Titanus giganteus

Problems in length measurements outlined by Williams (2001) could be adjusted in dried collection specimens by resofting and applying a standard measurement procedure. For the longest beetle, Williams (2001) cites a specimen Titanus giganteus having 167mm. Two other candidates for the longest beetles are Macrodontia cervicornis and Dynastes hercules.

The longest beetle I have seen so far was a male of M.cervicornis having 169mm, which is actually in the collection of J. Sticher (Germany). This specimen was not mounted in an unnaturally stretched position and was measured with a digital caliper between the most outer mandibular and elytral tip.

Macrodontia cervicornis

When we take thoracic horns into consideration in length measure- ments, Dynastes hercules may be as well a candidate for the longest beetle. Such species may reach a body length of 170mm, however, there is no confirmed record in literature.

Other noteworthy species with exaggerated morphologies is Batocera wallacei with impressive long antennae (max. length incl. antennae 315 mm, Raymond Chin, pers. comm.), Euchirus longimanus and Acrocinus longimanus with extraordinarily prolonged forelegs.

Fighting Dynastes hercules

Larger males have larger weapons in respect to their body length and win more often in direct encounters. A smaller male loosing in competition is not able to contribute genetic information to the populations gene pool, unless it develops a alternative reproductive tactic. Such „sneaking tactic“ may be the reason why we still encounter distinct small male caste in species with prolonged morphological structures. In Lucanidae, taxonomists distinguish between meso- (small), amphi- (medium) and telodont (large) male forms, in Dynastidae minor and mayor male forms.

Mayor and minor male of Goliathus goliatus

The general lack of large males with large weapons in some species indicate a lack of male competition. Among scarab beetles, the Rutelinae have bigger females, while in many flower-, rhino- and dung beetles big males with prolonged horns could be observed. In Buprestidae, females generally appear to be bigger than males. These groups seem to invest more biomass in reproductive output.

Batocera wallacei

Remark. The treatment of dried museum specimens is often unknown, bacterial degradation and impact by parasites may result in a considerable variability of the dry weight. To compare weight measurements, a standard procedure should be applied on fresh speci- mens. In many studies freeze-drying is considered a good method to determine dry weight. A established dry weight/length relationship of a statistically significant number of specimens takes allometric relationships into account and allows the extrapolation of the dry weight based on length measurements of museum specimens.