Ectopic Branchless (Bnl)/FGF expression arrests fusion-cell (FC) migration. Local IR illumination was directed immediately dorsal to the dorsal-branch tip (asterisk at 0:00:00) in HS-GFP/dys-Gal4; UAS-GFPN-lacZ / HS-Bnl, and btl-RFP-moe embryos. Images were taken every 295 sec. Arrowhead: GFP (and Bnl/FGF). Arrow: the affected FC. Scale bar: 10 μm.