Monster Hunter World - Rainbow Bright Trophy / Achievement Guide - Capture a creature that glitters like a rainbow. [Silver]

For this trophy / achievement you must capture a "Prism Hercudrome" with the capture net. This is a small bug sitting on some trees in the game. It only spawns at dusk and dawn. You will notice the sun-icon in the top left corner starts blinking when the sun goes up or down. That's when this rare bug will spawn in specific locations. See the video for what it looks like & the location. It's available on low-rank & high-rank difficulty.
The capture net is automatically in your inventory from the beginning of the game. Equip it and shoot it at the animal to capture it alive. You can then use it as a pet in your room in Astera.