and thus to form a very efficient seal of the ostium, a necessary 

 condition for animals so likely to be exposed to desiccation, 

 ^It is of interest to compare Browning's study with that of 

 Arthur (in press) on the spiracle of Ixodes 7 . 



According to Mellanby (1935 )» the physiological reaction 

 that governs the opening and closing of the spiracular ostium is 

 similar to that of insects. Browning (195AB) appears to accept 

 this conclusion. The physiology of spiracular action has been 

 discussed under Environmental Adaptability above, 



Haller's Organ 



The structure of haller's organ and its supposed value as 

 a phylogenetic indicator has been discussed by K, W. Neumann 

 (194.33. Schulze (1941 J also described and illiistrated haller's 

 organ, which functions as an organ of smell. Incidentally, 

 Zumpt (19A9) summarized his studies on the systematic importance 

 of this structure as follows; Research up to now indicates that 

 haller's organ will have to be considered in the future as having 

 a role in tick systematics and should not be overlooked. 



Abnormal Development 



During examination of about eight thousand laboratory reared 

 specimens of 0. moubata, Robinson (19^3A) encoimtered two examples 

 of partial twinning of the posterior area in a third instar nymph 

 and in a fifth instar nymph that subsequently molted to a male 

 and female, each with abnormalities in internal anatomy. These 

 specimens were normally fertile. Another peculiarly humped third 

 instar nymph normally molted to a male that showed suppression 

 of the postanal region. This male failed to copulate although 

 the genital system was well developed and the sperm normal, Robinu 

 son (19AAB) also noted many abnormalities of the legs during handling 

 of about ten thousand tampans, I'tost cases were deficiencies due to 

 parti ad regeneration of a leg damaged in a previoiis nymphal instar. 

 Two cases of supernumerary segments of legs were also observed and 

 illustrated. In the same batch a nymph that was much more complete- 

 ly twinned posteriorly than previous examples was observed. This 

 specimen molted to a partially twinned female, mated normally, 

 refused to feed, and deposited a small egg batch (not particiilarly 



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