Cooley & Kohls: Argasidae of N. America, etc. 27 



long by about 2 mm. broad, rounded, white pyriform structures with one end elongate. . . 



We have not seen this stage alive, but from the general structure it is apparent that 

 in changing from the hexapod to the octopod stage O. megnini passes a resting pupa-like 

 stage. This is by no means surprising, since the differences between the hexapod and the 

 octopod stages of the Argasidae are far greater than those between the corresponding 

 stages of the Ixodidae. This is apparently the stage which Townsend (1893) interpreted 

 as an egg. 



Brumpt (1936), p. 647, gives the following: 



From the cat (693 XV) I collected two types of nymphs (1st and 2d. n.). The 

 engorged nymphs in the last stage dropped on the 38th day. 



The last molt, which produces the adults, is effected in the exterior environment. 

 From the hexapod larva to the adult according to me there certainly are three molts and 

 not two as claimed by others. 



In February, 1940, many larvae of megnini from females, Douglas, Ari- 

 zona, 16128, were placed in the ears of rabbits and soon engorged. Some of 

 the engorged larvae were removed and held for molting while others were left 

 attached. Fourteen days after the rabbit was infested with larvae, a comparison 

 was made of the nymphs resulting from the engorged larvae removed from the 

 host and the nymphs that were now present on the rabbit. The two nymphs 

 were found to be distinctly different, showing that the nymphs on the host had 

 undergone a molt; thus our findings are in conformity with those of Dr. 

 Brumpt. The hypostome of the first nymph measured 0.195, the coxae were 

 smaller, and the legs not as heavy. The hypostome of the second nymph meas- 

 ured 0.33, the coxae were larger, and the legs heavier. 



Otobius megnini has only three molts in its development from egg to adult 

 1 larval and 2 nymphal stages. The larva becomes very large during its 

 feeding and is what was spoken of as the "pupa-like stage" by Salmon and 

 Stiles (1901, p. 410). Whether nymph 1 ever feeds is not evident. 



Nymph 2 is the stage usually seen and from it has arisen the name 

 "spinose ear tick." This stage is small when it emerges but during its pro- 

 longed feeding it becomes very large and it appears that its striated integument 

 is correlated with its phenomenal extensibility. When ecdysis takes place there 

 is a complete change of character of the integument, the spines are lost and 

 the large hypostome is replaced by a vestigial one. 



The adult does not feed. 



HOSTS 



O. megnini appears to be largely restricted to domestic animals and most 

 of the records are from cattle and horses. Other animals known to be attacked 

 include mules, asses, sheep, goats, hogs, dogs, cats, coyotes, deer, mountain 

 sheep (Oris canadensis) , cottontail rabbit (Sylvilagus sp.), jackrabbit (Lepus 

 californicus walla walla), and ostrich. There are several records of occurrence 

 of nymphs in the ears of man. 



