Peak Oviposition Research Articles

Parasitisation activity of Spalangia cameroni and Muscidifurax zaraptor, pupal parasitoids of Musca domestica

AbstractThe house fly, Musca domestica L. (Diptera: Muscidae), is a significant pest in livestock farms and a major concern for both humans and farmed animals due to its ability to transmit over 200 pathogens. The use of pupal parasitoids is a sustainable strategy for controlling this pest. Spalangia cameroni Perkins (Hymenoptera: Spalangiidae) and Muscidifurax zaraptor Girault & Sanders (Hymenoptera: Pteromalidae) are commonly used as biocontrol agents for M. domestica. The objective of this study was to determine the oviposition peak of female parasitoids in relation to their age and the sex ratio of the adult progeny. For both species, 20 fresh M. domestica pupae (24–48 h old) were provided daily to each fertilised female for 14 days, after which the pupae were checked for parasitoid emergence. A control group of 20 pupae without female parasitoids was maintained. The results showed that S. cameroni had a higher overall percentage of parasitisation (57.7%) compared with M. zaraptor (32.4%). The parasitisation ratio of S. cameroni remained almost constant throughout the 14‐day period, whereas that of M. zaraptor decreased drastically after Day 11. Peak oviposition for S. cameroni was on Day 5 with 13 parasitised pupae per female, whereas M. zaraptor parasitised eight pupae per day on 4 days during its peak oviposition period (between Days 3 and 8). The newly emerged parasitoids had a skewed sex ratio towards females: 81% for S. cameroni and 66% for M. zaraptor. The presence of these parasitoid species resulted in fewer new house fly emergences than in the control group, where natural pupal mortality was lower in the absence of parasitoids. These findings may be useful for optimising the mass production and time‐use of the two parasitoid species for the management of house flies in livestock farms.

Benefits of remating of a hyperparasitoid acting as a biocontrol agent

Encarsia sophia is the dominant parasitoid of invasive whitefly pest such as Bemisia tabaci. This heteronomous hyperparasitoid species lays fertilised diploid eggs in whitefly nymphs, which serve as primary hosts. Larvae develop as female progeny by consuming whitefly hosts, providing direct biocontrol benefits. However, male progeny originate from unfertilised eggs laid on secondary hosts (primary parasitoids within whitefly nymphs) and develop by consuming primary parasitoid larvae rather than whitefly hosts. Therefore, it is crucial for indoor rearing and field release of the hyperparasitoid to determine whether a female with single-mating experience can parasitise primary hosts and produce female progeny for a whole lifetime and, if not, whether it is remating events and prolong the period of female production, thereby increasing the amount of parasitism on whiteflies. Our fecundity experiments of females with single-mating experience, equally provided with primary and secondary hosts, showed that single mating was insufficient for E. sophia females to lay fertilised eggs in whitefly nymphs for their whole lifetime. In multiple mating experiments, 76.7 % of male adults completed their second mating 2 h after the first, whereas female adults accepted the second mating only if primary hosts were available thereafter. Remating was beneficial for female adults as it prolonged the ovipositional period of fertilised eggs (from 13.3 ± 0.6 days for single to 17.1 ± 0.7 days for twice mating) and increased parasitism on B. tabaci primary host (from 53.1 ± 3.8 for single to 76.4 ± 5.9 for twice mating respectively). The mating experience of males increased their copulation success, whereas that of females decreased it. In conclusion, recommendations are provided for large-scale indoor rearing and field release of E. sophia. Firstly, sufficient time for providing males can be shortened to within 2 h, and a single male can engage in 2–3 mating sessions. Following the 15-day peak oviposition period, the addition of newly emerged males is advised. Secondly, for field release of adult parasitoids, it is recommended to concentrate on releasing females after completing mating indoors. For the release of pupae cards, ensure a balanced ratio of males and females on each card to facilitate mating upon emergence. Additionally, release extra males and females 2 weeks after the initial batch of releases.

Oviposition biology and seed damage by Smicronyx lutulentus Dietz (Coleoptera: Curculionidae), a biological control agent of Parthenium hysterophorus L. (Asteraceae) in South Africa

The seed-feeding weevil Smicronyx lutulentus Dietz (Curculionidae) was released in South Africa in 2015 to supplement the biological control programme against the invasive annual weed Parthenium hysterophorus L. (Asteraceae). Larval feeding within young, developing ovules and larval-induced abortion of adjacent seeds within the flowerheads causes seed destruction, augmenting low levels of natural seed abortion. We studied female fecundity in a glasshouse trial, to identify critical periods in oviposition and inform mass-rearing and field release protocols. Newly emerged mated females displayed a pre-oviposition period of 1–2 weeks, a peak in oviposition after 7–8 weeks and a lifetime fecundity of 324–446 eggs. We also studied the relationship between weevil density and seed damage during two separate glasshouse trials, to facilitate predictions of seed damage under field conditions. Plants exposed to 15 mating pairs of weevils harboured substantially higher proportions of larval-damaged flower buds (75 %) than plants with five pairs (45–56 %) or a single pair (19 %). Larval progeny from five adult pairs caused significantly higher seed inviability (38 %) than progeny from a single pair (14 %), versus the weevil-free control (5 %). Progeny from 15 pairs damaged 30 % of developing seeds, potentially causing up to 60 % seed inviability due to enhanced abortion of neighbouring seeds. Although ≥5 females per plant caused appreciable seed damage, the proportions of unexploited new buds (25–55 %) versus buds with multiple occupancy (≥2 larvae; 35–47 %) indicate the importance of floral phenology in oviposition site selection, as flowerbuds of 2–3 mm are preferred. Although progeny from five females per plant could cause up to 30 % seed reduction, within a week of oviposition, higher densities are required to limit the entry of viable seeds into the soil seed banks.

MiR-2940-1 is involved in the circadian regulation of oviposition in Aedes albopictus.

The vast majority of all global species have circadian rhythm cycles that allow them to adapt to natural environments. These regular rhythms are regulated by core clock genes and recent studies have also implicated roles for microRNAs in this regulation. Oviposition is an important circadian behavior in the reproductive cycle of insect vectors of diseases, and little is known about the rhythm or its regulation in mosquitoes. Aedes albopictus is a diurnal mosquito that transmits arboviruses and is the major cause of outbreaks of dengue fever in China. We analyzed the oviposition rhythm patterns of A.albopictus under different light/dark conditions and show that the mosquitoes have an oviposition peak between zeitgeber time9 (ZT9) and ZT12. Furthermore, the antagomir-mediated knockdown of expression of the microRNA miR-2940-1 affected the oviposition rhythm of A.albopictus. These data support the conclusion that miR-2940-1 is involved in the regulation of oviposition rhythm in A.albopictus and provide a foundation for using oviposition rhythms as a new target for vector mosquito control.

Seasonal differences in amounts of oviposition habitat and egg‐laying by caddisflies in rivers with regulated versus unregulated flows

Abstract Few studies consider spatio‐temporal variation in egg‐laying for benthic insects in streams. However, such variation can have lasting effects on the numbers and distribution of offspring and subsquent life‐cycle stages. For species that require specific egg‐laying habitats, such as rocks that protrude from the water surface (emergent rocks, ER), densities of egg‐laying habitat can affect densities of benthic eggs and even larvae for some species. For such species, changes in water levels alter the spatio‐temporal distribution of ER and can affect densities of eggs and, potentially, larvae. Below dams, modified flow regimes may alter the temporal availability of ER. In this study we tested whether river regulation altered the availability of oviposition habitat and changed the phenology of oviposition compared to unregulated rivers. At multiple sites in two regulated (Murrumbidgee, Tumut) and three unregulated (Goobarragandra, Goodradigbee, Micalong) rivers (south‐east Australia), we surveyed densities of ER and egg masses of five species of caddisflies (family Hydrobiosidae) seasonally over 3 years (2019–2021). Samples of adults also were collected during two seasons using light traps. High flows in both regulated rivers submerged all rocks during spring and summer and low‐flow releases stranded rocks above the waterline at all (Murrumbidgee River) or most (Tumut River) sites during autumn and winter. No ER or egg masses were observed on any date in the Murrumbidgee River, despite relatively large catches of adults. On the Tumut River, low densities of ER and egg masses were twice observed at one site, during seasons (winter, autumn) when oviposition was low in the unregulated rivers. In unregulated rivers, ER and egg masses (five species, four genera) were present at all sites but with lower densities in winter than in other seasons. During peak oviposition periods, densities of egg masses per site were not strongly related to densities of ER. In summer 2019, ER in two unregulated rivers were blanketed by sheets of algae and sediment that appeared to prevent oviposition because no egg masses were observed at this time. In regulated rivers, aseasonal flows precluded egg‐laying by submerging (summer, autumn) or stranding (winter, spring) all or most ER. In contrast, ER were available all year in the unregulated rivers and egg‐laying occurred all year, except when ER were blanketed by algae and sediment. Within seasons, local densities of egg masses may be limited by numbers of gravid females, rather than numbers of ER, which differs from previous research. Identifying impediments to reproduction is critical to understanding variability in population numbers in natural and altered systems. Our observations of oviposition failure downstream of dams present a new hypothesis for why some insect species are absent from channels where flows are regulated for irrigation. Blankets of algae may similarly preclude reproduction in rivers with low‐flow conditions, but this remains untested.

Laboratory evaluation of the compatibility of Beauveria bassiana with the egg parasitoid Trichogramma dendrolimi (Hymenoptera: Trichogrammatidae) for joint application against the oriental fruit moth Grapholita molesta (Lepidoptera: Tortricidae).

The entomopathogenic fungus Beauveria bassiana and the egg parasitoid Trichogramma dendrolimi can both contribute to biological control of the global fruit borer Grapholita molesta. To derive insights for optimizing their combined application in augmentation programs, we assayed fungal pathogenicity to both G. molesta (eggs, larvae and adults) and adult parasitoids, and assessed wasp acquisition and transmission of fungal spores following their emergence from B. bassiana-treated host eggs. Concentrations of 108 conidia mL-1 of B. bassiana and higher caused virtually complete mortality of G. molesta larvae, but less than 30% mortality of eggs, and female moths surviving treatments had reduced fecundity. More than 80% of adult T. dendrolimi survived B. bassiana treatments of 107 conidia mL-1 , and more than 60% survived 109 conidia mL-1 , with surviving females achieving reproductive success equivalent to controls. Parasitoid females preferred healthy eggs over B. bassiana-infected ones in choice tests; wasps emerging from treated eggs carried about 104 conidia each and contributed an additional 11% host mortality in trials combining both agents. Our results indicate that combined applications of B. bassiana and T. dendrolimi can have complimentary impacts on G. molesta, the wasps compensating for low fungal pathogenicity to eggs and their progeny potentially aiding in subsequent disease transmission. Although foraging wasps tended to avoid infected eggs, negative interactions between the two agents might be further mitigated by timing B. bassiana applications from late instar larva to early moth stage, and T. dendrolimi releases several days later to coincide with peak oviposition periods. © 2022 Society of Chemical Industry.

Effect of weather parameters on the seasonal dynamics of tobacco caterpillar, Spodoptera litura (Lepidoptera: Noctuidae) in castor in Telangana State

Field experiments were carried out for four years (2012-13 to 2015-16) to study the seasonal dynamics of tobacco caterpillar, Spodoptera litura in castor and its relationship with different weather parameters during kharif season in Telangana State. Moth catches of S. litura were observed throughout the crop season, wherein maximum catches (44.8 to 124 moths/trap/week) were observed during mid- August to late-October [33rd to 43rd Standard Meteorological Week (SMW)]. Peak oviposition (2.0 to 14.8egg-masses/5 plants) and larval incidence (14.4 to 48 larvae/5 plants) of S. liturawas recorded during mid-August to mid-November (33rd to 46th SMW) coinciding with the vegetative to primary spike development stage of the crop. The correlation analysis indicated that the moth catches and larval population of S. litura showed significant positive correlation with weather parameters viz., maximum temperature, minimum temperature, rainfall and rainy days, while egg-masses of S. litura showed significant negative correlation with morning relative humidity and minimum temperature.The stepwise regression analysis revealed that minimum temperature, rainy days, wind speed and evening relative humidity could explain 64 per cent variation in S. litura moth catches. Among all the variables morning relative humidity was found to contribute significantly and showed 59 per cent effect on the population fluctuation of eggmasses, while rainy days and maximum temperature could explain 51 per cent variation in larval population of S. litura in castor.The models were validated with independent data 2015-16. The overall results suggested that the models can be used for predicting the population of S. litura in castor for optimizing management strategies.

Life cycle of the tick, Haemaphysalis (Kaiseriana) bispinosa (Acari: Ixodidae) under laboratory conditions

ABSTRACT Haemaphysalis (Kaiseriana) bispinosa is one of the widest–spread tick species in Southern Asia vectoring pathogens to wildlife and livestock animals. Understanding biological parameters of this species is of great importance, particularly when setting control plans or for epidemiological studies under laboratory conditions. The aim of this study was to figure out the biological aspects of H. (K.) bispinosa under laboratory conditions. Three continuous generations of this tick have been recorded. The study resulted in overall means of 10.6 ± 2.46, 8.7 ± 2.68, and 14.6 ± 2.39 days for pre-oviposition period, oviposition, and egg incubation, respectively. Larvae needed means of 4.10 ± 1.24 and 7.50 ± 1.57 days for feeding and pre–moulting periods, respectively, whereas nymphs required means of 5.10 ± 1.32 and 10.90 ± 2.39 days for feeding and pre–moulting periods, respectively. Adult females engorged for a mean of 8.0 ± 0.79 days. The entire life cycle averaged of 71.0 ± 12.0 days. Adult females weighted an average of 47.6 ± 14.8 mg, which produced egg masses that averaged 10.9 ± 3.5 mg. The oviposition rate was 557 ± 179.1 eggs/female with a peak oviposition on day 4. Hatchability rate with an average of 94.3 ± 2.19% was recorded. Significant linear correlations between weight of engorged females and weight of egg mass, and with number of eggs laid were recorded (r = 0.90; P > 0.01; r = 0.89; P > 0.01, respectively). The life cycle of this tick species was ambiguous over the past, and finally has been cleared; therefore, it could be used in the future biological, epidemiological, and control investigations concerning this tick species.

Reproduction of Black Soldier Fly (Diptera: Stratiomyidae) Under Different Adult Densities and Light Regimes.

The black soldier fly (BSF) Hermetia illucens (L.) (Diptera: Stratiomyidae) has been recognized as a promising insect species for sustainable management of organic waste and by-products. Indoor breeding of BSF with artificial lighting has been proved successful, but efforts are still needed to optimize BSF reproductive output. Increasing adult density seems an option to exploit space, whereas decreasing artificial lighting duration may reduce unnecessary power consumption. This study aimed at investigating the effects of adult density (10, 25, and 50 pairs per 30 × 30 × 30 cm cage; i.e., 370, 926, and 1,852 pairs/m3), light regime (8:16, 12:12, and 16:8 [L:D] h), and their possible interactions, on some BSF life history traits relevant to reproduction. The results show that the overall BSF reproductive output increased with increasing adult density but was not affected by light regimes per se. With the highest BSF adult density tested, an average of more than 20,000 neonate larvae were produced from a cage within 10 d. At this density, increasing photoperiod increased neonate production, but also decreased the number of neonates per watt used for artificial illumination. The temporal oviposition patterns, mean individual female reproductive output, mating success, egg hatching rate, and insect survival rate were not affected by adult density or light regime as simple effects. However, the interaction between adult density and light regime was significant for the first oviposition peak, mean individual female reproductive output, and insect survival rate. The possible mechanisms behind our results are discussed.

Some Biological Parameters of Caryedon furcatus (Anton & Delobel) (Coleoptera: Chrysomelidae), Developing on the Seeds of Senegalia macrostachya (Reichenb. ex DC.) Kyal. & Boatwr. (Fabales: Mimosaceae), an Edible Wild Legume in Burkina Faso

The beetle Caryedon furcatus (Coleoptera: Chrysomelidae) attacks and destroys the seeds of Senegalia macrostachya (Fabales: Mimosaceae), thereby limiting their availability as food throughout the year. Very few studies have focused on the ability of this pest to develop on S. macrostachya seeds. The objective of this study was to determine some bio-demographic parameters of C. furcatus on the seeds of S. macrostachya. The results of this study showed that the peak of female oviposition occurs on the second day after emergence. The female laid during her lifetime, an average of 37 eggs of which an average of 35 hatched, while larval survival until imago was 87.14 %. The weight and size of emerged adults did not differ statistically by sex. However, the sex ratio was female-biased. The mean development time for C. furcatus to complete its development on the seeds of S. macrostachya was 50 days. With a population that doubles every 4.75 days, C. furcatus could cause significant damage to the seed stocks of S. macrostachya.

Potential of parasitoid Gronotoma micromorpha Perkin (Hymenoptera: Eucoilidae) as a biocontrol agent for pea leafminer fly, Liriomyza huidobrensis Blanchard (Diptera: Agromyzidae)

The potential of the parasitoid, Gronotoma micromorpha (Perkin) as a biological control agent for pea leafminer fly, Liriomyza huidobrensis (Blanchard) has been evaluated in a series of studies on the fly preference to host instars, biological characteristic and functional response to the host density. The studies were carried out at the Laboratory of Integrated Pest Management (IPMLab), Faculty of Agriculture Udayana University in Denpasar and Greenhouse Owned-Farmer in Pancasari Buleleng, Bali (1200 m asl; average temperature 23.67 ± 5.69 °C and average RH of 64 ± 17.69%). The results showed that G. micromorpha has a strong preference towards the 3rd instar larvae of L. huidobrensis. The pre-oviposition period was 0.4 ± 0.67d, oviposition was 12.5 ± 2.0d and post-oviposition period was 1 ± 0.0d while the peak oviposition occurred on the 4th day. Meanwhile, all the offsprings produced were females which indicated that parthenogenesis thelytokous was present in G. Micromorpha and the fecundity was 29 ± 3.77 per female adult. Furthermore, the average life span for the adult was 13 ± 1.42 days with an oviposition period of 12.5 ± 2.01 days. The average post-oviposition period was 1 ± 0.0 days and average development period of egg to adult was 32.03 ± 0.98 days. Meanwhile, the breeding potential was high with an average daily percentage of 2.27 ± 0.27 fecundity and a maximum spawning occurred on day 4. The functional response was type-2 and it is the rate at which parasitism increase with increase in population of the host density. Hence, the biological characteristics and mode of functional response by the parasitoid showed its potential as a biological pesticide for pea leafminer L. huidobrensis.

Later Nesting by Hawksbill Turtle following Sea Surface Warming

We studied the nesting behavior of the Hawksbill Turtle (Eretmochelys imbricata) along the northeastern coast of Brazil, specifically in southern Rio Grande do Norte. We compare the peak of nesting activity for several seasons from 2006 to 2016. The raw data consist of daily records of the presence of hawksbill turtle on a beach (N = 3,717). In the statistical analysis, we construct a cumulative sum of data and perform a logistic fitting. Furthermore, we use the derivative of the fitting to find the peak of nesting season. We observed a drift in the oviposition peak of the Hawksbill Turtle. In addition, the peak of maximal sea surface temperature in the nesting area followed a similar drift. The results suggest that the Hawksbill Turtle population has been responding to warming environmental changes.

Reproduction and demography of an Aphidophagous ladybird, Hippodamia variegata on six aphid species

We tested six aphid species, viz. Aphis gossypii, Aphis craccivora, Brevicoryne brassicae, Lipaphis erysimi, Myzus persicae and Uroleucon compositae as essential foods needed for the reproduction and demography of an aphidophagous ladybird, Hippodamia variegata. Females were highly fecund (1210.8 ± 55.31 eggs) with prolonged oviposition period (56.30 ± 2.36 days) and laying most viable eggs (92.91 ± 0.81%) when fed on A. gossypii (reared on Lagenaria vulgaris) with the highest net reproductive rate (449.45 ± 20.53 females / female). Aphis craccivora (raised on Dolichos lablab) supported optimal value for intrinsic rate of increase (0.183 ± 0.003) with the shortest generation time (32.40 ± 0.557 days). Other diets didn’t show improved performance but quantified as essential foods. Brassica hosted B. brassicae and L. erysimi were less suitable but not the rejected prey. Age-specific fecundity of female H. variegata was triangular in function with peak oviposition during her early reproductive age when fed on either A. gossypii, A. craccivora, U. compositae or M. persicae, while peak skewed towards later reproductive age when fed on B. brassicae or L. erysimi. Fecundity was positively correlated with egg-viability and oviposition period. We used jackknife technique to estimate and compare the demographic parameters within the groups. High values of intrinsic and finite rates of increase on A. gossypii and A. craccivora affirm their suitability for augmentative rearing of H. variegata. We conclude that both A. gossypii and A. craccivora on above respective host-plants are highly suitable aphid-diets for mass-multiplication of H. variegata.

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Life cycle, parasitism and damage of Xanthogaleruca luteola (Muller) in Valencia (SE Spain): A preliminary study

Xanthogaleruca luteola (Muller) (elm leaf beetle, ELB) (Coleoptera, Chrysomelidae) is a serious pest for elms in urban green areas of Mediterranean climate zones in Spain. In order to design an integrated pest management strategy, a study was conducted on this insect in the city of Valencia (east Spain) in six streets that house trees of the species Ulmus minor. Four larvae increases were found that peaked in mid-May, the first half of July, the second half of August and the end of September/beginning of October. The mean degree-days accumulations required for completion one generation were 612°D±24.98, and 461.12°D±43.95 were needed between the oviposition peaks and adult emergence peaks. Larvae caused a higher degree of defoliation than adults. The defoliation levels caused by generations 1 and 2 were similar, and higher than those caused by generations 3 and 4. Defoliation ranged between 30% and 100% in September. The degree of defoliation and citizen pressure led to treatment, performed by injecting trunks with abamectin in the first generation in three streets under study. This treatment did not allow the level of defoliation to increase with each new generation, and the mean degree of defoliation remained below 30% throughout the study period. Two parasitoid species were identified: Oomyzus gallerucae (Fonscolombe) (Hymenoptera, Eulophidae) from the eggs and Erynniopsis antennata (Rondani) (Diptera, Tachinidae) from larvae, prepupae and pupae of ELB. Nonetheless, during the year of this study, and after considering the defoliation undergone by elms, the parasitism level was low and insufficient to keep Elm leaf beetle at tolerable levels. The integrated ELB management involved regularly monitoring defoliation levels with each new ELB generation by setting the treatment threshold at 20% defoliation and favouring biological control by increasing the quantity and diversity of plants in urban green areas to provide natural enemies with refuges and food.

Estimation and validation of developmental thresholds and thermal requirements for cotton pink bollworm Pectinophora gossypiella

The developmental thresholds and thermal requirements of pink bollworm were estimated using laboratory data on its development at six constant temperatures from 15 °C to 38 °C. The results were validated using field data on male moth catches in sex pheromone traps baited with gossyplure recorded at Nagpur (Maharashtra) during 2018 for predicting the initiation of moth emergence and completion of generation events. The theoretical lower and upper threshold temperatures estimated using non–linear Sharpe and DeMichele model applied to mean development rates were: 14.17/35.43, 15.18/35.48, 11.00/35.48 and 13.40/35.50 °C, and the thermal requirements estimated as inverse of slope of linear regression were: 72.99, 285.71, 144.92 and 503.62° days for development of eggs, larvae, pupae and egg – adult emergence, respectively. Simulation of life table parameters provided reasonably closer estimates across the tested locations. The estimated lower and upper threshold temperatures accumulated the heat units (489.90–497.90) closer to the laboratory estimates (503.62 DD) and sensibly predicted the developmental events in pink bollworm with ±1.0 day error of margin under field conditions. The estimated thresholds and thermal requirements may help in comprehending seasonal dynamics of pink bollworm in relation to timings of developmental events like beginning and peaks of moth emergence, oviposition and egg hatching. This could facilitate in undertaking timely pest management actions such as insecticidal applications.

The reproductive behavior and evaluation of sex pheromone gland extracts of Ectropis grisescens (Lepidoptera: Geometridae)

The geometrid, Ectropis grisescens Warren, is one of the most serious defoliators of the green tea, Camellia sinensis. In the present study, adult emergence, calling behavior, mating activities, and oviposition patterns were observed and the effect of female sex pheromone was evaluated under laboratory conditions (25 ± 1 °C, 14:10 light/dark and 70–75% RH). Adult emergence and calling behavior occurred only at the scotophase. The peak emergence occurred 2 h into the scotophase for males and 3 h for females. Female calling behavior occurred during 1–4 days after eclosion, with most callings among the 1-day-old and the calling gradually decreasing by the age. Mating behavior was first observed at the 2 h into the scotophase. While the mating peak time was similar, 6–8 h into the scotophase for single-pair and multiple-pair groups, the peak of oviposition was 3 days after mating. The pheromone gland extracts from the abdominal tips of 1–2 days virgin female moths were more attractive than the virgin females or the control in the wind tunnel tests. Our findings provide scientific basis to ecological control of E. grisescens.

Diel periodicity and visual cues guide oviposition behavior in Phlebotomus papatasi, vector of old-world cutaneous leishmaniasis.

BackgroundPhlebotomine sand flies are vectors of human leishmaniases, important neglected tropical diseases. In this study, we investigated diel patterns of oviposition behavior, effects of visual cues on oviposition-site selection, and whether these affect the attraction of gravid Phlebotomus papatasi (Scopoli), the vector of old-world cutaneous leishmaniasis, to olfactory cues from oviposition sites.Methodology/principal findingsTo evaluate these questions, we conducted a series of experiments using attraction and oviposition assays within free-flight test chambers containing gravid females entrained under a 14:10 hrs light:dark photoperiod. By replacing sticky-screens or moist filter papers every three hours, we showed that oviposition site search occurs mainly in the latest part of the night whereas peak oviposition occurs during the early part of the night. Behavioral responses to olfactory oviposition cues are regulated by time-of-day and can be disrupted by transient exposure to a constant darkness photoperiod. Gravid females, but not any other stage, age, or sex, were attracted to dark, round oviposition jars, possibly resembling rodent burrow openings. This visual attraction disappeared in the absence of an illumination source. Egg deposition rate was not affected by jar color. Olfactory cues had the strongest effect when the visual cues were minimal.Conclusion and significanceOur study showed, for the first time, that visual cues in the form of oviposition-site color, lighting level, and photoperiod are important in guiding the oviposition behavior of phlebotomine sand flies. Furthermore, such visual cues could modify the flies’ sensitivity to olfactory oviposition cues. Our results suggest that chemosensory and visual cues are complementary, with visual cues used to orient gravid females towards oviposition sites, possibly at long- to medium-ranges during crepuscular periods, while olfactory cues are used to approach the burrow in darkness and assess its suitability at close-range. Implications to sand fly control are discussed.

Effects of sublethal fumigation with phosphine on the reproductive capacity of Liposcelis entomophila (End.) (Psocoptera: Liposcelididae)

The goal of our study was to determine if phosphine exposure changed the fecundity of the surviving Liposcelis entomophila, and the fitness of resulting offspring. Two strains of L. entomophila, were tested. One (F0) that had not been exposed to phosphine in the laboratory, and a second (F4) that had been exposed to the LC50 dose of phosphine for 4 successive generations. The daily egg production, rate of growth, hatching rate, sex ratio, and adult emergence rate were measured after exposures to phosphine at the LC20 and LC50 doses. LC20 fumigation did not affect peak oviposition and fumigation at LC50 dose delayed peak oviposition peak in F0. Females fumigated at LC20 dose had higher fecundity in the first oviposition peaks from 3rd day. The accumulated egg production of F4 fumigated at LC20 and LC50 was significantly higher than that of F0 in the first and second weeks. All the results indicated that long term fumigation with sublethal LC20 could stimulate the surviving females to lay more eggs. Fumigation at LC50 dose could inhibit female fecundity and progeny population growth. The results suggested that long-term fumigation with LC20 could induce strong population growth and lead to L. entomophila infestations.

Fecundity for free? Enhanced oviposition in longevous populations of Drosophila melanogaster.

Artificial selection for increased life span in experimental populations of Drosophila melanogaster sometimes produces long-lived populations that exhibit greater fecundity than unselected controls. The absence of a trade-off between survival and reproduction in these cases might be an artefact of the rich diet of typical lab culture; if nutritional resources are not limiting then there may be no need to trade off. Here I test the rich diet hypothesis by estimating genetic correlations between survival and age-specific fecundity in three nutritional environments. Experimental material consists of 58 recombinant inbred lines derived from an artificial selection experiment. Reducing the yeast content of medium causes substantial reductions in fecundity but does not alter patterns of genetic correlation. The correlation between life span and early fecundity is non-significant in all environments, while the life span correlations with mid-life fecundity are positive and statistically significant in all environments. The rich diet hypothesis is rejected. Qualitative features of fecundity trajectories are conserved across environments, with long-lived lines exhibiting a secondary peak of oviposition in mid-life. The micro-evolution of extended life span is not a monolithic process and does not necessarily involve direct trade-offs between survival and reproduction.