Popular Article Journal Home: www.bioticainternational.com Article: RT0121 How to cite this article? Biotica Karthik and Kukanur, 2020. . Research Research [Today 2(5) Spl.: 316-317. [ Today 316 Abstract Vol 2:5 nsects have developed many structural modifications to ensure 317 their survival during the course of evolution. A recently discovered 2020 Spl. Iadaptation was the presence of gears in insect legs of coleoptratus which they use for jumping and faster movements. In this paper, we have briefly described the modifications of hind legs Insect Gears in Issus and mechanism behind the working of insect gears. G. Sai Karthik1* and Vinod S. Kukanur2 Introduction 1*Dept of Entomology, Prof. Jayashankar Telangana State nsects are the most diversified organisms on the earth due to their capacity of flight and presence of three pairs of Agricultural University, Hyderabad, Telangana (500 030), India legs that helps in their better locomotion. Insect legs have 2International Crops Research Institute for Semi-Arid Tropics, I several structural modifications like large femur, strong tibia, Hyderabad, Telangana (502 324), India heavy musculature etc. that enable their faster movements to serve their various purposes. show a wide range of modifications in legs that suits their lifestyle. One of such modification which was recently discovered is briefed here. A or cogwheel is a rotating machine part having cut teeth, or cogs, which mesh with another toothed part to transmit torque, change the speed, creating a mechanical advantage. We humans think that we are pretty smart by inventing some dizzy array of machines and mechanisms that utilizes the so called ‘gears’ in their functioning, but Open Access evolution has once again outraged us, this time a million years ago. Recently, it has been reported that the gear Corresponding Author mechanism has been operating in insects since long time G. Sai Karthik (Lewis, 2013). Malcolm Burrows and Gregory Sutton of the e-mail: [email protected] University of Cambridge (2013) reported that the nymphs of , a common species of plant hopper, have the first known case of an evolved working gear mechanism. Keywords Juveniles of the species have gears on trochanter portion of Legs, Gear, Issus, Trochanter their hind legs, locking them together. Insects’ hind legs can be arranged in two ways. The legs of grasshoppers and fleas move at the sides of their body, in separate planes whereas those of champion jumping insects and plant hoppers, move beneath their body along the same plane. Thus, plant hoppers’ legs need to be tightly coupled for their synchronization (Burrows, 2009). As the young bug Article History prepares to leap, it meshes the gear teeth of one leg with those Received in 10th May 2020 of the other. Each leg has a curved strip (400 micrometers Received in revised form 23rd May 2020 long) of 10 to 12 gear teeth that attach to the trochanter on Accepted in final form 24th May 2020 the insect’s legs. The dark coloration of the teeth, in contrast with the lighter color of the underlying cuticle, suggests that the teeth are heavily sclerotized (Burrows and Sutton, 2013). Each gear tooth has a rounded corner at the point it connects to the gear strip. If there were to be a slight timing difference E-mail: [email protected] between the legs, then the body would start to spin. The gears

© 2020 316 Karthik and Kukanur, 2020 add an extra level of synchronization beyond that which can References be achieved by the nervous system. They synchronize the movement of the hind legs to within about 30 microseconds Burrows, M., 2009. Energy storage and synchronization of of each other much faster than the nervous system. In 30 hind leg movements during jumping in plant hopper microseconds, a neuron can barely begin to fire. insects (, ), The Journal of Experimental The cogs are only found in immature plant hoppers, or Biology, 213, 469-478. nymphs, and are lost during the final moult. But, adults do Burrows, M., Sutton, G., 2013. Interacting gears better jump than youngsters. Adult plant hoppers use friction synchronize propulsive leg movements in a jumping between their legs to achieve the same effect as the gears. insect, Science 341, 1254–1256. Adults may ditch their gears partly because gear teeth can Lewis, T., 2013. Creature with Interlocking Gears on Legs break, questioning the insect’s survival. Younger ones undergo Discovered, livescience.com. 5-6 moults and hence any damage to the gears, by chance can be corrected by replacing with new ones. It was said that, “In Issus, the skeleton is used to solve a complex problem that the brain and nervous system cannot.” Conclusion

ear mechanism existed in insects long before the invention of machines by humans. This paper will be Guseful in understanding the basic mechanism behind functioning of insect gears.

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