More of the same, to be honest.
6 RHD, diminutive, and no ability bonuses apart from dexterity. This thing is arguably weaker than the bat swarm had they had the same amount of HD: with the locust having twice that -0 is the only thing I could reasonably assign.
The only Tiny-sized one amongst the swarms, which sadly mangles that magnificent weapon immunity. Low speed, bad ability scores, and no further special abilities beyond a weak disease force me to put this down as another -0.
Now this is interesting: a diminutive swarm with only 2 RHD! Tremorsense, a climb speed, and poison are all pretty nifty, and I think this one deserves +0 if only for giving access to swarm traits at a relatively low level. I admit it's close to -0, though.