Pieris napi, the Green-veined White is a very common butterfly, similar to [267] the Large White and Small White but with a marked vein-like structure on the under wings.
Taxonomy
Kingdom – Animals
Phylum – Arthropods
Class – Insects
Order – Lepidoptera (Butterflies and Moths)
Family – Pieridae
Subfamily – Pierinae (Whites and Yellows)
Tribe – Pierini
Genus – Pieris
Scientific Name – Pieris napi
Name
[057] Rapeseed is Brassica napus, which is all you need to add to the section about Names for the two species yesterday. (Latin purists will recognize that the masculine napus becomes napi in the genitive, as the feminine brassica and rapa became brassicae and rapae.)
Description
From the top, this butterfly is very similar to the other Whites but the undersides of its wings show the ‘green veins’ that give it its name. Dark scales – from a dirty green colour to brown or almost black – show against the background of the pale yellow or green wings.
It feeds on many of the wild species of Brassicaceae, such as Hedge Mustard, Garlic Mustard, Water Cress, Charlock, Wild Cabbage, Wild Radish and Cuckooflower. (There are too many such species for easy identification and I haven’t been able to include them specifically in these blogs.)
Habitat
Pieris napi is widespread and common across Eurasia and North Africa. In Britain it is even more widespread than the Large White and Small White, including all of Scotland in its range. It is found in hedgerows, forest edges and anywhere with grass.
[267] Pieris brassicae and Pieris rapae, Cabbage White
Introduction
Informally, Pieris brassicae and Pieris rapae are both sometimes called Cabbage White butterflies and most of the general population do not distinguish between the two species. Although one is larger than the other, close inspection may be needed to tell them apart. I will treat them together.
Pieris brassicae, the Large White, Large Cabbage White, Cabbage White or Cabbage Butterfly, is a common and widespread, mostly white butterfly.
Pieris rapae, the Small White, Small Cabbage White, Cabbage White or Cabbage Butterfly, is also a common and widespread, mostly white butterfly, with very similar markings. In some countries where it is non-native and invasive, the larval form is called the Imported Cabbageworm.
More of the usual warnings. There is a plant genus also called Pieris. This duplication is allowed and does happen. There is another genus of butterflies, Pierella, that retains Pieris as a synonym. [It was named Pieris until it was discovered that the name had already been used for another butterfly.]
Taxonomy
Kingdom – Animals
Phylum – Arthropods
Class – Aves (Birds)
Order – Lepidoptera (Butterflies and Moths)
Family – Pieridae
Subfamily – Pierinae (Whites and Yellows)
Tribe – Pierini
Genus – Pieris
Scientific Names – Pieris brassicae, Pieris rapae
Names
Pieris comes from the city of Pieria, home of the mythological Muses of Ancient Greece. (Don’t ask why!)
Both species are widely regarded as agricultural pests because the caterpillars eat cabbages and other species of Brassicaca. Brassica rapa is the Turnip. Hence Pieris brassicae and Pieris rapae. See [057] Rape. (The species epithets take genitive endings, so brassicae means ‘of brassica’ and rapae means ‘of rapa.’)
Description
Pieris brassicae adult butterflies are mostly white with a dark tip on the forewings. Females have two black spots on the forewings and the hindwings are pale yellow. Males are significantly smaller.
Pieris rapae differs in being slightly smaller. The dark tip to the wing is less extensive and males may have a single dark spot.
Everything else about these two butterflies is similar.
The larvae have five instar stages, feeding on wild or cultivated Rape, Cabbage, Brussels Sprouts and other members of the family Brassicaceae. There are two or sometimes three generations each year.
In many places both species are considered pests because of its the damage they can do to crops. In countries like India, they are estimated to reduce crop production by up to 40%.
Habitat
Pieris brassicae is common throughout Europe, Northern Africa and Asia. The resident UK population is normally increased with migrations from Europe. It is less common to the North of Scotland than the rest of Britain. They are found in open country and especially farms and vegetable gardens.
Pieris rapae has a similar natural distribution. It was introduced to Quebec around 1860 and has spread across most of North America and via Hawaii to New Zealand and parts of Australia.
Other Notes
These two species are among the most common British butterflies. It is easy to spot one but much more difficult to decide which species it is.
You will understand that the Large White butterfly is not often confused with the Large White breed of [328] Pig.
See also
[268] The Green-veined White, coming tomorrow is relatively easy to distinguish from these two species.
The Species of Britain 