Follow by Email

Wednesday, September 3, 2014

WILDLIFE WEDNESDAY: DRAGONFLIES AND DAMSELFLIES





Flame skimmer (Libellula saturata) is one of the more striking (and common) dragonflies on Tejon Ranch. Photo courtesy of Chuck Noble
Late summer in California is often seen as a time of senescence. Hot temperatures and dry conditions conspire to make many plants lose their leaves (drought-deciduous) and force animals to estivate. Fortunately for us naturalists, we can use this time to seek out water sources and turn our attention to insects. In particular, dragonflies and damselflies (members of the order Odonata) present themselves as some of the most colorful, acrobatic, and fascinating creatures around. 

Mesurupetala dragonfly fossil By Daderot (Daderot), via Wikimedia Commons
Part of what makes this order so fascinating is how ancient it is. Fossil records provide evidence that dragonflies and their kin have been on planet Earth since before dinosaurs. According to the University of California Museum of Paleontology website, dragonflies have been around since the Carbonifeous - that is over 300 million years!


Dragonflies and damselflies are also fascinating because of their life history. After hatching from their eggs, dragonfly larvae live underwater as jet-propelled hunters. That’s right- they take water from their mouth and shoot it out of their rear end to generate rapid bursts of movement. Damselflies in contrast will wiggle their abdomens from side to side as a means of propulsion. If their hunting speed wasn't formidable enough, these larvae also have a labium, or lower lip that they project forward in order to catch their prey (Biggs, 2004). It's almost like these creatures are miniature versions of the extraterrestrials in the Alien movies! Members of the order Odonata typically spend extended periods of time in their larval stage. In the case of some species of dragonfly, it can take up to 6-7 years before they find a dry place to emerge as adults. 



Blue dasher (Pachydiplax longipennis) adult perched above the abandoned larval exoskeleton of a larger dragonfly. Photo courtesy of Chuck Noble

Once they emerge as adults, dragonflies and damselflies become aerial hunters extraordinaire. Dragonflies in particular have been observed as having a hunting success rate around 95%! Check out this New York Times article (http://www.nytimes.com/2013/04/02/science/dragonflies-natures-deadly-drone-but-prettier.html?pagewanted=all&_r=0) if you don’t believe it!


One of the biggest factors contributing to their success as hunters is how their flight has evolved. Unlike many other insects, dragon and damselflies can move each of their four wings independently, allowing them to move forward, backwards, and make immediate stops. The two videos below provide some great information about how these can be so maneuverable.




In addition to their incredible life histories, dragonflies and damselflies can be extremely fun to watch and identify in the field. Like most insects, their relatively small size and fast flight can make it difficult to tell one species from the next. However, there are a few rules of thumb that can help:


First, it is important to know whether you are looking at a dragonfly or a damselfly. Dragonflies tend to be larger and keep their wings out when at rest. Damselflies, on the other hand, are typically smaller, much more slender, have a bug-eyed look where their eyes stick out to the size of their heads, and often hold their wings along their bodies when at rest (unless they are spreadwings, which hold their wings in a posture in between dragonflies and most damsels).


Next, look for bold patterning on the wings and body of your insect. These markings can indicate what species you are looking at and whether it is a male or female. Size can also be a great clue for helping you determine exactly who you are looking at. 

This eight-spotted skimmer (Libellula forensis) has a distinctive wing pattern

Filigree skimmers (Pseudoleon superbus)  of Arizona and New Mexico also have distinctive wing patterns and interesting markings along the thorax.


One of the best ways to figure out which species you have encountered is to look at a field guide. We recommend these:

Dragonflies of California and the Greater Southwest by Kathy Biggs

Dragonflies and Damselflies of California by Tim Manolis

Dragonflies and Damselflies of the West by Dennis Paulson

There are also some great web resources for identifying these incredible creatures:



References:

Kathy Biggs, Common Dragonflies of the Southwest (Sebastapol: Azalea Creek Publishing 2004), 9.

University of California Museum of Paleontology website (http://www.ucmp.berkeley.edu/arthropoda/uniramia/odonatoida.html). Accessed 3, Sept 2014