In the heydays of sci fi,so I hear, there was also the fear of communism. So that’s where you get the exagerrated fear of that: facelessness, non-individuality, mind-control.
Also H.P lovecraft (a pulp writer) wanted sci fi to be as far from humanity as possible, he was fed up of lazy pulkp writers sticking one or two broad human characteristics onto creatures from another world(note that cthulhu, dagon, etc, aren’t bothered by humans either way really, we’re either food, slaves, or something in the way). It’s like the colonial era mentality – we’re christian and ‘advanced’ so obviously we’re more important, more interesting. Europeans and americans were not the only humans on planet earth, and, in sci fi at least, humans aren’t the only beings in space, right? You have to be open-minded!

I prefer the idea that it’s psychological though, the deep recesses of the psyche. Notwithstanding the Protoss/Eldar,  interesting in pointing out humanity’s shortcomings as applied to themselves, don’t seem to me to deal with much more than that.
The ‘bugs’ are our fear of our origins in the greater universe, as it were. Invertebrates with a neuron for a brain – wriggling, crawling things. They remind us of our frailty – to disease and luck, and our selfhood’s frailty within the mass of human beings and the world of matter. When you die, which we all will, you rot. One of the cruellest lies seems to me God in the Bible (you know that book?) telling us we have a special place in His world. He has set us apart, above the other things of the world, made us stewards of nature. He loves us. And our selves will never be dismantled or disappear, they will live for eternity in his kingdom of good things.
Exactly the opposite is true! We are trapped alongside the lions and tigers (who had us at the bottom of the foodchain for thousands of years), the plants, moulds fungi and of course bugs. Everything physical will die or change, be usurped and usurped in turn. And everything non-physical will eventually be forgotten. it lives on in our hearts and our children’s hearts, but eventually we all will die, and it will be incredible luck, and only luck, if we survive for more than a micro blink of an eye in universal, cosmological, geological terms.

Nature is overabundance. Famine, and flourishing of life. It is split apples fluffing white and green, infected wounds, dead cells, dead beings, rotting, breaking down, to slime, fertile or poisonous ooze. Warm wriggling, down to cold – always heading down into the earth to sprout up again. The cycle is unstoppable, it does not know mercy. It sacrifices one aspect, is in another’s growth.
She’s a red-toothed whore who kills her creations