Twenty one species of ticks (Ixodoidea), one of which is represented by two subspecies, are recorded from the Bechuanaland Protectorate. Localities, dates and the hosts are given; general distribution and medical and veterinary importance are discussed under each species.

The shrub desert formations of the Kalahari are shown to be unsuitable habitats for most species of ticks; only a few are able to survive under severe desert conditions.

In medical respects, Ornithodoros moubata (Murr.), as the transmitter of relapsing fever, is the most important tick in the Protectorate. It has been found in the eastern part up to Francistown and in Ngamiland and near Tsane; its further distribution has not yet been established. Larvae and nymphs of various members of the Ixodidae infesting domestic and wild rodents are potential transmitters of tick-bite fever.

Cattle in the eastern area and in Ngamiland were found to be infested by ten species, of which Amblyomma hebraeum Koch, Hyalomma rufipes Koch, H. truncatum Koch, Rhipicephalus appendiculatus Neumann, R. evertsi evertsi Neumann, R. simus simus Koch and Boophilus decoloratus (Koch) are the most important ones, both in respect of the numbers infesting cattle, and of their significance as transmitters of redwater, anaplasmosis, heartwater and sweating sickness.

Sheep, goats, pigs and horses were found to be infested by nine of the species listed above as occurring on cattle.

Dogs were mainly parasitised by Rhipicephalus simus which outnumbered by far the two recognised dog-ticks, Rhipicephalus sanguineus sanguineus (Latr.) and Haemaphysalis leachii leachii (Aud.).

Wild Bovids and zebra are infested by species which also live on domestic ruminants, but the percentage of the different species present varies according to the host and to the locality.

Wild carnivores are infested by the same species as are dogs, but in this group, too, there are differences in the relative abundance of the various tick species.

Small birds are hosts of immature stages of Amblyomma and Hyalomma species. Their importance as carriers for the dispersal of cattle-infesting ticks is noticed.

Two areas in Ankole, Uganda, were studied with a view to obtaining estimates of the standard availability of Glossina morsitans Westw. These estimates gave maximum and minimum fiducial limits of 2·0 and 0·19 per cent. These are considerably lower than the estimates, obtained by Jackson in Tanganyika, of approximately 10 per cent. This difference is of practical importance in that a single fly caught in Ankole indicates a much larger population, and this is the probable explanation of the trypanosomiasis problem round the edges of the flybelt, where routine catches showed flies to be scarce.

Replicated sample plots of wattle (Acacia) were sprayed from the air with 2 oz. endrin and 1½, 2¼, 3 and 6 lb. toxaphene per acre, each in light diesel oil, to test the effect of these insecticides on the bagworm, Kotochalia junodi (Heyl.), and other wattle fauna. All invertebrates which fell from the sample trees were collected on sheets at intervals after spraying and identified. The mortality of bagworms was assessed after 10 to 14 days.

The mean corrected mortality was significantly lower in the treatment with 1½ lb. toxaphene than in the others, which, however, did not differ significantly amongst themselves. In all cases the kill was greater in the upper than in the lower parts of the tree crowns. There was no difference in the final percentage “fall-off” of bagworms in all plots, though in those treated with endrin the initial rate was higher. A very high kill, ranging from 96·6 to 98·5 per cent., was obtained in all but the 1½ lb. toxaphene plots, but even the 6 lb. application was not sufficient to reduce the bagworm population to its endemic level.

The arthropods, other than bagworms, collected on ground sheets are listed by Orders and Families and also classified into groups as beneficial, indifferent, and harmful. Nearly two-thirds of the total were found to be beneficial.

Winged and wingless individuals of Myzus persicae (Sulz.), when offered a choice between unsprayed cauliflower seedlings and seedlings sprayed with a 0·1 per cent. aqueous solution of Lissapol N (a non-ionic wetting agent), preferred Lissapol-treated plants. This effect was statistically significant.

Further experiments showed that Aphids similarly preferred treated turnip seedlings to untreated seedlings. The preference for sprayed cauliflower seedlings was also shown when an anionic, a cationic and a mixed wetting agent were used.

An account is given of the damage caused by adults and larvae of Brontispa longissima (Gestro) to the young unopened fronds of coconut palms in the British Solomon Islands. Normally, only young palms less than 10 years old are severely attacked, but this has interfered seriously with replanting programmes. Full-grown palms suffer severe damage only occasionally; reasons for this difference in susceptibility are suggested.

Earlier reports, that seedlings of Malayan type are more readily and severely attacked than those of Samoan or local origin, were confirmed. A fertiliser treatment had no effect on the growth of the palms or the amount of damage by Brontispa.

Laboratory tests showed that the deposit from a spray of 0·2 per cent. p,p′DDT was completely effective for three–four weeks, that chlordane (0·16%) became significantly less effective in the third and fourth weeks, and that dusts of DDT, alone and with BHC, showed signs of diminished efficiency in the fourth week.

In small-plot trials with sprays of DDT or chlordane, applied at various concentrations and frequencies, the effects of treatment were assessed by counts, at suitable intervals, of living and dead examples of Brontispa, by estimating damage to the youngest open frond, and by measuring the growth of seedlings. DDT at 0·1, 0·2 and 0·3 per cent. of p,p′isomer, and chlordane at 0·08, 0·16 and 0·24 per cent. gave very satisfactory control of a heavy attack of the beetle and suppression of damage. Applications at 10-day intervals were more effective than 3-weekly ones. Similar trials with dieldrin at 0·1 per cent. and DDT at 0·3 per cent. against a light attack were completely effective.

In further trials, direct comparisons were made between DDT at 0·25 and 0·025 per cent., chlordane at 0·16 per cent. and dieldrin at 0·15 per cent. applied at both fortnightly and monthly intervals. The lower concentration of DDT was much less effective than the other treatments. DDT at the higher concentration and dieldrin were equally effective when applied at fortnightly intervals, but at monthly intervals the latter was superior in control of immigrant beetles. This is attributed to its greater persistence. It is concluded that, in the formulations used in this trial, dieldrin is superior to DDT and chlordane.

Further trials with dieldrin at 0·15 per cent. showed that palms subjected to only moderate reinfestation were adequately protected by spraying every six weeks, whilst isolated areas of young palms may be left much longer, probably several months, once the initial population has been controlled. The maximum frequency, under the most adverse conditions, might vary between 2 and 4 weeks, initially. Varietal susceptibility in the coconut does not affect the efficiency of control.

Slight phytotoxicity, indicated by retardation of growth and rate of production of new fronds, was caused by frequent applications of high volumes of spray, but the volume necessary to produce such effect is considerably in excess of that required for satisfactory control. Unnecessarily high volumes and concentrations should, however, be avoided.

The spray was applied to each palm, individually, downwards on to the central spike, where the beetle lives. Equipment capable of delivering a fine, low-volume spray controlled by an efficient trigger tap will use only about 16 cc. spray per palm up to 3 years old. With a low-volume atomiser, this consumption can be reduced to about 6 cc.

An imitation aerial spray gave promising but inconclusive results.

With the proprietary formulations of insecticides used, the addition of a wetting agent was unnecessary.

Field applications were tried out in the Russell Islands on extensive areas of young palms that showed heavy beetle attack. Sprays containing dieldrin or DDT, each in two proprietary formulations, gave excellent and satisfactory results, respectively.

It is concluded that the experiments clearly indicate that very satisfactory control can be achieved at low cost, and that a programme of replanting could be safely embarked upon without fear of the severe losses, due to Brontispa, that have been suffered in the past.

A method is described of estimating the total numbers and frequency distributions of adults of the Red Locust, Nomadacris septemfasciata (Serv.), in outbreak areas of hundreds of square miles, based upon counting the numbers that fly up in a two-yard strip in front of a moving vehicle. The method has proved itself valuable for indicating both immediate and future requirements for killing the locusts, but it requires refining for some research purposes.

By this method, the importance has been clearly shown of the process of congregation of scattered adult locusts in forming emigrant swarms that could start a plague. The locusts do not congregate but actually disperse just before laying eggs.

The total population in part (189 sq. miles) of the North Rukwa Outbreak Area (a self-contained area of 253 sq. miles) in Tanganyika Territory has been followed for four years. There are indications that a small migrant swarm contains 5–10 million locusts, that a total population in the whole of the North Rukwa Outbreak Area of 20 million locusts is unlikely to yield a migrant swarm, but that 50 million locusts could readily do so.

In 1953, after poor rains, no natural mortality was detected between July and October by the assessment methods described. In 1957, after good rains, natural mortality of 70–90 per cent. was revealed by the same methods, although the dry season was not fully covered by the assessments.

A colony of Eretmapodites chrysogaster Grah., sensu stricto, was maintained successfully for over a year without any reinforcement.

Identity of the mosquitos was established by starting the colony from a single batch of eggs laid by a single wild-caught female mosquito, and subsequent examination of the genitalia of the male progeny.

Mating occurred regularly after the first blood-meal of the female. In fact the females would not accept the males until they had started, or had finished, their first blood-meal.

Eggs were laid on the sterilised, water-filled bracts of banana flowers. Moist paper, moist cotton-wool or free water above paper or cotton-wool proved unsatisfactory as egg-laying media.

Larvae fed largely on the substance of the banana bracts on which the eggs had been laid. The banana bract also provided cover and so reduced the incidence of cannibalism among larvae.

Glossina vanhoofi Henrard has been found at the I.R.S.A.C. field station at Irangi in the Belgian Congo in dense rain-forest. The fly does not normally attack man and was collected only by looking for it in its resting places. The fly rests on small saplings, head down, at an average height of about 133 cm. A three-months' survey on a fly-round transecting three valleys and two hill-tops showed that the resting density (defined as the total number of resting flies observed per 10,000 metres of path) was correlated with the profile of the transect, the hill-tops yielding more flies than the valleys. The fly-round was worked three times a day and showed the highest density during early morning in all three months; in two of them there was little difference between midday and evening catches. The resting height varied in much the same way in all the sections of the fly-round and the average height remained virtually constant during the three months of the survey. There was a slight difference between the sexes as regards average resting height, the females perching somewhat lower than the males. The sex ratio of about 1:1 was very constant throughout the day and the period of the observations.

There is some evidence which seems to indicate that this species is strongly attracted to possible host-animals by a sense of smell.

Puparia have been found in “classical” sites, but the proportion containing living pupae was small. The duration of the pupal period is about 35 days under laboratory conditions at 26°C. and 90 per cent. relative humidity.

G. vanhoofi in captivity feeds readily on the porcupine, Atherurus africanus.

Dr. W. Thalenhorst, of the Niedersächsische Forstliche Versuchsanstalt, Göttingen, Germany, sent me some time ago specimens of what he took to be an abnormally dark form of Pachynematus montanus (Zaddach). These had been reared in 1952 from larvae, not at the time distinguished from the larvae of that species and found feeding with them on spruce (Picea abies) in the Harz Mountains in the previous year. Unfortunately the female was smashed in the post and I did not like to describe a new species that would have to be based on only a few males, though I was not able to identify them with any known species. In 1955, however, he reared another female of the same species and from this he tried to obtain eggs but without any success. This female I now have before me. No further specimens have been found.

The departure of the newly emerged adults of the salt-marsh mosquito, Aëdes taeniorhynchus (Wied.) from the breeding sites was studied in Florida. The departures, which are presumed to be the initial stage of the migratory flight, have been observed to take place only in the dark period of the 24 hours, and, the vast majority of individuals being ready to take off at dusk, spontaneous mass departure took place at that time.

Samples of the resting population of mosquitos were taken at intervals before and after the mass departure, and from the departing migrants. The average age of the males in each sample was estimated by the proportion in different stages of hypopygial rotation, from which it is concluded that migratory activity begins when the insects are six or more hours old. The end of the migratory period is not yet known. In all of 21 female departing migrants examined, the ovaries were immature and the spermathecae empty.

Quantitative measurements of the sorption of γ BHC and dieldrin in Uganda mud blocks have been made. Gamma BHC diffused more rapidly than dieldrin, and within a few weeks had achieved an almost uniform concentration throughout the sprayed blocks. Only when the uniform concentration had been reached did loss by evaporation from the blocks become marked. Increased dosages of γ BHC gave increases in biological activity which were roughly proportional to the dosages used. Sorption on to mud greatly prolonged the residual life of γ BHC as compared with similar deposits on glass.

Dieldrin behaved in the same way as γ BHC although because of its slower rate of diffusion the distribution in the blocks had only reached in 48 weeks the stage reached by γ BHC in eight weeks. There was no appreciable loss of dieldrin during this time, whereas about 90 per cent. of the deposit on glass plates had been lost.

Gamma BHC, dieldrin and DDT were recovered from the adsorbed state on mud and identified. Any decomposition is therefore likely to be negligible. Dieldrin was also recovered from two soils which had much higher “surface acidities” than the standard.

Active mud can only sorb the portion of insecticide vapour from an evaporating deposit which happens to diffuse in its direction. This is to be expected, but the system has some peculiarities because the evaporation of γ BHC from filter papers over mud blocks is much faster than in the absence of the mud.

Measurements of the distribution of DDT and dieldrin in soils less active than the standard Uganda one showed that both the initial adsorption and subsequent diffusion were very much slower.

The activity of Uganda soil was not reduced by removal of material soluble in organic solvents, and was only partly reduced by complete extraction of iron compounds.

Variation in temperature over the range 20 to 30°C. had only small effects on the diffusion of DDT and dieldrin within mud blocks.

Repeated applications of DDT and dieldrin to the same blocks did not result in any observable slowing in the rate of disappearance. The concentration of insecticide in the successive layers of mud, did, of course, increase with successive sprayings.

Changes in relative humidity had a very marked influence upon the biological activities of γ BHC, dieldrin and DDT sorbed on Uganda mud blocks. In agreement with field observations, kills of mosquitos increased as the humidity increased and this effect was rapidly reversible.

Disappearance of insecticide particles from the mud surface was inversely related to humidity, the rate increasing as humidity decreased. On the other hand, the rates of diffusion of sorbed insecticide away from the surface were greater at higher humidities.

It is suggested, therefore, that when the biological activity of a mud surface is increased by increasing the humidity, the insects acquire a greater dose of insecticide not because the concentration of insecticide in the surface layers is greater but because the insecticide that is already present acquires a greater mobility. This greater mobility results in a more rapid diffusion in the mud itself away from the treated surface and a greater potential for diffusion into insects resting on the mud surface.

Support for these conclusions was obtained by showing that on transferring dieldrin-treated mud blocks from low to high humidity the change in biological activity occurred at about the same rate as the increase in water content of the blocks.

The influence of humidity upon the sorption of DDT and dieldrin on a selection of soil samples of widely differing origin was observed. Both insecticides disappeared from the surface more rapidly at low than at high humidity on all the soils.

In laboratory cultures of Wheat Bulb Fly, Leptohylemyia coarctata (Fall.), a daily oviposition rhythm was observed in which egg-laying was virtually restricted to the afternoon and evening with maximum laying occurring in the two hours before nightfall. The time of oviposition coincided with that part of the diurnal flight rhythm, earlier observed, in which the flies actively congregated on wheat and this, it is suggested, could account for the fact, already recorded, that laying has been found to occur mostly on sites close to an infested crop.

The oviposition rhythm was maintained for 24 hours in absence of light and therefore appeared to be partly inherent. However, it could be influenced by the times of exposure to light and disappeared in constant light. Darkness did not appear to affect the egg-laying rate but a temporary increase followed exposure to continuous light. Within the course of the experiments the rate was not affected by small changes in temperature.

The individual fly laid up to 180 eggs in the laboratory in periodic batches of up to 42 eggs laid over periods of 1 to 6 days. This periodicity was obscured in cages containing a number of flies. Disproportionately small decreases in the mean daily laying rate occurred with increases in this laying period. Within the laying period the rate progressively increased with each successive day. The total number of eggs laid was not related to the number of ovarioles. In the laboratory, the rate of laying increased with age and most of the eggs were laid by relatively few flies.

The rate of egg-laying and survival at different stages in the field is discussed and it is suggested that about two per cent. of the eggs successfully develop as matured females which lay an average of about 50 eggs each.

The Lepidopterous stalk borers that occur in Uganda in association with the Gramineae were studied there during 1954–1956 by collecting on all likely host-plants at two centres and by a country-wide survey in which stalk-borer damage in cereal crops was qualitatively assessed at five-mile intervals along the routes followed, and the species of borer present in such crops and, where possible, in nearby wild host-plants were determined. The commonest Noctuids were Busseola fusca (Fuller), B. segeta Bowden, Sesamia calamistis Hmps. and S. poephaga Tanas & Bowden. All these attacked sorghum, maize, sugar-cane and (except the last) finger millet (Eleusine coracana.); so also did S. botanephaga Tarns & Bowden, but only near swamps, in which it infested sedges (Cyperus spp.) and reeds (Typha australis), from which the other species were virtually absent. Only S. calamistis and S. botanephaga attacked rice. All attacked Pennisetum purpureum, Sorghum vertictlliflorum, Vossia cuspidata, and (except S. botanephaga) Panicum maximum, and also other wild grasses.

B. fusca is widely distributed but most abundant in areas of intensive cultivation, where crop residues abound in which the resting larvae can survive the dry season. B. segeta is the most frequent species in Pennisetum purpureum and Panicum maximum, which are extremely common over most of the country, but is rare in cereal crops. S. calamistis (to which earlier records of S. cretica (Led.) and S. vuteria (Stoll) must be attributed) is not numerous but occurs in every district except Karamoja, where it cannot survive the dry season; and S. poephaga is known only from northern and eastern districts and is unimportant.

Chilo zonellus (Swinh.), which may be a recent introduction, occurs in all the cultivated host-plants and most of the wild ones except Cyperus and Typha; it has not been found at altitudes above 4,000 ft. in the west or 5,000 ft. in the north and east, but elsewhere it is the prevalent borer and can cause severe damage in dry years and on out-of-season crops. It was the only species besides B. fusca found on bulrush millet (Pennisetum typhoides), the tough stem of which resists attack. On the western border, Eldana saccharina Wlk. attacks sorghum, maize and sugar-cane at high altitudes, and Maliarpha separatella Rag. attacks rice. A fourth Pyralid, Pectinigeria sp., occurs on maize.

When small plots of host-plants were grown in a matrix of sorghum, and also in a swamp, and the whole sampled at harvest for borer infestation, all the cultivated hosts and many of the wild ones suffered some attack, the percentage of stems bored varying from 10 (finger millet) to 89 (sorghum) amongst the former, and reaching 34 (Panicum maximum), 40 (Sorghum verticilliflorum) and 50 (Pennisetum purpureum) amongst the latter. Immature stages of C. zonellus and B. fusca greatly outnumbered those of Sesamia, especially in the more heavily infested host-plants.

Notes are given on the life-histories of the commoner species of borer and on their habits in the field. In the laboratory, the lengths of the life-cycles, in days, were 68–75 (B. fusca), 65–78 (B. segeta), 46–58 (S. calamistis) and 46–53 (C. zonellus). In the dry season, the larvae of B. fusca entered a resting stage, which prolonged the life-cycle to 200 days; such larvae were found only in living or dry stems of crop plants. C. zonellus and Sesamia spp. bred continuously, in the dry season the former being found chiefly in trash, stubble and volunteer tillers of sorghum, the latter in these and living stems of grasses.

Of the principal cereal crops in Uganda, sorghum is the most widespread. The main crop, sown after the longer of the two dry seasons, suffers little borer attack; second crops are more severely affected, but plants with thick stems or numerous tillers nevertheless yield heavily. Finger millet is the staple food crop in the north and west; borer damage is negligible and restricted to small patches of “dead-hearts” caused by larvae from single egg-masses of S. calamistis. Maize is grown on a large scale in the districts bordering Lake Victoria and in the highlands; borer attack is usually very late and, where rainfall is adequate, appears not to afiect yields.

Apanteles sesamiae Cam. and another, unidentified, Braconid probably control S. calamistis, but on the other stalk borers the incidence of parasites, which are listed, is low. Destruction of all crop residues and wild species of Sorghum around cultivated areas would considerably reduce borer attack at the beginning of the growing season, but chemical control was only partly effective and did not increase the yield.

Information on the world distribution and host-plants of the Groundnut Bruchid, Caryedon gonagra (F.), has been summarised from the literature. As a result of misidentification of the species that attacks groundnuts and of differing views about its generic assignment, this information has been given under several different names. The records brought together here are believed all to represent C. gonagra, and in a number of cases this has been confirmed by examination of the material concerned by Mr. B. J. Southgate.

C. gonagra is widely distributed in the Old World tropics and sub-tropics, but it is absent from Australasia, and it has only a restricted distribution in the New World tropics. Almost all its host-plants belong to the Leguminosae, the principal one being the tamarind, Tamarindus indica, in the pod of which the beetle has been found to develop more quickly than in the groundnut.

Data on the life-history and habits, and on the duration of pre-adult development and adult life, are summarised from the literature.

Experiments are described to determine the optimum conditions for multiplication of C. gonagra, using groundnuts as food. When adult females were allowed to lay large numbers of eggs on shelled and unshelled nuts, only a small proportion of the resulting larvae completed their development, the number of adults that emerged averaging about 2·4 per kernel in shelled nuts and 3·2 in unshelled ones. The developmental period at 70 per cent. relative humidity was 42 days at 30°C. and 91–98 at 25°C.; the former figure is less than any recorded in the literature at higher or lower temperatures, and all subsequent experiments were therefore made at 30°C. and 70 per cent. relative humidity.

Adults confined for three weeks, starting when four days old, at the rate of 25 pairs on 160 g. of a mixture of broken and intact kernels gave rise to some 314 F1 adults; this total was virtually unchanged when 50 pairs were used, but lower densities, though giving rise to greater yields per parent adult, gave much lower yields per weight of food. Emergence of adults began six weeks after the date of egg-laying and reached its peak from one to three weeks later.

The yield from ten females on intact kernels was greater than from the same number on the mixture, but differed little whether the parent adults were left on for one week or three weeks, indicating that the majority of the eggs are laid in the first 11 days of adult life. The yield from unshelled nuts was nearly twice as great as that from shelled nuts, and also significantly larger than that from shelled nuts with ground shell added. Possible causes of this are discussed.

The sexes can be distinguished in the adult stage by differences in the terminal abdominal segments.

The Onion Fly (Delia antiqua (Mg.)) was bred at Wye, Kent, under insectary and laboratory conditions to obtain further information on its biology and reactions to various temperatures.

A comparison of the times of emergence of overwintering generations of Onion Fly and Cabbage Root Fly (Erioischia brassicae (Bch.)) in an insectary showed that the former emerged consistently about a month later than the latter. This supported the observations of previous workers that the Onion Fly was not active in the field until late May.

A diet containing protein was necessary for oviposition. The length of the preoviposition period was affected by temperature. Flies maintained at 25°C. laid eggs in 10–24 days, with an average of 15 days. At spring and summer laboratory temperatures (12–29°C.) the preoviposition period was 10–25 days, with an average of 15 days; and in autumn and winter (11–20°) it was 11–46 days with an average of 21 days. Flies maintained at 6–8° did not lay eggs.

Flies in captivity laid up to 123 eggs at the rate of 1–45 per day. Intervals between batches of eggs varied from 1–9 days, and the oviposition period was 7–25 days. Flies lived up to 6 days after oviposition.

The incubation period depended on the temperature. Eggs at 25°C. hatched in 2 days; at 20° in 3–4 days; at 15° in 4–6 days; and at 7–10° in 9–14 days.

The temperature also affected the duration of larval and pupal stages. At 25°C. the successive larval stadia required 2, 2 and 5–9 days, respectively. Lowering the temperature increased the time for development until at 9–11° the three larval stadia required 8–12, 8–18 and 24–37 days, respectively. At 25° the pupal stage lasted 12–17 days; at 20° it was 16–25 days, and at 15° it was from 35 days to over a year. At 25–30° the development from egg to adult was completed in 25 days; at 25° it required 28 days; at 22–27°, 30 days; at 19–24°, 33 days.

At 25°C. the Onion Fly bred continuously without diapause. When larvae were reared at temperatures below about 18° pupal development was often retarded. Pupae formed from larvae reared at 12–18° and maintained at approximately that temperature, required 94–442 days to complete their development. By raising the temperature of pupae formed from larvae reared below 18°, it was demonstrated that a true diapause had been induced. Of 54 pupae raised to 25°, 8 (15%) completed their development in the expected time (13–16 days) and 46 (85%) required 94–208 days. Of 322 pupae formed from larvae reared in an insectary in May and June at 10–18° and exposed to July temperatures of 13–20°, 37 (11%) emerged in 25–35 days and 252 (78%) required 234–294 days. Similarly, of 283 pupae formed from larvae reared at 12–21° and exposed to a temperature of 15–23°, 30 (11%) completed their development in 21–31 days while 253 (89%) required 118–341 days. Exposure to low temperatures was not necessary to terminate pupal diapause.