Tick statistics are impressive. Some 907 tick species have been named. Their only food is blood, of which some ticks consume relatively vast quantities (several hundred times their unfed bodyweight). Some take 2weeks or more to feed. Often they only feed three times during the whole of their life cycle (which may take 7 years to complete). They feed on mammals (including humans), birds and reptiles. Their geographical distribution ranges from sub-arctic through equatorial to antarctic regions, and habitats range from desert to rainforest.蜱虫统计数据令人印象深刻。约907种蜱类已被命名。它们唯一的食物是血液，其中一些蜱类消耗相对大量的血液（是它们未进食体重的数百倍）。有些需要2周或更长时间才能进食。通常，它们在整个生命周期内只进食三次（可能需要7年才能完成）。它们以哺乳动物（包括人类）、鸟类和爬行动物为食。它们的地理分布范围从亚北极到赤道到南极，栖息地从沙漠到雨林。