Aphid: Aphids are soft bodied insects that use theirmouthparts to suck sap from your plants. They can be green, brown, black or red. In Epiphyllum they are most often found on newly forming blooms. In small quantities aphids do not cause much harm, but if they are left untreated they can multiply quickly and cause blossom deformities or complete lose of your blooms.
Solution: Small infestations can be sprayed with a solution of 50% isopropyl alcohol and 50% water several times a week while insects are present. Large infestations can be controlled with an insecticidal soap spray or systemic insecticide (follow manufactures directions for application rates and times). Light Horticultural oil is also very affective against aphids but it is becoming very hard to find for the home gardener (CAUTION: Neem oil is too heavy for Epiphyllums and may cause damage to your plants)
Biological control of aphids can be obtained by releasing Ladybugs or lacewings at the bottom of your infested plants at dusk.