The incident happened at 1:00am when water from the Sultan Abu Bakar Dam in Ringlet was released after it breached the danger level.
The insect can also be very common where there are creeping thistles (Cirsium arvense) or swamp thistles (Cirsium palustre), oregano (Origanum vulgare), Forest scabious (Knautia sylvatica), or hogweed (Heracleum sphondylium) which are favourite foodplants of the imagos.