Wiggle will ask you to find two Sub Sandopedes for her, and you will need to do it to progress through the game. To find Sub Sandopedes, you will need to go back to the Flavor Falls area, the very first area in the game. It doesn’t matter if it is day or night time, the Sub Sandopede will be wandering around the area.
You can find the Sandopede walking a pretty large circuit around the area, but if you just stay in the area that you arrive in he will come to you eventually. There is also a Salad Dressing plant here, so harvest some of that as you will need it to get the Sub Sandopede.
You can’t catch the Sandopede in its large form, you actually need to break it up into smaller pieces to be able to catch it. Scan the Sandopede so you know the route that it takes, then place four or five globs of Salad Dressing down close together.
The Subs Sandopede is actually made up of multiple smaller Bugsnax, and they will all break up to try and get some salad dressing. When this happens, you can catch the smaller pieces in your net. Run in and hit Square to grab as many as you can. You can then head back to Wiggle and feed her the Sub Sandopedes. Keep in mind, it doesn’t matter which section you feed her. One is called Sandopede, and the other is called Sub Sandopede, feeding her two of them will move you onto the next quest.