The Collaborative International Dictionary of English v.0.48:

Ootheca \O`o*the"ca\, n.; pl. Oothecae. [NL., fr. Gr. w,'o`n
   an egg + ? a case.] (Zool.)
   An egg case, especially those of many kinds of mollusks, and
   of some insects, as the cockroach. Cf. Ooecium.
   [1913 Webster] Ooticoid