Three years of research on Eurygaster integriceps Put., and other Pentatomoids associated with cultivated cereals in Middle East countries, covered many aspects of the biology and control of these insects. This report is concerned especially with the overwintering or resting period and certain aspects of the annual life-cycle and physiology of E. integriceps.

Up to now these aspects have been studied mainly in the U.S.S.R., and frequent reference has been made to this work. The main objective in the author's own research has been not to explore fresh fields but rather to ascertain whether conclusions reached by workers in Russia are applicable also in countries of the Middle East.

Typically, E. integriceps spends a relatively short active period in the cereal fields in spring and early summer, and the young adults of the new generation migrate in mid-summer to higher altitudes in the mountains, where they spend a few autumn months in aestivation, followed by a hibernation period during the cold months of late winter; they descend to the fields again in spring. A number of different overwintering areas were visited in Turkey, Iraq and Iran, and two were selected for special long-term studies; one was Karacadag mountain, near Diyarbakir in south-east Turkey, and the other Ghara-agadj mountain, in the Varamine district near Tehran, in Iran.

Some of the ecological characters of these areas were studied, including the vegetation and certain climatic factors; the latter included maximum and minimum temperatures and relative humidity, and were studied more intensively on Ghara-agadj. Special attention was given to the microclimatic conditions under the plants where the insects are actually situated.

Population density has been studied at observation stations at different altitudes in the overwintering areas. Two methods are described for estimating population density in terms of the number of insects per square metre. Certain plants are more suitable for shelter than others, and there is some evidence that different types of plants tend to be used more extensively for shelter in the aestivation and hibernation periods. The distribution of these plants affects local variations in population density.

Monthly estimates of density at different altitudes confirmed that there is a partial downward autumn migration which takes place in October on both Ghara-agadj and Karacadağ. Mortality was also estimated during these counts and found to be highest after aestivation, and to affect males more than females. This differential mortality, and also a difference in migratory behaviour between the sexes, brings about differences in the proportions of males and females at different times and in different places; an account has been given of the changes, both local and over-all, in sex ratio throughout the year, and in most cases the reasons for them can be understood.

Research has been carried out on certain aspects of the physiology of Eurygaster, with particular reference to the fat content and the condition of the internal organs (‘ morphofunctional condition ’) and the seasonal changes which they undergo during the year. Fat content has been extensively estimated by chemical analysis, and morphofunctional condition by dissection. The Russian method of forecasting the strength of invasions by reference to physiological condition is discussed; analysis of population changes on Ghara-agadj (where numbers were increasing) and on Karacadağ (where numbers were decreasing) suggests that the present work supports this system of forecasting in principle, provided it is maintained for long periods and the condition of the population kept under regular observation. Fat analysis has proved a more reliable method than dissection for assessing the physiological condition of the population. This condition is not in itself an adequate criterion for making forecasts, and a summary is given of other factors determining the future population density which should be taken into account.

A technique is described for maintaining colonies of mosquitos belonging to the genus Mansonia, subgenus Mansonioides, which have root-piercing larvae and pupae. The colonies are maintained in the absence of living plants. The females lay their eggs on discs of wet-strength crepe paper floating on the surface of water in small 10 × 6–cm. containers. Sheets of the same paper, 14 × 10 cm., stand vertically in the larval infusion bowls and the larvae attach themselves to, and pupate on, these sheets of paper, which contain air spaces. The papers are changed three times a week and this ensures an adequate air supply for the aquatic stages. The larval infusion is produced by soaking pellets of a proprietary animal-diet (Diet 18) in water, at the rate of 20 g. pellets per 1,500 cc. tap water, allowing to stand 3–7 days and using diluted 1:5 with water. The infusion in each larval bowl is stabilised by a block of turf, and yeast is added three times a week; this ensures a continuous supply of micro-organisms on which the larvae feed. The pupae are removed whilst still attached to the sheets of paper, these being transferred to covered bowls, containing tap water and a turf block, in which the adult mosquitos emerge. Pupal mortality is found to be about 40 per cent. With this technique, monthly production of adults has averaged about 2,000 and 1,300 in two insectaries, but has continued to fluctuate between wide limits. The fluctuations have not shown seasonal periodicity, but the numbers produced per month in the two insectaries are correlated significantly, although the insectaries are managed independently. This may reflect variations in the balance of micro-organisms in the standard nutrient infusions used, which could affect mortality amongst firstinstar larvae.

A method is described by which candidate repellents can be rapidly screened and evaluated by comparing them with a standard repellent or with each other. Mosquitos are confined in a petri dish, of which the top is covered with mosquito gauze and the bottom lined with two semicircular filter papers, one of which is treated with a standard repellent, the other with candidate repellent. The dish is placed in an apparatus through which passes a slow stream of air of standard temperature and humidity. Counts of mosquitos are taken every half minute on and above the two halves of the petri dish, which is jarred after every second count to change the position of the mosquitos. A total of 40 counts is taken, the dish being rotated through 180° after the 20th count. The index of reaction is determined as the mean excess of position records for the candidate repellent over those for the standard one.

The initial effectiveness and the persistence of various repellents have been compared. In tests against Aedes aegypti (L.), the repellency of N, N-diethyl-m-toluamide and of O-chloro-N, N-diethyl benzamide did not differ, but each significantly exceeded that of dimethyl phthalate (DMP). The loss of repellency of DMP with time was approximately linear.

Attention is drawn to various aspects and applications of the method, and to its advantages, particularly for rapid screening of repellents.

Cryptolestes capensis (Waltl) has been reared successfully upon wheatfeed at constant temperatures of 15 to 32·5°C., at intervals of 2·5°C., and 90 per cent. R.H., and at 30°C. and 10 to 70 per cent. R.H. Newly formed adult males were found to weigh more than females bred under the same conditions. Oviposition was investigated at 90 per cent. R.H. and 17·5, 20, 30 and 32·5°C.; the highest rate was at 30°C. It was concluded that 30°C., 90 per cent. R.H. were the optimal conditions of those observed. Comparison with C. turcicus (Grouv.) which occurs in the same habitat as C. capensis, shows that the temperature limits of the former are higher, but that at those temperatures at which both species can breed, there is little, if any, difference between the total duration of the immature stages. At the observed optimum for the two species, C. capensis has a higher innate capacity for increase than C. turcicus. These observations do not account for the rarity of C. capensis in comparison with C. turcicus, and it is postulated that C. capensis is, like C. ferrugineus (Steph.), more susceptible to the harmful effects of high larval density than is C. turcicus.

The ability of the foreign grain beetle, Ahasverus advena (Waltl), a reputed mould feeder, to breed on various foods under conditions not conducive to mould growth was investigated in a series of culturing experiments. At 25°C., on a diet of rolled oats and dried yeast, the lowest relative humidity at which successful breeding occurred was 65 per cent., although a few adults were produced at 60 per cent. R.H. Wheat germ proved a satisfactory food under these conditions and the addition of yeast or germ to cereal products enabled the species to breed in the absence of visible mould growth, which it failed to do on. the cereal products alone. Although thriving larval cultures developed with crushed, dead grain weevils (Sitophilus granarius (L.)) as food, they invariably died out without producing pupae. On oilseeds at 70 per cent. R.H., moderate breeding occurred on groundnuts, which remained free from visible mould, but little or none on copra, cocoa or palm kernels in the absence of mould.

It is concluded that most stored foodstuffs are deficient in some factor, present in adequate quantity in dried yeast or wheat germ, that A. advena requires for successful breeding and that, in the field, this requirement frequently limits the species to mouldy products, although direct damage to groundnuts at 30°C. and 70 per cent. R.H. is possible in the apparent absence of mould.

In a continuation of studies of diurnal and seasonal feeding activity of Glossina pallidipes Aust. in thick riverine vegetation at Rekomitjie, in the Zambezi Valley, Southern Rhodesia, flies attracted to a stationary black ox were allowed to become engorged, then caught, marked and released. More flies fed per day in the late dry season (November), and fewer during the rainy season (February), than at other times of the year. The proportions of females amongst flies feeding, and of marked flies recaptured, were greatest in May (77·6 and 20·0 per cent., respectively) and least in November (59·2 and 7·7 per cent., respectively). The diurnal pattern of feeding activity was similar in all seasons, there being a well-marked peak of activity at or shortly before sunset.

The trypanosome infection rate was obtained by dissecting flies caught near the experimental site and was combined with figures for the number of flies attacking the ox to give an estimate of the seasonal trypanosome risk (mean number of infected flies that fed on the ox per day); this was greatest in November and smallest in February.

From comparison of catches off a moving and a stationary ox, two stationary oxen standing together, and two standing out of sight of one another, in each case one being red and the other black, it appears that colour of the bait-animal is not of great importance as an attractant to G. pallidipes unless a definite choice is presented, when flies show preference for feeding on a dark surface.

In conjunction with an investigation of the diurnal and seasonal feeding behaviour of Glossina pallidipes Aust. in dense riverine vegetation in the Zambezi Valley, Southern Rhodesia, gorged flies caught on a stationary ox were marked and released and their subsequent resting places recorded. Fallen logs, a rot hole, boles and branches were found to be utilised in the late hot dry season (November), but in the rainy season (February), the cool season (May) and the early dry season (August), flies were found almost entirely on branches. Of the total resting flies observed, 89 per cent, were at heights of 0 to 9 ft., but whereas in November 49 per cent, of resting flies were at heights between 0 and 3 ft., only 10 to 19 per cent, rested at this level in the other seasons. The choice of more deeply shaded resting sites in November is thought to be due to a reversal, at temperatures over 35°C., of a normally positive reaction to light. The resting behaviour did not appear to differ greatly between sexes, although females do not move so readily as do males on to sites other than branches.

In November, a diurnal pattern of resting behaviour was noted. A branch type of site was preferred in the early morning, but a shift to the rot hole and boles was evident during the middle of the day, followed by a return to branches in the evening; there was evidence that flies rested in yet another type of site at night. In May, searches from 1930 to 2100 hr. for flies marked with reflecting paint revealed some on leaves and small twigs.

A simple method is described of testing the susceptibility to acaricides of larvae of the cattle tick Boophilus microplus (Can.) in Queensland, Australia, by enclosing them in packets made from rectangular filter papers, folded once and secured along the remaining three sides by spring clips, that had been impregnated with Risella-oil solutions of DDT, dieldrin, or Bayer 21/199 (coumaphos), or with deposits from xylene solutions of Dilan. The response of susceptible engorged adult females to dieldrin was tested similarly. Five out of six experiments showed statistical evidence of repeatability of results in determination of relative DDT-resistance of larvae. There was a slight increase in susceptibility of non-resistant larvae to DDT with increasing age between 7 and 28 days for fresh packets but not for re-used packets. In three out of four tests, re-used packets were significantly more toxic (up to 1·40 times) to susceptible larvae than fresh packets. In one test a loss of toxicity occurred after storage of Bayer 21/199 packets for 23 days. The possible use of this method for measuring resistance in ticks is discussed.

The age compositions of samples of females of Glossina pallidipes Aust., G. palpalis fuscipes Newst. and G. brevipalpis Newst., are analysed by means of a method of age determination based upon the changes occurring in the reproductive system during successive gonotrophic cycles. This method of age determination is described in detail.

Females were sampled by three main methods: in traps, by catching on a bait-animal, and on a fly-round. Some flies were also found as resting flies in the undergrowth.

Trap-caught samples of G. pallidipes were older (i.e.), contained a larger proportion of old flies (and a smaller proportion of young flies) than the hand-caught samples. The bait-caught samples were intermediate in age structure. Correlated with the increasing mean age in the hand-caught—bait-caught—trap-caught series was an increase in the proportion of females carrying third-instar larvae and a decrease in the proportion of those carrying eggs. Results with samples of G. palpalis fuscipes and G. brevipalpis were not so well defined.

The results of dissecting teneral and non-teneral nullipars of G. pallidipes and G. palpalis fuscipes indicate that females of the latter are inseminated some time before they take their first blood-meal, but teneral females of G. pallidipes are inseminated when they come to the host to feed or after they have fed.

The relation of the ovarian method of age determination to Jackson's (1946) wing-fray categories in females of G. pallidipes, and the probable epidemiological importance of the samples, are also discussed.

The toxicities of sprays of some insecticides used against locusts have been determined. The LD50's of γ BHC, diazinon, and dieldrin to both flying and settled adults of Schistocerca gregaria (Forsk.) were between 0·9 and 1·5 times those of the same formulations when applied as a single drop to the abdomen. The toxicity of these insecticides was not affected by the size of the spray droplets when these ranged from about 60 to 250 µ in diameter. The toxicity of DNC, however, was always less by spray application than when applied by micro-drop syringe and was affected by the droplet diameter (droplets of 100 µ being 1·5 times as toxic as those of 200–230 µ) and by whether the locusts were sprayed in flight or when tethered on a card (those in flight being about 1·6 times as susceptible to 100 µ droplets as those at rest). A tentative explanation of this effect is given.

The speed of action of the insecticides was compared and the effects of flight activity on susceptibility to the insecticides when sprayed over the flying insects was examined, but none could be detected by the technique used.