Teaching ecological concepts and field methods for introductory biology courses can be challenging, especially when class sizes are large and activities or topics depend on environmental conditions that can change dramatically from semester to semester. We provide a laboratory module that can be used throughout the year, where students can explore plant-insect interactions on campus trees in urban environments using nondestructive measures. Students are provided a transparent grid, a measuring tape, and a random selection protocol to estimate gloomy scale (Melanaspis tenebricosa) insect density on preselected Acer rubrum tree trunks. Students are also given a pace-to-plant protocol to evaluate how impervious surfaces around trees in urban environments may be associated with scale insect abundance. This module highlights ecological concepts, such as population dynamics, species interactions, competition, and food webs, among others. Through this module, students also learn skills in ecological field sampling techniques, particularly how to randomly sample, how to estimate insect abundance, and how to use observation skills to inform scientific inquiry.