We’re about to start the second year of our Dragonfly Detectives project, so it is a great time to think about what we’ve learned so far. Over the past year, over 100 kids in grades 4-8 have participated in the 6-week Dragonfly Detectives program. The first meeting is our primary training time as the kids learn how to identify the focal dragonfly species and read the equipment they will use in the field. The last week, the kids analyze their results and create a poster to share their findings. In the 2nd-5th weeks, the kids travel from their schools to a nearby NC State Park or Museum facility. There, they study dragonflies in the field and collect data that will help us answer an important question: how weather impacts the flight activity of the Common Whitetail Dragonfly.
At first glance, this might not seem like something anyone should care about, but this is an important question. It has been well established in the scientific literature that dragonflies are strongly impacted by the weather around them. This isn’t surprising when you remember that dragonflies are insects and are therefore exothermic (aka, they do not generate their own body heat). They are also large and have big, flat wings. Those big wings can get caught in gusty conditions and blow a dragonfly off course or raindrops hitting the wings might cause it to fall out of the air and become injured. However, we don’t know the intricacies of how weather impacts more than a few species. If a person is, say, studying the feeding behaviors of a particular species, but that species has a hard time flying if the wind speed surpasses 4 mph, then any scientific analyses that include observations from days with a wind speed of greater than 4 mph might not be accurate or tell a complete story. Because weather has a huge impact on flight activity in many species of dragonflies and damselflies, the relationship between weather and how much they fly is well worth studying in detail.
And that’s exactly what our Dragonfly Detectives are doing with the Common Whitetail! Our participants are using a weather measurement device called a Kestrel to measure the air temperature, wind speed, wind direction, humidity, and barometric pressure. They use a light meter to measure the light intensity and they make direct observations to determine if it’s raining or not. They also count the total number of Common Whitetails that fly past an imaginary straight line that extends from their position on the shore as far as they can see across the pond. Every time a Whitetail passes the line, they put a tick mark on their data sheet. Each group of Dragonfly Detectives collects data for the project 12-24 times during their 4 visits to the field. Then on the last day, they graph their findings, compare what they observed to what they hypothesized they would see on the first day, and think about the implications of their results. We take it one step further at the end of the year when we combine all the data from every group at every site and use statistics to look for patterns in the data.
By and large, the students in year 1 used their graphs to determine that wind speed, temperature, light intensity, and relative humidity mattered most to the dragonflies. Their data suggested that the barometric pressure, wind direction, and presence or absence of rain did not have much of an impact on the flight activity they observed. They also considered the pattern of their data and concluded that…
- The number of Common Whitetail flights increased with increasing temperature
- The number of flights increased with increasing light intensity
- The number of flights increased with increasing wind speed, and
- The number of flights decreased with increasing humidity.
Now one important thing to keep in mind is that each group only visited the field 4 times. Not all groups observed rain or high winds during their observations. Some groups also saw very few dragonflies overall due to the time of year they participated in the project. These are important considerations as we compare the analyses of our Dragonfly Detectives based on their graphs to those made by scientists using statistical methods.
At the end of the season, we looked for relationships between the counts with each of our measured weather parameters. Like the Dragonfly Detectives, we learned that temperature, humidity, and light intensity were the weather factors that showed the strongest relationships with flight activity. However, we found that the relationship was weak for wind speed, wind direction, barometric pressure, presence and absence of rain. We still have at least two more years of data collection planned for this project, but our preliminary results suggest that…
- Common Whitetail flights increase with increasing temperature
- Flights increase with increasing light intensity, and
- Flights decrease with increasing humidity.
Our findings differ from those of our Dragonfly Detectives in that the statistics do not support a strong relationship between wind speed and flight activity. Additionally, the statistics show a slight decrease in the number of flights with an increase in wind speed, a pattern that has been observed in several dragonfly species in the past. The fact that our results say something a little different than what our Dragonfly Detectives discovered doesn’t mean that our kids are wrong or that we are wrong. If you look at the graphs the Dragonfly Detectives made, you can see that it is visually unclear how wind speed actually impacts flight activity in Common Whitetails. Our kids are also working with small data sets. We, in contrast, are working with much bigger data sets and our tools are better at examining visually ambiguous relationships in much finer detail.
As we begin year 2 of the project, it will be interesting to see if the relationship between wind speed and flight activity becomes stronger. When you have more data points, you can sometimes see subtler patterns in the data than you can with a smaller data set. I suspect we will see only minor changes in how temperature, light intensity, and humidity impact flight activity and that we will continue to see that barometric pressure and wind direction won’t matter much. Very few groups got to observe dragonflies in the rain, so we could potentially see a shift in that relationship as well as the overall dataset grows. Only time and more data will tell, so we’re excited to collect more data with the help of our fabulous Dragonfly Detectives this year!