Can Summon Minor Monster summon swarms?
This spell functions as summon monster I, except you can summon 1d3 Tiny or smaller animals, such as bats, lizards, monkeys, rats, ravens, toads, or weasels. The summoned animals must all be the same type of creature. As with animals summoned with summon monster I, you may apply one alignment-appropriate template to these animals.
The only limiting factor in this spell is that all creatures summoned by this spell must be tiny or smaller, animals, and the same creature.
A Venomous Snake Swarm meets all of these requirements.
No, because swarms are always more than 1d3 animals.