Music Composers Unite!
I can't speak for the flute part, since I'm not a flautist, but one thought that occurred to me was to leave adequate breathing points. Your flute passages are a bit virtuosic, and in high register, so you probably want strategic breathing spots so that your flautist doesn't run out of air and peter out in the middle of an exciting run. :-)
Another note is that m.9 has an unplayable piano part: you're asking the pianist to play a 2-octave interval with his left hand, but I don't think any living pianist has hands that large. :-P In the same bar you also have an 11th, which is pretty hard to play for normal hands. ;-)
Also, while the piano accompaniment isn't bad, there are some parts where I felt the left hand part was a bit too boring -- just quarter notes or dotted half notes. In some spots I almost wish the piano, esp. the left-hand part, would do something more interesting, like maybe echo some motifs from the flute part, or play a counter-rhythm to the flute, or something. Perhaps something even more frenetic-sounding to reflect a bat's haphazard flight.
Other than that, it's a pretty fun piece. I think I like it too!