Arthropods may cause direct or indirect injuries, damages and/or infections of a variety. Mostly, 
however, they are important medically because of their mediation as a vector for a large number 
of diseases transmitted to human and animals. They are medical importance as biological vectors 
of pathogens (malaria and Leishmania parasites, viral hemorrhagic fevers, Lyme disease…etc.), 
passive carriers of pathogens (bites or feces), ectoparasites (ticks, fleas, blood-sucking, flies, 
lice…etc.), nuisance pests (bed-bugs, millipedes). But, not all the insects are harmful, others are 
essential to life on Earth. Bees and butterflies help plants produce seeds, ladybugs eat devastat
ing pests and have even saved citrus crops, and centipedes control indoor bug population.