1. The inheritance mechanism or resistance to lindane in the German cockroach, Blattella germanica (L.) was studied by determining the toxicity of lindane to the following populations ot cockroaches: a) lindane.resistant and non-resistant strains, b) the F1 and F2 progeny of reciprocal crosses between the two parental strains, c) the F1 and F2 progeny of backcrosses between the reciprocal cross F1 males. and resistant and non-resistant strain females, d) the progeny of pair matings within resistant and non-resistant strains and e) eight successive generation of a resistant strain isolated from further insecticide selection. 2. The method. employed in rearing the cockroaches and obtaining toxicological data on the different populations, as well as the genetical and statistical procedures, are described. 3. The toxicological data tor the mass matings are presented 1n the form of regression lines fitted by appropriate statistical analyses. 4. The toxicological data. for the pair matings, transformed into "indices of resistance," are presented in tabular form. 5.. Appropriate conclusions are drawn from the data to explain the inheritance mechanism of lindane resistance in the German cockroach. / Ph. D.

Dosage mortality data by a topical application method for eight organophosphorus compounds are given for two laboratory-selected .strains of Blattella p:ermanica ( L.), one resistant to malathion and the other resistant to diazinon. Comparison of this data with similar data for a normal susceptible strain of the same species reveals that development of resistance to malathion in this species is highly specific imparting no effective cross resistance to any of the other seven compounds evaluated. Selection with diazinon induces a low level of tolerance to all the organophosphates studied, but there are indications that in most cases this is due to vigor tolerance rather than to true resistance. There is reason to believe that if carboxyesterase activity is responsible for the resistance phenomena to malathion exhibited by this insect, its action is blocked or its detoxifying ability rendered ineffective by the presence of a vinyl group in an organophosphorus compound, such as GC 3707. / Master of Science