Southeastern Uganda Research Articles

Calzirtite and the mineralogy of residual soils from the Bukusu carbonatite complex, south-eastern Uganda

SummaryCalzirtite, essentially CaTiZr3O9, has been identified in residual soils from the Bukusu carbonatite complex in Uganda. A satisfactory ultrasonic technique was developed for cleaning the samples prior to studying their mineralogy. Other heavy minerals present include ilmenite, perovskite, melanite, apatite, zircon, and baddeleyite. The properties and composition of calzirtite are compared with the available data from occurrences in the U.S.S.R. The mineral has a metasomatic paragenesis and probably indicates the presence of carbonatized rocks at depth.

Studies of the sampling of Glossina pallidipes Aust. IV.—Some aspects of the use of Morris traps

Experiments carried out in south-eastern Uganda, as part of a series of investigations of factors affecting the catch of Glossina pallidipes Aust. by Morris traps, showed that this was not significantly affected by varying the interval between emptying the traps within the range 1½-24 hours or by varying the width of the entrance slit from ¼ to 1½ inches. Such exceptions as occurred could be attributed to unexplained variations in the intrinsic performance of individual traps. Almost no flies were trapped at night (1830–0630 hr.).Catches in traps with simulated defects (leaving the sleeve open or making holes in the cage gauze) were lower than in perfect traps; the catch was not significantly affected by the diameter of the sleeve opening, but was significantly lower in traps with 16 ½-in. holes in the cage gauze as against those with 2, 4 or 8. Escapes through such holes were observed whilst emptying the traps, when the recorder's approach disturbed the trapped flies, which were otherwise inactive. Frequent visits to the traps to empty them did not materially increase the number of flies effectively trapped, as might have been expected were flies escaping continuously or were the traps to catch flies accompanying the observer.When the interval between emptying traps exceeded 24 hr., losses of trapped flies occurred, to an extent that is unknown but sometimes substantial, as a result of predation by ants; this is the most likely source of significant variation in catches made by apparently identical traps, and can be overcome by mounting traps on greased, single legs. When thus protected, there was no significant difference in catch between traps cleared at intervals ranging from 12 hr. to eight days. The longer this interval, the greater the proportion of dead amongst captured flies; the median length of life after capture was about two days, this period varying slightly with sex and more substantially with undefined differences between sites and trapping periods.

Studies of the sampling of Glossina pallidipes Aust. III.—The hunger stages of male flies caught on cattle and in Morris traps

When non-teneral male flies of Glossina pallidipes Aust. were caught concurrently on oxen and in Morris traps in two experiments in south-eastern Uganda and classified, within 1½ hr. of capture, according to a modification of the hunger-stage categories described by Jackson, individual recorders were found to differ markedly in their assessments. No conclusions regarding the hunger stage of flies taken by different attractants could therefore be drawn from the first experiment, but in the second, which was so designed as to discount possible bias amongst recorders, the proportions of ‘hungry ’ (stage III + IV) flies in catches of males were similar on variously coloured individual oxen, and generally higher than in trap catches, in which the proportions varied widely. As all the traps appeared identical, no generalisation is possible about the mechanism by which non-teneral male flies are attracted to and induced to enter such traps.

Studies of the sampling of Glossina pallidipes Aust. I.—The numbers caught daily on cattle, in Morris traps and on a fly-round

Two experiments in which G. pallidipes Aust. was caught on oxen, in Morris traps and on a fly-round in south-eastern Uganda are described.Fewer flies were caught in traps than on oxen, but the former took a higher proportion of females. The numbers in traps covered with natural-coloured hessian tended to be greater than in traps on which the hessian was painted black. A white ox attracted fewer flies than darker-coloured oxen, among which a red ox was the most attractive. Variations reflected in day and site effects indicated that the sexes were differentially affected by the factors controlling availability to the oxen and the traps. Fly-round data appeared to give an unsatisfactory estimate of the population density.The numbers caught by the various methods were, in general, not correlated and this casts doubt on the validity of fly-round or trap data as estimates of the number of G. pallidipes likely to attack cattle.

VARIATION IN THE AFRICAN BLACK TITS, PARUS NIGER AND PARUS LEUCOMELAS

SUMMARY1. The relationship between the Black and Grey Tits of Africa is discussed briefly.2. Variable characters in the Black Tit are listed, on which five forms can be distinguished.3. The characters, ranges and ecology of the five forms are set out, with some discussion on atypical populations within the forms, and on the variable population of central and southeastern Uganda.4. It is concluded that speciation is taking place in many populations of Black Tits and that this presents considerable difficulties in assessing the relationship between forms.5. Reasons are given for considering P. n. niger and P. n. carpi as specifically distinct from other forms. The question of whether guineensis should be considered specifically distinct from P. I. leucomelas and P. I. insignis is left open until more is known of their field characters in Uganda and Abyssinia. Similarly purpurascens is regarded as a variable race until more field study has been done.