Small children are attracted to bright colors, so look for ways to keep your pre-K classroom door colorful, bright and kid-friendly. Insects can appear scary to little kids, but brightly colored ones with happy faces aren't as likely to intimidate.
Insects are easy to sketch on construction paper and cut out. For example, you can lay three or four green ovals sideways and paste or staple them together to make a caterpillar. Add a face and draw some tiny legs. A ladybug requires a red oval with black dots and a head. Cutting the insect shapes from construction paper will save the expense of purchasing items from an educational supply store, although that is always an alternative.
To create a realistic looking scene with insects for your pre-K classroom door, you will need a habitat onto which you'll affix the bugs. A tree works well and is very easy to construct. Take advantage of brown paper grocery bags. Simply sketch your trunk and branches and cut from the brown paper. Add leaves cut from green construction paper if you'd like. Insects can climb on the branches and trunk or appear to be crawling on the ground underneath the tree. Add green fringed paper as grass.
As with most pre-K concepts, your insects on your classroom door decorations should be labeled. Tape plain white paper with the name of each insect printed clearly close to each insect depicted.
To assemble your pre-K classroom door decor, start by taping the tree and branches to the door. Follow with your leaves and grass, and then affix your various insects and their titles. This display should get quite a reaction when the preschoolers start walking through your classroom door.