The Lepidoptera Log - by Steve Woodhall
That's a Plain Tiger!...?
or is it...
Watching butterflies in the field and photographing them is a rewarding hobby that more people are taking up every day.
But frustration may creep in with the realisation that many of them look SO similar to one another. For some species it’s simply because they are closely related to one another, like the Jokers. But with others, the similar ones might come from a totally different group of butterflies – a different subfamily, or even family. There are even some moths that look like butterflies!
The three types (or species) above are probably the ones that people confuse the most often.
Why do they so often look alike?
Some butterflies, like the Plain Tiger, Danaus chrysippus carry in their bodies chemicals that are bad tasting, or even poisonous. Because many predators hunt by sight, they have developed warning (or aposematic) colouration that predators learn to avoid because they associate it with an unpleasant experience. Such species are known as distasteful. The orange-black-and-white combination is aposematic.
Some other butterflies (or moths) have evolved to carry the same aposematic markings but are NOT distasteful, in fact predators may find them palatable (edible and good). An example of this is the female of the Common Diadem Hypolimnas misippus. She looks very like a Plain Tiger but there are certain differences you can see if you look closely. This is known as mimicry, because the palatable species mimic the unpalatable or distasteful ones.
There’s another form of mimicry in which unpalatable or distasteful species evolve to look alike. The butterfly shown above with the spotted wings is the White-barred Telchinia, Telchinia encedon. This form of mimicry, in which unpalatable species look similar to one another, is known as Müllerian mimicry. This is distinct from the Batesian mimicry shown by the Common Diadem female, in which unpalatable species look alike.
Practically, Batesian mimicry tends to dilute the effect of the distasteful species’ effect on predators. The more Batesian mimics there are around, the less the chance a predator (usually a bird) has of having a nasty experience. Fewer predators learn the lesson and the result is that more of the unpalatable ones get attacked. They often have other defences, like a tough body that can withstand injury, but the visual aspect gets diluted.
Müllerian mimicry works in the opposite direction. The more Müllerian mimics there are, the less the effect of the aposematism gets diluted. The chances of a predator associating the colour pattern with a nasty experience increases, and the books are balanced!
What we find is that certain colour patterns become embedded in the population. Several Müllerian and Batesian mimics share a common aposematic colour pattern, and this becomes known as a mimicry ring. Such rings are common in the tropics where there are many butterfly and moth species. The orange-black-and-white ring is one of several. Others are (for example) yellow with black spots or pied (black-and-white).
Mimicry rings can even spread out into other groups of insects like wasps or grasshoppers.
This can make life very tough for YOU, the observer wishing to know exactly what they are looking at. It’s made worse because the distasteful ones often have a slow lackadaisical flight pattern (as if they knew they aren’t likely to get chased) and of course the palatable ones tend to mimic that too!
Fortunately, there are subtle visual cues you can watch out for that allow you to tell them apart. So read on…
Common Diadem ♀
Hypolimnas misippus
African Plain Tiger ♀
Danaus chrysippus orientis
Let’s put a lady Diadem next to a Plain Tiger. They look pretty similar, don’t they? Enough to fool many people, and birds as well.
If you look carefully you can tell the difference between them.
First, their antennae (green arrows). Some people call them ‘feelers’ but they are more to do with their sense of smell than touch.
The Diadem (left) has straight antennae whereas Plain Tiger has droopy antennae.
Then the hind wing margins (blue arrows). The Diadem’s hind wing edges are more strongly scalloped and have two or more rows of pale marks all along the margin. Plain Tiger has smoother hind wing margins, doesn’t have a complete double row of marks, and the ones along the outer edge are broken in two
Forewing margins (white arrows): The Diadem’s forewing has a double or triple row of pale marks going all the way to the wingtip; Plain Tiger’s forewing pale marginal marks are only double in a couple of places and never triple – and there’s a gap below the wingtip.
Ignore that extra white spot on this Plain Tiger’s forewing (red arrow) – not all of them have this.
Common Diadem ♀
Hypolimnas misippus
African Plain Tiger ♀
Danaus chrysippus orientis
The Common Diadem’s underside is on closer inspection different to that of a Plain Tiger. The scalloped versus smooth wing edges are the same (white and blue arrows). The edge of the Diadem’s forewing underside, like the upperside, has three rows of spots all the way to the tip.
Underneath, the Plain Tiger’s forewing has white edge spots that go all the way to the tip but they are double not triple and the ones on the margin are split in two. The Diadem’s hindwing underside has a triple row of pale edge spots and an inner row just for good measure. The Plain Tiger’s hindwing underside edge only has a double row of spots and the inner ones are more rounded.
Their thorax (chest – red arrows) shows more differences. The Diadem’s is reddish below. The Plain Tiger’s thorax is black with white spots all the way down.
The labial palpi (a pair of sense organs on the front of the head – green arrows) show more differences. The Diadem’s labial palpi are white from base to tip; the Plain Tiger’s palpi are black with three white dots.
African Plain Tiger ♂
Danaus chrysippus orientis
African Plain Tiger ♂
Danaus chrysippus orientis
African Plain Tiger ♀
Danaus chrysippus orientis
And how to tell a male from a female Plain Tiger? Well it isn’t as obvious as the difference between a male and a female Diadem, where the male looks nothing like the female!
A male Plain Tiger has a big extra spot on his hindwing, pointed to by the red arrow in the middle picture above. On the underside it’s black with a white centre, on the upperside (left) it’s plain black (also shown by a red arrow). It’s actually a pouch where he keeps his scent powder, or androconia, which he uses to excite the female.
Mocker Swallowtail ♀
Papilio dardanus cenea form trophonius
Mocker Swallowtail ♂
Papilio dardanus cenea
There are a few other butterflies that mimic the Plain Tiger. The female Mocker Swallowtail Papilio dardanus form trophonius (left) is one. She is more distantly related to the Plain Tiger than the Diadem – she’s from the Papilionidae, a Swallowtail. Like the Diadem she looks nothing like the male (right)! You can tell her from the Common Diadem and the Plain Tiger by:
- Her antennae are the typical Swallowtail type, upcurved at the end (red arrow)
- The white patch at the tip of her forewings is a blotch not a band (blue arrow)
- There are no white spots along her forewing upperside margin (green arrow)
- There is only one row of spots along her hindwing upperside edge and they aren’t any right on the margin as the other butterflies have (white arrow)
You might also notice that she has six walking legs (not visible here) that sets her apart from the Nymphalidae, which have four (both Common Diadem and Plain Tiger are in the Nymphalidae). Also her abdomen is pale buff with a dark stripe running down the back, between a double row of dark spots.
The female is the reason this butterfly is called the ‘Mocker Swallowtail’. ‘Mocker’ is another word for a creature that mimics others. ‘Mockingbird’ is another example of how the word is used.
This is not the only form of the female Mocker Swallowtail. There are others that ‘mock’ or ‘mimic’ other distasteful relatives of the Plain Tiger.
White-barred Telchinia ♂
Telchinia encedon encedon form fulva
White-barred Telchinia ♀
Telchinia encedon encedon form lycioides
This is another mimic, the White-barred Telchinia, Telchinia encedon encedon. It’s smaller than the other butterflies and it shares the Plain Tiger’s slow and lackadaisical flight pattern, as if it knew not many predators would want to eat it. It’s the orange form fulva (left) that mimics the Plain Tiger. It has other colour forms like form lycioides (right) that have similar markings but a very different colour to the Plain Tiger. The colour difference has nothing to do with the fact it’s a female. Other females might have the fulva colour scheme.
Unlike the females of Common Diadem and Mocker Swallowtail this one is NOT palatable. It’s one of the Heliconian butterflies that taste just as nasty as Plain Tigers. Like them it’s one of the Nymphalidae and has only four walking legs.
At first glance it looks very like the Plain Tiger and its slow flight can make you think it is one, but there are some important differences that make it easy to tell it apart.
- It has row of black spots in the middle of its forewings (red arrow)
- It has many black spots on the hindwings – and these are on the underside as well (green arrow)
- And they never have any white spots or stripes on the margin of the forewing (blue arrow) OR the hindwing (white arrow).
This is Müllerian mimicry where distasteful species tend to look alike.