|I think they need to hire a new landscaper...|
This area in Pokémon FireRed and LeafGreen called "Pattern Bush" is located just a little north of Fortune Island. It's pretty strange looking when you walk through it during normal gameplay, and only bug type Pokémon can be found here. When seen from above, it's pretty obvious that this grass makes some sort of image, or dare I say, pattern. While the trainers there speculate that this area's strange look is some indication that treasure is hidden there, the developers at Game Freak had a completely different intention when designing this area.
As it turns out, the grass is supposed to look like a circuit board from the original Red, Blue, and Green cartridges. And as for only bug type Pokémon being found there, it's a reference to how buggy the original games are. At least the developers can acknowledge that the original games are less than perfect (I'm looking at you Genwunners)!
(Source 1, Source 2)