To make the trap you just print the lid and fill the jar with sugar water and yeast.  The fermentation will generate CO2 which attracts the mosquitos they fly in the cone and get trapped. Turns out it attracts other pests like bald faced hornets and wasps as well.  (The fermentation must dissuade the bees as it didn't catch any of my honey bees or other pollinators.). The 20mm opening was the most effective in my backyard with the jars filled as shown, but I am providing all three lid types so you can experiment and see what works in your area.  If you find one size particularly useful, or a better attractant mix, please do comment so that we can work towards a consensus.  I used it in my backyard, but I can't wait to take it camping.  Enjoy.  

Liquid mixture (approximate):

1 ½ cups (400mL) water

½ cup (125mL) white sugar

1 tsp (5mL) yeast