I finally got the composition together, and recorded a video of the thing in action.
The video starts with the fireflies calibrating themselves to a dark room. Then they start blinking randomly and find a common rythm quite quickly. When I flick the lights on, they become confused (red flashes) because they are “used” to a darker ambient light level. Finally darkness falls upon the room again and the flies synchronize, this time with a quite nice melody.
petterniklas 
Is it possible to use a photodiode instead of phototransistor?
Thanx
I don’t know if you could just swap it out in the current cicruit. The phototransistor was probably chosen because it responds faster to changes in light intensity, and a phototransistor also produces more output current for a given light intensity than a photodiode. For a more definite answer you should ask Alex Weber over at tinkerlog.com, who designed the kit.
thanx
Hello.
Im very interested in this.
Can you enlighten about how you got Alex’s fireflies to play the tones?
Did you go in an program it?
If so do you offer the code for others to see somewhere?
Thanks
Nathan
I haven’t implemented this in hardware yet. The prototype is a pretty crude QC comp. that uses Image Pixel patches to detect flashes from webcam video input. The output is fed into the gates of Kineme Global Output MIDI Note patches. The MIDI notes are then routed to a standalone VST instrument (I think I used the free Kore Player from Native Instruments). There’s info on setting up the MIDI out part in this post https://petterniklas.wordpress.com/2009/08/04/midi-out-from-quartz-composer/ YMMV if you’re using 10.6 though. I changed my github repo to include all kinds of patches (including QC), added the comp I was using for this, and it can be found here: http://github.com/niklasekman/Petterniklas-patches
Thanks.
Midi and video is way out of my league at the moment. I might buy a few and try hardware.
Inspired.