servation would appear to indicate that the immature stages overwinter.

In southern and eastern Europe, adults appear on hosts in the middle of April, are most numerous from May to July, and by the middle of September again become scarce (Enigk 1947).

In equatorial climes with rainy and dry seasons, ticks are frequently reported as most noticeable at the commencement of the rains and this has been assumed to be an indication that they are then most numerous.

Though two or three generations a year seem likely almost wherever the kennel tick ranges, no definite reports concerning this based on observations in nature are available.

Overwintering of the tick in temperate climes is probably entirely indoors. For example, MacCreary (1945) states that there is no evidence of overwintering outdoors in Delaware. This tick does not survive long at temperatures under 5°C. (Enigk and Grittner 1953).

In NAMRU3 (Cairo) laboratories, as a piece of research correlative with field findings, Dr. Samira El Ziady is undertaking an ecological study of populations from domestic and from wild local stocks, under controlled conditions. Two years will be required to obtain significant data on this subject.

Parasites: The most commonly reported parasite of the kennel tick* is the chalcid, Hunterellus hookeri Howard, 1907 (= Ixodiphagus *Habrolepis sp. (Chalcidoidea, Encyrtidae) has been reported to parasitize immature stages of R. s. sanguineus in French West Africa (Risbec 1944). An inquiry concerning this report, addressed to the United States National Museum, resulted in the following statement by Dr. B. D. Burks: "This undoubtedly refers to Habrolepis caniphila Risbec, 1951, Mem. Inst. franc. d'Afr. Noire, 13 (pt. 1), p. 170. This is Hunterellus hookeri How.; I saw the types in Paris last year. Ferriere had already (1953) published a note stating that Risbec's species probably was hookeri, just on the basis of the original description. In 1953, Risbec published a paper transferring his species to Hunterellus, but he still thinks his species can be separated from hookeri

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caucurtei du Buysson, 1912), a wasp known in many areas of the world. It is specialized for parasitism of ixodids and infests most genera. A related species, H. theilerae*, has been described by Fiedler (1953) from R. oculatus and H. truncatum in southern Africa. knowledge of these parasites will be completely reviewed in a forthcoming volume of this work, but a few preliminary remarks are indicated.

Our

In Africa, parasitism of the kennel tick by H. hookeri has been occasionally reported. Nigeria (Philip 1931A,B). French West Africa (Blanc, Goiran, and Baltazard 1938. As Habrolepis sp.: Risbec 1944). Uganda (Fiedler 1953, Steyn 1955). Angola (Fiedler 1953). Kenya (Philip 1954). Kenya (Philip 1954). We have thus far been un able to find this wasp in Egypt, where the climate is probably too dry for its existence.

Other tick species known to be attacked in Africa are Hyalomma (sp. truncatum, according to Theiler, correspondence) and H. leachii in South Africa (Cooley 1929,1934); R. e. evertsi in South Africa (Bedford note in Cooley 1929); species not mentioned, from Mozam bique (Howard 1908); and A. tholloni from the latter area (Santos Dias 1949D).

R. s. sanguineus also is attacked by H. hookeri in Brazil (da Costa Lima 1915), U.S.A. (Smith and Cole 1943, includes review of previous reports), and other areas of the world.

As summarized by Smith and Cole (1943), infestations of H. hookeri in nature are not known markedly to reduce tick popula tions. Experimental attempts in this direction have been in effective for tick control even when millions of parasites were released (Cooley and Kohls 1933) to attack the Rocky Mountain spotted fever vector, Dermacentor andersoni (Stiles). Soviet experiences with this parasite have been reviewed by Pervomaisky (1947) and Blagoveschensky (1948).

*Dr. B. D. Burks states (correspondence) that this unquestionably is a distinct and valid species.

Larvae of H. hookeri feed on all contents of engorged nymphal ticks and pupate in the body of the host. Adult wasps emerge from the nymph by gnawing a hole through the host's expanded integument. Mating occurs soon after emergence. Oviposition, by insertion of the ovipositor through the tick's integument, may follow immediate ly after mating. Unfed nymphs are preferred for egg laying, though oviposition in engorged nymphs also occurs. Eggs are sometimes laid in tick larvae; in these, however, the parasite undergoes a latent period until after the larval nymphal molt. Latency con tinues in unfed, hibernating ticks until they commence engorging. Cooley and Kohls 1928,1934.7

Brumpt (1930), who experimented with rearing this parasite in R. s. sanguineus, noted that a period of some 83 days passes before nymphs exhibit signs of parasitism, a factor of practical interest in transportation of the wasps to new areas or labora tories.

Adult wasps may sometimes be noticed running rapidly on the dog's hair in search of ticks (da Costa Lima 1915, Philip 1931A,B).

Morphological characters of tick parasitizing wasps have been compared by Steyn (1955) who concludes that H. theilerae might be expected to be of greater value in biological control than the other species. (If, however, H. theilerae is actually as infrequent in nature as present scanty records suggest, its range of physiological adaptability may negate this possibility HH).

Predators: In a Corsican house invaded by both kennel ticks and Theridiid spiders, Teutena triangulosa Wick., the spiders were observed feeding on the ticks (Sautet 1936). Under experimental conditions, they fed on both the immature and adult stages and young spiders attacked ticks shortly after hatching. Although the predators also fed on flies, they showed a preference for ticks. Under August, midsummer conditions, the spider life cycle from egg to adult required three weeks. Six to twelve eggs were laid in each webbed mass, and females produced from eight to ten of these balls.

In Russia, a staphylinid beetle, Juracekia asphaltina, devours Rhipicephalus ticks (?R. sanguineus) in nests of the ground squirrel, Citellus pygmaeus (Flegontova 1938).

DISEASE RELATIONS

Role in Nature

It

MAN: R. S. sanguineus, in some areas, is considered to be the principal vector of boutonneuse fever (tick-bite fever), Rickettsia conorii, (see, however, page 687). It is known to transmit the rickettsia causing the closely related "Indian tick typhus". is a vector of Rocky Mountain spotted fever (R. rickettsii) in the warmer parts of the Americas. It is said to be the vector of a virus causing "Congolese red fever", a syndrome of moot identity and etiology.

Persons bitten by this tick sometimes complain of pruritus, due possibly to injection of a toxin while feeding.

A number of the pathogens listed under experimental relations below may be transmitted in nature but the details have not yet been elucidated.

DOGS: R. s. sanguineus transmits two diseases to dogs, the highly fatal canine rickettsiosis, caused by Rickettsia canis, and canine piroplasmosis, or malignant jaundice, caused by Babesia canis. In addition, it is an intermediate host of Hepato zoon canis which results in an anemia and infection when dogs swallow ticks. Tick typhus or boutonneuse fever, Rickettsia conorii, is apparently transmitted among dogs and from dogs to man by the kennel tick. It seems likely that this arthropod transmits Salmonella enteritidis, which causes a paratyphoid disease in dogs and in laboratory animals. When dogs are heavily infested, loss of blood and nervous energy from irritation may be severe. See also experimental relations below.

Other domestic animals: Spirochetosis of sheep, goats, horses, and cattle, caused by Borrelia theileri, is transmitted by the brown dog tick in some areas.

Although this tick has been incriminated as a vector of several pathogens of bovine diseases, it cannot be ascertained from the literature that they are yet known to play any real role in the transmission of these diseases in nature.

is true for other diseases of horses, goats, sheep, and dogs, listed below.

Experimental (Human Diseases and Syndromes)

Tick paralysis (venom or toxin): This syndrome can be in duced in experimental animals by injection of the ticks' eggs and ovaries.

Yellow fever: Although the virus remains viable in this tick for some time, it is not transmitted by biting.

Scrub typhus: Rickettsia tsutsugamushi is not transmitted by the kennel tick.

Q fever:

Coxiella burnetii has been found naturally in fecting R. s. sanguineus and experimental transmission has been demonstrated but apparently no cases of Q fever in man attributable to this tick have been reported.

North Queensland tick typhus: It has been suggested, on epidemiological grounds only, that R. s. sanguineus might pos sibly be a vector of this rickettsia.

"Sao Paulo or Minas Gerais typhus": Rocky Mountain spotted fever; cf. above.

Louse borne typhus: This tick does not transmit Rickettsia prowazeki.

Relapsing fevers: Spirochetes, Borrelia hispanica, can be transmitted to guinea pigs and man by the bite of this tick, which is not, however, known to be a vector in nature. Attempts at transmission of the "Greek variety of B. hispanica have been unsuccessful and only exceptional transmission of B. persica has been obtained.