Spectral index between 12 and 20 μm vs. the spectral index between 5 and 12 μm for all YSOs in Taurus from Furlan et al. (2006, 2008) and this work. Previously known transitional disks, i.e., disks with dust-depleted inner regions (CoKu Tau/4, DM Tau, GM Aur, UX Tau A), are shown with star symbols; protostars surrounded by envelopes and studied in Furlan et al. (2008) are plotted with circled diamonds (the smaller circles denote sources with more tenuous envelopes). Objects in the lower left corner are Class III objects.