The effect of Bacillus thuringiensis var. Israelensis (serotype 14; IPS-78) on larvae of Toxorhynchites rutilus rutilus was determined in the laboratory. The survival of 4th-instar larvae exposed to 10 ppm B. thuringiensis (H-14) in the absence of prey was unaffected after 10 days of continuous exposure. Fourth instars exposed to 1.0, 5.0 and 10 ppm of the bacteria in the presence of excess prey (20 Aedes aegypti larvae) responded with 23, 62 and 95% mortality, respectively, after 10 days. One ppm B. thuringiensis (H-14) in the presence of 5, 10 and 20 Ae. aegypti larvae produced 9, 21 and 23% mortality, respectively, after 10 days. First instars were considerably more susceptible to B. thuringiensis (H-14) than were older instars. In the presence of excess prey, 98% mortality was observed 10 days after exposure to 0.5 ppm; those larvae fed on a nonliving diet at the same concentration responded with 80% mortality. No significant difference in mortality was observed between 4th instars exposed to excess prey at 1.0 ppm (IPS-78) or to cadavers of Ae. aegypti that had fed on 1.0 ppm B. thuringiensis (H-14) 24 h earlier. Neither blended cadavers that had died as a result of consuming B. thuringiensis (H-14) nor water in which cadavers had set overnight produced mortality in 4th instars of Tx. r. rutilus.
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Lacey et al. (1982) studied this question.