The Large White, Pieris brassicae
The Large White is on average larger, and some say a stronger flyer, than the Small and Green-veined Whites, but it is often very difficult to distinguish between the three species unless fairly good views are obtained of the butterflies at rest. Then the details of the wings may be picked out.
Both the Large White and the Small White have rather uniform yellowish hind underwings, which distinguishes them from the Green-veined White with its heavily patterned hind underwings, i.e. with the veins picked out with greenish markings.
The difference between the Large White and the Small White is then in the shape of the dark “corner mark” at the tip of the forewing. In the photograph below, see how the dark “corner mark” sweeps around the tip of the forewing, making a “boomerang” shape. This is characteristic of the Large White, irrespective of gender. The dark “corner mark” is on the upper surface of the wing, so shows up well on the far wing in this photograph where the upper side is visible, but is actually quite difficult to see on the near wing, where you are looking at the lower side of the wing.
This is a female because it has two spots (and a dark streak, less commonly seen) on each front wing, the second spot of which you can only just see. These spots are much more visible on the underside of the wing than the corner marks.
In this photograph below, the wings are closed and only the lower side of the near wing can be seen, so the dark “corner mark” is heavily obscured and only just visible. However it can still be seen (faintly) to be a “boomerang” shape, so this is definitely another Large White butterfly, and again it is a female, with the two dark spots on the fore wing. in both sexes there is also a black spot on the fore edge of the hind wing, which shows through to the underside slightly.
The Large White wanders freely across the parish and is also found everywhere in Kent.
Its distribution internationally is throughout the majority of Europe, Asia and North Africa. It is now found in South Africa as well but has not established itself in Australasia or the Americas. In 2010 it was discovered in New Zealand, but thorough and immediate control measures were taken and it was declared completely eradicated in 2014.
The first brood of adults appears around April, the second around July and there may be a partial third later in the year. The later generations of adults are darker in their markings than the spring generation. After the last summer generation of adults, their larvae each develop as far as pupating in a green-white chrysalis and enter a winter diapause or hibernation stage, until the next year’s adults emerge from the chrysalis in the following April. The butterfly is a strong flier and is able to migrate long distances. The adult population in the UK is regularly bolstered by immigration from the continent, so adults seen in Hadlow could have flown here from France or Spain. Here is one in the second generation nectaring off a Knapweed flower, I wonder where it came from?
Mating takes place on the wing. The females are monogamous, or perhaps serially so, and after a mating they are able to lay fertile eggs for up to two weeks. Before the two weeks are up they will most likely have mated again, and be able to continue laying fertile eggs. They lay cylindrical yellow eggs in clumps on the underside of the leaves of the food plants, which become more orange as they age. When laying an egg, the female locates one previously laid with the tip of her abdomen and so builds up the regularly arranged batches.
The better fed the females are, the more eggs they lay. Cabbage growers may therefore perhaps not actually be very keen on nectar sources around their fields!
The larvae are yellowish in colour with black spots, eventually becoming greenish on the top surface with black spots, and a clearer yellow on the underside, and with black and grey heads. They feed in increasingly loose groups, spreading out a bit as their appetites increase.
This is the butterfly that does most damage to cabbages, kale and nasturtiums in gardens. It is voracious!
Females are attracted to green colours. When they reach a green surface, they then “drum” on it with their feet. They are then able to detect the mustard oil glucosides present in cabbages and other food plants using special hairs in their feet, and these are thought to stimulate them to lay their eggs. As long as their feet are on a cabbage leaf, they will then lay their eggs on any suitably placed piece of paper or glass!
Newly hatched caterpillars are frequently attacked by the females of some parasitic wasp species, including those Braconids in the genus Cotesia, which used to be known as Apantales.
The larvae of Large White Butterflies secrete some chemicals that make them distasteful to various predators. Predators of the adult Large White Butterflies do include different birds, although there is a lot of carry-over of the chemicals from the larval stage into the adult butterflies.