MITES. 



101 



By this metamorphosis the forms are enabled to withstand desiccation, while a slight 



exposure to dryness kills the normal forms. The species of Typhlodromus usually 



occur on plants, where they eat the epidermis of the leaves. 



The IxoDiu^E, or family of ticks, embraces the largest individuals of the Acarina. 



The body is enclosed in a leathery skin, the palpi are four-jointed, enclosing the 



denticulated beak, which is formed of 



the cheliceraj and labrum. Eyes are 



sometimes lacking, and the legs are 



slender, terminating with two claws. 



Ixodes is the typical and largest genus, 



embracing the forms commonly known 



as ticks. These live in the woods, and 



attach themselves to cattle, dogs, and 



man whenever they have a chance. 



Here they suck the blood until the body 



swells up so that it resembles a pea. 



Several American species have been 



described,- mostly by Dr. Packard, the 



AVhite-sjiotted Tick, Ixodes alhipictus., 



being possibly the best known. The 



European Ixodes ricinus attaches its 



eggs to its body by a clear fluid which 



flows from the mouth, and this, to- 

 gether with the position of the open- 

 ing of the oviduct, which is very far 



forward, gave rise to the idea that the 



female laid its eggs through the mouth. 



The genus Arffas, which is blind, contains two well-known species, the A. reflexus 



of Europe, which is parasitic on birds, especially on doves, and A. persicus, of Persia 



and adjacent countries, which 

 lives in houses, and by its 

 punctures j)roduces convul- 

 sions in man, and it is said 

 that even death has resulted 

 from its sting. Another less 

 known form, Arffas niffua, 

 the Pique, jiroJuces distress- 

 ing, and sometimes even dan- 

 gerous, sores on men and 

 cattle. 



But little is known of 

 the American species of the 

 next family, the Oeibatid.e, 

 though the European species 



have been more extensively studied. These forms have the body hard and hornj^, 



the ocelli almost obsolete, the mandibles chelate, and the palpi four-jointed and 



short. The legs are fitted for walking, and terminate in from one to three claws. 



The sides of the cephalothorax are frequently expanded, and bear on their edges two 



FIG. 136. 



— Ixodes ricinus, female, a, 

 Stigma, h. Genital opening. 



, d, e. Mouth-parts. 

 Anal valves. 



Fig. 137, — Upper and under surface of Argas rejlexus, dove-tick, enlarged. 



