Here's the jist on this guy.
Another critter needed for the achievement added in 3.08 Pest Control (at the time of this post, it's not in database).
They're scattered all over Hellfire Peninsula, just fly around and spam your target macro, then keep an eye out. They're not very well hidden, you almost feel like a bird of prey swooping in to snatch him.

Helpful macro for the achievement:

• /tar https://vanillawowdb.com/?npc=3300 Adder
• /tar https://vanillawowdb.com/?npc=24270 Devouring Maggot
• /tar https://vanillawowdb.com/?npc=24174 Fjord Rat
• /tar https://vanillawowdb.com/?npc=16068 Larva
• /tar https://vanillawowdb.com/?npc=4953 Moccasin
• /tar https://vanillawowdb.com/?npc=4075 Rat
• /tar https://vanillawowdb.com/?npc=15476 Scorpion
• /tar https://vanillawowdb.com/?npc=14881 Spider
• /tar https://vanillawowdb.com/?npc=28202 Zul'Drak Rat
• /tar https://vanillawowdb.com/?npc=32261 Crystal Spider
• /tar https://vanillawowdb.com/?npc=9699 Fire Beetle
• /tar https://vanillawowdb.com/?npc=32258 Gold Beetle
• /tar https://vanillawowdb.com/?npc=16030 Maggot
• /tar https://vanillawowdb.com/?npc=6271 Mouse
• /tar https://vanillawowdb.com/?npc=4076 Roach
• /tar https://vanillawowdb.com/?npc=2914 Snake
• /tar https://vanillawowdb.com/?npc=32428 Underbelly Rat

Helpful macro for finding the Larva:
/tar Larva
/stopmacro [noexists]
/tell (YourCharacterName) > %t <

Remember to replace YourCharacterName with, well Your Character's Name.

Going to repost this on the others.

I kept searching some of these areas, and found nothing but the ""Addler"" snakes. I killed them and waited for respawn, and BAM! Scorpions showed up! So yes, if you find nothing but snakes, kill the snake, and sometimes a scorpion will respawn!

you can find them in Hellfire Peninsula also.

Confirmed scorpion sightings in Hellfire Peninsula. Found a scorpion in Hellfire Peninsula near 57,73 northeast of the Expedition Armory and just southeast of Valley of Bones.

These critters spawn in multiple colors. However, one color in specific, the yellow scorpion (shown in most of the screen shots), actually has a sound on click. It hisses, chitters, and makes rather adorable raspy little sounds. Interestingly enough, the other colors I've found (the black and such) don't make these squeaks. I'm assuming it's because the minipet scorpid is using the same skin exactly.

If you are working on the achievement ""Pest Control"" and are flying around Hellfire Peninsula looking for a scorpion, use the word ""scorpid"" in your /target macro. That is the exact name of the critter I found east of the Temple of Telhamat. It was the last one I needed for the achievement. (Targeting ""scorpion"" did not work.)