Archive for the ‘Electron Challenge’ Category

Electron-raster Challenge III: Name this mite

June 28, 2012

Name the family and, for extra fame and fortune, the suppressed seta.

Anyone can play, but this Challenge is posted especially for the students in Acarology Summer Program Soil Acarology course. At least one semi-bingo character is readily visible. The mite is from Alberta, and most prominent in northern forests, but not above an alpine vacation in Mexico. Why swelter in the 100 F Columbus heat, when you can ponder this boreal beasty in over-airconditioned discomfort at your own computer screen.


Electron-raster Challenge II: Name this mite

June 16, 2012

A species name may be a nomen nudum, maybe not, but again genus is probably possible to guess and suborder certainly is

Posting at macromite isn’t what you might call a regular occurrence, but all work and no play makes for a dull life. So here, in quick succession, are the bug blogger’s first choice when time and energy lag: an identification challenge. In this case both are cropped and both are mites. After that you are on your own.

Electron-raster Challenge: Mystery mite

June 16, 2012

Mystery mite

Don’t try for species, that would be a nomen nudum, but genus is doable

Photons to the Rescue: Hintorama on Photo-Electron Challenge

May 28, 2011

Ex Ips pini and once the same genus as the Challenge

Ted MacRae at Beetles in the Bush once complained that my Challenges are too tough, but his Close Crop Challenges are even worse, IMEO (in my exalted opinion). Well, I just took the plunge at his latest Challenge, so anyone misguessing here can laugh at my answer there. It’s all part of the learning process and the more we learn, the less mistakes we will make in the future (or at least this is the theory).

Hi, I'm back and bode ill for beetles

So far, the fearless Kaitlin has been the only one to venture a guess. Her logic is impeccable, but the premise is false. Given the miserably blurry picture of the larva, that isn’t too surprising. I think I will give this one away and show the adults associated with the mitey larva. I may be making a false assumption here too – the larvae and adults occurred together in the rotting mushroom, but that is only weak inference.

What are we?

Pygmephoridae is a good guess for the mite, this is a member of the Heterostigmatina, so one point for Kaitlin, but not of the Pygmephoroidea. All the pygmephoroids that I am familiar with have a more or less distinct gnathosoma, but this mite seems very withdrawn. Here’s a hint – these mites will not harm the larva, but bode ill for its future fitness. At the head of the post is a mite related to the Challenge mite, once it belonged to the same genus, but now it does not. Below is the actual mite itself.

Lightmicrograph of mystery mite

New Photo-Electron Challenge & Old Answers

May 14, 2011

What is my secret name and what do I want from life?

‘To-morrow, and to-morrow, and to-morrow, Creeps in this petty pace from day to day’, but at last the the tomorrow promised in the last post (in March no less) has finally arrived. I plead overwork – I’ve had two massive taxonomic projects to complete including a listing of all of the species of mites known from Alberta – before the new field season commences.  Above is one of these little monsters saying high and below are a number of them clinging to an insect collected from a rotting oyster mushroom (Pleurotus ostreatus). Any guesses to the mite, insect, spores, ecological interactions?

Mites & insect - name them both and what is happening.


I’m fairly pleased in how well everyone did in the first Photon Challenge, especially considering the quality of the pictures.  Ray even got the fly to genus and Kaitlin got pretty close to the family of the mesostigmatan – at least according to the Manual of Acarology 3rd Edition the Halolaelapidae belongs in the Rhodacaroidea and they certainly are phoretic as deutonymphs, as one would expect in that superfamily. So Kaitlin gets points for that. Bruce got the family, and, I believe, the genus correct, at least in the broad sense: Halolaelaps s.l.  Bruce has the advantage of having described the only known Australia species of the group and to have pointed out how messy the generic concepts are (see Halliday 2008 Systematic & Applied Acarology 13, 214–230). I am neutral on what superfamily Halolaelapidae belongs to – Rhodacaroidea is unlikely to be monophyletic and deutonymphal phoresy is probably a ‘primitive’ behaviour in Mesostigmata.

Deutonymph of Myianoetus - note bifurcate claws

Alas, no one guessed the genus of the histiostomatid – Myianoetus! All acarologists should know this genus if only because it contains one of the few mites to lurk among the pages (as an anoetid) of  a large circulation, general science magazine – Science itself – and the interesting concept of ‘fly factors’:

Greenberg & Carpenter (1960) Factors in Phoretic Association of a Mite and Fly. Science 132: 738-739.

“Abstract: Combined rearing of the mite Myianoetus muscarum (L.), and the fly Muscina stabulans (Fall.) has revealed adaptations of the hypopus to a series of fly factors. These adaptations favor the mite’s dispersal. Hypopi are attracted to the pupa by a volatile substance and cluster on the anterior end, from which the fly emerges.”

Read the whole thing, as they say, but, although published over 50 years ago, you will still need access to Science to do so (and to read the next paper entitled  ‘Licking Rates of Albino Rats’). Rat licking trailer aside, I think the most interesting thing about the Myianoetus paper is that I can’t remember any follow-ups that explain ‘fly factor’ or ‘beetle factor’ or ‘ant factor’. Most of the chemical clues used to induce or terminate phoretic behaviour in mites remain unknown. Only skatoles and dung beetles come to mind. If someone out there in the ether knows of other studies, please let me know – I can use the information to help a student.

And the Answer is: Polyxenid Millipede

December 16, 2010

the presentable part of a polyxenid from Queensland

As Christopher Taylor deduced, the 3rd Electron Challenge is none other than a member of the millipede subclass Penicillata and its only order Polyxenida. The cephalic trichobothria and disaggregated eye cups are characteristic of this group. Müller et al. (2007) consider the eyes to be secondarily reduced, miniaturized ommatidia and used their study of eye ultrastructure to argue both for the homology of all mandibulate eyes and a possible synapomorphy of the Myriapoda (millipedes, centipedes, symphylans, and pauropods).

Polyxenid in the courtyard: tiny, but not defenceless

Christopher also hypothesizes that parthenogenesis may help them to colonize extreme habitats like the Spanish Moss (the lichen-like bromeliad Tillandsia usneoides) that dangles from trees, especially live oaks, in the south eastern USA. Some populations of species of Polyxenus, at least, are parthenogenetic, so I suppose, that is a possibility under the General Purpose Genotype Hypothesis about the persistence of parthenogens. But, both bisexual and unisexual polyxenids are unusual among Diplopoda in that many inhabit xeric environments such as rock surfaces, bark, and even Spanish Moss (Whitaker & Ruckdeschel 2010). Wright & Westh (2006) recently demonstrated that Polyxenus lagurus (L.) is capable of absorbing atmospheric water vapour down to relative humidities of 85% – so far the only known millipede to have this ability. So, this ability seems more useful for climbing trees than the ability to do without males.

Our somewhat deformed specimen is from Queensland. Three families of Polyxenida have been recorded in Australia (Lophoproctidae Silvestri, 1897; Polyxenidae Lucas, 1840; Synxenidae Silvestri, 1923), but I don’t know which one this Queensland specimen represents. Unlike all other millipedes, polyxenids (this ‘common name’ could be confusing since it can be applied both to the family and order – but I’ll use it for the order) are soft-bodied and preserving them for SEM is tricky (also the setae, especially in the posterior pencil-like tuft, fall out and get stuck to everything else in the dish). Only about 160 polyxenid species are known today, but the group is very ancient with fossils in amber known from the late Cretaceous – and all have the whorls of serrate setae and the dense pencil-like tuft of fine setae on the rear.

Eisner et al. (1996) have a fascinating (and currently freely available) paper in the unfortunately acronymned PNAS that demonstrates that a North American species of Polyxenus uses the pencil tufts of modified setae on their posterior to thwart predation by ants. In fact, they use the ant’s mechanoreceptor setae and grooming behaviour as a death trap. When an ant approaches, the polyxenid swings its butt around and brushes the tuft of setae against the ant. Grappling hook-like processes on their tips (see the excellent SEMs in the paper)  snare setae on the ants mouthparts and legs and are shed as the millipede moves away. When the befouled ant attempts to clean itself the jagged-edged bristles become entangled and an elaborate snare begins to envelop the ant’s legs and mouthparts, often resulting in the eventual death of the ant (at least in the lab).

The whorls of setae on the body lack the grappling hook ends, but easily fall off and may provide a similar, last ditch defence against being grabbed by a predator and allow the polyxenid a chance to bring its death brush to bear. Polyxenid fossils are only known from the late Cretaceous and Polyxenus from the Eocene (Nguyen Duy-Jacquemin & Azar 2004), so this behaviour may have evolved in response to ants, but millipedes seem to have originated by at least the mid Ordovician and the Polydesmida are either the sister group to all other millipedes or, at the latest, originated in the Carboniferous (Wilson 2006), so this defence may be more than just a myrmicide. Also, not all ants let polyxenids entangle them.

Neotropical ants of the genus Thaumatomyrmex (they feign death when disturbed) hunt the polyxenids abundant in leaf litter (Brandão et al. 1991). A polyxenid is seized by the ant’s antennae, snapped by the wicked-looking mandibles, and then stung and carried back to the nest. In the nest the paralyzed polyxenid is turned belly up and stripped of its setae using the fore tarsi which have “small but stout setae” (perhaps too stout to be engaged by the grappling hooks) and the mandibles. This can take 20 minutes, interrupted by bouts of grooming, so it seems the polyxenid setae may still be fighting back. Brandão et al. thought the setae must have a noxious chemical – this being the normal millipede defence – but Eisner & Deyrup have shown that the morphology of the setae themselves can be fatal and no chemical defence need be invoked. The hunter then eats most of the polyxenid and feeds the remains to a larva.

Polyxenus Latreille, 1803, seems to have given its name to this strange and ancient group of millipedes, but I’m not sure where ‘Polyxenus’ (‘very or many strange’ or ‘very hospitable’ are two possible translations) comes from. Polyxena, the daughter of King Priam of Troy, who came to such a gruesome end on the pyre of Achilles, would seem to be one possible answer, but ‘Polyxenus’ is not feminine and the animal is not hospitable and anything but a willing victim. Polyxenidas was a renegade Rhodian admiral known mainly for treachery and losing naval battles to the Romans, but there is nothing marine or ship-like about these dry-adapted animals (although they may be found on beaches). I think it must be the many strange setae that inspired Latreille and that seems very fitting.

Short Bibliography

Brandão, C. R. F., Diniz, J. L. M. & Tomotake, E. M. (1991) Thaumatomyrmex strips millipedes for prey: a novel predatory behaviour in ants, and the first case of sympatry in the genus (Hymenoptera: Formicidae). Insectes Sociaux 38: 335-344.

Eisner, T., M. Eisner and M. Deyrup. 1996. Millipede defense: use of detachable bristles to entangle ants. Proceedings of the National Academy of Sciences 93: 10848–10851.

Müller CHG, Sombke A & Rosenberg 2007. The fine structure of the eyes of some bristly millipedes (Penicillata, Diplopoda): Additional support for the homology of mandibulate ommatidia. J. Arthropod Structure & Development 36: 463-476

Nguyen Duy-Jacquemin M. & Azar D. 2004. — The oldest records of Polyxenida (Myriapoda, Diplopoda): new discoveries from the Cretaceous ambers of Lebanon and France. Geodiversitas 26 (4) : 631-641.

Nguyen Duy-Jacquemin, M., and J.-J. Geoffroy. 2003. A revised comprehensive checklist, relational database, and taxonomic system of reference for the bristly millipedes of the world (Diplopoda, Polyxenida). African Invertebrates. 44(1):89-101.

Whitaker JO Jr & Ruckdeschel C. 2010. Spanish Moss, the Unfinished Chigger Story. Southeastern Naturalist 9:85-94.

Wilson HM. 2006. Juliformian millipedes from the Lower Devonian of Euramerica: implications for the timing of millipede cladogenesis in the Paleozoic. J. Paleont. 80: 638–649

Wright JC & Westh P. 2006. Water vapour absorption in the penicillate millipede Polyxenus lagurus (Diplopoda: Penicillata: Polyxenida): microcalorimetric analysis of uptake kinetics. The Journal of Experimental Biology 209: 2486-2494.

A long and more normal millipede:

A more traditional Australian millipede

3rd Electron Raster Challenge – Hint

December 12, 2010

Here's a hint - diagnostic character is visible

Hmm, I’m surprised no one has guessed this one. I wonder if everyone is busy shoveling snow? I would be myself, except a neighbour did my driveway for me, so we can do our food shopping this morning with no hassle. Since my neighbour was so kind, I’ll pass it along as a hint: a diagnostic character for the class this animal belongs to is visible in the new image (and the orientation is more realistic).


Macromite’s 3rd Electron Raster Challenge

December 7, 2010

Now that I’m back in the groove, more or less, I suppose I should offer up a new Electron Raster Challenge. This is an easy one, these things are everywhere, so for full credit, how about naming three of the structures visible too. In case anyone needs a hint or two, well, they are unusual  among their close relatives for two reasons that I can think of:  (1) they have a physiological ability that allows them to live in Spanish Moss and (2) they use their morphology to confound ants. Extra credit for explaining these two feats.

Macromite’s Second Electron Challenge

July 4, 2010

Rainforest Electron Raster Mystery with Blobs

I spent my lunch break one day this week talking ant mites and looking over the amazingly diverse collection of laelapid mites that formed a significant subset of the 200 mite species that a graduate student has found on Ohio ants over the last few years. The conversation drifted to bug blogs and the usual adulation that one hears for Alex Wild from the ant-infatuated. Of course, I asked why would an mymecoacarophile mention Myrmecos before macromite? After the usual gushing about all the wonderful things on Myrmecos, this student pointed out that ‘Well, you don’t post very often you know.’

Point taken and given that I’ve been stuck in this bloody airport for the last 8 hours and it may be as long again before I’m home, might as well do some of that not very often blogging.

Here’s the second macromite challenge: what is it and what are those blobs on the outside? As a few clues to get you started I’ll tell you that the larger animal is terrestrial and not uncommon in soil and litter on the floor of subtropical rainforest in southeastern Queensland. The first time I saw one of these crawling across the floor of a live extraction container I was flummoxed and then amazed. But amazement and the Australian fauna are never too far apart.