Tholian

Tholans were first shown in the TOS series "The Tholian Web"

In the Enterprise episode "In A Mirror Darkly" Tholians appeared again. Unlike their TOS appearance, this time their entire body was shown. Tholians are an insectoid species.

Though they often claim (and fight over) territory they do not actually hold, Tholians seem to largely keep to themselves, as their small number of appearances since TOS will support.