OBJECTIVETo generate life table characteristics for the dengue vector Aedes albopictus (A. albopictus) under uncontrolled conditions, incorporating both the aquatic and the adult stages.

METHODSTen females derived from wild pupae were allowed to fully blood-feed on restrained mice. 774 eggs were hatched in seasoned water. F1 larvae were followed for development until their F2 counterparts emerged as adults. Some population parameters were monitored (F1) or estimated (F2).

RESULTSA. albopictus exhibited increased fecundity and egg hatch success. Immature development was quick. Immature survival was high, with lowest rate in the pupal stage. Adult emergence was about 81% and sex ratio was close to 1:1. Generational mortality (K) was about 28%. A high proportion of females completed a reproductive cycle and the obtained parity rate was predicted to lead to higher fecundity in the next generation.

CONCLUSIONSIt can be concluded that natural A. albopictus populations in Penang seem largely determined by quick development in combination with low immature loss and increased oviposition.

Aedes ; growth & development ; physiology ; Animals ; Female ; Insect Vectors ; Malaysia ; Male ; Mice ; Vital Statistics

The medically important mosquito, Aedes albopictus is native to Asia and has become a major health concern in most Asian countries including Malaysia. Being recognized as a dengue vector, a clearer understanding of how mosquito populations are geographically connected, may therefore represent a profound yet significant understanding of control strategies. There are no documented reports on the genetic structure of Ae. albopictus populations from different developed settlements inferred from microsatellite DNA markers in Malaysia, particularly in Penang Island (Northern Peninsular Malaysia). Here, we assessed the molecular population genetics of Ae. albopictus in terms of their allelic variation, genetic diversity and population structure. A total of 42 mosquitoes were sampled from Jelutong, Batu Maung and Balik Pulau which represented urban, suburban and rural areas in Penang Island respectively and analysed for polymorphism at six microsatellite loci. All of the microsatellite markers were successfully amplified and were polymorphic, showing low genetic structure among geographic populations (FST= 0.0362). It is supported with admixture individuals observed in STRUCTURE and FCA and this suggests that high gene flow has been experienced between populations. These findings implicate passive dispersal through human-aided transportation; as a factor shaping the genetic structure of Ae. albopictus populations in Penang Island.

Plants contain numerous bioactive compounds that can be used to develop environmentally-safe insect control agents. Castor oil is a vegetable oil derived from the seeds of castor bean and is widely used as an industrial lubricant and medicinal purgative. In search of an alternative natural insecticide, the objective of this study was to evaluate the larvicidal and adulticidal activities of castor oil against the important dengue vector, Ae. aegypti. Larvicidal and adulticidal bioassays were conducted following the World Health Organization methods. Larvicidal activity was observed at castor oil concentrations of 10, 25, 50, 75, and 100 ppm; larval mortality was checked after 48 h of exposure and the lethal concentration (LC) at LC50 and LC90 were 51.38 and 116.26 ppm, respectively. Adulticidal activity was determined by topical application at the concentrations of 1, 5, 10, 15, and 20 µg/ mg on female mosquitoes and the mortality was checked after 24 h of exposure. The effective adulticidal activity was apparent with the LD50 and LD90 values of 6.03 and 25.07 µg/mg against female mosquitoes. The results indicated that castor oil has potential in the practical control of both immature and adult stages of the mosquito vector.