Best-match honey bee sequences were then aligned with counterparts from D. melanogaster and A. gambiae, along with other insects where sufficient genome-level data were available. Amino acid sequence alignments were carried out using GONNET series weight matrices, with the program CLUSTAL_X (Chenna et al., 2003) . Alignments were used to propose phylogenetic relationships using maximum-parsimony and neighbour-joining algorithms, with the programs PAUP* (Sinauer, Sunderland, MA) or PHYLIP (http:// evolution.genetics. washington.edu/phylip.html). The PGRP tree is based on the conserved domain region only. Other alignments were edited manually to reduce or remove ambiguous regions. For scavenger receptor class B proteins, human (NP_005497) and mouse (NP_031669 CD36) proteins were added to alignments. Honey bee scavenger receptor AmelSCRB8 was not included because its relatively short predicted length (apparently the result of an intercontig gap) precluded an unambiguous alignment. All alignments are available on request.