Zergling (StarCraft II)

Zerglings have evolved, affecting such things as their appearance. They develop small wings when given the speed upgrade.

Zerglings have been reduced in size and have much better path-finding than in StarCraft I.

Zerglings are strong against marauders and stalkers, and weak against hellions, archons, and banelings.

Strategies
Zerglings are very useful for an early rush. If the opponent masses units or builds defensive buildings you can morph some of them into banelings, a superior choice against some unit types.

Zerglings are useful even into the late game due to their ability to surround opponents quickly.