Threatened arthropods and described. The total number of living arthropod species is probably in the tens of millions. One conservative estimate puts the number of arthropod species in tropical forests alone at six to nine million species. As a consequence of all of the above, most published estimates of the total number of endangered insects and arachnids are probably low by at least an order of magnitude. Conservatively at least eighty percent of all living animal species are arthropods. Since arthropods constitute the majority of the faunal biomass on Earth, their role is vital to the survival of large numbers of insectivores
Parasitic flies of domestic animals transmitted organisms to develop, multiply and be exposed to further vertebrate hosts where they can complete their life cycle. Only the adult flies are involved in this biological transmission, in contrast to biological transmission by other arthropods such as lice or ticks in which all active stages of the life-cycle feed on blood. Typical genera are "Culex", "Aedes", and "Anopheles". The basic structure of dipteran flies is illustrated in the diagram. Veterinary parasitology also covers arthropods in the Class Acari, the ticks of domestic animals and mites of livestock which have distinctly different structure from arthropods in the Class Insecta.