RESUMO: "Efeitos do óleo essencial de Pilocarpus spicatus Saint-Hilaire (Rutaceae) no desenvolvimento de ninfas de Rhodnius prolixus". Bioensaios contra ninfas de 5º estádio de Rhodnius prolixus foram conduzidos utilizando-se óleo essencial de Pilocarpus spicatus extraído por hidrodestilação. Os principais resultados podem ser resumidos como se segue: (i) altos níveis de toxicidade e paralisia associados à discreta inibição da muda foram induzidos pela aplicação tópica de 0,5 μL ou 1,0 μL do óleo essencial por inseto; (ii) fagoinibição parcial, altos níveis de inibição da muda, período intermuda prolongado e alto número de insetos paralisados mas ausência de toxicidade foram observados após tratamento oral com 5,0 μL ou 10 μL de óleo essencial de P. spicatus por mL de sangue ingerido. A importância destes resultados em relação a eventos biológicos relevantes em R. prolixus é aqui discutida. Unitermos: Rhodnius prolixus, Pilocarpus spicatus, óleo essencial.ABSTRACT: Bioassays against fi fth-instar nymphae of Rhodnius prolixus were conducted with essential oil of Pilocarpus spicatus extracted by hydrodistillation. The main results may be summarized as follows: (i) high levels of toxicity and paralysis together with discrete moulting inhibition were caused by topical application of either 0.5 μL or 1.0 μL per insect of the crude essential oil; (ii) partial fagoinhibition, high moulting inhibition, prolonged intermoulting period and high number of paralyzed insects, but no toxicity were observed after oral treatment using either 5 μL or 10 μL of Pilocarpus spilcatus essential oil per mL of ingested blood meal. The importance of these results in relation to the relevant biological events in R. prolixus is herein discussed.

Studies were carried out to evaluate the efficacy of the growth regulator, triflumuron (TFM) (Starycide ® sc 480 Bayer), for disrupting the development of Rhodnius prolixus fifth-instar nymph by oral, topical or continuous treatment. All treatments were able to induce high levels of mortality, delay development and molt inhibition. Oral treatment induced molt inhibition in all insects that survived at doses of 0.25, 0.50 and 5.0 mg/mL of a blood meal. The highest levels of both mortality in 24 h and molt inhibition were always observed after topical treatment. The lowest doses needed to obtain considerable biological effects were always observed after continuous treatment. In this way, the highest levels of mortality within 30 days were detected after continuous treatment, which also induced an extended inter-molting period, a lower number of over-aged nymphs and the highest level of molting in nymphs that survived. Moreover, the effects of TFM on insects were often displayed in a dose response manner. These results indicate that TFM acts as a potent growth inhibitor of R. prolixus nymphs and has the potential to be used in integrated vector control programs against hematophagous triatomine species.Key words: Rhodnius prolixus -triflumuron -benzoylphenylurea -chitin synthesis inhibitorIn search of alternative methods against insect pests that would avoid the harmful effects of conventional insecticides on both the environment and human health (WHO 2006), the insect growth regulators (IGRs) of the benzoylphenylurea (BPU) family were used against a wide range of crop, pasture and forest pests (Amir & Pevelling 2004) and also against disease vectors (Langley 1995, Rehini & Soltani 1999, Senthil-Nathan et al. 2006. The primary mode of action of BPUs is to disrupt chitin synthesis during larval development, which is the period that determines molting inhibition and/or malformations of the cuticle (Merzendorfer 2006). Since BFUs are relatively selective towards immature life stages of arthropods and are safe for vertebrates, they are often preferred over broad-spectrum insecticides when control operations against agricultural plagues are conducted in natural and semi-natural ecosystems (Sulaiman et al. 1994).Chagas disease (Chagas 1909) is an illness widely spread in South America that currently affects 18 million people (Garcia et al. 2007) by the dissemination by hematophagous insects such as Rhodnius prolixus. Furthermore, R. prolixus is traditionally used as a model for studies of insect physiology, control vector strategies and parasite vector interactions (Garcia & Azambuja 2004). Therefore, the aim of the present work was to investigate the biological effects of different doses and treatments , containing 48 g of TFM per 100 mL, was kindly provided by Bayer (Brazil) and directly used for the experiments using fifth-instar nymph of male R. prolixus (Hemiptera: Reduviidae). The insects were reared and maintained in the laboratory at 28 o C with a relative humidity of 60-70%, as described by Garcia et al. (...