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Well, the first one is a assassin bug: http://en.wikipedia.org/wiki/Reduviidae
Not harmful for plants but for other insects.

The second one with wings is also a bug, but I don´t know what it will eat, insects or plant juice.

The last one is a weevil: http://en.wikipedia.org/wiki/Curculionidae
They eat plants.

I don´t think your friend should kill them ... only if there are too much of them. That´s nature.