Belongs within: Anystina.
Contains: Microcaeculus, Allocaeculus.
The Caeculidae, rake-legged mites, are a group of large, heavily sclerotised, predatory mites with large spine-like setae on the legs (particularly the first) that are used in the capture of prey.
Meet Australia’s newest rake-legged mite
Published 20 December 2013
Taylor, C. K., N. R. Gunawardene & A. Kinnear. 2013. A new species of Neocaeculus (Acari: Prostigmata: Caeculidae) from Barrow Island, Western Australia, with a checklist of world Caeculidae. Acarologia 53 (4): 439–452.
And, just in time for Christmas, here comes another publication for our lab! The paper is freely available for download, and represents my first foray into the world of mite taxonomy! So let me introduce to you the Barrow Island rake-legged mite, Neocaeculus imperfectus.
One of the most productive methods that we use for our collections on Barrow Island is suction sampling. This is exactly what it sounds like: we run a blower-vac over the vegetation, slurping up any bugs that might be sitting there. This usually provides us with a ton of material relatively quickly. The method’s main caveat is that it provides mostly smaller stuff (larger insects are more likely to fly away before the blower-vac reaches them, or be strong enough to hang onto the vegetation as the vacuum passes over them). You also tend to confuse on-lookers who cannot work out why you are vacuuming the scrub.
So the average suction sample from Barrow Island will contain a lot of micro-wasps, a lot of leafhoppers… and one heck of a lot of one particular species of mite. The entire island seems to be crawling with these guys (or girls, rather: we’ve not yet identified a male, and it seems likely that this species is parthenogenetic). Some samples look to contain specimens numbering in the hundreds.
It might seem surprising for the single most abundant species in a region to also be a completely new species to science, but this is indeed what we found. This particular mite belongs to a family called the Caeculidae, the rake-legged mites. The name refers to the presence of long spines on the front legs of these mites, which they use in capturing prey. Otto (1993) observed live individuals of another species, Microcaeculus pica, and found that they would stand in once place, immobile, with their front legs raised above the ground. When a small animal such as a springtail walked underneath the raised legs, the mite would drop them down, and the spines would act like a cage, trapping the victim. This habit of remaining perfectly still goes some way to explaining another interesting detail about the Barrow Island caeculids: despite their apparent abundance, we’ve never seen them alive in the field (I have occasionally seen one walking about in the lab when sorting samples). Presumably their motionlessness makes them almost invisible.
Caeculids are common in many parts of the world, particularly in arid regions, but they’ve never gotten much love; relatively little has been published on them. A large part of this is that they’re difficult to work with under a microscope, being dark and heavily sclerotised. Their aforementioned crypsis also means that they are often overlooked and may be difficult to collect. The last person to work extensively on caeculids, the now-retired French researcher Yves Coineau, reported that he collected specimens by filling a tray with leaf litter and then blowing tobacco smoke over it to make the mites move (Coineau 1974). This method would probably not be recommended today. Because of the difficulty in finding information on caeculids, we also included in our paper a key to the genera and a complete checklist of the species of the world.
Finally, in case you were wondering, ‘imperfectus‘ is Latin for ‘undeveloped’. Neocaeculus imperfectus is something of an apparently neotenous form compared to other caeculids, with adults retaining a number of juvenile features such as a low number of dorsal setae.
Continued adventures with rake-legged mites
Published 8 October 2014
It’s been a noteworthy couple of weeks here at chez Variety of Life. My contract at the university has reached its end, and I’ve become a Free Agent (‘free’ as in ‘I don’t get paid for any of this stuff’). That bit in the sidebar where I describe myself as “an entomologist working on the identification of terrestrial invertebrates” is, for the nonce, more of an aspiration. Or, to put another way, a lie. And my lunch breaks have gotten a lot more generous. Time will tell how long this state of affairs will continue, but in the meantime, there’s still research to be done and papers to produce. Which segue’s nicely into the subject of today’s post: my newest paper, “Two further Neocaeculus species (Acari: Prostigmata: Caeculidae) from Barrow Island, Western Australia”.
Back in December, I commented on the publication by myself and my colleagues of the rake-legged mite Neocaeculus imperfectus. In the comments for that post, I indicated that N. imperfectus was not the only new rake-legged mite species that I had on hand*. As it turns out, there was a total of five different species of caeculid in our collection (including N. imperfectus). Two of these were species that had already been described by Coineau & Enns (1969), but two more were new. The first of these I have dubbed Neocaeculus kinnearae, after my colleague Adrianne Kinnear, to whom I owe all of my understanding of mites. Adrianne first identified many of the Barrow Island mites, and trained me in mite identification prior to her recent retirement. Neocaeculus kinnearae is very similar to a species originally described from the Kimberley region of northern Western Australia, N. knoepffleri (some of you not familiar with Australian geography may still know the Kimberley as one of the few regions that diamonds come from). The two primarily differ in size (N. kinnearae is distinctly smaller) and while the large leg-spines in N. knoepffleri end in sharp points, those of N. kinnearae are blunter. Interestingly, N. knoepffleri is also present on Barrow Island, which did lead me to wonder if the specimens I ended up assigning to N. kinnearae might be just smaller individuals of N. knoepffleri. But I have seen several specimens of both from Barrow by now, and I’m yet to see any overlap between the two, so I do think that they are both good species.
*You may wonder why, if I knew that there was more than one species present, I didn’t just put them all in the one paper. The reason was that, because I had never prepared a mite taxonomic paper before, I wanted to just do the one species at first as a test run, and then do the others once I felt a bit more confident that I knew what I was doing.
Neocaeculus knoepffleri also has a particular claim on my affections in that I’ve seen it alive. This is a bigger deal than it sounds: caeculids are cryptic and slow-moving, so observing them in the field is notoriously difficult. I already explained in my earlier post how I’ve never seen Neocaeculus imperfectus out and about, despite it turning up in samples in numbers that suggest absolute plagues of the things. But on my last trip to Barrow back in March, we were out collecting at night near the shore when I spotted a small grey point on a grey rock move slightly. Closer inspection revealed a caeculid sitting on the rock with spiny front legs outstretched, in the classic caeculid ambush pose. If I moved my forceps close to it, the mite would turn towards them as if warding them off. Having found one, I looked a bit further, and found several more, all perfectly camouflaged against the rock.
The second new species was the smallest caeculid I had seen from Barrow so far, but was none the less remarkable. For a start, it didn’t have the slender spines on its front legs of other rake-legged mites; instead, the spines were modified into rounded paddles. There are a few other caeculids known to have this feature (one of them, Neocaeculus bornemisszai, is another Kimberley species now also known from Barrow). Where their habits are known, it seems to be an adaptation for digging in sand, something that I can assure you Barrow Island has no shortage of. The other interesting feature of the new species is that the dorsal plates that usually cover the rear half of the body in other caeculids are unusually small. It was the appearance given by these small plates that inspired the name I gave this species: nudonates, from the Latin nudus, naked, and nates, buttocks. This is, literally, the bare-arsed mite.
So Barrow Island is now officially home to five different species of caeculid mite (and shortly after submitting this paper, I came across specimens of a sixth). While only one of these species has actually been observed alive, we can still infer some things about the likely habits of the others. Two, Neocaeculus bornemisszai and N. nudonates, are probably diggers of some sort. They may prefer different substrates: while N. nudonates has the afore-mentioned reduced plates, N. bornemisszai is more heavily armoured than usual. There may be a difference in preferred substrate between N. knoepffleri and N. kinnearae as well, to explain the blunter leg spines of the latter. In the paper, I suggested that N. imperfectus was probably a climber on vegetation, to explain it mostly being found in suction samples while the other species all came from pitfall traps. Since the paper was submitted, I have seen a few N. kinnearae specimens in suction samples, but I still think that it is most likely not a climber because these have been few and far between.
The other main point to be made is that there are probably a lot more caeculids out there than we realise. Though only eight species of caeculid have been recorded from Australia so far, Barrow Island is home to at least six (one of which may or may not be a further undescribed species). Caeculids are generally regarded as associated with warmer, drier habitats, and Australia is almost entirely warmer, drier habitat. I would not be surprised if, once we looked further, we would find a lot more undescribed caeculids out there.
Systematics of Caeculidae
Characters (from Walter et al. 2009): Heavily sclerotised, usually with eight dorsal shields arranged in a characteristic pattern. Cheliceral bases unfused, apparently capable of limited lateral motion; palptibia always with a single, well-defined terminal claw and ancillary subterminal spines; with two pairs of lateral eyes and an anteromedian prodorsal eye associated with a naso. Setal elements of opisthosomatic segment AD present; with three pairs of genital papillae. Legs I with strong, internal spinose setae, tibia and tarsus I each with a solenidion and a vestigial actinopilous seta in an integumental sink. Paired claws on legs usually unequal in size, empodia absent. With prelarval, larval, and three nymphal stases.
<==Caeculidae [Caeculoidea, Hoplopidae, Hoplopini] | i. s.: Calocaeculus Coineau 1974C74 | `--*C. lawrencei Coineau 1974C74 |--Procaeculus Jacot 1936C74 | | i. s.: P. brevis (Mulaik 1945) [=Caeculus brevis]TGK13 | | P. magnus Coineau 1974C74 | | P. mexicanus (Mulaik & Allred 1954) [=Caeculus mexicanus]TGK13 | | P. orchidicolis (Mulaik & Allred 1954) [=Caeculus orchidicolis]TGK13 | | P. oregonus (Mulaik & Allred 1954) [=Caeculus oregonus]TGK13 | | P. potosi (Mulaik & Allred 1954) [=Caeculus potosi]TGK13 | | P. puertoricus (Mulaik 1945) [=Caeculus puertoricus]TGK13 | | P. willmanni (Vitzthum 1933) [=Caeculus willmanni]TGK13 | |--P. coineaui Porta, Proud et al. 2019PP19 | `--+--P. eridanosae Coineau & Magowski 1994PP19, TGK13 | `--+--*P. bryani Jacot 1936C74, PP19, C74 | |--P. aitkeni Coineau 1969PP19 | `--P. dominicensis Coineau & Poinar 2001PP19, TGK13 `--+--+--Caeculus Dufour 1832PP-AR21, TGK13 (see below for synonymy) | | | i. s.: C. fedrae Porta, Michalik & Ramírez 2022PMR22 | | |--C. hirtipes Berlese 1910 (n. d.) [incl. C. hirtipes var. graecus Berlese 1910]TGK13 | | |--C. calechius Mulaik 1945BL20, M45 | | `--+--+--+--C. dorotheae Mulaik 1945BL20, C74 | | | | `--C. janetae Higgins & Mulaik 1957BL20, TGK13 | | | `--+--C. hardyi Mulaik & Allred 1954BL20, TGK13 | | | `--+--C. gertschi Mulaik 1945BL20, TGK13 | | | `--C. hypopachus Mulaik 1945BL20, TGK13 | | `--+--+--C. clavatus Banks 1905BL20, TGK13 | | | `--C. mariae Higgins & Mulaik 1957BL20, TGK13 [=Microcaeculus mariaeP65] | | `--+--C. pettiti Nevin 1943BL20 | | `--+--C. crossleyi Hagan 1985BL20, H85 | | `--+--C. archeri Mulaik 1945BL20, C74 | | `--+--+--C. cremnicolus Enns 1958BL20, H85 | | | `--+--C. krantzi Coineau 1974BL20, C74 | | | `--+--*C. echinipes Dufour 1832TGK13, BL20, TGK13 [=Hoplopus echinipesTGK13] | | | | |--C. e. echinipesC74 | | | | `--C. e. crosbyi Jacot 1936C74 | | | `--C. kerrulius Mulaik 1945BL20, TGK13 | | `--+--C. americanus Banks 1899BL20, TGK13 [=Pseudocaeculus americanusTGK13] | | `--+--C. tipus Mulaik 1945BL20, TGK13 | | `--+--C. valverdius Mulaik 1945BL20, C74 | | `--+--C. cassiopeiae Bernard & Lumley in Bernard, Lumley et al. 2020BL20 | | `--C. lewisi McDaniel & Boe 1990BL20, TGK13 | `--Andocaeculus Coineau 1974PP-AR21, C74 | |--*A. brundini (Franz 1962) [=Microcaeculus brundini]C74 | |--A. beatrizrosso Porta, Pizarro-Araya & Ramírez 2021PP-AR21 | |--A. burmeisteri Porta, Pizarro-Araya & Ramírez 2021PP-AR21 | |--A. caioi Ott & Ott 2014OO14 | |--A. castrii (Franz 1964)PP19 | |--A. nudus (Franz 1964)PP-AR21 | `--A. weyrauchi (Franz 1964) [=Microcaeculus weyrauchi]PP-AR21 `--+--MicrocaeculusTGK13 `--+--AllocaeculusTGK13 `--Neocaeculus Coineau 1967PP19, C74 | i. s.: *N. luxtoni Coineau 1967TGK13 | N. imperfectus Taylor, Gunawardene & Kinnear 2013TGK13 | N. kinnearae Taylor 2014T14 | N. lamorali Coineau 1974C74 | N. nudonates Taylor 2014T14 | N. setecidades Ott & Ott 2018OO18 |--N. bruchi (Berlese 1916)PP19, TGK13 [=Caeculus bruchiTGK13, N. brucki (l. c.)TGK13] `--+--N. johnstoni Coineau 1974PP19, TGK13 |--N. womersleyi Coineau 1974PP19, TGK13 `--+--N. orientalis Fuangarworn & Butcher 2015PP19, FB15 `--+--N. bornemisszai Coineau & Enns 1969PP19, C74 `--N. knoepffleri Coineau & Enns 1969PP19, C74
Caeculus Dufour 1832PP19, TGK13 [=Hoplopus Canestrini & Fanzago 1877TGK13; incl. Pseudocaeculus Coineau 1974 (n. n.)TGK13]
*Type species of generic name indicated
[BL20] Bernard, J., L. M. Lumley, M. Buck & T. P. Cobb. 2020. A new species of rake-legged mite, Caeculus cassiopeiae (Prostigmata, Caeculidae), from Canada and a systematic analysis of its genus. ZooKeys 926: 1–23.
[C74] Coineau, Y. 1974. Éléments pour une monographie morphologique, écologique et biologique des Caeculidae (Acariens). Mémoires du Muséum National d’Histoire Naturelle, nouvelle série, Série A, Zoologie 81: 1–299, 24 pls.
[FB15] Fuangarworn, M., & B. A. Butcher. 2015. Neocaeculus orientalis sp. nov. (Acari, Trombidiformes, Caeculidae) from Thailand. Zootaxa 4048 (2): 251–268.
[H85] Hagan, D. V. 1985. Caeculus crossleyi n. sp. (Acari: Caeculidae) from granite outcrops in Georgia, U.S.A. International Journal of Acarology 11 (4): 241–245.
[M45] Mulaik, S. 1945. New mites in the family Caeculidae. Bulletin of the University of Utah 35 (17): 1–23.
[OO14] Ott, A. P., & R. Ott. 2014. A new species of Andocaeculus (Acari, Caeculidae) from the Pampa biome, southern Brazil. Iheringia, Série Zoologie 104 (3): 355–363.
[OO18] Ott, A. P., & R. Ott. 2018. A new species of rake-legged mite Neocaeculus (Acari, Caeculidae) from Brazilian semiarid and new data on distribution of Andocaeculus caioi. Iheringia, Série Zoologie 108: e2018027.
Otto, J. C. 1993. A new species of Microcaeculus from Australia (Acarina: Caeculidae), with notes on its biology and behavior. International Journal of Acarology 19 (1): 3–13.
[P65] Piffl, E. 1965. Microcaeculus namibensis nov. spec. Ein Vertreter der Caeculiden (Arachnoidea, Acarina) aus der Namibwüste Südwestafrikas. Scientific Papers of the Namib Desert Research Station 28: 1–12.
[PMR22] Porta, A. O., P. Michalik & M. J. Ramírez. 2022. Caeculus fedrae sp. nov., a new fossil species of rake-legged mite (Acari: Caeculidae) from Baltic amber. Acarologia 62 (4): 1154–1170.
[PP-AR21] Porta, A. O., J. Pizarro-Araya & M. J. Ramírez. 2021. Revision and phylogeny of the genus Andocaeculus (Acari: Caeculidae) I: the A. weyrauchi species group. Zootaxa 4945 (1): 1–78.
[PP19] Porta, A. O., D. N. Proud, E. Franchi, W. Porto, M. Bernar-da Epele & P. Michalik. 2019. The first record of caeculid mites from the Cretaceous amber of Myanmar with notes on the phylogeny of the family. Zootaxa 4647 (1): 23–43.
[T14] Taylor, C. K. 2014. Two further Neocaeculus species (Acari: Prostigmata: Caeculidae) from Barrow Island, Western Australia. Acarologia 54 (3): 347–358.
[TGK13] Taylor, C. K., N. R. Gunawardene & A. Kinnear. 2013. A new species of Neocaeculus (Acari: Prostigmata: Caeculidae) from Barrow Island, Western Australia, with a checklist of world Caeculidae. Acarologia 53 (4): 439–452.
Walter, D. E., E. E. Lindquist, I. M. Smith, D. R. Cook & G. W. Krantz. 2009. Order Trombidiformes. In: Krantz, G. W., & D. E. Walter (eds) A Manual of Acarology 3rd ed. pp. 233–420. Texas Tech University Press.