Oviposition Chambers Research Articles

Oviposition biology, behavior, and avocado cultivar preferences of Heilipus lauri Boheman (Coleoptera: Curculionidae).

Heilipus lauri is a specialist avocado seed feeding weevil native to parts of México and is an invasive pest in Colombia. This weevil is considered an incursion risk because possible unintended introductions into areas outside of its native range can result in establishment, which threatens avocado production in invaded regions. Despite being a well-recognized pest of avocados, relatively little is known about oviposition biology, behavior, and cultivar preferences of this weevil. Field studies in commercial Hass avocado orchards in México and laboratory studies in a quarantine facility in California (USA) indicated that H. lauri prefers to oviposit into middle and bottom thirds of fruit. In the laboratory, an average of 1.7 eggs (range 1-6 eggs) are laid over a 24-h period in oviposition chambers by individual females. Conspecifics add eggs to these clutches, with up to 17 eggs being recorded in 1 oviposition chamber. This finding suggests that H. lauri does not use an oviposition deterring pheromone. Female weevils readily oviposit in artificial holes representing mechanical wounds on fruit. In comparison to the commercially dominant Hass variety, fruit from Lamb Hass and G22, a native Guatemalan variety, and to a lesser extent Gem, may be less preferred for oviposition when females have a choice of fruit in which to oviposit. Videography studies indicated that H. lauri exhibits predominantly diurnal activity with respect to oviposition behaviors, feeding, and walking.

Assessing the susceptibility and efficacy of traditional neurotoxic (pyrethroid) and new-generation insecticides (chlorfenapyr, clothianidin, and pyriproxyfen), on wild pyrethroid-resistant populations of Anopheles gambiae from southern Benin.

The objective of this study was to determine the susceptibility of wild Anopheles gambiae sensu lato (s.l.) from southern Benin to the new insecticides (chlorfenapyr (CFP), pyriproxyfen (PPF), and clothianidin (CTD)) and assess the efficacy of insecticide-treated bed nets (ITNs) that contain these new products. Wild An. gambiae from the Benin communes of Allada, Ifangni, Akpro-Missérété, and Porto-Novo were tested for their susceptibility to CFP and PPF using the WHO bottle tests, and pyrethroids (alpha-cypermethrin, deltamethrin, and permethrin) and CTD using WHO tube tests. WHO cone tests were used to evaluate the efficacy of Interceptor® (which contains alpha-cypermethrin (ACM) only), Interceptor® G2, (CFP + ACM), and Royal Guard® nets (PPF + ACM). The ovaries of blood-fed An. gambiae from Ifangni exposed to a new PPF net were dissected, and egg development status was examined using Christopher's stages to determine the fertility status of the mosquitoes. Using a standardized protocol, the oviposition rate and oviposition inhibition rate were calculated from live blood-fed An. gambiae placed in oviposition chambers after exposure to PPF. In all four mosquito populations, pyrethroid mortality ranged from 5 to 80%, while chlorfenapyr and clothianidin mortality ranged from 98 to 100%. At Ifangni, all mosquitoes exposed to Royal Guard® nets were infertile (100%) while the majority (74.9%) of mosquitoes exposed to Interceptor® nets had fully developed their eggs to Christopher's stage V. The oviposition inhibition rate after exposure of the mosquitoes to the PPF was 99% for the wild population of An. gambiae s.l. and the susceptible laboratory strain, An. gambiae sensu stricto (Kisumu). The results of this study suggest that pyrethroid-resistant An. gambiae from the selected communes in southern Benin are susceptible to chlorfenapyr, clothianidin, and pyriproxyfen. In addition, based on bioassay results, new and unused Interceptor® G2 and Royal Guard® nets were effective on Ifangni's mosquito populations. Despite the availability of new effective insecticides, continued vigilance is needed in Benin. Therefore, monitoring of resistance to these insecticides will continue to periodically update the Benin national insecticide resistance database and management plan.

Efficacy of Royal Guard, a new alpha-cypermethrin and pyriproxyfen treated mosquito net, against pyrethroid-resistant malaria vectors

Royal Guard is a new insecticide-treated bed-net incorporated with a mixture of alpha-cypermethrin and pyriproxyfen (an insect growth regulator). We assessed its efficacy and wash-resistance in laboratory and experimental hut studies following WHO guidelines. Mosquitoes that survived exposure to the net were kept in separate oviposition chambers and observed for the reproductive effects of pyriproxyfen. In laboratory assays, Royal Guard induced > 80% mortality and > 90% blood-feeding inhibition of An. gambiae sl mosquitoes before and after 20 standardised washes and sterilised blood-fed mosquitoes which remained alive after exposure to the net. In an experimental hut trial against wild free-flying pyrethroid-resistant An. gambiae sl in Cové Benin, Royal Guard through the pyrethroid component induced comparable levels of mortality and blood-feeding inhibition to a standard pyrethroid-only treated net before and after 20 washes and sterilised large proportions of surviving blood-fed female mosquitoes through the pyriproxyfen component; Royal Guard induced 83% reduction in oviposition and 95% reduction in offspring before washing and 25% reduction in oviposition and 50% reduction in offspring after 20 washes. Royal Guard has the potential to improve malaria vector control and provide better community protection against clinical malaria in pyrethroid-resistant areas compared to standard pyrethroid-only LLINs.

The effect of temperature on the development and reproduction of Busseola fusca (Lepidoptera: Noctuidae).

The effect of temperature on the reproduction and development of Busseola fusca was studied under laboratory conditions. Single male-female pairs were confined to oviposition chambers kept at 15, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. Data on reproduction parameters were captured daily. Oviposition occurred at all the mentioned temperatures but no fertility was recorded at 30°C. The total number of eggs laid per female moth was between 300 and 400 and the optimum temperature for oviposition and fertility was between 20 and 26°C. Larval development was studied at five different temperature regimes, i.e. 15, 18, 20, 26 and 30 ± 1°C and a 14L:10D photoperiod. The most favourable temperature as well as the upper threshold temperature for larval development was between 26 and 30°C. Total development period was 152.6-52.6 days, respectively, at 15°C, and 26-30°C. The thermal constants for B. fusca was 99.50, 536.48, 246.25 and 893.66°D and lower temperature thresholds were 10.36, 8.14, 8.99 and 8.84°C, for completion of the egg, larval, pupal and egg-to-adult stages, respectively. Results on the thermal constants and lower and upper threshold temperatures of B. fusca can be used to predict the impact of climate change on the distribution and population growth of this pest.

Sub-additive effect of conspecific eggs and frass on oviposition rate of Lutzomyia longipalpis and Phlebotomus papatasi

Oviposition behavior is a fairly neglected aspect in our understanding of the biology of sand flies. In this study, we used a comparative approach using both new- and old-world species (Lutzomyia longipalpis and Phlebotomus papatasi) in choice and no-choice oviposition chambers to evaluate the effect of old sand fly colony remains (frass), conspecific eggs, and their combination on oviposition rates of these sand flies. We also tested the effect of egg washing with de-ionized water on oviposition rates. In both choice and no-choice experiments, sand fly species laid more eggs on a substrate containing frass. The effect of eggs alone was not significant but showed a positive trend. Furthermore, for both sand fly species, the effect of the combined treatment was sub-additive suggesting a potential inhibitory effect of one factor on the other. Egg washing did not have a significant effect. The choice and no-choice experimental designs did not differ in their outcomes suggesting the choice-design could serve as an effective high throughput method for screening oviposition attractants/stimulants.

Spatial heterogeneity in oviposition preference of the mosquito Aedes notoscriptus (Skuse) (Diptera: Culicidae) in Adelaide, South Australia

Ovitraps were used to determine the container‐breeding mosquito fauna at three sites in suburban Adelaide, South Australia, from January to May 1998. A novel ovitrap design provided a choice of four distinct, water‐filled oviposition chambers: open top/manure slurry, closed top/manure slurry, open top/pond water and closed top/pond water. The traps were hung in trees, 3–4 m above the ground, and predominantly captured one species, Aedes notoscriptus, which enabled an a posteriori analysis of maternal oviposition preferences. At site 1, Ae. notoscriptus preferred closed‐top chambers, regardless of water type, whereas chambers containing manure slurry were preferred at sites 2 and 3, regardless of whether the chambers were open or closed. It is possible that differences in the complexity of vegetation structure and extent of shading between sites (less overall shading and vegetation complexity at site 1) may have elicited phenotypic variability in maternal oviposition choice. However, genetic variability in Ae. notoscriptus between sites cannot be discounted.

Fecundity and Egg Viability of Northern and Western Corn Rootworm (Coleoptera: Chrysomelidae) Beetles Surviving Labeled and Reduced Soil Insecticide Applications

The influence of soil insecticide application rates on the reproductive biologies of field-collected northern and western corn rootworms, Diabrotica barberi Smith & Lawrence, and D. virgifera virgifera LeConte, respectively, was investigated under laboratory conditions. Comparisons were made on beetles obtained from plots treated with planting-time applications of labeled (IX) and reduced (0.5 and 0.75X) rates of chlorethoxyfos, tefluthrin, and terbufos, and from untreated control plots. Captured insects were pooled by species and insecticide treatment into laboratory rearing cages and allowed to mate. Gravid females were held individually in oviposition chambers to assess fecundity. Egg viability was measured on subsamples of eggs from all treatments. No significant differences ( P >0.05) were detected in fecundity, fertility, or percentage of nonviable eggs of D. barberi or D. virgifera with any insecticide or application rate within insecticide tested. However, reductions in total eggs produced and hatch were 31.2 and 53.7%, respectively, for D. virgifera that survived chlorethoxyfos treatment in comparison with beetles that emerged from untreated plots. Also, the percentage of nonviable eggs produced by D. virgifera emerging from chlorethoxyfos-treated plots was 2-fold of that in beetles captured from untreated corn plots. Whereas, D. barberi females from tefluthrin-treated plots experienced a 44% increase in fecundity and 49.2% more egg hatch than those from the untreated controls. Additionally, total eggs and hatch were increased by 32.1 and 33.7%, respectively, in D. barberi that emerged from terbufos-treated corn plots when compared with their counterparts from untreated control plots. The numerical disparities that we observed appeared to be species specific rather than associated with insecticide class or application rate. Our evaluations indicate that using reduced (0.5 and O.75X) application rates of these organophosphate and pyrethroid insecticides will not likely have major effects on the reproductive capacities of D. barberi or D. virgifera . Thus, corn rootworm management programs should include options for using the lowest efficacious application rates of these insecticides.

Seasonal Emergence-Time Effects on Adult Longevity, Fecundity, and Egg Viability of Northern and Western Corn Rootworms (Coleoptera: Chrysomelidae)

Seasonal emergence time was studied to determine its influence on adult vigor and reproductive fitness of field-collected Diabrotica barberi Smith & Lawrence and D. virgifera virgifera LeConte. Time of emergence was divided into six 2-wk intervals (lots; pooled from beetles collected every 2 d from onset to end of seasonal emergence cycle), which served as treatments. Beetles were maintained in single-insect oviposition chambers on a natural diet and were provided soil as an oviposition substrate. The experiment was arranged in a randomized complete block design with 10 replicates. Female D. barberi survived on natural diet for averages of up to 89 d within lots. Earliest emerging (lot 1) beetles of both species lived significantly longer than those from later lots, thus suggesting reduced fitness as the season advanced. Lot fecundity means ranged from 133 to 312 eggs (maximum 1,036) and 357 to 736 (maximum 1,864) eggs per female for D. barberi and D. virgifera , respectively. Corresponding with greater longevity, increased fecundity was also observed with early-emerging females of both species. Beetles emerging during the first part of the growing season appeared to be generally healthier and more reproductively fit than their latter-emerging counterparts. These findings may warrant further evaluations to determine possible effects on late-season management efforts in adult corn rootworm suppression programs. Methodologies associated with insect maintenance and assessment of reproductive biology proved suitable for both species. Additionally, these findings may offer valuable insight needed to refine procedures for laboratory rearing and egg production from D. barberi .

Recognition and avoidance of previously laid egg masses by the oblique-banded leafroller (Lepidoptera: Tortricidae)

Investigations were conducted on oviposition by laboratory-reared oblique-banded leafrollers, Choristoneura rosaceana Harris. In paperbag oviposition chambers, females deposited their egg masses in a significantly nonrandom, uniform manner in 16 of 20 replicates. Inpetri dish oviposition chambers, gravid females were exposed to egg masses recently deposited by other females. As determined by the magnitude of the mean direction vector of the second egg mass in relation to the first, females detected and avoided egg masses laid by other females. In addition, they avoided waxed paper from which a recently oviposited egg mass had been removed. This phenomenon is most likely due to a pheromone laid down with each egg mass.

AN EFFICIENT TECHNIQUE FOR REARING PHLYCTINUS CALLOSUS BOHEMAN (COLEOPTERA: CURCULIONIDAE)

AbstractAn improved rearing technique is described for P. callosus. It involves isolating adult weevils into oviposition chambers, removing newly laid eggs to an incubation chamber to allow first instars to emerge before placing them onto food plants and collecting late instar larvae after 8 weeks. Mean survival of larvae from first instars to late instars is 54%± 7%. It enables continuous mass‐rearing of all development stages for laboratory bioassays.

A method for mass rearing the aphid predatorAnthocoris nemorum

SUMMARYAnthocoris nemorumis currently under investigation as a potential agent for the control of damson‐hop aphidPhorodon humulion hops. Detailed here is a method of rearingA. nemorumto provide a large number of insects with a predetermined age structure for mass release in the field. It is designed to minimise culture maintenance, with components and materials which are readily obtained as, or can be modified from, stock items. Initial cultures are collected from the field, as adults, in early autumn and artificially overwintered. These are recovered in early spring, with females being placed in oviposition chambers, and the harvesting of ova regulated to provide synchronisation of eclosion within batches. Larvae are reared until they reach the desired instar for mass release and then held in controlled cold storage until required.

THE EGG-LAYING BEHAVIOR OF 11 SPECIES OF LYTTINAE (COLEOPTERA: MELOIDAE)

AbstractBehavior patterns associated with egg-laying are proposed as a potentially valuable source of taxonomic characters for blister beetles that excavate oviposition chambers in the soil. Methods of digging the burrows and covering the eggs are complex and stereotyped and often differ considerably from one species to another. Relationships among species of Lytta, Linsleya, and Epicauta suggested by their nesting behavior are compared with those indicated by other characteristics.

The effects of temperature and humidity on the oviposition rate of Tribolium castaneum (Hbst.) (Coleoptera, Tenebrionidae)

The rate of oviposition of isolated pairs of Tribolium castaneum (Hbst.) on finely divided wheatfeed was measured over the entire adult life at 25°C. and 70 per cent. R.H. It was also measured over a period of seven weeks from the start of oviposition at 30 and 70 per cent. R.H. at 25, 30 and 35°C., respectively, at 70 per cent. R.H. only at 22·5, 27·5, 32·5 and 37·5°C. and at 2 per cent. R.H. at 30°C.At 25°C. and 70 per cent. R.H. each female laid, on the average, 360 eggs at the rate of 2·5 per day for about one hundred days and then at a decreasing rate for the next hundred days. When this experiment was repeated over a seven-week period, each female laid on average about 3 eggs per day. At 70 per cent. R.H., the optimum temperature for oviposition was about 32·5°C., at which about 11 eggs per day per female were laid over the seven-week period. These rates fell to just over 2 per day at 22·5°C. Only one egg was laid by 15 females at 20°C. At 37·5°C. the rate was about 10 eggs per day initially but it declined to about 3 per day by the end of seven weeks, whereas at lower temperatures the decline in laying was slight. Compared with 70 per cent. R.H., the oviposition rate at 30 per cent. R.H. was almost halved at 25°C., but was only slightly reduced at 35°C. At 30°C. and 2 per cent. R.H., females laid well, averaging over 4 eggs per female per day. The periodic provision of water for drinking at 25°C. and 30 per cent. R.H. depressed oviposition.The preoviposition period was 2 days at 37·5°C. and increased steadily at lower temperatures to 10 days at 22·5°C. It also varied more between females at low temperatures.The number of eggs recovered in this work was lower than the number obtained by Park & Frank (1948), who used considerably more food in their oviposition chambers. In this work, some eggs were eaten by the adult beetles. However, the innate capacity for increase of the species calculated on these data is extremely high, and could not be maintained for long because of the cannibalistic habits of this species.