My daughter (age 6) LOVES bugs. Every year for Halloween (since she became old enough to make a choice) she chooses a different "bug" to dress up as. She has been a Death's Head Hawkmoth, a Snail, a Monarch Butterfly, an Isopod (Roly-Polly), and this year she wanted to be an Iridescent Stag Beetle.

I have no skills with sewing, and nobody makes Isopod or Stag Beetle costumes for little girls (imagine that!). So, when she was 4 and I needed to turn her into an isopod, I grabbed some cardboard, roughed out some shapes, covered everything with ducttape (silver/grey and waterproofing!) and hooked it all together with box rivets. It was a hit!

This year, we're going for an Iridescent Stag Beetle- so the process has been similar, but I've replaced the duct tape with some adhesive vinyl (like they make for cricut machines).

Supplies

Various Carboard boxes (whatever you have on hand)
Box rivets (I like makedo)
Tool for cutting cardboard (scissors if you have to)
Duct tape or Vinyl contact paper
Any fun accessories.

Step 1: The Elytra (Wing Covers)

Lay out the child onto your largest piece of cardboard and trace them (to make sure you can get big enough wings)
Draw and then cut out a nice big circle
Cut the circle in half
Overlap the two halves at a slight angle and join the two halves with a box rivet (this lets them open and close a bit)
Cut a smaller half circle shape for the top of the beetle's "shell"
Fold this a bit to shape it
Join this with two box rivets, one at each corner, to each elytra (wing)
Add some shoelaces or other string through each wing as arm loops.
Stick on the shell covering (when we made the isopod we used duct tape for this. This time, it is adhesive vinyl. For the wings I found some iridescent vinyl that shifts green/yellow/orange (orange being this girl's favorite color)
Covered the inside of the wings with a contrasting color too.
Test out on your kiddo.

Step 2: Make the Head

The head is the hardest part. Not the design of the head itself, but making it comfortable and making sure it will stay on and in position. I apparently didn't take process photos though. (Oops).

Use thin flexible cardboard (like cereal box) to make a "crown" shape around the kid's head. I usually also add a strip that goes up and over the top.
Then build the rest of the head is segments around it. This head is three cardboard strips, each held onto each other with box rivets at one pivot point.
The box rivets were pokey, and the head kept slipping back so we improvised some padding into the head with duct tape (orange, because it is HER duct tape.)
This is a stag beetle, so she needed awesome pincers. Traced one out, used it as a template to cut the other. Added some Popsicle sticks for extra support. Each pincer is two layers of cardboard.
The pincers are attached with box rivets, which she asked me to leave showing because she thinks they look like eyes.
Covered everything again in vinyl. This time in some shimmery brown.
Added some antenna that she had leftover from a previous year (in the isopod costumer we added fake eyeballs at this stage as well).

Step 3: Making the Abdomen

For the abdomen, child requested that she have two features: bumps like a real beetle and an extra pair of legs. Trickiest part for me was deciding how to attach the abdomen to her body in a way that would allow the whole costume to come on and off easily with minimal adult help.

Trace your kid again
Cut out two vest shapes
Cut one of the vest shapes into strips.
Layer the strips onto the full vest to create a bumpy look.
Stick everything together with box rivets.
Take a pair of child's tights. Stuff with cotton, or old socks- whatever you have on hand.
Attach the tights across the back of the middle section. These will be the legs. (You can attach these in several different ways- I used duct tape because we want to be able to reuse the tights, but rivets could work too)
This will attach to child with two pieces= (1) a loop up over shoulders and behind neck and (2) and cloth band across middle to tie behind back (it is tucked behind one of the cardboard strips.)
After everything is in place, coat all visible surfaces in your choice of covering (in this case, more brown shimmer vinyl)
Test for fit (and because she is six and we have been testing everything every ten seconds)

Step 4: Final Touches

Dress the kid in one color of top/bottom (we chose black), accessorize as needed. Fiddle with the details, but remember that a six year old who wants to be a Stag Beetle is probably just thrilled that you helped her become a stag beetle! (Or isopod, or lady beetle, or I hear next year I'm making her into a preying mantis...)

And also, she got to help cut the cardboard with the cool little cardboard saw.

Enjoy being shiny and Iridescent!