The development of sampling techniques for populations of the tarnished plant bug,Lygus lineolaris (hemiptera: Miridae)

Summary The relationship of ‘mean crowding’ to mean density showed that counts of nymphs and adults of the tarnished plant bug,Lygus lineolaris (Beauv.), on birdsfoot trefoil were aggregated and that the index of basic contagion approached zero for each developing stage. Aggregation increased gradually from the first to the fourth instar and then decreased through the adult stage. The mortality process from the first to the fifth instar was inversely density dependent. Inter-sample variance was the major source of population variance although significant variance was occasionally associated with blocks and plots owing to heterogeneity of the host stand. The most appropriate sample unit was a 3 sq. ft. area of foliage and substrate. This was divided into four quarters; application of the variance component technique indicated that in most cases one quarter drawn at random was optimal for sampling different stages. The number of samples required to attain a given level of precision varied inversely with population density. The cost function for sampling was determined for specified levels of precision.