Experiments were carried out to study the possibilities of using ground or crop interference with the spray laden slip-stream of a helicopter flying slowly in the ground cushion to obtain a high dynamic catch of spray droplets. Experiments were carried out in 1945 and 1946 with a Sikorski type Y.R.4.B. helicopter and experimental spraying gear designed for the purpose.

The forward portion of the slip-stream annulus was explored by means of spraybars placed in three different positions. The position in the sector between angles of 15° and 45° with the direction of forward flying was found to give the best all-round cover and was the position in which the spray deposit was less influenced by alterations in the control-surfaces of the helicopter.

To obtain a fairly wide swathe of approximately 70 ft., the equivalent of two rotor diameters, the forward speed of 6–8 m.p.h. was found to be optimal, and it was observed that not only was good cover of the upper surfaces of the leaves obtained but the spray-laden slip-stream also gave a good cover of the vertical surfaces of the plants outside the rotary periphery and, in certain boom positions, descended and in rebounding produced a cover of the lower surfaces.

In order to obtain maximum dynamic catch and a good cover of the lower surfaces of leaves, spray-bars must not be more than 6 ft. above ground.

Helicopter spraying is wind dependent and in wind velocities above 12 m.p.h. uniform cover of spray deposit does not appear to be feasible.

The performance of the flattened out slip-stream and rebound depends on the type of crop, and as this affects the dynamic catch to a considerable degree, this phenomenon will be the subject of a special investigation.

The forward portion of the slip-stream was found to give a more even spray deposit than the aft portion because in the latter case vortices are caused by the rotor blades which affect the spray deposit.

In view of its limitations as regards speed and dependence on wind velocity, economic application of spray chemicals by helicopter at a degree of efficiency and workmanship equal to that of ground machines is only possible with a heavy load-carrying helicopter. A specification for such a machine has been issued to the manufacturers of rotory wing aircraft.

It is hoped that this report will be followed by a report on the performance data of the new spraying apparatus designed for the Sikorski S.51 which is based on the results of these investigations.

Several species of Tribolium are important primary and secondary pests of various kinds of cereal products and for this reason have long attracted the attention of entomologists. Some of the species are easily cultured in the laboratory and have therefore become favoured animals for experiments not particularly concerned with their rôle as pests. As a result of the two avenues of approach, a very impressive amount of information has now been accumulated concerning the habits and physiology of a few of the species.

The Pea Moth, Laspeyresia nigricana, Steph., is one of the principal pests of garden and field peas in Great Britain. Its larvae feed within the pods causing considerable damage to the developing seeds and giving to their contents a veryunsightly appearance. The insect is widely distributed in England and, according to Meyrick (1927), occurs in Scotland as far north as the Clyde. It is most prevalent, however, in the southern part of England, where in the pea growing counties of Lincoln, Essex and Kent it frequently causes severe losses. It is widely distributed in central and southern Europe while in North America it has spread, since its introduction, to all the main pea producing areas and has become a major pest.

The genus Phlebotomus has been much studied in recent years since the transmission of various diseases by some species has been established.It has now become a matter of importance to be able to identify species accurately in connection with the study of the epidemiology of the disease they are known or thought to transmit. It has been found that those which are closely related morphologically, often show marked biological differences and vary considerably in their rôle as transmitters of certain diseases.

1. A selected stock bred on middlings and not diapausing at 25°C. was used in these experiments. None of the larvae reared on Manitoba wheat diapaused at 25°C., 70 per cent. R.H.; some diapaused at 21°C. and 17°C., 70 per cent. R.H. At these lower temperatures development was slower, more food by weight was eaten, and the moths were heavier.

2. More larval substance by weight was needed to produce a male than a female adult.

3. It was possible to subdivide natural foods into 3 groups: (i) Those on which no larvae diapaused at 25°C., 70 per cent. R.H. (ii) Foods on which a fairly low percentage of larvae diapaused at 25°C. 70 per cent. R.H. (iii) Foods on which most, or all of the larvae diapaused at 25°C., 70 per cent. R.H.; these foods were all characterised by a high content of starch. The possible cause is discussed.

4. Larvae moult 4 or 5 times on Manitoba wheat at 25°C. 70 per cent. R.H. Most of the larvae developing on this food under warehouse conditions could be allocated to 6 instars. At 25°C., 35·5 per cent. R.H. the number of larval instars is increased— one larva died in 12th instar.

5. The growth curves, obtained by measuring head capsules of successive instars roughly follow Dyar's law, although the ratio of increase falls off in the last 2 instars.

6. The prepupal stage in E. elutella can be subdivided into five stages, on the basis of withdrawal of ocellar pigment, described in E. kühniella by Kühn and Piepho. Only those prepupae which have reached stages four and five attempt to pupate after the head is ligatured, the other stages remain as “permanent larvae”.

Length, 2·9 mm. General coloration pale yellow. Width of head, across the eyes, 0·7 mm. Tegmen with a brown marking as shown in fig. 1b. Male genitalia as in fig. la.

Type ♂ from Suva, Fiji, collected by R. A. Lever 14. viii. 1943, on bean.

According to Mr. Lever, E. leveri is a vector of a leaf-crinkle on leaves of Madagascar beans (Phaseolus Iwnatus) and cowpea (Vigna unguiculata) in Fiji.

The mosquitos of the reservoir area have been studied mainly with the object of planning suitable methods of controlling malaria. This paper is an account of the work done so far.

The diversity of conditions in the area, which is of such length that it has been divided into three sections, is described with special reference to the river and reservoir levels, predacious fishes, breeding places of mosquitos and water plants among which mosquitos breed.

The mosquito fauna of the area is described and observations on the breeding places and adult habits of the principal species are recorded. The large proportion of “ripe” females among Anophelines dissected is noted.

The probable effects of the reservoir conditions on the mosquitos are discussed.

Notes are given on certain species, and the relation of A. rufipes and A. pharoensis to malaria are discussed from circumstantial evidence. The former is provisionally regarded as a vector.

Control measures are described with particular reference to A. funestus (in the south), A. gambiae and A. rufipes, the latter being a vector of malaria expensive to control in the larval stage. The value of insecticidal dusts in the area is discussed.

Observations are recorded on the habits and behaviour of wild adult A. amictus hilli and A. punctulatus farauti at Cairns, North Queensland, and of the two subspecies and intermediate forms of A. punctulatus in New Guinea.

The most important points determined, which bear on the control of adults of A. punctulatus, are:—

(1) Females disperse from the breeding area shortly after emergence. During the day, they are rarely found indoors in any numbers, but hide away in moist, sheltered places in the bush in the vicinity of the source of the blood-meal. Fertilisation of the female takes place here, and these diurnal resting places are vacated only for the purposes of feeding and oviposition.

(2) Both before and after feeding, females rest on the walls, etc., of huts and houses, which they readily enter. There is some evidence that the normal flight is dose to the ground, and only comparatively small numbers enter houses built several feet off the ground.

(3) Activity does not usually commence until just after dark, and the peak of abundance occurs in the early hours of the morning.

(4) Females may disperse at least one mile from their breeding grounds in search of a blood-meal.

(5) In New Guinea there is a distinct preference for the native.

(6) Whilst A. pundulatus farauti does not show any marked preference for man, animal or bird, A. pundulatus pundulatus has very definite androphilous tendencies.

The habits of A. amictus hilli are broadly similar to those of A. pundulatus farauti, but differ in important details. It does not rest indoors during the day, but its favoured outdoor habitat awaits determination. Only a few females were found at Cairns in the bush diurnal resting places used by A. pundulatus farauti, whilst the large numbers observed on the breeding area were there for the purposes of oviposition. Fertilisation takes place in the breeding area, where the males remain. There also appears to be a different nocturnal periodicity from that observed for A. pundulatus farauti.

An attempt was made to determine the ages of the females captured at night and during the day by means of the criteria of ovary development, wing condition, presence of blood and of spermatozoa. The interpretation of these criteria was assisted by observations on bred A. pundulatus pundulatus.

Limewashes containing DDT or “Gammexane” were tested for insecticidal action on mosquitos (Aëdes aegypti) by confining the latter in cages with treated walls and ceilings. Only about 60 per cent, of the total internal surface of the cages were treated but the mosquitos were averse to settling on the floor, window, etc., which constituted a large part (28 per cent.) of the untreated area.

Limewashes containing 160 mg. DDT per square foot gave a high kill of mosquitos after two hours' exposure in the cage; and 8 mg. per square foot of the active principle of “Gammexane” gave a high kill with a one hour exposure.

Both treatments remained effective for 6–8 weeks under temperate conditions.