74 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL, 1 10 



SO that the cutting action of their teeth is in a lateral direction. The 

 shafts are protractile and retractile within the sheaths. On their 

 bases are inserted the usual cheliceral muscles, which here serve as 

 retractors ; protraction is said to be produced by a bulblike compression 

 of the body effected by the dorsoventral somatic muscles. 



The exact method by which a tick "bites" perhaps needs more study 

 than has been given to it. Sharif (1928) observes that the palps of a 

 feeding tick are pressed against the skin of the host, and that the 

 initial incision must be the work of the chelicerae, which cut the skin 

 to admit the blunt tip of the hypostome and enable the latter to be 

 pushed into the wound. According to Cooley and Kohls (1944) the 

 hypostome in the argasid genus Antricola has only very small teeth, 

 while the chelicerae are large and effective cutting organs. The mouth 

 parts of these ticks, therefore, are "adapted for quick feeding and 

 not for clinging to the host." In preserved specimens of Dermacentor, 

 Amblyomma, and Boophiliis that have been detached with a piece of 

 the host's skin, the rostrum of the tick is ensheathed to its base in a 

 conical or sleevelike papilla extended from the flat surface of the 

 integument, and the sides of the papilla are clasped by the concave 

 mesal surfaces of the palps. Figure 26 C shows a papilla from which 

 the rostrum of the tick below has been removed, and at D the line hs 

 indicates the position of the papilla ensheathing the rostrum. If the 

 papilla results from the forcible detachment of the tick, the teeth 

 of the hypostome should be holding at its distal end ; on the contrary, 

 the hypostome in all cases is completely enclosed with its toothed 

 extremity at the bottom of the tube. In these specimens, therefore, 

 it would appear that the skin of the host has grown out around the 

 rostrum of the tick. Portman and Dalke (1945) report finding 

 numerous larvae, nymphs, and adults of Amblyomma americanum 

 buried in the skin of a fox, presumably as a result of local swellings 

 of the host tissue that had engulfed the parasites. 



The ticks are said to have a keen sense of odor perception. In the 

 Ixodidae the organs of smell, known as Haller's organs, are groups 

 of innervated hairs in cavities on the tarsi of the first pair of legs. 

 When these legs are amputated, according to Totze (1933), the tick 

 gives no reaction to odor, but will feed through a moist, warm, arti- 

 ficial membrane on blood or most any kind of liquid, such as chemical 

 solutions, even strong-tasting substances, showing that it has no 

 gustatory sense. Presumably, then, the ticks recognize an animal as 

 its proper source of food by a sense of smell, and the combination of 

 warmth and moisture from the skin gives the stimulus for feeding. 



