none Entered purchase/In this article, the ontogeny and reproductive biology of Diadegma semiclausum (Hym.: Ichneumonidae), an important parasitoid of Plutella xylostella (Lep.: Plutellidae) are described in detail. We did dissect parasitized P. xylostella larvae in phosphate-buffered saline and determine the external morphology of its parasitoid at all developmental stages. The developmental duration of its immature stages, adult longevity, total oviposition period and fecundity of the parasitoid are determined at 24 1 C, 65 5% R.H., and a photoperiod of 16:8 h L: D. The mean duration of egg and larval stages is 9.56 days and the prepupa and pupa stages last for 8.27 days. In average, female longevity is 131 times longer than that of males, and females lay 300 eggs in total. The peak of D. semiclausum oviposition is on the eighth day after mating. The egg loading pattern of D. semidausum was investigated to determine the parasitoid 'ovigeny index' throughout the female's parasitoid lifetime. Initial egg load in immature females (<2 h age) is 1.45 per female and the mean lifetime potential fecundity (total immature and mature oocytes), at four interval ages, is 34. With an ovigeny index value of 0.038, D. semiclausum is considered moderately to strongly synovigenic. In the absence of the host, after 3 days, the number of eggs is decreased in D. semiclausum. Our results demonstrated that there is a negative relation between the ovigeny index and egg resorption in this parasitoid. (C) 2014 Elsevier Ltd. All rights reserved. Jan 2015