I spotted this caterpillar crossing the narrow gravel trail at Hurdman on August 28th and was immediately intrigued by its bristly appearance and warm fall colours. It was about as long as my index finger, and had yellow markings on the black face and body which made it easy to identify as a Salt Marsh Moth caterpillar (Estigmene acrea). This species received its name because it was once believed to be a pest of salt-grass hay grown near Boston; however, the caterpillars feed on a wide variety of plants, and are much more likely to be found feeding on broadleaf weeds rather than grasses.
This species’ range covers almost the whole North American continent except the extreme northwestern corner (Alaska and Yukon) where it can be found in open wooded areas, meadows, farm fields, weedy waste places, prairie grasslands, and marshes – including salt marshes. A member of the Tiger Moth family, this species has two generations per year in southern Quebec and Ontario, and 3 or 4 generations in the south. This caterpillar will overwinters as a pupa in a spacious cocoon, then emerge as an adult in early spring. The late-instar caterpillars are active dispersers, and may be found traveling singly or in large numbers in search of suitable food. Their diet includes many weedy plants, plus crops such as beans, beets, carrots, celery, clover, corn, lettuce, onion, peas, tomatoes, and turnips. Large numbers feeding in the same area may skeletonize the foliage, which is why they are considered pests. Rarely, they may also feed on the leaves of deciduous trees and shrubs such as alder, apple, cherry, poplar, and serviceberry.
Adults are nocturnal and are attracted to light. The males are quite stunning, with black-speckled white forewings and yellowish-orange hindwings (females have mostly white hindwings). With a wingspan of 45-68 mm, it is not a small species, and one that I would definitely love to see one day! In the meantime, I was worried that the caterpillar would get stepped on, and moved it to the side of the trail where it quickly began scurrying up the vegetation.
I had a great insect day the following day at Sarsparilla Trail. The goldenrod blooming between the outhouse and the picnic shelter was a magnet for all sorts of interesting bugs, including Tri-coloured Bumble Bees, White-faced Meadowhawks and Autumn Meadowhawks.
At the pond, a large Northern Watersnake was dozing on a log right beside the boardwalk. It looked very well fed.
As I was photographing the snake I noticed a couple of darners foraging in the area, zipping up and over the boardwalk before continuing their flight over the cattails. One decided to land on the boardwalk railing, and I got close enough to see that it had a thin dark line across the face. This seemed unusual to me, as our common darners (Canada and Lance-tipped) are not supposed to have a facial cross-stripe. Lake Darners, which do have facial cross-stripes, do not seem to be found on the Ottawa side of the OFNC circle. They are considered “rare and local” on the OFNC checklist, however, I have never seen one at any of the places I frequent in Ottawa and suspect they may be more common on the Gatineau side. Although Lake Darner was a tantalizing possibility, the shape of the thoracic stripe (although partially obscured) and the shape of the claspers pointed toward Canada Darner instead.
After enjoying my time at the boardwalk, I was heading back to my car when I spotted this Monarch butterfly flying gracefully in the open area near the outhouse. This was only the second one I’ve seen this summer, and as it looked as though it were going to land in the goldenrod, I hurried over in time to get this photo (as it turns out, I saw four more Monarchs in September, but this was the best photo that I got):
A White Admiral was also in the area, and while I was examining the meadowhawk dragonflies, this red-faced beauty caught my attention. The black legs rule out Autumn Meadowhawk, the most common red-faced dragonfly in the late summer and fall. It is either a Ruby Meadowhawk or (more likely) a Cherry-faced Meadowhawk. I needed to catch it in order to identify it, and my net was back in my car.
I decided to try and catch it with my hands, and so I cupped them together and slowly brought them down on top of the dragonfly. This didn’t work; he immediately flew out from under them and landed on top of my right hand. This absolutely counts as an instance when a dragonfly has landed on me, so I took its picture as proof (which was difficult with just my left hand)!
Dragonflies are not the only cooperative predators I’ve found recently. On August 30th I found a Robber Fly eating a moth on the side of a tree at Trail 26 on West Hunt club.
Orbweavers seem to be slightly more numerous this year than they were in the three previous years when they seemed to have all but vanished. At Hurdman I found two species: a Black and Yellow Argiope on August 28th, and a Shamrock Orbweaver on September 1st.
This is the first time I recall seeing the Shamrock Orbweaver at Hurdman, and I saw it again in the same spot on September 3rd. It was in the tall grass on the south side of the transitway, and I wasn’t able to get close enough to for a macro photo. This one was taken from next to the bike path.
Another cool insect I saw was a Pearl Crescent at the Rideau Trail on September 5th. They are normally hard to differentiate from the similar-looking Northern Crescent, except that this butterfly was absolutely TINY. The aster flower it was feeding on was one of the smaller species, about the size of my thumbnail. Fortunately it was a male, which are not as similar in appearance as the female Pearl and Northern Crescents. The hindwings lack the large open orange area found in most male Northern Crescents, which – in addition to its tiny size – points to Pearl Crescent as a definitive ID.
With respect to the difficulty in identifying the three eastern crescent species (Northern, Pearl, and Tawny), it is perhaps telling that when prominent lepidopterist James Scott, author of The Butterflies of North America, was asked to identify individual crescents from photographs taken during the Vermont Butterfly Survey, he was unable to confidently identify most of the individuals photographed, stating that the key characteristics were not visible. The difficulty arose because (a) females of the three crescent species are more similar than are males; and (b) characteristics of the male crescents vary considerably, and often overlap between species.
As a result of James Scott’s inability to ID most of the crescents in the photos, the Vermont species account for Northern Crescent states that the “only specimens confidently identified were those that contain most of the key characters in a state that is most different from the state possessed by most of the typical or most different individuals of the other species”. In other words, I am perfectly content with ignoring any crescents I find when out looking for butterflies, rather than agonizing over the ID!
Spreadwing damselflies, on the other hand, are much easier to identify. Mud Lake is one spot where it is possible to see a few different species, and on September 5th I saw a Slender Spreadwing in the woods near the edge of the lake. The proportions of this damselfly alone are enough to identify it, however, the whitish edges of the curves of its wings and squared-off claspers are also key features to look for in this species.
Even though bird migration is already underway, the insects this time of year are still fascinating in their own right. It’s great to see the variety of butterflies, odonates, spiders and flies that are still present as we head into fall.