John, others much better than me will hopefully chime in but what I learned from Geoff and others on this thread is that for macro insect photos it's best to use an aperture much smaller than f4. Depth of field is critical and f4 provide very little.
Following Geoff's comments, I've used f14 recently and that seems to work well. A faster shutter speed would also be good, especially since you were using flash. I hope this helps.