Biology and management of the masked chafer Cyclocephala distincta Burmeister (Melolonthidae, Dynastinae, Cyclocephalini)

Adults of Cyclocephala distincta are flower visitors of Neotropical palms (Arecaceae) and commonly found in the Atlantic Forest of Pernambuco, Brazil. Males and females were collected in the wild and subjected to captive rearing and breeding. The egg hatching rate, the life cycle, longevity of immatures and adults, and oviposition parameters in captivity were analyzed. The average duration of the life cycle of C. distincta was 108.2 days (n = 45). The egg stage lasted on average 10.9 days, and the egg-hatching rate was 73.9%. The immature stage lasted on average 93.4 days. The larvae stage exhibited negative phototaxis, and the size of their head capsules increased at a constant rate of 1.6 between instars, following Dyar's rule. The average duration of the first instar was 24.8 days (n = 88), whereas the second and third instars lasted for 17.2 (n = 76) and 40.4 (n = 74) days respectively, and survival rates were 21.6%, 86.4% and 97.4%. The pre-pupal stage was recorded, and pupal chambers were built before pupation. The average number of eggs laid per female was 15.5, the total reproductive period lasted for 3.3 days, and the total fertility was 81.2%. Adults that emerged in captivity exhibited an average longevity of 18.9 days. Adult C. distincta exhibited thanatosis behavior upon manipulation, a strategy observed for the first time in Cyclocephala.

Eclosion rate, development and survivorship of Aedes albopictus (Skuse)(Diptera: Culicidae) under different water temperatures

In tropical areas, where vector insects populations are particularly numerous, temperature usually range between 25°C and 35°C. Considering the importance of such temperature variation in determining mosquitoes population dynamics, in this work the developmental, eclosion and survival rates of the immature stages of Aedes albopictus (Skuse) were compared under constant 25, 30 and 35°C (using acclimatized chambers) and environmental (25°C to 29°C) temperatures. The hatching rate was considered as total number of larvae recovered after 24h. The development period as well as larval and pupal survival rate were evaluated daily. Eclosion rate was significantly higher under environmental temperature than under the studied constant temperatures, suggesting that temperature variation may be an eclosion-stimulating factor. The mean eclosion time increased with the temperature, ranging from 2.8h (25°C) to 5.2h (35°C). The larval period was greatly variable inside each group, although it did not differ significantly amongst groups (11.0 ± 4.19 days), with individuals showing longer larval stages in water at 35°C (12.0 ± 4.95 days) and environmental temperature (13.6 ± 5.98 days). Oppositely, survival was strongly affected by the higher temperature, where only one individual lived through to adult phase. The results suggest that population of Ae. albopictus from Recife may be adapting to increasing of environmental temperatures and that the limiting temperature to larval development is around 35°C.

Em áreas tropicais, onde as populações de insetos vetores são particularmente abundantes, as temperatura usualmente variam entre 25°C e 35°C. Considerando a importância dessa variação na determinação da dinâmica populacional de mosquitos, neste trabalho, desenvolvimento e as taxas de eclosão e sobrevivência dos estágios imaturos de Aedes albopictus (Skuse) foram comparados sob temperaturas constantes de 25, 30 e 35°C (em câmaras climatizadas) e ambientes (25°C a 29°C). A taxa de eclosão foi considerada como o total de larvas obtidas após 24h. O período de desenvolvimento, assim como a taxa de sobrevivência larval e pupal foram avaliados diariamente. A taxa de eclosão foi significativamente mais elevada sob temperatura ambiente comparada às constantes, sugerindo que a variação da temperatura pode ser um fator estimulante da eclosão. O tempo médio de eclosão aumentou com a temperatura, variando de 2,8h (25ºC) a 5,2h (35ºC). A duração do período larval apresentou grande variabilidade dentro de cada grupo, embora não tenha diferido significativamente entre os mesmos (11,0 ± 4,19 dias), tendo sido mais longo para indivíduos mantidos na água a 35°C (12,0 ± 4,95 dias) e temperatura ambiente (13,6 ± 5,98 dias). Ao contrário, a sobrevivência das larvas foi fortemente afetada na temperatura mais elevada, onde apenas um indivíduo alcançou o estágio adulto. Esses resultados sugerem que a população de Ae. albopictus de Recife pode estar em processo de adaptação ao aumento de temperatura e que o limite para o desenvolvimento de estágios larvais se encontra próximo a 35°C.

Reproductive aspects of the mosquito Culex quinquefasciatus (Diptera:Culicidae) infected with Wuchereria bancrofti (Spirurida: Onchocercidae)

This study reports on the relationship between Wuchereria bancrofti infection and female body size, intake of blood and fecundity in the mosquito Culex quinquefasciatus, vector of this filarial parasite in Recife (Brazil). Adults from field collected larvae were infected via a membrane feeding procedure, using blood with parasitaemia ranging from 724-6,000 mf/ml. A positive correlation was observed between mosquito size (measured by wing length) and egg production in uninfected females. However, this relationship did not exist in W. bancrofti infected mosquitoes. This change is unlikely to be the result of changes in blood ingestion as no significant difference was found when infected and uninfected females were compared. Variation in egg production observed between trials could not be associated with parasite density in the blood. These results suggest infection with W. bancrofti may disrupt the relationship between mosquito size and egg production during the first gonotrophic cycle of C. quinquefasciatus such that fecundity is sometimes reduced. However, this overall affect is variable and many groups of mosquitoes do not respond in this way

Primeiro registro de Aedes albopictus em área da Mata Atlântica, Recife, PE, Brasil / First report of Aedes albopictus in areas of rain forest in Brazil

Pela primeira vez é registrada a presença do Aedes albopictus em remanescentes de Mata Atlântica, localizada em área urbana em Recife (Pernambuco, Brasil). As coletas foram realizadas em isca humana e em criadouros de formas jovens (ocos de árvores, bambus, bromélias e pneu). A presença de Ae. albopictus na regiäo metropolitana do Recife representa um risco potencial do inter-relacionamento dessa espécie de mosquito com a populaçäo

Bloodmeal microfilariae density and the uptake and establishment of Wuchereria bancrofti infections in Culex quinquefasciatus and Aedes aegypti

The relationship between ingestion of microfilariae (mf), production of infective larvae (L3) and mf density in human blood has been suggested as an important determinant in the transmission dynamics of lymphatic filariasis. Here we assess the role of these factors in determining the competence of a natural vector Culex quinquefasciatus and a non vector Aedes aegypti to transmit Wuchereria bancrofti. Mosquitoes were infected via a membrane feeding procedure. Both mosquito species ingested more than the expected number of microfilariae (concentrating factor was 1.28 and 1.81 for Cx. quinquefasciatus and Ae. aegypti, respectively) but Cx. quinquefasciatus ingested around twice as many mf as Ae. aegypti because its larger blood meal size. Ae. aegypti showed a faster mf migration capacity compared to Cx. quinquefasciatus but did not allow parasite maturation under our experimental conditions. Similar proportions of melanized parasites were observed in Ae. aegypti (2.4 per cent) and Cx. quinquefasciatus (2.1). However, no relationship between rate of infection and melanization was observed. We conclude that in these conditions physiological factors governing parasite development in the thorax may be more important in limiting vectorial competence than the density of mf ingested.