[David]

It is not a good idea to flush water on the ants unless you are careful enough not to pour water into the pitcher. I am guessing the dead ants are around the peristome area. If you pour water into the pitcher the digestive fluid in the pitcher will be diluted. This would upset the chemical balance in the digestive fluids.

It is also normal for a lot of ants to be attracted to your pitchers. It is a symbiosis between Nepenthes and ants. The traps of the pither plant is such that not all ant that visits it's pitchers get caught. This is logical because if the first ant that found the nectar is caught, it will not be able to go back to its nest and bring a whole army to harvest the nectar.

So it's kind off a give-and-take situation between plant and ant. The pitcher plants offer food (nectar) to the ants. In return the ants sacrifice some of their worker ants for food to the pitcher plant.

Sometimes when the pitcher produces alot of nectar around the peristom ants do get caught in the sticky nectar. When the sticky nectar covers the ants body it suffocates the ants. Pitcher plant nectar is also known to have a slight effects similar to alchohol on insects. Perhaps the ants were drunk on pitcher nectar and fall on the nectar instead of inside the pitcher. But no worries as this does not have any ill effects on your neps.

If you want to use a mosquito/cocroach spray/arosol to kill the ants and you want to spray on the plant itself, use waterbase arrosol. Normal sprays is about 80-90% percent petroleum base. Not good for your Neps.