Beating the odds

Any elephants in the Empire will remember I found just one iris egg this year, which hatched into a tiny person I named Tiberius. I lost Tiberius in his second instar, in September, despite examining every single accessible leaf on his sallow tree on three different occasions. Today I found him again, now in his third instar:

I speculate he spent much of his second instar higher up the tree where I couldn't see him and has now been driven lower again either by the leaves dying off sooner up there or by the lousy weather we've had recently.

Whatever, it's good to see him. What are the odds of finding a single egg, just after it was laid, and for the caterpillar still to be around two months later?

Guy