Where do I find the beetles and the pebbles?

I have exploration 2.

What tech items do I need to have purchased to be able to get each of these.. as well?

Try taking a scientist up there, they will pick it up to make a
tool, then get them some wood from the twisty roots just below
the shiny thing. This is the tool that will allow your villagers to clear away the thorns.

Yes, just edited my post because I just found out about the tool.. but still don't know about the collectibles.

The shells pop up around the beach,
the butterflies can show up anywhere,
the pebbles will be down in the right
hand corner on the mosiac and
the bugs will show up after you clear the
thorns, but don't forget the exploration
tech

Forgot to mention, the collectibles are
random and even if you've already got it
pick them up again, you get 100 tech points
for each duplicate they take to the scientist

2 or 3 on exploration to get those darned beetles? I've got 2 so far.

I did know about the getting them again, even though you already have them.

I also found a semicheat that if you pause, grab 2-3 kids and put them on that item (must be uncommon or rare to work) the kids will all pick it up.. so there are 2-3 of that item, and you'll get the tech points for them along with the first of the item. Be quick, because pause doesn't pause the item, but the kids so you can grab them faster.

Some of the items, such as rare, I have seen bring in 1k in points for one.

You get much more than a hundred on some of them - and if they are rare especially 300+ tech points.
Beware of picking up more than one item at a time, if you pick up a second item before the 1st one has been taken into the science shed the 1st child will drop his/hers. (At least they do on my system)