Megasoma occidentalis, Bolivar, Pieltain, Jimenez-Asua & Martinez, 1963

Ratcliffe, Brett C. & Morón, Miguel-Angel, 2005, Larval Descriptions Of Eight Species Of Megasoma Kirby (Coleoptera: Scarabaeidae: Dynastinae) With A Key For Identification And Notes On Biology, The Coleopterists Bulletin 59 (1), pp. 91-126 : 92

occidentalis Bolívar y Pieltain, Jiménez-Asúa, and Martínez was recently elevated to

species status by Morón and Gòmez-Anaya (2002).

Adults of Megasoma are recognized by their moderate to large size, broadly truncate to emarginate clypeal apex with acute or toothed anterior angles, mandibles with two or three acute teeth, short prosternal process, and tridentate anterior tibia. Males all have a variably developed, bifurcate head horn, and the pronotum is either armed or not. Hardy (1972) reviewed the North and Central American species, Endrödi (1977, 1985) provided a synopsis of all the species, and Lachaume (1985) illustrated (life-size) all the species as part of the Sciences Nat Beetles of the World series.

The immature stages, biology, and life cycle of the species of Megasoma species are poorly known. Some comments and photographs about collecting larvae of M. actaeon (L.) inside the standing trunk of the ‘‘matamata´’’ tree, Lecythis chartacea Berg , ( Myrtaceae ), in the Brazilian Amazon were published by Zahl (1959). Gibson (1964) published some data on the habits and larval development of M. pachecoi Cartwright that were reared from eggs laid by captive females that were collected on the branches of ‘‘palo brea,’’ Cercidium torreyanum (Wats.) Sarg. (Caesalpinaceae) . Möhres-Reitter (1966) provided a short note and picture of the larva of M. gyas (Herbst) in Brazil, and he indicated Cordia gerascanthus L. ( Boraginaceae ; ‘‘palo de rosa’’) was the rotting tree in which the larvae were found. William Warner (pers. comm., to BCR) indicated that adult females of M. sleeperi Hardy occasionally come to lights (males rarely so), and that males can be found on the trunks of blue palo verde, Cercidium floridum Benth. (Caesalpinaceae) , at night or on small branches feeding from dawn to ca. 0900 h. Adults have also been observed emerging from the sand beneath palo verde trees at dusk. Morón (1977) provided a description of the third-stage larva of M. occidentalis that was found in the rotten stem of a coconut palm, Cocos nucifera L. ( Arecaceae ). Life cycle notes and illustrations of immature stages of M. elephas (F.) reared in captivity were provided by Morón (1984), Morón et al. (1997), and Morón and Deloya (2001).

Fourteen species of Megasoma are distributed from the southwestern United States to northern Argentina ( Endrödi 1985). One of us (BCR) was able to obtain over the last five years the larvae of six species of Megasoma from the southwestern United States, northwestern Mexico, and South America that provided the foundation for this work. MAM obtained the larvae of two additional species. In this paper we describe for the first time the third-instar larvae of M. pachecoi Cartwright , M. punctulatus Hardy , M. thersites LeConte. , M. vogti Cartwright , M. cedrosa Hardy , M. actaeon (L.), and M. elephas (F.), as well as a redescription of the third-instar larva of M. occidentalis Bolívar y Pieltain, Jiménez-Asúa and Martínez. We also have notes on the first and second instars of M. elephas and describe the pupa. Megasoma species for which the immature stages have not been discovered and/or described are M. gyas (Herbst) , M. mars (Reiche) , M. anubis (Chevrolat) , M. joergenseni (Bruch) (all South American), M. sleeperi Hardy (SW United States), and M. lecontei Hardy (Baja California Sur, Mexico).

Terms and characters used in the descriptions are those of Ritcher (1966), Ratcliffe and Chalumeau (1980), Morón (1977, 1987, 1993, 1995), and Morón and Ratcliffe (1990). Drawings were made using a stereomicroscope and camera lucida. Measurements were obtained with an ocular micrometer or caliper. Study specimens were deposited at the University of Nebraska State Museum, Lincoln, Nebraska (UNSM) and the Instituto de Ecología, Xalapa, Veracruz, Mexico (IEXA).