The effects of certain age factors on the response of the German cockroach to insecticides

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Virginia Polytechnic Institute


Two age factors were studied: the age of the roach at the time of testing, and the age of the female parent at the time reproduction occurred. Age groups from 1-3 days to 25-28 days were used to test the first factor and the first three egg eases were used to test the latter.

Age was found to be a statistically significant factor when malathion, aldrin, and DDT were tested on both sexes of the normal strain. However, because of inconsistencies and a lack of differences of any great magnitude, it is believed that the differences in all but the aldrin tests were of no biological significance. In the aldrin tests it appeared that as the age of the roach increased, susceptibIlity gradually increased. The tests using aldrin on the Aldrin-resistant strain were significant for the females. Resistance in this strain appeared to increase from the 1-3 day age group until it reached a peak in the 10-12 day age group, then decreased to a level equal to or lower than that of the younger age groups. Statistical significance was found for the parental age factor in about one-half of the tests. However, it was of little biological significance because the variations were of a small magnitude and inconsistencies between the males and females occurred of ten.