Thirteen copies of the lexAop regulatory sequence are separated from a non-fluorescent 'spaghetti monster GFP' ('smGdP') marker by an FRT cassette containing stop sequences, which prevents expression of the marker in the absence of FLP recombinase. The smGdP marker consists of 10 copies of the Tag:FLAG tag inserted in groups into the backbone of the superfolder green fluorescent protein, which has been rendered non-fluorescent by mutation. A N-terminal myristoylation signal (Tag:Myr(Src64B)) is also present and the marker has been optimised for Drosophila codon usage.