There is a group of fritillaries – including the Heath (M. athalia), Provencal (M. dejone), False Heath (Melitaea diamina), as well as the scarcer Nickerl's (M. aurelia) and the Alpine Grisons (M. varia), which can all look very similar and are quite difficult to tell apart, especially with so many subspecies and local variants. The key differentiators for parthenoides are that the upf linear discal mark in s1b is largely oblique for the male (not necessarily the female) parthenoides c.f. athalia and varia, and the uph discal line is missing or incomplete producing a “gap” where the black lines are usually (but not always) complete in athalia. The male is bright orange and the female is larger and a little deeper orange sometimes with some colour variation between the bands. There is also a dark form of the female, as its name suggests and with a slight suffusion; to add confusion, there is also a dark form of the female varia.

The forewings of the male often seem (to me at least) to be very wide in comparison to the hindwings. The textbooks, T&L in particular, focus on differentiating parthenoides from varia, and the illustrations or the male in particular are very similar; in my experience, parthenoides and varia look quite different and neither really resemble the T&L illustrations. The key feature is, as mentioned earlier, the upf discal mark in s1b.

The word "Meadow" in the name is rather misleading as, although it does occur in lowland areas, it is equally at home at (very) high altitudes. Even though there are meadows at high altitudes, the name rather conjures up images of a low altitude species.

In the new European taxonomy, the Mellicta fritillaries are now grouped with the Melitaea genus, so this species now has the scientific name Melitaea parthenoides.

observations

classic male parthenoides, although nothing like the illustration in T&L. The constant orange colouring, the heavily oblique upf s1 discal mark are sure pointers, and the extended forewing shape is something that I tend to associate only with this species.

a male. The upf s1 discal mark is quite heavy and not totally straight, but is clearly oblique. The uph discal line is entirely missing, although I have seen this in athalia. One forewing is slightly folded back, which I have noted on parthenoides and not on many of its cousins. Is it characteristic?  

another classic male parthenoides, the s1b oblique line is a little curled at the top edge but most of it is clearly oblique. There is a slight colour contrast in the uph bands with the submarginal band being a rather yucky orange that seems to occur in parthenoides and no other Mellicta species.

a female of the dark form of parthenoides (rather than varia), I believe. It is difficult to tell for sure because of the wear. The altitude is rather lower than would be normal for varia.

I believe this to be a female parthenoides of the nominate form, rather than the dark form of 21259. I could not be 100% certain that this is nominate parthenoides as the nominate form of the female varia is very similar. I did, however, get a photo of the underside, on which my ID is largely based.  

could this be the dark form of the female varia? It was seen north of Digne in the first week of June at around 1200m, probably a bit early for varia and at the lower end (or even below the lower end) of the varia altitude range, and at the western end of its range. These factors make it rather unlikely to be varia. At the time, I had never seen a female varia but it did seem to match the illustrations in T&L and in both Lafranchis books. The upf discal mark in s1b seems to match the characteristic varia mark.

a male, dining on a sheep "crotte" at high altitude in the Alpes. The heavy black uhf markings and pronounced marginal lunules tend to query parthenoides, but the unh lunules are shallow and the post-discal series of white spots are quite rounded, both of which point to parthenoides, as I understand it. I also have a photo of the upperside which seems to confirm parthenoides.