Thunder Bay Butterflies 2007

The summer of 2007 was an exceptional season for butterflies in the Thunder Bay area. Many species of a more southern affinity were seen, some in record high numbers.

The first indication of an influx of southern butterflies in the spring was the abundance of the Monarch and American Painted Lady starting in mid- to late May. Both species, which migrate north in the spring, were in very high numbers through the spring and early summer.

The next southern species to be seen was a Little Sulphur (also known as the Little Yellow) seen by Sue and Mike Bryan at a boat launch on Sunbow Lake near Quetico Provincial Park on June 10. This was the first recent record of this southern stray for Thunder Bay District.

Also on June 10, a Variegated Fritillary was seen on Alice Avenue. This was the first sighting in our area in at least 10 years, and was a harbinger of many more sightings this year. A strong colony was found on the Thunder Bay waterfront, around the railyards and grain elevators. The first was seen there July 3; the colony was centered in a weedy area where several railroad tracks had been pulled up. The highest count was over 100 individuals Aug. 12; 64 were counted Aug. 18. On both days most were males, patrolling for females. A couple of mated pairs were seen. On Sept. 2 a female was observed to lay an egg on Johnny-Jump-Up, a plant which was growing in fairly high numbers in the gravel, although most plants were small and stunted.

The last two fritillaries were seen there on Sept. 22. Other sightings of this species were at the old Smurfit-Stone mill; and the Bryans saw one Aug. 4 on the Black Bay Peninsula.

The Common Buckeye has been true to its name in the Thunder Bay area this summer. First appearing on June 16, it was recorded at various places, including the Thunder Bay waterfront, Alice Avenue (June 16, NGE), Raith (John Walas), and the Black Bay Peninsula (Aug. 4, Bryans). Second and third generations appeared around the Thunder Bay grain elevators, with a high count of 25 individuals July 30, and 2 fresh adults Sept. 16.

On June 15 John Walas saw a butterfly at the grain elevator weed patches he thought was a Grizzled Skipper. He and I returned there the next day and saw about 15 of these, which turned out to be the Checkered Skipper. Females were observed ovipositing on a prostate mallow plant that was growing around the piles of old grain sweepings from the elevators. The plant keyed out as the Common Mallow. The butterflies we observed were presumably the second generation, and a third generation was seen in August, with a high count of 10 on August 12. The last sighting was Aug. 18. This species had not been recorded in Thunder Bay District before

On July 28, John Walas caught a fresh Dainty Sulphur on the Thunder Bay waterfront. This southern stray was another first record for Thunder Bay District. Subsequent searches in the same area failed to turn up any more of this species.

On Aug. 18, while searching for more Dainty Sulfurs in the same general area, I found a fresh Purplish Copper; we are not aware of any recent records of this species in Thunder Bay District.

On July 30 I found a Checkered White on the Thunder Bay waterfront. This southern species was seen on several more occasions at various locations along the Thunder Bay waterfront and in town, with a strong colony at the old Smurfit-Stone paper mill property, where 30 were counted on Aug. 5. This species has been seen there in good numbers in previous years, and it is possible that the Checkered Whites at that location are a permanent overwintering colony. The last sighting was Sept. 23 at the Thunder Cape Bird Observatory (NGE)

Why did so many southern butterflies appear here this past summer? We suspect that they migrated or strayed north during the hot dry spell that we experienced in the late spring. Once here, they found suitable food plants to lay their eggs, and produced one or more generations locally. They are not expected to survive the winter here; it will be interesting to see if any of these species are observed next summer, 2008

Back to the Butterfly Page