Larva

I just realized I didn't have one of these, so I flew down to Tranquillen, and started riding around to the spawn points, but wasn't finding any.  I rode past the Dawnstar Spire, then swam across the lake.  I got to Goldenmist Village where I finally saw a spawn, and it turned out to be a level 5 rare.  Quickly captured it, and killed the Snake that was with it.  This one is my 350th unique pet :)

After farming Spirit Crabs for an hour I finally said screw it and was going to move on into Eversong Woods for my next pet. On my way I stopped and fought a Small Frog at Suncrown VIllage and BOOM, Rare Larva. Im not saying it was worth it but I smiled

Off a Rat in Deatholme...1st try

Found a rare level 5 as a second on a small frog on the N.E. end of Lake Elendar. There seemed to be more larva  around the lake than anywhere else in the zone, but it took several hours over several days to come up with a rare.

Thanks for the tip for trying the secondaries on the spirit crabs. I had a gray quality but was looking to upgrade at least to uncommon. Spent about 2 hours pet battling all lvl 5 -6 spirit crabs last nite. Log in today.. 3rd spirit crab had a rare larva! (woot ty ty)

Definitely go for the secondary pet method - 5 spirit crabs (including a rare) and voila...

I got very lucky, about 20 battles and I got a rare lvl 6 as a secondary to a rat in Deatholme on the trail leading up Thalassian Range.

*went to look for spirit crab* (forgot to swap to my turnip) lvl 21s all round and had a larva (r) as the backup pet... couldn't lower its health without killing it... *crys*

Since I was spending A LOT of time in the Ghostlands looking for a rare Larva, I started to battle everything I ran across and level up my lower level pets.  I found the Larva as a secondary to a small frog.  It suprised me, but now I read that other people found it with the spirit crabs, so don't give up hope finding that rare - just battle everything.  :)

Found this little guy after about 6 spirit crabs as a secoundary 

I found mine just east of Sanctum of the Sun, between it and the road. It was paired with a bat (I think). It was an uncommon and I'm happy with that considering how hard these things are to find!

4 Hours of farming for a rare. Found mine as a secondary to a crab. Not fun.

I just got my rare by using the spirit crab method.

Took me a couple of hours, but I just ran up and down the coast engaging all the level 5 or 6 crabs, and just killing the others to despawn them and hope for a higher level.

This is far faster than searching the whole zone.

I did that for a few hours and only saw two larvae the entire time.

Caught one second to a Maggot in Deatholme

Can someone please give me absolute conclusive proof that the beige skin for this battle pet does exist in capturable form? Or am I just being spectacularly unlucky with the spawns?

Sadly when I went all the lvl5+ critters were dead or unco-operative; luckily, I found a solitary poor lvl4 Larva spawned near the ramp for Zul'Aman - good enough for now!

After taming my Rare Spirit Crab i spent 2 hours farming this little one. Tried the various spawn points and the secondary pet method and didnt see a single one. Finaly i fought a lvl 6 Rat and the Larva came up as an add, and lucky me it was a Rare!

Couldn't find any larva at all, then found out about the secondary pet method.  First secondary pet larva was rare and caught it.  Then used spirit crabs for an uncommon, but while I found a larva here and there, didn't find a green one (though it did appear that someone had gotten nearly all the +lvl 5's before me).

I then moved inland, hunting down all the +lvl 5's I came across and soon I got an uncommon larva secondary over in Deatholme.

Finally found mine by the Sanctum of the Moon on the west side common quality

After trying spirit crabs for a bit, I went to the east side of the map headed up to Dawnstar Spire, the snakes (level 5 and up) have these as secondary. My first was grey, second was green. Good enough for the achievement, good enough for me!