(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.

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.

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.

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.

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.

1. The work here reported was carried out in Bwamba County, Uganda, a district where human yellow fever has recently occurred. It consisted of continuous 24–hour catches of biting mosquitoes in a banana plantation, made simultaneously at ground level, 6 ft., 12 ft. and 18 ft.

2. Aédes (Stegomyia) simpsoni, Theo., the carrier of human yellow fever in Bwamba, was found to be active throughout the day at all these levels.

3. The presence of sylvan mosquitoes in the banana plantation was noted. The nearest forest was ½ mile away.

4. The biting cycle of the strictly diurnal A. simpsoni was studied, and it was found that this species was most active on warm cloudy days. The main factors decreasing its activity appeared to be cold, wind, and direct hot sunshine.

A new mealybug injurious to cacao in the Gold Coast was described by Laing in 1944 under the name of Pseudococcus exitiabilis (Bull. ent. Res., 35, p. 91). It was said that it had been reported by the collector, Mr. H. E. Box, to be one of the Coccid vectors of the “Swollen Shoot” virus disease of Cacao. This was later confirmed by Box (Nature, 155, 1945, p. 608).

In February, 1944, No. 2 Entomological Field Unit, R.A.M.C., arrived in India with the first consignment of DDT (dichlor-diphenyl-trichlorethane) to be used there for research purpose. Experimemts to determine the larvicidal effects of this substance were carried out by the unit, of which I was Commanding Officer.

Ferrière (1941) in his study of the Euplectrini (Chalcidoidea, Eulophidae) has described three yellow species from Ceylon, all parasites of nettle grubs (Limacodidae) from tea, and has erected three genera to accommodate them. They are Neoplectrus maculatus (1940), Platyplectrus natadae (1941), and Metaplectrus thoseae (1941). In April, 1944, the writer obtained two females from Thosea cervina, and at first sight they were thought to be Metaplectrus thoseae, but closer examination showed them to differ from Ferrière's description in several important respects. In order to ascertain their systematic position the following brief study of Ceylon specimens was under taken.

Since the recognition by Bolivar (1912) of Hieroglyphus nigrorepletus as a distinct species, Coleman's (1914) note and Uvarov's (1922) valuable revision of the rice grasshoppers, it has been clear that in the earlier literature this species has been confused with H. banian, F., chiefly under the name of H. furcifer, Serv., while H. bettoni, Kirby, 1914, and H. vastator, Carl. 1916, are synonyms.

The theory of phases, Uvarov (1921), had the object of explaining the interrelationship between different forms of Locusta migratoria and Locustana pardalina. This theory has been accepted by most entomologists working on locust problems. Authors such as Faure (1923 and 1932), Johnston and Maxwell-Darling (1931) and later a series of others including Hussein and Ramchandra Rao, proved and confirmed the truth of Uvarov's theory.