Readers’ wildlife photos

December 11, 2021 • 8:00 am

Send in your photos, please; the holidays will soon be on, and nobody will be reading or sending. Thanks!

Today’s photos, a great batch, come from regular Tony Eales from Queensland. His notes are indented, and you can enlarge his photos by clicking on them.

A grab bag of rainforest finds.  I’ve been getting seriously addicted to doing night walks in the local rainforest. There’s a lot of different species out compared with the day, and different activities are going on.
Like cicadas emerging from their pupal shells, this one is a Green Grocer (Cyclochila australasiae). One of the favourite photos I’ve ever taken.

I encountered this mantidfly (Ditaxis biseriata) wandering about on a huge tree fallen limb. The ones I’ve found in the rainforest in the day have flown off quickly but this one seemed very interested in my lights.

A lot of sex seems to happen at night as well. Who would have thought that cockroach sex would be so weirdly beautiful? These are in the family Ectobiidae, but more than that I do not know.

There’s a few species I only ever see at night, like this huntsman (Heteropoda hillerae):

And these harvestmen, probably an undescribed Neopantopsalis species:

. . . and these weird crickets in the ‘Cave Weta’ family Macropathinae:

During the day these spiders (Genus Namandia in the family Desidae) stay deep in their messy cobweb retreats in the hollows and forks of trees. But at night they run out and grab anything walking around on the trunk of the trees. This hairy caterpillar’s spines were apparently no defence.

The lower trunks of the trees are full of these prehistoric looking pygmy grasshoppers (Tetrigidae). They are both armoured and camouflaged and difficult to photograph well, but worth the effort. This one is  Vingselina crassa. [JAC: Look at those hoppers!]

Not just invertebrates come out at night but also vertebrates and normally shy frogs are rather easy to approach and photograph at night time. This one is the Dainty Tree Frog, Ranoidea gracilenta, a fairly common frog but one I never tire of photographing.

Readers’ wildlife photos

September 24, 2021 • 8:00 am

I have returned, and I hope that some of you have accumulated wildlife photos to send me for the cache. Now is the time!

Today’s contribution of spider photos is from Tony Eales of Queensland. His notes and IDs are indented, and you can enlarge the photos by clicking on them.

Spider guru Dr Robert Raven, Head of Terrestrial Biodiversity & Senior Curator of Chelicerata at the Queensland Museum, has been telling me for some time now that the way to survey for spiders is to leave your diesel engine running for a while, and the spiders will come crawling out of the surroundings like hypnotised zombies. I had tried this a few times with little success, but recently I tried it on some sandy loam in coastal heath near Bundaberg, Queensland, and it worked beyond my wildest expectations.

Big spiders, little spiders, huntsmans and jumpers and especially ground spiders all came out toward the car. As did a lot of native cockroaches. And at one site the engine vibrations seemed to induce a bunch of spiders to compulsively climb a small tree near the car. I can’t wait to try it again.

Here’s a small sample of some of the things that came running to the siren call of the diesel engine.

One of the larger spiders to come out (around 20mm) and an unusual one. Asadipus sp. There are only seven observations of this genus on iNaturalist. It comes from an Australasian family Lamponidae which has the undeserved reputation of giving necrotic bites, though there is no solid evidence for this idea.

This little guy is probably Epicharitus sp or something related. This genus of striking black and white spiders belongs to the family Gnaphosidae. This is a varied cosmopolitan family known rather unhelpfully as Ground Spiders. [JAC: Wikipedia notes that “Epicharitus is a monotypic genus of Australian ground spiders containing the single species, Epicharitus leucosemus.”, so that may be the species.]

This one is Mituliodon tarantulinus, also knowns as the Little Tarantula even though it’s not remotely related to tarantulas. It’s in the family Miturgidae with the ominous common name of Prowling Spiders.

This is a juvenile wolf spider (Lycosidae). As it’s so young, it’s hard to guess at the ID. Quite pretty, though.

By far the most common family attracted to the car were members of the family Zodaridae AKA Ant Spiders. This one is Habronestes hunti and the next two are ones I have yet to get an ID for.

And lastly a couple of the spiders that climbed the small tree in response to the engine vibrations. Hamataliwa sp from the Lynx Spider family Oxyopidae.

And a lovely male Helpis minitabunda: A jumping spider, family Salticidae.

Readers’ wildlife photos

September 8, 2021 • 8:00 am

I am running very low on photos, with less than a week’s worth left—and some of them singletons.  Please send your good wildlife/street/travel photos, or we’ll have to abandon this feature.

Today’s contribution is from a regular, Mark Sturtevant, whose IDs and descriptions are indented. Click on the photos to enlarge them.

Here are more pictures of arthropods from way back in 2019. These were taken at various Michigan parks late in the season. Autumn was rapidly closing in, and this is my final set of pictures for readers from that year.

First up is a six-spotted fishing spider (Dolomedes triton), with barely a one inch leg span, so she is just a youngster. Folks may remember earlier pictures in which I used a much bigger adult spider to show that they are able to catch fish and also dive under water. But here this little one is demonstrating that they are quite skillful at hunting above the water as well.

This very small Muscid fly (species unknown) was so intent on feeding on a drop of berry juice that I could get all fancy at using my highest magnification capabilities. A good macro lens with a Raynox diopter attached can do wonders at boosting magnification. If people don’t have a macro lens, a Raynox diopter is still an easy and inexpensive way to get good close up pictures with the lenses you have now.  Raynox lenses were also helpful at taking the next two pictures.

I can usually find a few of these psychedelic leafhoppers in my yard (Graphocephala coccinea). Most are blue and red, but some are green and red. An accepted common name is ‘candy-striped leafhopper‘:

I saw this marsh fly (Tetanocera sp.) with something odd stuck on it. Marsh flies are fortunately pretty mellow about being photographed. What I saw through the camera viewfinder was a significant surprise, for this one was carrying a bunch of little pseudoscorpions! Pseudoscorpions are small arthropods, related to scorpions, and they are known for hitching a ride on insects as an aid to their dispersal. Now I must look carefully at each marsh fly that I see.

Next up is our largest damselfly, the great spreadwing (Archilestes grandis). The first picture shows a lovely male, and the second is a mated pair in which the male (on the left) is guarding the female while she inserts eggs into a twig above a stream. The hatchlings will have to drop about eight feet to the water below.

Next up is an underwing moth that I found in a park shelter while waiting out a sudden rain shower. The species looks to be Catocala amatrix. “Catocala” is Greek for ‘beautiful below’, which refers to the flashy hind wings that are typical of this large genus of moths. Underwing moths utilize a combination of camouflage and deception to thwart predators. When disturbed, they charge into rapid and evasive flight, flashing their colorful hind wings. They generally land on a tree trunk (sometimes ducking to the back side first), and with folded wings they are well camouflaged. Underwings will often scooch over several inches after landing as well. A predator will be challenged to find the flashy insect that they were following! If I were a bird, I’d just give up.

The next picture is an alien landscape of mosses and I don’t know what else, taken as a focus stacked picture early one morning. This is some of the ground cover in a marvelous place I like to call the Magic Field.

Finally, with autumn and the end of a fabulous season rapidly coming to a close, I found this queen bald-faced hornet (Dolichovespula maculate) who was going into hibernation under a fallen tree log. She was of course carefully returned to her retreat after a few pictures.

Thanks for looking!

Readers’ wildlife photos

August 14, 2021 • 8:00 am

Please send in your photos!

Today’s batch is quite diverse in content, and comes from reader Leo Glenn, whose notes are indented. You can enlarge the photos by clicking on them.

I haven’t been able to take many photos lately, and my archive is fairly disorganized, so here is a somewhat random collection of photos. The only thing tying them together, really, is that they were all taken within walking distance of my house in western Pennsylvania. I’ve also included a “macro” photo that you could use as a “What am I?” quiz, if you so desire. The subsequent photo is the reveal.  [JAC: I’ll put it below the fold.]

American giant millipede (Narceus americanus), a relatively common sight on my daily dog walk:

Gray treefrog (Dryophytes versicolor), so named because they can change color from gray to green or brown. Far more often heard than seen, this one was down near the ground and politely lingered long enough for me to take its picture:

Another organism with the species name versicolor, the Turkey Tail mushroom (Trametes versicolor)

Yellow morel (Morchella esculenta), from my secret morel patch:

Crown-tipped coral fungus (Artomyces pyxidatus):

Our mulberry tree had a bumper crop this year, which attracted many bird species, including this Black-billed cuckoo (Coccyzus erythropthalmus), seen here, though, on a neighboring red maple (Acer rubrum).

Red-headed bush cricket, also known as a Handsome trig (Phyllopalpus pulchellus):

Pennsylvania leatherwing, also called a goldenrod soldier beetle (Chauliognathus pensylvanicus):

And a photo from this past winter. Even the Eastern gray squirrels (Sciurus carolinensis) were social distancing:

Finally, here’s the photo for the “What am I?” quiz:

To see the reveal, click “read more”:

Continue reading “Readers’ wildlife photos”

Readers’ wildlife photos

August 3, 2021 • 8:00 am

I’m running out of photos to post, so once again I importune readers to send me their good wildlife/landscape/street photos. The need is urgent. Thanks!

Today we have a melange of photos from several readers. Their captions are indented, and you can enlarge the photos by clicking on them.

First up are moose and elk photos from Stephen Barnard in Idaho.

I had another visit from mama moose and the twins. Not knowing the moose [Alces alces] were in the front yard, I let my dogs out to confront them face-to-face. The dogs started barking like crazy, of course, but obediently came back in. Mama and the twins were unperturbed and kept browsing on my shrubbery, finally crossing the creek in the usual place.

I don’t normally see elk [Cervus canadensis] herds in this field this time of year, because I’m normally growing barley or alfalfa so the farm hands scare them off. This year, because of the irrigation restrictions, I’m not growing anything, so there’s no one to bother them. The air is clouded with smoke from wildfires.

From Leo Glenn:

Here are a few that I took back in May of a white-tailed deer (Odocoileus virginianusdoe and newborn fawn. This was just beyond our orchard in our back yard, in western Pennsylvania.


From Laurie Berg:

Immature eagle with former mouse

Limpets from  Ken Phelps:

And from Diana MacPherson:

I took this on my iPhone of the tiny little thing. This pseudoscorpion lives in my bathroom enjoying the humidity.  Isn’t he/she cute?

Readers’ wildlife photos

January 27, 2021 • 8:00 am

Please send in your best wildlife photos. I have a reasonable backlog, but it gets depleted quickly.

Today’s arthropods are from regular contributor Tony Eales from Queensland. His notes and IDs are indented; click on the photos to enlarge them.

I’m afraid I’m going to spam you with a few because I’ve had a good couple of weeks finding new weird beasties that I’m keen to share.

There’s been a lot of new life of late in the rainforest, with the spiders in particular producing slings (that’s what we spider lovers call ‘spiderlings’)

My favourite rainforest cellar-spiders, Micromerys raveni, are producing eggs and babies, and I managed to capture three stages in one afternoon. A gravid female, a female with eggs and a female with newly hatched slings on her back.

Also, at the tips of some palm leaves are folded tetrahedrons held together with silk. If you can carefully open them a crack there is a mother long-legged sac spider, Cheiracanthium sp. with her newly hatched young.

There seems to be no season to the little green jewel-like Chrysso sp.: I rarely see one without a clutch of humongous (relative to the mother) eggs.

I also love to find these tiny white Theridiids, currently undescribed but will probably go into the genus Meotipa. Looking at the developed eggs I suspect that spider eggs don’t so much hatch as just develop into slings. Does anyone know?

Finally, an unknown Theridiid mother inside a cured leaf retreat with her brood.

Readers’ wildlife photos

July 25, 2020 • 7:45 am

The photo tank is running low, so please send in your good wildlife photographs.

Today’s contributor is a regular, Mark Sturtevant, with some lovely arthropod photos. His notes are indented.

This is the last installment of pictures taken last Spring when I was visiting the Phoenix, Arizona area for several days before attending a fancy teaching conference.

First is a picture of a buckeye butterfly (Junonia coenia), a species that is widespread in the U.S., followed by a white peacock butterfly (Anartia jatrophae), whose range is restricted to southern states so it was new to me. I saw plenty of both on this trip, but they were easy pickings in the Desert Botanical Garden.

Next is a male western pondhawk (Erythemis collocata). Very similar to the eastern species back home, but eastern pondhawks have white cerci (the paired appendages near the tip of the abdomen), while the western species have black cerci.

I spent much time in the Tonto National Forest. This national forest covers an enormous part of the state, and in its northern range it is indeed forest, but in the Southern range it is of course Sonoran desert. Central to this region is the Salt River, which is wide but shallow (I could easily wade across it), and it is sustained by periodic releases of water from a dam. It is not unusual to see herds of wild horses at the river, and indeed I saw a large herd some distance away that was being surveyed by another photographer who had a lens that was the size of a fire hydrant. Here is a lovely video that features these animals, and you can see some of the Sonoran desert scenery as well.

Rubyspot damselflies were hoped for and found at the river. There is more than one species that is possible, but these are most likely the American rubyspot (Hetaerina americana). The first are females, and the last is a male. The males were firmly staying out on the water so I had to wade out and basically lie prone in the river to photograph them. It was like a warm bath.

Next is a beautifully camouflaged pallid-winged grasshopperTrimerotropis pallidipennis. Had to lie down on the hot ground for that one!

My last day goofing off was spent at the Hassayampa Forest Preserve that was north of Phoenix. This was a long drive to a higher elevation, so that the Sonoran desert was displaced by grassy meadows and deciduous forest. Part of the time in this park was spent searching for Dangerous Things by lifting up loose tree bark. This being Arizona, it did not take long!  The next picture shows a western black widow spider (Latrodectus hesperus). The link provides some information about the various species of ‘black widows’ in the U.S. In addition there are a couple other species of widows that we have.

Shortly after that I found what I was really after: an Arizona bark scorpion (Centruroides sculpturatus). This was a very satisfying end to the adventure!

And with that, it was time for the long drive back across Phoenix to the airport to drop off the rental car and experience the surreal plunge of being in civilization and mingling with people.

Readers’ wildlife photos

May 29, 2020 • 7:45 am

Tony Eales from Brisbane has sent us a collection of mixed arthropod photos. His notes are indented:

I just thought I’d throw together some oddballs for fun.

First, a tiny little mite known as a whirly-gig mite family Anystidae. These guys are so small and fast that I rarely attempt to photograph them even if I see one. However this one stopped for half a second and I just managed to get the focus.

Next, a particularly pretty planarian worm called Australopacifica regina, found in the local subtropical rainforest under a log.

This is one of the cup moth or slug moth caterpillars. Calcarifera ordinata. The stings are said to be particularly fierce. Happily so far I remain un-stung, touch wood (actually don’t touch anything in the bush, it probably stings or bites, just take photos).

Next a few spiders. First, an undescribed member of the genus Celaenia. This genus generally imitate bird droppings though this one not so much. Still, it l doesn’t look very appetising.

Second an ant-mimicking jumping spider. Not as convincinga  close-up as the more well-known Myrmarachne species, but from above at a glance, it’s still very ant-like. This one is genus Ligonipes sp: .‘white brows’. A very common but as yet undescribed species.

The last spider is an Oonopid aka goblin spider. Maybe, genus Grymeus. I’ll know more later as there’s a person at the Qld Museum currently working on the family and I’m sending the specimen in to go into the collection. For fun I’ve added a picture of the spider in the test tube. See if you can spot it.

I picked up something fairly rare the other day, a species of lace bug, Tingidae. To me it looked like the fairly common pest known as the Azalea Lace Bug Stephanitis pyrioides but the experts said “Oh no, The shape of the hemelytron is distinctly different. This is an Australian endemic, Lepturga magnifica. In any case, it’s an interesting looking bug.

Weevils are so diverse and there are some extreme variations on the weevil bauplan. This is one of the odder ones Rhadinosomus lacordaireei or Thin Strawberry Weevil.

Last but not least, a weird offshoot of in the lacewing Order Neuroptera, a Beaded Lacewing in the family Berothidae. These are unusual within the Neuropterans for having particularly hairy wings. The one pictured is  Stenobiella sp. The larvae of these lacewings live in termite mounds, apparently unmolested, snacking on a passing termite when hungry. Wired did an article on how the larvae have been observed to paralyse the hapless termite with termite-stunning farts


Readers’ wildlife photos

February 7, 2020 • 7:45 am

Please send in your good wildlife photos (roughly ten to a dozen if you have that many, though fewer are also welcome). And please supply locations and Latin binomials.  Thanks! Today’s batch comes from regular Mark Sturtevant, whose comments are indented. Note that in his first sentence Mark says, “I do me”!

Here are more ‘Arthropodian’ pictures from two summers ago. It is what I do.

The first picture shows one of many of our very quiet ‘housemates’. Cellar spiders will frequently return to old prey to scratch out a meager living, and will even accept dead and dried prey. They are very welcome to all the carpenter ants they can find. It is described that in the U.S., cellar spiders who live in homes are almost always one of three introduced species. This seems to be Pholcus phalangoides. The white patch on the abdomen is the cover for one of her respiratory openings. Spiders breathe through a pair of ‘book lungs’, which are stacks of thin respiratory membranes in the abdomen.

Late in the summer I have been regularly venturing outside at night in hope of photographing the male snowy tree crickets who loudly announce their presence from our bushes. It turns out that they are surprisingly hard to pinpoint, since they seem to ‘throw their voice’, and so I usually come away cricket-less. But here I managed to surprise this angle-wing katydid nymph (probably Microcentrum rhombifolium). The adults of these large katydids are also heard calling at night, but adults generally stay well out of reach in the trees.

The parasitized hornworm caterpillar in the next picture comes with an amusing story. I was out in a park one day when this professor I knew from work abruptly emerged from a trail carrying this branch with the caterpillar on it. He had been wearing the leafy branch on his head to keep away mosquitoes and was later surprised to see this caterpillar hanging down right in front of him! He gladly relinquished the find, and here it is. This should be a larva of one of our clearwing sphinx moths, although this one has defied identification beyond that. The white objects are the cocoons of parasitic Braconid wasps. The caterpillar of course is doomed.

In the next picture is a lovely moth that is clearly an excellent wasp mimic. It was sitting out in our back yard, and represents one of the many occasions where I find something in the back yard and have to drop everything to grab a camera. This is the red maple borer mothSynanthedon acerrubri, and it may have come from a red maple tree that we have.

We continue with a couple more Lepidopterans. I generally no longer bother with monarch butterflies (Danaus plexippus), but this sleeping one was letting me get very close to it. I liked how the light was working, and so I ‘bothered’. The flower head that it is on is teasel, an invasive species. The plant is much loved by butterflies and other pollinators, but now there is so much of the stuff that I am well at the point of not liking it.

The margin of a certain lake frequently turns up butterflies that sit near the water to imbibe the salts and amino acids from the wet bare ground. The next picture shows a perfect red-spotted purple butterfly (Limenitis arthemis) that was on the shore. The colors really pop with the camera flash!

In the woods I can usually find one or two of the species shown in the next picture. From a distance they look like a small wad of fluff on a tree trunk, only this little bit ‘o fluff will be slowly moving and has a set of very long mandibles. This is a species of debris-carrying ‘aphid-lion’ larva, and so is the larval form of one of our green lacewings (genus Chrysopidae). The debris that it is carrying is for concealment and protection from its own enemies.

The next picture is of a leafcutter bee (genus Megachile) at an artificial bee house that was being kept in the public garden at a local park. I should get one of these bee houses for yard, as watching all the drama taking place was very absorbing! Leafcutter bees are solitary, and females will raise their larvae in wood or earthen tunnels. They can raise several larvae at a time in separate pollen-filled chambers that are divided by pieces of leaves. This old video tells their story in charming detail:  What I am now curious about is how the new brood of bees exit the tunnel, since the ones developing deeper in a tunnel would surely be older. How do they emerge without harming their younger siblings who would be nearer the exit? 

Finally, during a particular window of time in the summer I will frequently come across the strange bee that is shown in this last picture. It is also a leafcutter bee, but it is a kleptoparasitic species (Genus Coelioxys). That means the females will lay eggs in the nests of other leaf cutter bees, and its larva will eat the food of its host. They are always very alert, and so this one had to be photographed at some distance, so the picture is heavily cropped. 

Fossilized trilobites preserved parading in line. But why did they do this?

October 18, 2019 • 9:30 am

A new paper in Nature by Jean Vannier et al. reports the unusual finding of a parade of trilobites—a group of the ancient arthropods—apparently killed and fossilized while walking in tandem, like an invertebrate conga line. They’re 480 million years old, from the Lower Ordovician, and were found in Morocco. (The paper can be seen by clicking on the screenshot below, the pdf is here, and the reference is at the bottom.)  This weird lineup of trilobites suggests some kind of collective behavior—the first such find documented by paleontologists. But what kind of behavior? The authors have two hypotheses, and I’ll discuss them briefly.

First, some photos of the species, Ampyx priscus, which had a hollow “glabellar spine” in front and two “librigenal spines” going backwards. The white scale line is 1 cm long, so these things were, including the front spine, about 6 cm (2.3 inches) long. The spines might have enabled the trilobites to sense each other and thus maintain contact while moving in line, much as spiny lobsters do when moving across the sea floor in line as I show below. (Any “communication” must have been tactile as these trilobites were blind.)

All captions are taken from the Nature paper. Here are the individuals at hand, with some close-ups of their spines:

General morphology and parameters of the raphiophorid trilobite Ampyx priscus Thoral, 1935, from the Lower Ordovician (Upper Tremadocian-Floian) Fezouata Shale of Morocco (Zagora area). (a–d) BOM 2481, overall morphology and details of genal spines. (e) Parameters used in measurements. (f,g) MGL 096718, genal spine showing internal mineralized infilling. (h) AA.OBZ2.OI.1, transverse thin section through right genal spine (see general view in Supplementary Fig. 8d). (i) MGL 096727, genal spine. (j) ROMIP 57013, external mould of glabellar and genal spine showing longitudinal ridge. a–d,f,g,i,j are light photographs.

Here are the fossils of the lined-up trilobites, which are remarkable, along with schematics showing the nature of the relief of the stone in which they were preserved.

Linear clusters of the raphiophorid trilobite Ampyx priscus Thoral, 193531, from the Lower Ordovician (upper Tremadocian-Floian) Fezouata Shale of Morocco (Zagora area). (a,b) AA.TER.OI.12 (see Supplementary Fig. 2a). (c) MGL 096727 (see Supplementary Fig. 5a). (d) AA.TER.OI.13 (see Supplementary Fig. 2b). (e) BOM 2461 (see Supplementary Fig. 2f). (a,e) are light photographs. Line drawings from photographs. Segmented blue lines in (b–d) join the central part of occipital rings of trilobites. Red arrows indicate the position of polished section in Fig. 3. Abbreviations are as follows: (x), Asaphellus aff. jujuanus (asaphid trilobite); (y), juvenile asaphid trilobite. Scale bars: 1 cm.

Here’s a video of spiny lobsters migrating in line, much like these trilobites:

So why were these ancient arthropods marching in line? The authors reject two hypotheses. First, that they were “mechanically accumulated along linear submarine reliefs (e.g. between ripple marks)”.  This is the hypothesis that they were blown into grooves in the ocean floor and accumulated there, explaining the lines. That, however, doesn’t explain the consistent alignment rather than some being blown in backwards. The authors reject this because there is no indication from the fossil strata themselves that there were these reliefs.

They also reject the hypothesis that these trilobites were lined up in burrows underwater and then trapped and killed by sediments. Their rejection is based on the absence of “any colored outlines or disturbances in the sediments surrounding trilobites.” I’ll trust the authors on this since knowing how to detect ancient burrows is above my pay grade.

Rather, the authors proffer two hypotheses to explain the alignment. The first, shown on the left below, is that there were underwater storms or currents that made the trilobites orient in one direction, and then they “found” each other by tactile signals (or perhaps also by chemical signals), forming a line that served a protective function. As the authors say, “Such mechanical contacts [as in the lobsters above] appear to be essential for group cohesion and for optimal coordinated locomotion.” Marching in a line reduces drag, saves energy, and, say the authors, “reduces the probability of detection and attacks by predators by creating confusion in their [predators’] visual perception.”

The second hypothesis, shown on the right below, is that the trilobites emitted chemical signals like pheromones as a way of detecting each other and coming together for sexual reproduction, with the lines presumably indicating a migration toward spawning grounds. As the authors note, both explanations could be operating together.

Two non-exclusive hypotheses to explain the linear clusters of Ampyx priscus from the Lower Ordovician of Morocco. (a–c) Response to oriented environmental stress (e.g. storms); hydrodynamic signal (higher current velocity represented by white arrows) received by motion sensors triggers re-orientation of individuals; mechanical stimulation and/or possible chemical signals cause gathering, alignment and locomotion in group. (d–f) Seasonal reproductive behaviour; chemical signals (e.g. pheromones; see red circles and red arrows) cause attraction and gathering of sexually receptive individuals (males and females) and migration to spawning grounds. The alignment of individual may have been controlled by mechanical stimuli (as in a–c). Olfactive and mechanical sensors were probably located on the antennules (pink areas 4, 5), and genal and glabellar spines (green areas 1–3), respectively. The exact location of mechanoreceptors is uncertain (possibly on high-relief exoskeletal features such as the glabella).

As for how they were buried together, that’s a bit of a mystery since trilobites, when stressed, are supposed to have curled themselves into balls like modern isopods, and these didn’t do that, as you can see above. Here’s one scenario that explains the successive strata in which lines of trilobites were buried.

First, subject to periodic storms that disturbed the waters, the trilobites joined up in a Big March. (Or, as I noted above, they could be marching for mating!). Then, the storm quickly deposited sediment atop the marching trilobites, preserving them in situ. There could have been two other events that preserved them quickly: “water poisoning,” like the release of hydrogen sulfide gas or, more likely, the upward movement of oxygen-poor (“anoxic”) sediments, which killed the trilobites quickly from lack of oxygen as well as protecting the carcasses from scavengers.

You can see one instance of preservation in panels a-c below, and then another line of trilobites forming in panel “d”:

Scenario to explain the in situ preservation of the Ampyx linear clusters from the Lower Ordovician (Upper Tremadocian-Floian) of Morocco. (a) Deposition of a distal tempestite (event layer 1). (b) Epibenthic (e.g. trilobites) and shallow endobenthic (e.g. possible worms) organisms settle and generate bioturbation above red-ox boundary. (c) Second storm event layer entombs epibenthic fauna in situ; red-ox boundary moves upwards (white arrows). (d) New faunal recolonization. According to Vaucher et al.34, distal storm deposits are relatively thin (less than 5 cm) and consist of a waning (base) and waxing (top) phases (subdivision not represented in this diagram), and depositional environment is that of the distal lower shoreface with a possible water depth of approximately 30–70 m. Bioturbation is based on polished and thin sections (Fig. 3 and Supplementary Figs 8 and 9). Abbreviations are as follows: bt, bioturbation; tr, trilobite group (Ampyx); trc, trilobite carcasses (Ampyx); w, worm; wsi, water-sediment interface.

Now much of this is speculative, as it must be with limited information about what happened 500 million years ago. But it certainly looks as if, like spiny lobsters, these trilobites were marching in line, probably following each other using tactile cues. And so we get a rare window on invertebrate behavior from the distant past.


Vannier, J., M. Vidal, R. Marchant, K. El Hariri, K. Kouraiss, B. Pittet, A. El Albani, A. Mazurier, and E. Martin. 2019. Collective behaviour in 480-million-year-old trilobite arthropods from Morocco. Scientific Reports 9:14941.