These are neat. With the energy drain, I guess we should mention that there's no Fort save needed to remove the negative levels after 24 hours, huh?
A strict interpretation would be "no". I'm fine with going that route or the traditional energy drain approach.
Added to Homebrews.
Updated.
Retain the locust swarm's +4 racial bonus on Listen and Spot?
Skills: Hide +16, Listen +4, Spot +4, 9 ranks
Feats: 3
Organization: Solitary or x (2-4 swarms) [x="infestation"?]
Challenge Rating: 4? (Energy drain has to at least add +1 CR over a locust swarm)
Since they are "eerily silent", how about adding a racial bonus on Move Silently, throwing some ranks in it, and giving 'em Stealthy rather than Iron Will?