A β-actin gene, Libβ-actin1, from the psocid, Liposcelis bostrychophila, was isolated, sequenced, and expressed inEscherichia coli. The cDNA sequence was 1 281 bp in length and contained an open reading frame of 1 131 bp encoding376 amino acids with a predicted molecular weight of 41.82 kDa. According to a BlastN search, the coding region sharedthe highest identity (97%) with Pediculus humanus actin 5C, while the deduced amino acid sequence was completelyidentical to a mutant of Drosophila melanogaster actin 5C. Comparison of the nucleotide and deduced amino acidsequences confirmed the high similarity between Libβ-actin1 and homologs in other insect species. The 3´ untranslatedregion (3´ UTR) of the Libβ-actin1 mRNA had a high A+U content (approximately 75%) and contained three repeats of theAUUUUUA and AUUUA motifs, which may play a role in regulating mRNA decay. The expression of Libβ-actin1 wasfurther analyzed in insecticide induced and control psocids. The results indicated that there was no significant differencein expression of Libβ-actin1 between the induced and control groups, suggesting that Libβ-actin1 may be an appropriateinternal control for the gene expression profiling in this insect. Furthermore, Libβ-actin1 was also heterologouslyexpressed in Escherichia coli, which provided a basis to investigate the physiological functions of actin genes in thepsocid.