Ozone Toxicity During Ontogeny of Two Species of Flour Beetles,Tribolium confusumandT. castaneum1

Studies of 2 species of flour beetles, Tribolium confusum (du Val) and T. castaneum (Herbst), were conducted to determine the toxicity of ozone given at specific life cycle stages. Toxicity was measured in terms of adult survival one mo posteclosion. Results indicated that the younger larval and pupal stages of T. castaneum were more ozone sensitive than similar older stages; 28-d-old pupae were the most ozone resistant of the stages tested. For a given stage, the younger forms of T. confusum were more ozone sensitive than older ones. Ozone resistance of T. confusum progressively increased with age, except the resistance of 20-d-old larvae was comparable to that of adults: In general, all stages of T. castaneum were more ozone sensitive than those of T. confusum ; however, for both species the l5-d-old larvae were equally sensitive at each exposure, as were the 28 d pupal stages. The hours of ozone exposure for 100% lethality of 15-, 20-, 23-, 28-d-old forms and adults ( T. confusum : T. castaneum ) were 3½:3½; 6½:5½; 5½:3½; 6:6; and 6½:5, respectively.