Differences in volatile composition and sexual morphs in rambutan (Nephelium lappaceum L.) flowers and their effect in the Apis mellifera L. (Hymenoptera, Apidae) attraction

ABSTRACT We studied the volatile composition and sexual morphs of Nephelium lappaceum flowers from two orchards, and investigated the choice behavior of the honey bee, Apis mellifera toward the floral extracts from both locations. Our results showed significant differences in chemical composition and sexual morphs; only the hermaphrodite flowers from the Herradero orchard produced limonene and α-pinene and had longer peduncle and sepal than flowers from the Metapa orchard; on the other hand, the hermaphrodite flowers from the Metapa orchard had longer gynoecium. In the behavioral experiment the extracts from the Herradero orchard seemed to give A. mellifera foragers better cues for orientation to food sources, perhaps due to the presence of limonene and α-pinene, which are absent in the samples from Metapa. Such differences in both orchards could affect pollinator attraction and ultimately seed set and productivity.

Effect of Citrus floral extracts on the foraging behavior of the stingless bee Scaptotrigona pectoralis (Dalla Torre)

Effect of Citrus floral extracts on the foraging behavior of the stingless bee Scaptotrigona pectoralis (Dalla Torre). Stingless bees have an important role as pollinators of many wild and cultivated plant species in tropical regions. Little is known, however, about the interaction between floral fragrances and the foraging behavior of meliponine species. Thus we investigated the chemical composition of the extracts of citric (lemon and orange) flowers and their effects on the foraging behavior of the stingless bee Scaptotrigona pectoralis. We found that each type of flower has its own specific blend of major compounds: limonene (62.9%) for lemon flowers, and farnesol (26.5%), (E)-nerolidol (20.8%), and linalool (12.7%) for orange flowers. In the foraging experiments the S. pectoralis workers were able to use the flower extracts to orient to the food source, overlooking plates baited with hexane only. However, orange flower extracts were seemingly more attractive to these worker bees, maybe because of the particular blend present in it. Our results reveal that these fragrances are very attractive to S. pectoralis, so we can infer that within citric orchards they could be important visitors in the study area; however habitat destruction, overuse of pesticides and the competitive override by managed honeybees might have put at risk their populations and thus the ecological services they provide to us.

Extratos florais de Citrus no comportamento de forrageamento da abelha sem ferrão Scaptotrigona pectoralis (Dalla Torre). As abelhas sem ferrão têm um papel importante na polinização de muitas espécies de plantas nativas e plantas cultivadas em regiões tropicais. Pouco se sabe, no entanto, sobre a interação entre as fragrâncias florais e comportamento de forrageamento de espécies de meliponíneos. Assim, investigou-se a composição química dos extratos de cítricos florais (limão e laranja) e seus efeitos sobre o comportamento de forrageamento da abelha sem ferrão Scaptotrigona pectoralis. Nós descobrimos que cada tipo de flor tem a sua própria composição específica de mistura de compostos: limoneno (62,9%), e farnesol (26,5%) para flores de limão, (E)-nerolidol (20,8%), e linalol (12,7%) para flores de laranja. Nos experimentos de forrageamento, as operárias de S. pectoralis foram capazes de utilizar os extratos de flores para se orientarem até a fonte de alimento, não sendo atrapalhadas por placas com iscas apenas de hexano. No entanto, os extratos de flores de laranja foram aparentemente mais atraentes para essas abelhas operárias, talvez por causa da mistura particular do extrato. Nossos resultados revelam que essas fragrâncias são muito atraentes para S. pectoralis, assim pode-se inferir que dentro de pomares cítricos poderiam ser visitantes importantes na área de estudo; no entanto a destruição do habitat, o uso excessivo de pesticidas e a substituição competitiva por abelhas Apis poderia por em risco suas populações e, assim, os serviços ecológicos que prestam para nós.

Respuesta de Anopheles albimanus a compuestos volátiles de casas del sur de Chiapas, México / Behavioral response of Anopheles albimanus to volatile compounds collected inside houses from the south of Chiapas, Mexico

OBJETIVO: Determinar el efecto de los compuestos volátiles en las casas sobre la respuesta conductual del vector del paludismo Anopheles albimanus. MATERIAL Y MÉTODOS: El estudio se realizó en enero de 2006 en el ejido Nueva Independencia, municipio de Suchiate, Chiapas. Se colectaron compuestos volátiles dentro de casas y los extractos se probaron sobre hembras sin alimentar en un olfatómetro en "Y". Los extractos se analizaron mediante cromatografía de gases-espectrometría de masas (CG-EM). RESULTADOS: Se obtuvieron 28 extractos, 12 presentaron respuesta de atracción y dos de repelencia. Los análisis por CG-EM indicaron variación en la presencia de compuestos volátiles y no se vincularon con compuestos específicos indicativos de algún efecto. CONCLUSIONES: Los volátiles en casas presentaron efecto de atracción y repelencia para An. albimanus. No se reconoció un patrón definido en cuanto a la presencia de compuestos químicos característicos y la respuesta obtenida.

OBJECTIVE: To determine effects of volatile compounds in homes on the behavioral response of Anopheles albimanus. MATERIAL AND METHODS: The study was conducted in January 2006, in the village of Nueva Independencia village, Suchiate, Chiapas. Volatile compounds were collected inside homes and the extracts were tested on unfed females in a Y-olfactometer. Extracts were analyzed in a gas chromatography-mass spectrometry system (GC-MS). RESULTS: Twenty eight extracts were obtained, twelve presented attraction and two repellency responses. GC-MS analyses of the extracts indicated variation in the volatile compound present in the extracts, but could not associated specific compounds with any particular effect. CONCLUSIONS: Within homes, volatiles presented attraction and repellency responses to An. albimanus. A definate pattern concerning the presence of a characteristic chemical compound and the observed response was not found.

Behavioral and olfactory antennal responses of Solenopsis geminata (Fabricius) (Hymenoptera: Formicidae) workers to their dufour gland secretion

Behavioral and electrophysiological tests were performed to evaluate the responses of workers of the ant Solenopsis geminata (Fabricius) from different size categories to Dufour gland extracts. Morphometric measures based in head widths across eyes were used to determine worker sizes. Trail following response of different worker sizes to Dufour gland extract from workers of different sizes was assessed. For each worker size category olfactory responses to Dufour gland extracts were determined using electroantennography (EAG). Gas chromatography and mass spectrometry (GC-MS) were used to determine the chromatographic profile of Dufour gland secretion for each worker size. Morphometric measures permitted to classify the workers of S. geminata as large, medium and small workers. Medium S. geminata workers displayed a significantly higher behavioral response to Dufour gland extracts produced by medium size workers. Similarly, medium workers showed a significantly higher EAG response to Dufour gland extracts produced by medium sized workers. Chromatographic profile of Dufour gland secretions produced by workers showed that each size category exhibited a characteristic profile of the three main components considered as potential trail pheromone constituents. This work showed that medium workers of S. geminata exhibited a high trail-following behavior as well as a high antennal response to Dufour gland secretion. This and their relative abundance in field foraging areas, suggest that medium-sized workers are specialized in foraging activities.

Se efectuaron pruebas comportamentales y electrofisiológicas para evaluar las respuestas de obreras de Solenopsis geminata (Fabricius) de diferentes tamaños a extractos de la glándula de Dufour. Se usaron medidas del ancho de la cabeza para determinar el tamaño de las obreras. Se evualuó la respuesta de seguimiento de ruta de obreras de diferentes tamaños a extractos de la glándula de Dufour proveniente de obreras de diferentes tamaños. Para cada grupo de obrera de determinado tamaño se le determinó la respuesta olfatoria por medio de electroantenografía (EAG). Se utilizó Cromatografía de Gases acoplada a Espectrometría de Masas (GC-EM) para determinar el perfil cromatográfico de la secreción de la glándula de Dufour para cada grupo de obreras. Las medidas morfométricas permitieron clasificar a las obreras de acuerdo a su tamaño en grandes, medianas y pequeñas. Las obreras medianas de S. geminata exhibieron una respuesta comportamental alta a los extractos glandulares de hormigas medianas. Las obreras medianas mostraron también una alta respuesta antenal a los extractos de obreras medianas. El perfil cromatográfico de la secreción de la glándula de Dufour producida por obreras muestra que cada tamaño exhibió un perfil característico de los tres componentes potenciales como feromona de ruta. Concluimos que las obreras de tamaño mediano exhibieron altas respuestas tanto comportamentales como olfatorias a la secreción de la glándula de Dufour. Lo anterior y el hecho de que sean las más abundantes en el área de forrajeo sugieren que este grupo de obreras está especializado en actividades de forrajeo.