PGRPs, major players in pathogen recognition (Hultmark, 2003; Steiner, 2004; Royet et al ., 2005) are less diverse in honey bees versus flies and other insects for which genomic data exist (e.g. the moth Bombyx mori ). There are only four PGRPs in the honey bee genome, compared to 13 and seven in Drosophila and Anopheles , respectively (Fig. 4A , Table 1 ). Further, bees show no capacity for the splice variation that contributions to diversify peptidoglycan recognition specificity in flies and mosquitoes. Specifically, the single membrane-bound PGRP in bees (PGRP-LC, GB17188) is similar to fly and mosquito PGRP-LC but lacks the potential to insert alternative peptidoglycan recognition domains by alternative splicing, a factor in recognition breadth for flies. PGRP-LC and PGRP-S2 are both up-regulated in honey bees after disease challenge (as in flies), suggesting that the products of these genes indeed play a defensive role (Fig. 3) . As in Anopheles , there is only one Class C Scavenger Receptor (SR-C) in the honey bee. This group has diversified into four members in Drosophila , three of which show selective signs suggestive of an immune role (Lazzaro, 2005) . There are 10 Class B scavenger receptors in the bee, a number roughly similar to that in the fly and mosquito (Fig. 4B , Table 1 ). Several other recognition classes also seem to be reduced in honey bees, including β -glucan recognition proteins ( β GRPs), galectins and fibrinogen-related proteins (Table 1) . Of these, the fibrinogen-domain genes are especially striking, due to the absence in bees of high lineage-specific diversification found in mosquitoes and Drosophila [resulting in 57 and 13 domain-family members, respectively (Christophides et al ., 2004) ].