It is not uncommon for a dragonfly to be trapped in our home. Recently, a relatively large dragonfly flew into our living room and set the house in pandemonium! Moreover, we live on the tenth floor which reflects on how high the dragonfly can fly. It was trying to escape and it was interesting to observe its flight pattern while trying to shun it. It flew (with a slight buzzing sound) forwards and backwards suddenly and sometimes it just hung in midair. Ignoring the innate fear of large insects, it was actually quite fascinating! Interestingly enough, the method dragonflies employ for flight has been applied to various fields such as “robotics, aviation, and the military” (Beale, 2003). I found out that the method employed by these highly-skilled fliers is referred to as “active motion camouflage” which creates an illusion that they are not moving when they actually are (Beale, 2003).
The presence of dragonflies in an urban area is analogous to the presence of lichens in forests. While the latter is very sensitive to air pollution and thus can be used as an indicator for air pollution levels (Nash et. Al), dragonflies are indicators of water pollution. Their presence indicates relatively unpolluted water bodies and they play a key role in the freshwater ecosystem (“NParks”). Dragonflies generally eat small insects, including mosquitoes! And frogs in the pond ecosystem feed in these dragonflies (see Aside and Youtube video Dragonfly and Frog!)
It came as a surprise to discover that the dragonfly population in Singapore is indeed flourishing and increasing! According to a study done by NParks over a two-year period (2008-2010), the total number of dragonfly species have reached over 120 (as compared to 117 in 2008 (Norma et. Al, 2008)) ! This is nearly as large as the number of species in the whole of Europe, which only has 130 species (Wasscher, 2003)!!
So the next time you see the humble dragonfly, remember it reflects on how the freshwater pond community is thriving!
Aside: Above are some pictures of the lagoon area in my condominium(I meant to put them below but i can’t seem to format it right). It used to be teeming with dragonflies and frogs everyday at around 1800. It was a freshwater ecosystem right at our doorstep, literally! Unfortunately, due to the high cost of maintaining the freshwater fish pond (also because many children including myself took the liberty to go pond fishing ;)), the fishes were removed and the water chlorinated about a year ago. Consequently, the dragonflies and frogs disappeared!
References
Beale, Bob. “Putting the Buzz in Navigation.” Scientist 17.19 (2003): 28. Web. 14 Apr 2010. <http://www.the-scientist.com.libproxy1.nus.edu.sg/article/display/14150/>.
Norma-Rashid, Y., L.F.Cheong, H.K.Lua & D.H. Murphy, 2008. The Dragonflies (Odonata) of Singapore: Current Status Records and Collections of the Raffles Museum of Biodiversity Research. Raffles Museum of Biodiversity Research, Singapore. 21 pp. Uploaded 7 Nov. 2008. <http://rmbr.nus.edu.sg/raffles_museum_pub/Dragonfly_of_Singapore.pdf>
Nash, Thomas, and Unione italiana. Lichen Biology. 3rd ed. United Kingdom: Cambridge Univ Pr, 1996. 240-41. Print.
“NParks’ Dragonfly Project Unveils One Third of Total Species Existing in Singapore Sighted at Urban Parks and Gardens.” National Parks. Singapore Government, 30 03 2010. Web. 14 Apr 2010. <http://www.nparks.gov.sg/cms/index.php?option=com_news&task=view&id=188&Itemid=50>.
Wasscher, MT. “The European dragonflies: Notes on the checklist and on species diversity .” CSA Illumina 29.1 (2000): 31-43. Web. 14 Apr 2010. <http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=ENV&recid=4699809&q=dragonfly+number+europe&uid=1015501&setcookie=yes>.
