1. The number of egg-tubes and the number of eggs in each tube varies in accordance with the food and the climatic and microclimatic conditions of each habitat. The majority of Siberian grasshoppers have adaptations in the ovaries which enable them to take full advantage of the available heat.

2. In the species possessing 10 or more egg-tubes, their number varies in different parts of the distribution area. It decreases towards the centre of the area with increasing warmth and dryness, and increases towards the colder and more humid margins of that area (e.g., in the Far East and in Western Europe).

3. The potential fertility is more or less stable in different species of grasshoppers, and in the species studied it fluctuates between 84 and 388 eggs per female.

4. There is no correlation between the potential fertility and the abundance of the species in nature, for the greatest fertility is met with in those species which occur but rarely. The injurious (i.e., very numerous) grasshoppers have a medium, or somewhat less than a medium, potential fertility.

5. The actual fertility is greatly dependent on the environment and has a wide range of fluctuation.

6. Lack of food in reservations was observed to lower the fertility of grasshoppers by 30–40 per cent. The parasites (Blaesoxipha spp., Mermis spp.) greatly reduce the degree of fertility of the Siberian grasshoppers. However, the percentage of infestation by these parasites is low, but in the reservations it is somewhat higher than outside. Thus, the actual fertility in reservations is rather lower than outside.

7. The outbreaks of the Siberian grasshoppers are determined by the climatic and microclimatic conditions. The fluctuations in fertility never have any real importance in causing the outbreaks. Lack of food, parasites, predators and diseases are of minor importance; among the latter the main factors are the diseases of the egg-pods, which again depend on the microclimate.

Insects and mites collected within the various sections of a combined flour, oatmeal and provender mill are listed. The mill in question is one of the most northerly in Britain. Notes are given on the distribution, abundance and associations, within the mill, of the species recorded. The economic importance of those considered to be pests is assessed.

The three most important pests were found to be Ephestia kuehniella Zell., Gnathocerus cornutus (F.) and Tribolium confusum Duv. It is suggested that Endrosis sarcitrella (L.), Tipnus unicolor (Pill. & Mitt.) and Cryptophagus cellaris (Scop.) might be included in the list of “ hardy ” insects given by Solomon & Adamson (1955) in their paper on the powers of survival of storage and domestic pests under winter conditions in Britain.

Trials are described with window-trap huts to test residual insecticides against vector mosquitos in Malaya. DDT, BHC and dieldrin were tested as wettable powders against Anopheles maculatus Theo., A. sundaicus (Ednw.) and Culex pipiens fatigans Wied. Some results were also obtained with Anopheles barbirostris Wulp, A. letifer Sandosham and A. umbrosus (Theo.), with species of Culex other than C. p. fatigans, with species of Mansonia, and with Aëdes albopictus (Skuse) and Aë. butleri Theo. All these mosquitos, except C. p. fatigans, are essentially outdoor species which enter houses only to bite, and which feed freely on animals as well as on man.

The validity of the window-trap hut method is discussed. It is concluded that although some mosquitos escape through the entrance louvres, and a treated hut is not quite the same as a treated and occupied room, the kills recorded are a good guide to the kills that may be expected in treated houses.

It is shown that there is usually some reduction, seldom sufficient to be important, in the number of mosquitos entering the huts in the first few weeks after treatment. This is probably due to air-borne particles of insecticide drifting through the louvres and acting on mosquitos waiting to enter.

The effect of treatment on the biting and resting behaviour of the mosquitos varied widely, being due to a combination of the properties of the particular insecticide and the habits and susceptibilities of the different species. Broadly speaking, all three insecticides tended to reduce the proportion of mosquitos obtaining a blood-meal, and the proportion remaining in the hut in the morning. But these tendencies might be modified or quite obscured by particular characteristics of the mosquito species or of the insecticide. Thus, for example, the percentage of A. maculatus obtaining a blood-meal was only reduced by 11 per cent, in the first month after treatment with DDT, compared with a 60 per cent, reduction in C. p. fatigans. It is suggested that perhaps A. maculatus did not touch the treated walls before biting and C. p. fatigans did. This difference applies to other species of Anopheles and Culex, and the average reductions in biting rate for the two genera were 19 and 62 per cent.

As another example, before treatment rather more than half of the C. p. fatigans, an indoor-resting species, remained in the hut; after treatment with DDT, which does not easily kill C. p. fatigans, over 80 per cent, were found in the window trap. By contrast, in the outdoor-resting species, A. maculatus, which is easily killed by DDT, over 90 per cent, were in the window trap before treatment, and fewer after treatment. The effect of DDT (and BHC) was to kill some of the A. maculatus before they could leave the hut, thereby reducing the proportion reaching the window trap to about 70 per cent. There was no reduction in the percentage of A. maculatus reaching the window trap with the slow-acting dieldrin.

Judged chiefly by the effect upon C. p. fatigans, DDT influenced mosquito behaviour mainly by its irritant effect, which persisted after the insecticide was no longer killing. The effect of BHC upon behaviour was due to a combination of irritance and rapid lethal action, but this did not last as long as the effect of DDT. Dieldrin has no irritant effect and it influenced behaviour only by lethal action for a short time while it was fresh; it continued to kill after it was no longer doing so rapidly enough to affect behaviour.

The most important finding was the wide range of susceptibility to the insecticides among the ten species or groups of species tested, and the fact that only two (Anopheles maculatus and A. umbrosus) seemed susceptible enough to be effectively controlled in practice by the fairly heavy doses used (200 mg. DDT, 40 mg. γ BHC or 40 mg. dieldrin) per sq. ft. With A. maculatus (and probably A. umbrosus) the 24-hour kill remained above 50 per cent, for about six months or more. With A. sundaicus (and probably A. barbirostris, A. letifer, Mansonia and Aë. butleri) the 24-hour kill fell below 50 per cent, in from one to four months. With C. p. fatigans (and probably Culex spp. and Aë. albopictus) the kill never reached 50 per cent, with DDT, and was only above 50 per cent, for one to two months with BHC and dieldrin.

A. maculatus was the most susceptible species to all three insecticides and C. p. fatigans the least; the latter was particularly insusceptible to DDT.

Heavier doses of dieldrin might be effective against the less susceptible species, and a dose of 100 mg. per sq. ft. has been found to remain effective for six months against Mansonia.

Except for the trial with light doses, dieldrin gave the best results against all species. When fresh it gave kills as high as or higher than those of BHC, and it remained effective longer than DDT or BHC.

Dieldrin and BHC when fresh gave complete or nearly complete kills of all species, but the rate of decline in the kills with time varied widely, and was quickest with the least susceptible species. With DDT, on the other hand, the rate of decline in the kill seemed to be roughly the same with all species, and it was the initial kill which varied. For the least susceptible group of species this was well under 50 per cent, in the first month, and was only 5 per cent, with one strain of C. p. fatigans; with the most susceptible it was between 80 and j 90 per cent.; it never reached 100 per cent.

Few mosquitos were found dead in treated huts, the great majority escaped into the window traps, especially with the slow-acting dieldrin. With A. maculatus in the first four months after treatment with DDT, only 25 per cent, of those dying in 24 hours were found dead in the hut. With BHC and dieldrin the corresponding figures were 14 and 2 per cent. The immediate kill (total found dead in the hut and window trap in the morning) was commonly less than half of the 24-hour kill. These results clearly show the importance of using window traps and holding mosquitos, if possible for 24 hours, if a reliable estimate of the effect of the insecticides is required.

Light doses (100 mg. DDT, 10 mg. γ BHC or 10 mg. dieldrin per sq. ft.) were tried against A. maculatus; DDT and BHC remained effective for three months, but dieldrin only for one month.

The performance of the insecticides at the higher doses can be characterised by saying that DDT is irritant and persistent, but not toxic enough except to the most susceptible of the species tested. BHC is irritant when fresh, though it kills at the same time; it is very toxic to all species, but does not remain effective long enough except against the most susceptible ones. Dieldrin is slower acting than DDT and BHC, but is non-irritant, very toxic, and remains effective longer; against less susceptible species higher doses than 40 mg. per sq. ft. will be needed. In countries where vector species rest indoors by day, dieldrin may prove particularly lasting because mosquitos will rest on treated surfaces for long periods.

The probable relation is discussed between the kills recorded in our windowtrap huts, and the degree of malaria control that may be expected when houses are sprayed. The kill necessary to control malaria depends to a large extent on how much contact the vector has with the insecticide. If its habits bring it into frequent contact with treated surfaces, a comparatively low kill on each occasion of contact may greatly reduce the population of the vector and suffice to control malaria. But if contact is infrequent, as may be expected with species of Anopheles such as those studied, which rest outdoors and feed only to a limited extent on man, then a high kill on each occasion of entry into treated houses is needed to control malaria, and there may be very little effect on the population of the vector. In these circumstances a 24-hour kill of 50 per cent., which is here considered the lower limit of effectiveness, seems a reasonable figure to adopt.

The mosquito factors which affect the degree of control achieved with residual insecticides can be thought of under three headings: (a) susceptibility to the insecticide, which largely determines the kill on each occasion of contact, and which we have shown may vary widely with different species, and is often quite low; (b) frequency of contact, which depends on habits, as these determine frequency of entry into treated shelters; (c) duration of contact on each occasion of entry, which is important when the insecticide deposit is no longer fresh, and depends mainly on whether the mosquito rests indoors by day and whether it is irritated by the insecticide.

Mature, singing adults of the bush crickets Platycleis intermedia (Serv.) and P. affinis Fieb. are normally separated in the field through differences in habitat preference. At some localities in southern France, nymphs and young adults of the two species occurred mixed together in herbaceous vegetation surrounding barley fields. Occasionally, there was acoustic interference between them, with modification of the song of P. intermedia. This was overcome by P. intermedia moving into the bushes and P. affinis into the barley. Cutting of the barley resulted in an invasion of the P. intermedia habitat by P. affinis so that there was further interspecific acoustic interference. Sheep grazing caused vegetation mosaics, which again created the conditions for acoustic interaction between the two species.

The flight performance of Simulium ornatum Mg. s.l. was measured under laboratory conditions using a simple flight mill. Males and unmated females were flown and the duration, distance and average speed of flight were recorded for adults fed on water only, sucrose, blood & water, or blood & sucrose. On 91% of all test occasions sucrose-fed insects flew but 25% of those on water only did not fly. Feeding flies on 10% sucrose solution markedly improved both willingness to fly and flight performance, and under these conditions maximum duration, distance and average speed recorded were 4.9 h, 4·2 km and 2·84 km/h, respectively. The ratio of average to maximum speed was 0·631 for females and 0·610 for males, with absolute maximum speeds of 3·19 and 2·99 km/h, respectively. Duration and distance flown were well-correlated, speed being the least variable aspect of flight performance measured. The distributions of flight duration and distance flown were skewed such that few insects made long flights. Mean flight performance at different ages was measured; unmated females appeared to retain a high level of willingness to fly throughout the age-range tested (up to 33 days). The longest recorded flight (5·3 h) was made by a female during an overnight experiment. The implications for long-range flight movements by simuliids are discussed.

Transmission of Trypanosma cruzi (Kinetoplastida: Trypanosomatidae) occurs when feces/urine of infected triatomines come into contact with mucous membranes or damaged skin, and this occurs mainly when insects defecate while feeding on the host. Thus, the vector competence of the triatomines is associated with their feeding and excretion/defecation behavior. This work studied for the first time the effect of T. cruzi infection on feeding and excretion/defecation patterns of Triatoma infestans (Hemiptera: Reduviidae). Uninfected and infected fifth-instar nymphs were fed ad libitum and their feeding behavior and defecations were registered during and after feeding. The feeding pattern did not show differences between the experimental groups. However, the infected nymphs began to defecate earlier, defecated in greater quantity and there was a greater proportion of defecating individuals compared to uninfected nymphs. These results show that T. cruzi affected the excretion/defecation pattern of T. infestans in a way that would increase the probability of contact between infective feces and the mammalian host.

Mounting levels of insecticide resistance within Australian Helicoverpa spp. populations have resulted in the adoption of non-chemical IPM control practices such as trap cropping with chickpea, Cicer arietinum (L.). However, a new leaf blight disease affecting chickpea in Australia has the potential to limit its use as a trap crop. Therefore this paper evaluates the potential of a variety of winter-active legume crops for use as an alternative spring trap crop to chickpea as part of an effort to improve the area-wide management strategy for Helicoverpa spp. in central Queensland's cotton production region. The densities of Helicoverpa eggs and larvae were compared over three seasons on replicated plantings of chickpea, Cicer arietinum (L.), field pea Pisum sativum (L), vetch, Vicia sativa (L.) and faba bean, Vicia faba from the plants after oviposition. Plantings of field pea as a replacement trap crop for chickpea under commercial conditions confirmed the high level of attractiveness of this crop to ovipositing moths. The use of field pea as a trap crop as part of an area-wide management programme for Helicoverpa spp. is discussed.

Single-species and mixed-species populations of Tribolium castaneum (Hbst.) and T. confusum Duv. were followed in two experiments. Food (flour) was renewed at various intervals between 30 days and 180 days or was not renewed at all. As the interval between food renewals lengthened, single-species populations of T. confusum became extinct later than populations of T. castaneum, the survivor in mixed-species populations changed from T. castaneum to T. confusum, and the mixed-species populations became extinct later than the single-species populations. When resource is limited, therefore, populations of the two species may persist longer if they compete than if they are husbanded as single species.

A method is presented for quantifying moth area densities in individual crops and average densities over the total crop area. Mortality within the total Heliothis armigera (Hübner) adult population as a result of insecticide applications against larvae on cotton in the Sudan Gezira was found to be very substantial for males and virgin and inseminated females. The level of adult mortality which was previously unknown, was shown to be an important factor in Heliothis control. The relative importance of alternative host crops as source sites of adults which infest cotton was demonstrated. Initially, larval populations built up in groundnut fields between July and early September. Females emerging from groundnut fields colonized sorghum in late August and early September and cotton slightly later. Larval densities found in groundnut and sorghum fields correlated strongly with the average densities of virgin females found 12 days later. Groundnuts provided the most important source of adults. The virgin female population was in turn highly correlated with the remainder of the adult population (males and inseminated females), demonstrating that H. armigera adults attacking cotton within the Gezira are locally produced. Adults were attracted to sorghum in large numbers for feeding and oviposition, but survival there of older larvae (fourth to sixth instars) to the adult stage was only 25% of that in groundnuts. The implications for pest management are discussed.

The geographical distribution in the African Continent of very few of the species of Ixodoidea has been fully determined. Rhipicephalus sanguineus (Latr.) and certain species of Boophilus are known to be widely distributed, while others, such as R. duttoni Neum., have been recorded from only one or two localities. The present study was primarily undertaken to determine the genera and species of ticks occurring in Nyasaland, but it is hoped it will contribute to the wider problems of the distribution in Africa of the several species.

The mean size of the males of the three tsetse species Glossina pallidipes, G. morsitans and G. swynnertoni is negatively correlated with the mean 2 p.m. saturation deficit of 2 months before.

The correlation is highest (—0·90) for G. pallidipes, the largest species, and lowest for G. swynnertoni, the smallest. The variation coefficient of mean vein length also is highest for G. pallidipes and lowest for G. swynnertoni.

The reason for the apparent 2 months' lag in the effect of saturation deficit on size of flies is that the mean male pupal period is 35 days in Shinyanga (23°C.) and the mean age of males measured is 3–4 weeks. If 1 month's lag is tried, the correlation for G. pallidipes drops from —0·90 to —0·32, and with no lag at all it is —0·24. The correlation with maximum temperature of 2 months earlier is insignificantly lowerthan that with saturation deficit; it is —0·79 for G. pallidipes.

Acroclisoides indicus, sp. n. (fig. l).

♂. Head and thorax dark metallic green ; abdomen with bluish reflections ; the short petiole black, the 2nd segment brown or more or less yellow. Antennae brown, scape and pedicel yellow. Mandibles yellowish with dark teeth. Tegulae and legs yellow, only the anterior and posterior coxae (except tip of posterior) green.

In an investigation of the insect fauna of the soil, the obtaining of the insects from this medium has hitherto been a very laborious and tedious process. It has necessitated the crumbling of the soil by hand, and the examination of it in small quantities at a time over sheets of paper. This method is naturally a lengthy one, and in order to facilitate it the apparatus which is now described was designed.

Zanzibar Town is roughly divided into two halves, the European quarter, with the Indian Bazaar, and the native African town, these two districts being separated by a tidal creek. The European quarter (where most of the Government officials and Europeans reside) is on the western side in close proximity to the sea. The periphery of the town is surrounded on the land side by various swamps, all of them potential mosquito-breeding areas during certain seasons of the year, some of them permanent throughout the year.

The vertical distribution of flying mosquitoes was investigated in separate experiments in open savanna and over a fallow field system near Keneba Village in the tidal zone of the Gambia using suction traps located at seven levels (0·1, 0·25, 0·5, 1·0, 2·1, 3·9 and 7·9 m) on a scaffolding tower. Mosquito density declined progressively with height for Anopheles melas Theo., An. pharoensis Theo., An. squamosus Theo., An. ziemanni Grünb., Aedes dalzieli (Theo.), Ae. punctothoracis (Theo.), Culex tritaeniorhynchus Giles and Mansonia spp. Catches of C. thalassius Theo. and C. invidiosus Theo. increased with height to around 1 m and then decreased steadily although the 7·9–m trap consistently captured more C. thalassius than the trap below, presenting a bimodal vertical distribution profile. Flight altitudes of the two most abundant species, An. melas and C. thalassius, declined as the night progressed, but wind speed and lunar phase had no clear or consistent effects on flight levels. A functional relationship between flight altitudes and dispersal patterns of mosquitoes is suggested.

The two ‘forms’ of the Afrotropical shoot-fly Atherigona rubricornis Stein are shown to be good species. A neotype is designated for the true A. rubricornis, which is restricted to tropical Africa. The other form is described as A. triticisp. n. It is widespread in tropical Africa, but is known also from Egypt, where the larvae attack wheat seedlings, Israel and Yemen. Infestation levels of larvae, with maxima between 9% and 32%, indicate that it is a significant pest of wheat seedlings in Egypt.

More adult males of Glossina morsitans morsitans Westw. were caught with hand nets in Tanzania from a man-carried dark screen baited with surrogate female decoys impregnated with synthetic 15,19,23-trimethyl-heptatriacontane (the G. m. morsitans sex pheromone) than from a screen bearing unimpregnated decoys or from a screen alone. A similar pattern was obtained with G. pallidipes Aust., but the variations in numbers of both species caught within and between fly-round sectors were large. Although many G. m. morsitans males attracted to the screens visually were seen to engage in copulatory activity with pheromone-impregnated decoys, none of the G. pallidipes so attracted was seen to do so. It is therefore concluded that catches of G. m. morsitans were not improved by the presence of pheromone-baited decoys on visually attractive screens. Copulatory behaviour was frequently interrupted by other flies and/or the flies flew off as soon as the screen ceased to move. Of the G. m. morsitans males attracted to a baited screen on the back of a slowly moving vehicle, 51% were seen to have alighted on the impregnated decoys and 42% were engaged in copulatory behaviour with the decoys immediately after the vehicle stopped. Copulatory responses of wild male G. m. morsitans to pheromone-impregnated decoys in glass tubes approximated those of laboratory-reared males only after confinement for several hours at low light intensity. Contamination of laboratory-reared male G. m. morsitans with synthetic pheromone elicited prolonged male:male copulatory behaviour. Prospects for the use of the G. m. morsitans sex pheromone in population studies or control programmes are discussed.

A method is described of estimating the total numbers and frequency distributions of adults of the Red Locust, Nomadacris septemfasciata (Serv.), in outbreak areas of hundreds of square miles, based upon counting the numbers that fly up in a two-yard strip in front of a moving vehicle. The method has proved itself valuable for indicating both immediate and future requirements for killing the locusts, but it requires refining for some research purposes.

By this method, the importance has been clearly shown of the process of congregation of scattered adult locusts in forming emigrant swarms that could start a plague. The locusts do not congregate but actually disperse just before laying eggs.

The total population in part (189 sq. miles) of the North Rukwa Outbreak Area (a self-contained area of 253 sq. miles) in Tanganyika Territory has been followed for four years. There are indications that a small migrant swarm contains 5–10 million locusts, that a total population in the whole of the North Rukwa Outbreak Area of 20 million locusts is unlikely to yield a migrant swarm, but that 50 million locusts could readily do so.

In 1953, after poor rains, no natural mortality was detected between July and October by the assessment methods described. In 1957, after good rains, natural mortality of 70–90 per cent. was revealed by the same methods, although the dry season was not fully covered by the assessments.

A key is provided for the recognition of the hymenopterous parasitoids of the African white rice borer, Maliarpha separatella Ragonot, a pest of rice in Africa and Madagascar. Five species are described as new: Braconidae: Chelonus maudae Huddleston, Rhacanotus carinafus Polaszek; Ichneumonidae: Prisfomerus bullis Fitton, Prisfomerus caris Fitton, Venturia jordanae Fitton. The following synonyms are proposed: Goniozus indicus Muesebeck, G. natalensis Gordh and G. procerae Risbec are synonymized with Goniozus indicus Ashmead. Phanerotorna major Brues is synonymized with Phanerotoma saussurei Kohl. Lectotypes are designated for Goniozus procerae Risbec, Rhaconotus scirpophagae Wilkinson and Garouella ovicida Risbec. The known distributions, biologies and alternative hosts of each parasitoid are provided, and their use as biological control agents or components of integrated pest management programmes are discussed.

A series of catches of G. pallidipes Aust. was made in 1½-hr. periods between 0800 and 1830 hr. each day during two experiments carried out in the early wet season (1957) and the late dry season (1958), at Lugala, Uganda, using tethered, small, shorthorned East African Zebu oxen, Morris traps and the standard flyround technique.

Flies were attracted to the oxen in greater numbers in the morning and evening than at midday, the evening increase being marked in the wet season. The daily catches of both sexes on oxen, though starting at much the same level in both seasons, fell to lower levels at the hotter times of day during the dry season and rose only slightly in the evening. Traps, on the other hand, in both seasons caught most females between 1230 and 1400 hr. and least in the mornings. Male flies were trapped in greatest numbers between 1400 and 1530 hr. in the wet season, but only in comparatively small numbers at any time in the dry season, though there was a suggestion of maximum availability between 1100 and 1230 hr. during the latter. During the dry season, catches on the fly-round and on oxen showed a similar periodicity in the case of females, but not in that of males, fly-round catches of which declined from a peak at 0930–1100 hr.