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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 7(¥ R.H., unfed Egyptian larvae survive for up to thirty days (H. S. Hurlbut, personal comrmlnication).

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

Nymphs usually feed twice, in a mtter of half an hour (sometimes two hO‘\II‘S) and malt 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 nim nmnthso

Female feeding has been discussed above. Copulation is similar to that described for Q. moubata (page 134).

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Adults my live as long as three years without food (Laboul. bene 1881) but this appears to be exceptional. Unfed adults generally 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 withsta.nd starvation for long periods no doubt accounts in part for its wide distribution and large mnnbers. Observations mde by Newman (1924) on longevity without food were summarized as follows: Test 1: An isolated female lived two years and three nnnths, (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 renEIE‘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 female lived was four years and five months. Remval of fowls from

a house or yard is in itself of little use in ridding the premises of ticks.

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Larval survival without food for 228 days at 22°c. to 2ePc. and 9% to 10% relative humidity was reported by Roveda (191.0). At temperatures of 37°C. to 38°C. and at relative humidities of 855 to 10% larval survival was reduced to an average of 50 days.

Eco log

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, a.nd on the trunks of trees in city. park heron rookeries. Trees in which chickens roost are frequently reported as hiding places for E. pgrsicus. 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-L Fifty-nine observations of nymphs and adults in temperature gradients ranging from 2°C. to 47.7°C. failed to ex. hibit a significant response to changing temperature stimuli. While the vital optimum of the egg stage is 20°C. and 8% relative humid. ity, the tolerance to fluctuating climatic factors is remarkably great. Even at 2% relative humidity, nnrtality is only slightly greater than at optinmm conditions of environmental moisture. The thermal constant for the egg stage is 316 day.degrees. At temper. atures of from 33°C. to 18°C., eggs hatch in from 10.5 days to 33.3 days (from highest to lowest temperature). Temperatures of 15°C. a.nd below inhibit egg hatching. At high temperature (33°C.), a relative humidity of at least 6% is necessary for hatching. At moderate temperature (18°C. to 27°C.), there is little difference in numbers of larvae hatching from eggs mintained at various per. centages of relative humidity ranging from twenty to a hundred.

The ability of E. rsicus to withstand desiccation and high temperatures has been st by lees (191.7) in his excellent re. search on transpiration and epicuticle structure in ticks.

In Argentina, the optinmm temperature for egg hatching is said to be between 22%. and 38°c. with relative humidity from 903 to 10%. Mortality increased from 4.85% under the above conditions to 22.45% at 37%. and sqt to 95% relative humidity. [Reveae

(191.0)_7

It appears, from these observations as well as from the comparatively great adaptability of this species as demonstrated by its wide geographical range, that Argas rsicus is less restricted by higher humidity factors than are mny other argasids.

In cold climates such as Saratov, Russia, development occurs only at temperatures over 20°C. Exposure to high humidity (pre. sumably at cold temperatures) kills the ticks (0lenev l926,l928A).

The presence or absence of A. rsicus in coastal areas fre. quently is referred to in literature. Iounsbury (19038) stated that A. Ersicus is everywhere common in South Africa, including coastal towns a.nd areas. Howard (1908) reported that in South Africa this tick is common except near the coast and that the same distributional pattern had been reported from Australia. Records from a number of other localities indicate that the fowl tick does indeed inhabit coastal areas. For instance, Theodor (1932) reports this species especially common along the Mediterranean coast and in Jordan Sea areas of Palestine. In Egypt, we find it commonly in coastal villages and cities. We have also found cast nymphal skins at Djibouti, the seaport of French Sommliland. It occurs at Port Suian on the Red Sea coast of Sudan (Sudan Gov. ernment Collection record) and at Hodeida on the opposite coast in Yemen (Hoogstraal, ne.). In Reunion, Gilla.rd (191.9) reported the fowl tick particularly common on the coast, and in Madagascar it occurs chiefly in coastal areas (B'1'1ck 1935 ,l91.8A,C).

Concerning altitudinal range, A. rsicus is frequently reported as commnon in lowlands and rare or absent in highlands. In mountains of the Sinai Peninsula of Egypt we find numerous speci... mens at elevations up to 6000 feet.

Lewis (l939A) stated that in Kenya 5. rsicus is present only in European areas. This is certainly not true for the Sudan, where chicken flocks of mny remote, indigenous tribes have been known to be infested for half a century. More recently, Wiley (1953) indi. cated that the fowl tick is increasing its range in Kenya.

An apparent negative geotropism displayed by unfed larvae reared from adults collected from trees serving as a heron rookery has been observed by Dr. H. S. Hurlbut at NAMRIL3, Cairo. At the same time, la.rvae from adults collected from chicken houses ap. peared to show a positive geotropism. The F1 larvae of adults from heron rookeries were inclined to prefer herons rather than chickens as hosts a.nd the reverse appeared true for larvae from adults from chicken houses. Informal as these observations are, they suggest an interesting research problem.

DISEASE RELATIONS

MAN: Reported sequelae of the fowl argas‘ bite range from

itching to death. Actually, there are no trustworthy accounts

of severe illness resulting from a fowl argas bite. Anthrax (Bacillus anthracis), however, has been transmitted to man by the bi e 0 his tick in the laboratory on one known occasion. Speci. mens have been experimentally infected with plague (Pasteurella

stis) and with yellow fever virus. A. rsicus has en reported

in textbooks and discussion papers to transmit human relapsing fever (Borrelia spp.) but there does not appear to be a shred of conclusive evidence to support this claim. Experimental studies to date negate this possibility. The little work done on_A. égg. sicus in relation to typhus has gone only far enough to show at the etiologic agent (Rickettsia owazekii) survives in the tick for ten days. The fowI tick is susce i e to parenteral infection with Nest Nile virus but does not transmit the virus.

FOHIS: The fowl argas is frequently so numerous that birds are killed by exsanguination. Spirochetosis ZrBorrelia anserina (: B. allinarum)_7 of chickens, ducks, geese, turfiys afi canaries is a serious disease transmitted by A. rsicus nearly everywhere that it is foun, but not everywhere. §owI piroplasmosis Ae ianella pgllorum) is also transmitted by the fowl argas, whic so has been suggested to be a vector of Grahaella allinarum. A condition called fowl paralysis by some students tic paralysis by others, due possibly to a toxin from the tick, sometimes occurs after bites. Chicken cholera or fowl plague (Pasteurella avicida) may cause the death of birds that eat infected ticks. Virus in_ duced fowl tumors are not transmitted by bites of the fowl argas. See next paragraph.

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WIID BIRDS: Populations of this tick from Egyptian rookeries of the buff_backed heron or cattle egret have been found infected with Salmonella typhimurium, but others from chicken yards were negative for Salmonella spp.

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CATTIE: Successful experimental transmission of anaplasmosis

(Anaplasma marginale) by A. pgrsicus has been reported.

MIQIELLANEOUS: It has been claimed that West African speci. mns have been found infected with Q fever (Coxiella blrnetii). In Egypt, the fowl argas is infected with one or more v1rus'es distinct from West Nile but otherwise unidentified.

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REMARKS

An excellent and detailed study of the internal and external morphology of A. rsicus has been presented by Robinson and David. son (1913A,B,1'911.), '_'d'byen Patton and Crag (1913). An earlier work is that of Heller (1858). Rohr (1909 reported on life cycle and biological sttdies in Brazil, and incluied a few photomicro. graphs of internal organs. Regeneration of broken appendages has been reported by Hindle and Cunliffe (1911.) and by mitten (192013). Sensory perceptions have been studied by Hindle and Merriunn (1912). The coxal cymtium of A. rsicus has been discussed by Schulze (l936A), who also (191.1) escr and illustrated the haller's organ. Micks (1951) gives an account of a convenient rearing technique and life cycle observations and Sapre (19/.3) described his method for laboratory rearing. Ixmmmity of chickens to bites of the fowl argas has been studied by Trager (191.0). Anticoagulin in the salivary lands and gut has been reported Nuttall and Strickland (1909 and by Cornwall and Patton (1911. . The salivary glands have been described and illustrated by Heller (1858) and Elmassian (1910).

Larvae of clothes moths, Tineola biselliella, have been ob.

served attaclcing living larvae of I. Ersicus in' laboratory colo. nies (volimr 1931). '

According to Zuelzer (1921), B. rsicus and B. reflexus mate and produce fertile offspring. We have Een unable to duplicate these results in our Cairo laboratories.

Observations on the bacteriostatic factors in blood..engorged ticks, including A. rsicus (Anigstein, Whitney, and Micks 195%, B), prompted further s es showing that bacterial growth inhi... bition in vitro is comparable with the phenomenon induced by anti. biotics-(WH51§y, Anigstein, and Micks 1950) and that a blood hydrolysate called sanguinin is responsible (Micks, Whitney, and Anigstein 1951). This subject is reviewed under B. moubata (page 178

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