I have 8/12 shells but only 1/12 butterflies!? Any ideas why?

You've either not spotted the butterflies when they spawned, or you've just had a plethora of shells. Don't worry, you should be able to get them all in time.

i have got 8 of every collectable lol

The collectibles are spawned randomly. Its not like you get i of each every so often. The rare ones don't come out often so you may have missed those and will have to hope you spot it next time.

I've only got 4 shells, 4 butterflies and 3 pebbles and the same ones just keep turning up over and over again (good for tech points though). So, do you have to reach a certain level of Exploration Tech to find more of each item? At the moment I am at Exploration Level 1.

yes.. as you get better exploration tech you'll see more of the uncommon and rare ones.. and more overall

I only need 1 more (uncommon) butterfly, 1 rare shell, 2 rare pebbles, and 4 or 5 beatles. I am unearthing the ruins now. I haven't seen a butterfly in days (I am still only level 2 exploration)... All that keeps poppin up are rocks and the occasional shell. Every blue moon I get a beetle - no butterflies. I am hoping that when I get level 3 exploration, they will all decide to show up!!!
K

I need 1 butterfly, 1 shell, 4 beetles, and 3 pebbles.

I need 2 butterflies and 4 beetles

I have all my butterflies, I need 1 uncommon shell, 1 uncommon beetle, all 4 rare beetles, and 1 uncommon pebble. And I love the tech points I get from extra rare items!!!!