Pale Clouded Yellow (Colias hyale)
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2018 photographs highlighted in green. Click on any photograph to go to an enlarged picture, or simply scroll down the page.
Hyale and the Berger's Clouded Yellow (C. alfacariensis) are almost impossible to tell apart by external characteristics. It is probably true that any individual that appears bright lemon yellow is almost certainly (male) alfacariensis, but the reverse is not necessarily true, and this pointer may be subject to considerable regional and altitude variation.
The most reliable (if any are) external characteristic is that alfacariensis has a slightly more rounded forewing outer margin and hyale is straighter with a more pointed wing tip (apex). If either the margin or apex are rounded, it is alfacariensis, but I'm not sure the converse is always true. The degree of curvature seems to me to be very variable for alfacariensis, some being extremely rounded and others either quite straight-edged and/or quite pointed at the apex. Photographs can be misleading if not exactly at 90 degrees to the plane of the insect.
In 2012 I studied the hyale and alfacariensis archives of the London Natural History Museum and concluded that there was little difference in the apex pointedness and the margin straightness between the two species, maybe the evidence just leaning toward the pointers as outlined above, but hardly conclusive. This always assumes that the NHM archives are correctly identified which one would expect, although the historical confusion of these two species may come into play here.
The uph discal spots are a different colour, but this doesn’t help (unless you are prepared to catch and examine specimens, which I am not) as they do not settle with open wings, although occasionally a quick photograph of courtship might catch this (I got lucky in 2015 - see 38539). The uph discoidal spot is said to be bright orange in alfacariensis and pale orange in hyale. Also, the alfacariensis upf basal shading is said to be narrow and extending along the lower margin, whereas the shading of hyale is broader and extends further upward. The illustration of this last point really needs a drawing to show the difference, and the best example seems to be in Lafranchis' ID book.
It is easy to separate them in Var: hyale does not occur in Var, according to Lafranchis, and I have not seen any concrete evidence to cause me to disbelieve this. I did, however, look closely at the forewing margins and apices of specimens in northern Var in 2008 and some are decidedly less rounded than those seen in the south of the département. Northern Var is a comparative wilderness compared to the relatively highly populated south of Var (the A8 autoroute makes a good dividing line), and I suspect somewhat under-recorded.
The larvae of these two species are different and in a recent study by Tim Cowles has bred them both (and the Clouded Yellow (C. crocea)) from ova, comparing the larvae at each instar. The larval hostplants are different and the only completely reliable method of differentiating them (without capture and examination) is to observe the female egg-laying and identify the plant; hyale uses White Clover (Trifolium repens) and Lucerne (Medicago sativa) whereas alfacariensis uses Horseshoe Vetch (Hippocrepis comosa) (as is commonly the case in Var) and, locally, Crown Vetch (Coronilla varia).
Tim Cowles' study can be found here:
|38539||F||this female is somewhat problematical. Is it hyale? The uph discoidal spot is clearly quite pale, but is this a result of ageing? The upf basal shading seems also seems to be quite extensive and thus ticking the box for hyale. I have a clearer shot of the male that is attending, and the uph discoidal spot seems more pale orange than bright orange. However, the latest work by Lafranchis, La Vie des Papillons (http://diatheo.weebly.com/la-vie-des-papillons.html) shows hyale as not occurring in this part of Lot (this may not mean a lot - pun intended - as the distribution of hyale is shown as a series of small colonies outside its main domain of eastern central France, suggesting that no-one really knows), whereas it does show alfacariensis extensively across most of Lot. It may be significant that 38539 appears to be on Lucerne (Medicago sativa), the larval hostplant, and this is often the telling factor where females are concerned, and probably swings the balance in favour of hyale. It occurs to me now that maybe I should have observed it for longer, when it might have been kind enough to start egg-laying on this plant.||320|
I believe this to be a male hyale largely on the grounds of the forewing shape and the rather heavily dusted unh. It was seen in the Hautes-Alpes where hyale is known to occur, albeit a few km from the nearest recorded sighting. However, alfacariensis is more widespread in the Hautes-Alpes and has an upper altitude limit of 2400m according to Lafranchis, whereas hyale is limited to 2000m although these ranges should not be interpreted rigidly.
I believe this is a male hyale as the forewing outer margin is quite straight and the apex is maybe just about pointed enough for hyale. The ground colour is a pale lemon yellow indicating hyale. It was seen in northern Italy, where hyale does occur.
I believe this could be a male hyale because of the colouring and the evident straight margin and pointed wingtip. However, the butterfly was in motion, so this may not be conclusive.
|27908||M||this male was flying in the département of Côte-d'Or in central Eastern France where hyale does occur. I felt that the quite-clearly straight forewing margin and quite accentuated pointed apex would be good indicators of hyale, coupled with the rather pale yellow colouring (at least compared with the bright lemon yellow specimens prevalent in Var), but the opinion of at least one expert is that it is alfacariensis. However, if the straight margin and pointed apex do NOT indicate hyale, why are these characteristics quoted in identification books?||320|