bartered May beetles for Beatles tapes
Footnote 1 tells you what it is. It can’t show you one, and the trade only works if you know what was on the other side of it.
A currency about four centimetres long that arrives on its own schedule in May, flies badly, thuds into lit windows all evening, and can be caught by hand.
Melolontha melolontha — taking off

CC BY-SA 3.0 · Mario Sarto · Wikimedia Commons · licence