Pieris oleracea, or more commonly known as the mustard white, is a butterfly in the family Pieridae native to a large part of Canada and the northeastern United States. The nearly all-white butterfly is often found in wooded areas or open plains. There are two seasonal forms, which make it distinct from other similar species. Because of climate change, populations are moving further north.
As indicated by the common name, P. oleracea adults and larvae primarily feed on plants in the mustard family, Brassicaceae. The species is threatened by the rapid, and monoculture-forming, spread of the invasive species Alliaria petiolata, which is toxic to larvae. Populations of P. oleracea have been declining. It may be that this butterfly is slowly adapting to garlic mustard. However, it may not be a fast enough process to ensure its survival, due to the high level of aggression on the part of the plant and the continuing encroachment of human development.
Its specific name oleracea means "related to vegetables/herbs" in Latin and is a form of ().
Description
Larvae
Pieris oleracea larvae are yellow and shaped like cones, with vertical ridges. Researchers have said that the univoltine nature of Pieris virginiensis, coupled with its rarity, makes A. petiolata potentially an even greater threat to its survival, due to a reduced ability to adapt.
Enemies
Alliaria petiolata
Alliaria petiolata is a toxic invasive species that is causing decreased survival in larval populations.
Pieris rapae
thumb|Image of [[Pieris rapae]]
Another potential enemy of P. oleracea is a member of its own genus, Pieris rapae. After introduction of this species in an area in New England populated by P. oleracea, the native populations were entirely wiped out. In many cases this appears to be because of competition for foraging sites. However, there has been a case observed where the two species were able to coexist successfully.
Sympatry
A specific case of sympatry between P. oleracea and P. rapae was seen in Vermont. Even though the populations had approximately the same territory, each species was able to find a specific niche in the food source or habitat that the other could not use. P. oleracea larvae primarily used Dentaria diphylla during the spring, whereas P. rapae used Barbaea vulgaris in the spring. As for mating, there was no observed interference between the two species. Even though adults were in the same areas, there was no conflict.