Morion japonicum, copyright Katsuro Yahiro.

Belongs within: Harpalinae.

Morion is a cosmopolitan genus of ground beetles found in rotten logs.

Characters (from Ball & Bousquet 2001): Body subpedunculate, legs flattened; head with two supra-orbital setigerous punctures over each eye; antennomeres 5–10 submoniliform, short, slightly compressed; mandible without setigerous punctures; maxillary palpomere 4 about subequal in length to palpomere 3; margin of pronotum with about seven setigerous punctures; eighth stria appearing as zig-zag groove, with numerous, evenly spaced ocellate punctures; middle coxal cavities conjunct (entirely enclosed by sterna), mesepimera not extended to middle coxal cavities.

On Morion
Published 22 June 2018
Morion monilicornis, copyright Charles Schurch Lewallen.

Just a quick one today. Above is a typical member of Morion, a genus currently recognised as including over forty species of carabid beetles though there may be many more yet to be described. Characteristic features of this genus include a somewhat flattened body form, moniliform antennae (that is, the antennal segments are all short and similar in form, like beads on a string), a more or less cordiform (heart-shaped) pronotum, and a bilobed median tooth on the mentum (a sclerite on the underside of the head that might be thought of as the ‘lower lip’ of the mouth) (Will 2003). Though currently recognised as pantropical, Will (2003) suggested that its defining features were potentially plesiomorphic relative to some closely related genera. Further studies may identify Morion in its current sense as a paraphyletic grade to those genera, possibly leading to a reclassification.

The flattened body form of Morion and its relatives (the Morionini) reflects their preferred habitat. Like other carabids, Morion species are voracious predators (both as adults and larvae). Morionins are specialised for hunting in dead wood and under back, forcing themselves through enclosed gaps in search of other insects that might have thought themselves secure in their lignified fortresses.

Morion revisited
Published 30 November 2019

I mentioned above how Will (2003) had questioned the monophyly of Morion, owing to its lack of derived features in comparison with closely related genera. In this section, I’ll take the opportunity to dive a little further into ways the genus may be divided.

Just to remind you what we’re looking at: Morion monilicornis, copyright Robert Webster.

As noted by Will (2003), many authors have recognised two subgenera within Morion, Morion sensu stricto and Neomorion. These subgenera were first established by Jeannel (1948) who identified a distinction between species he examined from the Old World (Africa and Asia) and the Americas. The Old World species, to which Jeannel gave the name Neomorion, had a number of setae along the rear margin of the last ventrite of the abdomen. In males, the basal segment of the fore tarsus had the inner apex drawn out into a tooth. The aedeagus bears a large dorsoapical orifice; in Old World Morion examined by Jeannel, this orifice was covered over by a large bilobed lamella. In the New World species of Morion sensu stricto, in contrast, the rear margin of the last ventrite bore only two setae, and males lacked a medioapical tooth on the basal fore tarsomere. The opening of the aedeagus lacked a covering lamella. In his key to Morion and related genera, Will (2003) referred only to the state of the male fore tarsus as distinguishing the subgenera. It may be that this indicates that the significance of the other characters described by Jeannel had been subject to question, but I suspect that they may have omitted by Will because their state in a number of Morion species remains unknown.

Aedeagi of Morion in lateral and dorsal view from Jeannel (1948). On the left is an Old World species (Morion orientale), on the right a South American species (M. georgiae).

A particular notable lacuna in Jeannel’s brief survey of Morion was that he didn’t look at any Australian species. In his description of M. crassipes*, a species found in the vicinity of Cairns in Queensland, Sloane (1904) noted that the male fore tarsi differed from those of other Australian species in having the “basal joints rounded and not produced at inner apical angle”, implying that most Australian Morion have tarsi resembling those of the New World species. Moore (1965), in a review of Australian genera of Pterostichinae, describes Morion as having an aedeagus with an orifice on the dorsum, with no mention of a covering lamella, again also suggesting a resemblance to New World rather than Old World species (unfortunately, Moore did not specify exactly which species his description of the genitalia was based on). Moore (1965) also noted that Australian species were distinctive among Morion in having a pronotum with more than the two setae along each lateral margin found in species from elsewhere. One species which is found in New Guinea and northern Australia, M. longipennis, does have only two pairs of marginal setae on the pronotum, and Darlington (1962) suggested that it was probably more closely related to Asian species than to other Australian Morion. The aforementioned M. crassipes differs from other Australian species in a number of significant features, including large size (it grows to a full inch in length) and modified legs, and Sloane (1904) did briefly wonder whether it should even be regarded as a Morion, but it does share the plurisetose pronotal margins. I should note that I’ve found no reference to the pilosity of the last ventrite in any Australian species.

*Under the name ‘Morio crassipes‘; confusion about whether this genus should be called Morion or Morio lingered for a long time in the early 20th century.

So overall, there is the suggestion of three distinct groups within Morion, for the Old World, American, and Australian species, with the last two more similar to each other than to the first. The New World species of Morion are more diverse in South America than in North America, and one might be tempted to line up the relationship between the three groups with the division of Gondwana. The Old World species group may have diverged first with the separation of Africa and/or India, followed by the South American and Australian lineages diverging as their own continents became isolated. The South American species group may have spread into North America with the formation of the Central American land bridge, and the increased proximity of Australasia to Asia may have allowed members of the Old World group such as M. longipennis to invade from the northwest. However, I’ve based this scenario on some pretty weak assumptions based on very incomplete data, and it would require a more detailed investigation before we could say if there’s any merit to it.

Systematics of Morion
<==Morion Latreille 1810 [=Morio (l. c.) non Montfort 1810]LM87
    |--*M. monilicornis (Latreille 1806)LM87, BB01 [=Harpalus monilicornisLM87, Carabus monilicornisL02]
    |--M. aridus Allen 1968BB01
    |--M. australis Castelnau 1867 [=Morio australis]LM87
    |--M. crassipes Sloane 1904 [=Morio crassipes]LM87
    |--M. dalbertisi Chaudoir 1880 [=Morio dalbertisi]LM87
    |--M. germanus Chaudoir 1880 [=Morio germanus]LM87
    |--M. japonicum (Bates 1883)I92
    |--M. longicollis Macleay 1871 [=Morio longicollis]LM87
    |--M. longipennis Putzeys 1875LM87
    |--M. novaehollandiae Castelnau 1867 (see below for synonymy)LM87
    |--M. orientalisB89
    |--M. pachysomus Chaudoir 1880LM87
    |--M. piceus Castelnau 1867LM87
    |--M. stolidusM86
    `--M. victoriae Castelnau 1867LM87

Morion novaehollandiae Castelnau 1867 [=Morio novaehollandiae; incl. Morio australasiae Chaudoir 1869, Morio seticollis Macleay 1871]LM87

*Type species of generic name indicated


[BB01] Ball, G. E., & Y. Bousquet. 2001. Carabidae Latreille, 1810. In: Arnett, R. H., Jr & M. C. Thomas (eds) American Beetles vol. 1. Archostemata, Myxophaga, Adephaga, Polyphaga: Staphyliniformia pp. 32–132. CRC Press: Boca Raton.

[B89] Bates, H. W. 1889. Viaggio di Leonardo Fea in Birmani e regioni vicine. XVI.—On some Carabidae from Burma collected by Mr. L. Fea. Annali del Museo Civico di Storia Naturale di Genova, Serie 2a, 7: 100–111.

Bell, R. T. 1990. Insecta: Coleoptera Carabidae adults and larvae. In: Dindal, D. L. (ed.) Soil Biology Guide pp. 1053–1092. John Wiley & Sones: New York.

Darlington, P. J., Jr. 1962. The carabid beetles of New Guinea. Part I. Cicindelinae, Carabinae, Harpalinae through Pterostichini. Bulletin of the Museum of Comparative Zoology 126 (3): 319–564, 4 pls.

[I92] Iwahashi, J. (ed.) 1992. Reddo Deeta Animaruzu: a pictorial of Japanese fauna facing extinction. JICC: Tokyo.

Jeannel, R. 1948. Faune de l’Empire Français. X. Coléoptères Carabiques de la Région Malgache (deuxième partie). Office de la Recherche Scientifique Coloniale: Paris.

[L02] Latreille, P. A. 1802. Histoire Naturelle, générale et particulière des crustacés et des insectes vol. 3. Familles naturelles des genres. F. Dufart: Paris.

[LM87] Lawrence, J. F., B. P. Moore, J. E. Pyke & T. A. Weir. 1987. Zoological Catalogue of Australia vol. 4. Coleoptera: Archostemata, Myxophaga and Adephaga. Australian Government Publishing Service: Canberra.

[M86] Macleay, W. 1886. The insects of the Fly River, New Guinea, “Coleoptera”. Proceedings of the Linnean Society of New South Wales, series 2, 1 (1): 136–157.

Moore, B. P. 1965. Studies on Australian Carabidae (Coleoptera). 4.—The Pterostichinae. Transactions of the Royal Entomological Society of London 117 (1): 1–32.

Sloane, T. G. 1904. Studies in Australian entomology. No. XIV. New species of geodephagous Coleoptera from tropical Australia. Cicindelidae (3), and Carabidae (5) [Platysmatini, Morioni, Perigonini, Masoreini, and Physocrotaphini]. Proceedings of the Linnean Society of New South Wales 29 (3): 527–538.

Will, K. W. 2003. Review and cladistic analysis of the generic-level taxa of Morionini Brullé (Coleoptera: Carabidae). Pan-Pacific Entomologist 79 (3–4): 212–229.

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