This work is a study of previous conceptions of young students and adults about the content relating to zoology, in particular insects. We emphasize that the knowledge built by these students should be respected and considered as an important variable in the process of teaching and learning of scientific and technological knowledge. To explain the students’ prior knowledge on the subject in question, we developed a questionnaire consisting of three themes relating to animals: the general concept, the characterization of invertebrates and the relationships established between insects and man. The data analysis allows us to state that although the vast majority of students evidencing the role that insects play in the ecological balance, still use common sense criteria to characterize them at the expense of biological criteria. Our studies show that the initial representations made by students about the concept of animal and, particularly, insects showed once again the need to propose teaching activities that facilitate the conceptual change from the confrontation of ideas and these students with scientific knowledge.