Dragonfly Detectives


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Featured Dragonfly: The Common Green Darner

The Common Green Darner (scientific name Anax junius) is the largest and most brightly colored of the five species of dragonfly we are looking for as part of the Dragonfly Detectives project. The body of this dragonfly is approximately three inches long. The thorax, or middle section of the dragonfly, is bright green. The abdomen, or tail-end of the dragonfly, can differ in color depending on the sex. Males have a brilliant blue abdomen while the females have a greenish or purplish brown abdomen. Both sexes have a black stripe down the entire length of the abdomen. The wings of this darner are uncolored or slightly orange-tinted in immature dragonflies.

ANAXJU~3-2This dragonfly can be found in almost any stillwater habitat in the entire United States, but is most commonly found feeding on small insects over fields or patrolling (flying over water to defend territory) lakes, ponds, and ditches. Its range stretches north into Canada and south to Central America. If you are lucky you might see a “swarm” of dragonflies: dozens, even hundreds of dragonflies all in one place at one time! Swarming appears to be due to favorable feeding conditions or group migration. Once familiar with this species, you might start noticing these beautiful dragonflies when you travel outside of North Carolina too!

North Carolina has both resident and migrating populations of the Common Green Darner. The migrating dragonflies arrive in early spring from the south. This early set of dragonflies mate, lay eggs, and die during the summer. The succeeding generation of these darners can go from egg to adult while still in summer season. Soon the migrating dragonflies are ready to take flight and head south once again. They migrate much like a bird, taking advantage of tail winds, using some days to travel and other days to rest. Their average daily flight during migration is 7.5 miles, but darners have been documented to fly up to 100 miles in a day! The total length of this dragonfly’s migration is still being studied by scientists and by citizens like you! Resident dragonflies do not migrate, but can be found in this area throughout most of the late spring and into the early fall.

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Spring Session: That’s a Wrap!

On the last day of the 6 week Dragonfly Detectives program, students compiled all of the data they had collected to determine which weather factors had the greatest impact on dragonfly flight.  They worked hard and did a great job analyzing the information to make sense of it all, determining that most of their hypotheses were correct; dragonflies do indeed prefer sunny warm weather with light winds and no rain. Students wrote out hypotheses, methods, conclusions, created graphs and graphics bringing it all together in a scientific poster that will be displayed at BugFest at the NC Museum of Natural Sciences on September 17!  Spring participants were all homeschool students from Harnett, Johnston, Wake and Franklin counties.

 


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Spring 2016 Dragonfly Detectives at Prairie Ridge

 

PR homeschool Monday spring 2016

Students busy counting dragonflies

Dragonfly Detectives spring sessions at Prairie Ridge started a few weeks ago, and with our ‘early’ spring, we’ve had plenty of dragonflies to view!  Week 2 began with the students’ first day of data collection. The day was warm and sunny, with the students recording a high temperature of 90.4 degrees F on the Kestrel and a light intensity of 1222 Lux on the light meter.  There were many dragonflies out and about and the students did an excellent job of counting and recording flight numbers!

Week 3 was especially exciting as we attempted to catch dragonflies with our insect nets, mark them, and release.

Sarah in pond

Sarah, one of our awesome and adventurous volunteers, helping the students out by attempting to flush the dragonflies so students can catch them!

 

blue dasher on shoulder

Caught one!  It’s a blue dasher. He marked it with a smiley face ~ can you see it?!

 

 

 

 


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Dragonfly Detectives Results for Year 1 Are In!

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.

storm at Prairie Ridge pondAt 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.

Dragonfly Detectives making observations at pondsAnd 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.

Common WhitetailNow 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.

Girl with damselflyOur 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!


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BugFest!

This year’s BugFest at the NC Museum of Natural Sciences was an amazing event!  There were so many exhibits and fun activities for people to do.  This year the Dragonfly Detectives program had an exhibit in the Citizen Science Exhibit at the Nature Research Center!

Dragonfly Detectives exhibit with Cit Sci educator

During the Dragonfly Detectives program, each group of student scientists record weather data and then conduct timed dragonfly observation periods in order to determine which weather factors affect dragonfly flight the most.  They then create a presentation to share their findings.  These presentations were displayed at BugFest.  As an added perk, the students were all invited to come volunteer at BugFest and present their posters to the public.  This allowed the students to share their findings and show off what they’ve learned.  The students also each received a free BugFest t-shirt.  The students did a fantastic job with the presentations and had a great time!

Student explaining the poster Student explaining the poster Student explaining the poster Student explaining the poster


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Highlights from Prairie Ridge Summer session

The Prairie Ridge summer session is now over but here are a few highlights:

While catching dragonflies, the students caught a common whitetail,

Student with a common whitetail dragonfly

                                                       a blue dasher,

Student with a blue dasher dragonfly

and one student even caught a comet darner!  Comet darners are seen relatively frequently at Prairie Ridge but are not generally common.  As you can see in the picture, they are quite large and they are also VERY hard to catch!

Student with a comet darner dragonfly

One of the days, we had to wrap up the program early because of an incoming thunderstorm.  You can see in the pictures how dark the sky was.  The students were trying to catch dragonflies on this day but had no luck–there weren’t many dragonflies flying around.  Luckily we all made it back to the parking lot before the rain started pouring down!

Students at the Prairie Ridge pond with dark thunderclouds in the sky      Students at the Prairie Ridge pond with dark thunderclouds in the sky

On the last day of the program, the students created a presentation to display and share their results of the data collection.

Students writing text for their posterboard

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They did a great job compiling the information and made an awesome poster board that will be displayed at BugFest at the NC Museum of Natural Sciences on September 19!

Students with educator holding finished posterboard