When two are more species are listed together, they are difficult to distinguish in the field but differ by structural characteristics that are explained and illustrated in more technical books such as The Dragonflies of British Columbia , by Robert Cannings and Kathleen Stuart, or The Odonata of Canada and Alaska , by Edmund Walker. Males and females can be distinguished as follows. An important feature for identification in some families is the vulvar lamina under the 9th abdominal segment that supports the eggs about to be laid. The definitive coloration of adults is acquired slowly with maturation, and individuals that are not yet mature may not be fully colored. Male dragonflies on territory at the water or individuals of either sex engaged in reproductive behavior will surely be mature.
Some adults become pruinose , with a blue or whitish powdery bloom that covers parts of the body.
Note the rectangular pterostigma near the tip of each wing. Both have a greenish thorax, the former with a conspicuous stripe on the side and the latter without. This information is provided by the Slater Museum of Natural History . Back to Dragonfly Biodiversity . All rights reserved.