ootheca /əʊəˈθiːkə/ noun2 •An egg case of any of the orthopteroid insects (such as cockroaches and mantids).Since the founding of the colony it had been a tradition to unload oothecae – egg sacs – in the cabinets so the younglings would be near the principal food stocks. — 1994 •The theca or sporangium of ferns. formsoothecae · oöthecae