Clouded Yellow (Early Stages)
Posted: Wed Nov 11, 2020 12:30 pm
The Clouded Yellow is a migrant to the shores of Britain and Ireland, arriving in varying numbers every year from its strongholds around the Mediterranean and North Africa. There can be up to three broods arising from the initial influx in May and June and there is a limited return migration in autumn. No stage of the butterfly is usually able to survive winters in most parts of Britain and Ireland, but in recent years there has been increasing evidence of larvae regularly overwintering in some sheltered southerly coastal locations. This species is also notable in that approximately 10% of the females are a pale form (f. helice).
The Egg
The principal larval host plants are clovers (Trifoliun spp.), but other important species are Bird’s-foot-trefoil (Lotus corniculatus) and Horseshoe Vetch (Hippocrepis comosa). Eggs are laid individually, usually on the upper sides of leaves. Their colour is white when freshly laid, turning gradually pale yellow and then orange after a few days.
In the hours prior to hatching the egg turns a dull purple/grey, with the larva chewing a hole near the top in order to emerge. *The use of flash shows the interior of the egg more clearly than usual in some of the photos.
Larva - General Behaviour
The Larva generally feeds in the open, on the upper side of a leaf. After feeding it will rest on a silk pad spun on the upper side of a leaf and facing away from the feeding area, usually towards the leaf stem. However, on small-leaved plants such as Horseshoe Vetch or Bird’s-foot-trefoil, where the larva may become too large to sit on an individual leaf, it may rest on a stem, usually head-down. It will moult on a silk pad spun usually on the upper side of a leaf, but on small-leaved plants, moults may also take place on a stem with the larva either facing head-up or head-down and the old larval skin is eaten after every moult. Larvae are tolerant of each other and will feed in close proximity without disturbance. As the larva grows, it becomes apparent that it has a mechanism in its rear end for flicking frass away from its body and the plant. Larvae were observed to feed by day and night, but this may not be typical behaviour in the wild.
First Instar
After hatching the larva immediately consumes the empty egg shell as its first meal. The first meals on the leaf are usually on the upper side and involve grazing on the outer cuticle, but without perforating it and leaving characteristic feeding damage. The first instar larva has a black head and is a greenish-yellow when first emerged, but gradually turns more yellow as it grows.
Second Instar
The second instar larva has a brownish-green colouration, with a pale brown head. A very faint white line may be visible at the base of its flanks as it approaches its next moult. When feeding it will now perforate the leaves, but will also feed on the sides of tender leaves.
Third Instar
The third instar larva now has a green head and body, with a white stripe along its flanks.
Fourth Instar
The fourth instar is initially similar in appearance to the previous stage but develops a faint row of yellowish-orange spots in the white line along its flanks, but only towards the end of its growth period. Larvae can be sexed at this stage of their development, but only when the body is back-lit. In this circumstance a pair of very faint elongated purple-grey patches can be seen under the skin on the back of the larva at its eighth segment. These patches are the developing testes of a male larva (and were found to be impossible to photograph). At this stage larvae will sometimes rest with the front part of their bodies slightly raised.
Fifth Instar
The fifth instar larva initially has the same colour and arrangement of yellowish-orange spots along its flanks as the fourth instar, but it is a noticeably darker green in colour compared to the pale green of the previous stage. This now makes sexing the larva more difficult. Stronger orange, yellow and black colouration in the side stripes develops gradually and can be quite variable between larvae. One of the larvae (L2) only developed yellow colouration and not the orange.
When fully grown, the larva will attach itself to a stem or other piece of vegetation by means of a silken pad at its tail and a silk girdle at its middle. This can be either in a vertical or horizontal position. Its colouration will pale and it will hang suspended in a “D” shape for around 24 hours before pupating.
The Egg
The principal larval host plants are clovers (Trifoliun spp.), but other important species are Bird’s-foot-trefoil (Lotus corniculatus) and Horseshoe Vetch (Hippocrepis comosa). Eggs are laid individually, usually on the upper sides of leaves. Their colour is white when freshly laid, turning gradually pale yellow and then orange after a few days.
In the hours prior to hatching the egg turns a dull purple/grey, with the larva chewing a hole near the top in order to emerge. *The use of flash shows the interior of the egg more clearly than usual in some of the photos.
Larva - General Behaviour
The Larva generally feeds in the open, on the upper side of a leaf. After feeding it will rest on a silk pad spun on the upper side of a leaf and facing away from the feeding area, usually towards the leaf stem. However, on small-leaved plants such as Horseshoe Vetch or Bird’s-foot-trefoil, where the larva may become too large to sit on an individual leaf, it may rest on a stem, usually head-down. It will moult on a silk pad spun usually on the upper side of a leaf, but on small-leaved plants, moults may also take place on a stem with the larva either facing head-up or head-down and the old larval skin is eaten after every moult. Larvae are tolerant of each other and will feed in close proximity without disturbance. As the larva grows, it becomes apparent that it has a mechanism in its rear end for flicking frass away from its body and the plant. Larvae were observed to feed by day and night, but this may not be typical behaviour in the wild.
First Instar
After hatching the larva immediately consumes the empty egg shell as its first meal. The first meals on the leaf are usually on the upper side and involve grazing on the outer cuticle, but without perforating it and leaving characteristic feeding damage. The first instar larva has a black head and is a greenish-yellow when first emerged, but gradually turns more yellow as it grows.
Second Instar
The second instar larva has a brownish-green colouration, with a pale brown head. A very faint white line may be visible at the base of its flanks as it approaches its next moult. When feeding it will now perforate the leaves, but will also feed on the sides of tender leaves.
Third Instar
The third instar larva now has a green head and body, with a white stripe along its flanks.
Fourth Instar
The fourth instar is initially similar in appearance to the previous stage but develops a faint row of yellowish-orange spots in the white line along its flanks, but only towards the end of its growth period. Larvae can be sexed at this stage of their development, but only when the body is back-lit. In this circumstance a pair of very faint elongated purple-grey patches can be seen under the skin on the back of the larva at its eighth segment. These patches are the developing testes of a male larva (and were found to be impossible to photograph). At this stage larvae will sometimes rest with the front part of their bodies slightly raised.
Fifth Instar
The fifth instar larva initially has the same colour and arrangement of yellowish-orange spots along its flanks as the fourth instar, but it is a noticeably darker green in colour compared to the pale green of the previous stage. This now makes sexing the larva more difficult. Stronger orange, yellow and black colouration in the side stripes develops gradually and can be quite variable between larvae. One of the larvae (L2) only developed yellow colouration and not the orange.
When fully grown, the larva will attach itself to a stem or other piece of vegetation by means of a silken pad at its tail and a silk girdle at its middle. This can be either in a vertical or horizontal position. Its colouration will pale and it will hang suspended in a “D” shape for around 24 hours before pupating.