However, you could use some general collective nouns that fit:
* A nest of hornets (this is the most common and natural choice)
* A swarm of hornets (especially if they are flying around in a large group)
* A colony of hornets (emphasizing their social structure)
You could also get creative and use a less common term:
* A fury of hornets (emphasizing their aggressive nature)
* A cloud of hornets (describing their appearance)
* A hive of hornets (referencing their dwelling)
Ultimately, the best collective noun depends on the context and the desired effect.