[Queens' technic in Pharaoh's ant control. 2. Synergistic effects]

The alkylating (Tepa, Metepa, Thiotepa, Apholate) and non-alkylating (Hempa, Hemel) chemosterilants have been tested in a screening programme together with 6 synergists of insecticides (Pieronylbutoxide, Bucarpolate, Sulfoxide, Safroxan, Demethylsulfoxide, S-421) for cumulative and synergistic effects. Since all of the insecticide synergists were repellent in contrast to the chemosterilants, the substances have been screened only by the dipping test. The synergists increased in solutions of acetone in contrary to the chemosterilants not the mortality of the queens. A combination of Tepa acetone in contrary to the chemosterilants not the mortality of the queens. A combination of Tepa and Piperonylbutoxide resulted in real synergistic effects. The sterility of the queens of the pharaoh's ant was increased at a relation of 1 part of Tepa to 5 parts of Piperonylbutoxide up to twentyfold. It is probably the first evidence of synergism between conventional chemosterilants and insecticide synergists. Unfortunately this excellent effect can not be used for practical control measures because only the baiting method leads to an eradication. - All the other screened combinations showed neither cumulative nor synergistic effects.