Quite a number of our Coleoptera are known to associate in their imago or perfect state with the Formicariæ—comprehensively, ants. Very little, perhaps nothing, is known of the larval and pupal life of any of these beetle. Some, like Batrisus bistriatus, probably never leave the ants; but others, like the species of Cremastochilus, desert them in the spring, whether afterwards to return and propagate among them is an open question.