Lygus hesperus (Knight) and Lygus lineolaris (Palisot de Beauvois) (Hemiptera: Miridi) are two sympatric Lygus species commonly found in Texas High Plains. These species have wide range of intra- and inter-specific morphological variation.  Within species and between sexes morphometric plasticity often cause difficulty and confusion in species identification using qualitative taxonomic key. Thus the morphometric analysis of various characters can be helpful in better differentiation of species in Lygus complex. Accurate identification of the species is very important in Lygus research and management. Since the information on ontogenic morphology of these species is not available, the main objective of this study was to characterize these to species by its ontogenic morphometric parameters and compare these two species. We hypothesize that there is obvious difference in morphometric characters between these species in different stages of its ontogenic growth and development.
Lygus hesperus and Lygus lineolaris pure colony were received from WCRL, Arizona, and SIMRU, Missisippi, respectively and both species were reared in laboratory in debolt diet. Lygus eggs were collected using carrageenane gel pack. The growth and development of 40 fertilized eggs of each species were recorded daily for a month by taking digital photograph of each insect using the cannon G6 camera and Meiji stereo microscope. Insects were photographed daily to record the actual pattern of growth and development under laboratory conditions. The selected insect (egg, nymph and adult) images were digitized and the data were analyzed using various geometric morphometric tools.

This study suggests that the traditional morphometric (Euclidian distance) measurement of various body parts and its multivariate analysis is less efficient in differentiating sex and species of Lygus in various stages of its growth and development but the landmark base morphometry and the geometric model fitting, reconstruction and the transformation are promising tools to differentiate these species. The result from various geometric morphometric analyses of the ontogenic morphometric data will be compared and discussed in detail. The data generated in this project will be helpful in further morphometric phylogenetic study of Lygus species and also in the future development of digital taxonomic key and computer vision technology for Lygus identification.