Abstract
Larval crowding effects and oviposition preference of 7 strains of Culex tritaeniorhynchus from Far East were studied under laboratory condition. The 7 strains may be grouped according to the experiments into 3 types : (1) Strains Tt and O : The pupation rate at low larval density was higher than in OK-7 strain. No clear discrimination was made between tap water and the conditioned water which had contained the 1st-instar larvae for 1hr at 25℃. The gravid females were reluctant to oviposit on artificial food suspension. (2) Strain OK-7 : The pupation rate was lower in one larva per pot than in two or ten larvae per pot. The pupation rate decreased more sharply in overcrowded density. The ovipositing females showed a significant preference to the certain concentration of artificial food suspension. The females were reluctant to choose the conditioned water which had contained the 1st-instar larvae. (3) Strains A, N, Os76 and S : For the range of density favorable for their larval survival, the similar results to those obtained with strains Tt and O were obtained. However, the oviposition preference was intermediate between strains Tt and OK-7. These results indicate that C. tritaeniorhynchus is a variable species in the ecological characters. Discussion was briefly given on the divergence of oviposition preference for larval food among strains from viewpoint of productivity of larval food source in subtropical and temperate zones.
