Caterpillar of Cephonodes kingii, SPHINGIDAE,
with white spiracles outlined in red along its sides
The spiracles along the sides of the abdomen of a moth, through which air diffuses, are very narrow. Given the high surface tension of water, no water actually enters the spiracles. So the moths will survive immersion on the air already trapped internally in the trachea until the oxygen therein is exhausted by metabolic absorption. The moths being cold blooded and immobile, this can be several hours.
(written 11 March 2020)