|The first animals on this planet were invertebrates. They conquered all terrestrial and aquatic ecosystems and are capable of living in the most extreme environments on planet earth. In the heat of the Alentejo summer, the sound of cicadas reminds us that even the most arid landscapes have life. Compared to vertebrates, invertebrates are found in most ecosystems in greater numbers, diversity and biomass. They represent many phyla of the animal kingdom. Typically with a complex life cycle, most undergo transformations (metamorphosis) while changing from the larval stage to adult. Some species are truly nature’s architects. Examples of this are spider webs, mollusc shells, bee-hives and butterfly cocoons. Ecologically, they play very important roles such as in the nutrient cycles, because many of them are decomposers. They exist mostly in the base levels of the food chain, so a lot of trophic levels depend upon their existence. Insects are also responsible for ensuring the propagation of many plant species through pollination and seed dispersal. The main threat to this group is the use of toxic products in agriculture and, in modern times, global warming.