66 
Parasitic Arthropods 
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) lias 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. scapularis, female. Capitulum and 
scutum; ventral aspect of capitulum- coxse; tarsus 4; 
spiracle; genital and anal grooves. After Nuttall and 
Warburton. 
