Choice and No-Choice Bioassays to Study the Pupation Preference and Emergence Success of Ectropis grisescens

Many insects live above the ground as larvae and adults and as pupate below the ground. Compared to the above-ground stages of their life cycles, less attention has been paid on how environmental factors affect these insects when they pupate within the soil. The tea looper, Ectropis grisescens Warren (Lepidoptera: Geometridae), is a severe pest of tea plants and has caused huge economic losses in South China. The protocols described here aim to investigate, through multiple-choice bioassays, whether mature last-instar E. grisescens larvae can discriminate soil variables such as the substrate type and moisture content, and determine, through no-choice bioassays, the impact of the substrate type and moisture content on pupation behaviors and the emergence success of E. grisescens. The results would enhance the understanding of the pupation ecology of E. grisescens and may bring insights into soil-management tactics for suppressing E. grisescens populations. In addition, these bioassays can be modified to study the influences of various factors on the pupation behaviors and survivorship of soil-pupating pests.