TICKS, the common name for Arachnida belonging to the order Acari, of which they constitute the two families, Ixodidae and Argasidae.
As compared with the majority of Acari, ticks are of large size, distended female specimens of some of the species measuring half an inch or more in length, while even the newly hatched young can hardly be regarded as microscopical.
It is by means of the hypostome that ticks pierce the integument and firmly adhere to the host whose blood they suck for food.
For a longer or shorter period of their lives ticks are parasitic upon vertebrate animals of various kinds; but although the belief that the bite of certain tropical species is poisonous has long been held by the natives of the countries they infest and has been recorded with corroborative evidence by European authors in books of travel, it is only of recent years that accurate information has been acquired of the part played by these Arachnids in transmitting from one host to another protozoal blood-parasites which cause serious or fatal diseases to man and other animals.
It is singular that the Argasidae, which are for the most part parasitic upon birds, contain the only species of ticks, especially 0.