The scene you're describing is a follow up to this exchange at the beginning of the episode.
NEELIX: And now, for some more of Zefram Cochrane's favourite music. Hey, come on, Mister Vulcan.
TUVOK: Vulcans do not dance.
NEELIX: But it's tradition.
TUVOK: There is no tradition, Mister Neelix. This ceremony is entirely your invention.
JANEWAY: This is an official ship function, Commander. Don't make me order you to dance.
Later, when Neelix is leaving, Tuvok is doing a little mini twist (the dance) to show Neelix that he respects him and will miss him by putting himself out and to some degree embarrassing himself by dancing.
So.... bottom line, that particular scene is no evidence of whether there are insects on Voyager.