Larval instars of Apion Clavipes gerst. (coleoptera: apionidae) Worku Mintesnot*, Azerefegne Ferdu1, Beyene Yibrah Amhara Regional Agricultural Research Institute Debre Birhan Agricultural Research Center, P O. Box. 112, Debre Birhan, Ethiopia 1Hawassa University, College of Agriculture, Department of Plant and Horticultural Sciences, P.O. Box. 05, Hawassa, Ethiopia *Email: mintie1976@gmail.com
Online published on 13 March, 2018. Abstract Morphological measurements such as head capsule width are being employed for classifying larval instars of insects. For successful IPM of larval stages of pests, assessment of the life history stage is very important. Apion clavipes Gerst. (Coleoptera: Apionidae) is an important pest of mungbean in the lowland areas of north Shewa, Ethiopia. Few studies have been made on specific parameters of its life history. The present study determines the number of larval instars of A.clavipes. Different growth stages of larvae were collected from mungbean fields on the commencement of pod formation to maturity during the main season of 2015 and preserved in 70% ethyl alcohol. Head capsule width of each larva was measured under a stereozoom microscope fitted with ocular micrometer. For analysis of data, the frequency distribution method and Dyar's Law were used. The frequency distribution showed three different peaks which represents the three layers of the head capsule width. These observations agreed with Dyar's Law that revealed a perfect geometric larval growth pattern for each instar by regression analysis. The excellent fit to a linear model, indicates that no instar was overlooked. Thus, this study brings out the morphometrics of the three larval instars for A.clavipes. Top Keywords Apion clavipes Gerst, mung bean, Ethiopia, Dyar's Law, larval instars, head capsule width, morphometrics. Top |