The work included study of external morphology of white cabbage butterfly Pieris rapae (Linnaeus, 1758). The study included the external morphological characters of different body regions in addition to the male and female genitalia. The studied morphological characters were supported by photos and illustrations. Specimens of the work were collected from north and middle of Iraq and dates and sites of collection were fixed.
In this paper, estimation of system reliability of the multi-components in stress-strength model R(s,k) is considered, when the stress and strength are independent random variables and follows the Exponentiated Weibull Distribution (EWD) with known first shape parameter θ and, the second shape parameter α is unknown using different estimation methods. Comparisons among the proposed estimators through Monte Carlo simulation technique were made depend on mean squared error (MSE) criteria