Bug Blog #8: The Dragonfly: Nature’s Pest Control
Welcome back to our eighth edition of Bug Blogs, celebrating Science Odyssey by showcasing benthic macroinvertebrates (bugs!) that we often find during our local stream studies program, Changing Currents.
Source: CAM Jr.-Sr. High School/BGSD
In this entry in our Bug Blog series we will be looking at the dragonfly. Dragonflies are easily distinguishable by their long thin bodies, long horizontally resting wings and large compound eyes on either side of its head. While dragonflies are a fairly well known species of insect, they spend very little time in their easy-to-recognize adult stage. Dragonflies will only spend a few weeks out of their four-year life span as a terrestrial insect. The rest of the time is spent below the surface of the water as a nymph. Dragonfly nymphs are the top predators in many aquatic ecosystems feeding on microscopic organisms when they are smaller and other invertebrates and even small fish and tadpoles as they grow. In their adult stage, dragonflies consume other insects including pests such as mosquitos.
Fun facts!
Nowadays, dragonflies can grow to be eight centimeters. However, in prehistoric times, the fossil record has shown that they could grow to be one meter long and have wing spans of up to two meters! One can only imagine how many less mosquitos would be around.
The Pantela Flavescens. Photo credit: Kate Hayes
Some species of dragonflies have also been known to migrate. Previously, the monarch butterfly was thought to be the record holder in terms of largest migration pattern. However, recently a species of dragonfly (Pantela Flavescens), also known as the Wandering Glider, has been found to migrate up to 18,000 kilometers, including a journey across the ocean, which is dicey for a dragonfly, considering they need freshwater to reproduce. That’s ten thousand kilometers further than the monarch butterfly!
What do they mean?
Needless to say, dragonflies are a fan favorite in the world of benthic macroinvertebrates, but what do they indicate about the environment they live in? Dragonflies have a tolerance value of 5 meaning they are slightly above average when it comes to living in polluted environment. However, being a top predator, their presence indicates a healthy food chain and good biodiversity.
If you’re feeling particularly slimy tomorrow, you won’t want to miss our snail-themed blog!
Bug Blog is EcoSpark’s blog series in celebration of Science Odyssey, a ten-day campaign celebrating Canadian achievements in Science, Technology, Engineering and Mathematics (STEM) with hundreds of science-based outreach events across Canada for all ages. Each day of Science Odyssey (May 12-21), we will be exploring a different Benthic Macroinvertebrate (BMI), small spineless organisms that live at the bottom of waterways. These are creatures we come across all the time in EcoSpark’s Changing Currents program, where we carry out stream studies with schools around the GTA by collecting BMIs to learn about local water quality.
EcoSpark's Bug Blogs would not be possible without the support from our generous sponsor, the Natural Sciences and Engineering Research Council of Canada (NSERC) PromoScience Program.
