Additional Toll members in Drosophila (Toll-3, -4, -5, -7 and -9) apparently reflect gene duplication events in the fly lineage ( Fig. 4) or, in the case of Toll-9, arguably a loss in the honey bee and lepidopteran lineages. For instance, the ancestral Toll appears to have diverged into two different groups, Toll-1 and Toll-5, in flies. In contrast, Toll-1 remains the only member of this clade in honey bees. Similarly, the Toll-7/2 clade is represented only by a single honey bee homologue Am18w (Aronstein & Saldivar, 2005) . Presumably, the ancestral Toll 7/2 gene was duplicated in flies following their divergence 300 Mya from the lineage leading to honey bees. A protein named Apis mellifera toll7 (Kanzok et al., 2004) , seems more likely to be an orthologue of Toll-10. The five Toll receptors present in the A. mellifera genome (Toll-1, -6, -2/7, -8, -10) are also present in the sequenced genomes of other insects that belong to the orders Diptera, Lepidoptera and Coleoptera, with few exceptions. For example, whereas orthologues of Toll-6, -7 and -8 are found in D. melanogaster and A. gambiae (Diptera), Bombyx mori (Lepidoptera), and Tribolium castaneum (Coleoptera), Toll-1 appears to be absent from the genome of the lepidopteran insect B. mori, whereas Toll-10 appears to have been lost in the fruit fly. This suggests that these five genes encode the basic set of Toll receptors that was present in the common ancestor of these insects. These five receptors are highly expressed, in a dynamic and tissue-specific manner, during Drosophila embryogenesis (Kambris et al., 2002) . Of note, Toll-6 and Toll-8, are adjacent in both the D. melanogaster and A. mellifera genomes.