Edit: This might be a duplicate, but I could not find a similar sentence (like mine) in any of the other questions.
The eggs were harvested from our colony which have been in rearing for over 4 generations.
Using the info from the links given, I feel that if the sentence had specifically mentioned 'colony of ants', I feel 'have' would have worked. Is this an AE/BE thing? The article, I believe, was written by an American.
Since the 'colony' is the subject, I feel 'has' would be more appropriate. Am I right?