Signal transduction and activation of transcription. Plays an important role in the segmental pattern formation in the early embryo by activating specific stripes of pair rule gene expression (By similarity). The STAT pathway directly participates in immune responses in insects. Forms a homodimer or a heterodimer with a related family member. Translocated into the nucleus in response to phosphorylation. Expressed in hemocytes, pericardial cells, midgut, skeletal muscle and fat body cells. Expressed at all developmental stages. Bacterial challenge results in nuclear translocation in fat body cells and induction of DNA-binding activity that recognizes a STAT target site. In vitro treatment with pervanadate (vanadate and H(2)O(2)) translocates protein to the nucleus in midgut epithelial cells. Belongs to the transcription factor STAT family.