Fig. 1.— Color-color diagram illustrating our key target selection criteria. Objects with [3.6]-[4.5] < 0.25 and [3.6] -[24] < 0.5 are consistent with bare stellar photospheres. Blue dots are disk-less WTTSs from Cieza et al. (2007) used to define this region of the diagram. Red stars are all the 297 Young Stellar Objects Candidates (YSOc) in the Cores to Disks catalog of Ophiuchus. Most PMS stars are either disk-less or have excesses at both 4.5 and 24 µ m. Our 26 transition disks, shown as green dots, have significant ( > 5- σ ) excess at 24 µ m and little or no excess at 4.5 µ m, as expected for disks with inner holes. The 8 black dots are likely Be and AGB stars contaminating our original sample. – 50 –