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.
This is a waved albatross (Phoebastria irrorata) heading in for a landing.
Albatross courtship.
Speaking of courtship, I think that’s also what these blue footed boobies (Sula nebouxii) are up to.
An aside: Watching a “changing of the guard” at some palace in Athens, I could not help thinking of the boobies. In both cases, the message seems to be “Hey, I’m the real deal! Check out these spectacular feet, and could any imposter possibly know all of these silly moves?”
Blue footed boobies, I think on a nest.
A Nasca booby (Sula granti), definitely on a nest.
This juxtaposition of Nasca boobies simply cried out to be “photoshopped”. Who was I to say no?
Reader Jim Trice from Oz sent me some photos from back in February; his notes and IDs are indented. One of the world’s cutest mammals is at the bottom.
Some recent visitors to my yard to help top up the photo tank. Shot 1 is of a damselfly resting on one of our lavender bushes in late afternoon light. I don’t have an ID for this species yet.
The spider is a garden orb spinner, probably Eriophora transmarina, another highly variable species, which seems to be the case with many Australian spiders. The “Spiders of Australia” web site has some information on these, including:
“Formerly called genus Araneus. These are the common garden spiders that make that familiar vertical orb-web usually at face level. The web is usually renewed after a night’s use and renewed the next evening. During the day the spiders remain in a hiding nearby. Males are the same size as females but with a slender abdomen, long legs and conspicuously clubbed palps.”
It’s a pretty accurate description, except it should read something like “…removed after a night’s use, and renewed the next evening.” This one built a new web just outside my back door exactly at my face height every night for months. The body of this spider is around 25mm, or an inch, in length. The web extends from the lower edge of our roof gutters to about mid chest height on me. But on this night the spider was above head height, and I needed a 3 foot step stool to get this shot. I also needed to shoot in manual mode as the hairs on the spiders body were highly reflective, bleaching out in my flash. I deliberately underexposed these shots by two stops, and brought the mid tones back up using curves.
The mantis is likely in the genus Archimantis, the stick mantids, and is probably a female Archimantis latistyla. This one is around 10cm long, but they grow to around 11cm. The adult females have reduced wings, and can not fly, but the smaller males do have fully formed functional wings.
This was quite a lucky mantis. She was trying to get herself squashed in our front door. But I rescued her and placed her somewhere more appropriate. I came back, camera in hand, about an hour and a half later. She had caught, and was much of the way through eating, a small vespid wasp. It might be Vespula vulgaris, the common wasp. We get a lot of them around that part of the garden.
And, though it looks odd, she really is upside down.
The koala, Phascolarctos cinereus, is a young female who came visiting near the beginning of a heat wave. She is clinging on to the trunk of one of our golden ash trees, Fraxinus sp., about 5 metres from my camera. When they are not foraging koalas often spend time in introduced trees. Their foliage is usually denser than Eucalypt foliage. This affords better protection from being mobbed by Australian magpies (Gymnorhina tibicen). It also provides better shade when they are heat stressed. Later that day she did indeed become heat stressed, and sat on the ground at the bottom of the tree. She became very annoyed with me and told me off quite vocally when I put out a tub of water for her, as I got closer than she was comfortable with. But I wanted the water close enough to the base of her chosen tree that she could easily flee up it if the neighbourhood dogs came by while she was drinking. She moved on about a day after that, which is pretty normal. They will typically spend between 1-3 days when visiting my yard, as we have many trees they can feed on, mostly grey box (Eucalyptus microcarpa), and a couple of South Australian blue gums (Eucalyptus leucoxylon).
Some kind readers have sent in photos, but I really could use more, so if you have some good ones (no duds!), send them along. Thanks!
Here’s a single photo, but a good one, sent just this morning by reader “grasshopper”. His/her/zir/their notes are indented:
Here is a photo I took this morning of a Grey Goshawk (Accipiter novaehollandiae), near Geelong, Victoria, Australia. This bird happens to be the white morph of the species. The bird sits upon my aviary quite frequently hoping to get a free feed, I think. [JAC: Beyond finding out that grey and white morphs interbreed freely, I haven’t located any genetic information on this variation, though I suspect, given the distinctness of the morphs and no reported intermediates, it’s due to segregation of alleles at a single gene.]
From reader Christopher:
I found this massive centipede (at least 4 inches long) under a large rock on a hillside in Climax Springs, Mo, on the Lake of the Ozarks. Perhaps some of the readers can identify it to at least the genus; I haven’t the foggiest idea. Whatever it is, it was spectacular!
From reader Chuck Spotts:
About 10 days ago (Feb 15 or so) a charm of hummingbirds arrived at my feeder here in NorCal.In the winter months prior, I had very few.In the winter a full feeder lasts 2 weeks or more.But recently I fill it every day and they drink it dry!I don’t know if they are just passing through or if they will sick around (I’d prefer the latter). They appear to be Anna’s Hummingbird (Calypte anna) both female and male.Time to buy sugar.
Finally, a lovely moth from W. Neil Everett, with some twig mimicry I hadn’t realized was a feature of this species:
Found this luna moth (Actias luna) resting at my front door this morning. Looks like he survived a bat or bird attack (frayed wing tips, looks asymmetric). I say “he” because the antennae are fairly feathery, which is supposed to be a characteristic of the male, although I don’t have another moth with less feathery antennae for comparison. I’m in central Texas, and it seems like this is about as far to the southwest as they’ve been spotted. The mimicry of a stem with leaf buds is phenomenal (especially in the early spring time), and it even has shading and highlights. Hard to fool echolocation, however.
After an absence of some time, naturalist and photographer Lou Jost has returned with some gorgeous photos of Ecuadorian wildlife. His notes are indented:
Earlier this month I visited the Canande Reserve of the Jocotoco Foundation, in some of the last remnants of the lowland rain forests of northwest Ecuador, to help them look for a new species of Magnolia (Magnolia canandeana) using my drone. While driving around looking for launching sites, I found a pair of Great Jacamars (Jacamerops aureus) on the roadside constructing their nest inside a termite nest. They don’t eat the termites as far as I know; they behave like Old World bee-eaters, using their long beaks to catch bees, wasps, cicadas, and large butterflies, which they beat to death and then swallow.
After this experience with the jacamars I started paying attention to the termite nests along the road. Sue enough, a few minutes later at a big termite nest, I saw another colorful pair of birds, the Western White-tailed Trogon (Trogon chionurus) making their nest.
At night there were exciting insects. The Peanut-headed Bug (Fulgora laternaria), a gigantic treehopper, was the best. This insect, called the Machaca by the local people, is widely believed to bite people, though it doesn’t. According to local legend throughout tropical America, if you are bit by one of these, you must make love within 12-24 hours or you die.
Night walks revealed a lot of action. I saw the thousand-and-one caresses of mating millipedes, and a sinister katydid belonging to the group of cone-headed katydids, which are often predatory rather than vegetarian. The climax of our night walk was a spider sucking the life out of a female cockroach while the cockroach’s babies escaped out of her rear end…..
In January I called your attention to “pelican spiders” (also called “assassin spiders”), a group once known only from amber fossils but which has recently been described from Madagascar, Australasia, and Southern Africa (as you’ll see in the video, that distribution makes evolutionary sense). The “assassin” name comes from their extraordinarily long chelicerae (jaws), which enables them to grab other spiders (their usual prey) holding them at jaw’s length so they can’t be bitten back during the attack.
At the time I put up my post, I couldn’t find any videos of this predatory behavior. Since then one has appeared in the New York Times, which I’ve embedded below (the predation takes place about one minute into the video) . Take two minutes to acquaint yourself with one of the weirdest arthropods around. (Click on the white arrow to start the video.)
Today we have reader Tony Eales’s photos from Australia, featuring insect and spider mimicry. His notes are indented.
Some more camouflage and mimicry. First I can’t stop photographing these ant-mimicking Jumping Spiders. This photo at least gives a bit of scale for how small these little arachnids are. It’s a Myrmarachne cf luctuosa. These are relatively common, but there’s a lot of slightly different forms—some of which are probably undescribed species.
Next is a tephritid fruit fly that mimics jumping spiders probably for protection. This species is Oedaspis goodeniabut there are several species with similar patterns. The patterns on the wings when held out look like a head-on silhouette of a Jumping Spider and they will make movements of the wings that increase the resemblance and mimic spider to spider threat displays of a jumping spider. Here’s one paper that looks at the phenomenon.
This next photo is an interesting colour form of Stephanopis sp, the Knobbly Crab Spider. It’s larger than the average Stephanopis. And its colouration perfectly mimics the common lichen found on the tree bark.
JAC: Here’s another photo of an S. antifrons, mimicking bark, from Brisbane Insects:
Lastly yet another Lycid Beetle mimic (boy, Lycid beetles must taste awful!). I sent a collection of Lycid mimics once before. The mimic in this case is a species of Belid Weevil, the Red Belid Weevil (Rhinotia haemoptera), which I only had a blurry photo of before. For reference I have included a shot I took of what I think is the model, the Red-shouldered Lycid Beetle,Trichalus ampliatus.
The title question is an evolutionary one: what were the ancestors of today’s spiders?
First, some taxonomy. You should know, if you don’t already, that spiders aren’t insects. They’re in the same phylum, Arthropoda, but then belong to the non-insect subphylum Chelicerata, the class Arachnida, and the order Araneae. But their evolutionary origins have been a bit murky, though we know they’re fairly closely related to the order Thelyphonida (also in the Chelicerata and Arachnida), containing whip scorpions—also called vinegaroons. Thelyphonids look sort of spiderlike, but have tails. Here’s a whip scorpion:
Well, the origins of spiders probably started with a creature that looked something like that, according to a new paper by Bo Wang et al. in Nature Ecology & Evolution (reference below, free access [might require UnPaywall], pdf here). The basis of the paper (and an accompanying paper; see below) is the discovery in Myanmar of two pieces of amber dates at least 100 million years old, each containing what appears to be a member of the same species. And that species sheds some light on the origin of spiders.
The authors name that species Chimerarachne yingi. This creature has a tail like a whip scorpion, but also has two distinctive features (“shared derived traits”, also called “synapomorphies”) that characterize spiders. First, sperm-transferring pedipalps, the anterior appendages that put sperm from the male’s gonads (deposited first on a small “web”) into the female’s reproductive opening (both amber specimens are males). Second, spigot-like spinnerets, the nozzles that squirt silk out of the abdomen. Here’s a ventral (bottom) view of one of the specimens, and its interpretation. The length of the black line in the photo is 1 mm (about 1/25th of an inch), so this creature is pretty small.
The pedipalps are labeled “Pd” at the top, and the four spinnerets are labeled “ALS” (anterior lateral spinneret) and “PLS” (posterior lateral spinneret). You can also clearly see the tail.
The tail of the whip scorpion, and likely of this specimen, serves not as a stinger (as it does in true scorpions), but as a sensory organ. Also, whip scorpions don’t have specialized pedipalps (nor spinnerets); insemination in that group is achieved by males transferring spermatophores (packets of sperm) using their different, pincer-like pedipalps. (Spider pedipalps have all kinds of other features for transferring sperm, including a “palpal bulb” that holds the sperm taken from the male’s abdomen.) Here’s a spider pedipalp versus a whip scorpion pedipalp:
Spider pedipalp (the dark bits are the complex “palpal bulbs”):
Whip scorpion (simple pincers):
The pedipalp of the new specimen C. yingi is complex, like that of a spider. Here’s a photo of part of the pedipalp, labeled “ta” for “tarsus”; the tarsus is modified for sperm transfer and is not a simple pincer. Scale bars in both photos below are 0.2 mm:
Here are the specimen’s four spinnerets:
I won’t belabor you with the morphological details, most of which are for specialists, but the important part is that we have a creature that is part spider and part whip scorpion. This leaves us with the big question:
Is this a “missing link” between spiders and whip scorpions? No, it isn’t, if by “missing link” you mean some kind of common ancestor. Nor is it really a “transitional form” between an ancestral creature with a tail and modern spiders, because already at 100 million years ago we see fully modern-ish spiders. This species and its mosaic relatives existed alongside spiders similar to those we see today, but C. yingi and its relatives probably went extinct without leaving descendants.
What it does show is that there were transitional forms between the morphology of the ancestor, which based on phylogeny probably had tails, and that of modern spiders. In other words, this gives us an idea of what the transitional form might have looked like, even though it wasn’t on the evolutionary route to modern spiders. Here’s the phylogeny the authors came up with, showing the placement of C. yingi as a sister group of spiders (Araneae).
Note that this phylogeny is unclear, as different methods give different results. In fact, I just now discovered there’s another paper in the same issue, by D. Huang et al., (reference below) arguing that this specimen belongs in an extinct sister group of spiders, the “Uraraneidae”, as seen in the phylogeny below (Huang et al. put the specimen in that group rather than occupying its own branch).
(from paper): Consensus cladogram (Bayesian majority rule consensus with support values) showing the position of C. yingi within the Pantetrapulmonata branch of the arachnids, which encompasses the spiders and their closest relatives (see Supplementary Fig. 3 for the full annotated tree). Both Attercopus and Permarachne are incomplete and scoring them individually collapses the tree, thus we combined characters from the two genera into one terminal Uraraneida.
So there’s still some confusion about where this specimen resides on the arachnid family tree. But to some extent it doesn’t matter. What this specimen shows is that at one point there was a mosaic species that had the tail of a whip scorpion (in the “pedipalpi” above) and the palps and spinnerets similar to those of a modern spider.
Both papers show that this creature wasn’t an ancestor of modern spiders because it coexisted with modern tailless spiders. What it gives us is an idea of what the transition from tailed arachnid to tailless spider might have looked like, and, importantly also pushes back in time the evolutionary origin of spinnerets and specialized pedipalps, which could have existed in the common ancestor of Uraraneids and spiders (the node labeled “1” in the phylogeny above.
Here’s a figure from the Huang et al. paper (which I’ve only skimmed), that analyzes the same two specimens as Wang et al. to reach a slightly different phylogenetic conclusion. But this figure is very nice, showing the animal with its complex pedipalps (“b”) and spinnerets (“h”):
(from paper): a, General habitus. b, General view of pedipalps. c, Detail of chelicerae (arrow points at cuticular striae). d, Detail of palpal tarsi. e, Detail of leg III (arrow points to metatarsal trichobothrium). f, Detail of the posterior lateral spinneret with the spigots. The red arrows indicate segments. g, Ventral view showing the clear, broad sternum. h, Detail of the spinnerets, pygidium and proximal portion of the flagellum. Scale bars: 1 mm in a; 0.2 mm in b–f; 0.5 mm in g and h.
