ChileanJAR

The emergence of the adults of N. xanthographus from the soil was evaluated with two types of traps, during the 1982/83, 1983/84 and 1984/85 seasons, in three fields of the V Region of Chile. Three peaks occurred: a first, at the end of spring; a second, at the begining of summer; and a third, that originated a lower population, late in summer (mid February, up to March). The oviposition of the adults of the first emergence begun 30 to 35 days after, occurring from November to December. The most important oviposition, from January to March, aroused from the second emergence. The developmental period of the larvae, in a glasshouse on weeds, was very heterogeneous, comprising approximately nine months. It fed principally on fine roots. Soil sampling carried out during three years, showed that larvae occurred during the whole year, while adults were not recovered during November. Soil temperature observations at a depht of 20 cm, suggested that adults emergence starts when the soil reaches approximately 15ºC, and stops when the temperature decreases below this value, in May. From this date onwards, the adults remained below the soil, during five to six months until September- October. Based on this, it is suggested that two parallel cicles occur: one with a span of 12 months, in which the adults emerge from December to April, and the other of 16 months, that originates adults that emerge in September-October.