A trophic egg, in most species that produce them, usually is an unfertilised egg because its function is not reproduction but nutrition; in essence it serves as food for offspring hatched from viable eggs. The production of trophic eggs has been observed in a highly diverse range of species, including fish, amphibians, spiders and insects. The function is not limited to any particular level of parental care, but occurs in sub-social species of insects, such as the spider "A. ferox", as well as a few other species like the frogs "Leptodactylus fallax" and "Oophaga", and the catfish "Bagrus meridionalis".