66 



Parasitic Arthropods 



49. Ixodes ricinus; male, ventral aspect. 

 Braun and Luehe. 



After 



work indicates that their long- 

 evity has been considerably 

 under-estimated. Typically, 

 they are permanent feeders, 

 remaining on the host, or hosts, 

 during the greater part of their 

 life. They molt twice only, 

 on leaving the larval and the 

 nymphal stages. The adult 

 female deposits a single, large 

 batch of eggs. Contrasting 

 the habits of the Ixodidae to 

 those of the Argasidae, Nuttall 

 (1911) emphasizes that the 

 Ixodidae are more highly 

 specialized parasites. "The 

 majority are parasitic on hosts 

 having no fixed habitat and 

 consequently all stages, as a 

 rule, occur upon the host." 

 As mere parasites of man, apart from their power to transmit 



disease, the Ixodidae are much less important than the Argasidae. 



Many are reported as occasionally attacking man and of these the 



following native spe- 

 cies may be mentioned. 

 Ixodes ricinus, the 



European castor bean 



tick (figs. 49, 50), is a 



species which has been 



often reported from 



this country but Banks 



(1908) has shown that, 



though it does occur, 



practically all of the 



records apply to Ixodes 



scapularis or Ixodes 



cookei. In Europe, 



Ixodes ricinus is very 



abundant and very 



commonly attacks 



50. Ixodes ricinus, var. seapularis, female. Capitulum and 

 scutum; ventral aspect of capitulum' coxae; tarsus 4; 

 spiracle; genital and anal grooves. After Nuttall and 

 Warburton. 



