1. The Viburnum aphis, Aphis (Doralis) viburni, Scop., is described and compared with two other species, A. fabae, Scop., and Ceruraphis eriophori, Wlk., also found on Viburnum opulus.

2. Transference experiments show that colonies can be established artificially on Euonymus europaeus and Rumex obtusifolius, but not on other common host plants of A. fabae.

3. The sexupara is apterous and produces mixed colonies, thus differing from A. fabae where an alate gynopara produces only oviparae, the males arising from an apterous mother on the summer host.

The considerations affecting the design of a spray testing chamber are discussed, and a description is given of equipment specially intended for use with mosquitos as the test insect. In essentials the apparatus consisted of a metal chamber surrounded by a “Masonite” cabinet with an air space in between. In this space air, at a constant temperature, was circulated around the outer face of the inner metal chamber and so controlled the temperature of the spray chamber. The cabinet was fitted with lights; wet and dry bulb thermometers to check the humidity, which was controlled by blowing in steam; a fan to circulate the air; a spray gun; four ports through which the insect exposure cages were introduced into the chamber; a shelf to carry these cages; and an exhaust and an intake port to allow the mist to be removed at the conclusion of the test. Finally, there was a door on one side allowing access to the interior. It will be noted that the insects were introduced into the spray chamber in cages and not allowed to fly freely. This greatly facilitated the collection of insects at the conclusion of the test. Under the routine testing conditions adopted the insects were not introduced until four minutes had elapsed after spraying. They were then exposed for ten minutes and afterwards transferred to clean recovery cages.

The practice of caging the insects and placing them on a shelf opposite a window within the spray chamber permitted the insects to be closely observed and the rate of paralysis (knockdown) to be followed. In general, however, the rate of knockdown, when it occurs, was not so sensitive a method of comparing insecticidal efficiency as the twenty-four hour percentage kill.

In practice the apparatus was found to give satisfactory results. It permitted accurate comparisons to be made between different strengths of a given insecticidal solution, but care had to be taken to ensure that the non-volatile content of the sprays being compared for toxicity was essentially similar. When this was not so, other things being equal, the spray which produced the less volatile mist (i.e., the larger particle size) gave the higher kill. When working on activators, which are usually non-volatile materials, it was therefore necessary to add an equivalent quantity of, say, high vacuum pump oil to the control spray before making the comparison. Examples of the application of the method of pyrethrum, DDT, and activated sprays are given.

The set of standard conditions chosen for the routine testing procedure were sometimes rather arbitrarily fixed but usually with due reference to the requirements of the insects or to practical testing conditions. Since two of the conditions chosen, i.e., the use of caged insects and exposure after an interval of four minutes after spraying, were rather artificial from the point of view of practice and might conceivably have led to conclusions inapplicable to practical conditions, the effect of modifying certain of the standard procedures was investigated. The results of these experiments are fully described in the text. It was concluded that temperature influenced the level of kill recorded considerably, the kill being lower when the temperature of the spray chamber was dropped 10°C. Humidity seemed to have little or no effect within the range 40–80 per cent. R.H. Increasing the interval at which the insects were inserted after spraying from 0 to 10 minutes affected the level of kill without influencing the comparative efficiency of the insecticides examined. On the other hand caging the insects had a pronounced effect on the comparative efficiency of pyrethrin sprays with and without added non-volatile material. This was thought to be due to the delay in access of the spray droplets to the caged insects which permitted a sufficient interval for the differences in particle size to become established. With caged insects inserted before spraying, therefore, the biological efficiency of a pyrethrin spray without, added non-volatile material is much lower than when some such substance as high vacuum pump oil is added, whereas this difference is much smaller when the insects are exposed free in the cabinet (Table X).

(1) The proprietary emulsion “Guesapon ”, containing 5 per cent. DDT, gave an unsatisfactory control of carrot fly damage on a plot scale.

(2) Treatment of the carrot foliage with this emulsion was more effective than treatment of the soil.

(3) A I per cent. emulsion of DDT applied to carrot foliage in the field gave 100 per cent. mortality of carrot flies in the laboratory for 26 days after treatment and showed marked toxicity after a further 38 days.

(4) The DDT spray deposits were very, resistant to treatment with water and remained active after death of the foliage. They were also very toxic and lasting on potato foliage.

(5) Deposits given by ½ per cent. and I per cent. DDT emulsion were similar in toxicity and persistence. The ½ per cent. is, however, slower in action.

(6) From a treated surface the carrot fly is able to acquire a lethal dose of DDT in a very short time, probably by absorption through the feet.

(7) Emulsions containing ½ per cent. and I per cent. DDT applied to carrot foliage under cages in the field both gave 95 per cent. kill of carrot flies for a month after application. The treatments also gave a high kill of other insects.

(8) Soil samples showed that the larval population and the damage was much lower in the treated than in untreated cages.

(9) In a field trial 2⅓ acres of carrots were treated with ½ per cent. DDT emulsion at about 50 gals. an acre.

(10) Sweeping showed a rapid decline in abundance of flies after treatment and high mortalities were observed. These features did not occur on neighbouring untreated carrots.

(11) These effects lasted for some 21 days after treatment and a marked reduction of larval population and damage resulted.

This review of investigations of Lygus simonyi, Reut., was originally written early in 1944 as a handing-over report, and was not intended primarily for publication. As I was then about to leave Uganda, it seemed desirable to place on record, for the information of my successors, the work which I and others had done, even though the investigations were still in an early stage. Since then, the opinion that publication of the report would be useful as a basis for future work has been expressed by the Empire Cotton Growing Corporation and others, and I have therefore agreed to publish it in spite of my consciousness of many shortcomings in it.

In Melophagus ovinus, derris dust is shown to be absorbed through the spiracles and tracheal system. The amount of dust entering the tracheae is governed by the structure of the inspiratory spiracles and the rate of flow of the inspired air.

Factors stimulating the rate of respiration of the insect—i.e., increased muscular activity, the presence of 5 per cent. carbon dioxide and a rise in temperature, increase the rate of entry of derris into the body.

Penetration of derris takes place slowly through the external cuticle at 30° C., but not at all at 20°C. It is postulated that the entry of derris through the cuticle probably depends on the hardness of the lipoid layer.

It is essential that an oil used for killing mosquito larvae on the surface of stagnant water should cover the whole surface completely with a spread film. Only if the oil spreads completely over the surface can it be certain of reaching all the larvae, penetrating into their respiratory system, and so killing them. Although practically all oils (except the most highly refined mineral oils) will spread on clean water surfaces, most stagnant waters have surfaces so contaminated by surface films, visible or invisible, that their surface tension is reduced much below that of clean water. This hinders, or completely prevents, spreading of oils of low spreading power which would spread on clean water. Therefore, other things being equal, an oil with a high spreading power is preferable to one with a low spreading power; indeed an oil with a low spreading power may, in practice, be of little or no use. A simple method of determining spreading power is thus of considerable importance.

1. 97 per cent, of the ♀ A. gambiae, A. funestus and A. melas remained until after dawn in the huts in which they had fed.

2. ♀ A. melas seldom left suitable huts in the daytime.

3. There was a high positive correlation between the time at which ♀ A. funestus entered huts and the time of moonlight. The maximum correlation coefficient was between the size of the catch at 8 p.m. and the duration of moonlight after this period, and its value was –0·783±0·068.

4. During moonless periods, the flighting of ♀ A. funestus was partially inhibited, and when the moon came out, the waiting mosquitos entered the huts in greatest numbers. The average proportion caught when the moon rose during catching periods ending 10 p.m., midnight and 7 a.m. was approximately 50 per cent., 100 per cent. and 400 per cent. greater, respectively, than the proportion caught during these periods on moonless nights. On moonless nights many mosquitos waited until twilight of the following evening before entering the huts, and in consequence the average proportion caught in the period ending 8 p.m. was six times greater on moonless nights than on the nights after full moon.

5. The records for ♀ A. melas are less complete, and the correlation coefficient for the relation between time of entry and time of moonlight has the value 0·421±0·184, a result which is barely significant. In view of the highly significant correlations found in the case of A. funestus it is unlikely that this correlation is fortuitous.

6. The average rate of entry of ♀ A. funestus throughout one complete lunar cycle at Krabonekrom, Gold Coast, was 27 per cent. before 8 p.m., 22 between 8 p.m. and 10 p.m., 21 between 10 p.m. and midnight and 30 after midnight. The similar rates for A. gambiae (based on very few records), were 10, 20, 30 and 40 per cent. respectively. Comparable rates for A. melas in Sierra Leone are not available, but at least 45 per cent. entered before 10 p.m. (= 11 p.m. Gold Coast time).

7. The essential difference between the behaviour of ♀ A. funestus and that of A. gambiae is that the former flight earlier than the latter. A. funestus also seem to be more active at dawn, so that they are more crepuscular in their habits than A. gambiae.

8. 58 per cent, of the Anophelines caught at 8 p.m. were unfed. This indicates that early entrants usually rest after entry and before feeding, and average time of biting is later than average time of entry. Gravid or half-gravid mosquitos and those containing partly-digested blood, did not enter the huts; there was evidence that Anophelines usually became fully gorged at one feed. Of the Anophelines caught in huts after dawn 95 per cent, were fully fed.

DDT (p,p'-dichlordiphenyl-trichlormethyl-methane) has been shown to be very toxic to the housefly, Musca domestica, L., when applied as a spray containing 0·1 per cent, w/v or more in kerosene. DDT at 1 per cent, gives an effective spray for practical use, but at lower concentrations the speed of knock-down is too slow. This disadvantage can be overcome by the admixture of a small amount of pyrethrum. A mixture of 0·03 per cent, w/v total pyrethrins and 0·1 per cent, w/v DDT in kerosene is recommended as a suitable fly spray for practical use. This mixture can be stored in glass bottles in the dark for at least 17 months at 27·5° C. without marked deterioration. Its toxicity may be increased by the incorporation of a suitable activator, e.g., sesame oil or isobutylundecylenamide.

The impurities in crude preparations of DDT appear to exert no toxic effect on houseflies.

DDT acts more slowly when dissolved in industrial methylated spirit than in kerosene.

Attention is drawn to the residual film effect of DDT on walls, etc., and an example is given to show how this effect was employed in the control of a fly population in a kitchen.

The symptoms of poisoning of flies by DDT are compared with those caused by pyrethrum. DDT is relatively slow in action; it is a severe irritant, causing the flies to buzz violently at one stage; it induces marked tremors during the coma preceding death; and, at death, it causes the legs to be tightly flexed at the femoro-tibial joint. When the pyrethrins and DDT are mixed in a spray, these constituents, so far as can be judged from the train of toxic symptoms, act independently, so that the rapid paralytic effect of the pyrethrins keeps the insects immobile until the slow lethal effect of the DDT supervenes.

This work has been carried out as part of the programme of research of the Pest Infestation Laboratory, and this account is published by permission of the Department of Scientific and Industrial Research.

The work described below forms part of an investigation to determine the residual toxicity of DDT when applied to the surface of materials commonly used in the construction of buildings. the bed-bug (Cimex lectularius, L.), because of its wide distribution and habit of infesting surfaces, either exposed or hidden, is an eminently suitable subject for such an investigation. In order to compare the residual toxicity of different surfaces after treatment with DDT, it was considered an essential preliminary step to ascertain whether or not the biological condition of the insect influenced its resistance to the insecticide. The present investigation was, therefore, undertaken to establish any possible variations in resistance which could be correlated with one or more of the following biological factors:— 1. starvation for different periods; 2. sex; 3. stage in the life-history; 4. temperature.

When I was revising the genera of the DIPRIONIDAE (Benson,1939), the British Museum had very scanty material of Neodiprion other than of the sole Palaearctic representative of the genus, N. sertifer (Geoffr.). The few North American specimens of the genus, only five females belonging to five species and a few unnamed males, were all ancient specimens in poor condition and pinned so as to obscure the shape of the scutellum. I had therefore to supplement my knowledge of Nearctic Neodiprion by information kindly sent to me by the late Miss Grace Sandhouse, gleaned from specimens in the collections at Washington. Atwood and Peck (1943), in dealing with long series of Canadian Neodiprion, have since found that the shape of the scutellum, as defined in my paper, is rather difficult to interpret and is liable to considerable individual variation.

This paper describes part of an extensive programme of research on new methods of controlling body lice carried out during 1940–1942. The work was initiated by Professor P. A. Buxton, F.R.S., with whom the writer was privileged to collaborate, and financed by grants by the Medical Research Council. The results proved for the first time the possibility of continuous protection against body lice over a period of several weeks after treatment. To some extent, the materials and methods of achieving this have now been improved or superseded; but it has seemed worth putting on record some details of technique and the results for their scientific interest.

The investigations herein recorded show that DDT is more toxic to bed-bugs when available on a surface as an oil solution than as a dry film, and that the toxicity of the latter is determined to some extent by the volatility of the medium in which DDT is applied. The results of trials on filter paper, glass and unpainted wood suggest that the minimum period of exposure to a dry film of DDT necessary for the insect' to acquire a lethal dose is one hour, and that this critical period is constant irrespective of the nature of the DDT-treated material to which the insect is exposed. Tests with bugs on DDT-impregnated filter paper show that this period can be curtailed considerably by the addition of a fine oil spray.

Durant l'année 1943, au cours de la campagne de lutte contre le criquet pèlerin (Schistocerca gregaria, Forsk.) il a été fait un large emploi des fruits de la pastèque (Citrullus vulgaris, Schrad.) dans les régions sahéliennes de l'Afrique Occidentale Française, des côtes de la Mauritanie à la rive occidentale du lac Tchad.

(a) Small field experiments (not attempts at control) are described with DDT in emulsion and in solution in mineral oils, 5 per cent, pure DDT in each material. These were tested on mosquito larvae (mainly A. funestus) under conditions that provided good opportunities for repetition and measurement of dose per unit area. Considerable day to day fluctuations were observed in numbers of larvae obtained by dipping, before the insecticide was applied.

(b) Preliminary work showed that kerosene, or dieseline without DDT, were not larvicidal in doses up to 0·5 cc./sq. yard. The dose of oil that was harmful was not determined.

(c) It is clear that DDT, either in oil or as an emulsion, is a very effective larvicide, as is well known from work (mostly unpublished) in many parts of the world.

(d) One may compare the effectiveness of DDT as an emulsion (Mixture A) and in solution in dieseline, as follows:—

It is clear that, under these rather precise conditions of testing, the dieseline solution is more effective than the emulsion both in the minimum amount required to kill, and in lasting effect.

(e) Field tests seem to indicate that DDT dissolves from oil into water, so as to make a larvicidal solution, at least when the water is shallow.

(f) Even if one puts down a relatively high dose (say 0·10 cc. of 5 per cent. DDT per sq. yard, at least ten times the quantity that will kill all larvae) the effect passes off in a few days, even on stagnant waters. It is not known what happens to the DDT, and difficult to know why it disappears.

(g) A heavy dose of DDT (0·50 cc. as above) gives a period of complete kill, followed by a period of partial irregular control. This was more often observed with solutions of DDT than with emulsions and might last as much as four weeks. No explanation of this irregular effect is put forward. It seems most difficult to understand how an insecticide, applied over an area of only a few square yards, can continue to kill some but not all larvae for a period of weeks.

(h) Except in one experiment, in which emulsion destroyed small fish, there was no evidence that creatures which prey on mosquito larvae were destroyed. There was no reason for thinking that after the population of mosquito larvae got back to normal it rose to exceptionally high figures (as it might have, had the predators been decimated).

1. To determine the percentage hatch of Calandra granaria eggs, the grain containing them should be kept for 6–10 days at 25°C. after a two-day oviposition period.

2. Pretreatment of grain with mercury vapour makes no difference to the fertility of eggs afterwards laid in it.

3. At 25°C. 99 per cent. of the eggs are sterilised in 24 hours and 87 per cent. in 8 hours, using what probably approaches the saturated vapour.

4. At 10°C., the sterilisation for periods of 24, 48, and 72 hours is 44, 87 and 93 per cent. respectively.

5. At 25°C., mercury vapour will penetrate at least 30 cm. of grain in 2 days. At 12°C., mercury vapour will penetrate at least 90 cm. of grain in 7 days.

1. The work was carried out in Bwamba County, Uganda, a district where human yellow fever has recently occurred. It consisted mainly of 24-hour catches in banana plantations and rain forest combined with climate observations.

2. It was found that forest was cooler and moister by day than a banana plantation while the plantation was cooler and moister than the open air. By night, however, the climate of all three environments was strikingly similar.

3. Methods used in making 24-hour catches and large scale routine catches are described. Trials with trap nets showed these to be less efficient than hand catching.

4. Experimental catches showed that Aëdes simpsoni, the only species known to be a vector of yellow fever in Bwamba, bites mainly in coffee gardens, maize fields and the thinner parts and edges of banana plantations. It is scarce in fully exposed situations. It occurs within the edges of primeval rain forest. It prefers human blood to that of goats, fowls, and monkeys, and attacks the head and shoulders selectively.

♂♀. Derm black, with uniform dense sandy-brown scaling above and opalescent scaling beneath.

Head short, not transversely impressed, the temples less than half as long as an eye; frons with the median stria partly obscured by scaling and with a few erect spatulate setae on each side; eyes strongly convex, highest behind the middle. Rostrum similar in the two sexes, a little longer than broad, about as wide at the genae as at the base, and with the sides slightly sinuate; dorsum with a high bare median carina that expands apically into a broad bare epistomal area, which is unevenly punctate and not marginate, the epistomal setae being rather sparse and narrow, the areas on each side of the carina densely squamose and obliquely impressed in the middle; mandibles less densely setose than usual and without scales; mentum with only a single row of setae along the apical margin. Antennae black, densely squamose throughout, scape straight, widening from base to apex; funicle with joints 1 and 2 equal, 3 as long as broad, 4–7 subequal and transverse; club with the basal joint pedunculate. Prothorax transverse (2:3), broadly rounded laterally in the basal half, widest at one-third from base, the basal angles rounded obtuse angles, not constricted apically, the base shallowly bisinuate with the median lobe short and broadly rounded; dorsum smooth, with dense overlapping striolate scales and short appressed spatulate setae, concealing the median stria, and with a large shallow impression in the basal angles.

In 1925, the writer (2) described some experiments that demonstrated the rôle of Helopeltis as a pest of cotton at Ibadan, Nigeria. Evidence was obtained that attack was greater on the improved indigenous Ishan (Gossypium barbadense, formerly described as G. vitifolium) than on either American Allen (G. hirsutum) or the ordinary native cotton (G. peruvianum).

Notes are recorded on some of the habits of members of the subgenus Coquillettidia of the genus Taeniorhynchus, with an account of catching and rearing methods employed. Fourth-stage larvae of eight different species have been caught and successfully reared to the adult stage, four of these for the first time. One new species is included in the list.

Keys are given for larvae and pupae, together with full descriptions of the larvae and pupae of the eight species dealt with.

Errors in the previous descriptions of T. aurites and microannulatus are pointed out.

It has been found to be expedient to determine the development of the Braconid parasite, Aphidius granarius, Marsh., under field conditions, following its artificial introduction in order to supplement the previous observations of the writer (Arthur 1944, 1945). The aim of the presaent work was to determine the degree of control likely to be achieved by the introduction of this parasite to corn crops known to harbour heavy Aphid infestations but lacking the corresponding paraponding parasitism. The work was undertaken during 1943–44 at Margam Cowbridge, and Ammanford, three widely separated locations in the south wales Area.