144 Veterinary Medicine. 



furrows respectively in front of and behind the anus, and a me- 

 dian groove from the anus to the post-anal furrow. 



Ornithodorus Megnini. The Spinose Ear Tick. Body 

 lyre-shaped, nearly twice as long as broad, rounded at both ends, 

 slightly constricted just behind its middle, and broader in front of 

 this. Color, brown to violet or black. On dorsum two grooves 

 starting from behind the head, arch backward near the lateral 

 margin often showing interruptions, and a median groove ex- 

 tends over nearly all the posterior narrowed part of the body. 

 On the ventral surface there is no pre-anal groove, but the 

 post-anal groove turns forward on the two sides to join the 

 grooves along the inner borders of the coxse. This coxal groove 

 passes between coxae one and two. Sigmata large, circular with 

 a semilunar pore. Anus near posterior border bearing fine hairs 

 on its lips. Head (capitulum) very short and narrow (150 ju. 

 long) ; mandibles .slender, internal apophysis bearing four teeth, 

 external apophysis with three teeth. Dart (hypostome) blade- 

 .shaped, unarmed. Palpi longer than other head organs with 

 many pennate hairs on base near palpal insertion. Legs moderate 

 in size prominent tuberosity on dorsal surface of each tarsus. 

 Eyes wanting. Females 5 to 6 mm. long, by 3 to 4 mm. broad ; 

 males somewhat less. 



In nymph and larva the hypostome (dart) is armed with teeth 

 which Megnin also figures in the adult though Stiles and Neu- 

 mann failed to find them. In these young forms the skin is firmly 

 striated and pierced with symmetrically arranged pores from 

 which project spines in the anterior part of the body and bristle- 

 like hairs in the posterior. Stiles describes a pupa-like resting 

 stage between the hexapod larva and octopod nymph. The 

 nymph is better armed and may grow as large as the adult. 



Distribution. Duges first described this argas in Mexico, and 

 it is common in adjacent states (California, New Mexico, Ne- 

 braska, Kansas, Texas). 



Hosts. It is particularly common on the ears of horse, ass, 

 mule, cattle, and other animals, and even attacks the human 

 being. It is not confined to the concha but invades the auditory 

 meatus as well, and gives rise to much irritation, shaking and 

 rubbing of the head, and even to nervous and other disorders and 

 it is alleged death. 



