Answer: Pediculus humanus, body or head lice.
It is not possible to tell body lice and head lice apart morphologically, although as L.R. says, head lice are generally smaller than body lice. Furthermore, as Vanessa CH points out, body lice are hardier than head lice and are much more likely to remain alive after being separated for more than 24 hours from their host. These lice were definitely separated for more than 24 hours (probably more like 48-36 hours) and therefore are more likely to be body lice.
Now as for what the 2 on the right are doing, that's an interest question! Thank you for the guesses. Despite some interesting speculation (fighting? mating? feeding on each other?) I think that B.A.M. got it right by saying that they probably are just stuck together and are trying to get loose. Recall that lice are used to attaching to hairs and probably just got tangled up in this artificial environment.