Why Evolution is True is a blog written by Jerry Coyne, centered on evolution and biology but also dealing with diverse topics like politics, culture, and cats.
Today we have photos by Dean Graetz of Australia. His captions are indented, and you can enlarge his photos by clicking on them. Aussie backyards have some cool stuff, especially the birds!
A Southern Hemisphere Backyard
Here is a sample of the inhabitants of our backyard in Canberra, Australia. Mid-March, at latitude 35°S, is a time of rapidly shortening daylength, and of harvesting the fruits of a coolish Summer. Our non-native garden shrubs (Buddleia davidii, aka ‘Butterfly Bush’) are popular attracting this new and hard to identify, visitor. We think it is a ‘Brown’, or Heteronympha species:
A large butterfly with a 10 cm wingspan, this female Orchard Swallowtail (Papilio aegeus), is always eye-catching, and always harassed by ever-present Cabbage White butterflies:
The common Meadow Argus (Junonia villida) which, after enjoying a nectar feed, often unhurriedly suns itself on our warm garden pathways, adding colour in two places:
The also common, and charmingly named, an Australian Painted Lady (Vanessa kershawi) choosing feed on a desert wildflower (Xerochrysum sp.) which we also grow as another inducement for butterflies. All the butterfly photos were shot from a 3-5m distance with zoom lenses:
A pair of aged adult Crimson Rosellas (Platycercus elegans) feeding on our neighbour’s tall shrub. These parrots are everyday sightings in Canberra gardens that are not far from surrounding native woodlands where they breed as hollow nesters:
A juvenile Crimson Rosella in the process of changing its dull green plumage to the bright reds and blues of the sexually mature adult. The coloured feather contrasting patches are so sharp that these birds enjoy the common name of ‘Patchworks’:
An adult Satin Bowerbird (Ptilonorhyncus violaceus), sex not obvious, having enjoyed a vigorous bath now eyeing the photographer. At age 7 years, a male bird will change from this khaki plumage to a brilliant blue-black glossy version, build a bower in a grassy woodland, decorate it with blue objects (same colour as its eyes), such as flowers, clothes pegs, bottle tops. The purpose is to attract, court and mate with numerous females. Hard to believe? Go here to watch:
A juvenile Kookaburra (Dacelo novaeguineae) now regularly arrives and sits patiently surveying our back yard for any living food items, such as lizards, mice, or snakes. These birds readily habituate to hand feeding by the lonely to become a mendicant friend for life:
An adult male Australian King Parrot (Alisterus scapularis) enjoying the last of an unripe pomegranate in a neighbour’s tree. The dark lower beak is staining. These are frequent visitors to Canberra at this time of the year. Being predominantly fruit eaters – their favourite is cherries – has required nearby fruit growers to cover their entire orchards with parrot (and hail) proof tents:
Close by, and part of a family flock, was this juvenile female King-Parrot, elegantly holding an unripe olive with toe and beak. They skillfully rotate each olive with their blunt tongue to flense off all the edible flesh. To us, hard green olives are unappealing, but this female ate steadily for about 15 minutes before flying off with a noticeably full crop:
Thanks to the readers who sent in photos at my behest. And today we have one of most faithful contributors, Mark Sturtevant, with some lovely photos of arthropods. Mark’s captions and IDs are indented, and you can enlarge his photos by clicking on them.
Last summer I chose to go back to Ohio to spend a few days “bugging” the local parks with a camera. I had gone late the previous summer, but this trip was done much earlier. Here are some of the critters that I had found, beginning with moths.
Here is a Tulip Tree Beauty Caterpillar (Epimecis hortaria). This will become an intricately patterned Geometrid moth with variable color patterns, as shown in the link:
A Orange-patched Smoky Moth, Pyromorpha dimidiate. Larvae feed on decaying leaves in oak woods. The moth is clearly a mimic of one the toxic Net-winged Beetles, but I don’t know if this is a case of Batesian mimicry, where the beetle is the only one with a defense, or Müllerian mimicry, where both are unpalatable and so they mimic one another:
Deep in the woods, these boldly marked moths were quite common on the low vegetation, although they seldom allowed me to get close. It is one of the Haploa Moths (which is in the Tiger Moth family), but there are perhaps three species that are similar and I can’t be sure of the exact species. I can say that it is a dead ringer for Haploa lecontei:
Next up is a bumble-bee mimicking Robberfly Laphria sp. These robust predatory flies are always interesting to watch since they can swivel their heads around to look for prey. When I found this one, it had recently hauled in a Golden-backed Snipe Fly (Chrysopilus thoracicus), and it was still struggling.
Next up are a pair of Leaf-footed Bugs, Acanthocephala sp. The female is feeding on bird poo, which is a thing that these bugs often do:
I was quite happy to see this Cocklebur Weevil,Rhodobaenus quinquepunctatus. Larvae bore into cocklebur stems and in other members of the sunflower family. I presume it is a Batesian mimic of the toxic milkweed bug:
Here is a pair of black-headed Ash Sawfly larvae, Tethida barda. Although they resemble Lepidopteran caterpillars, sawfly larvae actually grow up into stingless wasps:
There were quite a few of these Stoneflies near a river. I cannot even begin to ID these further with any confidence. The immature stages of these archaic-looking insects are aquatic:
The terrain gets quite hilly farther south in the state, and so the park trails there would send me down deep gorges. Along these trails the rocks and trees were generously festooned with large millipedes (the size of pencils) that I think belong to the Narceus americanus/annularisspecies complex. The taxonomy in the group appears to be messy and someone needs to sort them out:
Lastly, here is an interesting spider, the Humpbacked OrbweaverEustela anastera with an unknown moth as prey. I don’t remember if I’ve ever seen one before:
I’ve discussed many types of mimicry over the years, and one of them is Müllerian mimicry, in which a group of species, often not that related, come to mimic each other in appearance. In this form of mimicry, the different species are all aposematic: that is, they have bright warning coloration and obvious patterns, all evolved to deter predators. (The form of mimicry is named after the German zoologist Fritz Müller.)
The way it usually works is that a group of species, often butterflies, are subject to predation, but are also unpalatable since they ingest plant compounds that are either toxic or can be converted to toxic ones. (Determination of unpalatability may involve tests with caged birds, observation of what a butterfly eats, or even, in the case of macho biologists, eating the butterfly itself, though human taste may not mimic butterfly taste).
At any rate, each species develops aposematic patterns and colors, which lets the predator know to stay away from the butterfly. This evolves not for the genetic sake of the bird, of course, but for the butterfly, as such coloration and obvious patterns give the aposematic individual a survival advantage over others. (How this occurs, which makes the initial individual conspicuous and perhaps more likely to be caught, is somewhat of a mystery, but there are some hypothesis that have been experimentally supported.)
Once you get some species of butterflies in one area that have warning colors and patterns, natural selection can then act to make their different colors and patterns come to resemble each other. That’s because if a bunch of toxic butterflies look alike, the predator learns to avoid them more readily (it has more chances to learn). Ergo, mutations in individual butterflies of different species that lead to a convergence in their appearance will be favored, reducing the chance of individuals being eaten by birds. This can lead to quite unrelated species of butterflies adopting similar colors and patterns. (Of course, all the lookalike Müllerian species, which can be quite unrelated—even including both butterflies and day-flying moths—must live in the same area, because this convergent evolution requires reinforcement by predators that can encounter all the mimics.)
Here’s a group of six unrelated butterflies that are part of a Müllerian mimicry ring. Each species is in a different genus! Moreover, there’s a moth species in there, too! Can you spot it? (answer at bottom). The photo is courtesy of Dr. Mathieu Joron, whose webpage is here, and is used with permission.
Note that there’s no need for species to be related to each other for this to happen, as the evolution of similar color patterns happens independently in each species, all mediated by visually hunting predators. A single Müllerian mimicry ring can involve true bugs (Hemiptera), wasps, beetles, and butterflies.
And different populations of a single species, if they live in different places that have other species of aposematic butterflies, can evolve different patterns in those different places to look like the local deterrents. Here’s an example of single species (the top four species are all Heliconius numata) that mimic other aposematic species in the genus Melinaea in different areas. Remember, the top four drawings are all members of the same species, but living in different areas. Further the caption notes, “the bottom four are H. melpomene (left) and H. erato (right), which mimic each other.” Thus in the bottom four we see two cases of Müllerian mimicry.
As you see, things can get quite complicated.
Source:Repeating Patterns of Mimicry. Meyer A, PLoS Biology, Vol. 4/10/2006, e341 doi:10.1371/journal.pbio.0040341l; CC BY 2.5, via Wikimedia Commons
Butterflies in the genis Heliconius are particularly famous for showing Müllerian mimicry, and feature largely in a new paper from PNAS. What the authors were studying was not the the patterns and colors of butterflies in Müllerian mimicry rings, but mimicry of their behavior. It’s easy to see resemblance in color and pattern, but biologists have largely neglected the very real possibility that because predators can see behavior as well as appearance, mimics might evolve to resemble each other in behavior, too. This is well known in salticid “jumping spiders”, which have evolved to mimic the walking behavior of ants. (Predators hate ants since they sting and often taste bad as well.) There’s a video of an ant-mimicking salticid at the bottom.
In this paper the author studied 29 species of heliconiine butterflies and 9 ithomiine species, belonging in total to 10 mimicry rings. They wanted to see if there was, in each mimicry ring, an evolution of similar “flight behavior”, because predators can see not only how a butterfly looks, but, when it’s on the wing, how it flies. They found that there was indeed evidence in each Müllerian mimicry ring that the species had evolved similar flight behaviors. Clearly, natural selection had altered flight behaviors within a ring to make the species flap more like the other ones, with the explanation being that predators learn to avoid not only certain color patterns, but also certain ways of flying.
(Note: I am imputing bird avoidance to their learning which species are toxic, but there’s no reason why birds cannot undergo genetic evolution via selection to innately avoid certain colors and behaviors since individuals with genes tending to cause such avoidance will be favored. (This is presumably because getting sick after a meal is something that natural selection would eliminate by favoring gene forms that instinctively avoid certain appearances and behaviors.)
Read the paper by clicking on the title, or see the pdf here.
I will be brief since the analysis is complicated, involving all kinds of corrections for wing size, relatedness, habitat, and other factors; and I’ll just give the conclusions.
For several members of each species, the authors used cameras to measure three aspects of flight:
Flapping rate of the wings
“Up angle” (the angle between the wings of an individual at the top of its upstroke)
“Down angle” (likewise, but with the angle measured at the bottom of the downstroke)
And, lo and behold, when you correct for relatedness, wing size, ecological area, and other factors, the authors still found significant similarity between members of each of the ten mimicry rings they measured. This held, though, only for the first two parameters: flapping rate and up angle. There was little convergence among members in down angle, for reasons that aren’t clear (perhaps birds can’t see it as well. Here’s the authors’ tentative ad hoc explanation:
. . . down wing angles respond differently to selection exerted by predators and may be indicative of greater aerodynamic constraint on this trait. Fuller characterization of flight may provide stronger evidence of whether different components of flight are evolving under different selection pressures.
Here’s a figure from the paper showing the ten Müllerian mimicry rings they studied, each ring indicated by a different color. The groups’ conventional names are given by the key at upper left. The “tiger group” is the most famous.
(From paper): Diversity and convergence of wing patterns among the heliconiine and ithomiine taxa whose flight patterns have been measured. Background color indicates the 10 mimicry groups. Transparent (Ithomiine) 1: Ithomia salapia travella, 2: G. zavaleta; Tiger (Ithomiine) 3: Melinaea marseus phasiana, 4: Tithorea harmonia, 5: Mechanitis polymnia, 6: Melinaea menophilus zaneka, 7: Mechanitis messenoides deceptus, 8: Melinaea mothone mothone, 9: Hypothyris anastasia honesta; Tiger (Heliconiine) 10: Heliconius ismenius bouletti, 11: H. p. butleri, 12: Heliconius hecale felix, 13: Eueides isabella nicaraguensis, 14: H. pardalinus sergestus, 15: Heliconius numata bicoloratus, 16: Heliconius numata aurora, 17: Heliconius ethilla aerotome; hewitsonii-pachinus 18: H. pachinus, 19: Heliconius hewitsoni; cydno–sapho 20: Heliconius cydno chioneus, 21: Heliconus sapho sapho; Blue 22: Heliconius doris viridis blue, 23: Heliconius wallacei flavascens, 24: Heliconius leucadia pseudorhea, 25: Heliconius sara sara, Postman 26: Heliconius timareta thelxinoe, 27: Heliconius melpomene rosina, 28: H. e. favorinus, 29: Heliconius erato demophoon, 30: Heliconius melpomene amaryllis; Orange 31: Eueides lybia olympia, 32: Eueides aliphera aliphera, 33: Dione juno juno, 34: Dryadula phaetusa, 35: D. iulia; Dennis rayed 36: Heliconius elevatus pseudocupideneus, 37: Heliconius burneyi huebneri, 38: Heliconius aoede cupidensis, 39: Heliconius melpomene aglaope, 40: Heliconius doris viridis, 41: Heliconius eratosignis, 42: Heliconius demeter joroni, 43: H. e. emma; Red and white 44: H. himera; Zebra 45: H. charithonia. Butterflies images are from the Neukirchen Collection, McGuire Centre, Florida; https://www.butterfliesofamerica.com/ (Andrew Warren); http://www.sangay.eu/esdex.php/ (Jean-Claude Petit).
But it gets even nicer, for the authors also looked at flight similarity between isolated populations of the same species that were members of different mimicry rings, which, as I said above, can happen They used populations of two species, Heliconius melpomene and H. erato. Again, different populations of each species appear to have evolved similar flapping rates and up angles (but not down angles) to species of the different mimicry rings they’ve joined.
The ages of these conspecific populations can be estimated from molecular data as less than half a million years, so the flight mimicry can evolve quite rapidly. As for the other species, well, some of them are not that related, being separated by up to 70 million years from their common ancestor.
The upshot: Müllerian mimicry is often thought of as visual phenomenon because it’s mediated by visually hunting predators. And it is, but the emphasis on vision has led biologists to concentrate on easily-discerned colors and patterns (birds have color vision). Yet vision can also detect behaviors—in this case flight behavior. This isn’t really a brand-new discovery, because mimetic behavior has clearly evolved in other cases. As I said, we see Batesian mimicry in which salticid spiders, which are edible, have evolved to walk like ants that are avoided by predators (see below). But the important lesson of this paper is that biologists studying visual mimicry should not neglect to look at behavior of animals and not just their appearance.
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To end, here’s a remarkable case in which an edible jumping spider has evolved to not only look very similar to weaver ants, which are avoided by predators, but also to walk like ants. This is a case of Batesian rather than Müllerian mimicry, but it does show mimetic evolution of behavior.
Answer to question above: Which species is the moth in the first picture above? It’s Chetone sp.! (Bottom left.)
Today we’re treated to some lepidopteran photos taken by Mary Rasmussen. Her text and IDs are indented, and you can enlarge the photos by clicking on them.
American Lady and Painted Lady butterflies
Every spring American Lady butterflies (Vanessa virginiensis) are a welcome sight in my small Upper Peninsula garden. They are migratory butterflies found throughout North America:
They have a wingspan of 1.75 to 2.5 inches. Adults spend the winter in the southern U.S. and re-populate the northern areas each spring:
The butterflies lay their tiny eggs on the native Western Pearly Everlasting (Anaphalis margaritacea) plants, both in my garden and growing wild along the road:
The female butterfly lays the eggs on the cottony leaves of the Pearly Everlasting plant. Close-up of eggs with one near hatching:
American Lady caterpillar eating a Pearly Everlasting plant:
The caterpillar forms a chrysalis and its color will depend on the surrounding vegetation. On the left the chrysalis was hidden in a very green spot and on the right is a chrysalis made among dry and brown vegetation:
Newly emerged butterfly drying its wings before taking flight:
The recently emerged American Lady sips nectar. Notice the two eyespots on the hind-wing. This is an identifying feature that distinguishes this butterfly from its relative and look-alike, the Painted Lady butterfly (Vanessa cardui):
Here is a Painted Lady butterfly showing its four eyespots on the hind-wing. We have both types of butterflies in our area, and I have trouble distinguishing between them. Often taking a photo to check helps:
The American Lady also has a small white dot in the orange Patch (postmedian area) of the forewing. BugGuide has a great comparison chart:
These Painted Ladies are migrating south in late summer. You can see they lack the white dot on their forewings.
In the Eastern Hemisphere, Painted Ladies undertake a migration that is longer than the Monarch’s, flying from Sub-Saharan Africa to the Arctic regions of Europe.
I use a Nikon D500 camera with Nikon VR 105mm f/2.8G macro lens. For the butterfly egg I used a Laowa 25mm f/2.8 2.5-5X Ultra Macro lens with extension tubes.
Reader Roz sent a bunch of nice caterpillar photos, though not many of them are identified. It’s up to you, the readers, to identify them, or at least have a marvel at the larval. (And please send in your photos!)
Roz’s introduction is indented, and you can enlarge the photos by clicking on them:
The Caterpillar Lab is a New Hampshire based non-profit that breeds and collects New England caterpillars from the field. They come yearly to the Arnold Arboretum or at least they have for the years I’ve been in Boston. I saw them fall 2021. These photos are from that visit.
As for identifying them, here is what I know:
Order: Lepidoptera
Families: Saturniidae and Erebidae
While I will let readers taxonomize further, I believe the genus and species for some of the caterpillars I saw include:
Promethea Silk Moth (Callosamia promethea)
Brown-hooded Owlet (Cucullia convexipennis)
Hickory Horned Devil, the larva of the Regal Moth (Citheronia regalis), which I got to let crawl on my hand and arm.
The Caterpillar Lab has a lovely Facebook page for those who may be interested.
JAC: The first two are clearly mimics of bird droppings.
Today’s photos come from our intrepid regular, Mark Sturtevant. Mark’s text and IDs are indented, and you can enlarge his photos by clicking on them:
In a recent post, I shared some pictures of arthropods taken the previous summer on a trip to my home state of Iowa. Here are more pictures that came out of that trip.
To begin, readers may recall that the previous set included pictures of a large wolf spider (Tigrosa aspersa). To jog your memory, here is another picture of her:
One thing about wolf spiders is that their eyes produce a lot of eyeshine when you put a light on them at night. Like cats, these nocturnal spiders have a reflective layer in their eyes, and so a simple walk outside with a flashlight can reveal many glowing eyes of these spiders. Strangely, the internet does not offer very detailed pictures of this phenomenon, so I decided to take the spider home to give the internet a real close look at wolf spider eyeshine. Back at home, I put her in a bucket of sand that was topped with a glass box that I had made from thin picture glass. The photographs below were taken from long exposures with a pinhole flashlight, in a dark basement, while the camera was fixed on a tripod. Getting eyeshine from a distance is super easy. But I found that when working up close, the angle between the light and the camera lens had to be very exact to get much of anything.
I soon learned that she liked to hide in a burrow, and so here she is glaring up at me from a tunnel that I made for her. The radiant pattern of light is a cool camera artifact that lights and reflections can have when a lens aperture is stopped way down. I am here reminded of Shelob, the giant spider in The Lord of the Rings – “an evil thing in spider form”.
The remaining pictures were taken while still back in Iowa. All but the first were taken over a couple nights while staking out my brothers’ porch lights. The family is quite accustomed to this sort of thing, of course.
