prosternal,a.Entom.|prəʊˈstɜːnəl| [f. prosternum + -al1.] Of or pertaining to the prosternum of an insect. 1868Rep.U.S. Commissioner Agric. (1869) 93 They [Elateridæ] extend the prothorax so as to bring the prosternal spine..to the anterior part of the mesosternal cavity.