By means of a minnow bioassay, the prothoracic defensive steroid titer of a population of Agabus seriatus (Say) was quantified at monthly intervals over a 15-month period. The titer of defensive steroid varied seasonally. A minimum of ca. 25 µg deoxycorticosterone (DOC) per beetle was observed in October and November. Through the winter and spring the steroid titer increased progressively and a maximum of ca. 60 µg DOC per beetle was reached in the summer months. During September, the steroid titer sharply decreased to the fall minimum.
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Miller et al. (1974) studied this question.