Membrane attack complex / perforin-like (MACPF) proteins are well known for their roles in mammalian immunity and defence against pathogens where they function to disrupt cell membranes by forming oligomeric pores. However, several MACPF proteins perform essential, but poorly understood roles in development. In Drosophila, specification of the embryo termini is governed by a localised interaction between the receptor tyrosine kinase Torso (Tor) and its ligand Trunk (Trk). It has long been presumed that Trk must be cleaved in order to bind Tor, and that these proteolytic events are controlled by secretion of Torso-like (Tsl), a MACPF protein present only at the embryo termini. However, we have recently shown that while Trk must be cleaved in order to bind and activate the Tor receptor, this process occurs independently of Tsl function. By visualising Trk localisation in live embryos we found that it is not, as previously believed, ubiquitously present in the extracellular space surrounding the embryo, but is instead found only at the embryo termini. Strikingly, this localisation is highly dependent on Tsl, suggesting that localised Trk secretion may be the mechanism that restricts Tor activation to the embryo termini. Together, these data represent a new paradigm for the spatial control of receptor tyrosine kinase signalling by localised growth factor secretion, and define a new role for perforin-like proteins in eukaryotes.