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and lower average relative humidity probably modify this tick's ecological thresholds (HH).
In southern Africa, low temperature and high altitude do not in themselves limit the range of H. truncatum. It occurs in all types of South African vegetation except in short grass of the highveld, a mountainous zone associated with high rainfall, and is rare or absent where snow falls.
From the size and variety of collections examined, it appears that in comparison with H. rufipes, H. truncatum may be somewhat less numerous and more widely ranging in southern Africa but that the reverse is true towards and beyond the equator. This matter, however, requires more careful study. H. truncatum is rare or never present in the forests of western I*LC 8
This species was not collected in high rainfall areas of the Cameroons (Unsworth 1952), and is unusual if not entirely absent on the humid west bank of Equatoria Province in the Sudan.
In Northern Province of Nyasaland, where H. truncatum is the only species of this genus that is found, females engorge on cattle chiefly during the dry season (March, April, May) but also in small numbers during other months of the dry season. Nymphs were found on hares early in the rainy season (October) and also in December (Wilson 1946).
Adults attach in the brush of hair at the tip of the tail, between the hooves, in the inguinal and perianal areas, and on the scrotum and udders.
A hymenopteran parasite, Hunterellus theilerae, has recently been described from nymphs of H. truncatum of Southwest Africa and from nymphs of Rhipicephalus oculatus from Transvaal (Fiedler 1953). Cooley # reared Hunterellus hookeri from nymphs of "H. aegyptium" in South Africa, but it appears that he included both H. truncatum and H. rufipes under this name.
# Tick paralysis (toxin or venom). Q fever (Coxielle burnetii).
CATTLE: Sweating sickness (virus). Lameness and paralysis in calves (toxin or venom).
SHEEP: This tick may be associated with footrot of sheep, a secondary infection by bacteria, and lesions from its bites may lead to lameness.
HORSES: Not a vector of horsesickness (virus).
NOTE: This species should be considered as strongly suspect in the transmission of rickettsial organisms among domestic and wild animals.
A somewhat deformed specimen of H. truncatum has been described and sketched by Santos Dias (1947B) and another (as H. savignyi) by Tendeiro (1951F).
In various papers by E. A. Lewis on work in Kenya, based largely on H. truncatum (cf. Hoogstraal 1954C), the author refers to rearing experiments by Nuttall (1913) and Patton and Cragg (1913) as being accomplished with the same species. Since Nuttall's material originated in Algeria and Patton and Cragg's in India, these workers obviously utilized different species. The material used by Nuttall, now in British Museum (Natural History) collections, reported as H. aegyptium, is H. marginetum.
The 4500 specimens of H. truncatum from throughout Africa that have been examined for the present study are highly distinctive and show considerably less variation than encountered among most other species in this genus. This observation is diametrically opposed to Feldman-Muhsam's (1954) remarks: "Examination of laboratory-bred material . . . . . . . . .
showed an enormous range of variation between the offspring of one female". As much caution must be employed in evaluating laboratoryreared specimens as in evaluating field-collected material. Under abnormal, artificial conditions, some individuals that would not survive in the field may be protected enough to maintain the life they would otherwise lose under inclement conditions. Artificial conditions in themselves obviously induce morphological modifications. At any rate, extremely few atypical specimens are found in field collections.
Males: The scutum is black or reddish-black and measures approximately 3.3 mm. long and 2.3 mm. wide. It is characterized by long, deep, distinct, cleanly cut lateral grooves; smooth, glossy, impunctate surface except caudally, where there is a dense patch of large, contiguous punctations. The scutum is narrowed posterior of the spiracular plate, but the posterior margin is usually not so squarely truncate as in H. impressum. The festoons number seven and the central one is not morphologically differentiated, as compared with H. albiparmatum in which the central festoon forms a parma resembling a #. celluloid watch cover, variable in size, shape, and color. Ventrally, the small rectangular subanal shields lie posterior of the axis of the larger, rectangular adanal shields. The legs are reddish brown with bright paler rings.
Variable field collected males may be small and stunted and lack the subanal shields. Such specimens are the basis of Schulze's, so called "H. lewisi" in the "subgenus Hyalomina" (page 521). Collections from a few areas show somew In OI"e than ordinary scutal punctation. The long, clear, cleanly cut lateral grooves indicate that such specimens are H. truncatum and not lightly punctate H. impressum, as does also the comparatively more rounded posterior margin of the body.
Although H. marginatum occurs with H. truncatum only in rare localities at the northern periphery of the range of the latter, it may be well to add that the scutum of H. truncatum is characterized by fewer scapular and central punctations;
longer and cleaner lateral grooves; glossier surface; often somewhat smaller size; obsolescence of posteromedian and paramedian grooves in the caudal field of dense punctations; and narrowed posterior margin. Field collected specimens of these two species that might be confused have not been observed during the present study; Feldman-Muhsam (1954), however, states that laboratory-bred series might be confused.
Females are easily recognized if only by the genital apron, the character of which is accentuated rather than decreased by enormous engorgement. The apron is a transversely elongate oval of somewhat variable shape; in profile it is surmounted anteriorly by a narrow, bulging lip; centrally it is deeply depressed (or concave); posteriorly it is bounded by a more or less distinct lip that never protrudes as much as the anterior lip. Feldman-Muhsam's (1954) figure 2F of this apron is a surprisingly unsatisfactory representation of its actual appearance and supports the assumption that this species did not prosper during the laboratory study devoted to it.
The scutum of practically every field collected female is blackish and with few punctations among which a few fine ones may be scattered. The scutum of a few specimens bears larger, superficial punctations scattered about its surface; that of greatly engorged specimens, as usual in this genus, is rugose. In the few specimens with a more punctate scutum, the genital apron is nevertheless highly distinctive and the glossy scutal appearance is retained.
Note that no known characters distinguish the females of H. truncatum from those of the less common and more restricted
NON-SUDANESE SPECIES OF HYALOMMA
(Figures 190 to 211)
In order to better understand this group, illustrations and
selected data for all species presently-recognized in the genus Hyaloma have been assembled in this section.
KEY TO ALL PRESENTLY RECOGNIZED
Without Subanal shields. Festoons
not fused. Adanal shields un
usually large and wide. Scutum
with few large, scattered puncta
tions and long, clear lateral
grooves. £ . (Subgenus
Hyalomine * - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - - -H. HUSSAINI
With subanal shields (exceptional, deformed runts may lack subanal
*The status of H. kumari, Sharif, 1928, which falls into this classification, is uncertain.