Self-recognition is essential for the maintenance and reproduction of organismal integrity throughout the biological hierarchy, such as immune system and self-incompatibility in cellular level and territoriality in individual level. Social insects also maintain colony cohesion by self-recognition to discriminate non-nestmates. Despite the key role of chemical cues, the comprehensive understanding of nestmate recognition mechanism from genomic level to behavioral level is still incomplete due to difficulty of separating the genetic and environmental factors. Therefore, we tried to isolate the effect of non-genetic factor for nestmate recognition in insect society by generating genetically identical colonies of a parthenogenetic ant. Here we report that colony level identity changed within clonal colonies derived from a parthenogenetic strain of a thelytokous ant. We artificially divided a colony and put a worker from both colonies into small arena. The time length of touching each other with antennae was recorded. Workers spent more time touching the counterpart from divided colony than their nestmates. In addition, the touching time increased with the number of days after the colony division. Our finding will offer a unique opportunity to evaluate accurately genetic, molecular and chemical mechanisms underlie self-recognition observed among social insects.