Life history studies of <Emphasis Type="Italic">Prorops nasuta</Emphasis>, a parasitoid of the coffee berry borer

Life history studies were conducted in the laboratory on the African parasitoid Prorops nasuta Waterston (Hymenoptera: Bethylidae), a parasitoid of the coffee berry borer, Hypothenemus hampei (Ferrari) (Coleoptera: Scolytidae). The female wasp enters an infested coffee berry, kills the adult borer and seals the entrance of the berry with the body of the borer, impeding the entry of other organisms into the berry. The preoviposition period ranges from 3 to 14 days (mean 5.42 ± 0.37 SE). During this time females feed on the immature stages and paralyse fully grown larvae and pupae of the CBB. P. nasuta is an idiobiont solitary ectoparasitoid. Eggs are laid externally on the last instar larvae and pupae. Mean development time (egg to adult) for males and females was 27.7 (±0.37 SE) and 30 (±0.12 SE) days, respectively. Median survival for wasps fed on final instar CBB larvae was 27.7 days, significantly longer than any other treatment, while for females without food it was 2.5 days. In culture, females produced an average of 4.3 (±0.39 SE) progeny during their lifetimes. Adults began emerging at 30.6 days (±0.28 SE) after cultures were started and peak production was reached at 36 days, declining thereafter. Males normally emerged from coffee beans 2–3 days before females. Males usually emerged from 07:00 to 09:00h and females from 10:00 to 14:00 h. The culture sex ratio (proportion of males) was 0.21. Virgin females produced only male offspring.     

Life table and predation of Oligota pygmaea (Coleoptera: Staphylinidae) a major predator of the red spider mite, Oligonychus coffeae (Acarina: Tetranychidae) infesting tea

The staphylinid beetle, Oligota pygmaea (Solier) is an important predator of the red spider mite, Oligonychus coffeae (Nietner) infesting tea. Biology, life table and predatory efficiency of O. pygmaea were studied under laboratory conditions. Duration of developmental stages of O. pygmaea was 3.2, 5.7 and 12.5 d for eggs, larvae and pupae, respectively with an average of 23.0 d from egg to adult emergence. After a mean preovipostion period of 2.9 d, each female laid an average of 400.5 eggs in its life span. Adult O. pygmaea lived for an average of 54.1 d. Adult females lived for a longer period of 58.8 d compared to the longevity of 49.4 d of adult male. Studies revealed that its life table characterized by an intrinsic rate of natural population increase (r) of 0.118 d, net reproductive rates (R_o) of 243.693 eggs/female, gross reproduction rate (Σm_x) of 245.313 eggs/female, generation time (T) of 46.575 d, doubling time (DT) of 5.874 d and finite rate of increase (λ) of 1.125 d. Seasonal abundance of O. pygmaea and its prey, O. coffeae was monitored by sampling 25 tea leaves randomly from each experimental block grown under the prevailing field conditions. O. pygmaea showed a typical pattern of population dynamics with a peak during January to March and low incidence during June to September. Peak in the population of O. pygmaea coincided with the abundance of O. coffeae in the tea fields. Weather factors such as high temperature, low relative humidity and low sunshine hours adversely affected the populations of O. pygmaea. The first to third instar larvae of O. pygmaea consumed 31.0–133.2 eggs of mites per day. Third instar larva of O. pygmaea consumed an average of 133.2 eggs, 46.4 hexapod larvae, 39.6 nymphs and 11.4 adults per day. Adult females consumed more number of red spider mites compared to the males.     

Enhancement of supercooling capacity and survival by cold acclimation, rapid cold and heat hardening in Spodoptera exigua

Insects can increase their resistance to cold stress by prior exposure to non-lethal cold temperatures. Here, we investigated the supercooling capacity and survival of eggs, 3rd and 5th instar larvae, and pupae of Spodoptera exigua (Lepidoptera: Noctuidae) during CA, and responses to various pre-treatment protocols, including constant temperatures, thermoperiods, and RCH, RHH, RCH + RHH and RHH + RCH combined with thermoperiods. Only acclimated eggs demonstrated a significant decrease in SCP, from −20.7 ± 0.3 to −22.9 ± 0.3 °C, among all experimental groups compared to non-acclimated stages. Survival increased by 17.5% for eggs, 40.0% and 13.3% for 3rd and 5th instar larvae, and by 20.0% for pupae after CA. Compared to controls, survival of eggs under the conditions of thermoperiod (5:15 °C), thermoperiod (5:15 °C) + RHH, and thermoperiod (5:15, 10:20, and 15:25 °C) + RCH significantly increased. In addition, survival of 3rd and 5th instar larvae and pupae increased under the conditions of thermoperiod (5:15 °C) and thermoperiod (5:15 °C) + RCH, possibly due to the induction of heat shock proteins or cryoprotectants. However, the pre-treatments of thermoperiod + RCH + RHH and thermoperiod + RHH + RCH did not significantly enhance survival of any developmental stage. These adaptive responses may allow S. exigua to enhance supercooling capacity and survival in response to seasonal or unexpected diurnal decreases in environmental temperatures.     

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.     

Biology of the shore fly Scatella stagnalis in rockwool under greenhouse conditions

The development times and survival of immature stages in rockwool and the fecundity and longevity of adult Scatella stagnalis were determined and stage-specific life-tables constructed for the species at constant 20 and 25 °C and at a fluctuating temperature (23–34 °C, mean 28.5 °C). Development time from egg to adult decreased with temperature, being 15.9±0.1 days at 20 °C, 11.4±0.1 days at 25 °C and 10.1±0.2 days at fluctuating temperature with mean of 28.5 °C. The lower threshold for egg-to-adult development was 6.4±2.7 °C and the total quantity of thermal energy required to complete development was 212.8±.0 °C. The proportion of females in two populations studied was 0.521. High temperature increased the mortality of pupae from 7% (20 °C) and 10% (25 °C) to 29% at 28.5 °C. At 25 °C, female longevity was 15.5±0.7 days and fecundity 315±19 eggs/female (20.4 eggs/female/day). Males lived for 22.0±1.1 days. At constant 25 °C, the net reproductive rate was 126.1 female eggs/female, generation time was 18.4 days, the doubling time of the population 5.3 days, and the intrinsic rate of increase (r _m) 0.263 day^–1.     

Life table and predatory efficiency of Stethorus gilvifrons (Coleoptera: Coccinellidae), an important predator of the red spider mite, Oligonychus coffeae (Acari: Tetranychidae), infesting tea

The ladybird beetle, Stethorus gilvifrons, is a major predator of the red spider mite, Oligonychus coffeae, infesting tea. Biology, life table and predatory efficiency of S. gilvifrons were studied under laboratory conditions. Its average developmental period from egg to adult emergence was 19.2 days. After a mean pre-oviposition period of 5.3 days, each female laid an average of 149.3 eggs. Adult females lived for 117.3 days and males for 41.5 days. The life table of the beetle was characterized by an intrinsic rate of increase (r) of 0.066 day⁻¹, net reproductive rate (R ₀) of 72.2 eggs/female, gross reproduction rate (Σm _x ) of 82.3 eggs/female, generation time (T) of 64.9 days, doubling time of 10.5 days and finite rate of increase (λ) of 1.07 day⁻¹. Population dynamics of S. gilvifrons and its prey, O. coffeae, was monitored by sampling 25 tea leaves from each experimental block grown under the prevailing field conditions. Populations of S. gilvifrons reached a peak during January to March and had low incidence during June to November. Peaks in the populations of S. gilvifrons coincided with the abundance of O. coffeae in tea fields. Weather factors such as low temperature, high humidity and heavy rainfall adversely affected the populations of S. gilvifrons. The predatory efficiency of S. gilvifrons increased during the growth of larval instars. An adult female consumed 205.0 eggs, 92.2 larvae, 81.8 nymphs and 52.4 adult mites per day.     

Biology, rearing and field release on Guam of Euplectrus maternus, a parasitoid of the fruit-piercing moth, Eudocima fullonia

The eulophid parasitoid, Euplectrus maternus, is a gregarious ectoparasitoid of the larvae of thefruit-piercing moth, Eudocima (Othreis) fullonia. This parasitoid is indigenous to India and was released into Guam in 1998–99 to aid in the biological control of E. fullonia, an important pest of ripeguava, banana, mango, pomegranate, litchi,papaya, tomato, orange and other fruit crops.In the laboratory, biology and rearing of E. maternus on the larvae of E. fulloniawere studied. In no-choice tests, ovipositionby E. maternus was significantly greateron first and second instar larvae than on thirdinstar larvae. However, in free-choice tests,oviposition by E. maternus wassignificantly greater on second instar larvae,followed by first and third instar larvae. Thisparasitoid did not lay eggs on later instars,either in no-choice or free-choice tests.Females laid a significantly greater number ofeggs (>80%) on the dorsal surface of thelarvae than on either lateral or ventralsurfaces (1 to 8%). In general, more eggs werelaid on abdominal segments 1–3 on larvalinstars one to three. The survival of theimmature stages (from egg to adult) of E. maternus on second instar E. fullonialarvae was 61%, which was significantlygreater than the survival rates on first andthird instar larvae (32% and 26%), indicatingthat second instar host larvae are ideal formass rearing of the parasitoid. Mated femaleE. maternus continuously laid eggs on thesecond instar larvae of E. fullonia forup to 30 days, but the greatest number of eggswere laid during the first week after exposure.When E. maternus laid more than two eggson host larva, more female progeny wereproduced, indicating female-biasedreproduction. Adult parasitoids lived longerwhen fed with a honey: water (50% w/v)solution than with pure honey. Similarly, thefecundity of females increased significantlywhen fed with the honey-water solution whencompared to feeding with pure honey. To date,E. maternus has not established in Guam.     

Biology, life table and predation of Feltiella acarisuga (Diptera: Cecidomyiidae) feeding on Tetranychus cinnabarinus eggs (Acari: Tetranychidae)

Feltiella acarisuga (Vallot) is a common predatory gall midge, which feeds on many species of spider mites. All major life history and life table parameters of F. acarisuga were determined using the carmine spider mite, Tetranychus cinnabarinus (Boisduval) eggs as prey under laboratory conditions [26.7 ± 2 °C, 75 ± 5% RH, and a photoperiod of l4:10 (L:D) h]. Developmental times of F. acarisuga were 2.6, 7.1, and 6.7 d for eggs, larvae, and pupae, respectively, with an average of 16.4 d from egg to adult emergence. Female immatures development took ≈1 d longer than male immatures did. Adult F. acarisuga lived an average of 12.8 d, and the female adults (13.3 d) lived significantly longer than male adults did (11.9 d). After an average of 1.5 d preoviposition period, each female laid an average of 27.3 eggs in its life span with an average of 2.1 eggs per day and an average of 2.8 eggs on each of its oviposition day. The raw data were analyzed using an age-stage, two-sex life table method that takes into consideration of the variable developmental rates among individuals and between sexes. The intrinsic rate of natural population increase (r), net reproductive rates (R_o), gross reproductive rate (∑m_x), generation time (T), and doubling time (DT), and the finite rate of increase (λ) of F. acarisuga were estimated using the age-stage, two-sex (male and female) life table analysis as 0.122 d⁻¹, 16.19 eggs per female, 20.81 eggs per female, 22.81 d, 1.1298 d, and 5.7 d⁻¹, respectively. Each of the first, second, and third instar larvae of F. acarisuga consumed an average of 35.5, 54.0 and 86.9 T. cinnabarinus eggs per day, respectively. Larvae of F. acarisuga could consume an average of 175.4, T. cinnabarinus eggs, and female larvae consumed 14% more spider mite eggs (187.6 eggs) than male larvae (165.1 eggs). The significance of other life table parameters related to the population and the potential of using F. acarisuga as a biological control agent are discussed.     

Host-finding behavior, host acceptance, and host suitability of the parasiteXanthopimapla stemmator

Xanthopimpla stemmator (Thunberg)(Hymenoptera: Ichneumonidae), a solitary endoparasite of pupae of Old World lepidopteran stalkborers, was recently imported into Texas as a candidate for biological control of New World stalkborers. Information on host acceptability, host suitability and cues responsible for host finding were necessary to gain an insight into parasite/host interactions, because of the absence of a coevolutionary history.Xanthopimpla stemmator females were exposed to laboratory-reared one-to six-day-oldDiatraea saccharalis (F.) pupae. An average of 62% of host pupae were accepted and all ages of pupae were equally acceptable. Host suitability decreased with host age. One- to five-day-old host pupae averaged 31–37% suitability, whereas only 19% of 6-day-old pupae were suitable. Successful parasitization, defined as the product of the proportion accepted and the proportion suitable, decreased from 22–23% for 1-, 2- and 3-day-old pupae to 13% for 6-day-old pupae. Sex ratio (female:male) of the parasite progeny increased with host age. Females comprised 47% of total parasite progeny of 1-day-old and 84% of 6-day-old pupae. The increase in percent females was a result of a similar number of females in all age classes, coupled with a decrease in the number of males from older hosts.Xanthopimpla stemmator superparasitized 61% of acceptedD. saccharalis pupae in the laboratory. On dissection, 73% of host pupae with multiple probe wounds were found to contain parasite eggs or larvae; these hosts contained up to 10 eggs or 7 first-instar larvae. Increased numbers of probes by the parasites were associated with an increase in successful parasitization. Host seeking activity inX. stemmator was stimulated by the presence of larval frass, host odor and movement of host pupae. Results suggest thatX. stemmator is a good candidate for biological control ofD. saccharalis and possibly other factitious stalkborer hosts.     

Submergence tolerance in immature stages of the stalk-eyed fly Sphyracephala detrahens (Diptera: Diopsidae)

Sphyracephala detrahens (Walker, 1860) (Diptera: Diopsidae) inhabits the riparian zones of streams and rivers. Because of the limited dispersal ability of S. detrahens during egg, larval, and pupal stages, immature individuals are at risk of being submerged by floodwater after heavy rain. In this study, I evaluated the submergence tolerances of immatures of S. detrahens by comparing them to immatures of Drosophila melanogaster, which also feed on rotten fruits but are not restricted to the riparian zone. The results showed that S. detrahens eggs were susceptible to desiccation, but more than 80% of eggs hatched after full submergence. Later instar larvae were more resistant to full submergence than earlier instar larvae. The duration of submergence causing 50% pupation (PD₅₀) in the first, second, and third-instar larvae of S. detrahens were 15.88, 58.46, and 91.74 h, respectively. The PD₅₀ of the third-instar larvae of D. melanogaster was 20.01 h. Third-instar S. detrahens larvae continued to develop in water for a longer duration than D. melanogaster larvae of the same instar. In the pupal stages, late pupae tended to remain afloat longer than early pupae. The duration of submergence causing 50% emergence (ED₅₀) of adults from early and late pupae were 40.70 and 104.74 h, respectively. In the larval and pupal stages, individuals in the later developmental phases tended to be more tolerant to full submergence. The submergence tolerance of the immature stages of S. detrahens may reflect adaptation to an environment with fluctuating water levels.     

Acute toxicity and sub-lethal effects of a pyrethroid (cypermethrin) on survival,development and fitness of Helicoverpa armigera

The chickpea pod borer, Helicoverpa armigera (Hübner) is one of the most destructive pests of India and most of the countries. In this experiment, sub-lethal effects of cypermethrin were evaluated against sixth instar larvae of this pest that had ingested insecticide-treated chickpea pods. The LC₅₀, LC₃₀ and LC₁₀ values of cypermethrin were 80.38, 26.65 and 5.41?mg a.i.?L^?1, respectively, against sixth instar. The sub-lethal effects on fitness, eggs, larvae, pupae, adult longevity and reproduction were observed in H. armigera population that survived exposure to the sub-lethal doses of LC₅₀, LC₃₀ and LC₁₀ of cypermethrin. Survivorship was reduced to 36?days if H. armigera exposed to the sub-lethal dose of LC_50, whereas it was 42?days in unexposed groups. Larvae treated with LC₅₀ dose exhibit lowest intrinsic rate of increase (r_m) (0.0413 females/female/day) and highest (0.0517) with the unexposed group. Time taken by H. armigera to complete one generation (T_c) was 40.09?days, while this time significantly lowered to 32.85?days when exposed to the sub-lethal dose of LC₃₀. Hatching eggs were greatly reduced in the larvae exposed to cypermethrin at all the sub-lethal doses. About 430 eggs/female/generation were recorded after treatment with 80.38?mg/L as compared with untreated females (1390). Larvae that were exposed to sub-lethal concentrations of cypermethrin exhibited lower pupal weight and prolonged pupal developmental times compared control larvae. The overall fitness performance was better in the unexposed population as compared to the population exposed to sub-lethal doses.     

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。     

Regulation ofHelicoverpa zea larval behavior by the parasitoidEucelatoria bryani

The parasitoidEucelatoria bryani Sabrosky regulates the larval behavior of its hostHelicoverpa zea (Boddie). Parasitized third, fourth and fifth instars burrow into the soil 0.7–3.4 days earlier than unparasitized larvae that normally enter the soil to pupate at the end of the fifth and final larval instar. Parasitized third instars molt once then burrow as fourth instars, one instar earlier than normal. WhenE. bryani pupariated on the soil surface in the field, none survived to the adult stage. However,E. bryani adults emerged from 49.2% of hosts that had burrowed into the soil. By accelerating the timing ofH. zea burrowing behavior and causing host larvae to enter the soil before death,E. bryani ensures its pupariation in an environment with improved protection against natural enemies and lethal temperatures.     

Effects of gamma radiation on different developmental stages of the oriental tobacco budworm,Helicoverpa assulta (Lepidoptera: Noctuidae)

Ionizing radiation is increasingly used as an alternative to post‐harvest crop fumigation by methyl bromide. We studied the effects of gamma irradiation on Helicoverpa assulta (Lepidoptera: Noctuidae) at different stages of development to determine the minimal dose for the prevention of normal emergence of adults. We selected five doses of gamma rays (100, 200, 300, 400 and 500 Gy) based on preliminary experiments and irradiated eggs, larvae, pupae and adults. A dose of 100 Gy to eggs allowed 21.83% of larvae to pupate, but these all died during the pupal stage. A dose of 100 Gy to last‐instar larvae caused larval or pupal death, or the emergence of abnormal adults; no normal adults developed. Irradiation of pupae with doses of 300 Gy and above resulted either in their death or emergence of abnormal adults; however, after 100 or 200 Gy, normal adults emerged and F₁ eggs were produced, but no eggs hatched. Following irradiation of adults, eggs were produced at all doses, although the numbers were significantly decreased compared to untreated controls (P < 0.05; 69.45–125.50 vs. 475.05 eggs per female); however, none of the eggs hatched. As prevention of normal emergence is a key outcome for measuring the effectiveness of radiation, then the 100 Gy dose was effective for irradiation of eggs and larvae, and 300 Gy for pupae.     

Host selection and survival of the parasitoidEncarsia formosa on greenhouse whitefly,Trialeurodes vaporariorum, in the presence of hosts infected with the fungusAschersonia aleyrodis

Successful control of greenhouse whitefly may be achieved by complementary activity of the parasitoidEncarsia formosa and the fungusAschersonia aleyrodis. One way to obtain an additive mortality effect of both entomopathogen and parasitoid would be achieved by the selection of healthy hosts by the parasitoid and rejection of fungus-infected hosts. Third and fourth instar larvae ofTrialeurodes vaporariorum which had been treated with a spore suspension ofA. aleyrodis 0, 4, 7, 10 or 14 days beforehand, were presented to female parasitoids. The parasitoids adopted the oviposition posture on untreated hosts as well as on treated hosts, irrespective of the different stages of infection in the hosts. However, significantly more hosts were parasitized byE. formosa in the control treatment than in the fungal treatment. The parasitoids offered treated hosts, showed rejection behaviour after probing on hosts showing detectable signs of infection (containing hyphal bodies or mycelium in the haemolymph). For instance, when hosts were offered seven days after spore treatment, the parasitoids showed an oviposition posture on a total of 83 (95.4%) out of 87 infected larvae, but laid only 4 eggs (4.6%). In contrast, on 48 (94.1%) out of 51 noninfected (or showing no detectable signs of infection) hosts an oviposition posture was adopted and 40 eggs (78.4%) were found after dissection. When infected hosts were encountered the oviposition posture lasted less than 1′40″ while rejection of non-infected hosts occurred after more than 1′40″. Other experiments were carried out offering treated hosts for 24 h to the parasitoids. The hosts were dissected afterwards. Again, significantly more eggs were laid in the non-infected hosts. When hosts were parasitized shortly after fungal spore treatment they were colonized by the fungus and the parasitoids did not develop. Transmission of the entomopathogen after probing infected hosts was observed to a limited extent. In conclusion,A. aleyrodis andE. formosa can be used together in a glasshouse situation. The parasitoid will be most effective when introduced more than seven days after application ofA. aleyrodis, because from that time onwards it is able to detect and reject fungus-infected hosts.     

Fecundity,autogeny, and the larval environment of the pitcher-plant mosquito,Wyeomyia smithii

Summary Pupae and fourth instar larvae of a southern (30°N, Alabama, USA) population of Wyeomyia smithii Coq. (Diptera: Culicidae) were collected from pitcher plants. Adults which emerged were maintained without food then dissected to determine their egg clutch size. Among females which matured eggs, fecundities were negatively correlated with larval densities in individual pitchers. The mean autogenous fecundity of the overwintering generation did not differ from a summer sample. Adults unable to mature eggs comprised 6–39% of samples, depending on whether collected as pupae or fourth instar larvae. Fecundity was negatively correlated with time to adult eclosion among larvae maintained on unrenewed pitcher contents in the laboratory.Cohorts from this population were reared in artificial containers from egg hatch to adulthood at a single density and a superior or inferior diet. On the superior larval diet, all females survived to reproductive age, and all but one (>99%) produced eggs autogenously. On the inferior diet, survivorship to adult eclosion was significantly less, a high proportion of females died before reaching reproductive age, and only 19% of survivors matured eggs without blood. Protracted larval development induced by the inferior diet did not influence the probability of autogeny among females that survived to reproductive maturity.The relationship between larval environment and reproductive strategies is contrasted across the geographic range of W. smithii. Bloodfeeding occurs among southern populations where density dependent constraints on preimaginal growth are constantly severe. The loss of hematophagy among northern populations may have been facilitated by periods of density independent larval growth.Institute of Food and Agricultural Sciences, University of Florida, Experimental Station Journal Series No. 3645     

Physiological energetics of a midge,Chironomus riparius Meigen (Insecta,Diptera): normoxic heat output over the whole life cycle and response of larva to hypoxia and anoxia

The rate of metabolism of laboratory reared Chironomus riparius was monitored by direct calorimetry over the entire life cycle from egg to adult stage. The metabolic response of the fourth instar larva to decreasing oxygen concentrations and anoxia was also measured. Normoxic measurements were carried out at 20°C and the hypoxic-anoxic experiments at 10°C. In larvae with body sizes ranging from 0.0028 to 0.645 mg ash-free dry mass (afdm), the rate of heat dissipation was related to body mass by a power function, with a mass exponent of 0.71±0.02 corresponding to an exponent of -0.29 for the relationship between mass-specific metabolic rate and body mass. However, the allometric equations applicable to larvae would not predict the metabolic rates of eggs, pupae and adults. Single egg batches used in the experiments consisted of 354±90 eggs, the individual egg with a mass of 0.99±0.01 g (mean±SD). The mass-specific rate of heat dissipation of the egg (13.7±1.8 W mg^-1 afdm) was considerably lower than that of the first and second instar larvae (44–53 W mg^-1) but equal to that of fourth instar larvae (13.1±3.9 W mg^-1). Heat dissipation by a pupa shortly before adult emergence was high (14.8±1.8 W mg^-1), probably due to high metabolism during metamorphosis. Emergence of the adult in the calorimeter was indicated by a short but intense burst of heat. The newly emerged imago had a ca. 20–35% higher metabolic rate than the pupa. In response to reduced O₂ partial pressure the fourth instar larva of C. riparius displayed metabolic regulation. In continuously declining oxygen partial pressure, the fourth instar larva maintained its aerobic energy metabolism (4.2 W mg^-1) with only a small decrease down to 0.8 kPa, corresponding to an oxygen concentration of 0.42 mg O₂l^-1 H₂O. Below this critical oxygen concentration (P_c), the rate of heat dissipation decreased rapidly down to the anoxic level which was only 14–17% of the normoxic level. The high relative reduction of metabolic rate under anoxia gives a wrong impression of short-term tolerance of C. riparius to anoxia. The absolute energetic costs of C. riparius associated with anaerobic energy metabolism (0.64±0.11 W mg^-1) are almost 6 times higher than those of more anoxia tolerant invertebrates such as sphaeriid bivalves.     

Fecundity and oviposition ofEucelatoria bryani, a gregarious parasitoid ofHelicoverpa zea andHeliothis virescens

We examined longevity, fecundity, and oviposition strategies ofEucelatoria bryani Sabrosky (Diptera: Tachinidae), a gregarious endoparasitoid ofHelicoverpa zea (Boddie) andHeliothis virescens (F.) (Lepidoptera: Noctuidae). Longevity of adult femaleE. bryani was not related to body size. In contrast to longevity, largerE. bryani females had greater potential fecundity than smaller females, as determined by the number of embryonated eggs present in the common oviduct. However, female parasitoid size did not affect primary clutch size (number of eggs deposited in a host). Because embryos in eggs located in the ovisac were larger than those located elsewhere in the common oviduct, maximum primary clutch size may be physiologically limited by the number of fully mature eggs a female has available at one time.E. bryani females adjusted primary clutch size in response to host size, for bothH. zea andH. virescens. This adjustment appears to be adaptive because females did not overexploit hosts by depositing more larvae than a host could support. Adult emergence was not related to host size. Although host weight positively influencedE. bryani progeny weight, increases in progeny size with host size were counterbalanced by increases in primary clutch size with host size.     

The effect of temperature on development and fecundityof Scymnus levaillanti

Development and fecundity of Scymnus levaillanti(Mulsant) were recorded at fiveconstant temperatures ranging from 15 to 35 ± 1 °C in 5 °C increments, 60 ± 5% RHand 16 h of artificial light (5000 Lux). Developmentaltime (egg to adult) of S. levaillantisignificantly decreased with increasing temperatures,ranging from 63.9 days at 15 °C to 11.1 days at35 °C. Development from egg to adult required305.2 DD above a developmental threshold estimated as11.7 °C. Oviposition periods lasted 86.5, 76.1,47.2, and 31.5 days at 20, 25, 30 and 35 °C,respectively. No eggs were deposited at 15 °C.Higher temperatures resulted in shorter generationtimes (T_O) and in decreased net reproductiverates (R_O) of the coccinellid. S.levaillanti kept at 30 °C produced 0.151females/female/day, the highest per capita rate ofpopulation growth (r_m). The `functional response'of larvae and adults of S. levaillanti matcheswell that described by Holling (1959) as Type 2.Daily number of eggs deposited by females increased toa plateau with increasing prey density. Resultsobtained here provide information about the biology ofS. levaillanti, and its feeding capacityindicates that it may act as an important control agent.     

白蜡虫阔柄跳小蜂生物学特性的研究

白蜡虫阔柄跳小蜂Metaphycus ericeri Xu et Jiang在昆明地区一年发生5代,以3、4、5龄幼虫和蛹在白蜡虫雌成虫体内越冬。该蜂的发育起点温度和有效积温分别为11.45℃和552.93日度。18 ℃、21℃、24℃、27℃和30℃恒温条件下的平均世代历期分别为 66.87天、42.27天、35.56天 、30.84天和27.81天。成虫需取食蜜露或白蜡虫雌虫体液作补充营养。性比为1.75～2.88:1(平均2.25:1)。产卵前期2～3天。开始产卵后的2～5天产卵量占总产卵量的62.21%。 27℃的产卵量和产卵率分别为19.31粒和89.81%。18℃时仅4.37粒和18.56%。15℃时不产卵。补充营养、性别和产卵与否对成虫寿命有显著影响。幼虫共5龄。1～4龄以寄主体液和组织为食。5龄幼虫不取食,3～4天后化蛹。