Dragonfly Science

Water quality indicators

Dragonflies and damselflies offer important clues about ecosystem health.

Dragonflies are predatory, capturing other insects in mid-flight!

By monitoring dragonflies and damselflies (collectively known as Odonates) every year, we can create a picture of the changes in composition and seasonality of local and migratory populations.

We began surveying dragonflies and damselflies in our watershed in 2016, and we’ have continued each year’ve added additional sites as our community scientist interest has grown. In fact, we’ve learned that the Johnson Creek Watershed is home to three of the five main species of migratory dragonflies in North America: the common green darner, the variegated meadowhawk, and the black saddlebag.

What we’ve discovered together –

Climate change is affecting dragonflies and damselflies.

23

Species

4

Sites

1000+

Observations

Dragonflies can spend several years underwater as larvae before emerging and transforming into winged adults.

Odonate surveys can provide important information about changes in habitat quality, as well as impacts of climate change.

Life History

When talking about dragonflies and damselflies, we often just say “dragonflies” as shorthand. But this leaves out the poor damselflies, which are closely related. Dragonflies and damselflies are a bit like cousins, and if you want to talk about both, you can use the word “odonate.”

Odontos is the Greek word for tooth. Odonates are carnivorous as nymphs and adults, and the nymphs are characterized by toothed mandibles (jaws) at the end of a long, extendable mouth part.

It’s actually pretty easy to tell the two apart! Just look at three key features- their eyes, body, and wings.

Dragonflies have much larger eyes than damselflies– in fact, most of a dragonfly’s head is actually its eyes. Damselflies have a bit of space between their eyes.
Dragonflies have bulkier bodies and are a bit shorter and thicker than damselflies, which tend to have narrow bodies.  
While at rest, a dragonfly’s wings spread out horizontally, like an airplane. Damselflies fold their wings up and over or alongside their body.

Dragonflies & Damselflies

The goal of these surveys is to document:

  • Diversity, or the number of species found in the watershed
  • Abundance, or how many of each species might live in the watershed. 
  • Timing of species’ occurrence: When do adult dragonflies and damselflies first appear in our watershed? How might this compare with other local areas, or with other years? 

The most common species found throughout Johnson Creek are the tule bluet damselfly (Enallagma carunculatum), the Pacific forktail damselfly (Ischnura cervula), and the blue dasher dragonfly (Pachydiplax longipennis). 

Methodology​

Volunteers conduct surveys about every two weeks. Odonate activity fluctuates a lot with temperature, cloud cover, wind, and more, so the timing of surveys may vary based on when conditions are optimal. Surveyors are armed with a net, hand lens, dichotomous key for identifying odonates to the family level, and a field guide to identify them to the species level. Volunteer teams walk transects along a water’s edge at each site, taking photos and netting individuals when possible. They record species, abundance, genders, and reproductive stage.

Early in the season, our teams are especially careful to avoid netting newly-emerged odonates that have delicate wings. (You can tell an odonate emerged recently because their wings have a soap-bubble appearance.) All of our data is reported on iNaturalist.

Survey methods were developed by C. Zee Searles Mazzacano of CASM Environmental. Zee is our entomologist extraordinaire and scientific advisor on this project.

The wandering glider has the longest-known insect migration in the world!

2022 Survey Results

The 2022 season started cold and wet, delaying the onset of flight activity, and the subsequent hot and dry summer reduced available habitat at some survey sites by early August. Nevertheless, a total of 21 species (16 dragonfly species and 5 damselfly species) were identified on surveys conducted between June 19 and October 16, 2022. No new species were observed. Typically, surveyors identify between 18 and 23 species each year, but in 2022, surveyors made twice as many observations (280) than in 2021, likely a result of fewer sample sites and the shortened flight season in 2022.

Species richness, defined as the number of species within a defined area, varied across sites. In 2022, surveyors saw the most species at Sunset Village and the fewest at Centennial. Species richness also differed from previous years for sites with data from more than one year. The low species richness at Centennial in 2022 was in sharp contrast to the 2021 – the year following habitat restoration when the highest number of species was observed. Richness at Brookside (16 species) ins 2022 was lower of any monitoring year at that site. Single day counts were highest at Tegart/Ponza and Sunset Village.

The higher incidence of species with adaptations for drying (e.g., saffron-winged meadowhawk [Sympetrum costiferum] , striped meadowhawk [Sympetrum pallipes], and California spreadwing [Archilestes californicus]) may indicate that the drier, hotter weather is favoring species that are not as reliant on open water for laying eggs.

Total number of odonate species reported at each monitoring site (data courtesy CASM 2022)

Although local environmental conditions were similar, habitat-driven differences in odonate communities were evident among sites. Lower richness at Brookside in recent years reflects reduced habitat suitability; in earlier years, the site had open water and fringing vegetation that attracted local species, but in recent years water levels are lower and by mid-summer in 2022 large portions were reduced to cracked mud or filled in with vegetation.

Richness at Centennial has varied more annually, reflecting the physical changes that occurred. Restoration initially saw increased odonate abundance and richness, but Centennial is now experiencing summertime wetland drying, dense plant overgrowth of the creek, and mowing in the adjacent upland, which reduces available habitat.

The new monitoring sites, which are stormwater ponds of varying ages and size, retained water throughout the season and provided more heterogeneous habitat.

This project demonstrates that even disturbed urban wetlands can support a variety of regionally common odonate species and occasionally host rarer species, but some degree of maintenance is needed to ensure the habitat does not become less attractive or unable to support odonate development.

This summary was adapted from Mazzacano, C. Zee Searles. 2022. Community Science in Johnson Creek Watershed:
Dragonfly & Damselfly Monitoring: Final Report for 2022. CASM Environmental, LLC. 30 pp.

In a migration that lasts for several generations, some populations of wandering glider travel 11,000 miles from India to Mozambique, twice the distance traveled by monarchs!

How to get involved:

Help Johnson Creek Watershed Council document the distribution of dragonfly and damselfly species by participating in our community science programs!  Check our events page in June to sign up for our Dragonfly Orientation to take part in the surveys.

Scroll to Top