Mexico, USA & Canada
Family - PIERIDAE
subfamily - COLIADINAE
© Tony Hoare
The subfamily Coliadinae includes the Sulphurs,
Grass Yellows, Clouded Yellows and Brimstones.
The genus Phoebis
comprises 8 species. Most are migratory, and widely distributed
throughout the neotropical region. There are however a few
non-migratory and very localised species -
avellaneda which is found only in Cuba,
editha which is endemic to Haiti, and
bourkei - found only in Ecuador.
Phoebis species are sexually dimorphic.
Males are bright yellow above, with a thick patch of matt
androconial scales around the forewing cell. Females are paler on
both wing surfaces.
Both sexes of
sennae are subject to variation. Many
examples are entirely devoid of markings, but others are quite
heavily mottled with brown on the underside, and have brown-edged
white stigma at the end of the cell on both wing surfaces.
Phoebis sennae is the commonest and
most widely distributed species. It is found from the southern
states of the USA to Peru, Chile, Bolivia and Argentina. It also
occurs on most of the islands in the Caribbean Sea. There are 4
named subspecies, 2 of which occur in the USA:
marcellina in the west, and eubule
in the east.
As with other Phoebis species,
sennae is highly migratory in behaviour
and can be found in a huge variety of open habitats
e.g. in clearings and glades in deciduous woods, and in grassland,
farmland and suburban habitats. It can be found at altitudes between
sea level and at least 1500m.
The eggs are laid singly on the underside of
leaves of the foodplant Cassia (
Caesalpinaceae ). The young larva is yellow, covered with tiny black
dots. Later it becomes more greenish, with blue bands between the
segments. The fully grown larva is yellowish-green, covered with
black dots, and has a yellow lateral line. Above the line on each
segment there is a series of short vertical blue striations. The
spiracles are also blue. The pupa is beautifully shaped, with an
arched body and projecting wing pads. When newly formed it is pale
greenish-yellow, but this soon changes to become pinkish. It can be
found attached to stems of the foodplant, and looks like a
discoloured withering leaf.
Males can be found mud-puddling at damp
patches of ground. The paler females are seen less often and are
usually observed in flight, or when visiting red or orange flowers
such as Lantana. There is no courtship
ritual - the females are intercepted in mid-flight and forced to the
ground where copulation takes place immediately.