Mosquitoes belong to order Diptera, sub order Nematocera and family Culicidae. Culexquinquefasciatus Say, is a medically important mosquito and major pest species with aworldwide distribution. Indiscriminate use of pesticides causes environmental constraints such ashealth problem, disturbance of natural enemies, eco-system and resistance development in insectpests. Therefore, the present study was planned to minimize the excessive use of pesticides bythe alternative novel chemistry insecticides. Susceptible (%) and resistance (%) status of 3 rdinstar larvae of Culexquinquefasciatus against conventional chemicals (Lamda-cyhalothrin,Permathrin, Deltamathrin) and new chemicals (Spinosad, Ivermectin, Emamectin) was determined by using their different concentrations rates viz., 100ppm, 125ppm & 150ppm afterdifferent exposure time (24hr, 48hr & 72hr). Generally, exposure time did not affect thesusceptibility and resistant % of Culexquinquefasciatus. Change in concentration directly affectsthe susceptibility and the resistance in case of both conventional and new chemistry chemicals.Lamda-cyhalothrine showing high value of LD₅₀ (1.80) while spinosad showing low value ofLD₅₀ (0.03). The Value of LD₉₀ is high in Deltamethrin and spinosad is lowest value in alltreatments.

Keywords-Culexquinquefasciatus, Health problem, Pesticides, Resistance.