Butterflies of the World - Lifecycle, Ecology, Taxonomy, Conservation, Photography, Butterfly Holidays, Photo Galleries, Book Reviews and more.........
Text and photographs protected by Copyright © Adrian Hoskins 2007, and must not be published in part or in whole elsewhere without prior written permission from the author.
Butterflies of Britain & Europe
 
Clouded Yellow
Colias crocea GEOFFROY, 1785
Family - PIERIDAE
subfamily - COLIADINAE
 
 introduction | habitats | lifecycle | adult behaviour
 
Clouded Yellow Colias crocea, male, Old Winchester Hill NNR, Hampshire, England
 
Introduction
 
The Clouded Yellow, like most other members of the Coliadinae, is a strongly migratory species. It is a common and widespread butterfly in North Africa and the Mediterranean region, migrating northwards each year, with small numbers arriving in Britain in May and June. Occasionally much larger numbers arrive, with an estimated 36,000 reported in 1947 - the famous "Clouded Yellow year".
 
The immigrant butterflies produce a new generation of Clouded Yellows which emerge in late July and August, which are sometimes supplemented by another band of migrants. In exceptional years there may be a further brood, emerging in October or even November.
 
Male and female Clouded Yellows normally both have deep yellow uppersides with broad black margins, but the females have a row of pale yellow spots within the margins.
 
About 5 percent of females are of a paler whitish ground colour. These are known as f. helice, and can easily be confused with females of the much rarer Pale Clouded Yellow and Berger's Clouded Yellow. In both of the latter species however the hindwing borders are very much narrower.
 
In Europe there are a total of 12 Colias species, and identification is further confused by the presence of sterile hybrids ( e.g. erate x crocea ) in areas where the distribution range of the species overlaps.
 
Habitats
 
The migratory nature of the butterfly means that it can be encountered in almost any habitat. It penetrates well inland, and can be found as far north as the Outer Hebrides. It is found in the highest numbers however along the southern counties of England, particularly in Dorset, West Sussex and on the Isle of Wight.
 
Clouded Yellow Colias crocea, male at roost, Ballard Down, Dorset, England
 
The butterflies breed in cultivated fields of lucerne and clover, and on heavily grazed grassland sites where bird's foot trefoil or horseshoe vetch grow in abundance. They favour south facing slopes over other habitats.
 
Lifecycle
 

The butterfly is multi-brooded in warmer parts of it's range, but in Britain, where it only occurs as a migrant, it normally produces only a single generation, emerging in late summer, the progeny of adults that migrated northwards from the continent in May or June. In particularly warm summers however there may be a partial 2nd brood emerging in the autumn. These late emerging adults, and any resulting eggs or larvae, usually perish in late autumn, but at one or two sites on the south coast of Dorset larvae have recently been found to successfully over-winter, producing a few adults in February or March.

 

The eggs are laid singly, or in two's or three's, on the upperside of leaflets of red clover Trifolium pratense, lucerne Medicago sativa, horseshoe vetch Hippocrepis comosa, bird's foot trefoil Lotus corniculatus, sainfoin Onobrychis viciifolia, kidney vetch Anthyllis vulneraria, black medick Medicago lupulina and other leguminous herbs. They are yellow at first, quickly turning to pink and finally to orange. They hatch after about 7 - 10 days.

 

Clouded Yellow caterpillars are dark green with a pale yellow lateral stripe, and orange dashes between the spiracles. They feed diurnally on the leaves and stems of the foodplants. Caterpillars hatching in May and June feed up and become fully grown within about 3 weeks. Those of the autumn generation however feed very slowly, and nearly always perish with the arrival of the first frosts in early November. In warmer areas they continue to feed during the winter months, and do not enter a state of diapause.

 

The pupae are yellowish green, marked on the wing cases and abdomen with tiny black dots. They are extremely difficult to find in the wild, attached by the cremaster and a fine silk girdle to stems of the foodplants or other nearby plants. The adults emerge after about 18 days.

 
Adult behaviour

 

Both sexes fly very rapidly and purposefully, migrating in search of breeding sites. Once they discover a suitable area they tend to stay for several days, patrolling back and forth on a regular "beat", exhibiting a regular cycle of nectaring, resting and searching for potential mates.

 

Clouded Yellow Colias crocea nectaring at birds foot trefoil, Dorset, England

 

On warm summer days they spend long periods flying restlessly from flower to flower, nectaring at small scabious, field scabious, devil's bit scabious, knapweeds, cat's ear, stemless thistles, mouse-ear hawkweed, marjoram, clovers, trefoils and vetches.

 

When feeding they remain extremely alert, and rarely settle for more than 3 or 4 seconds at a time. A fairly minor and temporary drop in temperature however is enough to cause them to enter a resting phase, when they settle in rabbit scrapes or other depressions, often remaining stationary for several minutes at a time.

 

I have only observed the courtship ritual once. Both sexes were patrolling across a south facing grassland slope. When they met, the male pursued the female until she flew over a ridge and settled on the ground amongst short grasses. She briefly opened her wings, at which point the male settled next to her. The female then closed her wings and the male attempted to get into position alongside her. After a moment she flew again and resettled a short distance away, followed by the male, which fluttered around her on the ground. Without any further courtship the male then got alongside her again, and on this occasion successfully copulated. The pair remained copulated for about an hour. If disturbed the pair will take to the wing, and fly a short distance.

 
                                                       
Almost every British and European species of butterfly is declining rapidly in numbers, due in most cases to loss or degradation of habitats.
 
You can help to reverse the decline by supporting conservation organisations which purchase and manage habitats as nature reserves, and which lobby government at local, national and international levels, often very successfully, to bring about changes in farming, forestry and urban development policies.
 
Please contact the conservation organisations for advice on how you can help protect British and European butterflies and their habitats. You may be able to offer practical help e.g. by monitoring butterfly populations or helping to manage nature reserves. Donations to these organisations enable them to employ ecologists and biologists. Even if you are unable to provide such help, merely having your name on the membership list can be a powerful tool for conservation organisations wishing to demonstrate the levels of support they have for their policies.

 

 
Text and images protected by Copyright © Adrian Hoskins 2007-2008, ( unless stated otherwise ) and must not be reproduced or published in part or in whole elsewhere in any form without written permission from Adrian Hoskins. Breach of copyright will be pursued by litigation.
 
Website designed, produced and owned by Adrian Hoskins