Bugs and Insects - STEAM Art Sub Lessons
Here is one on TPT that was written easy enough to be taught by anyone; art teacher, sub, classroom teacher, or random person off the street. Ugly Bug Ball
This one is also on TPT. It could also be taught by anyone. A multipurpose lesson, it could be used as a center activity, an early finishers activity, or an art sub lesson. Create Insect Designs with Radial Symmetry - STEM/STEAM
This is a coloring/doodle/patterned Monarch Butterfly activity on TPT.
The images in this blog post are great. As an upper elementart art sub lesson, you could do some step by steps of how to draw a simple insect and add a pattern chart. Kids could do some beautiful drawings with crayons or markers. This is over at Laura Kelly's blog, Me and My Inklings.
Here's another good one with lots of visuals and instructions. Still, for a sub, you might want to add a few more step by step visuals unless you have a person who is comfortable doing simple shape drawings. I would also keep the lesson to just crayons or markers. It is a nice lesson. Visit the Laugh Paint Create blog.
KinderArt, always a good place to check out lessons, has a lesson called Bug In A Jar. It was written for middle school art, but could be adapted, I'm sure.