Several studies have showed how climate change is affecting both distributional range and phenology of numerous insect species. Range expansion of different insect pests can be enhanced by human mediated dispersal with the settlement of new suitable areas far from the native range In particular, inter- and intra- continental ornamental plant trade seems to play a key role in the dispersal. The pine processionary moth, Thaumetopoea pityocampa, is one of the main pest attacking pine forests in southern Europe This species showed in the last decades a range expansion due to the recent climate changes. The spread of the moth seems to be also enhanced by both accidental human transportation linked to ornamental tree trade, and host tree distribution outside forests. In this study we analyzed the genetic variability of pine processionary moth populations in the front expansion edge as well as in other areas of the native range, using 24 microsatellite loci. The main expansion patterns were outlined in relation to the host plant distribution and other environmental factors.