Machleida banachi, Machleida flagstaffensis, Machleida tarskii & Machleida zofiae: Four new species of Darkling Beetles from South Africa.

Darkling Beetles, Tenebrionidae, are a morphologically diverse group with over 20 000 described species, and many more still being discovered every year. The genus Machleida is one of seven southern African genera, with five described species, four of which are known from single localities in the Eastern Cape Province of South Africa, with the fifth being found in Madagascar, leading to its placement within the genus questioned by entomologists.

In a paper published in the journal ZooKeys on 10 January 2019, Marcin Kamiński of the Department of Biological Sciences at Northern Arizona University, the Department of Entomology at Purdue University, and the Museum and Institute of Zoology of the Polish Academy of Sciences, Kojun Kanda of the also of the Department of Biological Sciences at Northern Arizona University, and Aaron Smith, again of the Department of Biological Sciences at Northern Arizona University, and the Department of Entomology at Purdue University, present a review of the genus Machleida, in which they describe four new species and formarly remove the Malagasy species, Machleida nossibiana, from the genus.

The first new species is named Machleida banachi, in honour of Stefan Banach (1892-1945), a prominent Polish mathematician and founder of modern functional analysis. The species is described from five specimens, collected in 1988 in what was then the Transkei Republic (now part of Eastern Cape Province) by Hungarian entomologist Sebastian Endrödy-Younga, four from Ntsubane Forest in and one from Ingogo Forest. This species ranges from 8.0 to 9.5 mm in length and from 4.0 to 7.0 mm in width, and is brownish in colour with abundant yellow hairs. It is typically covered in debris from the leaf litter in which it lives.

Machleida banachi, dorsal view. Kamiński et al. (2019).

The second new species described is named Machleida flagstaffensis, meaning 'from Flagstaff', in reference to the town in Eastern Cape, which is near the location where the species was discovered. This species is also based upon material gathered by Sebastian Endrödy-Younga in 1988, from the Ntsubane Forest and the Silaka Forest Reserve, also in the Eastern Cape. This species is much larger, reaching 13.0–15.0 mm in length and 7.0–7.5 mm in width. It is also brownish in colour with abundant yellow hairs, and typically covered in debris from the leaf litter in which it lives.

Machleida flagstaffensis, dorsal view. Kamiński et al. (2019).

The third species described is named Machleida tarskii, in honour of the Polish-American logician and mathematician Alfred Tarski (1901–1983). The species is described from two specimens collected by the Belgian entomologist Narcisse Leleup (1912-2001), in the Pirie Forest near King William's Town in Eastern Cape. This species reaches 9.0–9.2 mm in length, and 5.0–5.2 mm in width, and is dark brown or yellow in colour with abundant yellow hairs, and typically covered in debris from the leaf litter in which it lives.

Machleida tarskii, dorsal view. Kamiński et al. (2019).

The fourth new species described is named Machleida zofiae, in honour of Zofia Irena Kamińska, the daughter of Marcin Kamiński. This species is described on the basis of a single specimen collected in 1985 by Sebastian Endrödy-Younga in the Dwesa Forest Reserve in what was then the Transkei Republic and is now part of the Eastern Cape. This specimen is 11.5 mm in length and 5.5 mm in width, and brownish in colour with a coating of yellow hairs and a covering of debris from the forest floor.

Machleida zofiae, dorsal view. Kamiński et al. (2019).

The single Malagasy representative of the genus, Machleida nossibiana, has been considered to be a doubtful placement for some time. This is not uncommon with Malagasy species described in the nineteenth century, when it was not realised to what extent Madagascar represented a separate biogeographical realm to Southern Africa. Based upon re-examination of this species Kamiński et al.consider it should be placed in the genus Scotinesthes, as Scotinesthes nossibianus.

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Insect borings in bones from the Rancho La Brea Tar Pits.

The Rancho La Brea Tar Pits are located in what is now central Los Angeles, California. They are essentially oil deposits identical to those worked by oil drills in other parts of the world, but exposed at the surface. When oil deposits are exposed in this way the lighter fractions (crude oil is made up of a mixture of different oils, known as 'fractions' due to the process used to separate them, fractional distillation) such as petroleum evaporate off, leaving the heavier fractions, known as tar, or asphalt, behind. These form oily pools in which animals can become trapped. The La Brea Tar Pits appear to have been exposed at least intermittently at the surface for around 40 000 years, during which time a great number of animals have fallen into them.

In a paper published in the journal PLoS One on 3 July 2013, Anna Holden of the Department of Entomology at the Natural History Museum of Los Angeles County, John Harris of the George C. Page Museum and Robert Timm of the Department of Ecology and Evolutionary Biology and Biodiversity Institute at University of Kansas discuss the results of a study of insect damage to bones from the La Brea Tar Pits, and the implications of these results for the climate and conditions under which the deposits were formed.

Holden et al. compared damage on preserved bones from the Tar Pits to damage created in the lab by allowing Beetle larvae to feed on Pig and Chicken bones. They found that the damage to the ancient bones matched closely with that created by Dermestid and Tenebrionid Beetle larvae.

Damage caused to bones by Dermestid Beetle larvae. (A) Damage caused to a Pig bone in the laboratory. (B & C) Damage to the bones of Bison from the Rancho La Brea Tar Pits. Holden et al. (2013).

This has implications for the climate at the time when the bones became trapped in the tar. The types of Beetles that Holden et al. think were causing damage to bones in the La Brea Tar Pits are associated with far warmer climates than those suggested by pollen inclusions in the tar. Holden et al. suggest that this actually helps to clear up a mystery surrounding the Tar Pits; based upon pollen analysis, the temperatures at the times when the deposits were forming would have been to cool for the tar to melt, leaving a solid asphalt which animals would simply have been able to walk across.

Damage to bones from Dermestid and Tenebrionid Beetle larvae. (A) Chicken bone damaged by Dermestid Beetle larvae in the lab. (B) Camel bone from the La Brae Tar Pits showing damage by both Dermestid and Tenebrionid Beetle larvae. Holden et al. (2013).

The warmer temperatures implied by the Beetle damage suggest that the temperatures were warm enough for the tar to melt at least periodically, suggesting a fluctuating climate. Most pollen grains used in climate studies come from trees, long lived plants which can survive fairly long periods outside their optimum temperature range. A tree that lives for a hundred years or more will not die out because there is the occasional decade in which it is too warm for it to reproduce (most organisms can survive outside the conditions which they need to reproduce successfully). Thus a fluctuating climate which occasionally produced summers, or even strings of summers, would be all that was needed to produce the fossils of the La Brea Tar Pits.

Bones showing damage from Tenebrionid Beetle larvae. (A & B) A Chicken bones damaged by Tenebionid larvae in the lab. (C) Horse bone showing signs of Tenebrionid damage from the La Brae Tar Pits. (D) Bison bone from the Tar Pits showing signs of Tenebrionid damage. Holden et al. (2013).

The extent of damage can also be used to estimate how long the bones were available at the surface. Unlike a mammalian scavenger, Beetles do not simply turn up, gnaw a bone then leave, but rather lay eggs on the bone, which have to have time to hatch, and then the Beetle larvae must spend some considerable time on the bone to make holes of any size - something which can be measuered by observing Beetles in the lab.

Bones showing damage from Tenebrionid Beetle larvae. (A) Chicken bone damaged in the lab. (B) Horse bone from the La Brea Tar Pits. Holden et al. (2013).

Based upon these calculations, Holden et al. conclude that the bones examined were available at the surface for around five months, suggesting that quite long periods of warm weather occurring, i.e. that the deposits were formed in times of long warm summers, something which supports the theory that the area was subject to climatic cycles rather than occasional freak warm weather.

See also A new species of Skin Beetle from Yunnan Province, China, Insect borings in Triasic wood and Fossil Owls from the La Brea Tar Pits.

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