Green-veined White

The Green-veined White, Pieris napi.

There are two generations of Green-Veined White adults to be seen in Hadlow in most years, the first between the start of April and the end of June, the second (much more numerous) generation in July and August.

Description

This is a male of the second generation, showing only one dark spot (as opposed to two, which would indicate a female) on the upperside of the forewing:

This is another male of the same generation, with the same corresponding dark spot on the top of the front wing, seen in Dene Park. The dark wing “corner-mark” is quite triangular and fairly evenly balanced between the two edges of the wing. It is rather “jagged” on its inmost edge, which I also think is typical of this species.

Both sexes take sugar-rich nectar from flowers, and the males do some “mud-puddling”, possibly to replace salts lost in “nuptial gifts” to the females during the mating process. Here is a male in Combs, Peak district in Derbyshire, seen nectaring in July 2013, just possibly on Valerian.

Distribution

The Green-Veined White can be found in gardens, farmland and woodland across Hadlow, often mis-identified as a Small White. They do like moist environments, so tend to be found more in the woodlands and well vegetated gardens. Nationally this pattern is repeated on a larger scale, they are commoner in the wetter parts of the North and West of the UK.

Life cycle

The small first generation of adults fly between April and June, slightly smaller butterflies than the larger individuals noted in the more populous generation of adults which fly between July and August. The first generation lay eggs and the resulting caterpillars develop quickly, providing it is warm, to produce thin-walled chrysalises to provide the second generation of adults. The chrysalises of the second generation are much tougher, in order to withstand the rigours of hibernation. The difference is controlled by the temperature and daylength that the caterpillar experiences, and can be manipulated experimentally.

The females fly low, and rather jerkily, testing plants for the cruciferous chemicals indicating potential suitable caterpillar food-plants such as Water-Cress, Cuckoo-Flower, Garlic Mustard and Hedge Mustard. The eggs are laid on the underside of leaves of plants that are often small, and in very moist situations.

Why these particular White butterflies have not adapted to feeding off commercial crop plants such as cabbages is a complete mystery to me!

Oddities

When males find females, they flutter nearby, showering the females with clouds of lemon-verbena “love-dust” that even humans can smell! Once mated, the males coat the females with “anti-aphrodisiacs” to deter other males, but this soon wears off, Some females only mate the once, repelling males by spreading their wings wide and sticking their abdomens vertically up in the air. Others may mate up to five times, benefiting from the “nuptial gift” of nutrients donated by males on each successful mating.

Parasites and Predators

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