A Lantana provides a food source for the Postman and Zebra butterflies. A Vinca from South Africa provides nectar for many larger swallowtail butterflies. The centre of each Vinca flower is highlighted which aids butterflies in locating the nectar. This advertising is often more pronounced under ultra-violet light as many insects can see in these wavelengths. Other small plants provide some butterflies that are not specific about which flowers they visit with food.
Many butterflies are unable to survive on nectar alone.
They require essential salts. A special method of feeding is adapted by the New World tropical genus, Heliconius. The liquid now enriched with amino acids, is then sucked back into the gut. The protein-building material acquired in this manner sustains the butterfly in a much longer life than is usual and is also put into egg production. Exuded fluid contains no digestive enzymes but it is known that some pollen moistened with sugar solution releases protein and amino acids.