The studies were conducted on the biological aspects of Cyclocephala tucumana Brethes, 1904 and C. melanocephala (Fabricius, 1775) in Aquidauana, MS, Brazil. From January to December 2009 a light trap was installed to make collections of adults of C. tucumana and from January 2010 to February 2011 for collections of adults of C. melanocephala, at the experimental farm of the Universidade Estadual de Mato Grosso do Sul. Adults were maintained in plastic containers with soil and complete plants of Brachiaria decumbens Stapf cv. Basilisk to oviposition and start biological studies. Adults of C. tucumana were collected from September to November in the field; the embryonic period lasted on average 14.7 days, and the first, second and third larval instars lasted 47.7, 66.1 and 78.6 days, respectively. Pre-pupa and pupa phases lasted 98.2 and 15.1 days, respectively, and longevity of the adults was 13.3 days. From the egg to adult stage of C. tucumana was a period of average 211.2 days. Adults of C. melanocephala were collected from September to October 2010 and February 2011. The embryonic period lasted 17.8 days, and larvae in the first, second and third instars lasted 22.3, 21.0 and 27.0 days, respectively. The pre-pupa stage lasted 11.3 days and pupa phase lasted 13.3 days. The longevity of adults was 26 days, and the cycle from egg to adult lasted 113 days.
life cycle; Cyclocephalini; Dynastinae; insects of the soil
