Endrosis lactella is widely distributed in Britain, where it is a minor pest of stored products, especially of grain and seeds.

The incubation period of the egg varied between 42 days at 10°C. and 6·0 days at 26°C. It was almost unaffected by changes in relative humidity.

Survival of eggs was low at high temperatures and low humidites, and the mean survival from complete batches of eggs at 70 per cent. R.H. 25°C. was 44 per cent. The highest survival recorded was 81 per cent.

On a diet of middlings the larval stage lasted 133 days at 90 per cent. R.H. 10°C, and 38 days at 90 per cent. R.H. 25°C. No adults were reared from larvae grown below 80 per cent. R.H. At 90 per cent. R.H. and 25°C. there were 7 instars.

On various foodstuffs at 90 per cent. R.H. 20°C, duration of the larval stage varied between 40 days on dead moths and 109 days on macaroni. Survival to the adult stage varied between 75 per cent. on whole wheat and 20 per cent. on groundnuts.

The pupal incubation period was 58 days at 10°C. and 10·4 days at 25°C, and was approximately the same at all humidities.

The time required for complete development from egg to adult was 235 davs at 10°C. and 62 days at 25°C. (90 per cent. R.H.).

There was a significant correlation between the weight of a female moth at emergence and the number of eggs laid. Egg output was lower at 25°C. than at 15°C, was not significantly affected by relative humidity, but was increased by provision of drinking water. Weights of females varied from 2·9 mg. to 9·4 mg. and egg output from 14 eggs to 231 eggs.

The sex ratio of the adults in the dried grass culture was found to be 1 male to 23 females.

Longevity could not be correlated with weight in all experiments, but, in the case of mated females, was dependent upon temperature, humidity and availability of drinking water. The mean adult life in days was 3–0 at 30 per cent. R.H. 25°C.; 5·0 at 90 per cent. R.H. 25°C.; 9·1 at 90 per cent. R.H. 15°C.; and 8.9 at 70 per cent. R.H. 25°C. + drink. Mated males were very short-lived (2–4 days at 70 per cent. R.H. 25°C).

The only important predator was the mite, Cheyletus eruditus, which attacked the young larvae.

The status of the Mediterranean fruit fly in Israel is reviewed briefly. Apricots, peaches and guavas are the most severely attacked of the summer fruits.

The ecology of the various stages of the insect is discussed. It is pointed out that, in addition -to temperature, the type of food influences the length of development of the larva. The threshold of development in the temperature development hyperbola has been calculated and found to be between 10–11°C.

The threshold of development of the pupae was found to be close to 11CC. A daily exposure of the pupae for six hours at a temperature of 32–37°C. caused no injury, but a similar exposure at 42°C. brought about a heavy mortality. At 46°C. one hour's exposure resulted in considerable injury whilst three hours' exposure killed 80 per cent, of the pupae. This explains the very high mortality of the pupae in the groves during June, July and August.

A study of the development of the eggs in the ovarioles at various degrees of temperature indicated that at 18–22°C. no appreciable development took place and at 23–25°C. it was still retarded. The optimum development temperature was found to be 27–29°C, whilst 33–34°C. was actually detrimental.

A study of the length of life of the adult showed that survival was longest between 16–19°C. at which temperature it took 100 days to reach 50 per cent, mortality and 200 days a 100 per cent, mortality.

The fluctuation of the fly population in Israel is discussed in detail. It is pointed out that the prevalence of host fruits is one of the great factors responsible for these fluctuations. An analysis of the climatic conditions month by month and its influence upon the fly population is discussed. The curve depicting the fluctuations of the fly in the coastal plain has two depressions, one between December and January, and the other in July and August. In the Upper Jordan Valley, the summer depression was more clear-cut than in the maritime plain, and the spring population reached a much greater height than that in the autumn.

The fly appeared about two months later in the hills than in the plain, namely towards early June, and it disappeared also earlier, presenting a single peak in July and August.

The best method of assessing the wetting powers of liquids is to measure the contact angle formed with a particular solid surface. In order to study the wetting of insects by spray liquids, it was necessary to measure, as rapidly as possible, the contact angles of very small droplets on restricted surfaces (such as portions of the insects). The apparatus used projected a greatly enlarged image of the drop, the outline of which could be traced very quickly and used for subsequent calculations.

Under practical conditions, spray droplets impact on insects with some relative velocity either due to drift of the spray particles or to flight movements of the insect.Measurements were therefore made of the contact angles formed by droplets of water of known size falling on to insects (or to a beeswax surface) at a known speed. It was found that with rather large drops (5 mm. diameter) the contact angles formed were somewhat lower than the normal advancing contact angle. With small droplets (0·1-0·5 mm. diameter) there was no difference. Biological tests were made with 30 species of insects, differing widely in the nature of their integument and habitat. The resistance to wetting was found to vary greatly, not only from species to species but also on different parts of the body of a single insect. In general, most of the insects were readily wetted by oils and unwetted by water. Insects withhard cuticular lipoids, such as Tenebrio, were more hydrophobic than the Blattidswith greasy cuticular waxes. A few species were both lipophilic and hydrophilic (larvae of Mamestra, Polia, Musca). Apart from the chemical nature of the cuticle, irregularities and the presence or absence of hairs were important. Increased roughnesslowers the contact angles of liquids with good wetting powers, but has the opposite effect with liquids with poor wetting powers. Measurements were made of thecontact angles formed on individual hairs of Arctia caja larvae by spray droplets. The contact angles formed on these hairs by plain liquids were strongly correlated with the angles formed on smooth Tenebrio cuticle or on an artificial beeswax surface; but there was only very rough correlation between the three sets of data when aqueous solutions of wetting agents were tested.

The test liquids included saturated and unsaturated hydrocarbons, mineral oils with varying aromatic contents, organic esters, alcohols and aqueous solutions. Among the hydrocarbons, members of the aliphatic series wet insect cuticle more readily than the aromatic group. The aromatic contents of the oils did not, however, affect their very high wetting powers.

The effects of adding surface active agents to aqueous sprays were investigated. Of the samples tested, the most effective wetting agents were those with neutral un-ionised molecules.

Hofmannophila pseudospretella is widely distributed in this country. It is a minor pest of stored foodstuffs, clothes and furnishings, and under certain conditions may give rise to a major infestation.

The egg stage is characterised by a high sensitivity to temperature and almost complete indifference to humidity. The incubation period varied from 110 days at 10°C. (90 per cent. R.H.) to 8·5 days at 27°C. (90 per cent. R.H.) and from 9·8 days at 90 per cent. R.H. (25°C.). to 14·0 days at 8·5 per cent. R.H. (25°C.). The percentage survival was greatly reduced both at very low (<3 per cent. R.H.) and at very high (100 per cent. R.H.) humidities. The survival of eggs from a single female varied from 56 to 97 per cent. under favourable conditions.

The duration of the feeding larval stage varied between 145 days at 13°C. and 71 days at 25°C. (at 90 per cent. R.H. on middlings). Larvae failed to mature below 80 per cent. R.H. at all temperatures. Larvae were reared successfully on a wide range of diets of both animal and vegetable origin, some predominantly carbohydrate, some almost entirely protein. The most rapid development occurred on dead adults and the slowest upon leather and yeast.

Under most conditions fully grown larvae entered diapause. This was characterised by a diapause moult after which the larvae assumed a typical diapause appearance. The length of the diapause was extremely variable and was determined largely by the temperature during larval growth. Larvae grown at low temperature did not enter diapause when incubated at 25°C. as fully grown larvae. The diapausing larvae were remarkably resistant to desiccation.

The duration of the pupal stage is affected by temperature but not by humidity. It lasted 98 days at 10°C. and 13 days at 28°C.

The total length of the developmental period was highly variable because of the variability in the length of the diapause under constant conditions. When the conditions throughout were 25°C. and 90 per cent. R.H. the total developmental period varied between 152 and 266 days, and at 20°C. and 90 per cent. R.H. the figures were 192 to 440 days. The developmental period was approximately 12 months under field conditions.

Under crowded conditions, mating was observed between males of H. pseudospretella and females of Endrosis lactella but none of the eggs developed.

The weight of the female at emergence was the most important factor governing the number of eggs laid. Weight of females varied between 8·2 mg. and 43·6 mg. and the egg number between 106 and 657 at 25°C. and 70 per cent. R.H. The number laid was significantly reduced at lower temperatures (10°C.) and at lower humidities (20 per cent. R.H.).

The sex ratio was found to be approximately 1:1, with a slight predominance of females.

The longevity of the fertilised adult female depended upon its weight at emergence and upon the physical conditions. Variation in weights of males was small, and the length of life of mated males could be correlated directly with the physical conditions. The mean longevity of mated females of all weights was 11·9 days at 25°C. and 70 per cent. R.H., 19·0 days at 15°C. and 70 per cent. R.H. and 9·4 days at 25°C. and 20 per cent. R.H. At 25°C. mated males lived 7·1 days on the average, and 18·8 days at 15°C.

The only important predator was the mite, Cheyletus eruditus, which destroyed numbers of eggs and young larvae.

Three interconnecting cages, the largest of which was about 2 feet square, were used in experiments with Anopheles vagus bred from wild-caught larvae.

Variations in the arrangement of these cages showed that:

1. The mosquitos are quiescent by day, if not disturbed, whether kept in the light or in darkness.

2. If they are in complete darkness by night, as in a photographic darkroom, they fly vertically upwards. They will readily escape from a cage about one foot square, with a hold half an inch in diameter in the top, in their continued attempts to fly upwards.

3. They are attracted by a dim light at night and will fly sideways or to a lesser extent slightly downwards, in opposition to the tendency to vertical upward flight. In this way they can pass through openings which they would miss if in complete darkness. Light will not cause them to fly vertically downwards.

4. Anopheles maculatus is less responsive to light under these conditions, than A. vagus.

Using A. vagus, tests were made of the toxicity and residual effect of DDT, BHC and Chlordane as wettable powders on plywood panels. The order of toxicity when fresh was found to be BHC, Chlordane, DDT; the order of the residual effectiveness was DDT, BHC, Chlordane.

A considerable mortality occurred amongst mosquitos surviving the overnight tests with DDT and BHC, if they were kept for a further 48 housrs.

A larger proportion of females was killed than of males, especially by DDT and Chlordane.

BHC was shown to have a marked repellent effect, comparable with that of citronella, but whereas citronella repelled without killing, BHC repelled, but also caused a high subsequent mortality.

A. maculatus was tested once against DDT, and once against BHC in the main series of tests, and was much more readily killed than A. vagus, presumably because of its weaker response to light causing it to remain longer in the main cage in contact with the treated panels.

Methods of approach to the control of I. ricinus by acaricidal action are outlined, and the type of acaricide for the control of ticks on dairy stock is discussed.

Dairy cattle were treated against ticks. Arsenic and carbolic washes were avoided for specified causes. The results of using (i) derris (5·5 per cent, rotenone), (ii) 0·5 per cent. DDT, (iii) DDT in a mixture with pyrethrum, talc or kaolin base, and (iv) pyrethrum (0·9 per cent. pyrethrins I and II) in aqueous solution show that (i) had a greater residual toxicity when applied to cattle, (ii) produced erratic results, which at present do not permit of specific recommendations. When DDT is employed in conjunction with pyrethrum as a powder (iii) the effective duration is low, and this is true also of pyrethrum as an aqueous wash (iv).

Observations have been made on the life-history and habits of C. cilicrura. The flies came to moist, freshly turned soil at all times from April to October, particularly in warm bright weather, but the number of flies seen on observation plots was affected by the area of damp and disturbed soil nearby. Both males and females were attracted and some females laid eggs within a few minutes of their capture. When isolated in phials and fed on dilute sugar solution, captured flies lived up to 79 days. Captured females spent varying periods up to 44 days before laying eggs. The eggs were usually laid in batches of less than ten at irregular intervals over periods extending up to 28 days, and 53 eggs per fly was the highest number recorded. Parasitism by the nematode, Heterotylenchus aberrans Bovien, occurred.

Eggs were found in soil crevices and on vegetation in contact with soil. The observed incubation period was 2–4 days according to the temperature.

The duration of the larval instars was affected by temperature; in captivity, the larval feeding period was 8–16 days in May-June and 15–24 days in October-November. The pupal stage lasted from 16–21 days in May-June and from five weeks to five months in autumn and winter. A few flies emerged during January and February in the insectary.

In captivity first-instar larvae found food buried at a depth of 6 ins. and they were able to reach maturity on fragments of vegetation buried in sand. It is suggested that they are primarily scavengers on organic matter in the soil.

Larvae of P. fugax have been found in the stems and crowns of turnips and swedes, and in cabbages, cauliflowers, lettuces and brussels sprouts. A study of their habitat shows that they occur in decomposing vegetation.

Eggs have been found about various brassicas. Their incubation period was 2–4 days. Larvae were reared in decomposing vegetation. Pupation takes place in the soil and in the feeding sites. Adults have been taken from May to October. The life-cycle from egg to adult occupied 4–5 weeks in spring and the winter was passed in the pupal stage.

A method based upon Yeager's technique is described permitting the study of the surviving heart of Periplaneta americana under varying conditions for several hours.

Rotenone causes diastolic contractions, decrease of frequency and cessation in diastole, threshold <0·0000005 per cent. Presumably it produces an inhibitory action on the neurogenic automatic cardiac centre.

The latent period of the rotenone action is dependent upon the concentration. Using this principle a method is developed for quantitative estimation of the activity of derris preparations.

Tetraethyl pyrophosphate has a strongly accelerating action on the frequency of the heart and increases the amplitude; in this case there is no latent period. Threshold 0·000008 per cent. Presumably TEPP activates the neurogenic heart automatism by its vigorous anticholinesterase activity.

This paper is mainly an account of the known distribution of the 36 species and eight varieties of Phlebotominae found in the Sudan. Their economic importance is briefly discussed.

Regular surveys were carried out from May to July to find out where Jassids live during the cotton close season.

A list of host plants on which Jassids can breed, or feed only as adults, is given; they exhibit preference for certain plants.

The movement of Jassids to cotton was recorded. The initial infestation of cotton is very small but is rapidly built up within the cotton crop. Gardens are shown to be the chief sources of infestation and cotton fields nearest them show larger initial numbers.

Attempts to exterminate Jassids in these gardens by spraying all plants with 0.1 per cent, or 0.5 per cent. DDT emulsion during the summer dead season were not successful. It is thought that reinfestation came from adults which had been present on the tops of Acacia arabica trees and had not been reached by the spray.

The purpose of this note is to illustrate the importance of searching for resting tsetse when making a fly survey. Highly experienced entomologists and fly boys, who are accustomed to making surveys for G. palpalis (R.-D.), G. tachinoides Westw. and G. morsitans Westw., get into the habit of expecting tsetse to be attracted to themselves or to screens or to bait animals, and may easily fail to detect the less common species unless they appreciate that these should be searched for in their resting haunts.

“Gammexane” and DDT, have many advantages over arsenic as tick killing agents. “Gammexane” dips have been used successfully to control the one host arsenic-resistant blue tick, B. decoloratus (Koch) but these dips have not been fully investigated for the control of two- and three-host ticks. The control of the three-host bont tick, A. hebraeum, a vector of “heartwater”, a disease of cattle, sheep and goats, is of great economic importance to South Africa. Larvae and nymphs seem to occur on cattle to a lesser degree than adults, but each stage shows a definite preference for particular sites on the host. For this reason, control measures have to be mainly directed against the adult stage. The effect of “Gammexane”, DDT and arsenical dips, and combinations of these, has been investigated, by making weekly counts of adults on treated and untreated groups of animals. Dipping has been compared with spraying, and the results have been examined in the light of chemical analyses and biological tests with the same samples. The experiments were spread over two consecutive years.

Preliminary experiments indicated that all treatments markedly reduced numbers of male bont ticks on the cattle. Weekly arsenical treatments with 0·16 per cent. As2O3 either by dipping or spraying did not reduce the numbers of females, nor did a composite dip-wash of 0·16 per cent. As2O3 and 50 p.p.m. gamma isomer. Dipping in 50 p.p.m. gamma isomer gave slightly better results against females than the above treatments. Encouraging results were obtained by spraying cattle with freshly diluted wash containing 50 p.p.m. gamma isomer, but dipping in 100 p.p.m. also gave satisfactory results. The relative ineffectiveness of dipping as compared with spraying, was found to be due to the loss of biological activity of hexachlorocyclohexane in dipping tanks, where complicating pollution factors appeared.

The results of the preliminary experiments were largely confirmed by the second series. Males always outnumbered females in collections where the ticks were removed week by week from cattle. The collections were taken to represent the rate at which cattle became re-infested, and formed a basis on which to gauge the effectiveness of treatments. Males increased in numbers week by week on other untreated control groups of cattle, and eventually greatly outnumbered the females. This suggested that males remained on the hosts longer, and were recorded more than once in the consecutive weekly counts.

All treatments reduced the numbers of males. Weekly treatments in 0·16 per cent. As2O3 did not reduce the numbers of females, nor did it prevent them from engorging. Some females laid after removal from cattle so treated but the eggs were sterile, whilst females in a similar state of engorgement, removed from untreated animals, laid fertile eggs. Arsenical treatments should thus eventually control bont ticks.

All “Gammexane” treatments appeared more effective than the arsenical treatments. Fresh dilutions of dispersible pastes and powders in the form of sprays gave better results than dipping in the same preparations at comparable concentrations. This was due to a loss in biological activity of the hexachlorocyclohexane as the washes became dirty with use in dipping tanks. This factor makes chemical determinations of dip-washes, based on total hydrolysable chlorine, of little value, unless these data are correlated with some suitable biological test. The addition of 0·03 per cent, copper sulphate in the wash did not prevent the loss of biological activity.

Oil emulsion dips, which were known to show a drop in the gamma isomer content with use in dipping tanks, were kept at the desired concentration and biologically active by adding fresh dip each week. In such cases both dip- and spray-washes gave satisfactory results when used at 100 p.p.m. gamma isomer. A combination of 50 p.p.m. gamma isomer and 0·16 per cent. As2O3 used as a dip-wash was not satisfactory in reducing the number of bont ticks, and little better than a fresh spray of 50 p.p.m. gamma isomer alone. The striking results given by a combination of a dispersible powder spray of 50 p.p.m. gamma isomer and 0·1 per cent. p,p′ DDT might be due to persistent action or repellent effect.

Arsenic is a stable substance and has been used for many years in dipping tanks to control ticks. It has disadvantages and in the case of the bont tick many females remained attached to the hosts when treated weekly in arsenic, although the engorged females laid sterile eggs. “Gammexane” preparations when used at 100 p.p.m. gave satisfactory results. These preparations, however, lost their biological activity in dipping tanks, and the best results were obtained when they were applied to cattle as fresh sprays.

The wings of male Glossina morsitans appear to become frayed in the rainy season at about the same rate as in the dry season, and their brittleness seems directly related to age. The law of diminishing returns does not appear to apply, perhaps because of the weakening of portions of the trailing edge between indentations fairly near together.

The Gezira Scheme is divided into three areas according to the incidence of the Cotton Jassid, Empoasca lybica.

1. The Northern area of normal abundance.

2. The Central area of occasional abundance.

3. The Southern area of possible abundance.

The causes for this difference in the number of Jassids in the three areas were studied and rainfall in showers over 10 mm. in July and August was found to be the important factor. A definite correlation was found between the number of Jassids on cotton and the amount of this rainfall.

Some experiments were carried out which proved that the effect of rain was due to the splashing of mud from the soil on to the lower side of the leaves. The rain could therefore be effective if it is heavy enough to produce mud splashing.

It was shown by a simple apparatus that mud splashing hardly rises more than 30–40 mm.

The correlation between the number of Jassids and the amount of rainfall in July and August might be used as a basis for forecasting the extent of Jassid attack on cotton every year.

The Epilachninae constitute one-sixth of the known species of the family Coccinellidae. They are herbivorous and include a number of well known pests of cultivated plants in different parts of the world. Their adults present a great uniformity of external structure, with the result that nearly all the known species have been placed in one genus, Epilachna Hope. Their identification is made more difficult by the employment of characters such as the elytral markings and spots which may vary a great deal in one species or be almost identical in two quite unrelated species. Lately, there has been a tendency to split the genus by employing more reliable morphological characters, including genitalia. A greater knowledge of the biology and morphology, including that of the immature stages, particularly the larvae, is necessary to evolve a natural classification. Relatively little was known of the larvae. This paper deals with 14 species belonging to six different genera.

In addition to discussion of the relationship of this subfamily with other Coccinellidae in the light of the extensive larval material examined, it is observed that larvae belonging to different genera, including those recently erected or revived, show considerable morphological differences that support a division of Epilachna (s.l.) based on adult characters. A study of the larvae of nine species that are still retained in the genus Epilachna shows that they are separable into several groups, which may well indicate where further division of the genus may be made.

An account is given of observations made in two rooms of a warehouse during 1945 and 1946. In 1945 fortified flour was stored in a single tier of upright sacks, whilst in 1946 the rooms were empty except for 50 small experimental bags of wheatfeed.

Before the flour arrived in 1945, no insects were found except a few larval Ptinids in a bag of sweepings. Adult Ptinus tectus soon appeared on the sacks of flour and, in one room, the numbers on the sacks increased steadily to 6,000 by the time the flour was removed in November. In the other room, where the ecological conditions were obviously variable, the increase was erratic, but there were 4,500 adult Ptinus on the sacks by the time the flour was removed. The numbers on the experimental bags in 1946 rose from zero to 5,000 by the end of September. The weekly figures varied with temperature, falls in numbers coinciding with colder weather. In both years a steady 30–40 per cent, of the total Ptinus on the sacks or bags were fcund at the bottom except for the early months of 1946 when 80 per cent, were at the base of the bags until April.

In empty premises it was obvious that many adult beetles hid in the fabric of the building, a rough estimate of 150,000 being obtained following the use of traps and marked beetles. There were indications that the main hiding place in this building was at the junction of walls and floor. After the sacks of flour had been removed in 1945, it was estimated that the flour covering the floor of Room 70 contained about 7,000 larvae. These would normally be removed by sweeping and vacuum cleaning, but this treatment left behind about a further 10,000 larvae in the floor cracks of each room. No estimate of larvae inside the sacks was possible, but in eight months in 1946, about 1,500 eggs were laid in each small bag of wheatfeed. An average of at least 300 eggs per day were laid in the room in 1946.

Ptinus tectus has two complete generations a year. All stages may survive the winter so that overlap of generations is complete.

In a stack of sacks of flour, adults are most abundant on the sacks at the edge of the stack especially on those near the corners. Draughts, wetness and sunshine caused local changes of distribution. There was some suggestion that Ptinus preferred to rest upon cotton sacks rather than on jute. Larvae are normally present only in the outer layers of flour in a sack and spin cocoons on the inside surface of the sacking. The adults emerge through the sacking to the outside.

The activity of Ptinus in a warehouse is greatest during darkness. Hence it is fairly continuous in dark premises and periodic in light places. In the latter, beetles emerge from their hiding places at dark and return at dawn. If dark crevices are provided artificially they act as traps, for some of the beetles will use them as daytime hiding places. Activity is reduced by low temperatures but does not stop altogether until it is as low as 2°C.

Two methods are suggested for actual estimation of insect numbers without too much labour. One for estimating the numbers on the sacks is based on the fact that most of the insects are found on outside sacks, and involves the counting of the insects on several representative groups of contiguous sacks. Over half of the estimates made by applying this method to the data from one of the rooms in 1945 were within 20 per cent, of the correct values as indicated by total counts of the population. The combination of traps with the release of marked beetles is suggested for estimating the resident population of empty premises.

A résumé is given of the recommendations hitherto made for the control of the Narcissus flies, Merodon equestris and Eumerus tuberculatus. Nevertheless, the control of these pests still remains a major problem in the British Isles. Laboratory and field experiments on the control of both these species were carried out in 1946 and 1947. In the field trials, dichloro-diphenyl trichlorethane (DDT), benzene hexachloride (BHC) and mercurous chloride (calomel) were included. The DDT and BHC were applied in the form of sprays, at a concentration of 0·5 per cent. suspension in water, over the aerial parts of the Narcissus plants and the surrounding soil on three separate occasions at approximately monthly intervals during the oviposition period, starting on May 10, some two or three days before the adult flies normally appear in the district. The calomel was applied in the form of a 4 per cent. dust on separate occasions during this period.

BHC and DDT were successful in producing a marked reduction in the degree of infestations by both species of Narcissus flies and, of the two insecticides, the former was apparently more effective. Although calomel dust afforded an appreciable protection against attacks by the Large Narcissus Fly, M. equestris, it exercised negligible control of the Small Narcissus Fly, E. tuberculatus, in these experiments. It seems from the results obtained in the present investigations that DDT and, in particular, BHC do provide a much more effective and practical means of controlling infestations of the Narcissus flies than any other methods hitherto tested.