Abstract
On the basis of L.D.50 in dust tests, natural pyrethrins were 2.8 times as toxic as allethrin, and in spray tests 10.9 times as toxic, against the armyworm (Cirphis unipuncta). On the same basis, they were about 14.2 times as toxic in dust tests, and only 3.8 times as toxic in dipping tests, against the pea aphid (Macrosiphum pisi). But allethrin was 2.3 times as toxic as natural pyrethrins against the milkweed bug (Oncopeltus fasciatus).

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