Found this hard, foam-like brown structure attached to a fence post in the backyard. I was about to scrape it off but hesitated. What is it?.

5. Is It Safe? Why You Shouldn’t Scrape Off a Mantis Egg Case
While it might be tempting to remove an unfamiliar structure from your backyard, it’s essential to recognize the ecological role of a praying mantis egg case. These egg cases are harmless to humans and pets, and their presence indicates a healthy, balanced garden ecosystem.
Scraping off or destroying a mantis egg case not only disrupts the life cycle of this beneficial insect but also removes a natural form of pest control from your yard. Praying mantises are crucial for keeping pest populations in check, and allowing them to hatch and thrive benefits your garden’s health. It’s best to leave the egg case undisturbed unless you have a specific reason to relocate it.
6. What Happens Inside: Hundreds of Tiny Hunters Waiting to Hatch
Inside the protective shell of an ootheca, hundreds of mantis eggs develop over the winter months. The ootheca provides insulation and protection, ensuring that the embryos remain safe until conditions are ideal for hatching.
As temperatures warm in the spring, the young mantises begin to emerge from the egg case. They are tiny replicas of their adult counterparts, complete with distinctive forelegs and an innate predatory instinct. These miniature hunters disperse quickly, seeking out small insects to feed on as they grow and mature. The emergence of these mantises marks the beginning of their journey as beneficial predators in the garden.