Many butterflies adore the sweet taste of sap dripping from trees. This sap is actually the fluid transported in the cells within in the tree. The cause of the leaking of sap from trees is believed to be due to the carbon dioxide that can build up inside the tree, forcing the sap through cracks or openings called "wounds".The common species of butterflies that we might see in this context, are the Common Baron, Large Oakblue, Baronet, Gaudy Baron and nymphalids that belong to the sub-family Charaxinae. They feast on the leaking sap. The sap contains carbohydrates (Phloem content) and a lot of minerals, sugar, hormones meant as raw materials for different parts of the tree (Xylem content).
I have noticed that trees ooze a lot more sap on warm days than on the cold days. This is probably because of the pressure built up within the sapwood (alburnum) is much higher when the temperature is greater.
It is interesting to observe that these butterflies which feed on tree sap, also feed on rotten fruits and animal dung. These species are rarely found on flowers. They are rarely seen nectaring. Mudpuddling (See butterflies-mudpuddling-and-courtship) is a common phenomenon though. This might mean that their necessities are slightly different from the butterflies which feed on nectar, or that they have adapted themselves to other sources of nutrition.The sap which oozes from wounds of the bark is called exudate. When dried, this exudate becomes crystallized and is referred to as manna.
A few glimpses of sap-feeding butterflies that I photographed this month.
Common Baron (Euthalia aconthea) at J.P Nagar forest, Bangalore:
Common Baron (Euthalia aconthea) at Girinagar, Bangalore:
Common Baron (Euthalia aconthea) and Large Oakblue (Arhopala amantes) at J.P Nagar Forest, Bangalore. On Eucalyptus tree.
Baronet (Euthalia nais), courtship, at J.P Nagar Forest, Bangalore:
Baronet (Euthalia nais) at J.P Nagar Forest, Bangalore:
Large Oakblue (Arhopala amantes) feeding on tree sap at J.P Nagar Forest, Bangalore: