Cooperates with insulin-like peptides to stimulate the proliferation, polarization and motility of imaginal disk cells. May act by stabilizing the binding of insulin-like peptides to its receptor through a simultaneous interaction with both molecules to form a multiprotein signaling complex (By similarity). Secreted in hemolymph. It is probably transported to target tissues via hemolymph. Glycosylated. Belongs to the glycosyl hydrolase 18 family. IDGF subfamily.