The study investigated the development and stage specificity of physiological resistance to insecticides in a colony of
Culex quinquefasciatus
Say (Diptera: Culicidae) mosquitoes, which are vectors of bancroftian filariasis in India, after selection with deltamethrin. Resistance was selected by exposing the larvae to the concentration of deltamethrin that caused 50% mortality in the tested population (i.e., LC
50). Under continuous selection pressure, the LC
50 increased steadily in subsequent generations. The estimated LC
50 for the F
0 generation was 0.409 μg/L; the LC
50 first displayed a substantial increase in the F
5 generation (5.616 μg/L) and reached 121.902 μg/L in the F
10 generation. The objective of this study was to establish a deltamethrin-resistant colony to develop a research programme that will study the evolution of physiological resistance patterns and stage-specific resistance responses in Cx. quinquefasciatus larvae and adults under laboratory conditions. An approximately 298-fold increase in resistance was recorded after 10 generations, as evidenced by the resistance ratio (RR50). The progress and effect of the selection pressure in the adult stage was monitored with the World Health Organisation (WHO) diagnostic test. The mortality, as observed using the WHO diagnostic test, declined significantly from the F
5 generation (85%) onwards and the highest rate of survival (65%) was observed in the F
10 generation.
