Welcome to the critique gallery Tom.
Im sure you are pleased with this; though the lens is not identified, I would guess a Tamron 90mm Macro?
You have a good overall exposure, and as you can see, parts of the spider are sharp and focused, and some are not. This is a shallow depth of field, and is quite typical when using a large aperture (large opening). F/4 gives a very shallow depth of field, whereas f/11 would provide better depth, with more of the Spider appearing sharp. Thats the key to macro shooting, especially insects, - get a good depth unless you want a super close macro of the head only, as an example. the out of focus areas here are a combination of spider parts close to the lens (the back of the spider) and further away, the rear legs.
The smaller apertures (f/11 is smaller than f/4, f/4 is smaller than f/2.8, etc) of course allow less light in, so you need to compensate by allowing a slower shutter, and/or a higher ISO.
So, with this, lets say you use f/11, its a good idea to keep that shutter speed where it is, leaving you ISO to tweak. Up to 1600 is roughly what you need, unless you use a slower shutter, and then youre getting into tripod territory.
I did upload a modification, cropped closer a little, slight sharpening and contrast, but its really as good as it gets at f/4. Scroll up and click the modifications tab, and view large.
I notice you used flash, - I assume the on-camera pop-up; it likely that it fired in a "fill flash" mode, meaning that it added a small amount of light, and wasnt the primary source. This is a good thing!
Google macro photography and you will find a wealth of useful information on the subject, which w3ill always include either images or descriptions of depth of field and apertures.