Vol. 3, Issue 11, Part G (2017)

Present work is the laboratory study report supported with field observations made to understand the life cycle and development of Pachnoda interrupta (Oliver), along with its interaction on impact of physical factors and soil types on its development. Soil samples collected from Afar, Tikur-Inchini and sandy soil from Guder River near Ambo were used separately and mixed with different proportion of cow-dung. Eight types of food substances were tested for their effect as bait in the infested area. In the life cycle study (at 25 ˚C & Moisture 17%) the average oviposition rate was found to be 0.58 eggs/ day/ female. Whitish soft shelled eggs were laid separately in soil varying (strata) from 3-18 cm. in depth. The mean number of days for egg hatching was 9.63±1.4 ranging between 8 and 13. Larval development took an average of 59.09± 1.94 days ranging between 42-73. Body length was constantly increasing up to around 52 days where it reached 30.2 mm and was shrinking to its last days and measured 28mm at about the 70^th days. Larval head capsule width however showed discontinuous but constant increase and at an average 3.14+0.01mm was measured in final days (62-70). Papal development ranged from 18-30 days with an average of 24.47 ±3.5 days. When soil moisture is less the larvae went down deep in to the soil to pupate and when it is high, they remained in the upper layers. Soil temperature however did not show significant effect on pupation depth. The adults required an average of 93.79± 1.8 days, ranging from 68-116 to emerge.

The laboratory study and the field observation confirmed that P. interrupta are univoltine insects having two phases in their life cycle (emerging seasons). The presence of cow-dung in the soil was found necessary for the completion of life cycle in P. interrupta.