Effectiveness of synthetic versus natural human volatiles as attractants for Anopheles gambiae (Diptera: Culicidae) sensu stricto

Females of the African malaria vector, Anopheles gambiae Giles sensu stricto, use human volatiles to find their blood-host. Previous work has shown that ammonia, lactic acid, and aliphatic carboxylic acids significantly affect host orientation and attraction of this species, In the current study, these compounds were tested for their attractiveness relative to human emanations in vivo and in vitro. Emanations from a human hand, incubated sweat, and foot skin residues on a nylon sock were significantly attractive when tested against clean air. In a dual-choice test, foot skin residues were significantly more attractive than emanations from a human hand in vivo. Ammonia alone attracted more mosquitoes than fresh or incubated sweat, However, the odor of a human hand or of foot skin residues were more attractive than ammonia. A known attractive blend of ammonia with lactic acid and carboxylic acids was less effective than natural foot odorants, The results demonstrate that the synthetic blend based on skin odor is attractive for An. gambiae, but that in a choice situation in vitro natural skin odors are still preferred by the mosquito. Differences in volatile organic compound abundances between a worn sock and the synthetic blend may have resulted in stronger attraction to the sock. This suggests that candidate attractants should be evaluated with consideration of the strength of natural odorant sources, The data furthermore suggest that additional unidentified compounds from the human foot are involved in the host-seeking behavior of this mosquito species

Fatal attraction. Control of the housefly (Musca domestica)

Despite its long association with man, the housefly (Musea domestica Linnaeus) remains one of the most difficult pests to control. It is a ubiquitous insect that can be found in houses, stables, food processing factories and other domesticated areas and buildings. Reliance on insecticides for fly control is decreasing because of increased environmental constraints and insecticide resistance. So far, biological control with natural enemies often has disappointing results. Light- and odour-baited traps are considered to be promising devices to control houseflies indoors, although they are not yet effective enough to reduce fly populations to acceptable levels. Therefore, possibilities to improve the effectiveness of these types of traps were examine

Parasitoid load affects plant fitness in a tritrophic system

Plants attacked by herbivorous insects emit volatile compounds that attract predators or parasitoids of the herbivores. Plant fitness increases when these herbivorous insects are parasitized by solitary parasitoids, but whether gregarious koinobiont parasitoids also confer a benefit to plant fitness has been disputed. We investigated the relationship between parasitoid load of the gregarious Cotesia glomerata (L.) (Hymenoptera: Braconidae), food consumption by larvae of their host Pieris brassicae L. (Lepidoptera: Pieridae), and seed production in a host plant, Brassica nigra L. (Brassicaceae), in a greenhouse experiment. Plants damaged by caterpillars containing single parasitoid broods produced a similar amount of seeds as undamaged control plants and produced significantly more seeds than plants with unparasitized caterpillars feeding on them. Increasing the parasitoid load to levels likely resulting from superparasitization, feeding by parasitized caterpillars was significantly negatively correlated with plant seed production. Higher parasitoid brood sizes were negatively correlated with pupal weight of Cotesia glomerata, revealing scramble competition leading to a fitness trade-off for the parasitoid. Our results suggest that in this tritrophic system plant fitness is higher when the gregarious parasitoid deposits a single brood into its herbivorous host. A prediction following from these results is that plants benefit from recruiting parasitoids when superparasitization is prevented. This is supported by our previous results on down-regulation of synomone production when Brassica oleracea was fed on by parasitized caterpillars of P. brassicae. We conclude that variable parasitoid loads in gregarious koinobiont parasitoids largely explain existing controversies about the putative benefit of recruiting these parasitoids for plant reproduction

Van het lab naar de praktijk

Met het de bevindingen uit het laboratoriumonderzoek van Jetske de Boer en Marcel Dicke (Entomologische berichten; Jrg. 64 no. 4(2005)) als leidraad, worden de meningen van twee collega's uit de praktijk, over fundamenteel onderzoek en de relevantie voor de praktijk, in dit artikel beschreve

Larval nutrition differentially affects adult fitness and Plasmodium development in the malaria vectors Anopheles gambiae and Anopheles stephensi

BACKGROUND: Mosquito fitness is determined largely by body size and nutritional reserves. Plasmodium infections in the mosquito and resultant transmission of malaria parasites might be compromised by the vector's nutritional status. We studied the effects of nutritional stress and malaria parasite infections on transmission fitness of Anopheles mosquitoes. METHODS: Larvae of Anopheles gambiae sensu stricto and An. stephensi were reared at constant density but with nutritionally low and high diets. Fitness of adult mosquitoes resulting from each dietary class was assessed by measuring body size and lipid, protein and glycogen content. The size of the first blood meal was estimated by protein analysis. Mosquitoes of each dietary class were fed upon a Plasmodium yoelii nigeriensis-infected mouse, and parasite infections were determined 5 d after the infectious blood meal by dissection of the midguts and by counting oocysts. The impact of Plasmodium infections on gonotrophic development was established by dissection. RESULTS: Mosquitoes raised under low and high diets emerged as adults of different size classes comparable between An. gambiae and An. stephensi. In both species low-diet females contained less protein, lipid and glycogen upon emergence than high-diet mosquitoes. The quantity of larval diet impacted strongly upon adult blood feeding and reproductive success. The prevalence and intensity of P. yoelii nigeriensis infections were reduced in low-diet mosquitoes of both species, but P. yoelii nigeriensis impacted negatively only on low-diet, small-sized An. gambiae considering survival and egg maturation. There was no measurable fitness effect of P. yoelii nigeriensis on An. stephensi. CONCLUSIONS: Under the experimental conditions, small-sized An. gambiae expressed high mortality, possibly caused by Plasmodium infections, the species showing distinct physiological concessions when nutrionally challenged in contrast to well-fed, larger siblings. Conversely, An. stephensi was a robust, successful vector regardless of its nutrional status upon emergence. The data suggest that small-sized An. gambiae, therefore, would contribute little to malaria transmission, whereas this size effect would not affect An. stephensi

Evaluation of low density polyethylene and nylon for delivery of synthetic mosquito attractants.

BACKGROUND: Synthetic odour baits present an unexploited potential for sampling, surveillance and control of malaria and other mosquito vectors. However, application of such baits is impeded by the unavailability of robust odour delivery devices that perform reliably under field conditions. In the present study the suitability of low density polyethylene (LDPE) and nylon strips for dispensing synthetic attractants of host-seeking Anopheles gambiae mosquitoes was evaluated. METHODS: Baseline experiments assessed the numbers of An. gambiae mosquitoes caught in response to low density polyethylene (LDPE) sachets filled with attractants, attractant-treated nylon strips, control LDPE sachets, and control nylon strips placed in separate MM-X traps. Residual attraction of An. gambiae to attractant-treated nylon strips was determined subsequently. The effects of sheet thickness and surface area on numbers of mosquitoes caught in MM-X traps containing the synthetic kairomone blend dispensed from LDPE sachets and nylon strips were also evaluated. Various treatments were tested through randomized 4¿×¿4 Latin Square experimental designs under semi-field conditions in western Kenya. RESULTS: Attractant-treated nylon strips collected 5.6 times more An. gambiae mosquitoes than LDPE sachets filled with the same attractants. The attractant-impregnated nylon strips were consistently more attractive (76.95%; n¿=¿9,120) than sachets containing the same attractants (18.59%; n¿=¿2,203), control nylon strips (2.17%; n¿=¿257) and control LDPE sachets (2.29%; n¿=¿271) up to 40¿days post-treatment (P

Why humans are attractive to malaria mosquitoes

Malaria mosquitoes use host odours to find their blood sources, but little is known about the semiochemicals that mediate this behaviour. A combined study is undertaken to identify the volatile human-specific compounds that are used in the host-seeking behaviour of the females of Anopheles gambia

Attraction of the housefly (Musca domestica L.).

Ultraviolet (UV) light attracts more houseflies compared to green and white light. The attractiveness of UV light is not effected by its spectral composition. The number of flies attracted does not seem to change when a UV lamp is combined with moving elements, although the time spend on the lamp decreases.A few odours have been examined for their ability to attract houseflies. Hungry flies appeared to be attracted by the odour of manure, meat, fruit, and the diet they have been bred on. When the flies were well-fed, only the manure and tainted meat attracted female flies which were looking for a substrate to deposit their eggs. More odours will be examined for their ability to improve the attractiveness of the ultraviolet light trap.</p