The Lepidoptera Log - by Steve Woodhall
The 'Jokers'
Two very similar butterflies - how to tell them apart?
Some butterfly species (and many moths) are incredibly similar to one another. Some to an extent that you need a microscope or a DNA sequencer to tell them apart! We’ll look at some of those in a future blog post. For now, there are some that, with a little patience and attention to detail, can be identified by getting to know their patterns.
The ‘Jokers’ (genus Byblia) are two members of the Nymphalidae (Brush-foots), subfamily Biblidinae. Their upper sides appear almost identical in appearance apart from a simple clue that lets you tell them apart. You can probably see it by looking at the above images. One of them is the ‘Spotted Joker’ (Byblia ilithyia) and the other is the ‘African Joker’ (Byblia anvatara acheloia). Can you ‘spot’ the difference?
Eastern African Joker, Byblia anvatara acheloia is a common butterfly found across the warmer eastern and northern side of South Africa, but not in the cooler highveld areas. It’s found all over sub-Saharan Africa and Madagascar as well as the Arabian peninsula and the Comores. There are west African and Madagascan subspecies but their markings are basically similar. Its caterpillars feed on a wide range of wild hops and nettles in the plant family Euphorbiaceae as well as the Castor Oil plant Ricinus communis.
Spotted Joker, Byblia ilithyia, is a lot more widespread than the African Joker. The two species may be found flying together. It’s found across all of northern and eastern South Africa (including the cooler and more arid areas), and the same areas across Africa as the African Joker but not in Madagascar. In addition, it’s found on the Cape Verde islands and across Asia to Pakistan, southern India and the dry zone of Sri Lanka. Its caterpillars use a similar range of host plants to the African Joker. There is only one subspecies.
African Joker ♂
Byblia anvatara acheloia
Spotted Joker ♂
Byblia ilithyia
The Spotted Joker (right) has a row of black spots in the middle (the correct term is discal) area of the hindwing, where the African Joker (left) has none.
And the leading edge of the African Joker’s forewing (called the costa) has a broader dark band along the margin that stretches further towards the outer edge of the wing than the Spotted Joker.
The red arrows point to these differences. These are both males. What about the females?
African Joker ♀
Byblia anvatara acheloia
Spotted Joker ♀
Byblia ilithyia
Like many butterflies the Jokers show what we call sexual dimorphism. The females’ upper sides are a duller orange colour than the males’ and have dark shadows over some of the orange.
That’s not a consistent feature, it varies according to the season. Wet season form Jokers generally have more extensive dark markings than those in the dry season. However, the hindwing spots and dark forewing costal margin remain the difference between the two species regardless of sex or season.
There are only two species of Byblia Joker butterflies in the world, so fortunately there’s little else to confuse them with. The upper side differences are fairly clear cut and because they often oblige by posing with wings open, it’s not too hard to tell them apart – their names give it away once you know about the spots.
But people struggle with the undersides, so let’s look at those.
African Joker ♂
Byblia anvatara acheloia form similata
Spotted Joker ♂
Byblia ilithyia form ilithyia
These are both wet-season (or summer) form Jokers. The African Joker’s summer form is form similata. Spotted Joker’s summer form is form ilithyia.
With all those spots and squiggles it can get VERY confusing. The main differences (there are three) can be seen on the undersides:
One is that the submarginal row of marks – green arrows – that just means ‘below the margin’ – in African Joker are orange fading to cream basally (that means towards the base of the wing, or the butterfly’s body)
On Spotted Joker those marks are clearly divided in two. Basally (the side towards the body) they are half white, and distally (that means distal to the body, or furthest from it) they are brownish orange.
The second (red arrows) is that the postdiscal (that means ‘outside the middle’ – remember the discal spots on the Spotted Joker upperside – row of marks is orange on the African Joker.
On Spotted Joker those marks are tan-brown and larger.
The third (blue arrows) is that the basal half of the hindwing underside on African Joker is orange with subtle beige shading in the discal and basal area.
Spotted Joker is tan-brown with definite cream-white discal and basal bands. The effect is of a warm tan underside hindwing with three white bands crossing it.
What happens in the dry season?
African Joker ♂
Byblia anvatara acheloia form anvatara
Spotted Joker ♂
Byblia ilithyia form badiata
In the dry or winter season the undersides go DARK. And it gets more confusing!
African Joker’s dry season form is anvatara (left); Spotted Joker’s dry season form is badiata (right).
And both have three white bands crossing a chocolate-brown hindwing underside. How to tell them apart?
The marginal band is one way to tell them apart (white arrows). African Joker form anvatara has chocolate-brown all the way to the edge of the hindwing. Spotted Joker form badiata has a thin white marginal band (so in fact it has four white bands on the hindwing) and it has this on the forewing underside too.
The submarginal band is the same in both species – a row of rounded spots.
The other main differences are seen in the median (middle, remember) bands shown by the green arrows. African Joker’s median band is broken into spots by veins lined in chocolate-brown.
Spotted Joker’s median band is continuous, and it has a row of black spots basal to it. And its basal band (blue arrow) is similar. It really is a ‘Spotted Joker’!
Intermediates between the summer and winter forms aren’t rare. You’re likely to see summer forms of both species with the tan-coloured areas of the hindwing undersides invaded by some chocolate-brown, like this intermediate form African Joker..
African Joker ♂
Byblia anvatara acheloia form intermedia