Check the listing for details. 1 REAL PRAYING MANTIS EGG CASE OOTHECA NATURAL PEST CONTROL. Condition: New. Listed at 12.99 USD. Praying Mantis are utilized by gardeners who are looking for a chemical-free pest control solution for their gardens and greenhouses. Mantis have enormous appetites; eating various aphids, leafhoppers, mosquitoes and other pest insects. On average each praying mantis egg case contains close to 200 mantis. Within a few hours of hatching, the young mantis that have emerged are ready to start devouring your garden pests. Beware! If there is a limited supply of food, they may eat each other! Egg hatching requires approximately 4-8 weeks of continuous warm weather to begin hatching. You can keep the egg case refrigerated until you are ready to use. For best results, temperatures should be above 60°F where the Mantis are released. It is possible that the egg won't hatch. Unfortunately, there are no guarantees in nature.