Many parasites which actively invade or attack their hosts perform an ambushing strategy of host finding, i.e., they await their hosts in their selected microhabitats (e.g., many species of trematode cercariae, infective nematode larvae, and ticks). However, other parasites actively approach towards their hosts employing very different types of orientation. Aquatic invasive larvae such as some trematode miracidia and cercariae may reach their hosts by chemo-orientation along gradients of certain host-emitted compounds. In most species, the type of orientation is a chemokinesis (random, undirected changes of the path of swimming in response to an increase or decrease of the stimulus concentration); but chemotaxis (directed movements along the concentration gradient of the stimulus) has also been described ( Host Finding, Miracidium, Trematodes, Cercariae). Terrestrial host-searching parasites such as certain nematode larvae and ticks may orientate along thermal gradients, odorous and visual signals of their hosts ( Host Finding, Nematodes, Ticks), and bloodsucking arthropods such as Mosquitoes and Tsetse Flies may get to their hosts by an oriented flight toward visual cues or by an upwind anemotaxis in response to odors, moisture and heat ( Host Finding, Mosquitoes, Tsetse Flies). After attachment to the host many parasites such as schistosome cercariae, hookworm larvae, and ticks orientate themselves toward particular sites for penetration or feeding, responding to temperature, mechanical and chemical host cues (for details, Host Finding).