Cheers mongoose.
The pictures should link to the flickr pictures, which also have the full sized ones available. Im not sure what aperture they were, but think they were all mostly around thr 5.6 mark.
Thats wide open for this lens at 300mm so you wont be getting its best work. F8-F10 is the sweet spot for most lenses, but obviously youll have to ballance this against slower shutter speeds or higher ISO. Close ups of living things are tricky! which of course is what makes them fun, and adds to the satisfaction when you manage to get a good one.
Another good reason for stopping down when close in is that the depth of field is tiny at such close distances. It takes some doing to get the focus and angle just right so that enough of the critter is in focus that it doesnt notice. Particularly with something the size of a dragonfly, getting the whole thing in focus is often at odds with an interesting composition.