Remove 'a' from legend when using aesthetics and geom_text

Set show.legend = FALSE in geom_text:

ggplot(data = iris,
       aes(x = Sepal.Length, y = Sepal.Width, colour = Species,
           shape = Species, label = Species)) + 
    geom_point() +
    geom_text(show.legend = FALSE)

The argument show_guide changed name to show.legend in ggplot2 2.0.0 (see release news).

Pre-ggplot2 2.0.0:

With show_guide = FALSE like so...

ggplot(data = iris, aes(x = Sepal.Length, y = Sepal.Width , colour = Species,
                        shape = Species, label = Species ), size = 20) + 
geom_point() +
geom_text(show_guide  = FALSE)

I had a similar problem. Simon's solution worked for me but a slight twist was required. I did not realise that I need to add "show_guide = F" to geom_text's arguments, rather than replace with it the existing arguments - which is what Simon's solution shows. For a ggplot2 noob like me this was not that obvious. A proper example would have used the OP's code and just added the missing argument like this:

..
geom_text(aes(label=Species), show_guide = F) +
..