Abstract

PARDO-LOCARNO, Luis Carlos  and  KOBAYASHI, Kazuho. Larval morphology, key to immature and life cycles of Megasoma actaeon L., M. elephas F., and M. janus ramirezorum S. & A. (Coleoptera: Melolonthidae: Dynastinae) in Colombia. Bol. Cient. Mus. Hist. Nat. Univ. Caldas [online]. 2022, vol.26, n.2, pp.275-310.  Epub Feb 07, 2023. ISSN 0123-3068.  https://doi.org/10.17151/bccm.2022.26.2.14.

The giant beetles of the Dynastini tribe (Coleoptera: Melolonthidae) gather three genera and 14 species in Colombia. Megasoma Kirby or elephant beetles, is represented by four species which, despite being charismatic and famous species, have remained little explored in their biology reason why this research aimed at describing the immature stages and carrying out the life cycles of Megasoma actaeon M. elephas and M. janus ramirezorum in Colombia. Within the framework of several institutional projects, parent species of the three were confined at different times (1998-2012 and 2017-2019), implementing breeding protocols in a bioassay laboratory (Palmira, Valle, 24o C, 980 m.a.s.l.). Data collection was carried out every fifteen days and included data on head width, chest width and body length. In the process some specimens were fixed for the study of larval characters, description, photography and elaboration of graphic arts. The life cycles of the three species were developed from egg to adult and the data of the times and growth measurements of the egg L1, L2, L3, prepupa, pupa and adult stages were compiled in tables. The results showed very long life cycles, of several years: Megasoma actaeon 3.2-3.3 years, M. elephas 2.4-2.6 years and M. janus ramirezorum 3.1-3.2 years. Third instar larvae (L3), male and female pupae were described and illustrated presenting the respective taxonomic keys. Regarding larval morphology, the redescription of M. actaeon disagreed (maxilla with 4-5 stridulatory teeth), M. elephas was more consistent (with minor differences in cephalic and dorsum chaetotaxy of abdominal segment I, perhaps for geographical reasons), while M. janus ramirezorum is described for the first time and was incorporated into the key in the group of large species with 4-5 stridulatory teeth in the maxilla, head width between 11-18 mm with the diameter of the abdominal spiracles progressively enlarged and bulla slightly convex, almost vertical. Finally, it is recommended to continue research on these species given their very long life cycles and the intense deforestation of their habitat.

Keywords : Biology; immatures; giant beetles; rainforests.

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