|L B wrote:|
|MS Word tells me the second is correct,|
I'm pretty sure MS Word is right. The preposition "of" indicates the subject is the pair, and not the butterflies. It's as if you were saying "The axe of fire is deadly." Here, 'deadly' does not describe the fire, it's describing the axe.
(EDIT: another, better, example would be "The bottles of beer are full". Where we are describing the bottles and not the beer. Also sorry about "the axe of fire" nonsense.. I just got done playing Skyrim.)
|but I'm not trying to describe the pair|
Then you should not be making the subject the pair. "The two butterflies are alive" or simply "The butterflies are alive" both accomplish the same meaning while being grammatically correct.
Case in point, see firedraco's reply. He contradicted himself without realizing it:
|I would think 'are' is correct. You are describing the group of butterflies that happens to be a pair (two)|
Note he said "the group of butterflies that happens
The plural form here indicates the object is singular, which means the object is the group
, not the butterflies.
If he were [properly] describing the butterflies he would have said "happen" (singular). But I'm not sure that would be grammatically correct.