Fig. 1. (A) Western blot of protein extracts from Drosophila melanogaster and Planococcus citri probed with the D. melanogaster anti-HP-1 antibody as the primary antibody, and with goat anti-mouse IgG-HRP as the secondary antibody. Note the intense single band detected in D. melanogaster (lane 2), migrating, as expected (James and Elgin, 1986), at an apparent molecular weight of 34 kDa. P. citri protein extracts (lanes 3, 4) show two bands with apparent molecular weights of 29 and 46 kDa, respectively. The high molecular weight band is also present in control immunoblot (lane 6) probed with only the secondary antibody. M, molecular weight marker. (B) In situ immunofluorescence negative control, obtained by incubating cytological preparations with the secondary antibody only. Note the absence of any immunostaining on nuclei. Shown here are nuclei from a late blastoderm embryo. Scale bar: 10 µm.