Abstract
1. Mutant strains which exhibit "green" (Gr) and "orange" (Or) pigmentations at the 4th instar lavae were isolated from a colony of the autogenous form of the common house mosquito, Culex pipiens molestus. After selective breedings of such mutants for 4 generations, both Gr and Or could be established almost to the true breeding line strains, but the reverse selections for establishing white (Wh) strains which completely lack in such colour characters were rather difficult and the larvae at the generation were still ununiform in their coloration. 2. Crossing experiments were made on both sides with Gr and Or males and females. All the larvae at F1 generation were intermediate (Mix) in colour character. At F2 generation the larval colorations could be classified into Gr, Or, Mix and Ye by the ratios of roughly 12, 18, 67 and 3 percent respectively, in which a new character Ye appeared which could be differentiated by "yellow" coloration of the larvae. The adults reared from Ye were all males. 3. At the crossing between Ye males and Gr females, F1 larvae were all Gr and F2 were separated into the classes by ratios Gr 53%, Or 21% and Ye 26%, while F1 larvae obtained by the cross between Ye males and Or females were all Or and F2 were roughly Or 88% and Ye 12%. All of the adults reared from Ye were also the males, and the percentages of Gr females plus Ye males were always almost equal to that of Or females in all of these experiments. 4. The above genetical characters of Gr and Or are at most polygenetical in nature, and further genetical and biochemical studies need before these larval colour characteristics could fully be elucidated. 5. The above genetical characters were found to be useful markers in many ways in the researches on this species of the mosquito. As an example, the insecticides susceptibility of the non-selected parent colony and the Gr and Or strains were compared with DDT, dieldrin, lindane, fenthion, malathion, ronnel, dichlorvos, diazinon and Sumithion as the test insecticides, there are no significant differences could be detected. There seemed to exist no correlation between the above mentioned larval colour characters and the resistance to those insecticides.
