Here in the genitive case, *laistrugo/nos. However, this is evidently quoted from Homer, Odyssey 10.106 and/or 199, where we see what this genitive really is: 'daughter of Antiphates the Laistrygon'. (Adler's note suggests, following Cohn, that -- as in ps.-Zonaras -- the present headword should actually be Laitrina, in Elis.)
cf. generally lambda 203 and the note there.