hypothesis that the whitefly ( Bemisia tabaci ; Hom., Aleyrodidae) predator ladybird beetles, Delphastus catalinae (Col., Coccinellidae), are not adversely affected in the field by the crude insecticidal toxins extracted from two strains of the fungus Verticillium lecanii , V3450 and Vp28. We developed a method to evaluate sublethal toxicity and its effects on consumption and functional response of D. catalinae . The crude toxins have low toxicity against beetle larva with LC₅₀ values of 1942 (1393–2710) and 2471 (1291–4731) p.p.m., respectively (approximately 10- and 12-fold of field rate of application 200 p.p.m.). The adult beetles had less sensitivity to crude toxins with LC₅₀ values of 4260 (3376–5375) and 4426 (1734–11298) p.p.m., respectively (approximately 20- and 22-fold of field rate 200 p.p.m.). The consumption and foraging capacity were significantly impaired especially in the second-instar larval beetles which took longer time (more than twice of the control beetles) to consume whitefly eggs after exposure to toxins, although D. catalinae suffered no significant effect on fecundity and longevity, when exposed to a toxin dilution of field rate. The data suggest that spraying of V. lecanii or its toxins should be avoided in the field having immature stages of D. catalinae .     

Sex differences in movement between natural feeding and mating sites and tradeoffs between food consumption,mating success and predator evasion in Mediterranean fruit flies (Diptera: Tephritidae)

Summary Systematic quantitative observations of the location and diel pattern of adult Mediterranean fruit fly, Ceratitis capitata (Wiedemann), activities were carried out in an orange grove and surroundings on the island of Chios in Greece. Natural fly foods were assessed for their contribution to fly longevity, fecundity and fertility. There were diel shifts in male and female location. Females required a substantial and varied diet to realize peak fecundity. This diet was acquired away from the primary host, orange. Foraging for food throughout most of the day on fig and non-host foliage (including feeding on bird droppings) as well as on fig fruit and grapes, females dispersed and fed more than males. A diet of grapes alone did not support any fecundity, contributing only to longevity. A diet of figs alone, on the other hand, sustained both longevity and egg production. Bird feces alone supported neither egg production nor longevity. However, when added to a diet of figs, bird feces significantly increased fly fecundity. Throughout most of the day, males aggregated in leks within the inner canopy of the primary host, orange. The arrival here during the warmest hours of the day of receptive females, followed by pair formation, reinforced the lek mating system on host foliage. In the afternoon, females shifted to orange fruit where they suffered from high predation mortality while ovipositing. Soon after, males also shifted to orange fruit, where they attempted matings with non-receptive ovipositing females. Male feeding on fig fruit occurred late in the day, a time when they were least likely to find a mate. Male survival did not differ between the natural diets. Tradeoffs between food consumption, mating success and predator evasion are discussed for each sex and related to fruit fly mating systems.     

A microsporidian pathogen of the poroporo stem borer,Sceliodes cordalis (Dbld) (Lepidoptera: Pyralidae): Effects on adult reproductive success

Larvae of Sceliodes cordalis were infected over a range of ages and doses with Nosema sp. (NSC). The resulting spore loads in adults ranged from 9.3 × 10⁵ to 8.9 × 10⁷ spores and varied with the age of the larva at infection and with the dose ingested. Infection caused small reductions in female weight, mating success, potential fecundity, longevity, and egg viability. The magnitude of spore loads in female moths was not found to influence any of these factors apart from potential fecundity in very low weight moths. The cumulative effects of infection reduced natality in the laboratory colony from 11,400 to 6000 hatching eggs per 100 females. Laboratory reared, infected females were smaller, had a lower longevity, a reduced spore load, and were more fecund (eggs per milligram adult weight) than infected females from a field population. Manipulation of NSC in a biological control program is not considered to be of any value.     

Adult feeding and lifetime reproductive success in the parasitoid Aphytis melinus

The diet of adult females of the parasitoid Aphytis melinus DeBach (Hymenoptera: Aphelinidae) includes host insects and sugar-rich foods such as nectar and honeydew. We compared the contributions of host feeding to longevity and fecundity in A. melinus females in the presence and in the absence of honey meals. First, we assessed the longevity of females that were not allowed to oviposit. While the longevity of females fed honey was significantly increased by host feeding (median ages were 30.5 days for host-fed females and 17 days for females not allowed to host feed), the lifespan of parasitoids not fed honey did not exceed 3 days for any individual and there was no effect of host feeding on longevity in this group. In the second set of experiments, we assessed the fecundity and longevity of females allowed to oviposit. We conducted two experiments, one in which honey was continuously available, and one in which honey was not available. In both experiments, daily observations were made of females that were either allowed to host feed or manually prevented from host feeding. In the presence of honey, host feeding significantly increased both fecundity and longevity, and in the absence of honey, parasitoids died within 2 days and host feeding had no significant effect on either fecundity or longevity. The lifetime fecundity of females fed honey but not hosts exceeded the initial egg complement by 60% on average. Approximately one host per day was used for host feeding whether honey was supplied or not, and each host-feeding meal contributed approximately 3.9 eggs to the lifetime fecundity of honey-fed females. In the last experiment, we compared the rate of egg resorption over a 36-h period in A. melinus females that were deprived of hosts and either fed honey or starved. While no egg resorption was detected in honey-fed females over this time period, starved females resorbed approximately 9 eggs. Thus, the availability of a sugar-rich food interacts strongly with host feeding in influencing longevity and fecundity and has a strong direct effect on egg resorption.     

成虫取食对棉铃虫雌蛾繁殖的影响

试验对雌蛾设置５个食物处理,定量地研究了成虫取食对棉铃虫蛾繁殖和寿命的影响,成虫取食对雌蛾与寿命和主效量均显著影响,补充营养延长雌蛾寿命,提高产卵量,并且」补充营养对产卵量的影响比其对寿命的影响更大,分析表明被营养的作用在于提高雌蛾后期的存活率和产卵量,前期补充营养比后期补充营养具有更大的作用。雌雌全重及其蝮部干重受成廊和的自龄的双重影响,补充营养时雌蛾体重、腹部干重及其脂肪含量下降慢,补充营养可