Xylotrupes+gideon

=__**Overview**__= Below is a guide through my species page. If you're a hardcore beetle lover, or maybe just really bored, you are free to read this page from top to bottom. If not, you may use the flowchart below to help you find the section you're interested in, and click the link in the table of contents to arrive at your desired destination.
 * Brown Rhinoceros Beetle**  //**Xylotrupes gideon**// **(Linnaeus, 1767)**  [[image:7894265378_66206a5dd7_o.jpg width="493" height="363"]] [[image:kwang-5.jpg width="496" height="369"]] Left: //Xylotrupes gideon//, adult male. Image by Bernard Dupont, used under Creative Commons Attribution-NonCommercial License. Right: Male //X. gideon// fighting. Image by Uthen Kamsurin (permission pending)

toc =__Introduction__=

**What is a rhinoceros beetle?**
The term rhinoceros beetle, or rhino beetle for short, is commonly used to refer to any kind of horned beetle, and most often refers to species from the subfamily Dynastinae (a majestic and fitting name indeed). The Dynastines are one of the most recognisable groups of beetles, due to their relatively large size and the massive facial horns present in many species (For more diagnostic characters, see As a Species). These signature horns are usually only present in adult males, and often used for macho man-to-man battles for honour and the hands of pretty beetle ladies. As to why they're called Rhinoceros beetles, it should be pretty obvious unless you have no idea what a Rhinoceros looks like.

Rhinoceros VS //Oryctes rhinoceros.// Not to scale, as cool as it would be to have giant beetles roam the earth. Rhinoceros image by Peter Miller, used under Creative Commons Attribution-NonCommercial License. //Oryctes rhinoceros// image by Sean Yap.

Strength
Rhinoceros beetles are famous for their purported power, with anecdotal accounts of ridiculously impressive feats strength. An entry in the Guinness Book of World Records claims that the strongest animal was a rhinoceros beetle that could support 850 times its body mass. More credibly, scientific investigation that - in all seriousness, involves beetles carrying little dumbbells while walking on tiny treadmills - found that dynastine beetles could still move with a load 100 times its body mass, and could sustain regular walking speed with a load 30 times their body mass. This means that the beetles are able to move heavy loads with great effeciency, such that investigating scientists are unsure about how it is possible with existing knowledge of biomechanics and metabolic costs[6]!

Not even kidding. Image by Rodger Kram[5], permission pending.

VS Stag beetles
Quite often, rhinoceros beetles are confused with stag beetles (Family Lucanidae) by the layperson, as both are usually portrayed with large horn/antler-like head ornaments used for fighting. However, the grappling ornaments (antlers) of stag beetles are their enlarged mandibles (mouthparts), while the rhino beetles employ the use of their facial and thoracic horns in combat, and do not use their mouths to fight (which is admittedly a lot less gross). Because the rhino beetle horns and stag beetle antlers move along perpendicular planes, they happen to interlock nicely when facing off against each other, rhino and stag beetles are often pitted against each other in the popular japanese beetle fights. Another noticeable difference between the two - while rhino beetles have deeper, rounder bodies like sausages, stag beetles are dorsoventrally flattened like pancakes. These differences are denoted in the pictures below. Comparison between //Xylotrupes gideon// and //Aegus parallelus//, a native stag beetle. //Xylotrupes gideon// images by Sean Yap. //A. parallelus// images by John Ska (lateral view) and Udo Schmidt (dorsal view), used under Creative Commons Atribution-Share Alike License.

=__As Warriors__= Rhinoceros beetles are also famous for their fighting ability. In Japan, rhino beetles are known as 'kabutomushi', which when translated means 'helmet bug', supposedly from the way the beetles' horns resemble the ornaments on samurai helmets (kabuto). Some samurai helmets, especially the 'kawari kabuto' (strange helmet), were elaborately shaped with large ornaments such as horns. Image by Ian Armstrong, used under Creative Commons Atribution-Share Alike License.

Mating
Female rhino beetles are sexy and they know it, and they usually just sit atop trees, wafting their pheromones to get the boys to come to them. More often than not, multiple guys will be attracted to a single female, and they land on a tree, ascending in search of her. This becomes a battle to the top, and males that encounter each other on the tree grapple each other and engage in wrestling matches, in which the loser is lifted off the tree and tossed to the bottom, having to start his climb from scratch.

If beetle horns and size are so important in getting to reproduce, one would expect only the largest and strongest males to survive, but reality is never as we expect. The brown rhinoceros beetles have male morphs that vary a lot in size of both the body and the horns, where smaller males have correspondingly smaller horns. But how do these pretty boys get around the alpha males and get to pass on their genes such that small size remains in the gene pool?

Minor (3.8cm) and major (6cm) adult male //Xylotrupes gideon//. Image by Sean Yap. While the benefits of smallness is still relatively understudied for dynastid beetles, studies with the horned, //Onthophagus// dung beetles have proposed the possibility of sneak mating, where effeminate males fool the buff alpha males into thinking that they're female, thus getting around them without direct confrontation (in which they would most certainly lose) in order to mate with the actual females - with the large males none the wiser!

[|Beetle fighting]
In Thailand, the brown rhino beetle is known as 'Kwang', and betting on beetle fights is a popular past time, especially among men. The sport has recently been outlawed in the state, though there are still hidden beetle fighting rings. Head on to[| this site]for great photos and descriptions of how the beetle fights work!

media type="youtube" key="er2fBwsOM4M" width="560" height="315" align="center" Underground beetle fight club in Chiang Mai, Thailand. Obtained from YouTube under Fair Use guidelines. media type="youtube" key="82gwHUIMJWg" width="560" height="315" Selecting the best fighters for battle. Video by Daniel Ambuehl, obtained from YouTube under Fair Use guidelines.

=__As Pets__= Beetle breeding is big business, especially in Japan and Thailand, where beetles are not only used for fighting but also often kept as pets. Some individual beetles can even be sold for as much as a [|thousand USD]! media type="youtube" key="DOJi2ihWVPw" width="560" height="315" align="center"

Beetle breeding at the Siam Insect Zoo. Video by Daniel Ambuehl, obtained from YouTube under Fair Use guidelines.

Before embarking on a journey with your pet beetle, one should first understand the life cycle of the beetle.

Life cycle
As a beetle, rhino beetles undergo complete metamorphosis. Female //X. gideon// lay an average of about 55 eggs [cite Bedford, 1975] in rotten leaves, sawdust or decaying wood. As larvae, the beetles spend a lot of time in nutrient-rich soils and decaying wood, where they pupate for about 46 days before emerging as adults. Adults live for about 90 - 102 days in captivity (Bedford, 1975). Life cycle of //X. gideon//. Images by Alessandro Siletto (egg), Rachael Moore (grub), JC Shou (pupa), Lai Wagtail (adult). Used under Creative Commons Attribution-NonCommercial License. = =

=__As Food__= Entomophagy is the sciencey word for eating bugs, and this new trend is taking the world by storm. In Laos and Thailand, //Xylotrupes gideon// is one of the species that is eaten by locals, both grubs and adults. It is known as 'Maeng kee noon' in Thai, and 'Mang kwang' in Lao. In Thailand, the beetles are usually wok-fried and seasoned with sauce and pepper powder, to be consumed as a snack food on its own or with beer. A fried insect stand in Thailand. Image by Su-Lin, used under Creative Commons Attribution-NonCommercial License. The eating of insects has always been part of Southeast Asian culture (Bristowe, 1932). More recently, entomophagy has become recognised in the west as the future of food, being relatively sustainable and high in nutritional value. There is an exotic selling point as well, and the two factors have contributed much to the fried insect economy. Business is gaining so much traction that companies have started exporting edible insects from Thailand.

Packaged edible beetles. Note that the image on the bag shows a male Japanese rhino beetle (//Allomyrina dichotoma//), while the contents are female //X. gideon//. Images by Sean Yap.

The beetles that are imported come boiled and dehydrated instead of fried, and are actually pretty difficult to eat. The exoskeleton is really tough, and the sharp spines on the legs threaten to make your gums bleed. Definitely not for the faint-of-heart!

media type="youtube" key="Jv1uC0ZOfyk" width="560" height="315" align="center"

Eating a female //X. gideon//. Video by Sean Yap, with permission from persons portrayed. Interestingly, in areas such as plantations where //X. gideon// has become a pest species, local tribes have been encouraged to eat them as a possible way of controling the beetle population (Wongdao & Black, 1987).

=__As Pests__= Throughout their range, //X. gideon// is a known pest species that targets palms such as coconut, but sometimes also goes for the bark of fruit trees (Wongdao & Black, 1987). It is known to feed on newly opened coconut inflorescences and the undersurface of frond midribs, causing the distal portion to break and hang down, affecting the survivability of coconut trees. Apart from tree bark, //X. gideon// can also attack fruits such as guava, apples and pears (Wongdao & Black, 1987). It is generally regarded as a minor pest though, and is not feared as strongly as its cousin, //Oryctes rhinoceros//.

=__As Pop Culture Icons__= Japan is crazy about insects, particularly beetles, and a popular trope in television and gaming series and franchises is the '[|Japanese Beetle Brothers]' trope, where characters designed to resemble rhinoceros beetles and stag beetles are often portrayed as allies or rivals. Below are a few examples.
 * Type A: Allies. Usually introduced at the same time, constantly work together and are seldom seen apart. Often either partners or brothers.
 * Type B: Rivals. They can't stand each others' guts, constantly butt heads and at times are on opposite sides.
 * Type C: Coincidental. This is the rarest of the three types, and occurs when just by chance, a rhino beetle and a stag beetle exist in the same fictional universe, much like their real-life counterparts.

Heracross is rhino beetle Pokemon with the Bug/Fighting type category, a reference to real life beetle fighting. It does share a universe with the stag beetle Pokemon Pinsir, but they do not interact significantly and are thus a type C beetle brothers. Heracross and Mega Heracross, Pokemon inspired by the beetle fighting culture. Artwork by the Ken Sugimori, used in accordance with [|Fair Use guidelines]. Kabuterimon (rhino beetle) and Kuwagamon (stag beetle) from the Digimon franchise are a classic case of Type B, where the two fight every time they meet. Kabuterimon and Kuwagamon. Official artwork by Bandai, used in accordance with Fair Use guidelines. In the live action series Kamen Rider Kabuto, the red rider Kabuto (rhino beetle) and the blue rider Gatack (stag beetle) start out as rivals but soon become fast allies, exemplifying type A. Kabuto and Gatack from the Kamen Rider Kabuto series by Toei, used in accordance with Fair Use guidelines. =__As a Species__=

Appearance
Like its common namesake, this species is largely brown colour, though variation exists between individuals, with some so dark they look almost black. The elytra (hardened forewings that protect the flight hindwings) are relatively smooth and without punctures. These are large beetles, with sizes ranging from about 35 - 70mm for most individuals. Large, bifurcate (two-pronged) horns are present in adult males, but absent in females. Adult male major and minor //Xylotrupes gideon// to scale. Major is 60mm in length, minor is 38mm. Image by Sean Yap, specimen collected by Max Khoo De Yuan.

Type Specimen
The type specimen for //Xylotrupes gideon// resides in the Linnaean Collections of the Linnaean Society of London. It is a male individual labelled with the basiosynonym name, //Scarabaeus gideon//. The label suffers from a real information deficit. Also, the poor specimen appears to have lost his head. Holotype for the species //Xylotrupes gideon//. Images from the Linnaean Society of London, pending permission.

How to identify - diagnosis
//Xylotrupes// species are pretty difficult to tell apart from external morphology, and often dissection of genetalia is required. The raspula is a sclerotized piece in the internal sac of the male genitalia of a beetle. The position of this part of the genatilia is shown in the diagram below.

A: General Scarabaeinae male genitalia; B: Internal sac; C: Raspula of //X. gideon//. Image adapted from Zunino, 1978 & Rowland, 2003 (permission pending) The following are characters with which to diagnose //Xylotrupes gideon//: Raspular autapomorphs include a very strongly angled right raspula; a very large right raspular bulb; a very long right raspular process originating on the mesal aspect of the raspula and upon which the left raspula is articulated distally; downward reflection of the left raspular cup; the very small size of the left raspula; the median lobe of the aedeagus with lyriform distal invagination. The diagrams below show the difference in shape of the raspula from a closely related species with a small range overlap, //Xylotrupes ulysses//. Variation in raspular shape within the //Xylotrupes// genus. Image adapted from Rowland, 2003 (permision pending)

In Singapore
//Xylotrupes gideon// is found throughout Southeast Asia, including Singapore. In Singapore, this species is easily recognisable as one of our largest beetles, and the largest horned species. The only other horned dynastine beetle in Singapore is //Oryctes rhinoceros//, which is a basically a smaller, less impressive cousin of //X. gideon.//

//Oryctes rhinoceros//, image by E. L. Engasser, permission pending. Presented below are some recognisable differences between the two species. The main difference to look out for is the two-pronged facial (cephalic) and thoracic horns, which together are a character only seen in //Xylotrupes// species. This also works for the minor //Xylotrupes// males, which have smaller horns but that are still two-pronged.

Distribution
//Xylotrupes gideon// can be found throughout South and Southeast Asia, as well as northern Oceania. Map showing records of //X. gideon// in South and Southeast Asia and Oceania. Map ©Designed by The Polistes Corporation, records from the Global Biodiversity Information Facility.

Habitat
//Xylotrupes gideon// is usually found in forested areas, as well as in palm plantations where it is considered a pest. (For more detail, jump to As a Pest) In Singapore, this species is now relatively uncommon, and sightings are sporadic and random. They sometimes end up in peoples' homes at night, attracted by artificial lighting.

Classification
Warning: Here onwards is where things get pretty technical. //Xylotrupes gideon// was first described by Linnaeus in 1767 as //Scarabaeus gideon//, before Hope established //Xylotrupes// as a genus in 1837 with //Scarabaeus gideon// as the type. //Xylotrupes// was one of the 10 recognised genera from the Dynastini tribe in Endrodi (1985), but has since been determined to be inadequately diagnosed and has been re-diagnosed in 2003 by Rowland.

The genus //Xylotrupes// can be differentiated from other members of tribe Dynastini via its unique apomorph of the constitution of the right raspula as a single large spine [cite Rowland]. Also, only //Xylotrupes// has the following character combination in this tribe: Apically bifurcate pronotal and cephalic horns, with the pronotal horn the same size or longer than the cephalic horn in major males.

The higher classifications, synonyms and subspecies of //Xylotrupes gideon// according to the latest revision by Rowland are listed below.

Higher Classification
**- Kingdom** Animalia (Animals)  **-** **Phylum** Arthropoda (Arthropods)  **- Subphylum** Hexapoda (Hexapods)  **- Class** Insecta (Insects)  **- Order** Coleoptera (Beetles)  **- Suborder** Polyphaga (Water, Rove, Scarab, Long-horned, Leaf and Snout Beetles)  **- Superfamily** Scarabaeoidea (Scarab, Stag and Bess Beetles)  **- Family** Scarabaeidae (Scarab Beetles)  **- Subfamily** Dynastinae (Rhinoceros Beetles)  **- Tribe** Dynastini  **- Genus** Xylotrupes
 * - Species** gideon

Synonyms
Sometimes, different names are assigned to the same species. This usually happens when a scientist describes a species that has already been described earlier, perhaps unaware of the existing name, or mistaking a morphological variant within the species as a new species. In such a case, the earlier name is treated as the accepted senior synonym, while all names that come after it are considered junior synonyms and generally should not be used. Synonyms can also be the original name of the species when it was first described, that may no longer be correct to use if the species has been transferred to another genus afterwards. This is that case with the name //Scarabaeus gideon//, the name that Linnaeus first gave the species when it was described in 1767. Since the species has been transferred to the genus //Xylotrupes//, the name //Scarabaeus gideon// should no longer be used.

//Xylotrupes gideon// is a species with a relatively large number of synonyms. This is partly due to the fact that it was also known by the genus //Scarabaeus// for about 70 years, a time span that allowed for the creation of numerous synonyms under that genus name. This list of //Scarabaeus// synonyms add on to the list of synonyms under the genus //Xylotrupes//. //Xylotrupes gideon// is also a relatively charismatic species with many interactions with humans as pests or as a part of local culture, and is likely to get much attention from beetle workers. This, coupled with the fact that some subspecies of //X. gideon// show significant intraspecific morphological variation, especially between males, could have lead to higher frequency of workers wrongly describing //X. gideon// individuals as new species. A list of synonyms for this species is listed below.

//Scarabaeus gideon// Linnaeus 1767 //S. oromedon// Drury 1770 //S. phorbanta// Olivier 1789 //Geotrupes dentatus// Wever 1801 //S. Scorticum// Voets 1806 //S. simson// Voets 1806 //S. nimrod// Voets 1806 //S. furciger// Voets 1806 //S. alcibiades// Dejean 1833 //Xylotrupes beckeri// Schaufuss 1885 //X. beckeri// var. //metzeneri// Schaufus 1887 //X. inarmatus// Sternberg 1906 //X. gideon gideon// Minck 1920 //X. sumatrensis// Minck 1920 //X. borneensis// Minck 1920 //X. bourgini// Paulian 1945 //X. gideon beckeri// Endrodi 1951 //X. gideon sumatrensis// Endrodi 1951 //X. gideon borneensis// Endrodi 1951

Subspecies
While different websites have different lists of //X. gideon// subspecies, Rowland asserts that material of this widespread species has not yet been sufficiently examined to support a comprehensive subspecific classification. In Singapore, the local subspecies is likely to be //Xylotrupes gideon beckeri// (Rowland, 2003).

Phylogeny within //Xylotrupes//
A phylogenetic study of the genus //Xylotrupes// exists, taking into account only morphological characters (Rowland, 2003). Characters used in the construction of this phylogeny include the length of pronotal (thoracic) horn relative to the cephalic (face) horn, the position of the cephalic horn tooth, number of mandibular teeth, and raspula shape. The tree below was obtained, showing the proposed relationship between //X. gideon// and other species from the genus //Xylotrupes//, with a //Trypoxylus// species as the outgroup as //Trypoxylus// has been found to be the sister group to //Xylotrupes//. Phylogenetic tree for //Xylotrupes//, with //Trypoxylus dichotomus// as the outgroup. Discovered by exhaustive search algorithm of PAUP 4.1 using 19 characters. Consistency index 0.91, retention index 0.94, length of 21 steps. HTU = hypothetical taxonomic unit; C = convergence; R = reversal. From Rowland, pending permission from the author. Rowland's phylogenetic analysis shows that only two apomorphs (derived characters), both in the raspula, distinguish //Xylotrupes// from other dynastine genera. The assumed monophyly of the genus however, is supported by the combination of other characters.

Phylogeny within tribe Dynastini
Rowland and Miller have more recently presented the first inclusive phylogenetic analysis of the Dynastini tribe of giant rhinoceros beetles, which contains the genus //Xylotrupes. Twenty species representing each genus within the tribe were included as ingroup taxa for the analysis, which includes morphological, biogeographical and molecular data.

Morphological characters used in this analysis include mandible incisor denticulation (how toothy the mandibles are), the presence of cephalic and pronotal horns in different arrangements, presence of sexual dimorphism in the legs, shape of raspulae, and colour of dorsal integument.

For the molecular analysis, four genes were sequenced - Cytochrome c oxidase II (COII), 16S rRNA (16S), histone III (H3) and arginine kinase (ArgKin).

The phylogeny was estimated using a combined equal-weights parsimony analysis using the program NONA (Goloboff 1995 ) as implemented by WinClada (Nixon 2002 ) using the heuristic command settings “hold 10000”, “mult*100”, “hold/40” and “multiple TBR + TBR”. Bootstrap values were used to measure branch support. These were calculated with NONA and WinClada using 1000 replications, 10 search reps, 1 starting tree per rep, “don’t do max*(TBR)”, and save the consensus of each replication. The resulting fully resolved cladogram from the parsimony analysis is shown below.



On the left is the single most parsimonious cladogram resulting from analysis of morphological and molecular data, while a summary tree is shown on the right. Numbers immediately above hashmarks are morphological character numbers. Numbers below hashmarks are character state numbers derived on that branch. Numbers in bold above branches are bootstrap support values. Inset branching diagram is single most parsimonious cladogram from analysis of all data with branch lengths proportionate to number of character state transformations mapped using “fast” optimization. From Rowland and Miller, pending permission from the authors.

The trees show that the genus //Xylotrupes// is sister to //Allomyrina//, a genus of japanese rhinoceros beetles. This group, is in turn sister to a group containing //Trypoxylus// (also a japanese rhinoceros beetle) and //Xyloscaptes//. This is an interesting result, as in terms of horn morphology, //Xylotrupes// is more similar to //Xyloscaptes// while //Allomyrina// and //Trypoxylus// look almost identical, but the groupings show a relationship differing from expectations. In any case, the four genera are well-supported as monophyletic, with Rowland and Miller proposing recognition of Xylotrupina as a valid subtribe.

=__References__=