By Rohith Srinivasan | Illustrations by Rubina Rajan
As we enter the deodar forests of the Himalayas, the first creatures to welcome us to these magnificent hills are the cicadas. Each deodar tree has cicadas thriving on them, producing clicking and buzzing noises. But while we may have heard their song, how many of us know about the life cycle of a cicada?
A cicada’s life begins underground. Beneath the deodar trees, nymphs undergo five stages of moulting and survive by feeding and sucking on the sap of the roots and the xylem of the tree. A large part of the cicada’s life cycle is spent in the nymph stage below ground. Their life cycles can be annual or periodical. Some species live across a span of a year whereas other species live for a longer period of two to 17 years, depending on species. All species of cicadas in India have an annual life cycle except Chremistica ribhoi from the hills of Meghalaya, which follow a periodical cycle. This species is known as the “World Cup insect” because it bizarrely emerges every four year once, surprisingly just a few weeks before the FIFA World cup. They are locally in Meghalaya known as known as “Niangtaser,” and they are immortalised in legends and are a delicacy for the local Meghalaya tribes.
A brood of cicadas emerges from the ground when the temperatures and the conditions above ground are ideal to metamorphose into an adult. They crawl up the nearest tree, shed their final layer of skin, harden and move up into trees to camouflage with the bark and branches, where they begin to sing their mating song. They have a very short life above ground, living only for a few weeks. Their main goal is to find mates and reproduce. Cicadas are very important to the ecosystem as they prune mature tree, aerate the soil, provide ample food for many organisms and, once they die, their bodies serve as an important nitrogen source for growing trees.
As soon as the forests echo with the racket chorus of male cicadas singing, the atmosphere within the forest changes. A plethora of organisms have been waiting for this moment! The singing cicadas herald a buffet for a variety of organisms in and around the deodar forests. Yellow-billed Blue Magpies, Spotted Forktails and Gray Treepies congregate to feed in and around the canopies of the coniferous trees, praying mantis and wasps scavenge on the barks of trees and bats feast on flying cicadas during the night. The cicada’s dingy colour provides camouflage against the bark and branches of the tree, so a hungry hunter must listen for its song in order track this cryptic insect.
They breathe life into the forest with their ceaseless singing.
Cicadas have a special membrane in both sides of the abdomen called a tymbal that produces their unique vocalisation. The tymbal contains a sequence of membranes that buckle one after the other when the cicadas flex their muscles. Every time a membrane buckles, it produces a click. Many clicks in rapid succession produce a buzzing sound. They vibrate their membranes 300-400 times per second! Cicadas have an air sac that amplifies the sound they produce. This sac, along with the competitive cacophony of all the male cicadas, produces the ear shattering volume that we recognize. The sound produced can go up to 120 decibels and each species has its own unique song. Cicadas prefer sunlight and warmth, as too much heat or cold will reduce the volume of their song. Their singing is a team effort, be it to warn away predators or to attract mates, and it is certainly worth it! Crickets are another major orchestral member of the background music of the forest. They rub their wings together in order to produce chirping sounds. Cicadas and crickets together create the wild and wonderful sounds of the forest.
The song of the cicadas resembles the rushing sound of the wild Beas River or the pit-a-pat of the torrenting monsoon rains in the Western Ghats. Due to their life cycle, cicadas need trees to survive. As soon the tree line ends at about 10,500 ft at Mali Pass in the Himalayas, one is surrounded by dead silence.
And once we turn and trek downhill again, the cicada’s song heralds our return.
About the Author:
Rohith Srinivasan is an undergraduate student studying Life Sciences at Ahmedabad University, Gujarat. He has always been passionate about exploring the natural world and has spent nearly 10 years with nature, mainly documenting birds, butterflies, reptiles, moths and, most recently, intertidal fauna. He has participated in wildlife conservation surveys across India and aims to enter the field of wildlife research in the years to come.
About the Artist:
Rubina Rajan is currently pursuing her master’s in Wildlife Science from Amity Institute of Forestry and Wildlife. The magic of nature is an unceasing inspiration for her creativity.