Praying mantids are a well-known insect predator. Their egg cases are frequently found in Christmas trees. In the fall, female mantids lay eggs in a frothy liquid which hardens into an egg case that sticks to the branch. Once warmed inside the home, the eggs may hatch and tiny mantids can invade your home. Again, these insects do not bite or carry disease. If the egg case can be located, remove it from the tree and put it outside. Small mantids that have escaped can be vacuumed up or caught and released outside.