Ecology 



All stages congregate on walls, in crevices, or between boards 

 of poultry houses. Around Cairo we find literally tens of thousands 

 under loose bark, in crevices, and on the trunks of trees in city- 

 park heron rookeries. Trees in which chickens roost are frequently 

 reported as hiding places for A. persicus . Other habitats have 

 been discussed under HOSTS above. 



The ability of eggs, larvae, nymphs and adults to withstajid a 

 wide range of temperature and humidity conditions has been sttodied 

 by Bodenheimer (l93/k). Fifty-nine observations of nymphs and adults 

 in temperature gradients ranging from 2°C, to ^7,7°C. failed to ex- 

 hibit a significant response to changing temperature stimuli. While 

 the vital optimum of the egg stage is 2CPC, and 8C^ relative hvimid- 

 ity, the tolerance to fluctuating climatic factors is remarkably 

 great. Even at 2Q6 relative humidity, mortality is only slightly 

 greater than at optimum conditions of environmental moisture. The 

 thermal constant for the egg stage is 316 day-degrees. At temper- 

 atures of from 33°C, to 180C., eggs hatch in from 10,5 days to 33.3 

 days (from highest to lowest temperature), Temperatxrres of 15°C, 

 and below inhibit egg hatching. At high temperature (33°C.), a 

 relative hxomidity of at least 6Q& is necessary for hatching. At 

 noderate temperature (l8°C, to 27°G,), there is little difference 

 in numbers of larvae hatching from eggs maintained at varioiis per- 

 centages of relative hiimidity ranging from twenty to a hundred. 



The ability of A, persicus to withstand desiccation and high 

 temperatures has been studied by Lees (1947) in his excellent re- 

 search on transpiration aiid epicuticle structure in ticks. 



In Argentina, the optimum temperature for egg hatching is said 

 to be between 22°G. and 38°C, with relative humidity from 90^ to 

 10Q6, Mortality increased from U»^% under the above conditions 

 to 22, U% at 370c. and 806 to 9555 relative humidity. ^Roveda 

 (1940)_7 



It appears, from these observations as well as from the com- 

 paratively great adaptability of this species as demonstrated by 

 its wide geographical range, that Argas persicus is less restricted 

 by higher humidity factors than are many other argasids. 



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