Representation of the known Hox expression domains in the segments of A. longisetosus , the spiders Cupiennius salei and Parasteatoda tepidariorum , and the harvestman Phalangium opilio . (A) The known Hox expression domains in the mite A. longisetosus. Expression data for pb, Dfd, Scr, and Antp from . Expression data for Hox3 from  and Ftz expression from . Question marks for Hox3, Dfd and Antp denote the unknown late-expression patterns in the Te (see text). (B) The known Hox gene expression domains for the spider C. salei. lab, Antp, Ubx-1 and 2 and abd-A expression from ; pb, Dfd-1 and 2 and Scr-1 and 2 expression from . Note that Scr-2 expression was not observed in L2; Hox3 expression from ; Ftz from ; Abd-B from . (C) The known Hox expression domains for the spider P. tepidariorum. lab, Dfd, Scr, Antp, Ubx, and abd-A modified from  and pb and Hox3 from . (D) The known Hox expression domains for the harvestman P. opilio, adapted from . Shaded bars indicate weak expression; however, the shaded bar for Abd- B expression in A. longisetosus denotes its early expression in the Te and subsequent clearing from this tissue. abd-A abdominal-A; abd-B, Abdominal-B; Antp, Antennapedia; Ch, chelicerae; Dfd, Deformed; ftz, fushi-tarazu; L1-L4, first through the fourth walking legs; lab, labial; O1-O12, first through twelfth opisthosomal segments; pb, proboscepedia; Pp, pedipalps; Scr, Sex combs reduced; Te, telson; Ubx, Ultrabithorax.