Apple Motion 2 Tutorials - Manual (Page 185)

Tutorial 4 Working With Particles 185
To adjust the Butterflies emitter:
1 With the Butterflies emitter selected, click the Emitter tab of the Inspector.
2 In the Cell Controls group, set Birth Rate to 3.
The number of butterflies decreases by a significant factor.
3 Set Scale to 60.
Each butterfly particle is scaled down to 60 percent of its original size. In order to create
variation in the size of the butterflies, change the Scale Range parameter.
4 Set Scale Range to 50.