BIOLOGICAL ASPECTS OF CHISAS IN LA SABANA DE BOGOTA

Abstract

The objectives of this study were to identify the most common species of white grubs in the Sabana de Bogotá, to establish a rearing medium, to determine the life cycle and to build the fertility table. These experiments were cdrried out under insectary conditions, at ICA's Experimental Station "Tibaitatá" in Mosquera (Cund.). The species of Scarabaeidae collected in the light trap were Ancognatha scarabaeoides Burmeister, A. ustulata Burmeis­ter, Heterogomphus dilaticollis Burmeister (Dynastinae) and Clavipalpus sp. possible ursinus Blanchard (Melolonthi­nae), being the first the most abundant; however under field conditions, the most numerous seems to be C. pos. ursinus. After trying several rearing media, it was concluded that the only one in which larvae of A. scarabaeoides developed sat­isfactorily was a mixture of soil+ ground rotten wood+ dry cow dung. The duration of the life cycle from egg to adult emergence was 342.75 days for females and 348.62 for males. The longest was the larval stage with 244.93 days, and the third larval instar had an average duration of 162.72 days. According to the fertility table the fecundity rate obtained was 3.84 and the net reproductive rate (Ro) 16.58. The intrinsic rate of natural increase (r_m) was 0.12 and the finite rate of increase ( ) was 1.124.