Trilobite “horns” may have been used as weapons in male-male combat

January 19, 2023 • 9:15 am

Years ago I met Richard Fortey at the inaugural meeting of Spain’s new evolution society, and found him an affable and lovely guy. He’s a paleontologist and writer, and I had the pleasure of reading and giving a positive review to his first book, Life:  A Natural History of the first Four Billion Years on Earthwhich is well worth reading (he’s written several other books, including Trilobite: Eyewitness to Evolution (also a good read).

And it’s four trilobite species that are the subject of Fortey’s new paper coauthored with Alan D. Gishlick, a geophysical sciences professor at Bloomsburg University, in PNAS, a paper you can read for free by clicking the title below (it’s free with the legal Unpaywall app., the pdf is here, the reference is at bottom, and judicious inquiry might yield a pdf if you can’t see the paper). Trilobites are common fossils, and were marine arthropods that went extinct without leaving descendants.

The upshot is that Gishlick and Fortey analyzed fossils of one species of trilobite found in Morocco, deriving from the Devonian (400 million years ago). This species, Walliserops trifurcatus, had a long trident attached to the front of their bodies, and tried to figure out what it was for. They also found one adult individual whose trident was a bit deformed (see below). Their conclusion is that these were weapons used by males to fight with other males, almost surely to compete for females. They are, posit the authors, the arthropod equivalent of reindeer horns. The other possible functions (feeding, digging, etc.) were largely ruled out.

Read on:

Here are four species of Walliserops, shown below. All specimens bear a rigid cephalic trident. W. trifurcatus has a slightly recurved trident that bends upwards, while the other species have tridents more flush with the surface of the sediment (all captions come from the paper):

Four recognized species of Walliserops: A. trifurcatus, UA 13447 (topotype); B. hammi, UA 13446 (holotype); C. tridens UA 13451 (holotype); D. lindoei ROMIP 56997. Images taken from photogrammetric models. (Scale bar, 10 mm.)

The obvious question is: what is this damn thing for?  And there are several hypotheses, all assuming that the structure was molded by natural selection (which includes sexual selection). The authors find evidence against all but one possible function. Here are the alternatives (of course, it could have been used for several things, but it’s likely that selection was wholly or largely on one function). Indented bits are quotes from the paper. The rest of the discussion concerns W. trifurcatus:

A.) Defense. Perhaps the structure could have been used to ward off predators, like the spines found on other trilobites.  Here’s how the authors rule this out:

However, such a function would have been difficult given the overall anatomy of the trident and the trilobite. The trident is rigidly attached and cannot be moved independently from the cephalon; it could only be flexed in a dorsal-ventral plane by the trilobite raising and lowering its cephalon. This would create further difficulties since the long genal spines limit how high the head could be angled without lifting the entire body. The trident, therefore, could not be employed in a versatile way, nor be presented as to defend from a predator attacking from above or behind. This morphology is not consistent with a defensive structure.

B.) A feeding structure.  Doesn’t seem likely:

A second possible function for the trident would be as an aid to feeding. Like all members of the Phacopida, Walliserops was probably a scavenger/predator, and it might be considered as a possibility that the trident was a comparatively sophisticated sensory device concerned with early detection of prey species—such as buried annelid worms—which could then be grasped by the endopods of the ventral limbs.

C.) Sensory detection of the environment.  This is also deemed unlikely from inspection of the structure:

However, examination of the trident in optical and scanning electron microscopy failed to find the arrays of cuticular pits or tubercles usually indicative of the presence of sensilla in fossil arthropods. Most groups of trilobites include species with exterior exoskeletal pitting that is preserved even if the intracuticular canals have been removed by calcite reorganization—and there is no evidence of such exterior pitting on the trident of Walliserops. The absence of evidence for specialized organs on the tines makes it unlikely that it was primarily a sensory apparatus.

D.) A spear to pierce prey:  Unlikely because the structure was inflexible, so the animal would have no way of accessing speared prey.

E.) An apparatus to dig, perhaps for prey.  The way it’s shaped and angled seems to preclude this (remember, it’s slightly recurved upward; see below):

Another possibility is that the trident may have been used to agitate sediment to disturb prey items, which could then be trapped by the limbs. It is difficult to conceive of W. trifurcatus digging into sediment because to engage sufficiently with the substrate the cephalon would have to tilt at an angle greater than would be allowed by movement on the posterior occipital margin. Equally, if the thorax was arched, the pygidial spines themselves would dig into the sediment.

F.) A combat device on males molded by sexual selection mediated by male-male competition for mates.  The authors consider this most likely, especially because the tridents resemble the structure of male dynastine (rhinoceros) beetles, which use them to fight for females.

Here’s a picture of three of those beetles which have similar projections as do the Walliserops trilobites (the one at the extreme right).

(From the Natural History Museum): An image comparing the different beetle morphologies as they relate to fighting mode compared to Walliserops. © Alan Gishlick

The authors did a complex morphometric analysis of body and horn shape of W. trifurcatus, comparing it with living rhinoceros beetles to see if the trident could have been used for shoveling/prying, grasping, or fencing—the three types of male-male combat seen in living beetles. The analysis puts the trilobite in the group of living rhinoceros beetles whose males fight by fencing/shoveling: jousting with the structure in front and then trying to shovel the opponent over onto its back. I won’t go into the gory statistical details, which involve principal-components analysis, but the recurved structure of the trilobite’s “trident” is similar to that of shoveling, prying, and fencing beetles (left column: observed means of fighting of living beetles; center: the cephalic structures used; right: the species name [trilobite at the bottom]).

Cephalic structures of taxa treated in this research in lateral view showing the nature of the curvature and orientation of the tip of the active weapon and how it relates to its employment in combat.

 

As you see, and as the statistical groupings show, W. trifurcatus is similar to the structures used in rhinoceros beetles for fencing, prying and shoveling. Here is Gishlick and Fortey’s scenario of how the males battled it out in the competition to pass on their genes:

We would hypothesize a fighting scenario in Walliserops similar to that of Trypoxylus. The trilobites would meet and at first spar with their forks, pushing and poking. At some point, they would shift to trying to slide the fork under the other, in an attempt to flip them over. Given the morphology of Walliserops, flipping would be a very effective combat technique. Although the appendages of Walliserops are unknown, it is likely that they were like those of other phacopids in not extending beyond the carapace. This is seen in the Devonian Chotecops, asteropygines Asteropyge, and Rhenops, and recently described in three-dimensional material from the Silurian Dalmanites. Once the trilobite was inverted, righting would not be a simple matter, especially if the dorsally directed spines had snagged in the sediment. An upended trilobite would probably be even more helpless than a beetle in this position and thus excluded from sexual competition.

It might also be dead!

Now the first thing that struck me when I saw this paper was the question that would have occurred to many of you: WHERE ARE THE BLOODY FEMALES??  One of the signs of male-male competition is that the structures used to compete are present in males but almost never in females, as they’re of no use in that sex—and detrimental to fitness if you don’t use them. Male deer have antlers, females do not. Body size, used for combat in elephant seals, is huge in the males, and much, much smaller in females.  So if these trilobite horns really were tools used for the “combat” form of sexual selection (the other form, as pointed out by Darwin, is female preference), the females should be around but lack the ornaments. Where are they?

Gislick and Fortey suggest that the females were indeed around, but because they lack the tridents they have not been identified as females of Walliserops trifurcata:

Since the diagnostic synapomorphy [JAC: shared derived trait] for Walliserops is the anterior trident, it would be likely that the female of the species has been classified in a different genus. That leaves two possibilities: either the females of the relevant species are at present unknown, or they are known but placed in another trilobite genus within Asteropyginae.

That mandates a search for trilobites that resemble the males but lack the horns.  The authors raise another possibility: the females weren’t preserved or were offstage, living elsewhere, but this seems less likely:

If we extend the beetle analogy further, it is possible that the females are not preserved if some trilobites, like many dynastines, engaged in sex-specific aggregations; in this case, the females were not always present in the same locations as the males, although it is difficult to explain why the latter were selectively caught up in obrution events. [JAC: “Obrution” is rapid burial in the sediments, the way these creatures must have died and been preserved.]

I favor the “females not yet found” hypothesis. There’s one more hypothesis, which is mine: both males and females have tridents.  I don’t know why this would be the case, although you could think that it’s used to take other individuals out of action in conspecific competition for food. But that makes little sense.

Finally, the authors found one example of W. trifurcatus with a deformed trident, having an extra spike (a “quadent”?). Here it is on the right. Note that the branching pattern can be asymmetrical in the normal three-pronged structure).

Examples of branching patterns for the middle tines in W. trifurcatus; A. left branching (HMNS 2020-001); B. right branching (HMNS PI 1810); C. teratological example (HMNS PI 1811) showing a secondary branching of the left-branching middle tine. Images taken from photogrammetric models. (Scale bar, 10 mm.)

Because the individual on the right was an adult, Gishlick and Fortey suggest that the deformed structure did not prevent the bearer from growing up and thriving, and thus was unlikely to be used for some vital function like feeding. This adds a little more weight to the sexual-selection hypothesis.

The Upshot:  The authors’ analyses and explanations seem plausible to me, though they’d be even stronger if they could find the females. That might be tough: in living species you could find them by looking at mating pairs or even seeing that the DNA was nearly identical, but this isn’t possible with fossilized trilobites, especially because in some living and sexually dimorphic species the females look very different from males.  If the authors are right, and I think they are, then this quote from the paper is correct:

Walliserops provides the earliest example in the fossil record of combat behavior, very likely ritualized in competition for mates. Although fossil life habits are difficult to prove, the consilience of morphology, teratology, and biometric data all point to the same interpretation, making it one of the more robust examples of paleoecological speculation.

h/t: Matthew

_________________

Gishlick, A. D. and R. A. Fortey. 2023. Trilobite tridents demonstrate sexual combat 400 Mya. Proc. Nat. Acad. Sci. USA 120 (4) e2119970120 (in press).

Readers’ wildlife photos

January 17, 2023 • 8:15 am

Today’s photos are a batch of microorganisms and small creatures sent in by reader Mary Rasmussen. Her captions and narrative are indented, and you can enlarge the photos by clicking on them.

If there’s water, there’s probably something living in it.

I collected a half gallon of water, muck, detritus, rocks, a tiny aquatic plant and 3 snails from some very shallow temporary pools along the Lake Michigan shore. Lake Michigan’s depth varies year-to-year. The pools sometimes last a few years and sometimes just a few weeks. This year the lake level was down and the pools dried up by the end of summer.

I put the water etc. in a 12 inch square glass aquarium with an L.E.D. light on top. These are the creatures living in the water that I was able to photograph.

The last 2 photos are Seed Shrimp that were living in 2 inches of water that had collected in a truck rut in a gravel road.

Aquatic Sowbugs (order: Isopoda) a freshwater crustacean, lived at the bottom of the tank, feeding on organic matter.

Two Hydra (phylum Cnidaria, class Hydrozoa, genus Hydra) After a month there were many of these predators in the tank. I could watch them for hours.

Hydra don’t show any signs of deteriorating with age, and there is speculation that they may be immortal. (I’m sorry but I can’t identify that creature on the left.)

Hydra with bud. The bud is a clone of the parent and will break free when mature.

A freshwater snail laid a trail of eggs on the aquarium wall. These are close to hatching.

Male Cyclops (Cyclops bicuspidatus), the dominant cyclopoid species in Lake Michigan has a single red eye.

Female Cyclops carrying two egg sacs.

Seed Shrimps (subphylum Crustacea, class Ostracoda) have a hard shell and use their antennae to move through the water. These were barely visible in the water of a truck rut.

I used a Nikon D500 camera with three off-camera flashes. For larger creatures (Sowbug, Hydra) I used a Nikkor 105mm macro lens with extension tubes. For smaller creatures (snail eggs, Cyclops, See Shrimp) I used a Laowa 25mm f/2.8 2.5-5X Ultra Macro lens with extension tubes.

 

Readers’ wildlife photos

August 10, 2022 • 8:00 am

Today’s batch of photos come from Costa Rica, and were taken by Fred Dyer. His notes and captions are indented, and you can enlarge the photos by clicking on them:

Some Photos from Costa Rica 10-20 July 2022

I recently traveled around Costa Rica with my family for about 10 days prior to a conference.  Our itinerary included a day in the capital city of San Jose, a couple of days in the mountainous/volcanic region northwest of San Jose, and then several days along the central Pacific coast. Costa Rica is an amazing place, geologically, biologically, and culturally.  Almost everything you see is beautiful.  These photographs are a grab bag that don’t have much in common except that they were the ones that came out looking pretty good.

First, a few photos from near the town of La Fortuna and the Arenal volcano, including from a guided walk through a private rainforest reserve.  On the walk we saw toucans, howler monkeys, army ants, leaf cutter ants and morpho butterflies, plus these (I welcome corrections on the species identifications):

Python Millipede (Nyssodesmus python). This one was about 8 cm long.

Eyelash pit viper (Bothriechis schlegelii), which gets its common name from the hairlike scales protruding over each eye. It is a small snake, but one of the most dangerous in Costa Rica.

Stingless bees (Apidae : Apinae : Meloponini: Perhaps Tetragonisca sp?) guarding their nest entrance tube. There are something like 60 species of stingless bees in Costa Rica. These guard bees were 4-5 mm in length. The colony is enclosed in a cavity so its size is hard to know, but some species have several thousand workers in each colony.

View of the Arenal Volcano from the north. This volcano began erupting violently in 1968 and continued until 2010. Vapors still issue from the peak, although this picture shows only clouds:

Golden-bellied Flycatchers (Myiodynastes hemichrysus) perching behind our rental house in El Castillo (south of Arenal):

From La Fortuna/Arenal we drove toward the Pacific coast, and stopped at a wildlife rescue center (Santuario Las Palmas) near the town of Cañas in Guanacaste province.  The enclosures held rescued jaguars, pumas, ocelots, monkeys and several species of parrots.  We also spotted some wildlife outside the enclosures:

Automeris metzli caterpillar (larva of a Saturniid moth—in the same genus as the North American Io moth). This beauty was about 10 cm long

Same caterpillar after it moved onto a twig. The urticating spines supposedly produce a nasty venom. Here is what an adult Automeris metzli looks like. Whereas the larva relies upon aposematic signals and spines to deter potential predators from attacking, the adult is cryptic in the resting position, and exposes eyespots as a startle cue.
You can read more on Automeris here.

Black Ctenosaur (Ctenosaura similis), also known as the black spiny-tailed iguana, grazing at Las Palmas. These large lizards are extremely common along the Pacific slope:

On the coast our home base was the resort town of Manuel Antonio, which is next to the wonderful Manuel Antonio National Park.

Ponies for the tourists:

In Manuel Antonio National Park, stingless bees (species unknown) on a Heliconia sp.:

Also in the park, Panamanian white-faced capuchins (Capuchin imitator) engaged in a groomfest, while baby looks on. These were part of a larger group of a dozen or so monkeys in a grove of trees about 3 meters above the ground:

Same monkeys, still grooming.

Back in town, a Groove-billed Ani (Crotophaga sulcirostris) with some insect yumminess for its nestling(s). These are large birds (a bit bigger than a grackle) in the cuckoo family.  They often nest communally but this seemed to be a single mated pair.  The nest was in a tree across the street from our rental house in Manuel Antonio. Pictures of the nestling(s) and the other parent didn’t come out so great.

Playa Hermosa, a black-sand beach about an hour north of Manuel Antonio. This is a destination for expert surfers, and the surf was really intense the day we were there.

American Crocodiles (Crocodylus acutus) basking next to the Tárcoles River below the “Crocodile Bridge.” This is a tourist attraction on the main coastal highway (Route 34). The travel guidebook said that there is a population of 2000 or more crocs in this river and the nearby Carara National Park. Crocodiles often rest with their mouths open to dissipate heat.

Readers’ wildlife photos

June 13, 2022 • 8:00 am

Send in your photos lest this feature die!

Today’s photos come from reader Mark Sturtevant, specialist in arthropod photography. His IDs and text are indented, and you can enlarge his photos by clicking on them.

Here are more pictures taken in 2020.

One day while hiking in the woods, a large flying beetle made a noisy passage across the trail. I managed to knock it down. This is Osmoderma scabra, and it’s only slightly smaller than a walnut. 

After a few minutes it had enough, popped out its wings, and lumbered away through the air:

I recently showed a group of strange insects called bark lice. They’re in the same order as parasitic lice, but bark lice are more into feeding on lichens and algae. Some bark lice have wings; here is a handsome example of one. It is Cerastipsocus venosus

Bark lice are pretty alert and fast. But evidently the one shown in the next picture was not quite fast enough. Based on some details like the relative length of the legs, my guess is that the spider is one of the running crab spiders (species unknown). It was quickly hauling its prey along the twig. 

An extremely common visitor to our porch lights is this lovely little Geometrid moth known as the green pugPasiphila rectangulata. Cherry trees are one of their host plants, and we do have one, probably explaining why I see them so often. 

Let’s stay with the Lepidoptera. Next is a lovely Virginia ctenucha moth (Ctenucha virginica), a species found along wood margins. They resemble the closely related yellow-collared scape moth that frequents fields, and together they are part of an extensive mimicry complex that includes several orders of insects. Some members of the complex are distasteful, or they sting, and others are imposters. 

Next up is a caterpillar that was clearly preparing to form a chrysalis. Spiny caterpillars can be hard to identify, but I kept this one and it later emerged as a grey comma butterfly (Polygonia progne). 

And next is that same butterfly with recently expanded wings after emerging from its chrysalis. The reason for its common name is because of the comma-shaped mark on the underside of the wings. The upper side of their wings are mostly orange, but they spend much time sitting with wings closed on the ground among the dead leaves. In this circumstance, they are nearly impossible to see! 

Next up is a little planthopper called Acanalonia conica. These cute little insects are amusing to photograph, because when they realize they are being watched they deviously move to the back of the twig. The trick then is to extend a finger behind the twig, and that makes them sidle back out to sit in plain view. 

The house centipede (Scutigera coleoptrata) is a fairly cosmopolitan species that favors living in houses. As a result, many people know what it’s like to live with house centipedes. Let’s see. . . they attain a size that makes them a bit unnerving, they move fast, and they do have a tendency to suddenly dart out across a wall while you’ve settled down for the evening. I think that about covers it. Folks who live with house centipedes always have strong opinions about them, although they really cause no problems.

Here are some photographs of one that are actually focus-stacked from dozens of pictures taken during a staged setting on the dining room table. Lights were kept off, save for a lamp, and that helped keep it calm. Even so, I am rather surprised this even worked. A few times it did zip away into the dark surroundings, and it was challenging to find again. 

Thank you for looking! 

Readers’ wildlife photos

May 26, 2022 • 8:00 am

Today’s batch comes from regular Tony Eales from Queensland.  His notes and IDs are indented, and you can click on the photos to enlarge them.

One of my favourite habitats is leaf litter, I think because it is often overlooked by the general public unless you’re a little kid. Something about lying down in the dirt, watching what is going on brings back my childhood wonder at the variety of life all around us.

So here’s a random selection of leaf litter denizens from around Brisbane Queensland.

First a common little jumping spider called Bianor maculatus. These spiders live in open grass and leaf litter. I was out one day hunting for Peacock Jumping Spiders (Maratus sp.) but all I found was dozens of these little guys.

What they lack in colour they make up for in their charming way of constantly being on the move and waving their forelegs around like antenna. To me this seems to be the first steps towards ant-mimicry, which is highly advanced in some tribes of jumping spider.

It did this individual no good however because shortly after I took this shot it was nabbed and consumed by a wolf spider.

This strange beast is a Short-tailed Whip Scorpion, which is a small order of arachnids called Schizomida. There are only fewer than 250 described species and externally they are all very similar. Generally, the largest are 5-6mm long and are found in humid tropical and subtropical leaflitter and soil in Africa, Australia, Asia and the Americas. The most common genus in Australia is Brignolizomus and that’s likely what this one is.

They have no eyes, but are active predators using their antenna-form forelimbs to find and investigate prey and their relatively large pedipalps to seize, subdue and grind up their victims.

Another strange beast that is common in the litter is millipedes in the Bristle Millipede order Polyxenida. Probably Polyxenus sp.

And I always love finding these blue-legged beauties hunting through the sticks and leaves. Rhysida nuda, the Northern Blue-Legged centipede.

The leaf litter in Australia is the kingdom of ants. It’s nearly impossible to find anywhere without several species. This is a large Camponotus sp. that I’ve yet to identify.

This ant is perhaps my favourite but they are extremely difficult to photograph as they are always on the move. It is one of the so-called spider ants, Leptomyrmex rothneyi, found in subtropical rainforest leaf litter.

And another favourite is the Painted Strobe Ant, Opisthopsis pictus. These are less common in my area and tend to be in the drier open forests to the north and west. They have an odd stuttering gait that appears to be to confuse predators. It has been observed that they never walk with their strobe gait when inside their nests, only when out in the open.

The subtropical rainforest near where I live has plenty of species of snail but this one is the most spectacular. This is the Giant Panda Snail (Hedleyella falconeri). They are leaf litter specialists and are never found more than half a metre above the ground—unlike many of the other snails that regularly feed on the trunks and leaves of trees.

This is unsurprising given that an adult snail is the size of a tennis ball and a fall from any great height would be potentially fatal. They are under threat from collectors and the pet trade. They are almost impossible to keep in captivity as they require a high humidity and a thriving population of particular fungi on which to feed. Hence many are captured only to die in peoples’ vivariums.

Leaf litter in the open eucalyptus forest has many species of small orthoptera and this is one of my favourites. Macrotona mjobergi the Handsome Macrotona. Macrotona is a genus of spur-throated locusts mostly from Australia often associated with spinifex grasses.

Other common Hymenopterans in the leaf litter are various parasitoid wasps, the most common being velvet ants (Mutilidae), which is what I thought this was at first. However, as it turns out, this is Myrmecomimesis sp., a member of the cuckoo wasp family Chrysididae. Unlike many other cuckoo wasps (but like Mutilids), the females are wingless and spend their time hunting for Phasmid eggs in which to lay their eggs.

Phasmids in Australia produce seed-like eggs that are dropped into the leaf litter. Some have a part to the egg that is meant to be eaten by ants, who take the eggs into the nest where they develop in safety. These wasps run around manically tapping everything with their antenna looking for these eggs before the ants take them.

Another predator, this tiny Carabid beetle, Scopodes sp. hunting through for tiny prey, I’m guessing probably larvae.

One of those potential prey, defending itself with camouflage and silk with leaf-plate armour. One of the case moths in the family Psychidae. Maybe an early instar Lomera sp.

x

 

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?