Dynastes Tityus
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''Dynastes tityus'', the eastern Hercules beetle, is a
species A species () is often defined as the largest group of organisms in which any two individuals of the appropriate sexes or mating types can produce fertile offspring, typically by sexual reproduction. It is the basic unit of Taxonomy (biology), ...
of
rhinoceros beetle Dynastinae or rhinoceros beetles are a subfamily of the scarabaeidae, scarab beetle family (biology), family (Scarabaeidae). Other common names – some for particular groups of rhinoceros beetles – include Hercules beetles, unicorn be ...
native to the
Eastern United States The Eastern United States, often abbreviated as simply the East, is a macroregion of the United States located to the east of the Mississippi River. It includes 17–26 states and Washington, D.C., the national capital. As of 2011, the Eastern ...
. The adult's elytra are green, gray or tan, with black markings, and the whole animal, including the male's horns, may reach in length. The
larva A larva (; : larvae ) is a distinct juvenile form many animals undergo before metamorphosis into their next life stage. Animals with indirect development such as insects, some arachnids, amphibians, or cnidarians typically have a larval phase ...
e feed on decaying wood from various trees.


Taxonomy and names

''Dynastes tityus'' is known by a number of
common name In biology, a common name of a taxon or organism (also known as a vernacular name, English name, colloquial name, country name, popular name, or farmer's name) is a name that is based on the normal language of everyday life; and is often con ...
s, including ''eastern Hercules beetle'', ''elephant beetle'' and ''ox beetle''.. Cite by It was first given a
scientific name In Taxonomy (biology), taxonomy, binomial nomenclature ("two-term naming system"), also called binary nomenclature, is a formal system of naming species of living things by giving each a name composed of two parts, both of which use Latin gramm ...
by
Carl Linnaeus Carl Linnaeus (23 May 1707 – 10 January 1778), also known after ennoblement in 1761 as Carl von Linné,#Blunt, Blunt (2004), p. 171. was a Swedish biologist and physician who formalised binomial nomenclature, the modern system of naming o ...
, in his 1763 work ''
Centuria Insectorum file:Centuria Insectorum.png, The first page of ''Centuria Insectorum'', as included in ''Amoenitates Academicæ'' ' (Latin, "one hundred insects") is a 1763 Taxonomy (biology), taxonomic work by Carl Linnaeus, and defended as a thesis by Boas Jo ...
'', where it was called ''Scarabaeus tityus''; when Linnaeus' genus '' Scarabaeus'' was divided into smaller genera, ''S. tityus'' was renamed ''Dynastes tityus''.


Description

Adults of both sexes are wide, and males are long, including a long horn (the pronotal horn) which projects forwards from the thorax of the male; a second horn (the clypeal horn) projects upwards from the head. ''Dynastes tityus'' is therefore "among the longest and heaviest beetles in the United States". The horns are used in battles between rival males competing for a mate; the size of the horn reflects the availability of food when the beetle was growing. Despite the size of the horns, ''Dynastes tityus'' is harmless to humans. The elytra are
green Green is the color between cyan and yellow on the visible spectrum. It is evoked by light which has a dominant wavelength of roughly 495570 nm. In subtractive color systems, used in painting and color printing, it is created by a com ...
,
gray Grey (more frequent in British English) or gray (more frequent in American English) is an intermediate color between black and white. It is a neutral or achromatic color, meaning that it has no chroma. It is the color of a cloud-covered s ...
, or tan, usually with black mottling. The pattern of spots is unique to each individual. Beetles that are found in the soil or in rotten wood often appear very dark, with the spots on the elytra obscured. This results from moisture which the shell has absorbed; when the elytra dry out, they return to their paler color. Moisture is stored on the outer layer of the elytra, called the epicuticle, which changes the angle at which light reflects off of the underlying layer, the exocuticle, which is composed of photonic crystals. Occasionally, both elytra may be a uniform
mahogany Mahogany is a straight- grained, reddish-brown timber of three tropical hardwood species of the genus ''Swietenia'', indigenous to the AmericasBridgewater, Samuel (2012). ''A Natural History of Belize: Inside the Maya Forest''. Austin: Universit ...
color, or one elytron may be pale with dark blotches, while the other is a plain mahogany color. ''Dynastes tityus'' was featured on a stamp issued by the
United States Postal Service The United States Postal Service (USPS), also known as the Post Office, U.S. Mail, or simply the Postal Service, is an independent agencies of the United States government, independent agency of the executive branch of the federal governmen ...
in October 1999.


Physiology

The external humidity level leads to the elytra color change for the eastern Hercules beetle. They change color from yellow-green to deep brown when they move from a low humidity environment to a high humidity environment. When the environment is dry, the space between the multilayers is filled up with air and the refractive index has a low value of 1. However, when the humidity increases, the air is replaced by water and the refractive index increases 1.33. The change in the level of refractive index alters the light transmission path, which eventually causes the visible color change. The eastern Hercules beetle has a multilayer body structure in which the exact composition has not been determined. The known components of the insect cuticle are chitin fibers and a proteinaceous matrix. They fuse with each other and build an ordered structure which can store energy to protect the wing and body. When the elytra appears deep brown under the high humidity environment, it can better defend the beetle from attacks and accidents. Furthermore, the elytra is more apt to regular protection and attack when it has the yellow-green color.


Distribution

The genus ''Dynastes'' is theorized to originate in South America. The North American lineage appeared after the closure of the Panama Isthmus 3.5 million years ago. This lineage has been further dispersed by the Transverse Volcanic Belt and the Sierra Madre del Sur into eastern and western species in North America. ''D. tityus'' lives in the eastern and
southeastern United States The Southeastern United States, also known as the American Southeast or simply the Southeast, is a geographical List of regions in the United States, region of the United States located in the eastern portion of the Southern United States and t ...
, from
New York state New York, also called New York State, is a state in the northeastern United States. Bordered by New England to the east, Canada to the north, and Pennsylvania and New Jersey to the south, its territory extends into both the Atlantic Ocean and ...
,
Illinois Illinois ( ) is a U.S. state, state in the Midwestern United States, Midwestern United States. It borders on Lake Michigan to its northeast, the Mississippi River to its west, and the Wabash River, Wabash and Ohio River, Ohio rivers to its ...
and
Indiana Indiana ( ) is a U.S. state, state in the Midwestern United States, Midwestern region of the United States. It borders Lake Michigan to the northwest, Michigan to the north and northeast, Ohio to the east, the Ohio River and Kentucky to the s ...
in the north to
Florida Florida ( ; ) is a U.S. state, state in the Southeastern United States, Southeastern region of the United States. It borders the Gulf of Mexico to the west, Alabama to the northwest, Georgia (U.S. state), Georgia to the north, the Atlantic ...
and the
Gulf of Mexico The Gulf of Mexico () is an oceanic basin and a marginal sea of the Atlantic Ocean, mostly surrounded by the North American continent. It is bounded on the northeast, north, and northwest by the Gulf Coast of the United States; on the southw ...
in the south, with eastern
Texas Texas ( , ; or ) is the most populous U.S. state, state in the South Central United States, South Central region of the United States. It borders Louisiana to the east, Arkansas to the northeast, Oklahoma to the north, New Mexico to the we ...
and western Arkansas marking the western limit of its range. The larvae of eastern Hercules beetles live in decaying wood. They prefer to reside and develop within the large cavity at or near the bases of the tree through which they can tunnel into the soil. The adults are observed to live in the vegetation and under moist leaf-litter. The fallen leaves and logs can protect the beetle from predation risks. They are also found to live on ash trees where the trees help them attract and locate mates.


Life history

Mating can last up to 50 minutes in ''D. tityus''. Subsequent batches of eggs are oviposited in the same site until its resources are exhausted. The larvae are large C-shaped grubs with white bodies and chewing mouthparts, which feed on decaying wood and litter within rotten trees and produce distinctive rectangular fecal pellets about long. After 12–18 months, the larvae
pupa A pupa (; : pupae) is the life stage of some insects undergoing transformation between immature and mature stages. Insects that go through a pupal stage are holometabolous: they go through four distinct stages in their life cycle, the stages th ...
te in late summer. Adults remain underground through the winter, initially remaining in their pupal cell. They emerge in the summer and live for 6–8 months. The adults' diet is not well known, but they have been observed lapping up the sap of ash trees. Oviposition happens during the summer and females lay up to 100 eggs in large cavities at or near the bases of the tree. Mature oaks and hardwoods are preferred. Females may share the same site to lay the eggs if there are enough accumulations of woody debris as food resources. The eggs are generally laid within or very close to the decaying wood so that the larvae would have enough nutrients without traveling too far. Thus, female investment towards the eggs happens before laying. No further parental care behavior is reported. The beetles undergo
metamorphosis Metamorphosis is a biological process by which an animal physically develops including birth transformation or hatching, involving a conspicuous and relatively abrupt change in the animal's body structure through cell growth and different ...
, which includes egg, larval, pupal and adult stages. Females lay the white-yellow eggs inside the soil during the summer. Eggs have an incubation period of about one month, followed by three larval instars, which refer to molting stages of the larvae. Larvae spend most of their time underground. The larvae are large C-shaped grubs with white bodies and chewing mouthparts, which feed on decaying wood and litter within rotten trees and produce distinctive rectangular fecal pellets about long, which functions has a house for them to develop during both larvae and pupae stages. Before turning into pupae, larvae spend six months to one year to grow and molt twice in the soil. The molting process accommodates more growth. The "teneral" state describes the soft-bodied state of the beetle right after molting where their body has a pale color. This process lasts for a few hours to wait for the cuticle to harden. The larvae turn into pupae in the next late summer within the constructed larva’s fecal pellets and surrounding woody debris. Pupae turn into adults in about a month. They stay underground within their pupal cell through the winter and emerge in the next summer. The lifespan of adult beetles varies from 6 to 23 months. Individuals and mating pairs are commonly found to stay on the ash trees and scrape off the bark and feed on sap. The complete development may take up to three years in the wild. The larvae are saproxylophagous, meaning they feed on dead wood, such as rotten logs and decaying tree trunks.


Predation

Different
predator Predation is a biological interaction in which one organism, the predator, kills and eats another organism, its prey. It is one of a family of common List of feeding behaviours, feeding behaviours that includes parasitism and micropredation ...
s attack different life stages of ''Dynastes tityus''. The eggs are vulnerable to attack from a predatory
mite Mites are small arachnids (eight-legged arthropods) of two large orders, the Acariformes and the Parasitiformes, which were historically grouped together in the subclass Acari. However, most recent genetic analyses do not recover the two as eac ...
. The grubs are eaten by
mammal A mammal () is a vertebrate animal of the Class (biology), class Mammalia (). Mammals are characterised by the presence of milk-producing mammary glands for feeding their young, a broad neocortex region of the brain, fur or hair, and three ...
s including
skunk Skunks are mammals in the family Mephitidae. They are known for their ability to spray a liquid with a strong, unpleasant scent from their anal glands. Different species of skunk vary in appearance from black-and-white to brown, cream or gi ...
s and
raccoon The raccoon ( or , ''Procyon lotor''), sometimes called the North American, northern or common raccoon (also spelled racoon) to distinguish it from Procyonina, other species of raccoon, is a mammal native to North America. It is the largest ...
s, and soil-dwelling
arthropod Arthropods ( ) are invertebrates in the phylum Arthropoda. They possess an arthropod exoskeleton, exoskeleton with a cuticle made of chitin, often Mineralization (biology), mineralised with calcium carbonate, a body with differentiated (Metam ...
s, including
centipede Centipedes (from Neo-Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', "lip", and Neo-Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, ...
s,
ground beetle Ground beetles are a large, cosmopolitan distribution, cosmopolitan family (biology), family of beetles, the Carabidae, with more than 40,000 species worldwide, around 2,000 of which are found in North America and 2,700 in Europe. As of 2015, it ...
s,
spider Spiders (order (biology), order Araneae) are air-breathing arthropods that have eight limbs, chelicerae with fangs generally able to inject venom, and spinnerets that extrude spider silk, silk. They are the largest order of arachnids and ran ...
s and the maggots of Mydas flies. A tiny mite that burrows through the soils and feeds on the larvae. They are very similar in color to the eggs. The species has not been determined yet. Mydas fly larvae also feed on the eggs by burrowing through soil.


Mating

Males have been observed to release a pungent odor which is similar to blueberries. It is speculated that this scent is used to attract females. It has been shown that ash plays an important role in attracting and locating mates, which explains why adults live on ash instead of tree cavities. Males would scrape the bark and chew into the cambium of ash branches.


Similar species

''
Dynastes ''Dynastes'' is a genus of large beetles belonging to the family Scarabaeidae. They occur in the Nearctic realm and in the Neotropical realm, from the United States to Brazil;Americas The Americas, sometimes collectively called America, are a landmass comprising the totality of North America and South America.''Webster's New World College Dictionary'', 2010 by Wiley Publishing, Inc., Cleveland, Ohio. When viewed as a sing ...
and only two of the eight species occur in the
United States The United States of America (USA), also known as the United States (U.S.) or America, is a country primarily located in North America. It is a federal republic of 50 U.S. state, states and a federal capital district, Washington, D.C. The 48 ...
. While ''D. tityus'' inhabits the eastern United States, '' Dynastes grantii'' (the western Hercules beetle) live at higher elevations in
Arizona Arizona is a U.S. state, state in the Southwestern United States, Southwestern region of the United States, sharing the Four Corners region of the western United States with Colorado, New Mexico, and Utah. It also borders Nevada to the nort ...
,
New Mexico New Mexico is a state in the Southwestern United States, Southwestern region of the United States. It is one of the Mountain States of the southern Rocky Mountains, sharing the Four Corners region with Utah, Colorado, and Arizona. It also ...
and
Utah Utah is a landlocked state in the Mountain states, Mountain West subregion of the Western United States. It is one of the Four Corners states, sharing a border with Arizona, Colorado, and New Mexico. It also borders Wyoming to the northea ...
. Several species are found in Mexico with '' Dynastes hyllus'' found as far north as
Tamaulipas Tamaulipas, officially the Free and Sovereign State of Tamaulipas, is a state in Mexico; one of the 31 states which, along with Mexico City, comprise the 32 federal entities of Mexico. It is divided into 43 municipalities. It is located in nor ...
. ''D. tityus'' and ''D. grantii'' are very similar, and it is possible to interbreed them and produce viable hybrids.


Interaction with humans

''D. tityus'' possess elytra that are light and strong, and the purpose of elytra is to protect the beetle’s
hindwings Insect wings are adult outgrowths of the insect exoskeleton that enable insects to fly. They are found on the second and third thoracic segments (the mesothorax and metathorax), and the two pairs are often referred to as the forewings and hindwi ...
. Their unique and beneficial elytra has inspired applications to the human world. The beetle’s elytra is made up of chitin fibers and a proteinaceous matrix. The elytra of ''D. tityus'' can be used as a biological blueprint for the development of light and strong materials. ''D. tityus'' can also change color from green to black based on environmental humidity. They change to black when the humidity increases. Bio-inspired models from ''D. tityus'' include micro structures. From human structures, the materials used should be composite and fabricated in layers. Bonding between layers can be enforced by placing fibers in each layer and cross layer to obtain a bonding force. Another bio-inspired model is the varying hardness between layers. The hardness of bio-inspired materials should be different and the direction of the materials in the layers should also be different.


References


External links

* Includes an image of the postage stamp featuring ''D. tityus''. {{Taxonbar, from=Q644708 Dynastinae Beetles of North America Beetles described in 1763 Taxa named by Carl Linnaeus