228 



FLEAS, FLUKES AND CUCKOOS 



an eight-legged nymph. At this stage the subsequent moult produces 

 the hypopus. This form is devoid of mouth parts and cannot feed. The 

 legs are reduced and several adhesive discs or suckers are developed on 

 the ventral surface. It is solely adapted to phoresy or passive dispersal 

 by some arthropod carrier. It is these hypopus nymphs which are 

 found hitch-hiking on fleas (see p. 103), flies, ticks and even on the wings 

 of moths. They are never parasitic at this stage and use the adult insect 

 merely as a means of transport. Nevertheless in large numbers they can 

 cause the death of the transport host. 



In the adult form the bodies and secretions of mites are toxic, at any 

 rate to man, and possibly to other animals. So-called grocer's itch and 

 miller's itch are really forms of acute dermatitis (sometimes accom- 

 panied by fever, asthma, vomiting and other symptoms) produced by 

 contact with flour and grain heavily infested with mites. 



Itch mite, Cnemidocoptes mutans, occurring on various birds 



(x 176) 



