The behaviour of Anopheles gambiae Giles and A. funestus Giles was studied under natural conditions in a lowland area of Tanganyika.

Studies on the outside resting population were carried out by direct searching for natural resting sites, and by the use of artificial box shelters partly buried in the ground in shaded localities. Catches in these give a valid sample when set up at some distance from houses.

Fed and gravid females comprised 67 per cent. of the outside resting gambiae population, the latter group being between 12 and 4·5 times as numerous as the former. Rather less than half the funestus females caught were unfed, the remainder of the population being mainly composed of gravid females.

Precipitin tests on the small numbers of fed females caught outside were nearly all positive for man.

The identification of gravid funestus females was confirmed by periodic examination of the eggs.

Entry of females into outside shelters did not occur solely in the period around sunrise. An appreciable number of funestus females did not enter before 07.00 hours and this was particularly so in shaded shelters.

The building of a hut in the vicinity of a box shelter caused a drastic reduction in the numbers of mosquitos resting in the latter.

Outside biting activity in these two species is of negligible importance as a source of females resting outside.

The larva of Apomecyna binunila Pasc. is a stem-borer of cucurbits in South Africa and the Sudan. In the latter country its known distribution lies between the 12° and 20° parallels of latitude. A description of the morphology of adult, larve and pupa is given. Observations on the life-history reveal a very short development period of approximately 35 days from oviposition to adult emergence. The host range is restricted to sweer and water melon. Damage is only serious where larval populations are high and the vascular tissues are destroyed. With smaller infestations (two to three larvae per 10 cm. of stem) vascular continuity is not seriously interrupted. Reference is made to Iphiaulax sp. (BRACONIDAE), the first record of a parasite from this beetle. The larva is parasitic on larvae of Apomecyna.

Measurements of the Horizontal Equivalent Area (HEA) of flying locusts and the toxic efficiency of Mk. IV DNC solution, as a function of spray droplet size, have been made using Schistocerca gregaria (Forsk.) flying “ naturally ” in a wind tunnel. The experimental conditions, including visual stimuli, for “ natural ” flight were determined by means of a flight balance. The observed values of locust airspeed varied from 2·5 to 6·5 metres per second with a mean value of about 3·2 metres per second.

A series of field observations and rearing experiments were carrried out in Florida to gain information on the duration of the larval stage and the time of day of pupation and emergence of the salt-marsh mosquito, Aëdes taeniorhynchus (Wied.).

The technique adopted in a series of experiments is described.

It was found that the duration of the larvel stage is dependent on several factors of which water temperature is probably the main factor. Hunger was also shown to be important either through lack of food or overcrowding. Larvae which later became male adults pupated before those which became female imagines.

The period of maximum pupation is determined by the distribution of light and darkness, 83 per cent. of all pupation taking place during the evening periods, 15 to 24 hours after experimental midnight, and 48 per cent. in the period just after sunset, 18 to 21 after experimental midnight. The tendency to pupate around sunset is thought to have just as much accelerating as retarding effect on the larval development.

Temperature is considered to be the only factor of importance in determining the duration of the pupal stage which varies from 61 hours at 20·8°C. to 45 hours at 25·5° and 37 hours at 29°.

Both in nature as well as under controlled conditions in the laboratory it was found that, for a large number of larvae hatched simultaneously, the emergence of adults usually lasts three or fours days, with a maximum at the same hour on each of these days. The period of emergence is proportional to the duration of the post-embryonic development and may under unfavourable conditions last weeks.

Maximum emergence of imagines has been found to occur at various times of the day. This is as should be expected since the hour of pupation is fixed to a certain period of the day, and the duration of the pupal stage is solely dependent on the temperature.

The difference in the duration of pupation in males and females is very small but owing to the rather marked sexual difference in the duration of the larval stage, 129 hours for males against 145 for females at 29°, there is a preponderance of males during the first emergence maxima and of females in the last.

It is concluded that if the temperature of the water in which the larvae are living in the field is known, it should be possible to predict at what hour of the day the emergence maxima will take place.

It is felt that the 24-hour catch presents a valuable method of studying the biting-behaviour of mosquitos in the field, and further that conclusions concerning seasonal abundance, vertical distribution and times of biting-activity must be based on catches of this type if serious errors of interpretation are to be avoided.

The time-divisions of the catch should not exceed one hour, and even shorter intervals may be desirable. Timing should be related to the actual times of sunrise and sunset. Where possible, a series of consecutive catches should be carried out, and a shift system must be carefully considered in relation to the particular series projected.

Usually the results from different levels above ground should be treated separately in working out biting-cycles, and this may also apply to results from different seasons or different localities. Further, while in some instances the summation of long series of catches seems permissible, in others it is not, and in these detailed analysis of the figures may be necessary before consistent behaviour-patterns become apparent.

In cases where a measure of the central tendency is to be employed, the geometric mean as modified by C. B. Williams appears to be the most suitable.

A review of the available information concerning gall midges as endoparasites shows that only three species in two genera have been described.

Endaphis perfidus Kieffer is a parasite of apterous Drepanosiphum platanoides (Schr.) (Aphididae) in Lorraine and England. Although on several occasions larvae of Endaphis sp. have been found in England, the Netherlands and Germany parasitising other Aphids, practically no information additional to that supplied by Kieffer has beeen published. In only one instance besides E. perfidus has the adult midge been reared and figured, i.e., Endaphis (cf. perfidus Kieffer) in Macrosiphum jaceae (L.) on Carduus in Germany.

Endopsylla agilis de Meijere is a parasite of winges Psylla foersteri Flor (Psyllidae) in the Netherlands. The bionomics of what is almost certainly the same species, parasitising P. mali race peregrina Foerst. on hawthorn (also P. pyricola Foerst. and P. melanoneura Foerst.) and P. mali (Schmidb.) on apple, respectively, have been studied in Scotland and Germany.

Endopsylla endogena (Kieffer) was found parasitising the larva of Stephanitis pyri (F.) (Tingidae) in Portugal but has not been recorded again.

A fourth species, Pseudendaphis maculans, gen. et sp. n., that parasitises various Aphids in Trinidad, has now been described.

Indications are given of the whereabouts of any existing types or other specimens of all the known endoparasitic gall midges.

Observations on the behaviour of Anopheles gambiae Giles and A. funestus Giles in experimental huts and ordinary African houses were carried out in a low-lying area of Tanganyika. Special attention was paid to the exodus of females at different stages of the gonotrophic cycle and to the composition in terms of ovarian development of the house resting population.

About 5 per cent. of the biting population of gambiae and the same number of funestus were shown by the use of window traps to be leaving experimental huts after feeding.

Forty three per cent. of half-gravid gambiae left an experimental hut at dusk, 12–24 hours after entering for a blood meal, whereas only 3 per cent. of funestus left under the same conditions.

Daytime spray catches of gravid gambiae and funestus made in ordinary African houses during the hot season were about 50 per cent. and 30 per cent. lower, respectively, than the corresponding numbers of recently fed specimens. A. funestus therefore makes rather less use of outside shelters than gambiae during the hot months.

In the cool season about 50 per cent. of half-gravid and gravid funestus were absent from house catches.

No mortality could be detected amongst funestus females resting under natural conditions for 24 hours in an experimental hut.

Re-entry of gravid funestus into unoccupied and open types of inhabited houses occurs at dawn.

Glossina palpalis fuscipes Newst. was studied in lake-side forest in north-east Lake Victoria and in riverine forest on the Kuja river, which runs into Lake Victoria. Climatic records are given. Trees counts were made in fifty acres of lake-side forest.

Populations of G. palpalis exhibit long-term fluctuations which are not annual and not related to season. On the lake shore, the density of G. palpalis is roughly correlated with the width of the forest, being least where the forest is narrow. In a block 2,200 yeards along the shore by 100 yards wide (this was the widest forest studied) the population was 4,600 non-teneral males. The mean catch along the 2,200 yards of shore was 78 non-teneral males. Calculated on an area basis, this is more than ten times the population which would be inferred from the same catch of G. morsitans or G. swynnertoni. The mean death-rate in this isolated block was 26 per cent. per week, and the mean length of life was 27 days.

Analysis of catches indicates that riverine G. palpalis are always more hungry than those on the lake shore, for the percentages of tenerals, of females, and of males attacking, are all higher on the river. Catches from a boat produce more females but fewer males than land catches. Carrying a screen produced more females on some occasions, but not on others, the discrepancy being unexplained.

Conclusions concerning the distribution and field habits of Anthrenus verbasci (L.), A. fuscus Ol. and A. museorum (L.), are based upon the results of three surveys.

The first survey comprised the collection of adults of Anthrenus from attractive flowers, e.g., hogweed, Heracleum sphondylium, in various localities furing June and July. This showed that:—

A. Verbasci occurred in large numbers only in the suburban areas of south-east England, extending also to the west along the south coast.

A. fuscus was generally distributed in all types of locality in the south reaching a peak abundance in the vicinity of farms. Its members diminished rapidly towards the north.

A. museorum occurred in small numbers only, often accompanying A. fuscus.

The second survey comprised the collection of larvae from natural habitats and included results from an earlier survey of certain birds' nests. This showed that:—

A. verbasci was characteristically an inhabitant of dry birds' nests.

A. fuscus was usually found feeding on dead insects around spiders' webs, under the bark of trees, etc.

A. museorum occurred in small numbers in company with A. fuscus.

The habitat difference between A. verbasci and A. fuscus was sharply defined. Only very rarely was one sspecies found in the habitat typical of the other.

Sixteen of the numerous described species of Carpophilus Stephens have been found associated with stored products in different parts of the world, and of these, several species are continually distributed by international trade and have become established in many countries.

A key to most of these species is given, several of the species are redescribed and new taxonomic characters, mainly associated with the genitalia, are introduced and figured.

A Table is given summarising recent importations of Carpophilus species into Britain, detailing the commodities on which the insects have been found, their places of origin and the number of individual records.

An account is given of the life-history of Pseudendaphis maculans Barnes, a common and widely distributed endoparsite of Aphids, especially of Toxoptera aurantii (Boy.), in Trinidad. Alates are parasitised to a much smaller extent than apterae : it is thought that this is due to the parasite larva inhibiting wing development. Nymphs appear to be attacked usually during the first stadium; the parasite larva is fully fed after 6 to 7 days. Shortly before the larve leaves its host the latter assumes a characteristic spotty appearance, due to numerous granules of dark matter that are readily visible through the integument, which has become paler and more transparent than normal. Pupation takes place in the soil: 9–10 days after leaving the host the adult emerges, invaribaly during the early afternoon.

In the course of general studies on control of Culex pipiens fatigans Wied. in British Guiana, the indigenous shrub Ryania speciosa, proven to possess insecticidal activity against certain agricultural pests, was investigated.

Aqueous extracts of the dried stem were shown to possess toxic properties against all larval stages of C. pipiens fatigans under clean laboratory conditions. Under conditions simulating a water-logged pit latrine, however, toxicity was greatly reduced by adsorption of the active agent ryanodine, rendering the crude stem relatively ineffective after 16 days. Because of the great bulk of unprocessed material required for even this limited result in pit latrines—which constitute an important local problem—Ryania was not considered of practical value in C. pipiens fatigans control.

Aqueous and alcoholic extracts of Ryania speciosa had no contact insecticidal properties against adults of this species.

The general distribution of the Muscidae (other than Glossina) of medical interest in the Sudan is discussed, and brief notes are given on some Muscids in relation to trypanosmiasis.

Eighty-six species of some medical interest, belonging to 22 genera, are listed, with records of their distribution and notes on the habits of several of them.

An experiment is described where applications of a coarse aerosol were made to savannah woodland containing the tsetse flies, Glossina moritans Westw., G. swynnertoni Aust. and G. pallidipes Aust.

Seven applications were made, each at a nominal dosage of 0·25 lb. of technical DDT per acre and 0·25 gallons of solution per acre. The applications in any particular part of the treaed woodland covered an interval of 90 days, or rather more than two pupal periods.

The coarse aerosol was produced by emitting the insecticidal solution under pressure through fine nozzles fitted to a boom. It had a mass median diameter of approximately 60 microns, and droplet dismeters varied from a few microns to approximately 200 microns.

The population of G. pallidipes was so drastically reduced that it has subsequently dies out. The reduction of G. morsitans was approximately 95 per cent. The differences between the reductions are attributed mainly to differences between the ease with which the three species can be killed. It is pointed out that this is not necessarily equivalent to differences in susceptibility.

Comparisons are made with previous experiments, and the different results of the various experiments are difficult to explian satisfactory. The increased cover in savannah areas during the leafy period may have reduced the effectiveness of the applications, and the total periods covered by the various series of applications were probably also important. Random effects, leading to ineffective treatments, may also be important.

Costs are discussed.

Observations were made in Sierra Leone from September 1949 to November 1951 on the incidence of trypanosomes in Glossina palpalis (R.-D.), in continuation of those previously reported that began in September 1948. Flies were dissected; trypanosomes found to be restricted to the proboscis were classed as Trypanosoma vivax and those found also or only in the mid-gut as T. congolense. None of the flies had infected labial glands. The whole data are presented for the sexes separately by months.

The existence of a marked seasonal variation in the incidence of T. vivax in G. palpalis is confirmed. The highest rates of infection occured in the months of heavy rain, and there was a significant inverse correlation between the monthly means of infection rate and of hours of sunshine. The cause is unknown, but possible explanations are discussed.

The older the fly, as judged by its appearance, the greater the rate of infection by both species of trypanosme; the virtual absence of infection in the youngest group of flies does not support the theory that they can only be infected when very young.

In the case of T. vivax, but not in that of T. congolense, females flies were more heavily infected than males. This may be due to larger food intake by the females, or to males, because of their more active life, appearing to be older than they are.

The “ North Block ” at Kikore, Central Province, Tanganyika, was treated with insecticide dispersed from an Anson 1 aircraft during the period 23rd January to 4th May 1951. The area consisted of some 4,000 acres of mixed bush, including about 230 acres of miombo, infested by two species of tsetse fly, Glossina morsitans Westw. and swynnertoni Aust.

The insecticide used was equivalent to a 19·4 per cent. solution of technical BHC (equal to 2·45 per cent. γ isomer) in 50 per cent. diesel oil, 50 per cent. power kerosene. The solution was dispensed through a boom and nozzles under pressure as a coarse aerosol (mass median diam. 70 microns), at a nominal mean dose of 0·25 lb. technical BHC per acre per application. Eight applications were planned and seven completed.

The first application was relatively ineffective, and for the second and subsequent cycles the emission rate was increased and over part of the block the swathe width was reduced. The result was a much improved kill but neither species of tsetse was exterminated.

Owing to the number of factors involved, it is not possible to give any principal reason why this experiment was less successful than previous ones, but many of the difficulties encountered are inherent in rainy-season operations in East Africa.

An isolated area of 2,200 acres of thicket and thronbush in the Central Province, Tanganyika, was treated from the air with a DDT-in-oil aerosol in an attempt to eliminate the tsetse fly, Glossina swynnertoni Aust. Eight applications of 0·25 lb. technical DDT per acre were planned to be done at fortnightly intervals.Delays due to unseasonal bad weather reduced this to seven at a slightly higher rate and over a longer-period.

G. swynnertoni was reduced from an apparent density of about 7 to zero at the end of the second application. No flies were caught after the fifth application for a period of six months.

It is not possible to say whether the few caught since then have been brought in or are the offspring of survivors of the insecticidal treatment.

This experiment was more successful than that on the Galapo Block in the same ares, to a highly significant degree, and this is attributed to the vulnerability of the smaller population present. It was doubtfully better than the first treatment of the North Block, also in this area, because the increase in population in the latter block may have been assisted by immigration.