Interspecific mating between Louisiana strains of Aedes albopictus and Aedes aegypti in the field and laboratory.

Interspecific mating between Aedes albopictus males and Ae. aegypti females was detected in the field using mark-release-recapture techniques. By 3 days after the release of virgin Ae. aegypti females into a field site containing only Ae. albopictus, 100% of the captured females were inseminated. Laboratory investigations indicated that male Ae. albopictus were very proficient at inseminating Ae. aegypti females and that Ae. aegypti males rarely inseminated Ae. albopictus females, especially if Ae. aegypti females were available. Most of the Ae. aegypti females inseminated by Ae. albopictus males contained only small amounts of dead sperm in their spermathecae, while inseminated females from the converse interspecific mating and from intraspecific matings contained only large amounts of live sperm. The results are discussed in relation to the decline in Ae. aegypti densities observed since the introduction of Ae. albopictus into the southern USA.

Habitat associations of mosquito and copepod species.

Copepods and mosquitoes were collected and identified over a 12-month period from three woodland ponds, discarded tires and a salt marsh. The species distribution of both mosquitoes and copepods varied among habitats and seasonally. Acanthocyclops vernalis was the predominant copepod in all of the habitats except the discarded tires, where Thermocyclops dybowskii was the predominant species. Amblyospora sp.-infected mosquitoes and copepods were found on several occasions in one of the woodland ponds and in the salt marsh. The results indicate that several copepod species have the potential to influence larval mosquito populations either directly as predators or indirectly as intermediate hosts of parasites.

Effects of sublethal exposure to Bacillus thuringiensis var. israelensis on larval development and adult size in Aedes aegypti.

The effects of exposure to sublethal concentrations of Bacillus thuringiensis var. israelensis (Serotype H-14) on second instar Aedes aegypti larvae were investigated. A test system was developed in which adverse effects would be detected as increased duration of larval development and decreased adult body size. No evidence of negative effects on survivors could be detected when sufficient B.t.i. dosages were applied to kill approximately half of the larvae in the treatment groups. However, when larval density was not controlled, and competition for food decreased as a result of larval mortality in the B.t.i.-treated groups, adult wing length was greater in the B.t.i. survivors than in the untreated controls. In addition, a residual mortality was noted in larvae that had been exposed to B.t.i. for 24 hr and then removed to habitats without B.t.i.