Dung Beetles and The Milky Way By: Henry Klepser IV

Introduction After dung beetles find a suitable pile of excrement they roll it into a ball, do a “dance” atop it, and then roll the ball away from the original pile of dung. They do not have a destination in mind; they just want to get away as fast as possible. Some species do this during the day, but others perform this task at night. Scientists studied beetles in Africa to find out how they are able to navigate in the dark of night, and the answer they found was astonishing. Other nocturnal insects may use their sense of olfaction as a guide, but dung beetles use their sense of sight. Normally they use the light provided by the moon to move about, but when the moon is absent they use the Milky Way.

http://blogs. scientificamerican http://blogs.scientificamerican.com/observations/2012/10/22/booted-dung-beetles-reveal-clever-cooling-video/

Brief Review of Compound Eyes Responsible for photoreception (sight) in many insects Constructed from many ommatidia Can be either apposition eyes or superposition eyes Difficult to form a truly focused image of their environment, but are able to track objects at high speeds Compound eyes enable insects to detect light polarization and allow for the differentiation in color and ultraviolet wavelengths

Ommatidium Components A – cornea B – crystalline cone C & D – pigment cells E – rhabdom F – photoreceptor cells G – membrana fenestrata H – optic nerve http://en.wikipedia.org/wiki/Ommatidium

http://en.wikipedia.org/wiki/Arthropod_eye

So how does this happen? Because dung beetles eyes are so small, they do not have the needed sensitivity or resolution to see individual stars; instead, they use large clusters of stars, as well as the moon when it is present, to navigate at night. After dung beetles roll their ball of dung, they climb atop of it and “dance.” This dance is actually an attempt for the beetle to mark its position and then find a course so that it can set out Dung beetles use the gradient of light to dark generated by the Milky Way in order to ensure that they move away from the original pile of excrement and remain in a “straight” line. This is possible because of their superposition compound eyes which allow them to see when there is a very little amount of light present. What’s more, nocturnal dung beetles have highly developed light-sensitive cells in their retinas that are able to detect more photons than the retinas when compared to diurnal dung beetles.

Why this matters A dung beetle is an incredibly efficient at waste removal Improve soil structure and helps to recycle nutrients According to the American Institute for Biological Sciences, dung beetles save the U.S. $380 million dollars annually by burying livestock feces Without them their would be more pests and parasites that irritate or feed on livestock Because dung beetles are able to navigate at night, competition for resources amongst each other is reduced and the frequency of waste removal increases

Citations “Dung Beetles Use the Milky Way for Orientation,” Marie Dacke1, 2, Emily Baird1, Marcus Byrne2, Clarke H. Scholtz3, Eric J. Warrant1 ( 1 Department of Biology, Lund University, 223 62 Lund, Sweden) ( 2 School of Animal, Plant and Environmental Sciences, University of the Witwatersrand, Wits 2050, South Africa) ( 3 Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa) http://news.biharprabha.com/2014/04/some-less-known-fascinating-facts-about-dung-beetle/ http://www.theguardian.com/science/2013/jan/25/dung-beetles-navigate-stars http://scienceintheclouds.blogspot.com/2013/01/dung-beetles-follow-milky-way_28.html http://www.sciencedaily.com/releases/2013/01/130124123203.htm http://voices.nationalgeographic.com/2013/01/24/dung-beetles-navigate-via-the-milky-way-an-animal-kingdom-first/ http://www.todayifoundout.com/index.php/2014/05/dung-beetles-use-stars-navigate-2/ Losey, J. E.; Vaughan, M. (2006). "The Economic Value of Ecological Services Provided by Insects"