I'm in the same boat! I caught one last summer, but this year I haven't seen one yet. I've seen only 2 tarantulas as well. I just need to take laps and walk in and out of buildings more, but man they are the worst to find.
Step 1: Find a tarantula
Step 2: Find a tarantula
Step 3: Find a tarantula
Step 4: Get stung by a scorpion
Step 5: A scorpion jumps in the river when you are close to catching it
Fortunately I have not been stung by either yet (CF and WW made me paranoid so I'm so careful), but it is bound to happen eventually.