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Study of comparative morphology in the genus Rhi ce alus and of chaetotaxy in the family Ixodidae led Pomeran zev to reconstruct radially generic concepts of this family. This approach merits further investigation; however, the pitfalls of hasty conclusions based on worn or field collected specimens, in which the chaetotaaclc picture is imperfect, may result in aiditional confusion of species concepts (Hoog_ straal 19550).

Rhipicephalids tend to considerable variation in appearance and morphological details owing to crowding on the host, welfare of immature stages, and availability of suitable hosts, factors that play a part in the determination of size, robustness, and even certain physical characteristics. Distinguishing characters in many specimens tend to become so generalized that diagnosis is difficult. This is especially true for females. The question of biological races remains to be explored; many data suggest this phenomenon to be operable in certain groups of rhipicephalids. The genus is divided into clearly defined species and species variable enough to cause confusion. It contains extremely cormnon as well as rare species.

Host predilections within this genus are fairly wide among several groups of available animals, although the lack of interest in other animals easily available in the same area is conspicuous by rarity of records of their infestation. A few species, such as R. Eavus, have an exceedingly wide host range, being common. ly taken on man and all domestic and many feral animals, such as carnivores, antelopes, hares, birds, elephant shrews, elephants, buffalos, and others. Other species, such as R. distinctus from hyraxes, are known only from a single lcind of host. It is sig_ nificant that immatures and adults of most rhipicephalid species do not attack birds and reptiles.

The life cycle is either the two host or the three host type and hosts of immature stages may be either the same as those parasitized by adults or smaller and different animals. In some species, records of larvae from both cattle and rodents are so common as to confuse the picture of the preferred hosts of this

stage. H. a ndiculatus is an interesting example in point.
In R. s.-'simus there is so much data indicating immature stage
predil-e'ctioT'for b1n'rowing rodents that it is disconcerting to
find that in certain areas where this tick is common larvae are

frequently found on other animals. Reasons for these differences are beyond our present ability to explain.

Immature stages of many rhipicephalid species remain un_ described and distinguishing criteria for a number of those that are known are insufficient for identification of field collected material.

Ecological stratification is quite restricted, various species being confined to forests, highlands, semidesert areas, or certain rainfall conditions. The degree and distribution of relative humidity appear to be the most critical of limiting factors. Vegetation types associated with this factor and in. fluenced by the length of the rainy season or proximity to moisture laden air beside the seas can often be associated with rhipicephalid distribution.

Economically, many species are of considerable importance as reservoirs an vectors of a variety of animal and some human pathogens. The kennel tick, R. s. san 'neus, has been shown to have a particularly wide spectruh of achhhl or potential relationships as a vector of diseases.





Eyes convex or hemispherical, distinctly

furrowed laterally or protruding from a

depression ("orbited" ) . Coxa I with

distinct dorsal projection................................ ..2

Eyes flat or slightly rounded, not
convex, hemispherical, furrowed, or
orbited. Coxe I with or without dorsal


Eyes hemispherical, in a depression

(orbited) . Adanal shields large,

enormously widened posterolaterally.

Scutum dark with dense medium and

large size punctations; color con.

treating with reddish body integument

and saffron legs. Frequently large

(about 5.0 mm. long). (Common through


Eyes convex, with an encircling fur.

row. Adanal shields mildly rounded

laterally, not exceptionally large.

Color overall brownish. Scutum with

moderately numerous fine and medium

size punctations. Fairly smll (about

3.5 mm. long). (Southeastern PRAVUS Figures 255 aE"2'33

Coxa I with distinctly pointed dorsal projection*. (Localized areas in ~an)IOIIOICOIOUDUIQQQIIOIIIIQIQQIQIQIOQOOIOICOOQQL

Coxa I without a distinctly pointed

projection though a smaller, rounded

hump may be visible in its place.

(More or less widely distributed)..........................l1

R. simus group , a small parasite of canerats only,

_ sim soni _ typically Ears tfls projection but this projection is so small

and frequently so reduced that it is not considered distinct enough to include in this section.




Lateral grooves faint, absent, or
indicated only by a row of puncta.

Lateral grooves distinct as such#............................8

Scutal punctations in more or less

definite rows of'R. simus type,

interstitials varIabI5'5Et always

insignificant in comparison with

primary punctations..........................................6

Scutal punctations scattered, not

Posteromedian and paramedian grooves

absent. Adanal shields with inner

margin in a straight line centrally

and with a peculiar protrusion at

juncture of inner and posterior margins........................................R. LONGICOXATUS


Posteromedian groove long, narrow,

paramedian grooves shorter, wider,

less well defined. Adanal shields

with inner margin concave centrally

and its juncture with posterior I
margin rounded....................................R. B



Basis capituli sharply angled lat.

orally and with long cornua. Scutal

punctations large, unequal, unevenly

distributed, small laterally, larger anteriorly..........................................R. ARNOLDI

'Figure 213

Basis capituli slightly convex lat.
erally and with brief cornua. Scutal
punctations medium size, superficial,



fR. distinctus atypically may have apparently shallow lateral grooves due to the size and depth of the row of large punctations in its bed.




[blocks in formation]

Lateral grooves without prominent

punctations. Adanal shields with

both posterior marginal junctures

extended, the outer juncture spur_

like, the inner rounded or spurlike;

accessory shields distinct and pointed..........................................R. TRICUSPIS


Scutal punctations moderate size,
rather few and well spaced central.
ly, even fewer or none laterally.
Cervical fields moderately or non_

reticulate. (Common only in Yei

Figures ZZU ho ZZ2

Scutal punctations large , dense ,
partly confluent. Cervical fields
0 0 0 0 0 u 0 0 0 0 0 0R0


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