Naldormi

They can be found in a cave with another whelp (Xiddorm) messing with the spiders inside by warping time around the arachnids. They'll occasionally argue, transcript of the dialouge below.

Xiddorm: Stop messing with them, they are MY spiders!
Naldormi: Mine are going to go SUPER FAST!
Xiddorm: Stooooooop it!
Naldormi: There are lots of spiders, we can share.
Xiddorm: Find your own spiders!

Cave entrance:
/way 61.07 73.29 cave entrance

There are multiple cave entrances, but this is the largest opening.

Edit: Ha! Now in patch 10.2, these two finally are involved in a questline. I mean they don't star in it, but they are the source of the problems you solve in Cavern Cleaning. I won't explain much to avoid spoilers but upon speaking to Naldormi:

Naldormi: Hello!
You: Why are there so many spiders in this cave?
Naldormi: No idea! Xiddorm and I didn't put them here, that's for sure. We definitely did not see if we could make this entire cave the biggest spider cave ever. And under no circumstances did it get out of hand. I simply have no idea!

Ah, the joys of what are essentially children with superpowers... It's honestly no wonder Azeroth hasn't blown up by now.