Introduction of potential disease vectors into a new geographic area poses health risks to local human, livestock, and wildlife populations. It is therefore important to gain understanding of the dynamics of these invasions, in particular its sources, modes of spread after the introduction, and vectorial potential. We studied the population genetics of Aedes (Finlaya) japonicus japonicus (Theobald), an Asian mosquito that was recognized for the first time in the United States in 1998. We examined patterns of genetic diversity using random amplified polymorphic DNA and sequences of ND4 of mtDNA by comparing samples from populations spanning the range of this mosquito in Japan (six samples) and the United States (nine samples) as well as specimens intercepted in New Zealand in 1999. We found geographically differentiated populations in Japan, indicating limited gene flow even on small spatial scales. In the United States, we found evidence of significant genetic differentiation between samples from New York, Connecticut, and New Jersey and those from mid-Pennsylvania and Maryland. We were unable to pinpoint the source location(s) in Japan, although some of the U.S. samples are genetically close to samples from south Honshu and western Kyushu. Further studies should include samples from Korean populations. Distinct genetic signatures in U.S. populations undergoing expansion suggest the possibility of local increases in genetic diversity if and where they meet.

Desiccation survival times of adult mosquitoes were studied for yellow fever mosquito, Aedes aegypti (L.) (6 strains), Asian tiger mosquito, Ae. albopictus (Skuse) (5 strains), and Ae. paullusi Stone & Farmer (1 strain) colonized from South Sulawesi, Indonesia. At both 90 and 70% RH, Ae. aegypti males and females outlived the other species. The forest species Ae. paullusi was least resistant to desiccation. Strains of Ae. aegypti and Ae. albopictus from urban areas were more resistant to desiccation than conspecific strains from rural villages. When water was accessible, Ae. albopictus females outlived Ae. aegypti females, indicating that death from deprivation of water was not a result of energy depletion. Ae. aegypti was largest in body size, followed by Ae. albopictus and Ae. paullusi. Among strains within species, the relationship between body size and survival time was significant only for Ae. aegypti females at 70% RH. Adult desiccation resistance may be a factor that influences distribution and abundance of Aedes (Stegomyia) species.

We used two mitochondrial loci (nicotinamide adenine dinucleotide dehydrogenase subunit 4 and cytochrome oxidase II) and a nuclear locus (28S-D2 spacer) for a total of 1337 bp to evaluate the relationships among the four subspecies of Aedes (Finlaya) japonicus Theobald. Ae. j. japonicus was recently introduced into the United States and has been expanding rapidly. We also included in our analysis a morphologically very closely related species, Aedes (Finlaya) koreicus Edwards, as well as three more distantly related species: Aedes (Finlaya) togoi Theobald, Aedes (Finlaya) hatorii Yamada, and Aedes (Aedimorphus) vexans Meigen. We found that the four subspecies in the Ae. japonicus complex are genetically quite distinct but seem to form a monophyletic group that surprisingly also includes Ae. koreicus, suggesting the need for a taxonomic reconsideration of the group. We also found that the two southern subspecies are more closely related to each other than to any of the remaining subspecies or to Ae. koreicus and may indicate an ancient north-south split of the lineage. Considering the overlap between Ae. j. japonicus and Ae. koreicus, but the stronger association between Ae. koreicus and humans, we are surprised it also has not expanded from its original range. As a proactive reaction to this possibility, we designed and tested a DNA-based rapid assay to differentiate Ae. koreicus from some of the species with which it may be confused in the United States. These Aedes are putative vectors of several important viral encephalitides.

SummaryWe surveyed Nongceng, a village in a south-eastern province of Lao PDR, for malaria and its vectors. Nongceng is situated in a basin and surrounded by rice fields. In February 1998 (dry season), 28.6% of 126 villagers were infected with malaria, and in September 1998 (rainy season), 16.3% of 147 villagers. The prevalence of malaria infection was consistently high in children under 10, and the predominant malaria species was Plasmodium falciparum. In brief surveys of the mosquitoes performed on the same day as the malaria surveys, 2007 Anopheles females from 12 species were collected by means of human bait, animal bait and resting collections. Of the vector species known to be important in transmitting malaria in neighbouring Thailand -An. minimus, An. dirus, and An. maculatus groups -only An. minimus was found. Its density was, however, very low in both seasons and it was therefore unlikely to be the vector. In fact, An. nivipes accounted for more than 65% of all mosquitoes collected and was the most common species collected from human baits. The results of this study show that endemic areas of malaria in Lao PDR are not necessarily related to forest. Rather, An. nivipes is suspected to be the most important vector.

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Colonization of rice fields by mosquitoes and larvivorous predators was studied in asynchronous rice cultivation areas in the Philippines. Dipper samples were taken from rice fields at six phases of maturity (fallow, ploughed, nursery, newly transplanted, after tillering, mature). All phases were present concurrently at each of two study sites. Abundance levels of the vishnui subgroup of Culex and of the genus Anopheles were high in ploughed fields, nurseries, and newly transplanted fields; this was primarily because of the concentration of Culex vishnui. Theobald and Anopheles vagus Doenitz in those fields with short, sparse vegetation. Dytiscidae, Anisoptera, and Zygoptera were more abundant in fallow or mature fields. The abundance of aquatic predators decreased at the onset of ploughing and then recovered slowly as rice plants grew. The abundance of surface predators showed a similar pattern, but less conspicuously. The abundance of nonpredators (other than mosquitoes) was relatively stable with regard to rice field phases. Alleviation of mortality by predation was considered to be a secondary cause of increased mosquito abundance in the fields under early phases of rice cultivation.

Culicid and Chaoborid flies (Diptera: Culicidae and Chaoboridae) attracted to a CDC miniature frog call trap at Iriomote Island,