Page images
PDF
EPUB

third of the dorsum.

The female is similarly broad; its scutal margin is notched or concave posteriorly rather than broadly rounded. These two snake ticks are the only inornate aponommas known to occur in Africa.

IDENTIFICATION

Males and females are easily identified in the African tick fauna by key characters and notes.

BOOPHILUS

INTRODUCTION

Boophilus ticks are practically unique in that their entire life cycle from larva to engorged, mated adult is confined to a single host. Females drop to the ground to oviposit. This single host type of life cycle has numerous biological advantages. It also allows for particularly easy control by dipping infested animals, a benefit partially negated by the development of boophilid strains resistant to chemicals.

The boophilid type of life cycle eliminates danger-ridden periods between two or three different kinds of hosts, possibly in inhospitable areas and for indefinite periods. The predilection of these ticks for large domestic animals particularly favors wide spread dispersal and survival, not only within a continent but also from continent to continent on imported hosts.

Cattle are the chief hosts throughout the world, horses, other domestic stock, and wild antelopes and deer are less frequently attacked. Other wild animals are uncommonly infested. The veterinary importance of Boophilus ticks is considerable and they are suspect as reservoirs of some human disease pathogens.

Collectors who wish to be assured of accurate identification of their boophilid material should make every effort to obtain long series and to find the small, yellowish males as well as the heavier, more conspicuous, podshaped females.

Two of the three species presently recognized in this genus occur in the Sudan. One of these, Boophilus decoloratus (Koch, 1844), is endemic and ranges widely throughout African areas with relatively high rainfall and with some shrub cover; it is well known practically everywhere on the continent south of the great northern deserts and semideserts.

The second species is B. annulatus (Say, 1821) (= B. congolensis Minning, 1934), African populations of which cannot be dis tinguished from the famed American Texas fever vector, B. annulatus. This species is poorly known, more restricted, and less common in the Ethiopian Faunal Region than B. decoloratus and has been intro

duced from elsewhere. Data in the present report are the only published facts that give any information on the biology or ecology of B. annulatus on this continent. North African and Near Eastern populations usually called B. calcaratus subspp. appear to be identical to B. annulatus.

The third species, B. microplus (Canestrini, 1888) (= B. fallax Minning, 1934), is not yet known from the Sudan. This pantropical cattle parasite appears slowly to be extending its present southern and eastern African range northwards after once having been more widely distributed on Africa because of frequent importation of infested cattle from Madagascar. Differential characters for this species are provided in the following key and additional notes concerning it may be found following the discus sion of the two related species.

What has been considered the classic taxonomic work on Boophilus is that of Minning (1934,1935,1936). He divided the genus into three subgenera: Boophilus (sensu strictu), Uroboophilus, and Palpo boophilus and described a number of "new"" species. These subgenera have been given the status of genera in many pub lished papers, probably because Minning himself, curiously enough, failed to place a generic designation before them in his discus sion of species. Several later workers (Cooley 1946, Anastos 1950, and others) have questioned the worth of these findings, and in the present instance the Minning reports are of little value. The method appears to have been to hastily examine a few specimens from widely scattered areas, to describe and illustrate them inadequately, and whenever possible to apply names based on assumed, uncritically regarded, slight morphological variations. There is little or no correlation between the present and other extensive collections of boophilids collected from several geographical areas throughout the world, and Minning's illustrations and remarks about species collected in the same localities. Anastos (1950) has abandoned these three subgenera with the hearty concurrence of many serious colleagues.

Anastos (loc. cit.) on the other hand, would confine the known Boophilus species of the world to the three discussed herein. Al though it appears that his view is most likely correct, a pains taking study of extensive, worldwide series of specimens will be

necessary before any final judgement on all subspecies and related species may be vouchsafed.

Speciation in this genus has been extremely conservative and restricted geographical "species"" do not appear to have evolved. Many superficial "morphological variations" derive from degree of engorgement, method of preservation, or angle of examination.

Boophilids are exceptionally difficult to study taxonomically owing to superficial variability, small size, and crowding of diagnostic characters. The state of engorgement of many routinelycollected females tends to modify certain features so that they are frequently difficult to evaluate.

For discussion of the Sudan Boophilus fauna in relation to that of North Africa, southern Europe, and the Near East, see REMARKS under B. annulatus below.

[blocks in formation]

*Preserved specimens must be entirely free of surface sheen from liquid preservatives before identification can be attempted. The caudal appendage of B. decoloratus is very variable in size and the palpal basal bristle-bearing protuberance of either sex can be seen only when the mouthparts are absolutely clean; the bristles are frequently broken off. Turning the specimen at an angle to the light may be necessary to see this character as well as the groove of coxa I.

**B. microplus does not occur in the Sudan but there is some likelihood that it may reach the Sudan within a few years. The inclusion of B. microplus in this key makes it serviceable for all known species, according to contemporary concepts of the genus.

« PreviousContinue »