Glyphyalinia Snails

North America (as with pretty much everywhere in the world outside the coldest regions) is home to a wide diversity of small, terrestrial snails that tend to pass unnoticed. Among the more diverse of these is the zonitid genus Glyphyalinia.

Glyphyalinia carolinensis, copyright John Slapcinsky.

Glyphyalinia species are often found in forest leaf-litter in the eastern part of North America. They have a low, translucent shell that is often about half a centimetre in diameter. Whorls of the shell increase regularly in size and are marked by a series of strongly impressed radiating lines in addition to finer growth lines. The umbilicus of the shell varies between species from completely absent to quite wide (Burch & Pearce 1990). The soft body of the animal varies in coloration, again depending on species. That of G. roemeri is all white except for the eyes; that of G. wheatleyi is almost uniformly black. The reproductive system of Glyphyalinia (which are hermaphroditic) includes a well-developed epiphallus and a distinct, ovoid spermathecal sac (Baker 1930).

Multiple species of Glyphyalinia may be found living in a single patch of forest though, at present, we know little about how (and whether) micro-habitats are partitioned between species. Some species seem to tolerate a wide variety of soil types and are correspondingly widely distributed. Others are more selective and localised; some may be considered endangered by habitat degradation. Even supposedly widespread species may be more vulnerable than appreciated: at least some may represent clusters of closely related species rather than truly uniform populations. These tiny snails can be notoriously difficult to study, making for a risk that they might just slip away barely noticed.

REFERENCES

Baker, H. B. 1930. The North American Retinellae. Proceedings of the Academy of Natural Sciences of Philadelphia 82: 193–219.

Burch, J. B., & T. A. Pearce. 1990. Terrestrial Gastropoda. In: Dindal, D. L. (ed.) Soil Biology Guide pp. 201–309. John Wiley & Sones: New York.

Williamsita

A while back, I wrote a post about the crabronid wasp genus Podagritus. This time, I'm going to cover another crabronid genus found here in Australia: Williamsita.

Williamsita sp., copyright David Francis.

Like Podagritus, Williamsita species are boldly coloured wasps, typically mostly black with contrasting yellow or orange markings. They differ from Podagritus species in being more robust with the base of the gaster not notably pedunculate. Other distinguishing features include the presence of distinct foveae (pits) against the margins of the eyes (occasionally less distinct in males), thirteen-segmented antennae in males, and a pygidial plate in both sexes that is narrowed and concave in females, quadrate in males. Williamsita species also do not have the palps reduced as in Podagritus, instead having the more typical arrangement of six segments in the maxillary palps and four segments in the labial palps (Bohart & Menke 1976).

To date, eleven species have been recognised in the genus Williamsita (Leclercq 2006). Most are found in Australia with a single species each known from New Caledonia and Vanuatu. Leclercq (1950) suggested dividing the genus between two subgenera with all species except the New Caledonian type species W. novocaledonica forming a subgenus Androcrabro. Features supporting the latter taxon included the presence of ventral notches on one or more segments of the antennae in males. However, Leclercq later suggested abandoning such a formal division, questioning its significance (Leclercq 2006). The Australian species of Williamsita are, nevertheless, distinct from the two insular species in being marked with much stronger punctation over the body.

Most Williamsita species remain little seen and poorly known. However, breeding habits have been recorded for two Australian species, W. bivittata and W. tasmanica (Maynard & Fearn 2021; McCorquodale et al. 1989). Both these species nest in branching holes in rotting wood, either commandeering burrows left by wood-boring insects or excavating their own. Prey consists of larger flies such as blow flies or soldier flies which were carried back to the nest by the wasp running with the fly carried below the body. Up to six paralysed flies might be placed lying on their backs in a nest cell with an egg laid across the 'throat' (i.e. at the joint between head and thorax) of one of the flies. The cell would then be closed with a plug of woody frass. McCorquodale et al. (1989) recorded W. bivittata constructing several such cells in a series along a single tunnel, whereas Maynard & Fearn (2021) found W. tasmanica more likely to place a single cell in a side-branch. As both observations were limited to a single location in a single season, though, one might reasonably question whether these represent true differences in species behaviour or were determined by available conditions. There's a limit to how deep a Williamsita can burrow.

REFERENCES

Bohart, R. M., & A. S. Menke. 1976. Sphecid Wasps of the World. University of California Press: Berkeley.

Leclercq, J. 1950. Sur les crabroniens orientaux et australiens rangés par R. E. Turner (1912–1915) dans le genre Crabro (subgenus Solenius). Bulletin et Annales de la Société Entomologique de Belgique 86 (7–8): 191–198.

Leclercq, J. 2006. Hyménoptères crabroniens d'Australie du genre Williamsita Pate, 1947 (Hymenoptera: Crabronidae). Notes Fauniques de Gembloux 59 (2): 115–119.

Maynard, D., & S. Fearn. 2021. Ecological and behavioural observations of a nesting aggregation of the endemic Tasmanian digger wasp Williamsita tasmanica (Smith, 1856) (Hymenoptera: Crabronidae: Crabroninae). Papers and Proceedings of the Royal Society of Tasmania 155 (1): 43–50.

McCorquodale, D. B., C. E. Thomson & V. Elder. 1989. Nest and prey of Williamsita bivittata (Turner) (Hymenoptera: Sphecidae: Crabroninae). Australian Entomological Magazine 16 (1): 5–8.

Opening Dors

My current dayjob mostly revolves around identifying and counting dung beetles. When Europeans settled Australia, they brought their farm animals with them. Unfortunately, the large piles of dung produced by cattle and horses proved rather daunting to native scavengers used to the more compact droppings of kangaroos and possums. And if you've ever experienced an Australian summer, you'll know that flies are definitely a thing. To help with this situation, Australia has had a long-running programme introducing exotic dung beetles that are better able to clean up after livestock. Most of these are members of the typical dung beetle family Scarabaeidae but one species, Geotrupes spiniger, represents a different subgroup of the superfamily Scarabaeoidea. These are the earth-boring dung beetles or dor beetles of the Geotrupidae.

Dor beetle Geotrupes spiniger, copyright Udo Schmidt.
The geotrupids are medium-sized to very large beetles, ranging in size from half a centimetre to 4.5 cm in length (Jameson 2002). Like many other members of the Scarabaeoidea, they have broad fore legs used for digging. Their short, eleven-segmented antennae end in the asymmetrical club typical of scarabaeoids but they may be distinguished from other families in that the basal segment of the three-segmented club is expanded to form a 'cup' against which the other segments may be tightly closed. The body of geotrupids is strongly convex, and is smooth and shiny dorsally but hairy underneath. In many species, the males may bear elaborate horns and/or processes on the head and pronotum.

Male Taurocerastes patagonicus, copyright Nicolás Lavandero.

Despite their size, geotrupids are secretive animals, spending most of their time in burrows underground (which may be up to three metres in depth) and usually only emerging at night. Various species feed on animal dung or decaying matter; some feed on subterranean fungi. In at least some species, eggs are laid in brood chambers within the parent's home burrow and multiple life stages may share a single burrow. Burrows may also be shared between multiple adults when conditions demand. Though adults do not directly tend to larvae, they may stock brood chambers with food supplies. In some Australian species of the subfamily Bolboceratinae, females lay a single gigantic egg at a time that may be up to 56% the size of its layer (Houston 2011). Larvae hatching from such an egg are able to develop right through to maturity without feeding.

Adult geotrupids produce a stridulating noise when disturbed which is the origin of the alternate vernacular name of "dor beetle" ("dor" being an old word for a buzzing insect). Larvae may or may not be capable of stridulation, depending on the species.

Male Blackburnium rhinoceros, copyright Edward Bell.

The classification of geotrupids is the subject of ongoing investigation. A recent classification divides the family between three subfamilies, the widespread Geotrupinae and Bolboceratinae and the South American Taurocerastinae. Morphological differences between these subfamilies, particularly at the larval stage, have lead some researchers to question whether the Geotrupidae in the broad sense represents a monophyletic group. Molecular analyses thus far seem ambiguous; an analysis by McKenna et al. (2015) placed geotrupids as part of a polytomy near the base of the scarabaeoids. As an aside, my supervisor recently asked myself and a retired colleague whether Geotrupes spiniger was the only species of geotrupid found in Australia. I replied "yes", our colleague responded "no". Our conflict, of course, was based on whether Australia's wide diversity of Bolboceratinae contributed to the count.

REFERENCES

Houston, T. F. 2011. Egg gigantism in some Australian earth-borer beetles (Coleoptera: Geotrupidae: Bolboceratinae) and its apparent association with reduction or elimination of larval feeding. Australian Journal of Entomology 50: 164–173.

Jameson, M. L. 2002. Geotrupidae Latreille 1802. In: Arnett, R. H., Jr, M. C. Thomas, P. E. Skelley & J. H. Frank (eds) American Beetles vol. 2. Polyphaga: Scarabaeoidea through Curculionoidea pp. 23–27. CRC Press.

McKenna, D. D., B. D. Farrell, M. S. Caterino, C. W. Farnum, D. C. Hawks, D. R. Maddison, A. E. Seago, A. E. Z. Short, A. F. Newton & M. K. Thayer. 2015. Phylogeny and evolution of Staphyliniformia and Scarabaeiformia: forest litter as a stepping stone for diversification of nonphytophagous beetles. Systematic Entomology 40: 35–60.

Platybunus: the Wide-Eyed Harvestmen of Europe

The western Palaearctic region (that is, Europe and the immediately adjacent parts of Asia and northern Africa) is home to a diverse and distinctive fauna of harvestmen. Among the various genera unique to this part of the world are the forest- and mountain-dwellers of the genus Platybunus.

Platybunus pinetorum, copyright Donald Hobern.

Platybunus species are moderate-sized long-legged harvestmen of the family Phalangiidae, the central body in larger individuals being about eight millimetres long (Martens 1978). Their most characteristic feature is a relatively large eye-mound, distinctly wider than long and occupying a large section of the anterior carapace. As with other European phalangiids, they eye-mound is ornamented with a row of denticles each side though the body lacks denticles over the remainder of the dorsum. The body is often comparatively slender, tapering towards the rear (particularly in males), and is marked on the dorsum by a darker median band. The pedipalps have a pair of well-developed setose apophyses on the inner distal ends of the patella and tibia, and a series of long spine-like tubercles on the underside of the femur. These tubercles presumably function in the capture of prey, forming a basket that can be closed around the harvestman's victims. External sexual dimorphism in Platybunus is fairly minimal though females are overall larger and fatter. The penis is notably long and slender with a relatively small glans, offset from the shaft by a more or less marked constriction.

Platybunus bucephalus, copyright Adrian Tync.

Martens (1978) recognises four species of Platybunus found in higher altitude regions of central Europe with the species P. bucephalus and P. pinetorum occupying much of the genus' range. Platybunus bucephalus may be distinguished from P. pinetorum by, among other features, its relatively shorter legs. Platybunus pallidus is endemic to the Carpathians, and the tiny P. alpinorelictus inhabits the Garda Mountains of northern Italy. Another species, P. anatolicus, was described from Turkey by Roewer (1956)*. In general, Platybunus species inhabit alpine and subalpine forests, being found among the herbaceous undergrowth, under bark or on rock faces. Where their ranges overlap, P. bucephalus is more accustomed to extending beyond the forest margins than P. pinetorum and may be found above the tree-line. In recent years, the range of P. pinetorum has extended northwards, being first recorded from the UK in 2010 and Sweden in 2015 (Fritzén et al. 2015). At least some populations of P. pinetorum are capable of reproducing parthenogenetically and this may have played a part in its spread.

*Platybunus mirus was described by Loman (1892) on the basis of two male specimens that supposedly came from Sumatra. Though the identity of this species has never been resolved (Loman's illustration of the penis is at least suggestive of a true Platybunus), the claimed locality seems almost certain to be an error of some kind.

The internal classification of the Phalangiidae remains in need of further investigation. Platybunus has been recognised by some authors as forming a subfamily Platybuninae with a cluster of other western Palaearctic genera bearing similar ventrally spined pedipalps (Zhang & Zhang 2012). However, other authors have not separated this group from the subfamily Phalangiinae. The platybunines may represent a phylogenetically coherent grouping, or their shared features may reflect adaptations to a similar life style. The genital morphology of Platybunus is recognisably distinct from that of other platybunines which may argue against any relationship (Martens 1978). On the other hand, platybunines might possibly be distinguished from phalangiines by the chemical composition of their repugnatorial gland secretions (Raspotnig et al. 2015). A formal analysis of the family's evolution would be a welcome advance.

REFERENCES

Fritzén, N. R., V. Rinne, M. Sunhede, A. Uddström, S. Van de Poel & P. De Smedt. 2015. Platybunus pinetorum (Arachnida, Opiliones) new to Sweden. Memoranda Soc. Fauna Flora Fennica 91: 37–40.

Loman, J. C. C. 1892. Opilioniden von Sumatra, Java und Flores. In: M. Weber (ed.) Zoologische Ergebnisse einer Reise in Niederländisch Ost-Indien vol. 3 pp. 1–26, pl. 1. E. J. Brill: Leiden.

Martens, J. 1978. Spinnentiere, Arachnida: Weberknechte, Opiliones. Gustav Fischer Verlag: Jena.

Raspotnig, G., M. Schaider, P. Föttinger, V. Leutgeb & C. Komposch. 2015. Benzoquinones from scent glands of phalangiid harvestmen (Arachnida, Opiliones, Eupnoi): a lesson from Rilaena triangularis. Chemoecology 25: 63–72.

Roewer, C. F. 1956. Über Phalangiinae (Phalangiidae, Opiliones Palpatores). (Weitere Weberknechte XIX). Senckenbergiana Biologica 37 (3–4): 247–318.

Zhang, C., & F. Zhang. 2012. On the subfamilial assignment of Platybunoides (Opiliones: Eupnoi: Phalangiidae), with the description of a new species from China. Zootaxa 3190: 47–55.