Ants alone outnumber us by about one million to one. Until perhaps the last 200 years, an alien looking down on Earth at any time in the last 400 mil… - Dave Goulson

One theory as to why metamorphosis is such a successful strategy is that it enables the immature stages and the adults to each specialise in different tasks, and to have a body designed for the purpose.‡
‡Please note that I am not suggesting intelligent design by a supreme being. ‘Design’ is shorthand for the blind tinkering of evolution over millennia.

If one looks at the bigger picture, modern farming is part of a staggeringly inefficient, cruel and environmentally damaging food-supply system.

So, one can argue that insects are important, practically and economically, and one can argue that they bring us joy, inspiration and wonder, but both arguments are ultimately selfish, for both focus on what insects do for us. There is a final line of reasoning for looking after insects and the rest of the life on our planet, big and small, and it is one that is not focused on human well-being. One can argue that all of the organisms on Earth have as much right to be here as we do. If you are of a religious bent do you really think that God created all of this amazing life just so we could recklessly destroy it? Do you think He or She intended for coral reefs to be bleached and dead, littered with plastic trash? Does it seem plausible that He or She went to the trouble of creating five million species of insect so that we could drive many of them extinct without ever even registering their existence?
If on the other hand you are not a believer, and accept the scientific evidence that species evolved over billions of years rather than being created by a supernatural being with a beetle obsession, then you must realize that we are just a particularly intelligent and destructive species of monkey, nothing more than one of the perhaps ten million species of animal and plant on Earth. In that view, nobody granted us dominion over the beasts; we have no God-given moral right to pillage, destroy and exterminate.
Religious or not, most humans agree that the rich and powerful should not be allowed to oppress or dispossess the poor and powerless (though of course we do allow it to happen all the time). Similarly, in dozens of sci-fi movies from The War of the Worlds onwards, aliens more intelligent than ourselves arrive, decide that the human race is redundant, and set about wiping us out so they can plunder the Earth for their own ends, or build an interstellar bypass. Of course, in these films we see the aliens as the bad guys, and we root for the inferior humans who usually somehow triumph in the end despite the odds being stacked against them.
When will we realise the hypocrisy of our position? On our own planet we are the bad guys, thoughtlessly annihilating life of all kinds for our own convenience. We intuitively grasp that the aliens of the movie Independence Day have no right to take our planet; I wonder what goes through the mind of an orang-utan as it sees its forest home bulldozed to the ground? There should not have to be a ‘point of slugs’ for us to allow them their existence. Do we not have a moral duty to look after our fellow travellers on planet Earth, beautiful or ugly, providing vital ecosystem services or utterly inconsequential, be they penguins, pandas, or silverfish?