The female Christmas Island Red Crab has about 25,000,000 or so who migrate on shore together to then lay eggs in the Indian Ocean. The timing of the migration seems to be linked to phaese of the moon. They are apparently designed by their creator with software internally to know when and where to lay their eggs. Another part of the web-of-creation here on God's earth.
Bring forth with thee every living thing that is with thee, of all flesh,
both of fowl, and of cattle, and of every creeping thing that creepeth upon
the earth; that they may breed abundantly in the earth, and be fruitful, and
multiply upon the earth. Genesis 8:17
