Update from my last comment: 100% catch rate (for me) with this trick. Treat them as a scorpion and/or tarantula; approach slowly with your net in catch mode (crouching) and when they make a certain movement, stop. Move again when they become idle again (dunno how to describe) and then catch them.
Which time is the best to catch it? It legit won't spawn on my island :')
thanks for the comments guys, I was about to lose it. so annoying.
Tip for that motherfk: Just walk towards it until you're in range, WITHOUT your net equipped. When you're in range, get your net out, turn around carefully and catch that little sh** that I totally did not spend 10 hours of my life trying to catch ¯\_(ツ)_/¯
Sorry, it's not a town, it's an island. I know people will try to correct me on this, so might as well correct myself.