All most missed this..Hard to take that TC off but for shots like this, ya, ya easy to plan for, you can get more DOF at f8 if you do. I would not go past f11 with the combo, you want detail with the DF and that lens goes into defraction at a fairly low f stop. OR you can be back a bit more= increase DOF and crop, that combo works well with hefty crops.
I love the damselfly and I think Sean is right that the shell is it's cast off nymph casing. That's totally cool.The DOF is a bit shallow here, and I'd like the damselfly a little brighter, but understand you were flirting with blown highlights in the lily flower.