Brachysternus prasinus
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| Brachysternus prasinus | |
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Scientific classification  | |
| Kingdom: | Animalia |
| Phylum: | Arthropoda |
| Class: | Insecta |
| Order: | Coleoptera |
| Suborder: | Polyphaga |
| Infraorder: | Scarabaeiformia |
| Family: | Scarabaeidae |
| Genus: | Brachysternus |
| Species: | B. prasinus |
| Binomial name | |
| Brachysternus prasinus Guérin-Méneville, 1830 | |
| Synonyms[1] | |
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List
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Brachysternus prasinus is a species of scarab beetle endemic to Chile and parts of Argentina.[2] It was named after French entomologist Félix Édouard Guérin-Méneville and belongs to the Rutelinae subfamily of the Scarabaeidae family. It is the most common species in the Brachysternus genus and the most varied in terms of color and type of setae. Due to this variability, B. prasinus have often been used in entomological studies as the species with which to compare all other Brachysternus species.[3] It ranges from 11 to 19 mm in length. Its body is green and its light brown legs have white hairs.[2]
Morphs
B. prasinus is often mistaken for the more well-known Hylamorpha elegans, also known as the San Juan beetle, as they are both found in the same habitat.[3] It can be differentiated from other Brachysternus beetle species because they have a well-developed supraspiracular ridge on the abdomen of male B. prasinus, as well as a deeply emarginate terminal sclerite on the legs of female B. prasinus. Other identifiers of B. prasinus include their clypeal apex (a part of the insect's head) that is weakly reflexed at its tip. B. prasinus have prothoracic legs. These prothoracic legs include femurs which are weakly rounded and dilated, as well as tibia with weak pro tibial notches.
Male and female B. prasinus differ slightly in their body shape. Male B. prasinus have the apex of the terminal sternite quadrate (a part of an insect's thorax or abdomen), while females are categorized as having the apex of the terminal sternite moderately to deeply emarginate. In other words, the bottoms of female B. prasinus are slightly more rounded than those of their male counterparts.[3]
There is a large amount of variation among Brachysternus and especially in B. prasinus. Due to this large amount of variation, there are several different morphotypes of B. prasinus. There have been many different proposed names for these varied morphotypes. One morphotype is endemic to the province of Talca, which encompasses Carrizalillo and Constitución, in central Chile. This morphotype is unique because of its more dense setose, found dorsally on their upper body.[3] While these setae on B. prasinus are typically orange in the central Chilean morphotype, the setose of B. prasinus are a darker metallic green color on the top of their body and a deeper chestnut color on the bottom part of their body.[clarification needed] This difference is thought to be due to changes in genetics across different locations. However, it has been argued that many of these morphotypes do not differ significantly and therefore should not be categorized separately. Some argue that these differences in color and setae type are due to B. prasinus having a vast range of normal phenotypes.[3]
Distribution and habitat
Brachysternus prasinus lives on the southwestern coast of South America, in Chile and parts of Argentina. The habitat of B. prasinus spans from the Valparaíso region to the Magallanes Province in Chile. B. prasinus is found in Argentina in the province of Neuquén and the Río Grande Department region which is a part of the Tierra del Fuego Province.[3] B. prasinus is seen across a wide range of elevations. It is found anywhere from elevations at sea level to 2,000 meters above it.[3] Their geographic range is highly dependent on the availability and distribution of Nothofagus, the species which B. prasinus feeds on.[3] B. prasinus have been observed in the Nothofagus forests near the cities of Coquimbo and Llanquihue in Chile as well as the areas of Neuquén and Chubut in western Argentina.[3]
Diet
Brachysternus prasinus lives in Nothofagus forests. It is hypothesized that the larvae of B. prasinus feed on dead and decaying wood as well as other vegetation similar to other Ruteline larvae. Adult B. prasinus often fly at dusk to other nearby Nothofagus trees for sustenance.[3] These Nothofagus forests consist mainly of the Nothofagus plant but also often include other plant species like Araucaria (Araucariaceae), Saxegothaea (Pinaceae), Drimys (Winteraceae), and Chusquea (Poaceae). Most of these plant species are plentiful from the months of November to February. The Valdivian rainforest district has two types of Northofagus including the deciduous Nothofagus obliqua and Nothofagus alpina, which is also called N. nervosa.[4]