But I see no reason for some cutoff, where I arbitrarily decide to care for everything above a certain level of complexity, and decide not to care about anything below. "Vertebrates and octopuses" does not seem like a group that share any exclusive traits, i.e. any moral reason I have to care about an octopus seems like it would lead me to care about an insect, just maybe to a lesser extent.
Even if you value insect lives extremely lowly - if there's any moral value to them at all, mass farming them in the trillions or, possibly someday, quadrillions would be a moral travesty, even of their moral value is extremely small per individual, right?
I feel like "there seems to be a reasonable possibility that insects suffer" implies that we should have some level of interest in preventing their excess suffering, where practical.