according to the april 19, 2009 issue of news of the weird:
Biologist Michelle Solensky, of Ohio's College of Wooster, reported late last year in the journal Animal Behavior that male monarch butterflies are such calculating inseminators that they even decide the optimal level of sperm necessary for reproductive advantage. While injecting fluid, the male can "selectively" determine how much of it will be fertility cells, depending on how much residual sperm the female holds from previous suitors (and thus to always inject more than the other guys did). Solensky told New Scientist magazine that the penis acts as a kind of "dip stick" to check the quantity already present. [New Scientist, 1-7-09]
reading this leaves me with one question, and one question only: are you thinking what i'm thinking?