Recebido em 26/9/08; aceito em 24/4/09; publicado na web em 7/10/09 AGGREGATION PHEROMONE IN CURCULIONIDAE (INSECTA: COLEOPTERA) AND THEIR TAXONOMIC IMPLICATION. The pheromones of the weevils has been the most studied and used so far for Coleoptera species. The majority of reported weevil pheromones is produced by males and usually attract both sexes. The identified pheromone compounds are classified in two categories: ten-carbon compounds with terpenoid branching and compounds of various sizes, apparently of fatty-acid origin. These pheromone structural categories are consistent within subfamilies. This review aims to give an overview of the aggregation pheromones identified for Curculionidae pests, describing the relationship of the molecules structural pattern among subfamilies, and propose an identification key based on the structure of the pheromone components.Keywords: weevils; pheromone structure; identification key. INTRODUÇÃOOs curculionídeos são besouros da superfamília Curculionoidea, com cerca de 60.000 espécies descritas.1 Os adultos da família Curculionidae são facilmente reconhecidos pela presença de uma cabeça prolongada em um rostro de comprimento muito variável, assim como antenas genículo-clavadas 2 (Figura 1). Os curculionídeos, em sua grande maioria, são fitófagos, tanto na fase larval como na adulta. 3Muitas espécies são importantes pragas de diversas culturas, bem como de grãos armazenados, e a necessidade constante de medidas de controle mais efetivas e seguras ao meio ambiente tem exigido da comunidade científica a busca por novos métodos de controle para minimizar o impacto desses insetos. Como em outros grupos de insetos, esta necessidade tem aumentado a investigação do uso de feromônios como mais uma ferramenta no manejo dessas pragas. Um trabalho extensivo tem sido feito na identificação de feromônios e seu uso dentro da família Curculionidae, 4 exemplificado pelas décadas de pesquisa conduzidas com o bicudo do algodoeiro, Anthonomus grandis.5 Seguindo a identificação de quatro componentes do feromônio de agregação de A. grandis, 6 feromônios de várias espécies de curculionídeos têm sido identificados.A maioria dos feromônios relatada em curculionídeos é produzida pelos machos e usualmente atrai ambos os sexos, por isso são conhecidos como feromônios de agregação. Entretanto, alguns feromônios também têm sido verificados em fêmeas. Estes incluem feromônios sexuais de longa-distância, que atraem principalmente machos, curta-distância ou feromônio de contato, que permitem reconhecer coespecíficos e feromônio de oviposição, que algumas fêmeas usam para marcar os hospedeiros, nos quais elas colocam seus ovos. Finalmente, existem exemplos de curculionídeos utilizando feromônios de outras espécies de besouros, como cairomônios. 4 Em virtude de seus hábitos de vida, o estudo comportamental de curculionídeos é relativamente complexo. Uma alternativa que evita muitos problemas com bioensaios e acelera o processo de identificação é a cromatografia gasosa acoplada à eletroantenografia (CG-EAG)....
The sex pheromone of Lonomia obliqua Walker (Lepidoptera: Saturniidae) was studied in the laboratory. All female calling occurred during the scotophase. Most females (70.6%) called first within 24 hr of eclosion. Calling varied with age of female, with older (5-to 6-day-old) females calling earlier in the scotophase and for longer durations than younger (0-to 1-day-old) females. The sex pheromone gland of 1-to 3-day-old virgin females was extracted during the calling peak. A Y-olfactometer bioassay showed significant attraction of males to a filter paper containing the female gland extract. Gas chromatographic-electroantennogram detection (GC-EAD) analysis of the extract indicated the presence of at least two possible pheromone components. Gas chromatographic-mass spectrometric analysis of the major GC-EAD-active peak indicated a hexadecenyl acetate; chemical derivatization indicated Δ11 unsaturation. Synthetic samples of (E)-and (Z)-11-hexadecenyl acetate were obtained by coupling 10-bromo-1-decanol and 1-hexyne, utilizing lithium chemistry. The comparison of the retention time of dimethyl disulfide derivatives of the natural compound, to those of synthetic chemicals, confirmed the natural compound as (E)-11-hexadecenyl acetate. The minor component was identified as the related alcohol, (E)-11-hexadecenol. The ratio of the two components in female extract was 100:35. Preliminary tests of males in a Y-olfactometer showed that their response to a mixture of the two compounds was not significantly different from that to gland extract.
Ecological succession is a complex processes involving changes in the structure of plant community and it is an important factor determining the structure of arboreal ants assemblages, but little is known about the effects of succession on ant assemblages in regions of Tropical Dry Forests (TDFs), such as the Brazilian Caatinga. The aim of this study was to investigate the effects of ecological succession on the richness and species composition of arboreal ants in fragments of Caatinga, testing the following hypothesis: i) the richness of arboreal ants increases along a gradient of forest succession, in response to tree richness and/or density; ii) species composition of arboreal ants differs among stages of forest succession due to differences in vegetation structure in theses stages. This study was conducted in 15 plots distributed in three areas with different stages of secondary succession (early, intermediate and late). Tree density and richness were used as surrogate of vegetation structure. Ants were sampled using the technique of beating the foliage and baited pitfall traps, where five trees were sampled per plot, totaling 75 individual trees sampled. We sampled 37 species of ants, distributed in 16 genera and five subfamilies. Ant richness differed among stages of succession and seasons, with higher number of species in the late succession and rainy period, also increasing with tree richness and density. Besides, there was a distinct composition of ant species among stages of succession and seasons. Results obtained in this study reinforce the importance of using ants as environmental bioindicators, since the sensitivity to environmental variations of this group enables us to differentiate early and late successional stages of forest succession in Caatinga environment.
Analyses of the headspace volatiles produced by males and females of Sternechus subsignatus Boheman (Coleoptera: Curculionidae) revealed seven male-specific compounds. The major component was (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, and the minor components were 1-(2'-hydroxyethyl)-1-methyl-2-isopropenylcyclobutane (grandisol), 7-methyl-3-methyleneoct-6-en-1-ol, (Z)-2-(3,3-dimethylcyclohexylidene)-ethanol, (Z)- and (E)-2-(3,3-dimethylcyclohexylidene)-acetaldehyde, and (E)-2-(3,3-dimethylcyclohexylidene) acetic acid. The latter compound is described for the first time as a natural product. Only four of the seven identified compounds showed electrophysiological activity. Enantioselective gas chromatography showed that the natural grandisol is the (1R,2S)-stereoisomer. The major component, (E)-2-(3,3-dimethylcyclohexylidene)-ethanol, attracted S. subsignatus in olfactometer bioassays. Studies are in progress to evaluate the biological activity of the major component and the EAD-active mixture under field conditions.
Upon damage by herbivores, plants induce an array of volatile organic compounds (VOCs) that mediate ecological interactions involving communication with organisms of the second and third trophic levels. VOC-mediated tritrophic interactions have largely been studied in various systems, including cassava (Manihot esculenta), but little is known about the chemical nature of herbivore-induced VOCs in this crop and the response they evoke in natural enemies. Several tetranychid and predatory mites are associated with cassava. Here, VOC emissions from uninfested plants and plants infested with 200 or 400 Mononychellus tanajoa, a specialist herbivore on cassava, and the generalists Tetranychus urticae and T. gloveri were measured. Dual-choice experiments were also conducted to assess the preference of inexperienced (reared on prey-infested bean plants) and experienced (adapted on prey-infested cassava plants) predatory mites, Neoseiulus idaeus (Phytoseiidae), between odors of uninfested plants versus odors of plants infested with M. tanajoa, T. urticae or T. gloveri. Two hundred individuals significantly increased the emissions of (Z)-3-hexen-1-ol, (E)-β-ocimene, β-caryophyllene, alloaromadendrene and (E)-geranyl acetone in T. urticae-infested plants, and (E)-β-ocimene and methyl salicylate (MeSA) in T. gloveri-infested plants. Four hundred individuals significantly increased the emissions of (Z)-3-hexen-1-ol, MeSA, α-pinene and D-limonene in M. tanajoa-infested plants. In addition, T. urticae at this density induced (E)-β-ocimene, D-limonene, (E)-geranyl acetone and six compounds that were not detected in other treatments. Tetranychus gloveri-infested plants induced the emissions of (E)-2-hexenal and D-limonene. Regardless of the infesting species, inexperienced N. idaeus did not discriminate between uninfested or infested plants. Upon experience, they discriminated between the odors of uninfested and T. urticae-damaged plants. Our findings reveal that mite infestations in cassava result in density-dependent and species-specific emission of VOCs, and that N. idaeus relies on associative learning to forage for its prey.
The calling behaviour of virgin females Condylorrhiza vestigialis Guenée, 1854 (Lepidoptera: Crambidae) and the female pheromone gland extract activity were studied under laboratory conditions. Most of the females started calling from their Wrst scotophase period after emergence. Maximum calling occurred between the seventh and tenth hours of the scotophase period. The length of the calling increased with age until the fourth scotophase, but the onset of calling time did not diVer with age. The number of calling bouts increased signiWcantly with age, but the mean duration of each calling bout (20.8 min) did not vary with age. Extracts of pheromone glands evaluated in a Y-tube olfactometer attracted signiWcantly more males than control, 70 and 30%, respectively. Gas chromatographic-electroantennogram detection (GC-EAD) analysis of these extracts indicated the presence of a single EAD-active peak, the putative sex pheromone of the species. This pheromone compound may be suitable for monitoring populations densities of C. vestigialis, and for detection of the onset of the seasonal Xight period. An eYcient pheromone is of importance also with respect to current attempts to develop new control methods for this important pest of Populus spp. in Brazil.
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