Cloudless Sulphur (Phoebis sennae) (Linnaeus, 1758)
Diagnosis: Among Canadian sulphurs, Phoebis sennae is unique for its clear lemon-coloured upperside. It is also much larger than most other sulphurs (wingspan: 63 to 78 mm). The underside has two silver, blackrimmed spots on the hindwings. The female has a yellow-centred dark spot on the forewing upperside and some black edging.
Subspecies: Only subspecies eubule reaches Canada.
Range: This is an extremely widespread butterfly in the Americas, occurring from the tip of South America to southern Canada. The few Canadian records are all from southwestern Ontario northeast as far as Orillia.
Similar Species: Other large tropical sulphurs that have, or might, reach Canada, such as the Orange-barred Sulphur (P. philea), have some orange on the upper surface. The Large Orange Sulphur (P. agarithe Boisduval) has not yet been recorded in Canada, but has reached Maine and Wisconsin. [compare images]
Early Stages: The yellowish larvae have many small black spots and dark blue transverse bands. They probably have not occurred in Canada because the typical foodplants, mainly from the genus Cassia in the pea family, are not found here.
Abundance: This is a rare stray in Ontario. In the southern U.S. it is usually common to abundant, particularly in years when mass migrations occur. Canadian records are in these migratory years.
Flight Season: Records in Ontario range from May to October.
Habits: This butterfly has large wings and is a strong flyer; the Cloudless Sulphur can cover long distances in its migrations. Adults can be found at flowers and sipping from mud puddles.
Remarks: The appearance of this species in Canada may depend on weather conditions in the southern U.S. On 2 September 1985 PWH saw a large, lemon-yellow butterfly, presumably this species, flying in a Mississauga backyard several days after Hurricane Elena occurred in the Gulf of Mexico.
© 2002. This material is reproduced with permission from The Butterflies of Canada by Ross A. Layberry, Peter W. Hall, and J. Donald Lafontaine. University of Toronto Press; 1998. Specimen photos courtesy of John T. Fowler.