In my childhood, I have been shown the plant, ' Touch-me-not' as a wonder, whenever our family visited Courtallam (the hilly and holly tourist centre, The Spa of Southern India). Now I am able to see that the tropical trees too exhibit such response to environmental stimuli! See here how this Mesquite (Prosopis juliflora) responds to the touch by rain drops:
In our boyhood days, between our studies we used to explore the environment in the school play ground. We were examining the branches of Mesquite trees (Prosopis juliflora): ants were crawling up and down busily. There were also some black insects sitting on the path of these ants. They had a queer appearance with horn - like extensions on their heads. In side view, they appeared like a bull (student community called it as 'Yerrumbu Maaddu' in Tamil, meaning ant's cow!). This insect is the Horned Treehopper (Centrotus cornutus, Thorn bug). It feeds on the sap of the plants. This sap on digestion is converted into sweet honeydew and excreted out. Ants are attracted towards this honeydew naturally and they extract it for themselves. In exchange ants provide the hopper the protection from its predators.
As I approach this treehopper to hold it between my fingers it runs around the branch and hides itself behind it or flies away. Even if I get it and hold, its thorn - like horns do not injure me, even nowadays! A wonder insect to remember about and show it to the younger generations!
