Thursday 14 June 2012

East African Butterfly families and corrupt, singing caterpillars

Citrus Swallowtail, Papilio demodocus, is very common in Tanzania
We're rarely short of butterflies in Tanzania, but they're a sadly overlooked group. Except, perhaps, when they're swarming by the million as earlier this year most people will, at best, only notice a few in passing. For a hugely diverse group (there are over 18,000 described species), they fall into a relatively small number of readily recognisable families. Unfortunately, all the nice identification books are out of print (and wickedly expensive to buy on ebay!) for East Africa, but there are some resources out there that will help once you've figured out the families. The relationships between the families have recently been the subject of some serious work. It turns out that the family relationship were rather difficult to pin down because they all evolved relatively quickly in the Cretaceous (yes, dinosaur time, 100 - 75 Million Year Ago). But our best guess at the moment sorts them into 4 main groups split into a total of 26ish main family groups, only a few of which are at all diverse. So it's not too hard to get to grips with the main families, and the main change to the traditional taxonomy, if you've been into that, is that the big group Papilionoidea is actually two, rather distantly related groups. I'm going to describe some of the common families here (together with some of my favourite stories about them - yes, including corrupt, singing caterpillars) and hopefully will be able to show how the various families fit together at the end. So, here goes...

Graphium antheus, the Larger Striped Swordtail. Note 6 legs
Papilio orphidicephalus, the Emperor Swallowtail
Starting at the bottom of the new taxonomy (the first major split from the butterfly clade) we've got the Papilionidae, the swallowtail family. We've got lots of flavours of these here, from the standard yellowish ones like the Citrus Swallowtail which is virtually everywhere, to the nice Graphium genus of greenish blue ones. They're typically big species, often with long tails, but it's the caterpillars that are most distinctive - often brightly coloured and striped, they have a special forked organ behind the head that distinguished the group from all other butterfly groups. Most interesting thing about this group? Check the mocker swallowtail story in the caption...
Papilio dardanus, the Mocker Swallowtail. This is probably a male,
but the females come in at least 14 different forms, as mimics
of toxic species, but also as mimics of the male. Mimics of toxic species escape predation,
mimics of males escape sexual harrassment!
They're fascinating things...

Coeliades anchises, the One-pip Policeman (check the single dot on
the white triangle!) is not a typical skipper, but still shows curved antennae
Pardaleodes incerta shows the strange resting wing position of skippers
Next off is the Hesperiidae, or skipper family. If the swallowtails are the birds of paradise of the butterfly world, this family are the little brown jobs... They are a really big group and readily identified: all have curved antennae, instead of straight-ended clubs in all other families. They're usually small winged and big bodied, looking rather more like moths than other butterflies, and they're pretty unusual too in the way their wings are held, often folded in strange ways when resting. A hugely diverse family, many of these skippers are highly host-plant specific and often show strong evidence for co-evolution with their hosts.

The Flat, Celaenorrhinus galenus often sits underneath leaves
perches on the undersides of leaves and shows curved antennae tips
Colotis evagore antigone, the Tiny Orange-tip
Raffray's White, Belenois raffrayi is a typical white
Then we're into the whites, or family Pieridae. As the common name suggests, this is the group that contains most of those very obvious white butterflies that are major agricultural pests, and that here in East Africa form the huge eruptions involving many millions of animals from time to time, like the one in February that everyone here helped document. However, they're not all white and not all white butterflies are, in fact, Pierids, so to separate them from the other groups it's easy to see they're not skippers and then look at the  legs. All six should be normal length and, if you look really closely at the feet, the final claw is split into two (though most of the time it's enough to see that all the legs are long). As well as their major importance as agricultural pests and the phenomenal movements we get around here, it's interesting to note that whilst they are all basically pale coloured, some genera - such as Colias - have patterns only visible to us under UV light, reminding us that many insects have the ability to see UV.

Not all whites are white!
Belenois thysa, the False Dotted Border

I love the Crimson-tip Colotis danae

But I thought insects had 6 legs?! Members of the Nymphalidae
like this African Monarch only have four big legs.
African Monarch Danaus chryippus. Check the diadem below!
The final family is a monster group called the Brush-footed butterflies, the Nymphalidae. This family all has a much shorter front pair of legs, making them easily identifiable as a group. However, there are so many, and so many interesting members of this family, that we normally separate them into a number of different subfamilies which is where we'll look at some detail. First up, subfamily Danainae, the Milkweed butterflies. Not a big group, these are the large, brightly coloured and toxic Monarchs. As the common name suggests, the larvae all feed on the milkweed family, a toxic plant group, which makes the caterpillars and then adult animals toxic to most birds. They would be very easy to identify, as obviously orange, black and white - if it weren't for the fact that other species have evolved almost identical patterns to gain protection from predators!

Charaxes candiope, the Green-veined Charaxes shows typical
two tails, four legs and well marked underwings.
Charaxes varanes, the Pearl Charaxes only has one tail
Danaids form a group with two other common subfamilies we get out here: Charaxinae and Satyrinae. The Charaxes or Emperor butterflies usually have two tails and typically fly very fast - some have been clocked at over 40kmh in still air! Most are fairly strongly marked on the underwing, and they can be rather large. The caterpillars are easy to identify, as they all have flattened heads and strange horns, for the adults a combination of tails and much reduced first pair of legs is usually good enough. The satyrs or browns are anther big group. However, they're usually easy to overlook, sine they're mostly rather non-descript brownish species, ad the best things to look for are the eye spots - usually several. And when you look close up, these butterflies are really rather pretty too!

Bicyclus campinus is a typical Satyr: brown with lots of eye spots.
Neptis serena, the Serene Sailor is typical of the genus.
Subfamily Limenitidinae is commonly called the admiral family, but that's rather confusing here, since the African Admirals belong to a different subfamily all together. The guineafowl butterfly is probably the most often noticed species in this subfamily, but I've not got a picture! There are some really beauties here though, including the fabulous forester species, which are relatively common, particularly in coastal forests. And look around elsewhere and you'll soon start to notice sailors too - very territorial species that often perch on top of vegetation then sail about in loop before coming back to the same spot.

Bematistes aganice montana, The Wanderer, has recently
been split from Acraea and shows the typical long wings.
Acraea caldarena, The Black-tipped Acraea
Then comes the Heliconiinae or Longwings, which is actually a pretty good name for what is a mainly tropical family - they all look rather long and thin-winged, though they come in a huge range of colours. There's a beautiful one in in my garden here with black, yellow and orange wings that never stops for a photo, but the commonest group you'll see are the Acraea. This 'genus' is about to be split into lots of differet groups as it's recognised that they're not all similar at all, but for now it's pretty easy. Also in this group are some of the African fritillaries.
Mating Broad-bordered Acraea, Acraea anemosa
Phalanta eurytis, The Forest Leopard Fritillary
Junonia oenone, the Dark Blue Pansy, typical of Nymphalinae
One of my favourite: Euphaedra neophron, the Golden-banded Forester
Strangely, what's one of the most obvious and prettiest of the subfamilies, the Nymphalinae, doesn't seem to have a commonly used English name at all. But it's one you'll certainly be familiar with, as it includes the pansies that are everywhere in the savanna and the Diadem (also called the mimic or the Danaid Eggfly) that I hope everyone knows because the female is a near perfect mimic of the African monarch. It also includes some of the butterflies that do true migrations (not just eruptions, but regular 'there and back again' trips, such as the painted lady, and our African admirals. This group is one that I tend to identify mainly because they're obviously Nymphalids (with only four long legs), but not fitting any of the other subfamilies! Though as there are a number of other, much smaller subfamilies I'm not listing at all, that's probably not the best way to go about things and if anyone has any better advice, please let me know!

Mating Diadems, Hypolimnus missipus. The female
(above) is an excellent mimic of the African Monarch
Female Diadem laying eggs - compare spots with Monarch!
Junonia hierta, the Yellow Pansy is very common

Junonia natalica, the Brown Pansy
Male Diadem Hypolimnus misippus: completely different to female!

Vanessa cardui, the Painted Lady is almost global in
distribution and a true migrant, some moving between Africa and Europe
Lampides boeticus, the Long-tailed Blue is very widespread
Zezeeria knysna, the African Grass Blue is actually tiny!
Finally, we have the huge subfamily Lycaeninae, the blues or gossamer-winged butterflies. This is a massive group of mainly small blue and brownish species that are incredibly difficult to identify. They're often very pretty though and most of them (75%), when caterpillars, have some fascinating relationships with ants. Many ants protect trees from other insects in return for homes or access to nectar, etc. It's pretty good for the tree. But many blues effectively bribe the ants to turning a blind eye to them by the caterpillars also producing sugared water on demand (the ants can milk them), whilst allowing them to feed on the plant. In fact, it's better than that for the caterpillars, because the ants might even carry them down to the nest to look after them at night, and bring them back during the day, and they provide the same defence against predatory wasps that the plant gets against other herbivores! Experiments show that the caterpillars on ant-defended plants are much, much more likely to survive, and my most amazing fact of the week is that apparently the pupae of some species 'sing' to attract the ants to them! They can apparently make sounds with a comb-like structure on a hard flat piece within the abdomen, and have three signals they make to attract the ants to take them to the nest and protect them. Of course, some caterpillars have gone one step further, not content simply with bribing the ants to let them eat the plant, they then turn on the ants themselves and have turned predatory, feeding on the ant larvae but protected by chemical signals from being detected - until they emerge as adults, when they have to make a very rapid escape from the nest! Pretty remarkable group, the blues...

Oh, and if you got this far you're obviously as fascinated as me by invertebrates, so if you're in Arusha come to talk at the Coffee Lodge on Monday night, 18th June, on Ants, by Dr. Kate Parr. It's going to be great and the first in a series organised the the newly formed Society for Interpretive Guides. Hurrah!

Main reference:
Heikkila, M., Kaila, L., Mutanen, M., Pena, C., & Wahlberg, N. (2011). Cretaceous origin and repeated tertiary diversification of the redefined butterflies Proceedings of the Royal Society B: Biological Sciences, 279 (1731), 1093-1099 DOI: 10.1098/rspb.2011.1430

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