I like the monochrome that's going on here. It's a good picture but not perfectly sharp, but that's most likely because you've got a living subject there, so even the slightest movement of the insect will probably throw off alignment. Do you shoot on a tripod or handheld? 1/5 is a pretty long exposure, so you might even get some motion blur in every photo.
Additionally do you use focus bracketing or a focusing rail? Maybe your step size per image is too big? For my pictures I found that the smaller the step size i use and the more photos i take when bracketing, the sharper the final result will get.
Edit: Just saw that you have given those infos.