Tribolium castanaeum is a widespread insect in temperate regions. Because of its short generation time and easy handling, it serves as a model organism for various scientific questions. However, T. castanaeum, or its larger-sized relative Tenebrio molitor, can also be used at a school or college level to foster students' experimentation skills. We present a set of inquiry tasks that build stepwise on one another, using T. castanaeum or T. molitor as the model. The students will learn not only about insect ecology, but also about the influence of nutrition on several fitness parameters, such as development time and offspring number.