Copying from the web:
"The researcher Armando Zarate observes, "Theocritus of Syracuse
(308-240
B.C.), under the protection of Ptolemy Philadelpho and creator
of bucolic poetry,
is considered the first to devote himself to writing
this kind of poems." He adds:
" Perhaps even
more ambitious of intentions than Theocritus was
Simias of Rhodes. Contemporary of Callimachus and Euclid..."