certainty , but much can be deduced with relative accuracy from what is known . Titanus is confined to primary rainforest close to the equator in South America , principally northern Brazil , French Guiana and Surinam but also eastern Peru , Ecuador and Colombia . The beetles are only active nocturnally during the height of the wet season between December and March . The life cycle of Titanus is undocumented but there is no reason to expect that it varies in any major way from the rest of the prionid longicorns . This group have wood-boring larvae ( grubs ) that consume both living and dead trees and form large galleries in the wood . Female prionids seek out suitable host trees and lay their eggs in bark crevices with a long , flexible ovipositor that is extended from the tip of the abdomen . The vast majority of the Prioninae are large beetles (> 40mm ) and in many species the larval stage lasts for several years . The mature larvae of Titanus must be huge , approaching 30cm in length and weighing in excess of 100g , and to the best of my knowledge have never been found . The huge larva that featured prominently in Paul Zahl ’ s National Geographic article turned out not to be that of Titanus , but another giant South American prionid ; Macrodontia cervicornis . The complete absence of any clues as to the whereabouts of the giant Titanus larvae leads to only one logical conclusion - that they are underground in the decaying root systems of giant , dead rainforest trees . If Titanus was emerging from trees , logs or stumps above ground there would be tell-tale emergence holes left in the timber large enough to get four fingers into , and such obvious signs would be hard to miss . In support of the underground root system theory is the fact that a proportion of captured Titanus have patches of mud adhering to them , suggesting they have emerged through sodden wetseason soil . In addition , only very large roots could nourish such enormous larvae for a number of years , and this may explain why Titanus is common only in primary rainforest . The adult beetle lives for just a few weeks and does not feed ; clues from captured beetles indicate that their habits are similar to those of many other prionids . The mandibles of freshlyemerged male Titanus are tipped with a fine point , but very few males are captured with these intact . Many males are found with antennae , legs and most of the anterior portion of their mandibles sheared off , indicating that males engage in combat for breeding sites , mates or both . Larger males may therefore have an advantage in such combat bouts . From my observations of several species of prionids in Australia , combat and mating activities take place just after emergence when dozens of beetles can emerge from a single tree or log on the same evening . Males that are successful at driving off rivals copulate with females and then disperse in search of other host trees and potential mates . This may explain why Titanus only flies to lights very late in the evening , from about midnight to 3:00 am . Another intriguing aspect of the biology of Titanus is that females are not known to fly to lights and specimens are still considered a great rarity . It would be very unusual if the sex ratio was not close to 50:50 , so there are a lot of giant beetles out there that no one has yet found a way to sample . Huge , dead trees suitable for Titanus females to oviposit on are probably relatively common in a vast rainforest , but at the same time discrete and widely dispersed , so females are probably entirely focussed on locating suitable oviposition sites . It occurs to me that one way of cracking the Titanus life cycle may be to deliberately ring bark some forest giants and set up remote infrared cameras on the lower trunk and exposed roots in the hope of photographing or filming mating or ovipositing beetles .
As is typical of many
‘ Mature larvae must be huge , species of beetle whose larval stages live on approaching 30cm in length decaying wood , the eventual size an adult Titanus and weighing in excess of 100g .’ can attain is determined entirely by the amount of nutrition accessed as a larva . Adult male beetles display an amazing size range , from 79mm ' runts ' to a shade under 170mm at known maximum size . There are constant rumours that 180 and 200mm giants have been collected and secreted away , but no corroborative evidence has ever been forthcoming . There has been a great deal of debate about which insect is indeed the largest in the world , and Titanus is usually compared to other giant tropical beetles in the families Dynastinae ( rhinoceros and elephant beetles ) and Cetonidae ( flower chafers and goliath beetles ). The giant South American rhinoceros beetles in the genera Dynastes and Megasoma as well as the West African goliath beetles in the genus Goliathus are always put forward as contenders , but the lengths of all these giant scarab beetles are augmented by horns arising from the head or thorax or both . Titanus , on the other hand , is ' all beetle ' and has modest but very powerful mandibles that are in proportion to the rest of its body . Two other prionids vie with Titanus in total length ( Macrodontia cervicornis and Xixuthrus heros ), but both have long mandibles and more gracile proportions . Some of the giant scarabs may beat Titanus in weight , but again the comparison may not be valid . As recorded earlier , Titanus does not eat as an adult whereas the giant scarabs can live for months and eat a great deal . A single large male Dynastes hercules or Megasoma actaeon can consume an entire avocado in one day , so the only fair comparison to Titanus would be on an empty stomach . Reliable ' empty
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