As a cheeky boy running behind the Crimson Roses and the similar kind of butterflies to capture them to make-butterfly kites (I know I was horrible to them), I remember seeing some brown coloured butterflies sitting on “Lawulu” fruits (egg-fruit)?? that were fallen from our Lawulu tree (Pouteriacampechiana)in our garden. Those days, I did not pay any special attention to those Lawulu eating frugivorous butterflies. But later on, when I started to read more about butterflies, I have become interested in paying more attention to their different foraging behaviours, especially to their different foraging substrates.
Compared to fifteen years ago, today, my garden does not harbor diversified butterfly fauna; fewer species, and their numbers are less. I know the cause for it: clearing of all our native bushes and weed plants.
One morning, I was having my tea sitting in my comfortable chair on our back veranda, my mum drew my attention to a butterfly flitting on a fallen Jambu fruit. It was a Common Bushbrown, after observing it for a while from a distance I realized he was sipping the juice from the Jambu fruit. I was able to observe it for good 10 minutes before our dog disturbed it. After it left, I observed the jambu piece that it fed on, and I realized that it was not very flesh and could be a couple of days old.
On the same day, in the afternoon, I decided to wait closer to another Jambu tree where there were more fallen fruits on the ground. But I did not observe any butterfly there, instead, I saw two Evening Browns feeding on a rotten jack fruit piece at our home trash site where my mum puts litter from here kitchen such as unwanted vegetable pieces. I switched my study site from the Jambu tree to the trash site.
Within the next 10 minutes, two more Evening Browns were attracted to the site. They did not land on the fruit directly; instead, they landed on the ground closer to the fruit and walked to it. And they checked the fruit very carefully for the best places to feed on. These guys stayed on the same place for some time before moving to another place.Later they were joined by two Common Bushbrowns and Dark – Brand Bushbrowns. The individuals sat on the fruits, for varying lengths of time and flew away one by one as the darkness falls.
The next day, around 11 in the morning, my mum called me again and said ???there is another butterfly feeding on Jackfruits”. So I went there with my camera, this time it was a Common Baron feeding on a ripe jack fruit that we plucked the previous day. It had a small opening probably made by fruit bats; the juice was oozing out to the opening so easy spot for the Baron to feed on. It moved its long proboscis continuously to feed on, the reason for that could be, the particular spot it selected to feed on was contaminated with some milk-sap.?? After 10 minutes it left the jack fruit and flew towards our trash site and land on the rotting jack fruits and started to feed on it. The barons are known for relishing fallen rotting fruits
That evening I decided to conduct a small experiment to check their food preferences. I put some papaya peels, banana peels also some Namnam(Cynometracauliflora)fruits which I collected from our garden. Also, I put some lemon peels among them. The first species that attracted to the site was a Common Bushbrown, and it did not directly land on any fruit surface instead landed on the ground. After a couple of minutes, it landed on a papaya peel.
The second species attracted to the site was also a Common Bushbrown??which directly landed on another papaya peel. A few minutes later the Evening Browns arrived, and as usual, they landed on the ground. One walked to a papaya peel while the other walked towards the jack fruit and started feeding on it.
The fourth species that visited the site was a Dark – Brand Bushbrown, which landed on a papaya peel, and started feeding on it. Also a Nigger landed on a banana piece but did not stay long. All the individuals who landed on papaya, after feeding sometimes they switched to jack fruits and never fed on papaya again, showing that jack fruit was the most preferable food substrate.
Surprisingly, a ??Baron attracted to the site; it landed on Namnam and after feeding on it some minutes it changed its substrate to a papaya peel and did not feed on any other fruit. Other than the ??Baron, no other butterfly selected Namnum fruit that evening. No butterfly fed on lime peels.
Food preferences of Browns
All three satyrids (the browns) are not specialized fruigivores but according to my observations, they are more frugivorous than nectivorous. I have not seen a Nigger feeding on a flower. And the Barons are known for relishing fallen rotting and ripe fruits.
??I could definitely say jack fruit was the favorite fruit of all the species. High fondness for jackfruits by all three species could be due to the presence of high concentrated fermented products such as ethanol and acetic acid compared to other substrates.
Butterflies use both visual and olfactory cues to locate their food. It was clear to me that in this situation, butterflies used their olfactory senses to locate the trash site because rotten jackfruits have a strong order. But overripe and rotten fruits do not have aromatic odour like flowers and ripe fruits, therefore these frugivorous have evolved to smell the different volatile attractants released from the fermenting fruits such as jack fruit in this case. It has been found that some frugivorous have sensilla on the proboscis, labial, and legs in addition to sensilla on antena to perceive the magnitude of volatiles from rotting fruits. On the forest floor, rotting are fruits are most often covered with litter, so colour plays little role in locating food.
By landing on the papaya peel at first, it showed the butterflies were attracted to the reddish-orange colour of the papaya peel which was the most bright coloured food substrate in the trash. Butterflies are well visually adapted to distinguish between fine variations of color, so sometimes frugivorous also use their trichromatic vision to test their food like this occasion.
In order to feed on fruits, these butterflies needed behavioural ad morphological adaptations. The most important adaptation is in proboscis since up taking of fluids from fruits not as easy as feeding on nectar, they have to penetrate the thick skin of fruits and stringy fruit flesh. Some frugivores have brushy tips at the end of the proboscis to lapping up the fluids while others have strong and thick proboscis for piercing the skins of fruits.??????
Why do butterflies feed on fruits?
Since fruits are available year-round in the tropics, unlike in temperate climates, some butterflies have evolved to feed on rotting fruits. So why do these butterflies prefer fruit juice over nectar? It has been experimentally shown that Sodium and other microbial products such as Amino Acids are deficient in nectar, whereas fruits are richer in Sodium and Nitrogen. So the next question is, are these butterflies interested in both Sodium and Nitrogen equally or more interested in one over the other.?? A study conducted by Alison et al found that frugivorous have a stronger craving for amino acids than for sodium. As she mentioned this could be due to the fact that frugivorous butterflies have longer life spans compared to nectar-feeding butterflies and getting more nitrogen from fruits can help them to maintain body tissues.
This kind of dietary shift of butterflies is likely the result of evolutionary stratagem to reduce resource competition among them.????
