They change the number at random intervals and if you miss a sign. What a gotcha!

Would we might vote with equal ease, / As think what reälly we please! / Oh! for the placid ballot-box, / When at our ribs our conscience knocks! / […] / [Oratore, H. B. Chapman.]

a plausible excuse

The perch, for example, regards the danger as exaggerated: all one needed was to exercise moderation, as a fishly virtue; it had bitten off many a bait without suffering any damage to its body.