Do swarm of the same species attack each other?
It will depend on the species and group you're talking about. If the species is territorial, one swarm will tend to chase the other away. If it's a locust, they'll merge until they get to trillions of tons...

A study on wasps (Vespidae) I've read years ago showed an interesting experience. One individual wasp was tied by the waist and put close to different nests. The violence demonstrated by the nest was greater in a different species, median in the same species with a greater genetic distance, and none to her own or related nests.

Some "solitary" bees are very interesting in this respect, because they show many different kinds of sociality in related or even the same species, like many Halictidae and Euglossina (Apidae).