Larval densities, behaviour and life cycle of Sphodroxia maroccana (Coleoptera,Melolonthidae), an endemic pest of cork oak in the Mamora forest, Morocco

Abstract: The reproduction biology of Sphodroxia maroccana Ley was studied from adultscollected in 2009 in the Mamora forest (North of Rabat), and with adults issued from larvaereared in the laboratory. Pairs were bred separately in plastic boxes containing sand from theMamora and they were followed for their biology until death. In 50% of pairs, mating wasimmediate without any preliminary. In the other cases, mating occurred 24 to 48 hours after thepairs were formed. This delay was necessary until the two partners attained sexual maturity.Females oviposited quickly after mating, usually in the next three days. Oviposition occurred atthe surface of boxes in case of a thin layer of sand. When sand was enough, females oviposited atthe bottom of boxes. Fertility of females collected in the field varied from 60 to 120 eggs, 82eggs on average. Fertility was less for females obtained from larvae reared in the laboratory (10-70 eggs). Oviposition was sporadic, with breaks lasting up to 24 hours. Under laboratoryconditions, females were slowly moving round, allowing eggs dispersal. At a temperature of28°C, egg development lasted for 22 days on average. Adult longevity was short after sexualmaturity, 13 and 15 days on average for males and females, respectively. Development from eggto adult was 3 and 4-5 years on average for males and females, respectively, with three larvaeinstars and a marked sexual dimorphism. A study on the density of S. maroccana larvae duringtwo seasons (2008 and 2009) for all the Mamora districts showed that the density depended bothon the depth of the clay floor and on annual rains, and thus indirectly on the water holdingcapacity of sand. The highest densities (up to 3500 larvae / ha) were observed in the northerndistricts, where the soil depth was greatest, particularly during wet years.