Maybe I'm too empathic, but I would always assume animals have feelings, feel pain etc. and try to prove otherwise. Not the other way around.
It's interesting that your empathy would necessitate that they had feelings to begin with.
There's good reason to believe that there isn't. Which means it's ultimately a political question and will always have an arbitrary answer.
Have not seen a convincing argument that we will not find an evolutionary line in the sand between sentient and automaton animals.
Evolutionary success creates only the illusion of lines, none really exist.
Reality has very few lines.
Using an unnecessarily strict definition for line, you'll find there is almost nothing in the universe that is perfectly distinct:
There are no species, no genders, no living things, dead things, no discrete individuals, not even any discrete objects, no colors. Nothing is high, nothing is low, nothing is dark, nothing is bright; nothing is anything.
We can obviously draw a boundary between quadrupeds and bipeds -- we're doing it the second we use the words. Whether that boundary is absolute is not valuable.
The interesting question isn't "Can we argue for a continuum of awareness between insects and humans?" That part is easy.
The interesting part is, "Do we know enough about consciousness to describe a meaningful boundary between them?"
I don't take it to an extreme -- I regularly splatter bugs on the windshield of my car. Though, it's fun to view it from the prospective of a potentially conscious bug, fighting the invasion of the scourge of the giant genocidal automobiles, bugs suicidally hurtling themselves at the attackers in a futile attempt to defeat them. I also don't extend the courtesy to plants.
Why? Life is precious and rare, regardless of what form it's in. Just the fact that we don't know if these creatures have a consciousness is enough for me. Someone with an IQ of 1 deserves to live as much as anyone else.