The 2 best times to kill moth are when they are fucking and when they are still caterpillars.
A few minutes ago I did both and killed another odd one.
This does not mean that it is wrong to kill the odd ones, but when you catch them fucking you get both the 2 for 1 deal, and more assurance that you caught them still fertile and should assume that it would have resulted in at least one new caterpillar.
Trying to catch them in their flight is harder, because they are good maneuverers and sturdy.
To catch them in their flight one has to apply accuracy and determination: leave your hands clapped and press them further, or otherwise the moth will manage to escape alive.
An hour or two later I killed another mating couple, another caterpillar and at least two more singles.