  We study the short-term evolution of starspots on the ultrafast-rotating star
HD197890 ("Speedy Mic" = BO Mic, K 0-2V, P_rot = 0.380 d) based on two Doppler
images taken about 13 stellar rotations apart. Each image is based on spectra
densely sampling a single stellar rotation. The images were reconstructed by
our Doppler imaging code CLDI (Clean-like Doppler imaging) from line profiles
extracted by spectrum deconvolution. Our Doppler images constructed from two
independent wavelength ranges agree well on scales down to 10 degrees on the
stellar surface. In conjunction with nearly parallel V-band photometry our
observations reveal a significant evolution of the spot pattern during as
little as two stellar rotations. We suggest that such a fast spot evolution
demands care when constructing Doppler images of highly active stars based on
spectral time series extending over several stellar rotations. The fast
intrinsic spot evolution on BO Mic impedes the determination of a surface
differential rotation; in agreement with earlier results by other authors we
determine an upper limit of |alpha| < 0.004 +- 0.002.
