Termicin is a defensin-like antimicrobial peptide of termites that has strong antifungal activity. Fifty-six different termicin mRNAs encoding 46 different peptides were amplified and identified from Odontotermes formosanus (Termitidae), a species that inhabits environments with a large variety of microbial fauna. In contrast, only 38 different termicin mRNAs encoding 21 different peptides were amplified and identified from Reticulitermes chinensis (Rhinotermitidae). All mRNAs were amplified by reverse transcript PCR, with primers designed from reported termicin mRNA sequences. All of these genes showed high intraspecific sequence identity and were found to be highly homologous with other reported termicin genes. These two termite species live in different environments; the latter encounters relatively fewer pathogens in its habitat. We conclude that differences in microenvironmental pressure can affect the number oftermicin genes expressed in termite species.