186 MITES AND TICKS 



The Notostigmata are secretive and live under stones and other 

 debris. Chitinous remains of arthropods have been found in their 

 guts and it is probable that they are predatory, but so few speci- 

 mens have been collected that little is yet known of their biology. 

 The habits and life histories of the Holothyroidea too are virtually 

 unknown. Many of the Mesostigmata live on plants and prey on 

 small insects and other mites. A great many of the genera of 

 Gamasides and Uropodina are found in damp places, in manure 

 heaps and amongst moss and damp leaves, the Gamasides preying 

 on smaller creatures. The Uropodina, which are slow moving and 

 sluggish, feed on fungi and vegetable matter. The members of the 

 Parasitidae, for example, are found typically in accumulations of 

 organic material such as rotting logs and litter. Other families 

 however, such as the Laelaptidae, are usually parasitic on verte- 

 brates and to a lesser extent on invertebrates. Indeed, this family 

 includes the most common ectoparasites of mammals, while the 

 Halarachnidae live in the air passages of mammals, one genus 

 occurring exclusively in the respiratory passages of seals of the 

 family Phocidae, another parasitising the other Pinnipedia. 



Ticks are comparatively large, leathery animals which are all 

 parasitic on vertebrates. Even the larval forms or 'seed ticks' are 

 visible to the naked eye and a fully gorged female may attain a 

 length of half an inch. The Ixodidae are of great economic and medi- 

 cal importance. Heavy infestation by these creatures can cause 

 anaemia in domestic animals, and they carry several noxious dis- 

 eases to man and other vertebrates. Thus Rocky Mountain spotted 

 fever and Texas fever of cattle in America are transmitted by 

 Dermacentor andersoni and Boophilus annulatus respectively, while 

 man is infected with Rocky Mountain fever, Kenya typhus, Q 

 fever and Tularemia by the bites of various ticks. Tick paralysis of 

 man and animals is believed to be due to toxins secreted in the 

 saliva of the ticks. Though more frequently observed in tick- 

 infested animals, a number of human cases have been reported in 

 the United States, Canada and Australia. The ascending paralysis 

 is caused by a rapidly engorging female tick attached to the base of 

 the head where the hair may hide its presence for a long period. 

 Complete recovery follows within a day or two of removal of the 

 offending parasite, but death may occur if the paralysis has reached 



