Overview

Brief Summary

Taxonomy

The species was first described by Carolus Linnaeus in 1771.

Beetle, not cockroach!
When they first see it, many people think that Titanus giganteus looks like an enormous cockroach, because of its:
  • flattened body
  • long, relatively soft wing cases
  • long spiny legs
  • long antennae
Nothing could be further from the truth. Titanus is a true beetle, belonging to a group called the holometabolous insects - insects which have a distinct larval and pupal stage in their development. The group also includes:
  • butterflies
  • flies
  • wasps
  • bees
In contrast, a cockroach is a hemimetabolous insect - immature forms look, and live, like miniature versions of the adults. Other hemimetabolous insects include:
  • grasshoppers
  • crickets
  • greenflies
  • earwigs
The 2 groups are only distantly related and they separated hundreds of millions of years ago. Any resemblance that this giant beetle has to a cockroach is entirely superficial, probably because both insects evolved in similar environments, pushing through tropical forest leaf-litter.Unlike Titanus though, some cockroaches have also adapted to live in our houses!
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Introduction

Titanus giganteus is the world’s biggest beetle. The largest recorded specimen was a 16.7cm long male - longer than some small adult Chihuahua dogs - and was collected in French Guiana by entomologist Patrick Bleuzen.In spite of its imposing size, large jaws, sharp spines, and the ability to hiss and to fly, Titanus are quite harmless to humans.They live unobtrusively, deep in some of the world’s hottest tropical jungles, where the giant grubs recycle decaying wood below ground. The adults are active for a few weeks, seeking out a mate during the hottest and most humid time of the year.Like most inhabitants of the rainforest, this magnificent giant insect is threatened by the destruction of its forest home for timber and agriculture.
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Comprehensive Description

Biology

Very little is known about the biology of Titanus giganteus, though it probably has a very similar life cycle to other members of the subfamily, including the Tanner Beetle Prionus coriarius, a small relative that is widespread (though rare) in southern Britain.Most prioninae feed as larvae in buried decaying wood, probably for several years, with adults emerging for a brief annual flight period during which they reproduce and die.The adults of most species in this group are thought not to eat. Dr Michael Balke brought back a live male Titanus from French Guiana, which lived for a few weeks and is now in the Natural History Museum collection - this is approximately the adult life expectancy for many large beetles. During this time it was rather active, and could be induced to fly if the temperature was high enough. But it could not be persuaded to eat - it was offered fruit and tissue soaked in sugar solution, and was occasionally seen to mouth these substances, though not to actively feed.It is not uncommon for adult insects to survive entirely on resources stored during the larval stage, and some, for example many silk moths, completely lack a mouth and intestine.Adult males have an impressive threat display when disturbed:
  • they make a loud hissing sound by expelling air from their ‘spiracles’ (or breathing holes) along the sides of the body
  • they also have defensive spines on the inside margins of the legs (absent in the female) and on the sides of the thorax
  • and an impressive pair of ‘nutcracker’ jaws that can break a pencil or make star shaped cracks in a plastic ruler
If carelessly handled, they can scratch the fingers with their defensive spines. Like the British stag beetle, it is best to avoid putting fingers directly into the jaws of a large living specimen! However, all of this behaviour is entirely defensive and the beetle will try to escape before resorting to this threat display.It is not known what the natural predators of Titanus giganteus are, but these may include:
  • large birds
  • large fish (when they fly into the water)
  • mammals, such as:
    • coati
    • larger monkeys
    • smaller cats such as ocelot and margay
    • foxes
    • mink-like tayra
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Ecology

General Ecology

Distribution ecology

Titanus giganteus is found in good quality tropical rainforest across parts of northern South America, especially:
  • north Brazil
  • the Guianas
  • Colombia
It has also been found in Ecuador and Peru.Most specimens today come from French Guiana, and it was there that Sir David Attenborough filmed this spectacular insect for the BBC television series Life in the Undergrowth.This giant beetle - one of the largest of all living insects - is restricted to the hot, wet, tropics, in areas more or less adjoining the equator.The larvae of most prionine longhorns (the group to which it belongs) develop in dead subterranean wood, and Titanus is probably no exception. The larvae, which look like pieces of vacuum cleaner hose, are rather poorly known, but because of their huge size are assumed to need large chunks of buried wood, for example the root systems of vast decaying tropical hardwood trees.Hence this insect is dependent on the continued existence of good quality forests with large trees.
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Life History and Behavior

Behavior

Behaviour

Most specimens of Titanus giganteus are collected using mercury vapour UV lights, which are exposed in the rain forest at night - a technique known as light trapping.Anyone who has left the bathroom window open and the light on during a warm summer’s night will know that the room can fill up with moths, flies and other insects - nocturnal insects are strongly attracted by artificial light, and Titanus is no exception.They fly at the height of the wet season between December and February and apparently appear at the light sheet rather late at night, usually after midnight. It is possible to collect several specimens in a single night’s light trapping in the right forest, during the right season.Like many species of insect, it is principally the males that are attracted by light, and there are no records of a female Titanus being collected in this way. Females are very rare in collections (although they are probably as frequent as males in the wild). All known female specimens have been collected by chance - walking along the forest floor, crossing the road, or drowned in a river.The females probably spend most of their time in decaying subterranean wood where they lay their eggs and where the larvae develop.Before the advent of electric light trapping, Titanus was considered extremely rare. Jaroslav Mares, a Czech entomologist, tells the story of an explorer in Manaus, Brazil, in the 1910s who was fortunate enough to recover a specimen from the stomach of a large fish which was being prepared for the table.He apparently enlisted the help of local people to comb the nearby Rio Negro for additional drowned specimens. By this method he accumulated half a dozen or so in various stages of decay. He proceeded to assemble a number of ‘complete’ specimens from them and these were offered for sale to dealers, collectors and museums, who were so keen to get the finest specimens of this great rarity, they met his steamer in the harbour.
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Physiology and Cell Biology

Physiology

Appearance

In his seminal Book of Sharks, Richard Ellis writes of the world’s largest fish, the whale shark Rhincodon typus, "there is a general (albeit erroneous) understanding that if a fish can be ‘40 feet long, why not 50, and if 50 feet, then why not 60’. "The same logic seems to apply to Titanus. The largest reliably measured, and published, specimen of Titanus giganteus is a male from French Guiana that was 16.7cm long. But the popular literature abounds with references to 18, 20 and even 22cm specimens. There is a widely circulated rumour that the Natural History Museum has a 20cm example of this species kept under lock and key. This is false, as, no doubt, are most of these outsize ‘records’.At present males of this species are believed to be larger than females, because all the largest known specimens are males. But females will probably prove to be larger than males - the sex ratio of known specimens means we are comparing the extremes from thousands of male specimens with the extremes from a few dozen female specimens.In similar species, such as the British and north European Prionus coriarius, where both sexes are quite well known, the females are on average a few percent larger than the males. There is no reason to believe the situation in Titanus is any different.
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Conservation

Conservation Status

Conservation

Like most inhabitants of the tropical rainforests, titan beetles are threatened by deforestation and habitat loss. Paradoxically, the interest of commercial collectors in specimens of Titanus may help to save not only the beetles themselves, but the whole ecosystem where they live.Anything that can be commercially marketed, even on a relatively small scale, but which lives only in good quality forest, will have the fringe benefit of saving tracts of forest that would otherwise be cleared away for more destructive forms of subsistence. One example is the brazil nut which is considered a ‘green’ product because the nuts only grow well in relatively diverse, undisturbed forest. Thus, the brazil nut industry provides an incentive to local people to keep areas of natural forest in good condition. This provides an income from the nuts, and at the same time protects everything else that inhabits the forest.There are villages in French Guiana, in the rainforests, where many people supplement their income by collecting insects in general, and Titanus in particular, for sale to dealers and collectors. This cottage industry ensures the continued survival of the forests in these areas, and all the species they support.Because female Titanus beetles are nearly impossible to collect, the commercial industry deals almost entirely in males. This makes the business truly sustainable, because the removal of males is less damaging to a population than removal of females (because one male can fertilise many females).So as well as being a truly magnificent creature, and the largest beetle in the world, Titanus giganteus could be described as a guardian of the rainforest.Since it is a large and showy insect, and many specimens end up in the commercial trade, there have been moves to extend legal protection to this species. But any such legislation is likely to have a negative impact and lead to further deforestation.
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Wikipedia

Titan beetle

The Titan beetle (Titanus giganteus) is a neotropical longhorn beetle, the only one in the genus Titanus, and the second-longest known beetle.

Description[edit]

Adults can grow up to 6.5 inches (16.7 cm) in length.[1] Of all known beetles, only the Hercules beetle, Dynastes hercules, in which giant males occasionally can grow to 7 inches (over 17.5 cm),[2] is longer than the Titan beetle, but the Hercules beetle males have an enormous horn on the pronotum or thorax making up around half of its total length. As such, the body of the Titan beetle is considerably larger than that of the Hercules beetles. It is known that the short, curved and sharp mandibles can snap pencils in half and cut into human flesh.[3] Adult titan beetles do not feed, searching instead for mates.

The larvae have never been found, but are thought to feed inside wood and may take several years to reach full size before they pupate. Boreholes thought to be created by titan beetle larvae seem to fit a grub over two inches wide and perhaps as much as one foot long. A famous "life-size" photograph of a putative larva of this beetle appeared in National Geographic magazine, filling an entire page,[3] but it was of a different species of beetle, possibly Macrodontia cervicornis.

The adults defend themselves by hissing in warning and biting, and have sharp spines as well as strong jaws.[3]

Distribution[edit]

It is known from the rain forests of Venezuela, Colombia, Ecuador, Peru, the Guianas, and north-central Brazil.

Gallery[edit]

References[edit]

  1. ^ [1] University of Florida Book of Insect Records
  2. ^ http://www.scientific-web.com/en/Biology/Animalia/Arthropoda/Insects/DynastesHercules01.html
  3. ^ a b c Zahl, P. A. (1959): Giant insects of the Amazon. Natl. Geogr. Mag. 115 (5): 632-669.
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