Blood-feeding is relatively uncommon among arthropods and is seen only in 14000 species (Graca-Souza, 2006) from the orders Diptera (mosquitoes, flies), Siphonaptera (fleas), Phthiraptera (Sucking lice), Heteroptera (true bugs) and Acari (ticks, mites).
Hematophagy among arthropods can take two basic forms: obligatory and optional. Optional hematophagous have different sources of food and use blood either as a complementary source of nutrients or for a key physiological purpose. In some cases feeding on blood depends on the age and the sex of an individual.
For instance, only adult female mosquitoes feed on blood, besides feeding also on nectar. The males feed exclusively on nectar, and the larvae are aquatic filter feeders (Jason Pike, 2009). However, obligate blood-feeders do not have any other source of food besides blood. They rely exclusively on blood as a source of nutrients. The kissing bug is a good example, in which all the sexes, and the immatures as well as adults feed on blood (Edman and Edridge, p.25).