The distribution of 29 species and three varieties of Anopheles in the Sudan is shown on maps. Notes are given on each one with particular reference to distribution. Reasons are given for regarding A. rupicolus Lewis as a synonym or local form of A. rhodesiensis Theo. The former spread of A. gambiae Giles into the Palaearctic Region in Egypt is discussed, and notes are given on its distribution in the Wadi Halfa area.

The general distribution of the Sudan Anophelines is discussed.

Notes are given on malaria and on Wuchereria bancrofti.

Difficulty is being experienced in obtaining natural regeneration of Juniperus procera in the Daloh Forest, Erigavo, British Somaliland due to infection of the seed by an unidentified species of Megastigmus. In 1953, Mr. A. R. Tribe succeeded in breeding specimens from infested seed, and this material, together with a subsequent collection by Mr. J. J. Lawrie in January 1954, has been used as the basis of the following description.

Field and laboratory studies on the rôle of oxygen concentration and speed of current on larvae of Simulium ornatum Mg. show that current speed is more important than oxygen concentration in governing their distribution.

The larvae prefer waters with a velocity range of 50 to 120 cm./sec., the greatest numbers occurring between 80 and 90 cm./sec.

Larvae move independently of oxygen in concentrations above 50 per cent, saturation level.

The biology and general ecology of Melittomma insulare Fairm. in the Seychelles is briefly described and the difficulties in the biological control of this pest are stressed.

As much information as possible was obtained concerning the species of the little-known family Lymexylonidae, particularly with regard to their biology, which in most cases has not been investigated. Several species might warrant further investigation with a view to providing natural enemies for use against M. insulare, but in general what is known of their biology does not afford much hope that an effective parasite or predator will be found.

The biology of Atractocerus brasiliensis Lep. & Serv. was investigated in detail in Trinidad but no natural enemy was found.

The only possibility is that Rhizophagus dispar (Payk.), recorded as attacking Hylecoetus dermestoides (L.) in England, might also attack the eggs of M. insulare.

A systematic review of some species of the Coccid genus Saissetia occurring in East Africa led to the rediscovery of two species—S. persimilis (Newst.) and S. somereni (Newst.)—which although of economic importance have been almost completely neglected since they were first described. Both are redescribed in this paper. One new species recently collected in Kenya is described; this is S. pterolobina.

Seven species are dealt with in the paper, including the important and widely distributed S. oleae (Bern.). A provisional key for their separation is included, while one species—S. cuneiformis Leonardi—is sunk as a synonym of S. nigra (Nietn.).

Early last year five females of a species of Eupelmid were received from Mr. B. A. O'Connor of the Department of Agriculture in Fiji, where they had been bred in the previous November from eggs of the Phasmid, Graeffea crouanii (Le Guillou). Although this Phasmid, which is a pest of the coconut crowns, bad been bred many times before, no such parasite had occurred previously. As this species was unknown to the author, more material was requested.

In connection with studies on the control of tsetse flies (Glossina spp.) by insecticides, an investigation was made in Tanganyika Territory of the influence of a number of factors on the distribution of insecticide in woodland and open country. A solution of DDT in oil was disseminated as a coarse aerosol from an aircraft and its behaviour traced by the mortality suffered by caged flies. The test insects were wild-caught Musca (Eumusca) lusoria Wied., which proved more susceptible to the insecticide used than did Glossina. palpalis fuscipes Newst.

In open country, complete kills were obtained with the standard application rate (defined as one run using 10 gals, per minute of a 10 per cent, solution of DDT) for at least three hundred yds. downwind of the line of emission, in all the atmospheric conditions encountered.

Tests of the possibility of treating very thin woodland in comparatively high winds (for aerial dispersals of aerosols) and slightly unstable conditions were spoilt by variations in the emission rate of the insecticide, but it was shown that quite small numbers of twigs upwind provided a considerable degree of protection to the test insects and that the kills in cages completely exposed on the upwind side of trees were considerably less than at corresponding distances downwind in completely open country. There was evidence that in high winds and slightly unstable conditions, penetration through the trees was better than with moderate winds and small inversions, but in both conditions there was mortality behind obstacles.

Preliminary comparisons between the kill in the open and in continuous woodland composed of Acacia xanthophloea showed that in the latter mortality was greatly reduced and did not approach that frequently obtained in practical large-scale experiments in tsetse control. A search was made for factors which would increase the level of mortality.

Increased atmospheric stability caused greater average mortality at the expense of evenness of kill. This was not due solely to decreasing effective swathe width due to lighter winds.

Large natural openings in the canopy assisted the penetration of insecticide in unstable conditions, but in stable air the kill around and downwind of clearings was reduced compared with kills in unbroken woodland.

The principal factor in raising mortality to a generally high level was the summation of sublethal doses due to drifting downwind of the fringes of successive parallel swathes. The highest kill obtained in any of these trials was from summation of three swathes emitted 75 yds. apart, which produced a mean mortality of 84 per cent, for 75 yds. downwind of the third run.

An attempt to cover the whole area of woodland by emitting insecticide in a series of parallel runs, as in actual control procedure, showed that in conditions of low turbulence there yet may be great unevenness in the kill obtained. Mortality varied between 21 and 100 per cent., and this irregularity was almost certainly due to the fact that during each of the runs the wind was almost directly along the aircraft track. Such contingencies are unavoidable, for unsteadiness of wind direction is a constant feature of the stable, non-turbulent conditions in the free air that are needed to permit any substantial kill within continuous woodland.

The relation between these results and those obtained in practical control experiments is discussed. It is concluded that the use of caged insects and a particular type of woodland probably accounts for the comparatively low kills obtained in this investigation, from which, nevertheless, valid conclusions can be drawn concerning the variation in mortality from place to place.

Forty five species, two subspecies and one variety of Culex occur in the Sudan.

Taxonomic notes are given on a few species, and new localities, mainly for the subgenus Culex, are recorded. The known distribution of all species of this subgenus is shown on maps.

Several aspects of distribution are discussed, and there is a short section on practical importance.

The results of a general mosquito survey of the Liberian hinterland are presented together with the findings of previous workers in this country.

Liberia is almost entirely in the Upper Guinean Forest region with an annual rainfall from over 140 in. on the coast to about 80 in. in the hinterland.

A list is given of all species recorded from Liberia.

A brief account is given of the distribution, bionomics and relation to malaria of the Anophelini, with some taxonomie notes. Thirteen species or forms of Anophelines are listed, of which ten were found in the hinterland as well as on the coast.

A summary of the distribution and bionomics of the Megarhinini and Culicini of Liberia is given, with the writer's field notes and those of earlier workers, and some taxonomic notes. Seventy one or 72 species or forms are included, of which 59 were found in the hinterland. If the first mention of some species in the two previous papers in this series be included, 41 additions to the Liberian list, three of them new species, have been made.

The need having arisen for a small, conveniently situated warm room for the maintenance of mosquitos in a constant environment, the cabinet described below was constructed by the authors at a relatively small cost, and set up in a laboratory-class room (35 ft. x 45 ft.). The warm room, being detached and moveable. entailed no structural alterations or installations.

One hundred and fifty six species, two subspecies and seven varieties of Culicidae are known to occur in the Sudan. The present paper shows the known distribution of members of the genera Dixa, Chaoborus, Toxorhynchites, Harpa-gomyia, Hodgesia, Uranotaenia, Aëdomyia, Theobaldia, Ficalbia, Taeniorhynchus and Eretmapodites, and includes taxonomic and other notes on several species.

Some aspects of distribution are discussed, particularly the exchange of species between the Ethiopian and Palaearctic Regions in which movement has been mainly from the latter to the former.

Brief notes are given on the practical importance of some species.

Keys are provided for the larvae of 32 species of TINEIDAE, and detailed descriptions are given of 31 species. These include most of the species known to be of any economic importance. What is known of the biology of each is briefly summarised, but no attempt has been made to collate the available information on control measures.

No larvae have been available of four species of some economic importance nor of twelve others of doubtful status as pests. The literature on each of these species is noted.

The larvae of a few species of no known economic importance are described and are included in the keys. Most of these are very closely related to species known to be pests.

The keys and descriptions include 21 species which are indigenous to Britain or are established here, so that keys and descriptions are now provided for half of the British species of Tineidae.

Field tests were conducted on Soutra Hill (1,100 ft. above M.S.L.) in the winters of 1953–4 and 1954–5 to find a suitable larvicide for controlling Culicoides impunctatus Goetgh. In one trial, four formulations (wettable powder, water-miscible concentrate, oil solution and dust) of DDT and γ BHC were applied to plots (10 × 10 yd.) at dosages of 3, 12, 50 and 200 mg. p.p′DDT or γ BHC/sq. ft., except for the γ BHC dust which was applied at 3, 6, 12 and 25 mg. γ BHC/sq. ft. In a second trial, the larvicidal properties of aldrin, dieldrin and malathion wettable powders, chlordane water-miscible concentrate and malathion emulsi-fiable liquid were investigated at three or four of the following dosages —3, 6, 12. 25 and 50 mg./sq. ft. The conclusions to be drawn from these trials were:—

1. DDT was superior to γ BHC at all dosages and in all formulations both in immediate and residual effects.

2. For immediate larval control, DDT and γ BHC wettable powders and DDT water-miscible concentrate were effective but γ BHC water-miscible concentrate was relatively ineffective.

3. Although all the DDT preparations were effective as residual larvicides, the wettable powder was the most successful.

4. For immediate larval control a dosage of 200 mg. p, p′DDT or γ BHC is required. The effect produced by 50 mg./sq. ft. is variable.

5. For residual larvicidal action a dosage of 50 mg./sq. ft. is required although 12 mg./sq. ft. may sometimes be effective.

6. Both preparations of malathion reduced the initial larval density by just over half but they had no residual effect.

7. Chlordane and aldrin achieved an immediate larval reduction of one third but whereas chlordane had a greater residual effect, aldrin was ineffective.

8. Dieldrin had very little immediate (20 per cent. control) but considerable residual effect (72 per cent. control).

9. Wettable powders are the most successful larvicidal preparations.

10. DDT and γ BHC wettable powders at 50 mg. p, p′DDT or γ BHC/sq. ft. are superior to chlordane at the same dosage and slightly better than dieldrin at 25 mg./sq. ft.

The distribution of the Sudan HALTICINAE is given, together with brief notes on the food-plants and habits where known, and a key to the species.

Some 39 species, within 19 genera, are known to occur. Many are of minor economic importance, but three can be ranked as major pests. These are the two cotton flea-beetles, Podagrica puncticollis Weise and P. pallida (Jacoby), and Phyllotreta cheiranthi Weise on cruciferous vegetables.

In order to estimate the effect of cracks in floors upon the oviposition rate of Calandra granaria (L.) in an unstocked granary, grain was presented to adults in six ways. The grain was either fixed or loose. Fixation was achieved either by placing grain in cracks in wood or plaster of Paris, or by gumming (in rows or scattered) to glass. The loose grains lay upon glass or plaster of Paris.

A significantly greater number of eggs was laid upon grain that was fixed. The fact that the grains were in rows and partially enclosed when in cracks had no greater effect than fixing with gum. There was no significant departure from a random distribution of eggs in grains when the latter were in cracks.

Schizonycha larvae, of a species that cannot yet be named with certainty, are a serious pest of “lubia” (Dolichos lablab) and “dura” (Sorghum vulgare) in the Sudan Gezira. Damage from these grubs has seriously reduced lubia yields at the Gezira Research Farm during the 1946–52 seasons. Soil application of BHC, at rates between 10 and 40 gm. γ isomer per feddan (1·038 acre) give excellent control of this pest on lubia. Application with the seed at the time of sowing (in effect, by drilling) is, in general, more effective than broadcasting or applying the insecticide along the ridges. Seed dressings appear to be ineffective for control, with lubia.

Population estimates show that γ BHC does not kill Schizonycha larvae but repels them or prevents feeding. The larvae occur in the soil to a maximum depth of 60 cm., and are concentrated around the plant roots. The mean depth varies with time of year, and probably with type of plant, between 15 and 30 cm. The mean depth of the pupa is 15 cm.; this does not appear to be influenced by BHC.

Larvae are widely distributed in the Gezira but are most abundant in the South and Centre Groups of the Scheme. There is evidence that, where chafer larvae and termites are associated with groundnuts, the chafer larvae are responsible for initiating damage while the termites are secondary invaders. The beneficial effect of a good lubia crop (resulting from BHC application) is reflected in the cotton crop two years later.

It is known that the females of some species of parasites can distinguish hosts that have already been parasitised and refrain from ovipositing in them. A study was made of the extent to which Spalangia drosophilae Ashm. avoids superparasitism of the puparia of Drosophila melanogaster Mg. by means of these two steps, which are termed discrimination and restraint, respectively.

Host puparia 0–24 hours old were stuck on paper, with water, equidistant ¼ in. from each other and placed in 4½ in. × 1 in. glass vials into which females of Spalangia were introduced for different periods. A series of experiments was set up, in which 25, 10 and 5 puparia were exposed to attack by 1 unmated or 1, 2 and 5 mated parasites for 24, 48 and 72 hours. In this way a wide range was obtained of the parasite-host (P/H) ratio, computed as the ratio of the number of female parasites, multiplied by the number of 24-hour periods for which they were used, to the number of host puparia exposed. Each treatment was replicated ten times, thus entailing a total of 360 experiments. The sequence of events associated with oviposition consisted of examination of the puparium by the females, stinging, followed sometimes by feeding on the fluid that exuded, and finally, but not invariably, oviposition. At the end of the experiment each puparium was examined and the number of eggs present, or the occurrence of stinging only, was recorded. The chance of a puparium being attacked was unaffected by its position on the paper and there was no significant difference between the total number of eggs that virgin and mated females laid under the same conditions.

The results were assessed by comparing the observed distribution of parasite eggs amongst host puparia with the probable random distribution calculated from a formula that is given. The divergence between these distributions was greatest at the lower P/H values, and very little superparasitism occurred unless these exceeded 3/25, at which point total parasitism reached about 60–70 per cent. As the P/H value increased, so did the total parasitism and the degree of superparasitism, and the deviation of the observed from the random distribution of eggs diminished, although even amongst experiments in which parasitism reached 91–100 per cent., superparasitism was still avoided in 15·6 per cent, of them.

The degree to which females of Spalangia can restrain themselves from ovipositing in hosts that have been parasitised was estimated by plotting the percentage of experiments in which restraint was observed to break down, against the level of attack, and comparing the distribution of the points so obtained with the curves that would relate these two functions if the power of restraint was to break down when the female was confronted with 2, 3 or 4 successive puparia that had already been attacked. It is concluded that the assumption that restraint breaks down at about the third successive unsuitable encounter gives the best fit with the observed data.

Contributory evidence that females of Spalangia can distinguish parasitised hosts was obtained by direct observation of their behaviour, which indicated that, on the average, females took about 3½ minutes to examine an unparasitised host before deciding whether to attack or not, but, in the case of hosts already parasitised, either rejected them in half that time, or only accepted them after unduly prolonged examination.

When individual mated females were supplied daily for 16 days with a single puparium, then for 3 days with 25 puparia, then again for 8 days with a single puparium and finally for 8 days with 25 puparia, the number of eggs laid daily was restricted to less than two when only a single host was available, but rose to about 9–11 on the first day an excess of hosts was provided and then fell to a normal output. The females thus adapt their egg-laying to some extent to the number of hosts available.

It was hoped that this elucidation of the combination of perfect discrimination but imperfect restraint exhibited by Spalangia. when ovipositing, together with the data previously obtained on its biology, would make it possible to predict the fluctuations of a population of Spalangia in the field and its effect on the natural host, Oscinella frit (L.), but the factors involved, and their interactions, are too complex, particularly when weather effects are considered, and it is concluded that any predictions of population must be deduced empirically from field observations over a number of years.

Hands of warm-skinned Caucasian individuals were significantly more attractive to Aëdes aegypti (L.) than cool-skinned individuals. An artificially cooled hand is very much less attractive than a normal one.

Hands of Negroes were significantly more attractive than those of Orientals, and both were significantly more attractive than those of Caucasians. Hands of dark-skinned Caucasians were significantly more attractive than those of light-skinned Caucasians.

Warmer skins were more attractive even if combined with a lighter skin hue, in Caucasian subjects. Thus skin hue is secondary to skin temperature in deciding the attractiveness of Caucasians.

Hands of individuals with low moisture output were significantly more attractive than those of high moisture output. A hand induced to perspire freely was significantly less attractive than the normal hand.

Independent discoveries of an Aphid attacking the roots of rice and other Gramineae in different parts of the world have led to its description under different names, and its affinity with other species has sometimes resulted in its confusion with them. The literature relating to the species is reviewed and it is shown that the correct name for it is Rhopalosiphum rufiabdominalis (Sasaki), of which Prunus is the primary host.

What is believed to be a reasonably complete synonymy is given and this involves the sinking of the two genera Yamataphis Matsumura and Aresha Mordvilko as synonyms of Rhopalosiphum Koch because both of these genera were erected with the Rice Root Aphid as type. A species that was described as Yamataphis rhodesiensis Hall differs in too many respects to permit its inclusion in Rhopalosiphum and a new genus, Hallaphis, is erected for its reception.

Immature nutfall, caused by the Coreid, Amblypelta cocophaga China, was prevalent in the coconut plantations of the British Solomon Islands before the late war, and was increasing in extent and intensity. Good crops were borne by palms inhabited by colonies of Oecophylla smaragdina (F.), as this ant destroyed Amblypelta; and the same was true, to a lesser extent, of another ant, Anoplolepis longipes (Jerd.). The smaller species, Pheidole megacephala (F.) and Iridomyrmex myrmecodiae Emery, did not destroy Amblypelta and consequently palms bearing these species suffered from nutfall. These non-beneficial ants were extending their areas of occupation and becoming dominant in the plantations of the Protectorate.

Attempts to control Amblypelta by introducing parasites from Indonesia, Queensland and Fiji have all proved ineffective, and so also have past efforts to change the balance of ant populations in the plantations in favour of the beneficial species.

After the war, it was noticed that certain plantations in Guadalcanal, which had suffered severely from nutfall for several years, were recovering and bearing well. In 1948, it was found that this recovery was correlated with changes in the ant populations, Oecophylla having occupied much of the area, displacing Pheidole, which had previously been dominant. The investigators concluded that this was due to ecological changes in the. plantation undergrowth, resulting from neglect of cleaning and brushing during the war.

The present paper deals with a re-examination of the position in 1952–53. The author found a further improvement in the yield and an extension of the area of recovery on the plantation in question; Pheidole had completely disappeared, but in many parts Oecophylla had been driven back by Anoplolepis, which had now become the dominant ant. The only nutfall areas that remained here were occupied by Iridomyrmex.

A fuller examination of these and other plantations did not support the theory that nutfall recovery was due to ecological changes in the undergrowth, for these had occurred everywhere in the Protectorate during the war, yet on most other plantations yields had decreased, and Pheidole had greatly extended its pre-war area of occupation. The areas in which recovery had occurred were adjacent to wartime military installations that had been subject to regular weekly anti-malarial spraying from the air, and it is suggested that this had affected Amblypelta, both directly, and indirectly by having differentially affected the populations of Pheidole and Oecophylla. It seemed more likely that it had been caused by the long-sustained spraying programme carried out by the United States forces during and after the war.

Small-scale tests carried out with insecticidal sprays confirmed this theory: the harmful species, Pheidole and Iridomyrmex, were found to be very severely affected, while the beneficial ones, Oecophylla and Anoplolepis, suffered far less. In plots with mixed ant populations it was found possible to increase temporarily the number of palms occupied by beneficial species by spraying the palm-bases with insecticide. With the equipment available it was not possible to spray the boles and crowns: consequently, these trees were often reoccupied later by the harmful species Iridomyrmex from colonies in the crowns.

The sprays were also found to be fatal to Coreid bugs, both on contact and for a considerable residual period.