Very cool shots!
The MP-E 65mm is a difficult lens to work with, but really amazing what it can do!
With greater than 1:1 magnification, depth of field gets so shallow. 1:1 is the maximum magnification most macro lenses can do. But with the MP-E 65mm it's that lens'
minimum... and it goes as high as 5:1. Manual focus only, too!
I see you used f/11 for your images. f/16 is the MP-E 65mm's smallest settable aperture... But due to the way the lens extends, that setting is an "effective f/96 aperture"! Even so, there's very little DoF at full 5:1... fractions of millimeters are in sharp focus!
You have to watch out for diffraction, due the small apertures involved. I ran into that with the image below that was done with the MP-E 65mm, at about 3.5:1 and with f/16 set. This is close to f/72 "effective" aperture, due to the way the lens extends at high magnifications.
"Effective aperture" actually has more to do with exposure than with diffraction or depth of field. TTL metering with the camera is no problem and will make for reasonably accurate exposures. But if using a separate meter, perhaps with manual lighting setup, it's important to take into consideration. There are details in the user manual for the lens (avail. to download for free from Canon websites, if you don't have it).
You didn't use flash? My snail "portrait" was done with the Canon MR-14EX ring light on the MP-E 65mm, with an 8:1 lighting ratio. Personally I don't care for ring lights at lower magnifications, but it's near perfect for use with this lens!
To deal with the ultra shallow depth of field, you might experiment with "focus stacking"... For example:
https://www.heliconsoft.com/heliconsoft-products/helicon-focus/ There are other software and devices for stacking, but the Helicon website has a lot of good examples illustrating it.
The multiple shots needed for stacking are difficult to impossible to do with live, moving subjects. Even that tiny snail was too quick for more than a single shot!
Some folks doing stacking use dead subjects. Interesting, but I think they tend to look "lifeless" (go figure
).
Another approach is to briefly refrigerate the subject so that they become immobile... then take your shots quickly before they warm back up and get active again!
If you try the refrigeration trick with any small critters... it might be a good idea to warn anyone else using the fridge!