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In Palestine, Nicholson (1919) and Dunlop (1920) attributed human relapsing fever to bites of A. persicus. Their reports were based entirely on circumstantial evidence [ cf. also Balfour (1920A,B), Woodcock (1920), MacKenzie (1920), etc.7. Experimental evidence negates this probability.

Members of my staff and I on several occasions have questioned people who spend much time in heavily infested parks and houses in and near Cairo without finding anyone who acknowledged being bitten.

Apparently reliable accounts of A. persicus infesting human huts in which chickens are also kept, and not infrequently biting persons, are those of Sergent and Foley (1910,1922,1939) from Algeria. Natives there refer to fleas and to the fowl argasid by the same name, Although the ticks are frequently associated with cases of human relapsing fever, they were proven by these observers to have a negative role in the transmission of spirochetes causing the disease.

There are a few scattered, apparently authentic reports of A. persicus biting man outside of Africa. One such, a vivid descrip tion enhanced by illustrations of the tick and of dark weals where the human victim was bitten, has been reported from Romania by Ciurea and Stephanescou (1929). The attacks occurred inexplicably in the upper stories of a new concrete apartment house and no chickens or pigeons were known to have been associated with the buildings.

With regard to the lively account of attacks by "A. persicus" on indigent persons in Chile (Porter 1928), see A. reflexus, p. 77.

Reptile and Amphibian Hosts

Although A. persicus always shows a predilection for avian blood, it will feed on toads if the skin of these animals is warmed, according to Galli_Valerio (1911B). The blood is probably toxic for the ticks die afterwards.

The record of A. persicus from a tortoise in Iran (Michael 1899) is most probably based on misidentification or incorrect or incomplete specimen labelling.

Infestation of Human Habitations (Africa)

African records of A. persicus in huts of indigenous people (inferred presence of chickens in some huts) are: Annecke and Quinn (1952) for South Africa, Drake_Brockman (1913) for Somali. land, Sergent and Foley (1919, 1922,1939) for Algeria, and Sudan records above. Lounsbury (1903B) stated that the fowl tick seldom occurs in South African houses unless chickens are kept close by.

BIOLOGY

Life Cycle

Among the many references to some phase or other in the life cycle of A. persicus, some of the more important are: Lounsbury (1903B) for South Africa, Nuttall et al (1908) for laboratory observations, Olenev (1928A) for the Saratov area of Russia, Roveda (1940,1950) for Argentina, Bodenheimer (1934) on temperature and humidity tolerance, and Zuelzer (1920A,B,1921) on feeding, excretion, and life cycle. Hooker, Bishopp, and Wood (1912) contributed a detailed study of the life cycle in southern United States and reviewed earlier literature. These authors also provided data on growth and size of the fowl tick.

The life cycle in general under favorable conditions requires about four months.

Larvae attach usually to the base of the host's wing. They feed there for five to ten days before dropping from the host and seelding shelter. Nymphs and adults become satiated in from five minutes to two hours and then seek a sheltered place in the build ing, yard, or tree in which they secrete themselves, Feeding is usually done at night, sometimes in subdued light, seldom if ever in strong Light.

Coxal fluid is emitted within a few minutes after engorgement is complete and often while the tick is stationary or moving about the host, but only infrequently while the mouthparts are still in serted in the host's skin.

Digestion is extremely slow and fowl blood may be identified by the precipitin test for at least 23 months after ingestion (Gozony, Hindle, and Ross 1914).

The following notes are chiefly from Hooker, Bishopp, and Wood (1912). Many more details may be found in their report.

Usually females oviposit after each meal, which may number up to six or seven in a lifetime. Under exceptional conditions, a female may require two blood meals before laying eggs. The greatest number of eggs deposited after the first few blood meals increases progressively from 195 to 646, but decreases after sub sequent feedings to as few as 47 eggs following the seventh or last feeding. The average number of eggs laid after each engorgement was:

first, 131; second, 159; third, 133; fourth, 110; fifth, 97; sixth, 95; seventh, 47. Eggs are laid in the adult tick's retreat.

Oviposition generally commences four to ten days after feeding, in summer sometimes as early as the third day. In winter or in the absence of males, egg laying may be delayed for weeks or months. Oviposition of moderately large batches continues over a six to ten day period but only three days are required for depositing a small number of eggs. In nature it appears that the fowl argas seldom engorges and oviposits more than five times, unless females com mence feeding early in the spring.

Incubation of eggs extends over an eight to eleven day period in warm summer weather, but in cooler climates or seasons this period is extended to three weeks or even longer.

As stated above, larvae generally feed for from five to ten days, but they may complete engorgement in three or four days, and Rohr (1909) recorded two days. There is some indication that quiet, setting hens allow the greatest member of larvae to thrive, and that different breeds of hosts exert no influence on larval development. In NAMRUL 3 laboratories, Dr. Herbert S. Hurlbut (unpub lished) is finding that only a moderate number of larvae kills chickens used in his experiments, apparently not doing so by trans mission of pathogenic organisms or by exsanguination. Nymphs and adults resulting from these larvae have no observable deleterious effect on their hosts. Reasons for this exceptional larval toxico ity have not yet been ascertained.

Larvae survive unfed for over five months in cool weather, but in Texas during midsummer they succumb in about two months. At 30°c. and 70% R.H., unfed Egyptian larvae survive for up to thirty days (H. S. Hurlbut, personal communication).

Larvae molt to nymphs in warm summer weather about four days following completion of feeding.

Nymphs usually feed twice, in a matter of half an hour (sometimes two hours) and molt a week or two (sometimes longer) afterwards. Some nymphs undergo a third molt before reaching adulthood; this phenomenon cannot be correlated with sex, food supply, or climatic conditions. Unfed second instar nymphs survive up to a year but first instar nymphs are known to live for only up to nine months.

Female feeding has been discussed above. Copulation is simi. lar to that described for 0. moubata (page 134).

Adults may live as long as three years without food (Laboul. bene 1881) but this appears to be exceptional. Unfed adults gen erally succumb more rapidly than engorged adults, which normally appear to live from five to thirteen months, but which may on occasion survive longer.

Besides being a particularly intriguing study for some workers, the ability of the fowl tick to withstand starvation for long pe riods no doubt accounts in part for its wide distribution and large numbers. Observations made by Newman (1924) on longevity without food were summarized as follows: Test 1: An isolated female lived two years and three months, (2) it produced fertile eggs four months after isolation, and (3) larvae lived for three months. Test 2: (1) Males died four months after isolation, (2) first female died after two years and four months, (3) two females lived three years, (4) three females lived four years, and (5) the maximum time a few male lived was four years and five months. Removal of fowls from a house or yard is in itself of little use in ridding the premises of ticks.

Larval survival without food for 228 days at 22°c. to 26°C. and 90% to 100% relative humidity was reported by Roveda (1940). At temperatures of 37°c. to 38°c. and at relative humidities of 85% to 100% larval survival was reduced to an average of 50 days.

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 citypark 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 withstand a wide range of temperature and humidity conditions has been studied by Bodenheimer (1934). Fifty-nine observations of nymphs and adults in temperature gradients ranging from 2°c. to 47.706. failed to exhibit a significant response to changing temperature stimuli. While the vital optimum of the egg stage is 20°C, and 80% relative humida ity, the tolerance to fluctuating climatic factors is remarkably great. Even at 20% relative humidity, mortality is only slightly greater than at optimum conditions of environmental moisture. The thermal constant for the egg stage is 326 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). Temperatures of 150C. and below inhibit egg hatching. At high temperature (33°C.), a relative humidity of at least 60% is necessary for hatching. At moderate temperature (180C. to 2700.), there is little difference in numbers of larvae hatching from eggs maintained at various percentages of relative humidity 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 and epicuticle structure in ticks,

In Argentina, the optimum temperature for egg hatching is said to be between 22°C. and 38°C. with relative humidity from 905 to 100%. Mortality increased from 4.85% under the above conditions to 22.45% at 3pc. and 80% to 95% relative humidity. [Roveda (1940)

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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