Insect Life Cycle : Periodical Cicada

[Music] of all the Earth's living things no group is as durable or as diverse as the insects insects have been on Earth for millions of years since before the age of dinosaurs their success is due largely to their incredible diversity each different color size and form is a tool one that takes advantage of an opportunity for survival in some species the greatest tool for survival is the life cycle itself in certain years the forests of eastern North America are filled with evidence of one of the insect world's most spectacular life cycles empty insect skins litter the forest floor the air is filled with a shrill Eerie song the periodical cicada is emerging the life cycle of the periodical cicada is the longest known in the insect world life began for these cicas 17 years ago when their eggs were deposited inside the living branches of the forest a few weeks later tiny cicada nymphs hatched and tumbled to the forest floor in a tiny mud cell beneath the ground the nymph Drew nourishment from a tree root it will continue to grow and develop for 12 years until it reaches its full size late in the 16th year the nymph begins to tunnel to the surface now in the summer of the 17th year an unknown signal starts millions of cic nymphs crawling to the surface this signal invariably comes at night and the nymph's strongest instinct is to continue climbing vertically away from the forest floor finally the nymph stops a split opens at the back and the adult emerges this process called eclosion usually takes about 90 minutes here it's speeded up by the time-lapse camera the heart pumps blood through veins in the folded wings at the same time the cicada's soft white body begins to harden by morning the transformation is completed the cicada's body is dark and hard and its wings are fully developed the adult cicada about 4 cm long is easily recognized by its large red eyes and delicate orange double Wings it feeds by inserting its beak through thin bark on the branch of a tree and drawing off the sap there are large Regional populations or Broods where all the cicadas emerge together there are at least 18 Broods in North America many of which overlap in most Broods the emergence occurs every 17 years though a few Broods in the South are on 13-year Cycles all the Broods do not emerge in the same year the cicadas in brood 10 for example emerged in 1970 and will emerge again in 1987 and in 2014 brood 13 emerged emerged in 1973 and will emerge again in 1990 and 2007 in a healthy brood the number of cicas is awesome hundreds of Millions May appear over the usual 2E emergence period vast numbers are essential to the survival of the periodical cicada because many will not live to the completion of their life cycle some emerging adults become trapped without the strength to complete their transformation others have shriveled mhap and wings large numbers die from a fungus infection that fills up the normally Hollow abdomen even healthy cicas perish in large numbers for many animals the emergence of cicas means a new and bountiful supply of food but because the cicas appear all at once the great majority survive a few days after emergence mating begins under the wing the male cicada has a white rided membrane stretched tight like a drum head this is the sound organ the males congregate and chorus in unison this chorusing is the cicada's mating call the female's eggs are fertilized during mating which may take more than an hour then with the ovap posit or egg laying tube the female carves out a cavity in a small Branch here she deposits her eggs about 15 eggs are laid in two rows side by side the female cicada will make one pocket after another until all 600 of her eggs are laid then with the most important part of their life cycle completed the adult cicas die off only a couple of weeks after they first emerged the longest known lifespan in the insect world comes to a quiet end during one man's lifetime a brood of periodical cicas will emerge only three or four times Henry divus of Chicago's Field Museum of Natural History watched brood 13 emerge 17 years ago at that time he made a census of the cicadas in this area now with co-workers from the University of Chicago he is back to study the same area with the same statistical techniques the area is divided into thousands of plots each of one square yard then about 100 are selected at random the field workers locate the plots clear the ground and count the cicada holes which will remain until the following winter this study has shown that as many as a million and a half cicas have emerged from a single acre of land one reason for the success of the periodical cicadas is the fact that they appear above ground all at once this synchronous emergence ensures that almost all the cicadas will be able to quickly find a mate birds and other Predators will eat only a small part of the cicada population before the rest have reproduced and died a natural death another important adaptation for survival is the cicada's extremely long life cycle the longest part of the 17 years is spent underground hidden from most Predators only 1third of 1% of the life cycle is spent above ground where the cic is most vulnerable there is no fully accepted explanation of how the cicada developed such a long life cycle but it gives the cicada a big advantage against its above ground Predators several months after emergence the forest shows evidence that a new brood will soon hatch where many pockets of eggs were laid the branches are damaged and the leaves at the end of the branches are dead this is a natural pruning process and does the trees no permanent harm but it's another indication of the great size of the cicada population seven or eight weeks after the eggs are fertilized tiny cicada nymphs begin to emerge from the egg pockets they tumble to the ground and seek shelter below the surface not all will survive in a few years they will be large enough to attract the attention of feeding moles fire and plant diseases will also take a toll when Dutch elm disease struck a few years ago in The Brood 13 area up to 2/3 of the nymphs in some locations starved but again numbers of the cicus defense if only 30 or4 of each female 600 eggs survive the population will continue undiminished the periodical cicada will emerge again in 17 years [Music] [Applause] [Music]