In 1923, Edwards described under the name of Taeniorhynchus (Coquillettidia) buxtoni four cotype females captured by Buxton in September 1922 at Huleh, Jordan Valley (Palestine). A few years later, some females of the same species (determined by Edwards) were found by Brumpt in Corsica (Galliard, 1928): the Mediterranean and southern distribution of this mosquito was confirmed by the record of Mansonia buxtoni in Syria (Parr, 1943). Lastly, Aitken (1954) captured in Sardinia and Corsica some adults of M. buxtoni and described the structure of the male terminalia. The early stages, however, have remained unrecognised, and we have accordingly been led to make a morphological study of the larva and pupa, the results of which are presented here.

Details are given of the construction of an all-metal form of locust rearing cage which possesses several advantages over the more usual wooden type.

Three methods of chemical control of Melanagromyza phaseoli (Tryon) on bean (Phaseolus) have been investigated, these comprising seed and soil treatments and spraying of the foliage.

Organophosphorus and chlorinated hydrocarbon insecticides have been tested, chiefly as seed soaks, in the control of the pest. Applied in this way, the former gave poor protection, whereas the chlorinated hydrocarbons, especially the cyclodiene compounds, aldrin, dieldrin, endrin and chlordane, gave adequate protection. Reduction of the period of soaking led to better germination of treated seed. When seed-borne diseases were present, soaking in water or insecticidal solution enhanced their incidence. Bean varieties varied in their response to soaking in water or the insecticidal fluids used, the germination of most varieties being adversely affected. Endrin 20 per cent, emulsifiable concentrate (E.C.) used at a dilution of 1:250 as a soak for six hours or at a dilution of 1:125 for three hours or 1:50 for momentary dipping or up to an hour's soaking, gave good germination and protection from M. phaseoli with the climbing bean variety Kentucky Wonder but reduced very considerably the germination of several other varieties.

Where soil was treated with various insecticides for control of M. phaseoli. pre-sowing treatment was more effective in protecting the bean plant from this seedling pest than treatment given after seedling emergence. Soil treatment with endrin did not induce phytotoxic symptoms in those varieties that were adversely affected when the seeds were soaked in emulsified solutions of endrin.

Foliar spraying with DDT 18 per cent. E.C. at one fl. oz. per gal., endrin 20 per cent. E.C. at 0·5 fl. oz. per gal. or parathion 46 per cent. E.C. at 2 ml. per gal. at weekly intervals up to the time of flowering was very effective in controlling M. phaseoli.

The efficient control of the pest obtained with pre-sowing treatment of soil or seed suggests that the insecticides concerned may have been acting systemically. Laboratory studies on the life-cycle of the pest in plants derived from treated and untreated seed show that endrin (which was the only insecticide studied in detail in this way) has a larvicidal effect when used as a pre-sowing treatment.

A number of observations were made on parasites of certain Pentatomoids (sunn pest) attacking wheat in Middle East countries, during the course of other work on these pests. The principal host species studied were Eurygaster integriceps Put., E. maura (L.) and Aelia rostrata Boh. The data concern both Dipterous (Tachinid) endoparasites of the adult bugs, and also Hymenopterous (Scelionid) egg-parasites; the observations were made principally in central Turkey, and in the Varamine district of Iran. A few observations on predators were made also.

The data concerning Tachinids consist of host records for six species of parasites. In no case observed by the author did these parasites appear to be of great importance in reducing the numbers of sunn pest; the same is true of the few instances of predators recorded.

Observations were made on six species of Scelionid egg-parasites (five species of Asolcus and one of Hadronotus), five of which were bred from eggs of four species of Pentatomoid hosts collected in the field. The species concerning which the most comprehensive data were obtained were Asolcus rufiventris (Mayr), A. semistriatus (Nees) and A. vassilievi (Mayr). Egg-parasites are well known to be more efficacious in reducing sunn-pest populations, and A. semistriatus has been extensively used in Iran as a biological control agent. The data obtained enabled some ideas which are of importance for the use of egg-parasites in biological control to be formed and discussed. These concern principally (a) the susceptibilities of different hosts to parasitisation; (b) host selection by parasites; (c) the selection of a species of parasite most suitable for biological control in a particular area.

In tests of acaricides for the control of a Tyroglyphid mite, Aleuroglyphus ovatus (Troupeau), infesting cultures of the oriental rat flea, Xenopsylla cheopis (Roths.), in jars provided with linen covers and containing Purina dog food in sand as the rearing medium, Tedion and Kelthane proved ineffective, but light infestations (100 cc. of medium inoculated with 500 mites) were satisfactorily controlled by chlorobenzilate at 0·2 p.p.m. in the rearing medium or as a 0·05 per cent, solution in acetone painted on to the inner wall of the jar and used to soak the linen cover for three seconds. Heavy infestations (100 cc. medium inoculated with 2,000–3,000 mites) were controlled by chlorobenzilate at 20 p.p.m. in the medium or as a 0·5 per cent, solution applied to both the linen cover and the inner rim of the jar; a combination of both treatments (using 2 p.p.m. and a 0·5 per cent, solution) gave adequate control for 30 days.

The flea larvae were unaffected by 2 p.p.m. chlorobenzilate in the rearing medium; 20 p.p.m. killed larvae, but not adults. Neither stage was affected by treating the linen cover and inner rim of the breeding jar with a 0·5 per cent, solution of chlorobenzilate.

Measures are recommended for maintaining flea cultures free from mites, based on these experimental results and on a year's practice.

Cryptotermes havilandi (Sjöst.) is an important pest of domestic timber in West Africa, and in 1957 a study of certain aspects of its biology was made at Port Harcourt, Nigeria.

The alate is positively phototactic on emergence, and the main flights occur at dusk, between 1800 and 1900 hr. Heavy flights continue until 2200 hr., but few alates can be seen after 0100 or before 1600 hr. There is a peak of activity in the drier months of January and February, but flights take place in every month. Emergence for flight is associated with drier atmospheric conditions.

After a change to negative phototaxis, followed by shedding of the wings, the dealates search for a nest site. Tandem behaviour does not occur. The dealates cannot bore into sound wood, and a hole or crack is essential for colony foundation. The entrance to the hole is sealed with material carried in the gut of the insect, according to a fixed behaviour pattern. Dealates seeking to enter wood prefer holes between one and a half and three millimetres in diameter, and cannot use those of less than one or more than five millimetres in diameter. Preference by dealates for particular species of wood was not shown conclusively. There was no discrimination against wood containing lethal doses of borax or Celcure (a proprietary mixture consisting essentially of potassium dichromate, copper sulphate and acetic acid or chromium acetate).

The rate of egg-production, the incubation period, and the duration of the first three instars are recorded. At the rate estimated, egg-production by a physogastric queen could maintain populations in excess of 3,000. Neoteinics are readily produced in isolation from all but the first three larval instars. They may lay eggs from 35 days onwards, and in their first year have much greater fecundity than primary queens.

The economic applications of the observations and experiments are discussed, together with some factors affecting testing of timbers against termite attack.

Oviposition time (the time from blood-meal to egg deposition) has been investigated in five strains of Aedes aegypti (L.), two being DDT-resistant (from Trinidad and Haiti) and three susceptible (from West Africa (2) and Haiti). All the strains except the two DDT-resistant ones differed significantly from one another in mean oviposition time.

There was a close correlation between mean oviposition time, oviposition period (the over-all period during which eggs are laid) and ‘oviposition light preference’, both the former being greater in the ‘dark-laying’ strains than in the ‘light-laying’ ones. There was a positive correlation amongst four of the strains between degree of DDT-resistance and both mean oviposition time and oviposition period; the fifth, which combined long oviposition time with susceptibility to DDT, was a recently colonised West African strain.

In small mass crosses between two strains differing markedly in mean oviposition time, this character showed no dominance; it appears to be under poly genie control. Evidence is given which indicates that there is no close genetic connection between oviposition time and DDT-resistance. There is also no obvious genetic association between oviposition time and ‘oviposition light preference’.

It is concluded that the observed differences in oviposition time may have come about as a result of DDT selection, but could equally well have been the result of a selective influence exercised by the laboratory environment.

The rate of oviposition of isolated pairs of Tribolium castaneum (Hbst.) on finely divided wheatfeed was measured over the entire adult life at 25°C. and 70 per cent. R.H. It was also measured over a period of seven weeks from the start of oviposition at 30 and 70 per cent. R.H. at 25, 30 and 35°C., respectively, at 70 per cent. R.H. only at 22·5, 27·5, 32·5 and 37·5°C. and at 2 per cent. R.H. at 30°C.

At 25°C. and 70 per cent. R.H. each female laid, on the average, 360 eggs at the rate of 2·5 per day for about one hundred days and then at a decreasing rate for the next hundred days. When this experiment was repeated over a seven-week period, each female laid on average about 3 eggs per day. At 70 per cent. R.H., the optimum temperature for oviposition was about 32·5°C., at which about 11 eggs per day per female were laid over the seven-week period. These rates fell to just over 2 per day at 22·5°C. Only one egg was laid by 15 females at 20°C. At 37·5°C. the rate was about 10 eggs per day initially but it declined to about 3 per day by the end of seven weeks, whereas at lower temperatures the decline in laying was slight. Compared with 70 per cent. R.H., the oviposition rate at 30 per cent. R.H. was almost halved at 25°C., but was only slightly reduced at 35°C. At 30°C. and 2 per cent. R.H., females laid well, averaging over 4 eggs per female per day. The periodic provision of water for drinking at 25°C. and 30 per cent. R.H. depressed oviposition.

The preoviposition period was 2 days at 37·5°C. and increased steadily at lower temperatures to 10 days at 22·5°C. It also varied more between females at low temperatures.

The number of eggs recovered in this work was lower than the number obtained by Park & Frank (1948), who used considerably more food in their oviposition chambers. In this work, some eggs were eaten by the adult beetles. However, the innate capacity for increase of the species calculated on these data is extremely high, and could not be maintained for long because of the cannibalistic habits of this species.

Diparopsis watersi (Roths.) is the principal pest of cotton in the Abyan Delta, West Aden Protectorate, an almost rainless area where the crop is sown in August–September on floodland watered by seasonal streams rising on the Yemen plateau. From December onwards, a large proportion of the pupae formed exhibit a facultative diapause, and adults emerging from these are responsible for infesting the following season's crop, the size of the initial population in which depends upon the extent to which this moth flight is intercepted by cotton in a suitable stage for breeding. When initial populations are low, most of the crop is set before the population has greatly increased by short-cycle breeding, shedding of flower buds and young bolls following attack by D. watersi is slight in relation to natural shedding, and little crop loss is attributable to this boll-worm. When a large part of the moth flight is intercepted, initial populations are high, heavy shedding is caused, and varying degrees of loss ranging up to virtual crop failure can result.

Investigations show that, when land is watered, emergence from diapause pupae is almost completed within six weeks; it is thought that watering reduces soil temperature below the high level that appears to inhibit diapause development throughout the summer. The resulting moth flight is largely spent before flower buds become available and the initial population in the crop is low. When land that was under cotton the previous year is not watered, soil temperatures remain high, and this is thought to account for a delay in emergence until temperatures fall, giving rise to a moth flight extending from November to January. Much of this is intercepted by cotton in a condition suitable for breeding by D. watersi, the initial population is high and heavy losses can result. The annual variation in the volume of the floods results in corresponding fluctuations in cotton acreage, a varying proportion of the previous year's cotton land remaining unwatered. The histories of the four cotton crops 1958–59 to 1960–61 indicate the extent to which infestation of the crop depends on this factor. In a year of poor floods following a large acreage in the previous year, infestations tend to be severe, and, conversely, a large crop following a smaller one the year before is normally lightly attacked. Failure to observe a close season may also promote heavy infestation, since it results in the provision of a food supply for the offspring of the main emergence from diapause pupae, which otherwise would not survive.

Endrin has proved very effective in the control of D. watersi, and Sevin also shows promise, but several applications over the two months following the first flower buds are necessary and it is doubtful whether these could be economic. A close season is essential, and the effects of its violation have been seen in recent years. The available flood water should be used more economically, using a system of area rotation of crops whereby cotton would be followed by another crop and that in turn by a dry fallow. The spring floods, which normally run to waste, could thus be utilised, and this would reduce the incidence of unwatered cotton land.

Solutions of dieldrin, γ BHC, p, p′DDT and Baytex were applied topically to pregnant females of Glossina morsitans Westw. and also, in most cases, to fertilised flies over 21 days old and not noticeably pregnant, to virgin flies over 21 days old, and to males over 18 days old. Pregnant flies required about nine times as much dieldrin as young flies for comparable mortalities, and non-pregnant fertilised flies about four times as much. It was not possible to determine proper regression lines for other insecticides and classes of flies but significant increases in tolerance, as compared with that of young flies, were shown by pregnant flies to γ BHC and DDT, by old virgins to dieldrin and DDT but not γ BHC, and by fertilised flies to γ BHC and DDT. Pregnant flies and virgins showed no increased tolerance to Baytex, and old males showed none to dieldrin, γ BHC or DDT.

These results are discussed in relation to aerial spraying of tsetse habitats and it is suggested that they explain some unexpected past results.

Dieldrin, γ BHC, DDT, Telodrin and Baytex have been applied topically in oil solutions to G. swynnertoni Aust. caught as wild adults. The order of toxicity of these compounds was the same as that to laboratory-emerged G. morsitans Westw. and all were relatively more effective. Wild females were 2–3 times as tolerant of the chlorinated hydrocarbons as the males, and pregnant females required nine times as much DDT as the males. Greater tolerance to Baytex did not exceed the difference in body weights between the sexes. These results confirm those obtained with G. morsitans and are attributed to the increased tolerance to chlorinated-hydrocarbon insecticides shown by females as they age and become fertilised and pregnant.

There is no such increase in tolerance of females to Baytex and the importance of this in planning practical control measures is indicated.

The ecology of four tsetse species of the group of Glossina fusca (Wlk.) was studied near the Ugbobigha field station of the West African Institute for Trypanosomiasis Research in southern Nigeria. G. tabaniformis Westw. and G. nigrofusca Newst. occurred in Lowland Rain Forest and G. medicorum Aust. in forest outliers in Derived Savannah; G. fusca was present in both habitats. Meteorological records showed that the climate in the rain-forest was cooler and more humid than in the forest outliers where, in turn, it was more equable than in the savannah. The distribution of the four species, each with its own range of tolerance, was thought to be largely determined by the climatic conditions within the various habitats.

A fly-round, using a white Zebu ox as bait, had been established in the rain-forest in August 1956; 2,549 fusca-group flies were caught in just over three years, 83 per cent, were G. tabaniformis, 16 per cent. G. fusca and 1 per cent. G. nigrofusca. The number of flies caught on the fly-round declined during the catching period; it is suggested that this was caused by the necessity to kill all flies caught in order to identify them. This disadvantage was overcome in further experiments, in which fusca-group flies were caught from an ox tethered in the rain-forest, and in which all flies caught were marked and released; the proportion of each species in the total catch was known, although the identities of individual flies were unknown. A total of 14,577 fusca-group flies were caught once per day during 22 days in July 1957 (wet season) and 7,694 during 22 days in January 1958 (dry season). G. fusca and G. medicorum, which can be readily distinguished on external characteristics, were caught on an ox fly-round laid out in an area of riverine forest in the savannah and further studies on all species were made in a primitive fly-breeding room at Ugbobigha.

G. tabaniformis was most plentiful in the middle of the rains and scarcest during the dry season. Estimation of the numbers of G. tabaniformis and G. fusca combined, during July 1957 and January 1958, suggested that flies were approximately three times more abundant in the rains. The dry-season decrease was considered to have been caused by the adverse effects of high temperatures and low humidities. Largest numbers of G. tabaniformis were caught in those areas of the rain-forest where the host animals, especially the red river hog (Potamochoerus porcus), were least disturbed by human activity. In both wet and dry seasons there were early-morning and late-afternoon and early-evening peaks in activity of G. tabaniformis. It is incorrect to describe the species as crepuscular in habit; during July 1957 flies of a mixed population composed of approximately three-quarters of G. tabaniformis and one-quarter of G. fusca were caught at a rate of only just less than one a minute even when least active. Activity at night was negligible. Analysis of the sex ratio throughout the day showed that rather more than half of the catch of G. tabaniformis before 0700 hr. and after 1800 hr. were males. During the middle of the day females greatly outnumbered males. On the ox fly-round, 58 per cent, of the catch of G. tabaniformis were females; from the tethered ox, 65 per cent, (wet season) and 70 per cent, (dry season) of the mixed catch of G. tabaniformis and G. fusca were females. The percentage of females amongst flies that emerged from puparia of G. tabaniformis in the fly-breeding room was 57.

The numbers of G. fusca caught on the ox fly-round in the rain-forest were insufficient to provide definite evidence for seasonal fluctuations in population density, although such fluctuations probably did occur. In experiments in riverine forest, 2,547 individuals of G. fusca were caught once per day in July–August 1958 (wet season) and 304 in January–February 1959 (dry season). It is suggested that forest outliers in the savannah at Ugbobigha were a suitable habitat during the wet season but that the high temperatures and saturation deficits in the dry season approached the limit of endurance of the species and prevented larger numbers occupying the habitat; mean length of life was probably much reduced in the dry season. G. fusca in the wet season was nearly equally active throughout the day, with a suggestion of peak activity just before dark. In the severe conditions in the dry season in the riverine forest, activity was negligible between about 1200 and 1700 hr. Analysis of the sex ratio of G. fusca in the wet season showed that the proportion of males increased during the day. In the rain-forest, 44 per cent, of the examples of G. fusca caught on the fly-round were females; in the riverine forest 47 per cent, (wet season) and 40 per cent, (dry season) were females. The sexes emerged from the puparia in equal proportions.

Only 29 individuals of G. nigrofusca were caught on the ox fly-round in the rain-forest, of which only three were females.

Only 120 individuals of G. medicorum were caught in the wet-season experiment in the riverine forest and 36 in the dry season; 54 per cent, were females in the wet season and 42 per cent, in the dry season. The flies were most active early in the morning. The emergence rate (82%) from puparia of G. medicorum in the fly-breeding room was higher than for G. tabaniformis (56·5%) and G. fusca (54%).

The types of habitats occupied by the Nigerian species of the fusca group are described.

Females of Glossina palpalis (R.-D.) were dissected and examined for pregnancy at the Ugbobigha field station of the West African Institute for Trypanosomiasis Research in southern Nigeria between January 1958 and October 1959. Of 2,490 females dissected, 46 (2%) were virgin; 764 (31%) had an egg in utero and 221 (9%) a larva in utero. Highest pregnancy rates were found in months with heaviest rainfall and lowest mean temperature, saturation deficit and evaporation rate.

The pregnancy rate in G. palpalis near Kaduna, in Northern Nigeria, was nearly twice that found at Ugbobigha, the major difference being in the number of females with a larva in utero. It is suggested that in the Ugbobigha area an adverse factor operates in the late egg or early larval stage, causing abortion; this is probably not a direct effect of climate or of insufficient food but may partly be related to the possible inability of females to obtain a blood-meal at just the right stage in gestation. Low pregnancy rates may, at least in part, explain the low densities of G. palpalis commonly found in the forest belt of West Africa, despite the wide distribution of the species in such areas.

Dissections of over 93,000 grass stems obtained by random core-sampling of natural grasslands at a site in Berkshire largely confirm earlier conclusions regarding the associations of different species of dipterous stem borers and grasses. Allowing for the number of stems of each grass species per unit area, the densities of larvae were greatest in Anthoxanum odoratum, Poa and Lolium and lowest in Dactylis glomerata. Oscinella frit (L.) was less abundant than Cetema spp. and Opomyza germinationis (L.); it was not found in D. glomerata but was most abundant in Lolium and Festuca. Sampling showed that overwintering larvae of O. frit suffer at least 50 per cent, mortality between September–December and January–March.

Previous studies have largely concentrated on populations in different species of grasses, but it is advantageous to consider the production of O. frit in terms of short (grazed or regularly mown) grasslands and long grasslands (hay fields, uncut commons and rough grazing); comparisons of figures obtained by core-sampling for larvae and emergence traps for adults indicate a production from short grassland and long grassland of about 11 and under 1 overwintered adult per sq. yd., respectively. Having regard to the greater productivity of common leys, dominated by Lolium and Poa, a national average for the first figure would be 15. There is little increase from generation to generation in grassland populations during the year, in contrast with the situation in oats.

From tentative estimates of the acreages and productivities of the different sources of O. frit in England and Wales as a whole, it is clear that the majority of the adults of O. frit are produced by grasslands in the spring and summer and by the oat panicles in the autumn, the latter population being much the greater. As O. frit is a migratory insect, such a conclusion is especially significant and indicates that during the autumn the ‘ population pressure ’ in the grasslands will be very different to that during other seasons.

The age-composition of mosquitos biting at different times and levels was investigated in Zika Forest, Uganda. The four species studied were Mansonia aurites (Theo.) group (material mainly of actual M. aurites (Theo.) but probably including some examples of M. microannulata (Theo.)), Aedes africanus (Theo.), A. ingrami Edw. and Culex annulioris Theo. In each case the biting cycles of nulliparous and parous females were computed separately.

The material examined came from eleven 24-hour catches made by Dr. A. J. Haddow. Samples were taken at seven levels, at 20-ft. intervals, from the ground to a height of 120 ft. The top of the canopy was at 70–80 ft.

In each species the biting cycles of nullipars and pars were closely similar, both at the preferred level and at all levels combined. In only one case (that of the group of M. aurites) was there a significant and consistent difference in the average age of females at different levels, there being a relative excess of older females above the canopy, as found previously in M. fuscopennata (Theo.). This difference persisted throughout the period of biting activity.

These and other recent findings are briefly discussed. It is concluded that the hypothesis which relates the form of the mosquito biting cycle to the age-composition of the biting population and to the larval habitat of the species concerned cannot be accepted as a valid generalisation.

The work described in this paper forms the final part of an investigation into the biology and breeding of Pieris brassicae (L.) in captivity and concerns the larvae and the pupae.

The larvae of the Cambridge stock used in this investigation were found to pass through five instars in the course of their development at temperatures between 12·5 and 30°C. At the lower temperature, development was completed in 46·5 days and at the higher temperature in 11 days.

The average width of the head capsules in each instar was not affected by the temperature at which the larvae were reared, it showed little variation, and it never overlapped with that of the preceding or ensuing instar and, therefore, provides a certain way of determining the instar of any larva.

At 20°C., isolated larvae and larvae kept in crowded cultures completed their development in approximately the same time—19·6 and 18·8 days, respectively.

The average consumption of food during the whole larval period was determined in two experiments, in which it was found to be 1·42 and 1·29 g. of fresh leaves per g. of larva per day, respectively.

The duration of the pupal period ranged from 7·5 days at 30°C. to about 40 days at 12·5°C.

The adults showed a definite diel rhythm of emergence. When kept at a constant temperature, with a photoperiod from 6 a.m. to 10 p.m., nearly all the insects emerged during the dark period and that immediately following it—actually between the hours of 1 a.m. and 9 a.m. If the photoperiod is displaced 12 hours, the emergence is also displaced by the same amount, to correspond with the new dark period. If, instead of keeping the temperature constant, with the photoperiod 6 a.m. to 10 p.m., it is allowed to fluctuate, as it does naturally in June, the emergence is delayed and instead of occurring in darkness and the early hours of the morning as it does at a constant temperature, it takes place mainly during the morning and the afternoon. When insects, which have been reared at a constant temperature and a photoperiod from 6 a.m. to 10 p.m., are allowed to emerge at a constant temperature, in continuous light, there is very little evidence of a diel rhythm of eclosion but if the insects are kept in continuous darkness they show a definite rhythm of emergence. If the pupae are kept in constant light but the temperature is allowed to fluctuate, most of the adults emerge during the warmer period of the cycle.

Diapause in the pupa of P. brassicae is mainly determined by the photoperiod and the temperature during the larval stages. At 20°C., larvae reared in continuous darkness do not form diapause pupae; as the daily photoperiod increases, the percentage of diapause pupae formed also increases until, at a photoperiod of 12 hours, only diapause pupae are formed. Beyond this point the percentage of diapause pupae again declines until, with a photoperiod of about 18 hours, only non-diapause pupae are formed. At higher temperatures similar trends are observed but lower percentages of diapause pupae are formed at all photoperiods.

In P. brassicae there is no evidence that a short, sharply defined period of a day or two exists in the course of the life of the larvae during which the photoperiod operates to influence diapause.

Non-diapause pupae produced from larvae reared in continuous darkness and from larvae reared in long days (over 15 hours' light) appear to contain a growth-promoting hormone capable of causing the emergence of diapause pupae.

Features of the development of Stomoxys calcitrans (L.) are described, based on observations in Uganda on stocks maintained in laboratory culture at 80°F. and 80 per cent, relative humidity. Eggs hatch within 24 hours of deposition, and the mean viability of 10 random batches was 76·5 per cent. The larvae are about 1 mm. long when newly hatched, reach maximum length (about 11 mm.) in the third (final) instar on the seventh day, and pupate one day later, the puparium being barrel-shaped and about 5 mm. long and 11 mg. in weight. The pupal period is two days. Females mate when six days old and oviposit 1–2 days later. The mean values, for five newly emerged, once-mated females, of total eggs laid, number of batches and duration of egg-laying (in days) were, respectively, 376, 10·6 and 12·2.

To be suitable for breeding of Stomoxys in the field in East Africa, sites require the presence of rotted cattle dung, rotted straw or foliage, and shade. In the dry season, such conditions occur only within cattle enclosures and particularly in the small, grass-thatched structures, provided with straw bedding, that are used for housing calves. In the wet season, suitable breeding conditions occur in open park-land and banana plantations, wherever rotted cattle manure and vegetation occur together.