Fagotto 1994, dashed line), normalized to the average redshift and magnitude of the low redshift RGs from Taylor 1996). The resolved BL Lac hosts lie quite well on the H–z relation. In Fig. 5 (lower panel) we show the H–z diagram for the mean values of various blazar and RG samples from the literature. These values consistently follow the H–z relationship (within the errors), with the average value for the BL Lacs derived in this work well matching the relationship.

In Fig. 6 (upper panel), we show the H–band host galaxy absolute magnitude vs. redshift for the BL Lacs (this work), FSRQs (KFS98) and RGs (Taylor 1996). In Fig. 6 (lower panel), the same diagram is shown for the mean values of various blazar and RG samples. The average H–band absolute magnitude of the seven clearly resolved low redshift (z$\leq$0.2) BL Lac hosts is M(H) = –25.8$\pm$0.5, and the average and median bulge scalelength R(e) = 8.8$\pm$9.9 kpc and 5.0 kpc. The host galaxies are therefore large (all have R(e)$\geq$3 kpc, the upper boundary of normal local ellipticals; Capaccioli, Caon & D’Onofrio 1992) and slightly more luminous than an L$^*$ galaxy (M(H) = –25.0$\pm$0.2; Mobasher 1993). Indeed, we find no 