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The identified characteristic of Fork head box (Fox) genes is the Fork head domain,a winged deoxyribonucleic acid (DNA)-binding domain,which indicated these genes encoding transcription factors.Invertebrate Fox genes have been classified into 23 subclasses,named from FoxA to FoxS,in which FoxR and FoxS subclasses are specific to vertebrates.In this study,by whole genome scan,we identified 17 distinct Fox genes which were distributed on 13 chromosomes in silkworm,Bombyx mori.The exon numbers of Fox genes were from one to nine,whereas the Fox proteins encoded similar domains.11/17 Fox genes have expressed sequence tags (ESTs).Microarray data revealed the Fox genes have distinct expression patterns in tissues at day 3 of the 5th instar larval.The phylogenetic tree demonstrated all silkworm Fox genes could be classified into 13 subfamilies.The FoxK subfamily was absent in silkworm whereas present in other Lepidopteran genomes (Danaus plexippus and Heliconius melpomene).Analysis of selective pressure indicated most of the amino acid sites in Fox proteins were undergoing purifying selection,except two sites of the FoxD protein were undergoing positive selection.Gene ontology (GO) analysis suggested Fox genes have important roles in cellular components,molecular functions and biological processes except pore complex biogenesis.Herein,we summarized the general characteristics of Fox genes in silkworm,and these results will support further functional studies on the silkworm Fox genes.