Oviposition Substrate Research Articles

A Solution for Counting Aedes aegypti and Aedes albopictus Eggs in Paddles from Ovitraps Using Deep Learning

In 2018, the Epidemiological Record 36 of the World Health Organization (WHO) indicates that around 390 million people get infected from Arboviroses or mosquito-borne diseases. Among the transmission vectors of these diseases, the Aedes aegypti and Aedes albopictus are responsible for a considerable parcel of the infections since they can transmit a broad range of infections (e.g., dengue, yellow fever, and chikungunya). To reduce the number of infections and deaths caused by these mosquitoes, monitor and control the population of these insects is a key factor. In this sense, ovitraps can be employed to monitor the population of Aedes mosquitoes. Ovitrap is a dark container filled with water where a porous wooden paddle is inserted to serve as an oviposition substrate. These devices are installed in monitored areas and, periodically technicians collect them to count the number of eggs deposited in the paddles manually. Because the manual egg counting task can be time-consuming and susceptible to human errors, in this work we present a solution that uses deep learning algorithms to automate the counting process. Moreover, to further reduce the human effort in the counting process, hardware that automatically acquires the images of the wooden paddles is also presented. Experiments comparing the proposed solution, the manual counting method, and two other solutions, namely ICount and EggCounter, are performed. The results achieved indicate that the proposed method achieved a superior result than the two other methods. Moreover, the application of the Wilcoxon test with a confidence interval of 95% indicates that the solution presented can be as accurate as of the manual counting method which is currently adopted.

Effect of Diets and Low Temperature Storage on Adult Performance and Immature Development of Phyllonorycter ringoniella in Laboratory.

The Asiatic apple leaf miner, Phyllonorycter ringoniella (Matsumura), is an important insect pest to apples. We developed a rearing method for P. ringoniella in the laboratory. Overwintering pupae were collected from our apple orchard, and crabapple seedlings were selected as oviposition substrate and food source for the larval development. The mean developmental period was 25.9 ± 0.49 days from egg to adult and the survival rate was 0.387 under 25 ± 1 °C, 65 ± 5% RH and a photoperiod of 14:10 (L:D) h. Mean egg length and egg width were 0.336 ± 0.0043 and 0.259 ± 0.0046 mm, respectively. Mean body length and head width increased from 1.070 ± 0.0245 and 0.180 ± 0.0021 mm in first instar larvae to 5.027 ± 0.0718 and 0.321 ± 0.0021 mm in fifth instar larvae, respectively. The mean weight of the pupae was 0.946 ± 0.0132 mg. The wingspan of male adult (6.280 ± 0.0639 mm) was significantly larger than female (6.040 ± 0.0753 mm). The mean fecundity (56.9 ± 8.58 eggs per female) and longevity (8.2 ± 0.55 days) of females was highest when they were provided with 10% honey solution, followed by 10% sugar, water, and control. The females preferred to lay eggs (56.5 ± 3.84%) near the secondary leaf vein in a leaf. The larval mortality increased linearly (R2 = 0.94) with the number of larvae per leaf. The mortality of pupae increased from 5.6 ± 4.01 to 51.1 ± 9.88% as storage periods at 4 °C increased from 0 to 105 days. The rearing method and its biological characteristics presented in this study will contribute to further studies on this pest insect.

Oviposition Substrate Selection, Egg Mass Characteristics, Host Preference, and Life History of the Spotted Lanternfly (Hemiptera: Fulgoridae) in North America.

Oviposition substrate selection, egg mass characteristics, host preference, and life history of Lycorma delicatula (White) (Hemiptera: Fulgoridae) were studied in Pennsylvania between 2016 and 2017. Twenty-four substrate types (trees, shrubs, and nonliving materials) were selected by females for oviposition. Tree-of-heaven, black cherry, black birch, and sweet cherry were favored at 62.5% of the types and accounted for 68.5% of the egg masses based on survey results 200 cm above ground. Egg mass density ranged between 0.2 and 75.2 egg masses/m2 with no significant difference among substrate types. Egg mass size ranged between 0 and 192 eggs/egg mass, with 91.8% containing <50 eggs. Significantly larger egg masses were found on sweet and black cherry compared with tree-of-heaven, with significantly higher hatch success on black locust. Eggs hatched between May 2 and June 5 and peaked on 18 May 2017. Tree-of-heaven and summer grape were preferred by nymphs and adults, while multiflora rose and black walnut were favored by the first, second, and the fourth instar nymphs, respectively. The first, second, third, fourth instars and adults lasted for 62 (2 May-3 July), 42 (8 June-20 July), 35 (26 June-31 July), 39 (10 July-18 Aug.), and 114 (24 July-15 Nov.) days, with peaks on 25 May, 22 June, 6 July, 31 July, and 22 Aug., respectively. Adult feed for 2 months before laying eggs in early October. Cumulative degree-days were 0-325, 153-652, 340-881, 567-1,020, 738-1,227, and 942-1,795 for the egg, first, second, third, fourth instar, and adult stage, respectively. Oviposition strategies and development patterns were discussed.

Novel prey boosts the expansion of host-plant range in a native predatory bug

Anthocoris nemoralis (Fabricius) is a Palearctic predator associated with psyllids in their native region. We found it preying on the non-native psyllid Glycaspis brimblecombei Moore, on Eucalyptus camaldulensis Dehnh. Here, we demonstrate the predator acceptance of E. camaldulensis leaves as a substrate for oviposition. We further tested the ability of A. nemoralis to complete its life cycle on E. camaldulensis trees, while feeding on G. brimblecombei. For this purpose, we enclosed infested branches in bags with adult predators, during one-month trials. At the end of the trials we found eggs, nymphs and newly born adults of A. nemoralis, confirming that a complete life cycle had occurred. The psyllid population growth rate was lower in the bags with predators than in the control. These results point out: (1) the ability of A. nemoralis to feed and complete a life cycle on exotic novel prey; (2) the acceptance of an exotic host plant; and (3) A. nemoralis as a potential candidate for the biological control against invasive psyllid species.

The composition of the egg-parasitoid guild of the golden egg bug, Phyllomorpha laciniata (Heteroptera: Coreidae), in Spain

The golden egg bug (Phyllomorpha laciniata (Villers)) is a phytophagous insect with an unusual reproductive system. Females use the bodies of conspecifics, both males and females, as oviposition substrates. In addition, a varying fraction of the eggs is laid on the food plant. Egg carrying on conspecifics increases offspring survival. Predators and, especially, hymenopteran parasitoids are themain cause of egg mortality. So far, only the wasp Gryon bolivari (Giard) (Hymenoptera: Scelionidae) has been reported as an egg parasitoid of P. laciniata in several Mediterranean populations. In this study, three new egg-parasitoid species are recorded from P. laciniata: the primary solitary parasitoids Gryon monspeliense (Picard) and Telenomus sp. (Hymenoptera: Scelionidae), and the facultative hyperparasitoid Ooencyrtus telenomicida (Vassiliev) (Hymenoptera: Encyrtidae). All of these parasitoids have been reared from host eggs being carried by conspecific bugs. We discuss the taxonomy and biology of the individual parasitoid species, as well as ecological and evolutionary aspects of the interactions in this host-parasitoid system.

Biology and Laboratory Rearing of Codling Moth, Cydia pomonella (L.) (Lepidoptera: Tortricidae) on Its Natural Host “Green Immature Apple” Malus domestica (Borkh) (Rosales: Rosaceae)

The&#x0D; codling moth, Cydia pomonella Linnaeus, 1758 (Lepidoptera: Tortricidae) is an economically&#x0D; important pest of apple trees in Turkey and also in worldwide. The aim of this&#x0D; study was to report a continuous rearing method on green immature apples (Malus domestica cv. 'Gala') for C. pomonella and fundamental information&#x0D; of its biology. The experiments were conducted from 2017 to 2019 under the&#x0D; laboratory conditions. Eggs were laid individually or disorderly in small&#x0D; masses on the oviposition substrate in the adult cages. Adult food had a&#x0D; positive effect on the number of eggs laid per female and egg viability. Larvae&#x0D; developed through five instars based on head capsule measurements. Larval development&#x0D; was completed in 15.89±0.25 days. Survival rate of larvae ranged from 24.1% and&#x0D; 92.6% based on larval density per apple. The duration of pupal development was&#x0D; 8.90±0.10 days with 87.5% adult emergence. The life cycle was completed on&#x0D; average in 29.5±0.3 days. Adult longevity was 12.2±0.60 days for&#x0D; females and 16.7±1.90 days for males. A single female laid about 12.3 eggs/day&#x0D; and a total of 85-200 eggs with 83.9% viability. The codling moth has been reared continuously in the laboratory for two years&#x0D; with no evidence of disease in the colony.

Olfactory Preference of Drosophila suzukii Shifts between Fruit and Fermentation Cues over the Season: Effects of Physiological Status.

Worldwide monitoring programs of the invasive fruit pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), using fermentation baits like apple cider vinegar (ACV), revealed a counterintuitive period of low trap catches during summer, followed by an autumn peak. In this study, we demonstrate that ACV baited traps indeed provide a distorted image of the D. suzukii population dynamics as it is possible to capture higher numbers during this “low capture period” with synthetic lures. It was hypothesised that the preference of D. suzukii populations for fermentation cues like ACV is most pronounced during autumn, winter and spring, while the flies prefer fresh fruit cues during summer and that this seasonal preference is related to the changing physiology of the flies over the season. To test this hypothesis, the preference between fermentation cues (ACV) and host fruits (strawberries) and the effect of physiology (sex, seasonal morphology and feeding, mating and reproductive status) was investigated both in olfactometer laboratory experiments and a year-round field preference experiment. In olfactometer experiments we demonstrated that protein deprived females, virgin females with a full complement of unfertilised eggs and males show a strong preference for fermentation cues while fully fed reproductive summer morph females generally prefer fruit cues. These findings indicate that D. suzukii is attracted to fermentation volatiles in search of (protein-rich) food and to fruit volatiles in search of oviposition substrates. Winter morph and starved females displayed indiscriminating olfactory behaviour. In the field preference experiment, the hypothesised seasonal shift between fermentation and fruit cues was confirmed. This shift appeared to be highly temperature-related and was similarly observed for summer and winter morphs.

Temporal patterns and sex differences in dyadic interactions in a wild zebrafish population

Male-female interactions in several group living organisms, including some fish species tend to be dynamic and play a key role in determining their mating and courtship behavior. Laboratory-bred zebrafish (Danio rerio) strains are one of the most widely used model systems in various fields of biology. While research on wild zebrafish behavior is gaining ground, our knowledge about their mating ecology and mating strategies is still limited. We investigated diel temporal patterns in inter-sex dyadic interactions among wild zebrafish and the occurrence of behavioral dimorphism in their interactive behaviors. We observed randomly paired male and female individuals at three distinct time intervals (early morning, morning and afternoon sessions) in the day and collected occurrence data for six discrete inter-individual interactive behaviors that were associated with mating, aggression, and display. We used generalized linear mixed models to examine the effect of time, sex of the individual and presence of oviposition substrate on these behavioral traits. We found a higher incidence of mating-associated behavior during the early parts of the day which declined by the afternoon. These mating-associated behaviors were also dependent on the presence of gravel substrate for egg-laying compared to other behaviors. This work is the first of its kind that details patterns in behavioral dimorphism between sexes in zebrafish. Our results throw light on the complex dynamics of male-female interactions in a group living externally fertilizing species and can have implications in designing experiments involving behavioral testing of zebrafish which is increasingly being done in toxicological studies and laboratory breeding.

PLANT INFUSIONS MEDIATE OVIPOSITION OF MALARIA, DENGUE AND FILARIASIS VECTORS: PUSH-PULL APPROACH FOR VECTOR SURVEILLANCE AND CONTROL

ABSTRACT Semiochemicals are small organic compounds that mediate interactions between organisms by transmitting chemical messages. They are used by insects for intra- and inter-species communication in their ecosystem. Mosquitoes transmit malaria, dengue, West Nile virus, chikungunya, yellow fever, filariasis and encephalitis to human beings across the globe. Mosquitoes perceive semiochemicals in their environment respectively emanating from potential hosts and habitats by the sensory apparatus and act wisely for the benefit of their progeny. Host seeking and/ avoidance, oviposition site seeking behaviors are governed predominantly by chemical stimuli along with visual cues that ensure blood feeding and subsequent egg laying to complete the gonotrophic cycle. Further, plant materials such as neem, tobacco and their infusions are naturally repulsive to mosquitoes while infusions of Bermuda grass could be a promising avenue for exploring natural attractant molecules using gas-chromatography coupled massspectrometry to identify biologically active molecules. In the laboratory studies one week old infusions of neem seed kernel and dried tobacco leaves reduced 90-97% egg deposition by gravid females of Anopheles stephensi, Aedes aegypti, and Culex quinquefasciatus mosquitoes, while oviposition substrates treated with one week old infusion of Bermuda grass, Cynodan dactylon received 40-60% increased egg laying compared to control. Through GC-MS analysis of these plant materials revealed several fatty acids, hydrocarbons, nicotine, thymol, ethyl dithioisoindole, -lactone, -elemene, squalene, eudesmenol and stigmasterol that could be responsible for the attraction and repulsion of mosquitoes to respective extracts. Being biological in origin, these semiochemicals are safe to humans and environment, when judiciously used would manage effectively the mosquito menace and mosquito borne diseases.

Reproductive Capacity Evolves in Response to Ecology through Common Changes in Cell Number in Hawaiian Drosophila

Lifetime reproductive capacity is a critical fitness component. In insects, female reproductive capacity is largely determined by the number of ovarioles, the egg-producing subunits of the ovary [e.g., 1]. Recent work has provided insights into ovariole number regulation in Drosophila melanogaster. However, whether mechanisms discovered under laboratory conditions explain evolutionary variation in natural populations is an outstanding question. We investigatedpotential effects of ecology on the developmental processes underlying ovariole number evolutionamong Hawaiian Drosophila, a large adaptive radiation wherein the highest and lowest ovariole numbers of the family have evolved within 25 million years. Previous studies proposed that ovariole number correlated with oviposition substrate [2-4] but sampled largely one clade of these flies and were limited by a provisional phylogeny and the available comparative methods. We test this hypothesis by applying phylogenetic modeling to an expanded sampling of ovariole numbers and substrate types and show support for these predictions across all major groups of Hawaiian Drosophila, wherein ovariole number variation is best explained by adaptation to specific substrates. Furthermore, we show that oviposition substrate evolution is linked to changes in the allometric relationship between body size and ovariole number. Finally, we provide evidence that the major changes in ovarian cell number that regulate D.melanogaster ovariole number also regulate ovariole number in Hawaiian drosophilids. Thus, we provide evidence that this remarkable adaptive radiation is linked to evolutionary changes in a key reproductive trait regulated at least partly by variation in the same developmental parameters that operate in the model species D.melanogaster.

Larval experience of stable fly, Stomoxys calcitrans Linneaus, 1758 (Diptera: Muscidae) does not influence oviposition preference in gravid females

1. Hopkins' host selection principle (HHSP) proposes that, in holometabolous insects, gravid females prefer to oviposit on their developmental substrate. This hypothesis is widely explored in phytophagous insects, but few studies have considered blood‐feeding insects. In this study, the HHSP was tested using the haematophagous stable fly, Stomoxys calcitrans (Diptera: Muscidae). Using no‐choice and two‐choice tests, the study first sought to demonstrate whether S. calcitrans larvae recognise their rearing substrate.2. It was found that when a rearing substrate is offered to S. calcitrans larvae singly (no‐choice) or associated with a non‐rearing substrate (two‐choice), they were able to recognise the substrate in which they developed. This ability disappeared when larvae were transferred to another substrate for 5 h.3. Next, using oviposition bioassays, it was investigated whether information gathered by pre‐imaginal stages during their development can persist into the adult stages after metamorphosis. It was hypothesised that gravid females emerging from clean and uncleaned pupae reared on sheep and camel dung would still prefer to lay on their rearing substrate. The results revealed that gravid females did not prefer to oviposit on their developmental substrate. In addition, failure to recognise and prefer their developmental substrate was found in gravid females that had emerged from puparia that were cleaned as well as those contaminated with sheep dung.4. It is concluded that S. calcitrans adult preference is not influenced by their offspring's experience. Overall, the HHSP was not supported by our study, suggesting that this principle may not apply to generalist insects characterised by high plasticity in oviposition substrate acceptance.

Effect of female sunflower moth, Homoeosoma electellum (Hulst) (Lepidoptera : Pyralidae) age at first mating on fecundity, fertility, longevity and egg laying pattern

Knowledge of the reproductive behaviour of a pest species is beneficial to improving pest control strategies, particularly those based on perturbing reproduction, such as sex pheromone-based mating disruption. Following copulation, mated females of the different ages were individually transferred to separate 34 ml, clear plastic containers, with a 10% sugar solution absorbed onto a cotton wick. A 2 x 2 cm long blue felt cloth, dusted evenly with ca. 1 mg of H. annuus (variety RHA 274) pollen over its entire surface, was added to the container as an oviposition substrate. Mean fecundity, fertility and longevity were all analyzed by ANOVA. Data were checked for normality and homogeneity of variance; if non-normally distributed, data were transformed and checked again (arcsine or log). Age of female H. electellum at time of first mating significantly influenced lifetime fecundity (F=7.93, df = 4, 45, P<0.0001, ANOVA) and fertility (F=9.09, df =4, 45, P<0001). In general, younger females had greater fecundity and fertility than did older females. Thus, females that first mated at 1 day were significantly more fecund and had greater fertility than did females that first mated at 3 days or older.

Selection of oviposition sites by ground beetles Abaris basistriata and Selenophorus seriatoporus for mass rearing purposes

The oviposition preferences of Abaris basistriata Chaudoir and Selenophorus seriatoporus Putzeys (Coleoptera: Carabidae) were studied in the laboratory. Tested variables were substrate type (soil, vermiculite, cotton wool, and black gauze) and soil depth (0 to 20 cm) in terms of carabid beetle preference for oviposition. Both carabids preferred soil over the other substrates for oviposition. However, A. basistriata also showed a preference for black gauze. As for oviposition depth, A. basistriata laid eggs at a depth of 12 cm, while S. seriatoporus up to 20 cm. In terms of cost, soil was unprofitable as a substrate, mainly due to a high labor demand for prior preparation. Cotton wool was the substrate with the lowest cost. In conclusion, preference is a key mechanism that has to be understood the rearing ground beetles.

Egg-laying decisions based on olfactory cues enhance offspring fitness in Stomoxys calcitrans L. (Diptera: Muscidae)

Selection of oviposition substrate is critical in holometabolous insects. Female stable flies, Stomoxys calcitrans, locate and select vertebrate herbivore dung in which they lay their eggs. However, the preference for vertebrate herbivore dung by S. calcitrans females, its fitness consequences for offspring, and the semiochemicals used to locate and select oviposition substrates remain unclear. Using oviposition choice tests and life table bioassays we found that gravid female S. calcitrans prefer to oviposit on donkey and sheep dung, which also improves the performance of their offspring. GC-MS analysis followed by random forest classification identified β-citronellene and carvone as the most important predictive volatile organic compounds of donkey and sheep dung, respectively. In multiple choice oviposition bioassays, S. calcitrans laid more eggs in wet sand containing β-citronellene and carvone than in other treatments. The attractiveness of these compounds was confirmed in a field trial, with traps baited with β-citronellene and carvone catching more S. calcitrans. We conclude that gravid female S. calcitrans use semiochemical cues to choose oviposition substrates that maximise offspring fitness.

Anchoring of greenhouse whitefly eggs on different rose cultivars

Whiteflies attach their eggs to plants by implanting the egg pedicel into the epidermis of the underside of leaves. This pedicel works like a wall plug embedded in sealing cement, presenting a smart interconnection, which was exemplarily studied in Trialeurodes vaporariorum eggs on two stages of abaxial leaflets of four cut rose cultivars using a combination of microscopic and biomechanical techniques. The penetration force obtained by piercing single epidermal cells with an insect minuten pin did not significantly correlate with the force which was applied to pull off the greenhouse whitefly eggs from abaxial leaves. A maximum pull-off force of 5.4 mN was measured on young leaves of the rose cultivar ‘Schloss Ippenburg®’, corresponding to maximum 941 times the egg weight. Egg pull-off force significantly differed between cut rose cultivars and leaf ages. On greenhouse whitefly-susceptible cultivars ‘Poesie®’ and ‘Reggae®’, eggs detached, applying less force compared to that on resistant cultivars. Leaf structural features had no significant impact on greenhouse whitefly egg pull-off forces. A major effect of leaf turgor pressure and swelling of colleterial gland secretion (cement) surrounding the whitefly egg is assumed to facilitate the firm interconnection between egg and plant epidermis by a combination of form closure, friction locking, and adhesive bond forming a composite material in the contact region. This bond exhibits a maximum adhesive strength of 12.2 MPa, which is much higher than those in beetle and moth eggs glued to oviposition substrates.

Different Oviposition Strategies of Closely Related Damselfly Species as an Effective Defense against Parasitoids.

Parasitoidism is one of the main causes of insect egg mortality. Parasitoids are often able to detect eggs using semiochemicals released from eggs and disturbed plants. In response, female insects adopt a wide variety of oviposition strategies to reduce the detectability of eggs and subsequent mortality. We evaluated the proportion of parasitized and undeveloped eggs of three common damselfly species from the family Lestidae, the most diverse group of European damselflies, in terms of oviposition strategies, notably clutch patterning and the ability to utilize oviposition substrates with different mechanical properties. We assumed that higher costs associated with some oviposition strategies will be balanced by lower egg mortality. We found that the ability of Chalcolestes viridis to oviposit into very stiff substrates brings benefit in the form of a significantly lower rate of parasitoidism and lower proportion of undeveloped eggs. The fundamentally different phenology of Sympecma fusca and/or their ability to utilize dead plants as oviposition substrate resulted in eggs that were completely free of parasitoids. Our results indicated that ovipositing into substrates that are unsuitable for most damselfly species significantly reduces egg mortality. Notably, none of these oviposition strategies would work unless combined with other adaptations, such as prolonging the duration of the prolarval life stage or the ability to oviposit into stiff tissue.

Ultrastructural variation and adaptive evolution of the ovipositor in the endemic Hawaiian Drosophilidae.

Ecological diversification of the endemic Hawaiian Drosophilidae has been accompanied by striking divergence in egg morphology, and ovarian structure and function. To determine how these flies successfully oviposit in a variety of breeding substrates, we used Scanning Electron Microscopy to examine the ultrastructure of the ovipositor of a sample of 65 Drosophila species and five Scaptomyza species of this hyperdiverse monophyletic group. The Drosophila species analyzed included representatives of the fungus-breeding haleakalae group, the leaf-breeding antopocerus and modified tarsus groups, the modified mouthparts species group, the nudidrosophila, and the picture wing clade; the latter sample of 41 species from four species groups included stem- and bark-breeders, as well as tree sap flux-breeders. Ovipositor length was found to vary more than 12-fold among Hawaiian drosophilids, with the longest ovipositors observed in the bark-breeding species and the shortest among the Scaptomyza and fungus-breeders. More noteworthy is the striking variation in overall shape and proportions of the ovipositor, in the shape of the apical region, and in the pattern of sensory structures or ovisensilla. Ultrastructural observations of the pair of long subapical sensilla on the ventral side identify these, for the first time, as taste bristles. Ovipositor form correlates strongly with the oviposition substrate used by the species, being of a distinctive shape and size in each case. We infer that the observed morphological divergence in the ovipositor is adaptive and the product of natural selection for successful reproduction in alternate microhabitats. The array of ovipositor forms that have evolved among the Hawaiian Drosophila species represent a series of ecomorphs that along with other divergent traits of the female reproductive system, have contributed to the successful adaptive radiation of this remarkable fauna.

Effect of Temperature on Oviposition Behavior and Egg Load of Blow Flies (Diptera: Calliphoridae).

Making optimal oviposition decisions is especially important for female carrion colonizing insects whose larvae often depend on ephemeral resources. Optimal oviposition theory predicts that females should exhibit behaviors that will maximize the performance of their offspring. Oviposition can be influenced by a variety of factors, including temperature. The aim of this study was to investigate the effects of temperature on the oviposition behavior and egg load of two blow fly species native to southern Ontario: Phormia regina Meigen, and Lucilia sericata Meigen (Diptera: Calliphoridae). Using fetal pig carcasses as an oviposition substrate, we assessed the length of time until the first oviposition event, preferred oviposition sites, and the total number of eggs oviposited. For each of the two species, five different temperature treatments ranging from 15 to 35°C were used. Temperature influenced time to the first oviposition event, as well as the number of eggs deposited by L. sericata and P. regina. As temperature increased, oviposition occurred faster with more eggs deposited for these two species. Female P. regina, in particular, demonstrated a higher egg load with increasing temperature. Differences in optimal temperatures for reproduction, including egg load and oviposition, may be a mechanism driving seasonal temporal resource partitioning leading to species coexistence utilizing ephemeral resources.

INSECTICIDAL ACTIVITY OF ANACARDIUM HUMILE (ANACARDIACEAE) NUT SHELL LIQUID AGAINST AEDES AEGYPTI (DIPTERA: CULICIDAE)

This work investigated the insecticidal activity of Cashew Nut Shell Liquid (CNSL) extracted from the species Anacardium humile, a native plant in the Cerrado biome, against Aedes aegypti. A. humile fruits were collected and kept in a forced ventilation kiln at 40oC for seven days for CNSL extraction. Mortality tests were performed on third stage larvae, pupae and adults. In addition, female oviposition behavior, egg viability, and the residual effect of the solution on 3rd stage larvae were observed. The CNSL was diluted in decreasing gradient concentrations to obtain the Lethal Concentration (LC). In oviposition LC99 was used for larvae. Residual effect and oviposition tests were performed with LC99, LC 50 and LC90 were respectively obtained, 6.63 and 11.23 ppm for larvae. No mortality was observed in adults. The residual effect of the CNSL was five days in LC99. A repellent effect of CNSL on the females was noted, with a significant reduction of egg numbers and a change in egg stratification patterns in the oviposition substrate. The larval hatching rate of the eggs exposed to the substrate moistened with CNSL was significantly lower when compared to the control. The results evidenced the insecticidal activity of A. humile CNSL, suggesting it as a promising product in the quest for new botanical insecticides.

Role of kin recognition in oviposition preference and cannibalism by the predatory mite Gynaeseius liturivorus.

Animals often select oviposition sites to minimize the predation risk for eggs and juveniles, which are more vulnerable to predation than adults. When females produce eggs in clusters, the eggs and juveniles are likely to suffer from cannibalism. Although cannibalism among siblings is known to be lower than among non-siblings, there have been few investigations into the possibility that females select oviposition sites that reduce the risk of cannibalism for the offspring. To test this possibility, we examined oviposition preference by adult females of the predatory mite Gynaeseius liturivorus in response to the presence of her own eggs and to eggs of other females, offering plastic discs as oviposition substrates. Although females did not clearly show a preference for plastic discs on which they had oviposited, they avoided plastic discs on which other females had oviposited. When eggs of other females were artificially placed on clean plastic discs, adult female mites avoided these discs, suggesting that the eggs were used as cues for oviposition preference. Cannibalism among juvenile siblings was lower than among non-siblings. These observations show that adult females and juveniles of G. liturivorus discriminate kin relationships among conspecific individuals. Therefore, oviposition preference by adult female G. liturivorus may lead to the reduced risk of cannibalism among offspring.