Phosphorus Compounds as Ovicides and Adulticides against Body Lice1

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Abstract
Seventy-three phosphorus compounds were tested against laboratory colonies Pediculus humanus humanus. In acetone solutions parathion was the most effective ovicide, causing complete kill of eggs at a concentration of 0.0025%, and sulfotepp was most effective against adult lice, causing complete kill at 0.0000025%. Malathion and Chlorthion, which hold some promise for practical use in louse powders because of their low mammalian toxicity, were completely effective as adulticides at 0.001% and as ovicides at 0.05% and 1%, respecitvely. Malathion and Chlorthion in powders were about 97% effective as ovicides at 0.5% and 1%, respectively. Ovicidal action of O, O[image], O", O[image]-tetraethyl thiopyrophosphate was synergized by the addition of sulfoxide, but that of 3 other phosphorus compounds was not. Lice and eggs from a colony highly resistant to DDT showed no cross-resistance to 10 phosphorus compounds. The ovicidal effectiveness of malathion was directly correlated with the relative humidity, and that of malathion and Chlorthion with the age of the eggs. Pyrophyllite powders containing 0.1% of malathion or Chlorthion were completely effective against adult lice for 14 days.

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