My copy of Bug City lists the willpower for true form Ant warrior spirits as 2. Anybody seen errata that corrected this to willpower = Force lihe other spirits?

IIRC, most hive Bugs' queens have a power called something like "Hive Mind". By themselves, these spirits are fairly stupid, but they can share their queens mental abilities.

Looking through SR3, that doesn't seem to be a power still around (THat could be just something our GM used back then, dunno, I've never really used Insect SPirits in games I've GMed). But according to MitS, Ants have Willpower equal to their Force.

This doesn't appear an error, Bug City's insect spirits all have Willpower ratings of 1 or 2 except for queens/mothers. Grimoire 2 has these same stats. I don't know the reasoning behind MitS changing it.
Keeping the spirits at a low Willpower despite being physically powerful at high force and thus still vulnerable to mana based magic may have been the original idea. Depends on how you want to play them.

This was the norm for hive insect spirits back in the day.

The Queen's hive mind ability afforded the spirits some protection from mana spells and the like. I can't recall if this was detailed in Grimoire, Double Exposure or Bug City (I think it might be in the latter two) but basically the Queen could envelop the members of the hive in a "blanket of will" which let them use her willpower for resisting spells and the like (handy for avoiding pesky mind-probes on good merges as I recall)

Found the other reference I was thinking of in Magic In The Shadows. Willpower = Force in MitS. Willpower of 2 isn't reasonable to me. Insect spirits are supposed to be so nasty. With a willpower of 2 manaball works do well they are less trouble than any other type of spirit. Willpower = Force like all other summoned spirits makes them nasty.