tiger beetles

Platychile pallida (Fabricius 1801)

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Individuals of the monotypic genus Platychile occur on sandy beaches along the coast of Namibia and South Africa. The sole species, Platychile pallida, is an active forager at night but during the day retreats under kelp or into burrows along the high tide line. Kensley (1974) reports that these adult burrows are about a centimeter and a half deep.

At night, the adults forage along the low beach along debris lines and are principle competitors of juvenile Tylos sp. (Isopoda: Oniscidea) as both feed on animal matter, including washed up Physalia (Kensley 1974).

Prins (1984) notes the robust carabid beetle Acanthoscelis ruficornis (Fabricius, 1801) preys upon Platychile adults. If accurate this encounter must be quite the fight!

Arndt (1998) described the all larval instars of Platychile. The larvae are slender with an elongated and weakly sclerotized body. Of particular interest the abdominal hooks of Platychile larvae are shifted away the center of the fifth abdominal segment and located closer to each side. This is faintly visible in one of Arndt’s figures (reproduced in Handbook of Zoology, Vol. IV).

B Platychile pallida (Cicindelinae) (Arndt 1998b) angle horz

Johan Christian Fabricius described this species in his 1801 work Systema Eleutheratorum from material collected in southern Africa; however, he placed P. pallida in the genus Manticora. W.S. MacLeay established the genus Platychile in 1825 and placed P. pallida into this distinct genus. While at least five other species, subspecies, or variations of Platychile have been described each has not withstood scrutiny and P. pallida remains the only valid species in this unique genus.

Choate (2008) notes that P. pallida is a candidate for protection. I cannot find any further information regarding the threats to either habitat or population numbers. Other mentions of this species protection are confined to passing mention in drafts of South African protected species lists.

There is a photo of a live Platychile adult on flickr – you can find it here.

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Arndt, E. 1998. Larval description and natural history data of two genera of tiger beetles from Southern Africa (Coleoptera, Cicindelidae). Entomologische Blätter für Biologie und Systematik der Käfer. 94(1): 33-44.

Arndt, E., R.G. Beutel, and K.W. Will. 2005. Carabidae Latreille, 1802. [pp. 119–114.] In: Handbook of Zoology. Volume IV. Arthropoda: Insecta. Part 38. Coleoptera, Volume 1: Morphology and Systematics (Archostemata, Adephaga, Myxophaga, Polyphaga (partim) (R.G. Beutel and R.A.B. Leschen, editors). Walter DeGruyter GmbH & Co. KG, Berlin, Germany.

Choate, P.M. 2008. Tiger beetles (Coleoptera: Carabidae: Collyrinae and Cicindelinae) [pp. 3804-3818]. In: Encyclopedia of Entomology. 2nd Edition. (J.L. Capinera, editor) Springer.

Fabricius, J. C. 1801. Systema Eleutheratorum secundum ordines, genera, species: adiectis synonymis, locis, observationibus, descriptionibus. Impensis bibliopoli academici novi, Kiliae. 2 volumes. 506 + 687 pp.

Kensley, B. 1974. Aspects of the biology and ecology of the genus Tvlos Latreille. Annals of the South African Museum. 65: 401-471.

Macleay, W. S. 1825. Annulosa Javanica, or an attempt to illustrate the natural affinities and analogies of the insects collected in Java by Thomas Horsfield, M. D. F. L. & G. S. and deposited by him in the museum of the honourable East-India Company. Kingsbury, Parbury & Allen. London. xii + 50 pp.

Pearson, D. L. and A. P. Vogler. 2001. Tiger Beetles: The evolution, ecology, and diversity of the Cicindelids. Cornell University Press, Ithaca, New York, 333 pp.

Prins, A.J. 1984. Morphological and biological notes on some South African arthropods associated with decaying organic matter II: the predatory families Carabidae, Hydrophilidae, Histeridae, Staphylinidae and Silphidae (Coleoptera). Annals of the South African Museum. 92: 295-356.

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The Cicindela of Linnaeus

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Carl Linnaeus (or his ennobled name Carl von Linné or the latinate Carolus Linnaeus) laid the foundations for binomial nomenclature, modern taxonomy, and recognized the tiger beetles as a distinct group. As with much of Linnaeus’ writing the description of the genus is in Latin; in the first edition of Systema Naturae he erected the genus Cicindela, noting that unique appearance of the clypeus and the prominent mandibles.

 

From the publication of Systema Naturae and through subsequent editions until his death Linnaeus described eight tiger beetle species. While the species came from Europe, North America, and South Africa Linnaeus placed all eight species in the genus Cicindela. Later workers have dispersed these species across five genera and ajoined numerous subspecies since Linnaeus’ death in 1778.

Europe

Cephalota maura (Linnaeus, 1758)

Cicindela campestris Linnaeus, 1758

Cicindela hybrida Linnaeus, 1758

Cicindela sylvatica Linnaeus, 1758

 Cylindera germanica (Linnaeus, 1758)

North America

Tetracha carolina (Linnaeus 1767)

Tetracha virginica (Linnaeus, 1767)

South Africa

Habrodera capensis (Linnaeus, 1764)

References

Pearson, D. L., Cassola, F., 2005. A quantitative analysis of species descriptions of tiger beetles (Coeloptera: Cicindelidae), from 1758 to 2004, and notes about related developments in biodiversity studies. The Coleopterologists Bulletin, 59(2): 184-193.


Monographie des Cicindélides: Frontispice

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I don’t even know what to say!  This work of art is from James Thomson‘s 1857 “Monographie des Cicindélides” You can view the book online at Biodiversity Heritage Library.


Habroscelimorpha dorsalis dorsalis at last!

While I have assisted in a few surveys of Habroscelimorpha dorsalis dorsalis I had not been able to get a decent photo – until now. This past weekend I had the chance to stop and take a few photos of this Federally threatened subspecies at Savage Neck natural area preserve.

This subspecies is noticeably larger than its the other members of the dorsalis complex and, though camouflaged against the sand, is easy enough to spot. However, the beetles were quite flighty and very active making it a real challenge to get a photo. I was finally able to get shots of two males, one with greatly reduced maculations, a common occurrence in this species.

For more information on the dorsalis subspecies see here


why hello there…

This is a third instar larvae of Cicindela albissima – the Coral Pink Sand Dunes Tiger Beetle. I found the larvae to be virtually unapproachable during the day, but at night, with a little patience, I could get right up to their burrows. The head and pronotal coloration of the larvae is quite vivid – one of the most colorful that I’ve seen.

I photographed this individual and many more while I was doing some fieldwork back in 2010. I’ll post a best of from that trip in the coming month, if time permits.


Cicindela galapagoensis

A tiger beetle is hardly the first organism that comes to mind when the Galapagos Islands are mentioned. However, the Islands are home to a single endemic member of this subfamily, Cicindela galapagoensis.

Cicindela galapagoensis was first collected by then Stanford student F. X. Williams while he was serving as an entomologist on the California Academy of Sciences 1905-1906 expedition to the Galapagos. It was over ten years until this species was formally described, though this distinction went to German entomologist Walther Horn. In Coleoptera of the Galapagos Islands E.C. Van Dyke curtly mentions: “A tiger beetle collected by Williams was described by Dr. Walther Horn … as Cicindela galapagoensis. It had been submitted to him for his opinion.”

This species is represented by two color forms: a dark and a pale form. As one might suspect, this variation has led to some taxonomic confusion. The dark form of C. galapagoensis was described under the name Cicindela vonhageni in 1938, by American Museum of Natural History curator A.J. Mutchler, from 7 specimens collected by W. von Hagen. Additionally, a subspecies, C. galapagoensis discolorata, was described in 1967 from a single specimen collected on Genovesa Island. However, in 1976, Hans Reichardt synonymized vonhageni and galapagoensis discolorata with galapagoensis after finding evidence for only a single species based on the presence of intermediate forms in a large series of specimens.

Cicindela galapagoensis has been collected from seven major islands¹ where it inhabits sand beaches, mud flats, and salt tidal marshes. The adults have been collected at night with no reported observations of activity in the daytime. The larvae have been described and are found in similar habitats to the adults.

While C. galapagoensis is the sole endemic species of tiger beetle in the archipelago, a mainland species, Cicindela trifasciata was apparently introduced onto Santa Cruz Island and subsequently spread to several sites on during an extreme El Niño event in 1982-1983.  Since the apparent introduction, the trifasciata populations have grown to vastly out number the endemic speceis on the order of hundreds to one. As expected, the number of galapagoensis observed in recent studies has dramatically dropped at the sites where the two species co-occur, almost certainly due to fierce competition for prey and potentially larval habitat.

In addition, Cassola et al. noted that C. galapagoensis was not observed on Genovesa Island and, most distressingly, reported that the species primary habitat on the island, a small sand beach, had been incorporated into the tourist trail. The resultant trampling likely wiped out any larvae and rendered the habitat unsuitable, resulting in the extinction of this population.

Back in January, I have the privilege to spend ten days in the Galapagos. Though I did not see any tiger beetles, one of our stops was the beach at Genovesa, on Darwin Bay. We went ashore just after the equatorial sun rose and I was struck by the traces of human activity. Old graffiti was conspicuously emblazoned on the cliffs and footprints were almost everywhere across the small beach. As we proceeded down the beach the impact of foot traffic became even more apparent.

But, as a whole, Cicindela galapagoensis is not in danger. The Santa Cruz and Genovesa populations are not the rule and most of the species habitat is free from introduced competitors and the menace of human foot traffic. Adequate surveys are needed to assess the extent of tricfasciata colonization and the overall health of C. galapagoensis populations in order to develop management strategies. Ultimately, with careful management, this enigmatic species can continue to thrive.

Notes:

¹ Fernandina, Floreana, Genovesa, Isabela, Marchena, San Cristóbal, and Santa Cruz (Peck 2006)

References:

Cassola, F., Roque-Albelo, L., and Desender, K. 2000. Is the Galápagos endemic tiger beetle threatened with extinction? Noticias de Galápagos no. 61: 23–25.

Horn, W. 1915. Coleoptera, Fam. Carabidae, Subfam. Cicindelinae. In P. Wytsman, ed., Genera Insectorum, 82C: 209-487, pl. 16-23.

Mutchler, A.J. 1938. Coleoptera from the Galápagos Islands. American Museum Novitates 981: 1-19.

Van Dyke, E.e. 1953. The Coleoptera of the Galápagos Islands. Occasional Papers of the California Academy of Sciences 22: 1-181.


one from the archives…

Back in 2006 I photographed this female Cicindela sexguttata feeding on a caddisfly; the hapless  trichopteran had been attracted to my blacklight placed on a dirt trail along a stream. With the sunrise, I watched as the voracious tiger beetle happened along and was chowing down by the time I snapped this shot.