What's that white?

By Steve Goddard

Hands up all those who never have

problems in identifying 'Whites' in flight or at a distance. Do I see no hands? Well,

that's hardly surprising because most of us seem to have trouble at one time or

another in getting to grips with 'Whites'

on the wing or when they are not so closeup. After all they are white aren't they?

And, in researching this article I have to

say that there is no easy solution but there are some factors which seem to offer up some help.

At fairly close range the Large White is usually distinguished by its larger size particularly, the larger females. However, what about distant Whites (and small Large Whites)? Here, judgement of size oflone individuals is not always as easy as it might seem. In these situations it is generally only best achieved when comparison can be made with other Whites at the same time but even then binocular users should beware of the potentially misleading effects of 'size illusion' when the farther of two objects looks larger than it really is in comparison with the nearer object!. Judging size* is probably the greatest difficulty we have when encountering a single distant White because

Large White by Douglas Hammersley

accurate assessment of size is beyond the capability of the human eye. We may think we are judging size all the time but all that is really happening is that we know the size of a butterfly the instant it is identified. In effect, the process is no more than: "It's a Large White, so it's Large White sized". In such circumstances, it is best to ignore apparent size and instead to rely on objective differences such as colour markings. To confirm the identification of a Large White concentrate on the black marking at the apex of the forewing which should be visible at a reasonable range particularly with binoculars. This black or grey/black feature is broad and bold and extends almost half-way along the outer forewing margin. By comparison, in the Small White this key feature will be indistinct or absent. In the Green-veined White and female Orange-tip the black mark in this region (bolder in Orange-tip than Green-veined White) are no where near so broad or bold and it certainly does not continue along the outer margin. Of course, another potential problem at distance with the naked eye could be the Brimstone when any 'black'might not be so obvious! The shade of white should also be useful. Large White and Small White have a creamy tinge. The Green-veined White appears pale greyish whilst the female Orange-tip is quite translucent appearing pearly white, tinged with green. The flight of the butterflies can provide other clues as to their identity. Both the Large White and Small White are strong fliers since both migrate across the English Channel and they tend to have a much more direct flight than the weaker, fluttering style of the Green-veined White. The Orange-tip flits quite slowly except when egg-laying when it flies more directly between foodplants. Having said this, all the Whites could engage in similar flight at one time or another but on balance the Large White is likely to display a stronger, more loosely fluttering flight than the Small White which although having a fluttering appearance is not so loose (possibly due to wing size?). The Green-veined White whilst again having a similar fluttering flight to the Small White, it is generally weaker in manner. The flight of the female Orange-tip is very similar to both Small White and Greenveined White so the pearly white and greener impression will need to be looked for. Flight differences are rather subtle but the best way is to try out these perceptions in the field. I said at the beginning that there is no easy solution! The flight period of the female Orange-tip will also help in that it is not generally seen after the end of June. Nectaring preferences can provide further clues. Small Whites prefer white or pale flowers, while Large and Green-veined Whites are usually attracted to purple and yellow flowers such as thistle, bluebells, ragwort and dandelion. Orange-tips favour their larval food-plants such as cuckooflower or garlic mustard but will visit others. The location of a butterfly is also a useful pointer. Although all Whites have fairly widespread habitat preferences, the Green-veined White and Orange-tip are most often found in shadier, damper areas along hedges, ditches, woodland edge and water-sides where their food-plants grow. However, to be certain of identification you must obtain a good view of the butterfly. Close up, all Whites should give up their identification quite easily. One useful identification feature of the Greenveined White which does not seem to come out in all field guides are the grey triangular ends to the veins on the upper forewings. This can be most helpful when the 'greenveined' hindwing is not visible.

In summary, when watching Whites in flight or from a distance, beware of size judgement in not so close 'large' or 'small' species of White. Do try to focus on the area of 'black' on the forewing apex. Take note of the shade of white as well as the manner of flight. Also check out the nectaring preferences as well as the butterfly location. Best of luck and please write to the editor to let everyone know how these notes may have helped or otherwise! Any identification methods which you may already use would also be most welcome.

*Birdwatcher's among you may wish to remind yourselves of this fascinating subject by referring to 'Birding World, volume 2, number 4, pi 32.' This forms part of the excellent series presented in this publication - ' The New Approach to Identification' by Killian Mullamey and the late Peter Grant. It was also available in a separate booklet published in 1989.