On May 14th I wrote about a mass emergence of Spiny Baskettails at Mud Lake but didn’t explain much about how I identified them except to say my identification was based on the shape of the male claspers. Emerging dragonflies are pale and translucent, showing little to no colour of the mature adults they will become, but fortunately identification of the three small baskettail species in Ottawa does not depend the pattern of colours on its body (a fourth species, the Prince Baskettail, is much larger and has distinctive black spots at the base, tip and center of its wings). This post provides more detail about how to distinguish between the Common Baskettail, the Spiny Baskettail, and the Beaverpond Baskettail, three similar-looking species of the emerald family. While they are most likely to be found patrolling sunny woodland openings or grassy spaces next to water, they often perch on tree branches and plant stems at an angle, allowing good views or photographs.
Baskettails have black, spindle-shaped abdomens with orange stripes along the sides. Their eyes are reddish-brown when they emerge, and can be green or bluish-green at maturity. Spiny and Beaverpond Baskettails usually emerge first, typically in mid-May, while Common Baskettail emerges slightly later in May. The Common Baskettail also is seen later than the other two species in the summer, suggesting individuals emerge over a period of at least a month rather than over a much shorter period of time.
Of the three species in Ottawa, the Common Baskettail is the easiest to identify at a distance or in flight. The black patches at the base of the hindwings are much larger in this species, giving it a similar look to the saddlebags of southern Ontario. This field mark is variable, however, and can be smaller in individuals found in other parts of its range. It is also the least likely of the three to perch in my experience!
Fortunately, the male claspers are large enough that they can also be used to easily distinguish between the three species if you can see them clearly with binoculars or a good photo. They need to be viewed or photographed from the side rather than from above.
The upper clasper of Beaverpond Baskettail is very angular compared to the others, with the tip pointing down at a sharp angle and a small dorsal tooth projecting upward. A second smaller tooth protrudes downward from the center of the appendage.
In comparison, the upper clasper of the Spiny Baskettail is sinuous, like the shape of a tilde or sideways “S” where the end turns upward. A single sharp tooth protrudes from the upper clasper close to the base. I note the individual shown here is a teneral from my visit to Mud Lake; the claspers have not yet turned black (two teeth are shown here, one from each upper clasper).
Finally, the upper claspers of the Common Baskettail are relatively straight in comparison, with the tip being thicker than the base and an abrupt transition between the thicker and thinner sections.
Females are more difficult to identify as they do not have distinctly shaped claspers; however, the terminal appendages of the Spiny Baskettail are long and close together, while those of the Beaverpond Baskettail are short and close together. The appendages of the Common Baskettail are short and far apart. Size and distance can be difficult to judge if only one species is present, so a better way to identify one is to catch it and look on the underside of its body to examine the shape of the genital plates – which are distinctive in each species. The below female Spiny Baskettail has long appendages (green arrow) and genital plates that curve inward without meeting at the top (white arrow). I don’t have any photos of any Common Baskettails or Beaverpond Baskettails for comparison, but images of each can be found in the Field Guide to the Dragonflies and Damselflies of Algonquin Park which covers the Ottawa region.
There is one other way of distinguishing between the Spiny and Beaverpond Baskettails that doesn’t rely on magnified views of the dragonfly’s naughty bits. The colour of the back of the eyes is a seldom-described but useful field mark, particularly if you manage to photograph the insect from behind: in Spiny Baskettails the colour is black, while in Beaverpond Baskettails it is yellow:
I checked my photos of the Common Baskettail to see what colour it is behind the eyes; the upper half is yellow, while the lower half appears to be black!
While I used to see more Beaverpond Baskettails than Spiny Baskettails when I first started catching odes, this year I’ve seen more Spiny Baskettails. My only Beaverpond Baskettail was seen at Steeple Hill Park, while I’ve had Spiny Baskettails at the Eagleson ponds, Steeple Hill Park, Sarsaparilla Trail, and Mud Lake. So far I’ve seen Common Baskettail at Shirley’s Bay and the Eagleson Ponds, but they’ll be flying for a little while longer yet.
So there you have it – a few different ways to distinguish between the three small baskettail species on the wing in May and June in the Ottawa region!