Insects (Class: Insecta) are arthropods (Phylum: Arthropoda) that have specialized and segmented body extremities (“Insect” means cut in half). They have sclerotized cuticles (exoskeletons) but do not develop a real shell. They have a pair of antennae, three pairs of legs and two pairs of wings. Most are small (from 0.5 to 3 cm in length). The largest examples belong to the group of beetles and bugs.
The insect group is not only diverse, but also incredibly abundant: it is estimated that for every human being on Earth, there are 200 million insects. These may be herbivores, carnivores, scavengers, or even those which practice parasitism and commensalism (Brusca and Brusca, 2002).
Insects play an important role in the functions of the environment. They are the major predators of other invertebrates and are therefore also pest controllers. They break down and eliminate a significant percentage of organic matter and are the principal pollinators of ecologically and economically important plants. However, and as a result of their great abundance, they have occasionally been regarded as a harmful group, since they consume nearly a third of the world’s crops and are the main vectors of human diseases (Brusca and Brusca, 2002).
Insects are the most diverse group on the planet. To date, the number of insect species described worldwide is unknown, but estimates range from 890,000 to more than one million species. The catalogs (CAT) currently include seven groups of insects including the most diverse such as beetles (Order: Coleoptera) and the butterflies and moths (Order: Lepidoptera).