Thanks drjax and alab. After a bit of head scratching, the penny finally dropped! That's actually a very clever clue.
Staring at it, made me realise I hadn't parsed 3d either, so I was wondering if I'd got both 9a and 3d wrong. Then after getting 9a, the penny dropped for 3d also!
Re 1d, did anyone else think, not just rulers, but also butterflies?!