♀ ♂. Black; head (including palpi), all legs (including the coxae, but excluding the feet which are strongly darkened), tegulae, and certain portions of the basal joint of the scape, pale red testaceous; the lateral membranous portions of the 1st and 2nd tergites, and the basal ventrites, very pale red testaceous; the plate of the 1st tergite only weakly coloured, and of the 2nd not much more strongly so, both probably more rightly describable as pale red testaceous also; 3rd tergite (except laterally and right across apex) also weakly coloured; the flagellum, and certain portions of the scape, brown; wing-veins and stigma brown, and the setae of the wings coloured; apical third of stigma commonly appearing to be to some extent hyaline.

The mosquitos of the Australian region have been extensively studied from the taxonomic aspect, and a number of workers, including Taylor (1914, 1928, 1929, etc.) Mackerras (1926), Cooling (1924), and Hill (1922), have recorded in general terms the types of water in which the larvae of various species are found. With the exception of the work carried out by Hamlyn-Harris (1927–28–30–33), however, no detailed studies have been made of the possible chemical, physical, or biological factors which may limit particular species of larvae to the special type of water in which they develop.

The most important pest species in the Sydney district are probably Culex fatigans, Wied., Aëdes (Ochlerotatus) vigilax, Skuse, Aëdes (Finlaya) notoscriptus, Skuse, Aëdes (Mucidus) alternans, Westw., Aëdes (Finlaya) alboannulatus, Macq., and in restricted localities Aëdes (Pseudoskusea) concolor, Taylor. Of these A. vigilax, A. alternans and A. concolor breed commonly in various concentrations of sea-water. A. concolor was selected for study owing to its strict limitation to a particular habitat, in the hope that some information might be gained as to the factors responsible for this limitation. In addition nothing has so far been published on the bionomics of this species, which is a particularly interesting one from the ecological and physiological aspects. A discussion of the general position with regard to mosquito ecology is hardly necessary here, since numerous authors have given excellent summaries and bibliographies up to the time of publication of their work, and original papers are appearing at frequent intervals. The majority of the work on mosquito ecology, with certain notable exceptions, has so far been carried out by means of water analysis (both chemical and biological) and field observations, correlated with the occurrence of different species of larvae. While it is recognised that any ecological generalisations, if they are to be accepted, must agree with the observed conditions in the field, nevertheless laboratory experiments, in which a single factor only is varied, should yield considerable information. It is mainly along these lines that the present investigation has been commenced. While the information so far obtained as to the factors limiting the occurrence of A. concolor has been largely negative, still it is hoped that the data obtained are of sufficient general interest to warrant publication. The work will be continued if possible over a number of years.

1. The Algerian race of Locusta migratoria, L., although never known to occur in the gregarious phase in nature can be transformed into almost typical ph. gregaria by breeding in crowded cages.

2. Biometric characters of such individuals indicate a relationship of the Algerian race to the subsp. migratoria, but the data are insufficient for a final decision on this point.

3. The rate of embryonic and hopper development in the Algerian race is the same as in the tropical African subsp. migratorioides when bred at the same temperature and relative humidity.

4. The rate of sexual maturation is very much slower in the Algerian race than in the tropical one bred under the same conditions.

An experiment is described in which G. tachinoides in an isolated secondary focus was marked with distinct colours during thirteen successive weeks and the fate of the groups studied by recaptures. The population was known to be declining from moderate density to great scarcity through the dry season and the wastage in the colour groups on the average proved to be 11½ per cent, per diem, rather more, probably, than the wastage in unmarked flies. Following Jackson's method of assessment the population is shown to fall from 6,000 at the end of October to 400 by mid-January. The ratio of the boy-hour rate to these numbers is worked out for each collection and it is found that when the boy-hour rate is above 50 it is not relative to population, but below 50 the rate falls as the population, allowing for the influence of weather on rate of catching.

It is shown that under the conditions of the experiment there is an almost complete change of fly population each 5 or 6 weeks, though an occasional fly may survive 11 weeks. The proportion of male flies in the catches fell with increasing age from an initial 57 per cent, to 23 per cent, in the 6th week and no male fly surviving this period was caught.

During a series of experiments at Rothamsted with the mechanical insect trap described by Williams & Milne (Bull. Ent. Res. 1935, 26, p. 543) it became necessary to make counts of large numbers of insects three or four times a day over periods of several weeks. The following is a description of a device which was designed to facilitate the handling of the insects and to increase the speed and accuracy of the counting.

In 1933, the late Dr. Drysdale Anderson made a series of laboratory experiments at Onitsha, Southern Nigeria, to study the mosquito larva-killing properties of a number of mineral oils and of some mixtures of these oils. For the experiments he used fresh fourth instar larvae of Anopheles costalis, Giles, which is the most common malaria-carrying species in Nigeria; these larvae he obtained from two temporary pools in the bush, which produced large numbers of larvae in wet weather but dried up after a period of 48 hours without rain.

For his experiments Dr. Anderson used plates marked at a diameter of 19-5 cm. (giving a depth of fluid of 2-5 cm.) with 20 to 30 larvae for each plate and one observer for every 3 plates. An experiment consisted of an average of 200 larvae. The oil was applied by discharging 0·65 cc. from a pipette.

It was suggested that confirmatory experiments in the field were required to check the results of these laboratory experiments. This led to the methods described below being devised by us for testing the efficiency of larvicides under conditions as nearly natural as practicable.

To ensure comparability of results we dug our own breeding-pits, each approximately 2 feet by 2 feet square, on low-lying ground where the ground water is very near the surface. The pits were made of such a depth as to contain 8–12 inches of water and are kept under observation for breeding, and when this occurs its intensity is recorded by measuring out a definite number of dips taken along the four sides of the pit and by counting the larvae captured.

For this “dipping” we made our own rectangular dishes of zinc sheeting with sloping sides 2 inches from rim to bottom, 9 inches by 5½ inches in area at rim level, and 8 inches by 4½ inches in area at the bottom. In practice, such dishes collect about 30 fluid ounces at each complete dip.

The form of the Migratory Locust (Locusta migratoria, L.) appearing in swarms in south-eastern tropical Asia, the Malay Archipelago and the Philippine Islands, is usually referred to the subspecies migratorioides (Reiche & Fairmaire) which occurs in tropical Africa. However, even a superficial examination of series of specimens of the gregarious phase is sufficient to show that the Oriental locusts are somewhat different in their size and structure from the African ones. It was, therefore, of interest to compare the two forms biometrically and the results as described below have proved that the Oriental Migratory Locust should be regarded as a subspecies distinct from the African one, as well as from the three other subspecies of Locusta migratoria so far distinguished (Uvarov & Zolotarevsky, 1929).

Berlese's fluid has been known to entomologists for many years as a medium for making microscope mounts of small Arthropods; it has not been widely used, for which its unreliable keeping quality is perhaps partly responsible. It was developed by the late Professor A. Berlese, chiefly as a mountant for mites; apparently he did not publish the formula.

The bionomics of sandflies (Phlebotomus: Psychodidae) have been studied mainly in relation to the diseases they transmit. Comparatively little experimental work has yet been undertaken on the physiology of Phlebotomus in the laboratory. In the present paper experiments are described on the thermal limits of Phlebotomus, on the influence of temperature and humidity on the length of life of adult sandflies and on the loss of water in larvae and pupae. The problem of loss of water in sandflies is of particular interest, since adjustment to a varying humidity under natural conditions appears to be an important factor in the transmission of diseases by these insects.

For the study of sandflies in the laboratory an ample supply of insects raised under uniform conditions is required. In a previous publication (1934) a breeding method has been described which provides any desired number of sandflies. If overcrowding of the breeding pots is prevented the flies are relatively uniform.

The species used in the experiments was Phlebotomus papatasii, the common sandfly of the Mediterranean, which is the most suitable species for laboratory work; it is comparatively easy to breed and to handle and feeds readily in captivity. The sandflies used in the experiments were bred from females caught in October in Jerusalem. The pots containing the larvae were wrapped in moist cottonwool and survived the transport to London without any damage. The work was commenced, and parts of it completed, in the Department of Entomology, London School of Hygiene and Tropical Medicine, where I held the Avebury Studentship. It is a pleasure to acknowledge the help received from Professor P. A. Buxton and the valuable collaboration of Mr. J. D. Gillett. The work was completed in Jerusalem.

1. There is considerable seasonal variation in the longevity of G. submorsitans and G. tachinoides, and these variations are negatively correlated with the fluctuations in the maximum temperature curve, i.e., as the temperature rises longevity decreases, as the temperature falls so longevity increases.

2. The cycle is as follows:—The rains commence and temperature falls, longevity increases and remains high throughout the rains. The wet season ends, temperature rises and longevity descreases. The cold spell intervenes and longevity becomes maximal. The cold weather ends, the temperature soars up and longevity becomes minimal, remaining low until the new rains commence.

3. Maximum temperature is considered to be the dominant factor; favourable humidity cannot increase longevity unless the maximum temperature is favourable.

4. The oldest individuals occur in the rains, but the average longevity is highest in the cold season, when both temperature and humidity are favourable.

5. In both species females tend to live longer than males.

6. In the field G. tachinoides males appear to live rather longer than the males of G. submorsitans.

7. It is doubtful whether wild flies of either species live much more than 2½ to 3 months under the most favourable conditions; it is probable that in the hottest weather longevity is curtailed to a month or less, and that the production of puparia is seriously affected when the rains are late and the hot weather is prolonged.

The present paper is an account of a preliminary reconnaissance, undertaken during the wet season of 1932, of the suspected middle Niger outbreak area of the migratory locust, Locusta migratoria migratorioides, R. & F.

1. Methods of controlling ants invading houses are discussed.

2. Various methods have been tried, particularly against Monomorium pharaonis. The more general methods in use such as syrup baiting and the use of various insecticidal powders and sprays show at best a palliative effect and do not exterminate the pest. Destruction of the nest is effective where it can be carried out.

3. The use of a thallium sulphate-syrup as a poison bait devised by Popenoe has been tried with success against M. pharaonis and A. (Donisthorpea) niger. This inexpensive method is likely to prove useful in places where it is not practicable to find and destroy the nest, which invariably involves considerable structural alterations.

The genus Nysius, Dallas, as pointed out by China (1934), is in some respects the most cosmopolitan of all Hemipterous genera. Two species have been previously described from Australia, of which one, Nysius vinitor, Berg., occurs in every State of the Commonwealth. The other species, Nysius clevelandensis, Evans, is known only from Queensland. Below is described a third species which is apparently confined to Tasmania.

(1) A technique was devised for determining quantitatively the “ spontaneous ” locomotor activity of hoppers of Locusta migratoria migratorioides in terms of the distance travelled in half an hour in a special activity cage in which temperature, light intensity and humidity could be accurately controlled and all stimulation avoided.

(2) All the material used was derived from the same stock, and was kept under very constant and accurately known conditions from the time of hatching.

(3) The activity as measured in this way showed extremely great variation, as would be expected from our knowledge of the periodic character of “ spontaneous ” activity in many animals.

(4) Distribution curves were plotted showing the frequency with which various levels of activity were reached, and these curves were used as a basis for comparing the amount of activity shown under different conditions. In all these curves the mode was at the origin; by far the greater portion of the activity was of a very low order, though high activity occurred occasionally. The hoppers showed about 70 per cent, of their activity in the lowest activity group (0–5 cm./min.). The percentage fell very rapidly to the next group (14 per cent.), and then gradually to the 30–35 cm./min. group (0·6 per cent.), beyond which the records did not go.

(5) Hoppers kept throughout development in a very dry atmosphere showed a lower activity than hoppers kept in a very moist atmosphere.

(6) Differences in the relative humidity of the atmosphere in the activity cage had very little effect on activity. The figures obtained suggested, but did not prove, the following:—

(a) First and second instar hoppers were more active in a wet than in a dry atmosphere.

(b) Hoppers of instars 3–5 showed the greater activity in the humidity which represented a change from that at which they had been kept during development: those reared dry showed greater activity in a moist atmosphere: those reared wet in a dry atmosphere.

(7) The figures suggested that males were more active than females.

(8) Broadly speaking, all the various instars travelled the same distance in the same time. A consideration of the facts relating to size in the various instars led to the conclusion that the younger instars must have a higher rate of automatic nervous discharge than the older instars.

(9) Jumps were hardly ever encountered at a light intensity of 3–4 ft.-cands., though quite a number were obtained at about 20 ft.-cands. These jumps were “ spontaneous.”

(10) The underlying causes of activity are discussed. It is concluded that external stimulation was by far the most potent factor in influencing the amount of activity exhibited, and that it was the crucial factor in the production of the gregarious phase, but that

(11) Previous environmental conditions, especially previous conditions of stimulation, modified both spontaneous and reflex activity by influencing the nervous excitability of the insect; and

(12) Certain “ determining ” stimuli in the present environment affected the form, intensity and threshold of reflex, and, to a lesser extent, of spontaneous activity.

It is known that there is a high mortality in puparia of Glossina submorsitans and tachinoides if they are kept in air which is far from saturation; it seems anomalous that there is no evidence of mortality among puparia in nature at the end of the dry season when the soil in the thickets appears to be quite dry.

Experiments are described, showing that the soil of the thickets (unlike the more sandy soil of the open country) will take up large quantities of water; as its colloid content is high, this soil must also possess great power of retaining the water. Moreover even when the soil seems quite dry (water content 4 per cent.) the atmosphere in the soil spaces is very nearly saturated.

Oil has been used as a mosquito larvicide for about forty years, since L. O. Howard in 1892 first recommended its use, and a large literature has accumulated on the subject, but the physical and chemical properties which make an oil a suitable material for this work are very imperfectly understood. It is clear that the problem is one that can very favourably be studied in the laboratory, for it requires above all an answer to the question “How do larvae die under oil treatment?” which can only be answered by microscopic examination of the larvae.

The work which is described in this paper was undertaken owing to the conflicting results of standard fumigation practice in Palestine as it existed up to 1932, so that it became evident that the response of the Black Scale to Palestine conditions called for investigation.

Owing to the difference in climate between the Northern Coastal Plain and the Jordan Valley a series of parallel investigations had to be initiated, with the interesting results which Dr. Schweig and Mr. Grunberg have set forth.

There seems little doubt that the growers in the Jordan Valley will have to change from summer to winter fumigation and that in Acre Sub-District even if the double fumigation now under trial is not practicable (and there is no reason wh y it should not be) fumigation will have to be completed by the end of July—otherwise the fruit of the last fumigated groves will be infested before the gangs can reach them. With regard to biological control, this would be pf more value for keeping down the Black Scale population on alternative hosts, such as Eucalyptus groves and roadside trees. Negotiations for the importation of Comperiella bifasciata are in progress, and if this proves possible it will be given a trial in the Jordan Valley and the Coastal Plain.

It is unfortunate that the pressure of other demands on the time of a small staff precluded the investigation of the behaviour of the Black Scale in Jaffa Sub-District, but general observations show that it tends to react more in the manner of the Jordan Valley race than of that of the Northern Coastal Plain.

All the orange-groves between Jaffa and Haifa are heavily infested with Aonidiella aurantii, and it will be interesting to see, in view of the observations on mutual tolerance contained in this paper, whether Black Scale spreading from Jaffa will drive out the Red Scale or fail to make headway agaipst it.

The intimate association between a blood meal and ovulation in all female mosquitos, with the exception of a few (de Buck, Roubaud) has been clearly recognised; but the peculiar manner in which the presence of blood in the stomach can influence the formation of eggs is not understood. Two explanations may be suggested: it may either act as a physico-chemical stimulus to the ovarian follicles, or certain constituents in the blood may furnish some nutrient material for the development of the eggs.