The Macromite Before Christmas

Water-skating Homocaligus adorned with Roynortonella pustules

The winter solstice (adorned with a full lunar eclipse on an almost clear night here in Edmonton) is several days past and my brief Albertan ‘mid-winter’ holiday season has just commenced. In Australia the first month of summer is almost over – Australia begins its summer on the first day of December, presumably out of the usual nonconformity or some other reason that was never clearly explained to me – but their summer solstice is just past and it is also the holiday season (with snow in the mountains, but otherwise warmer than here). Celebrating the longest night of the year makes a certain sense. Although I still have 4-5 months before green returns to the landscape, I can optimistically assume that the sun will be shining longer and longer each day, even if it is on clouds that are dumping snow on me, and eventually the winter will end, at least officially. So, in the spirit of my holiday season, I wish my readers, wherever they are and whatever their holiday or not, a happy Christmas and productive, healthy, and intellectually stimulating New Year.

An undescribed, but checklist making, Annerossella from Queensland

Over the last few years I have gotten into the habit of tarting up one of my mites for a Christmas card. This year I picked an unidentified Albertan species of Homocaligus – one of the two genera of the raphignathoid family Homocaligidae. This mite is a festive bright red in life and skates over the shallow margins of lakes among emergent vegetation and aquatic mosses. Eggs are probably laid on vegetation as in Annerossella knorri Gonzalez, a homocaligid described from the leaves of water lettuce (Pistia stratiotes) near Bangkok, Thailand. I suspect it is a predator, perhaps of the springtails (Podura aquatica) that hop along in this habitat. I once kept an undescribed Australian species of Annerossella in a small aquarium, but other than watching it skate across the water, I was unable to add anything to the knowledge of its ecology (at about 0.5 mm in length, it is difficult to observe). However, I did make one of my early coloured SEMs of the mite and posted it on the Mite Image Gallery at the University of Queensland. Much to my surprise this was the first record of the family in Australia and my friend Bruce Halliday, putting aside his doubts about the validity of ephemeral web publications, cited the image in his Mites of Australia, a checklist and bibliography (1998, CSIRO Publications). Interestingly, the image at the top of a species of Homocaligus is probably the first record of the family from Alberta.

A pustule from the gymnodamaeid Joshuella agrosticula at 40,000x

Although festive enough for the holiday in itself, I thought the Homocaligus needed more adornment. The pine cone-like bulbs on the mite are cerotegumental pustules from another mysterious Albertan mite, Roynortonella gildersleeveae (Hammer, 1952). This mite used to reside in the genus Nortonella Paschoal, named after the great oribatologist Roy A. Norton. Unfortunately, in 1908 a certain Rohwer had already used Nortonella for a genus of tenthridinid sawflies; thus, the name was preoccupied. I suggested the new name as a replacement that was in keeping with the author’s original intentions. Like other members of its family (Gymnodamaeidae), the surface of the adult mite has scattered fields of strange and intriguing Bucky Ball-like pustules. The pustules arise as the cerotegument dries after the adult moult in what must be some interaction between microfibers and wax. Their elaborate form and species-to-species variants keep me, if not tied to a particular belief in the nature of the Universe, at least still amazed by how rewarding the study of even the smallest parts of Nature can be.

For more on Homocaligidae and Gymnodamaeidae see:

Fan Q-H. 1997. The Homocaligidae from China, with description of two new species (Acari: Raphignathoidea). Entomol. Sin. 4: 337-342.

Gonzalez RH. 1978. a new species of mite on water lettuce in Thailand (Acari: Homocaligidae). International Journal of Acarology 4:221-225.

Walter DE. 2009. Genera of Gymnodamaeidae (Acari: Oribatida: Plateremaeoidea) of Canada, with notes on some nomenclatorial problems. Zootaxa 2206: 23–44.

Wood TG. 1969. The Homocaligidae a new family of mites (Acari: Raphignathoidea), including a description of a new species from Malaya and the British Solomon Islands. Acarologia (Paris): 11: 711-729.

5 Responses to “The Macromite Before Christmas”

  1. Ted C. MacRae Says:

    Was it a different Norton that the sawfly genus was named for?

    Any ideas at all what function those pustules have?

    • macromite Says:

      Hi Ted,

      I have an interest in sawflies, so I thought the short answer (yes) insufficient and that I really should find out who this symphytan Norton was. That turned out to be not so easy because (1) there are a lot of Nortons who are or have been entomologists; (2) the wheat stem sawfly Cephus cinctus Norton, 1872, is a major pest; (3) once I discovered his first name, Edward, I had to wade through lots of pages on the actor Edward Norton (for some unapparent reason, this guy and ‘entomologist’ come up linked) and (4) EO Wilson who has published books via WW Norton! However, persistence, refined research terms, and switching search engines (hate to say it, but Google seems the best) finally produced a professional history, if not personal details.

      According to Ross (The Early History of Sawfly Study in North America. Transactions of the American Entomological SocietyVol. 85, No. 4, The Centennial Number (Dec., 1959), pp. 315-321.), Norton’s first paper on sawflies was published in 1860 and “Norton is certainly the father of North American sawfly studies”. This is further supported by an online Master’s Thesis by Rachel Ann Braud (2001. Diversity, Abundance, and the Effect of Bacillus thuringiensis var. kurstaki Berliner and Gypchek™ on Larval and Adult Symphyta in Virginia and West Virginia. MS Thesis West Virginia University, Morgantown.):

      “Edward Norton’s (1867-1869) masterwork on sawflies was published in four installments. It contained keys to genera and in many cases to species. Some of these keys are still used today and, in some cases, are the only ones in existence for certain species (Ross 1960). The catalogue contained 300 species, the most comprehensive at that date.”

      Also, in passing in a paper by Dave Smith (now retired, but still the best of the current sawfly workers), I learned that Norton was a buddy of de Saussure and helped translate his great work “Synopsis of American Wasps” (1875) into English. Looks like Norton’s most important works were:

      Norton, E. 1867. Catalogue of the described Tenthredinidae and Uroceridae of North America. Transactions of the American Entomological Society 1: 31-84, 193-280.

      Norton, E. 1869. Catalogue of the described Tenthredinidae and Uroceridae of North America. Transactions of the American Entomological Society 2: 321-368.

      Norton, E. 1872. Notes on North American Tenthredinidae with descriptions of new species. Transactions of the American Entomological Society 4: 77-86.

      Having run on so, I think I will limit myself to a short answer to your second question – yes! Or rather, I have a hypothesis. Maybe I should blog on this next.

  2. Adrian Thysse Says:

    Merry Christmas Dave! An amazing mite, even when unadorned. Looks like an alien spaceship coming in for a landing.

  3. scrubmuncher Says:

    Hello Dave

    I sent an email about the images to the alberta address. Did you get it?



  4. A Good, but Deviant Stigmaeus « Macromite's Blog Says:

    […] reaches it apogee in groups such as a the Homocaligidae or the Cryptognathidae. In the latter, the body is completely encased in a dorsal and a ventral […]

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