The Collaborative International Dictionary
Spermathecae
Spermatheca \Sper`ma*the"ca\, n.; pl. Spermathec[ae]. [NL., from Gr. ???? seed + ???? case, or receptacle.] (Zo["o]l.) A small sac connected with the female reproductive organs of insects and many other invertebrates, serving to receive and retain the spermatozoa.
Wiktionary
spermathecae
n. (en-irregular plural of: spermatheca)