Larval growth rates and sexual differences of resource allocation in the cetoniine scarabMecynorhina polyphemusFabricius 1781 (Coleoptera: Scarabaeidae: Goliathini)

Abstract

Larval ontogeny of the scarab Mecynorhina polyphemus was monitored throughout all instars, and larvae were weighed at 7-day intervals. Durations of the prepupal, pupal and postpupal stages were recorded. Larvae increase their body masses over 300 times during ontogeny. Male imagines are larger than females, and this is primarily a function of faster growth rates during instar III, resulting in significantly heavier larvae at the end of this instar. The durations of the three instars are not significantly different in males and females, but the duration of the prepupal and postpupal phases is significantly longer in males. There is a strong correlation in both sexes between maximal larval mass and the mass of the imago, but larval mass-imago mass scales with significantly different slopes in males and females. Male larvae must allocate increasingly more resources into production of cephalic horns with increments in larval mass, requiring differently proportioned pupal chambers.

Catch‐up growth in the rhinoceros beetle Trypoxylus dichotomus (Coleoptera: Scarabaeidae): Smaller neonates gain relatively more body mass during larval development

“…In contrast, many species in different subfamilies of Scarabaeidae (Coleoptera) show malebiased SSD with three larval instars irrespective of sex. This trend suggested by Tammaru et al (2010) was also supported among a few species of Scarabaeidae showing male-biased SSD (Christiansen 2013;Vendl et al 2016Vendl et al , 2018. In the present study, the sexual difference in the mean size continuously increased throughout larval development in T. dichotomus, a scarabaeid species with a relatively high SDI magnitude among insects.…”

“…This trend suggested by Tammaru et al . () was also supported among a few species of Scarabaeidae showing male‐biased SSD (Christiansen ; Vendl et al . , ).…”

“…obs. by the author, 2012-2013; however, its developmental mechanism has not been examined closely. In general, the development of sexual difference in body size has been evaluated in terms of sexual difference in the mean body size.…”

Immature stages of giants: morphology and growth characteristics of Goliathus Lamarck, 1801 larvae indicate a predatory way of life (Coleoptera, Scarabaeidae, Cetoniinae)

“…It is also known that other rose chafer larvae (e.g., Eudicella , Cheirolasia , etc.) enhance their diet by feeding on rose chafer larvae of other species or are even cannibalistic (Klátil and Vrána 2008, Micó et al 2008, personal observation), but this behaviour is only facultative and the larvae are able to finish their development normally without protein input (Christiansen 2013, personal observation). The possible dependence on live prey may also be reflected in their larval morphology.…”

“…Some breeders even report Goliathus larvae to be predaceous (McMonigle 2001, 2006, 2012, Meier 2003, Meier and Campbell (undated)). This is in contrast to most other rose chafers, whose larvae are able to develop successfully on a substrate composed only of decaying plant matter; this is also true for some genera with very large beetles (e.g., Mecynorhina Hope, 1837, Mecynorhinella Marais & Holm, 1992) (Micó et al 2008, Christiansen 2013). However, no experimental study has been carried out to confirm or disprove the assumptions made in these breeding manuals.…”