Starcraft – Squad selection in Starcraft

Queens are mainly casters with 4 main skills:

• It has the built in parasite spell that enables you to see the same things the host with the parasite can. (This can be removed only by the medic's restoration)
• It can Ensnare a group of units slowing them. This can be used to either prevent them from escaping or slowing their advance.
• Spawn Broodlings can also be researched to turn any ground unit into two broodlings, instantly killing the unit in the process. I don't know what mission your playing, but if that's the first mission in brood war, then you're supposed to use spawn broodlings on the ultralisks your about to come across, effectively rendering them useless. Alternately you can ensnare them and have your hunter killers have a go at them.
• Last but not least, they can infest a terran command center which turns said command center into a terrorist-training academy for suicidal infested terrans.

In Starcraft you can do it via a mod, but not by default (hack/mod)

In Starcraft 2 the default is F1, or the icon on the bottom left of your screen.