Colpochila

Colpochila obesa, from Insects of Tasmania.

Belongs within: Melolonthinae.

Colpochila is a diverse genus of large chafers found in Australia. Mature beetles are short-lived and mostly crepuscular, flying towards light sources at night (Britton 1986).

The Western Australian species C. crinita and C. nasuta combine eight-segmented antennae with granular, densely setose pronotal margins (Britton 1986).

Colpochila: the chafing of a mega-genus
Published 11 May 2020

Just a few weeks ago, I discussed the melolonthines, a hyperdiverse group of beetles including the chafers that have historically presented something of a taxonomic challenge. Commenting on that post, Adam Yates brought up one aspect of the difficulties presented by this group that I hadn’t gotten around to discussing. This is the presence among melolonthines of a number of what may be called ‘mega-genera’, large genera containing literally hundreds of species that defy attempts to break them down into more manageable units. So on that note, it’s only appropriate that I move on to an example of one of these mega-genera, Colpochila.

A second Colpochila species, from Friends of Queens Park Bushland.

Colpochila is an Australian genus of melolonthines belonging to a group currently recognised as the tribe Liparetrini (Britton 1986). Liparetrins are, on the whole, a fairly generalised group: characters of the group include a lack of metallic coloration, a labrum which sits underneath and is not fused to the clypeus, simple claws, and relatively broad hind tibiae that end in a pair of widely separated spurs that are placed one above and one below so that the tarsus when moved from side to side can move between the spurs. The two largest genera in the tribe, by a significant margin, are Colpochila and Liparetrus. Somewhere in the region of 130 species are currently recognised in Colpochila whereas Liparetrus is even more diverse. However, both genera were referred to by Britton (1986) as ‘polythetic’: that is, both represent assemblages of species that, while clearly connected to each other overall, are difficult to characterise from a diagnostic perspective. Species of the genus possess enough features in common that we can readily recognise them as related but it is difficult to drill down on any individual feature or set of features that is shared between all species without exception. Similarly, while I can say from experience that it is generally easy to tell at a glance whether a given species is a Colpochila or a Liparetrus, it is a lot harder to actually define what separates the two genera. The most obvious distinction is size: Colpochila species are relatively large chafers, over a centimetre in length, whereas Liparetrus are smaller. Other features that each separate most Colpochila species from most (though not all) Liparetrus are circular eyes (most Liparetrus have eyes with flattened edges in back so the eye is closer to semi-circular), antennae with more segments in the terminal club, longer elytra that leave less of the end of the abdomen exposed, and hind coxae without the translucent margins found in many Liparetrus.

The lifestyles of Colpochila species are still not very well known. As with other melolonthines, most of the life is spent underground with mature adults only emerging very briefly to breed. The active adults fly at night and may be attracted to lights; it seems unclear whether they feed at maturity. This genus is mostly found in drier habitats such as open woodland, grasslands or semi-desert (mind you, this is Australia we’re talking about; drier habitats are 90% of what’s going). Of the known species, over half are found in Western Australia.

So why are Colpochila and other melolonthine mega-genera so diverse? It should be noted that straight geographical and/or ecological divergence does not appear to be the reason: not only is it possible to find multiple species of a single genus in one location but one may even collect very similar species together. It might be that the diversity of the mega-genera is artefactual, a reflection of the failure of taxonomists to properly identify relationships: any study that wanted to explain their diversity would have to study their phylogenetic relationships with related smaller genera to confirm their evolutionary coherence and/or age of divergence. However, if the current generic classification of melolonthines reflects a real evolutionary pattern, a potential explanation was proposed by Britton (1986). Adult melolonthines do not emerge immediately upon maturing but remain dormant underground awaiting a suitable environmental signal such as rainfall. However, rainfall in the arid zone at any one time is often uneven. Dormant beetles at one spot may feel the urge to emerge while others nearby may be left to wait for the next shower. The first wave will have died off before the second wave emerges, and their offspring will not yet be mature. As a result, sub-populations in a single region may become temporally staggered allowing the possibility of divergence via genetic drift. Eventually, their emergence times may drift back into sync but by then they may no longer be able to breed successfully. Could this be the reason why so many species may be found in a single location or may other factors be more significant?

Systematics of Colpochila

Characters (from Britton 1986): Large (length 11-33 mm), of stout build; labrum not fused to clypeus; antennae 8- or 9-segmented, including a 3- to 7-lamellate club; eyes nearly circular though partly covered by prothorax; elytra not abbreviated (ratio of maximum length:width >2.3:1), covering propygidium and (in part) pygidium; elytral striae grouped in pairs so alternate intervals are obviously different in width; posterior and lateral margins of posterior coxae never thin and membranous; claws without a pulvillus beneath; abdomen with only terminal ventrite movable, separated from fifth ventrite by a pale membrane; propygidium and penultimate ventrite separated by suture on each side.

<==Colpochila Erichson 1843 [incl. Aplonycha Dejean 1833 (n. n.), Haplonycha Blanchard 1851]B86
    |--*C. gouldi (Hope 1842) [=Sericesthis gouldi, Haplonycha gouldi; incl. H. pulchripennis Lea 1924]B86
    |--C. abdita Britton 1986B86
    |--C. accepta (Blackburn 1906) [=Haplonycha accepta]B86
    |--C. aequaliceps (Blackburn 1906) [=Haplonycha aequaliceps]B86
    |--C. affinis Britton 1986B86
    |--C. amabilis (Blackburn 1906) [=Haplonycha amabilis]B86
    |--C. andersoni Britton 1986B86
    |--C. antennalis (Blackburn 1906) [=Haplonycha antennalis]B86
    |--C. aquila Britton 1986B86
    |--C. arida Britton 1986B86
    |--C. badia (Burmeister 1855) [=Haplonycha badia]B86
    |--C. bella Blackburn 1890B86 (see below for synonymy)
    |--C. bicolor Blackburn 1890 [=Haplonycha bicolor]B86
    |--C. bidentipes (Lea 1926) [=Haplonycha bidentipes]B86
    |--C. bimucronata (Lea 1917) [=Haplonycha bimucronata]B86
    |--C. blackburni Britton 1986B86
    |--C. bogania Britton 1986B86
    |--C. boreas Britton 1986B86
    |--C. brevisetosa (Lea 1930)B86 [=Haplonycha brevisetosaB86; incl. C. laciniata Britton 1959HW92]
    |--C. calabyi Britton 1986B86
    |--C. callida Britton 1986B86
    |--C. capta Britton 1986B86
    |--C. carinata Blackburn 1890 [=Haplonycha carinata]B86
    |--C. carnabyi Britton 1986B86
    |--C. castanea Britton 1986B86
    |--C. chinnicki Britton 1986B86
    |--C. clara (Blackburn 1906) [=Haplonycha clara]B86
    |--C. clavipalpis Britton 1986B86
    |--C. clypealis Blackburn 1906 [=Haplonycha clypealis; incl. H. marginipennis Lea 1919]B86
    |--C. comma Britton 1986B86
    |--C. crassiventris Blanchard 1850B86 (see below for synonymy)
    |--C. crepera Britton 1986B86
    |--C. crinita (Burmeister 1855) [=Haplonycha crinita]B86
    |--C. deceptor Blackburn 1890 [=Haplonycha deceptor; incl. H. punctatissima Blackburn 1906]B86
    |--C. decolor Britton 1986B86
    |--C. dilatata (Lea 1917) [=Haplonycha dilatata]B86
    |--C. efficax Britton 1986B86
    |--C. erythrocephala (Lea 1917) [=Haplonycha erythrocephala]B86
    |--C. faceta (Blackburn 1906) [=Haplonycha faceta]B86
    |--C. firma (Blackburn 1906) [=Haplonycha firma]B86
    |--C. fortis Blackburn 1890 [=Haplonycha fortis; incl. C. campestris Blackburn 1892, H. campestris]B86
    |--C. freyi Britton 1959B86
    |--C. fulva Britton 1986B86
    |--C. funerea Blackburn 1890 [=Haplonycha funerea]B86
    |--C. gagatina (Burmeister 1855) [=Haplonycha gagatina; incl. H. pygidialis Lea 1930]B86
    |--C. gibbosicollis Blackburn 1890 [=Haplonycha gibbosicollis, H. gibbicollis (l. c.)]B86
    |--C. gigantea (Burmeister 1855) [=Haplonycha gigantea; incl. H. fimbripennis Lea 1924]B86
    |--C. goerlingi Britton 1986B86
    |--C. griffithi (Blackburn 1907) [=Haplonycha griffithi]B86
    |--C. ignota Britton 1986B86
    |--C. immatura (Lea 1930) [=Haplonycha immatura]B86
    |--C. infernalis Britton 1986B86
    |--C. ingens Britton 1986B86
    |--C. interocularis (Lea 1917) [=Haplonycha interocularis]B86
    |--C. iota Britton 1986B86
    |--C. iricolor Britton 1986B86
    |--C. iridea (Lea 1930) [=Haplonycha iridea]B86
    |--C. iris Britton 1986B86
    |--C. jungi (Blackburn 1906) [=Haplonycha jungi]B86
    |--C. kalambi Britton 1986B86
    |--C. laminata Blackburn 1890 [incl. C. dubia Blackburn 1890]B86
    |--C. latebricola (Blackburn 1906) [=Haplonycha latebricola]B86
    |--C. leo Britton 1986B86
    |--C. limbata Britton 1986B86
    |--C. longiclava Britton 1986B86
    |--C. longior (Blackburn 1906) [=Haplonycha longior; incl. H. pallida Lea 1924]B86
    |--C. longipalpis (Lea 1926) [=Haplonycha longipalpis]B86
    |--C. lutea Britton 1986B86
    |--C. major Britton 1986B86
    |--C. marginata (Blackburn 1906) [=Haplonycha marginata]B86
    |--C. maura Britton 1986B86
    |--C. melina Britton 1986B86
    |--C. minor Britton 1986B86
    |--C. mixta (Lea 1917) [=Haplonycha mixta]B86
    |--C. nana Britton 1986B86
    |--C. nasuta Britton 1986B86
    |--C. nigra (Lea 1919) [=Haplonycha nigra]B86
    |--C. nigromarginata Britton 1986B86
    |--C. nitens Britton 1986B86
    |--C. nitida Britton 1986B86
    |--‘Haplonycha’ nitidicollis Nonfried 1892 (n. d.)B86
    |--C. nobilis (Blackburn 1906) [=Haplonycha nobilis; incl. H. colossa Lea 1919, H. lucifera Blackburn 1906]B86
    |--C. obesa (Boisduval 1835)B86 (see below for synonymy)
    |--C. opaca (Lea 1917) [=Haplonycha opaca]B86
    |--C. pagana Britton 1986B86
    |--C. pallidula Britton 1986B86
    |--C. palpalis Blackburn 1895B86
    |--C. parva Britton 1986B86
    |--C. paula Britton 1986B86
    |--C. piceofulva Britton 1986B86
    |--C. picta Britton 1986B86
    |--C. pilosa (Blackburn 1906) [=Haplonycha pilosa]B86
    |--C. pinguis (Macleay 1871) [=Haplonycha pinguis]B86
    |--C. polita Britton 1986B86
    |--C. potens Britton 1986B86
    |--C. pruinosa (Lea 1930) [=Haplonycha pruinosa]B86
    |--C. pubescens Britton 1986B86
    |--C. pulchella Blackburn 1890 [incl. Haplonycha novemarticulata Lea 1917, H. octoarticulata Lea 1917]B86
    |--C. punctiventris Blackburn 1890 [incl. Haplonycha gymnopyga Lea 1917]B86
    |--C. punctulata Blanchard 1851B86
    |--C. pygmaea Blackburn 1890B86
    |--C. regia Britton 1986B86
    |--C. rubida Britton 1986B86
    |--C. rubiginosa Britton 1986B86
    |--C. ruficeps (Burmeister 1855) [=Haplonycha ruficeps; incl. H. fimbriata Lea 1924]B86
    |--C. rufocastanea (Lea 1930) [=Haplonycha rufocastanea]B86
    |--C. rutila Britton 1986B86
    |--C. satelles Britton 1986B86
    |--C. scutalis (Blanchard 1851) [=Haplonycha scutalis; incl. C. testaceipennis Macleay 1888, H. testaceipennis]B86
    |--C. secreta Britton 1986B86
    |--C. setifera Britton 1986B86
    |--C. setosa Blackburn 1890 [=Haplonycha setosa]B86
    |--C. sinuaticollis Blackburn 1890 (see below for synonymy)B86
    |--C. sodalis Britton 1986B86
    |--C. solida Blackburn 1890 [=Haplonycha solida; incl. H. sloanei Blackburn 1906]B86
    |--C. sorella Britton 1986B86
    |--C. soror Britton 1986B86
    |--C. spadix (Blackburn 1906) [=Haplonycha spadix]B86
    |--‘Haplonycha’ striatella Blanchard 1851 (n. d.)B86
    |--C. suavis (Lea 1919) [=Haplonycha suavis]B86
    |--C. tarsalis (Lea 1924) [=Haplonycha tarsalis]B86
    |--C. tindalei (Lea 1926) [=Haplonycha tindalei]B86
    |--C. trichopyga (Blackburn 1906) [=Haplonycha trichopyga]B86
    |--C. unidens Britton 1986B86
    |--C. vanga Britton 1986B86
    |--C. velata Britton 1986B86
    |--C. vesca Britton 1986B86
    |--C. vicina Britton 1986B86
    `--C. villosa (Lea 1917) [=Haplonycha villosa]B86

Colpochila bella Blackburn 1890B86 [incl. Haplonycha amoena Blackburn 1906B86, H. cara Lea 1917B86, Colpochila gracilis Blackburn 1890B86, H. gracilisL19, H. iridipennis Lea 1917B86, H. neglecta Blackburn 1906B86, H. paradoxa Blackburn 1906B86]

Colpochila crassiventris Blanchard 1850B86 [incl. Haplonycha fimbricollis Lea 1924B86, H. roei Burmeister 1855B86, Colpochila roeiM86]

Colpochila obesa (Boisduval 1835)B86 [=Melolontha obesaB86, Aplonycha obesaB86, *Haplonycha obesaB86; incl. Melolontha destructor Tepper 1878B86, H. pectoralis Blanchard 1851B86, Colpochila tasmanica Blanchard 1853B86, H. tasmanicaM86, H. thoracica Blackburn 1906B86]

Colpochila sinuaticollis Blackburn 1890 [=Haplonycha sinuaticollis; incl. H. arvicola Blackburn 1906, H. egregia Blackburn 1906, H. electa Blackburn 1906, Colpochila fraterna Blackburn 1890, H. fraterna, H. rustica Blackburn 1906, H. sabulicola Blackburn 1906, H. semiopaca Lea 1917]B86

*Type species of generic name indicated

References

[B86] Britton, E. B. 1986. A revision of the Australian chafers (Coleoptera: Scarabaeidae: Melolonthinae) vol. 4. Tribe Liparetrini: genus Colpochila. Australian Journal of Zoology, Supplementary Series 118: 1–135.

[HW92] Houston, W. W. K., & T. A. Weir. 1992. Melolonthinae. In: Houston, W. W. K. (ed.) Zoological Catalogue of Australia vol. 9. Coleoptera: Scarabaeoidea pp. 174–358. AGPS Press: Canberra.

[L19] Lea, A. M. 1919. Notes on some miscellaneous Coleoptera with descriptions of new species.—Part V. Transactions of the Royal Society of South Australia 43: 166–261, pls 25–27.

[M86] Masters, G. 1886. Catalogue of the described Coleoptera of Australia. Part III. Proceedings of the Linnean Society of New South Wales, series 2, 1 (1): 21–126.

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