Legs I and II have long ambulacral stalks, and there are rows of jagged denticles on its dorsum.

The denticles are reminiscent of the dorsal integument of sarcoptid mites (e.g., Sarcoptes scabiei), but sarcoptids are restricted to mammals. Had the cowbird accidentally acquired a mange mite from a cow that it had perched on? That would be odd but not impossible. On the other hand, birds do have their own types of ‘mange’ mites from a different family. Scaly-leg mites in the epidermoptid subfamily Knemidokoptinae* can cause crusty growths on the legs and around the beaks of their hosts. But all the knemidokoptines that I’ve seen have been adult females, which have very stubby legs and lack dorsal denticles. The images below show the foot of an afflicted grosbeak and a female Knemidokoptes** from its scabby toes.

So, I scoured my med-vet entomology texts and Google-Scholared in search of illustrations of larval knemidocoptines. After much searching I had found only blurry photos and a solitary drawing of the amulacral stalk of a Knemidokoptes larva. But the stalk was long and thin, like that of the mite Hannah had mounted. At that point I decided it was time to ask someone who would know whether it was a stray sarcoptid: Hans Klompen from Ohio State University, whose Ph.D. thesis was on phylogenetic relationships within the Sarcoptidae. I sent Hans some photos and quickly heard back from him that (a) it was not a sarcoptid larva and (b) that he recognized it as a larval Knemidokoptes – hurrah! I hope that this post will help others avoid taxonomic frustration should they also come across these odd little mites.

*Previously a separate family, Knemidokoptidae.

**Also spelled as Knemidocoptes and Cnemidocoptes in the literature. GBIF indicates that the ‘-koptes’ spelling is the senior synonym.

(top two photos by Hannah Stormer, bottom two by Heather Proctor)

Two eggs on a squirrel hair, one occupied.

Close-up of one embryo popping out of the egg.

Nymphal sucking louse, Neohaematopinus sciuri.

Internal mouthparts of the nymph.

Tarsus of second leg showing faint scalloped structure.

A nice scaly patch of integument from the dorsum of the nymph.

Adult female Neohaematopinus sciuri.

Relative sizes of tarsal claws of legs I to III and shape of the sternal sclerite (arrow) helped to identify the female as belonging to the family Polyplacidae and the genus Neohaematopinus.

References

Kim, K.C. 1966. The species of Enderleinellus (Anoplura, Hoplopleuridae) parasitic on the Sciurini and Tamiasciurini. J. Parasitol. 52: 988-1024

Kim, K.C. 1966 The nymphal stages of three North American species of the genu Enderleinellus Fahrenholz (Anoplura: Hoplopleuridae). J. Med. Ent. 2: 327-330.

Kim, K.C., H.D. Pratt and C.J. Stojanovich. 1986. The Sucking Lice of North America: an Illustrated Manual for Identification. Pennsylvania State University Press, University Park.

Protomyobia nr. claparedei female (note egg).

Protomyobia nr. claparedei male (note well-sclerotized aedeagus).

Larval Protomyobia nr. claparedei (note styletiform chelicerae).

Ventral view of one of the many pygmephorids from the shrew washings.

Pygmephorid showing modified legs I.

Dorsal view of a shrew chigger (Trombiculidae).

Prodorsal shield of a shrew chigger, showing the posterior pair of trichobothria and single anterior median seta (just the base can be seen here) indicative of the family Trombiculidae, as opposed to members of the Leeuwenhoekiidae, which have two anterior median setae.

An Oryctoxenus sp. deutonymph (Glycyphagidae). Anterior is pointing up, and yes, it doesn’t have mouthparts.

Posterior hair-clasping structures of an Oryctoxenus deutonymph.

A larval hard tick (Ixodidae).

Retrorse spines on the tick’s hypostome help keep it attached to the host.

Maybe a female Proctolaelaps sp.(Melicharidae). Not in great shape.

The ‘procto’ part of Proctolaelaps refers to the large anal opening, or so the etymological legend goes.

*Smith, H.C. 1993. Alberta Mammals: an Atlas and Guide. The Provincial Museum of Alberta, Edmonton, Alberta.

Like Varroa, Euvarroa are very large, heavily sclerotized mites. The ones that Geoff sent were 1 mm long: five Notoedres from a mangy squirrel skin could lie nose-to-tail on the venter of one Euvarroa.

Euvarroa sinhai is a big mite, shown here with a 200 um long Notoedres for scale.

There are two named species in the genus Euvarroa, E. sinhai Delfinado & Baker and E. wongsirii Lekprayoon & Tangkanasing. Euvarroa sinhai is associated with Apis florea, whereas E. wongsirii is found on A. andreniformis Smith.  The species differ in general body shape (very triangular for E. wongsirii) and length:width ratio for the anal plate (longer than wide in E. sinhai, the opposite for E. wongsirii)*. Based on these host and morphological features, the mites from Geoff are E. sinhai.

I don’t think that much is known of the biology of either Euvarroa species, but they are very spiffy-looking mites. Here are some closer views of parts of their anatomy.

The bee-piercing chelicerae of Euvarroa sinhai.

Euvarroa sinhai‘s u-shaped peritreme; stigma to the upper left.

“My, what big ambulacra you have!” “All the better for holding onto bees, my dear.”

*Lekprayoon, C. and P. Tangkanasing. 1991. Euvarroa wongsirii, a new species of bee mite from Thailand. International Journal of Acarology 17: 255–258.

Diagnosis and drawings of Notoedres centrifera from Klompen (1992).

Jamie had only histological sections through mangy squirrel skin, though, which are difficult to match to species descriptions. I said sure and soon received a small frozen chunk of integument via courier. The skin sat in a saturated KOH solution for a couple of days to encourage its dissolution. The single mite I managed to find in the smelly skin slurry matched Klompen’s illustrations of N. centrifera (above), and was a similar size (200 um).

Ventral view of the sarcoptid mite I found in the squirrel slurry.

Dorsal view of same.

So, diagnosis confirmed, end of story, right? Well, actually, the mite isn’t the reason for the ‘mystery’ in the title of this post. In addition to the one tiny Notoedres, I found several almost as miniscule (600 um), translucent cigar-shaped objects in the digested squirrel skin. Out of curiosity, I mounted three of them yesterday. [UPDATE: I revisited the slurry and found a fourth critter, images of which are at the bottom of the post]. Today I spent several hours futilely trying to pin them down to a taxon finer than ‘probably some sort of arthropod’. My first thought as I mounted them was follicle mites (Demodicidae) in cysts, but nope, not enough legs. There seem to be only two pairs! Plus they end in single large claws or clawlike tarsi, whereas follicle mites have two small claws per leg. Embryonic insects in eggshells? Still not enough legs, unless the first pair develop much more slowly than the last ones. Maybe…see third photo below. What insects might be on squirrels? The critters don’t look much like lice, because to my knowledge no lice have a big tuft of bum setae. And what are those weird flash-shaped setae at the head end? Are those round things spiracles? And why is there scalloped ornamentation on the bases of the four well-developed legs? None of the many entomology texts I consulted had images at all similar to these.

Ventral view of one of the four-legged embryos (?) from the squirrel skin. Note the long whippy bum setae (I assume that’s the bum end).

Lateral view of one of the other embryos.

It looks like there might be another pair of very poorly sclerotized anterior legs, with the faint leg tips clasping on of the more posterior legs.

Flask shaped setae on the head-ish end.

Something that might be an anterior spiracle.

A row of abdominal spiracles?

There’s a fan-shaped structure at the base of each of the sclerotized legs (most clear on second leg from the right). They remind me of the ventromental plates of chironomid larvae.

I managed to mount one of the mystery critters with legs spread out and saw that the fan is actually split, like an open bivalve shell. Note also the trachea.

At the anterior end of the thing are two sets of what look like trichobothrial bases, but there are no trichobothria or other setae coming out of them on any of the four critters that I mounted.

I am thoroughly stumped. Help!

Reference:

Klompen J.S.H. 1992. Phylogenetic Relationships in the Mite Family Sarcoptidae (Acari: Astigmata). Museum of Zoology. Ph.D. thesis, The University of Michigan, Ann Arbor, MI, USA.

Scanning electron micrograph of a Drosophila hydei carrying a female Macrocheles muscaedomesticae (image by HP)

Females of many species of Macrocheles (Mesostigmata: Macrochelidae) hitch rides on winged insects to move from a place to place, a phenomenon called phoresy. Strictly phoretic organisms do not feed on the host while attached. A great many mite taxa fall into this ‘purely phoretic’ category. Others may facultatively snack on the host while in transit. My colleague Lien Luong has investigated one such mite species, Macrocheles subbadius (Berlese), and its cactus-associated host Drosophila nigrospiracula Patterson & Wheeler. When Lien moved to the University of Alberta it proved difficult to replicate the system, in part because cacti are not common in this part of Alberta.  Compost bins are abundant, however, and Lien and her students are investigating the ecological relationship between two compost-associated species, Macrocheles muscaedomesticae and Drosophila hydei. Does M. muscaedomesticae feed on its host while attached, or is it just holding on? One way to test this is to determine whether the mite’s mouthparts pierce the fly’s integument. In this N = 1 sample, the mite just seems to be holding on firmly, probably uncomfortably so from the fly’s point of view.

Piercing or just pinching?

Looks like pinching, probably painfully.

But by definition, facultative parasites aren’t always parasitic. More mites must be examined, and other lines of evidence followed, such as presence of melanized wounds on hosts after the mites have dropped off, or presence of Drosophila DNA in the guts of the Macrocheles.

Fabio is doing some marvelous work on taxonomy and ecology of these mites, including the very recent discovery of a host-switch from wild cuckoos to domestic poultry. But even though he and his colleague Michel Valim have been working hard to describe new species, at least 80% of bird species in Brazil have yet to be investigated for their acarofauna. Many more wonders await.

Click on the poster image then mouse over and click to magnify.

*abakashi@gmail.com

Pteronyssus sphyrapicinus (Astigmata: Pteronyssidae) feather mites from a Yellow-bellied Sapsucker. Male on left, female on right.

When I looked at the louse under the compound scope I thought its Malpighian tubules had burst out of its abdomen. At higher magnification, the tubules turned out to be hyphae.

Fungally infected Penenirmus auritus (Phthiraptera: Philopteridae) from a Yellow-bellied Sapsucker.

I figured it must be a member of the Laboulbeniales, fascinating and highly modified ascomycotan fungi: look here and here! Almost all of the 2000 or so described species are ectoparasites – or perhaps in some cases harmless commensals – of living arthropods. One species has achieved recent notoriety due to its spreading from a native ladybird in the U.K. to an invasive one. I had seen them on various critters before, including beetles and mites, though never on a feather louse. But Googling revealed that in 1951, Wolfdietrich Eichler had published an interesting overview of the Laboulbeniales he’d seen on lice from birds*.

They were all from the genus Trenomyces. I asked my mycologist friend Randy Currah if he could tell whether the fungus on my louse was one that Eichler had identified. He referred me to Meredith Blackwell at Louisiana State University. She identified the images as a Trenomyces sp. (like Eickler’s) and then sent the images I emailed to her to Danny Haelewaters at Harvard University. I’m not sure whether Danny will be able to get it to species based on my bad photos, but if he does I will update. UPDATE (22 Aug 2015) – Danny has just identified the fungus as Trenomyces circinans Thaxter, a new record for Canada. Thanks, Danny!

Closer view of the Trenomyces showing a big ascocarp, two ascospores (lower right) and juvenile multiseptate things that probably have proper names but I will just call ‘babies’.

*Eichler, W. 1951. Laboulbeniales bei Mallophagen und Läusen. Feddes Repertorium. 54(53):185-206.

Based on the last image, some university students believe that spiders should be speared on toothpicks and served in martinis.

*apologies to Facebook friends who’ve already seen a version of this.

At first I thought the pair of round things near the female’s genital area were sperm-storage chambers. But when I Googled ‘Crossocerus’ and ‘Scutacaridae’, I found a paper that showed I was only half right – they were sporothecae*, not spermathecae!

Two big spores tucked into the genital atrium of this female Imparipes.

Ebermann & Hall (2004) described a new species of scutacarid, Imparipes haeseleri, from several species of wood-associated Hymenoptera. In the genital atrium of these mites, they observed two large round fungal spores, one on each side, looking remarkably similar to the ones in the mites from the rotting chair. I asked Evert Lindquist, an expert on the Heterostigmata (the larger group to which Scutacaridae belongs) if these mites were Imparipes. Yup, they were. Were they I. haeseleri? There is a closely related species known from North America, I. vulgaris, but several setal characters matched haeseleri rather than vulgaris so I decided to go with Imparipes cf. haeseleri.

Why are the female mites carrying spores? No doubt they and their offspring feed on the wood-digesting mycelium produced from the germinated spores. The mites that hop on wasps as they depart from their overwintering chambers take with them the starter culture for their future meals. Dr. Lindquist noted that the spores these mites were carrying looked very similar to the Nigrospora spores known to be carried by a different species of heterostigmatan, Siteroptes reniformis Krantz. In his 1984 paper, Lindquist notes that S. reniformis “not only serve to transport and place spores of Nigrospora in an environment favorable for germination and growth, they also stimulate mycelial growth, apparently by secreting a chemical substance when feeding on the fungus.”

The second wasp was collected from an overwintered artificial nesting block that was supposed to house solitary bees. It was an Ancistrocerus sp. (Vespidae: Eumeninae). Knowing this, it was easy to guess who the mites were, and slide-mounting confirmed it: deutonymphs of a Kennethiella sp. (Astigmata: Winterschmidtiidae).

Like almost all phoretic deutonymphs of Astigmata, these Kennethiella have a terminal sucker plate to adhere to hosts. Unusually, they also have anterior ocelli. Why ocelli are present in only a small number of Astigmata is unclear (at least, it’s unclear to me).

Sucker plate.

Pair of ocelli.

The reason I expected the mites to be Kennethiella is because the relationship between them and their host wasps is famous among acarologists. Cowan (1984) unraveled the interactions for one mite-wasp duo.  To quote the abstract: “The mite Kennethiella trisetosa is phoretic on adults of the wasp Ancistrocerus antilope and develops in the nest with immature wasps. Female mites and a large type of male develop oviparously, whereas a small male develops oviparously. Small males kill each other, but are ignored by large males. By mating with females before small males are mature, large males may monopolize fertilization. Larvae of female wasps usually destroy mites within their cells but, as adults, are reinfested when mated by mite-bearing males. Each time a male wasp mates, about half of its mites transfer to the female.”

It’s worth reading the original to appreciate the full intricacies of these intertwined life-cycles.

A home-grown Ancistrocerus with a load of Kennethiella, from my back yard in Edmonton a few years ago.

*according to Evert Lindquist, they aren’t sporothecae (which are spore-storage sacs) but simply the spores themselves, tucked into corners of the genital atrium. Thanks, Evert!