Insects form a highly diverse taxonomic group, which has fundamental ecological functions, but is currently in a process of mass extinction. Here, we present the first cycle of design, implementation, and assessment of a didactic sequence oriented towards improving pre-service teachers' knowledge and appreciation of insect diversity. A methodological approach aiming to promote rigorous observation was followed, for which activities consisting of scientific and naturalistic drawing, among others, were included. The sequence was contextualised at a university organic garden, both to make learning meaningful and to promote new personal experiences with alive insects. We present the empirical results of the first implementation with a group of 28 pre-school (3-6 years) pre-service teachers at a Spanish university. Assessment was based on the analysis of drawings with a purposely designed instrument to assess constructive accuracy, and on the qualitative analysis of open questions that were posed before and after the implementation. Positive results were obtained regarding participants' knowledge of insect diversity, and positive impacts were observed also on their attitudes. Improvements to some activities are suggested before subsequent implementations of the didactic sequence. Finally, our study supports the effectiveness of maintaining organically managed gardens as facilities for biological education.