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| 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.
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| 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.
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| 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.
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| This eight-spotted skimmer (Libellula forensis) has a distinctive wing pattern |
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| 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:
Kathy Biggs Website- http://bigsnest.members.sonic.net/Pond/dragons/
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
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
