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Call number: LD2668 .T4 1948 O6 / Master of Science

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The objective was to quantify sublethal effects of two insecticides on the common damsel bug, a major predator in alfalfa. Groups of 2-day-old adult nabids were exposed for 12 h to filter paper treated with LC₅ or LC₄₅ carbofuran, or LC₅ or LC₂₅ methidathion. Males that survived the 4-day acute mortality period lived only 60 percent as long as control males, with low and high concentrations of insecticides producing similar decreases in longevity. More females who survived acute exposure to methidathion were missing portions of appendages at the time of death than in the controls. Although larger pronotal width was related to increased female longevity, to increased egg production, and to increased progeny production, exposure to insecticide had no consistently positive or negative effect. Pretreatment refrigeration affected neither postexposure longevity nor total eggs laid by females. Second instar nabids were exposed for 12 h on filter paper treated with LC₁₅ or LC₃₅ carbofuran, or LC₀ or LC₅ methidathion. Female nymphs which survived exposure to LC₃₅ carbofuran reached the 3rd instar more quickly than control nymphs, whereas methidathion tended to slow development to the 3rd instar. Neither insecticide significantly affected the duration of the 3rd-5th instars. While carbofuran reduced the longevity of adults compared to controls, methidathion only reduced the longevity of the LC₀ group compared to the LC₅ group. Although LC₁₅ carbofuran increased egg production per day alive, carbofuran did not affect total egg production. In laboratory studies male nabids were observed dispersing mistlike droplets (probably pheromone) by rapid movement of a hind leg, or by flicking, a term proposed here. Exposure to carbofuran or methidathion appeared to decrease the frequency of flicking in surviving nabids; however, the decreases were not always significant. Oviposition rates of control females averaged 3-4 eggs/female/d for adults from field-collected nymphs and 6 eggs/female/d for adults from insectary-reared nymphs with peaks around 18-22 d after the final molt. A tachinid, Leucostoma simplex (Fallen), was the most common nabid parasite reared (parasitization rates of up to 40%), while the braconid, Wesmaelia pendula Foerster, parasitized 0-4% of R. americoferus. / Ph. D.

The inheritance of resistance to chlordane in the German cockroach, Blattell germanica. (L.), was studied by determining the toxicity of chlordane to the following strains of roaches: a) chlordane-resistant and non-resistant strains, b)F₁ and F₂ progeny of reciprocal crosses between two parental strains, c) progeny of pair matings within resistant and non-resistant strains, and from a cross between resistant females and non-resistant males. / Ph. D.

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