Cotton growing landscapes in Australia have been dominated by dual-toxin transgenic Bt varieties since 2004. The cotton crop has thus effectively become a sink for the main target pest, Helicoverpa armigera. Theory predicts that there should be strong selection on female moths to avoid laying on such plants. We assessed oviposition, collected from two cotton-growing regions, by female moths when given a choice of tobacco, cotton and cabbage. Earlier work in the 1980s and 1990s on populations from the same geographic locations indicated these hosts were on average ranked as high, mid and low preference plants, respectively, and that host rankings had a heritable component. In the present study, we found no change in the relative ranking of hosts by females, with most eggs being laid on tobacco, then cotton and least on cabbage. As in earlier work, some females laid most eggs on cotton and aspects of oviposition behaviour had a heritable component. Certainly, cotton is not avoided as a host, and the implications of these finding for managing resistance to Bt cotton are discussed.

Over the past 40 years there have been marked shifts in arable farmland management that are widely believed to have had a considerable impact on flowering plants and invertebrates and the small mammals and birds that rely upon them. It is not yet possible to predict the dynamics of plants and invertebrates either with past or future changes in farmland management. This study investigates whether a basic invertebrate classification, formed of broad trophic groups, can be used to describe interactions between invertebrates and their resource plants and evaluate management impacts for genetically modified, herbicide-tolerant (GMHT) and conventional herbicide management in both spring- and winter-sown oilseed rape. It is argued that the analyses validate trophic-based approaches for describing the dynamics of invertebrates in farmland and that linear models might be used to describe the changes in invertebrate trophic group abundance in farmland when driven by primary producer abundance or biomass and interactions between invertebrates themselves. The analyses indicate that invertebrate dynamics under GMHT management are not unique, but similar to conventional management occurring over different resource ranges, and that dynamics differed considerably between spring- and winter-sown oilseed rape. Thus, herbicide management was of much lower impact on trophic relationships than sowing date. Results indicate that invertebrate dynamics in oilseed rape are regulated by a combination of top-down and bottom-up trophic processes.

We followed lifetime trajectories of reproductive allocation in Coleomegilla maculata females of three different size classes produced by rearing beetles on three different daily larval feeding regimes (30 min, 6 h or ad libitum access to eggs of Ephestia kuehniella). We hypothesized that small females would produce fewer and smaller eggs than larger females and that reproductive effort would decline with female age. Females were mated with a male from the same treatment and then isolated with ad libitum food for their entire adult lives. Egg size increased over time in all treatments; small females started off laying the smallest eggs, but increased egg size more rapidly than larger females, until all treatments converged on a similar egg size around the 20th day of oviposition. Large females realized a larger proportion of their fecundity early in life, but smaller females increased daily fecundity over time. Reproductive effort (egg mass/body mass) did not decline over 30 oviposition days; it remained constant in large females, but increased among small and medium females, suggesting gradual compensation for larval food deprivation. An increase in egg size with maternal age may be an adaptive strategy to maximize fitness on ephemeral patches of aphid prey, assuming females reproduce in a single aphid outbreak and that offspring produced later in the aphid cycle experience greater competition and risk of mortality compared to those produced earlier. We demonstrate for the first time in Coleoptera that dynamic changes in both egg size and number occur as a function of female age and illustrate that such changes are constrained by larval feeding histories via their effects on maternal body size.

Studies were carried out at Jilaal Moogi, south-eastern Somalia, of the responses of Glossina pallidipes Austen to traps and targets. F3 traps caught three times as many tsetse as a biconical trap. Baiting F3 traps with acetone (released at 5–50 000 mg/h), butanone (10–50 mg/h) or octenol (0·05–5 mg/h) either alone or as mixtures did not affect the catch significantly. The catch was increased by 1·6 times (P<0·05) by releasing a mixture of 4–methylphenol (at 0–2 mg/h) and 3-n-propylphenol (0·04 mg/h), and by four times by releasing a mixture of acetone (500 mg/h), octenol (0·5 mg/h) and the two phenols. Baiting a target enclosed in an electric net with the combination of acetone, octenol and phenols increased the catch only 1·3 times, (P>0.05). Baiting an electric net plus target with natural ox odour increased the catch 1·8 times (P<0·05). A pthalogen blue (peak reflectivity = 40% at 450 nm) target caught 1·7 times as many tsetse as a black target (P<0·01) and a standard blue (reflectivity = 29%) target caught 7·4 times the catch of a yellow one (P<0·001). The results are compared with published data from Zimbabwe, Kenya and Mozambique, and it is noted that the level of response of G. pallidipes in Somalia to host odours is lower than elsewhere.

1. The object of the investigation is the study of possible methods of control of injurious insects in pine areas in Britain, with special reference to bark-beetles and to Myelophilus piniperda, L., in particular.

2. Reference is made to the economic status of the pine beetles in Britain as compared with other countries, and it is pointed out that in this country control measures must be of a more intensive character than in countries where large tracts of natural forest occur.

3. An analysis of the various types of damage caused by Myelophilus is made, and it is shown that although the actual amount of damage caused in any particular year may at the time appear comparatively slight, the effects of successive outbreaks are cumulative, and frequently result in a great reduction in the value of the crop.

4. The occurrence of bark-beetle outbreaks and the conditions under which they occur are briefly described.

5. The factors influencing the pine beetle population are discussed, and it is pointed out that the effects of climatic and physical conditions on the development of the host-plant under forest conditions are of fundamental importance in determining the density of the bark-beetle population in standing pine woods. It is stated that apart from abnormal increase brought about by exceptional breeding facilities as a result of fire, windfall, and felling operations, the conditions favouring the increase of bark-beetles and wood-boring insects in pine forests are considered to be mainly due to exceptionally favourable conditions for vigorous growth during the early stages of the crop's development, resulting in large numbers of trees being suppressed and killed in the pole stage, by rapidly increased shade as a result of the abnormal development of predominant trees. This is inevitable when Scots pine plantations are formed on soils too rich and situations too favourable. On the other hand, exceptionally favourable conditions for bark-beetle development occur when conditions are unfavourable for the healthy development of the crop owing to bad drainage conditions and water-logging of the soil.

6. The effect of overcrowding among the brood is considered to be one of the most important factors in the limitation of the bark-beetle population. Examples of how this factor operates are given and it is shown that the practical application of this factor can be brought about by the limitation of the supply of suitable breeding material.

7. The relative value of various parasites and predators as factors in the control of bark-beetles is discussed.

It is considered that pathogenic organisms are of little importance in the control of bark-beetles, as although these organisms may cause an epidemic when the pest has reached its maximum abundance, the object of our control measures must always be to prevent the bark-beetle population from approaching that stage of density.

Evidence is cited from the literature as to the effects of Nematode worms in reducing the egg-laying capacity of bark-beetles. It is suggested that the difference in the results obtained by various writers may have been influenced by the state of the insects at the time the observations were made, since the state of development of the reproductive organs of bark-beetles varies considerably during different stages, and although they sometimes appear to be shrivelled, they are capable of recuperation after a period of feeding. In any case it is impracticable to utilise Nematode worms in control measures, and it seems probable that their usefulness as parasites of bark-beetles will be neutralised by their effects upon the Coleopterous predators.

A list of the Hymenopterous parasites of pine beetles found during the progress of the investigation is given, together with notes on their relative abundance, and their importance as controlling factors is emphasized.

A list of the Coleopterous predators found associated with the bark-beetles is given with notes on the most important species. It is pointed out that some species of Coleopterous predators are probably more injurious than beneficial owing to the destruction of parasite larvae ; Thanasimus formicarius and Elaterid larvae are examples. On the whole, the Coleopterous predators are considered to be of even greater importance than Hymenopterous parasites as agents in the control of bark-beetles.

The larvae of several species of Diptera are very numerous in the bark-beetle brood-galleries. A list is given of the species which have been identified. Although listed as predators of bark-beetles, these Diptera are regarded as being of greater importance as destroyers of parasite larvae and are therefore being studied with a view to their possible elimination.

The economic status of birds in relation to bark-beetle control is briefly discussed, and it is pointed out that although under certain conditions birds do undoubtedly destroy large numbers of adult bark-beetles, it is probable that this useful work is counterbalanced by the destruction of parasite larvae in winter. On the whole, birds are not regarded as being of importance in the control of pine beetles in Britain.

The effects of competition between different species of bark-beetles is discussed, with special reference to Crypturgus cinereus, Hbst., and its influence in the control of Myelophilus minor.

8. A detailed description is given of some large-scale thinning experiments which have been in progress in the New Forest since 1933.

The scheme on which the experiments are based is the result of observations carried out by the writer over a period of years during which he noted that parasites and predators of the pine beetles are most numerous in young pine stands in the pole stage, previous to the first thinning operations. The conviction was formed that under those conditions a state of biological control existed which might, under favourable conditions, be continued throughout the rotation of the crop. One of the necessary conditions for the maintenance of a permanent resident population of parasites and predators is the presence of a permanent host population. This, in turn, necessitates a continuous supply of suitable breeding material. The density of the host population is largely governed by the quantity of suitable breeding material available, and the requirements of an increasing bark-beetle population demand a corresponding increase in the amount of suitable breeding material from year to year; so long as this increase in suitable breeding material continues, the host population is maintained at a higher level than that of the parasites and predators. When, however, the supply of suitable breeding material ceases to meet the requirements of the increasing bark-beetle population, a point is reached where overcrowding of the brood takes place. The intersection and intermingling of the larval tunnels facilitates the work of destruction by the predator larvae and the balance is, for a time, turned in their favour. The increased density of the host population also favours the increase of the parasites at the expense of the host. Limitation of the supply of suitable breeding material also results in a high rate of mortality among the bark-beetle larvae. The combined effects of the increased parasite and predator population, accompanied by overcrowding in a limited supply of food material, will result in a sudden reduction in the bark-beetle population, which is followed by a corresponding reduction in the parasite and predator populations. It will be seen, therefore, that under natural conditions there is a considerable fluctuation in the rise and fall of the numerical ratio of the host population and that of the parasite and predator population. The time occupied by each cycle may be extended over a considerable period of years, the peak of each host infestation giving rise to a periodic outbreak, corresponding with the period of maximum density of the crop. The automatic opening up of the canopy results in a temporary reduction in the amount of suitable breeding material. Under silvicultural conditions, however, the sudden increase of available breeding material produced when a thinning takes place and the material is allowed to remain on the area provides abnormally favourable conditions for the sudden increase of the bark-beetle population, and an outbreak is precipitated. The occurrence of these outbreaks has led to the popular belief that the remedy lies in what is called “ clean forestry.” In theory, the elimination of all suitable breeding material would solve the bark-beetle problem, but in practice the method is often impracticable when large areas of forest have to be dealt with, as is clearly demonstrated by the frequency with which bark-beetle outbreaks occur as a result of thinning operations.

The object of the experiment was, therefore, to devise a method by which the state of biological control can be continued throughout the rotation, by the provision of the amount of breeding material necessary to maintain a permanent population of hosts which would be kept at a level of economic control by the parasites and predators, and at the same time to bring into practical application the factor of overcrowding as an automatic governor to check any undue increase of the bark-beetle population. The results of the experiments are given in detail, and it is shown that the rate of growth of the crop is a decisive factor.

A scheme is outlined for the study of the use of billets and trap-stems.

Reference is made to operations which tend to upset the balance of insect populations.

Control measures in felling, burnt, and windfall areas are also discussed.

The longhorn beetle Cerambyx welensii is an emerging pest involved in oak decline episodes, whose damage is increasingly reported in dehesa open woodlands. Knowledge of the reproductive biology of C. welensii is a crucial goal due to its new pest status. In this study, we assess the reproductive traits of both sexes in the laboratory (25°C and 60% relative humidity ). In females, body length was 44.9 ± 0.9 mm (mean ± SE), fecundity 132 ± 12 eggs, fertility 70 ± 1 %, longevity 70 ± 3 days, preoviposition period 2 ± 0.2 days, oviposition period 44 ± 3 days and postoviposition period 19 ± 3 days. Fecundity was positively correlated with female size, longevity and oviposition period. Daily fecundity was 3.0 ± 0.2 eggs/day and showed a fluctuating synovigenic pattern with a slight decreasing trend over time. Egg length was 4.24 ± 0.01 mm and egg volume 8.14 ± 0.04 mm3. Egg size was correlated with female size but the relative size of eggs was larger in smaller females. Incubation time was 13.9 ± 0.1 days and hatching did not depend on egg size. Neonate size was positively correlated with egg length. Females were polyandrous (more than 20 lifetime matings) but multiple mating did not increase fecundity, fertility or longevity. In males, body length was 43.7 ± 0.6 mm and longevity 52 ± 3 days. Unlike with females, longevity was positively correlated with male size. Males were polygynous (up to 30 lifetime matings) but mating history did not affect male longevity. Rather to the contrary, long-lived males mated more times because they had more mating chances. Lastly, C. welensii reproductive traits were compared with those other Cerambycidae species and discussed from an adaptive perspective. Our data will be useful to improve management of C. welensii in order to prevent or mitigate its impact in dehesa woodlands and other oak forests.

In order to evaluate the relationships between attacks by the mahogany shoot borer Hypsipyla grandella (Zeller) and host growth and phenology, field trials of Spanish cedar Cedrela odorata and American mahogany Swietenia macrophylla established in Costa Rica were assessed intensively over an 84 week period. Height growth of C. odorata was approximately twice that of S. macrophylla, with mean growth rates of 2.0 and 1.3 cm week−1 respectively. Cedrela odorata displayed pronounced temporal variation in leaf phenology, with a minimum of 51% of trees in leaf during a relatively dry period. In contrast, the minimum proportion of foliated S. macrophylla trees was 87%. No shoot borer attacks were recorded on S. macrophylla until week 50 after the onset of assessments, whereas initial attacks of C. odorata were recorded during week 6. By week 84, the proportion of trees attacked was 74% and 77%, respectively. In both species, attacks were concentrated in seasonal peaks, coinciding with the production of new shoots. Pronounced spatial variation in attack was observed in both species. At week 12, the number of attacks per block in C. odorata was negatively correlated with available calcium concentration (r=0.85, P<0.001), whereas mean height growth of C. odorata was positively correlated with available phosphate concentration (r=0.84; P<0.0001). Significant variation in height to first damaging attack was observed in both species. By the end of the observational period, only 6% of C. odorata and 0.4% S. macrophylla remained undamaged to a height of 3 m. It is suggested that control methods for the mahogany shoot borer should take account of temporal dynamics in attack, and relationship to host phenology. Manipulation of the soil nutrient status may also form part of an integrated approach to pest management.

Three related Aphidius parasitoid species share the same host, the grain aphid Sitobion avenae. Among this parasitoid community, Aphidius rhopalosiphi is the most abundant species in the field. Both the interspecific host discrimination of A. rhopalosiphi towards hosts parasitized by the two other species (i.e. A. avenae and A. ervi) and the interspecific host discrimination of the two other species towards hosts parasitized by A. rhopalosiphi were studied here. Results showed that females of A. rhopalosiphi and A. avenae both discriminated between unparasitized hosts and hosts parasitized by the other species. This discrimination occurred only after ovipositor insertion, suggesting the perception of an internal marker of parasitism. Likewise, females of A. rhopalosiphi and A. ervi were able to discriminate between unparasitized hosts and hosts parasitized by the other species. However, in this combination of species, recognition of parasitized hosts occurred before ovipositor insertion, through an antennal perception, suggesting the presence an external cue indicating parasitism. Hence, interspecific host discrimination in the three Aphidius species is based on internal or external cues, which are used either alone or together. Our results showed that the cues used for interspecific host discrimination depend on the specific identity of the interaction. These differences seemed strongly linked to the way the different species respond to defensive behaviours of their aphid hosts. Results are discussed in the context of optimal foraging and possible consequences for community structure.

Anopheles gambiae var. melas was first described by Theobald (1903), and at the same time Dutton (1903) recorded the breeding of A. gambiae in seawater. These two observations were not correlated, but most later workers have believed, with Evans (1931), that the melanic pigmentation of the variety was a direct and temporary response to brackish environmental conditions. They have therefore made no effort to distinguish between the two forms.

The rate at which gregarious nymphs of Schistocerca gregaria (Forskål) lose the tendency to form groups after different periods of isolation was measured. There was a marked loss of social grouping after isolation for 24 h. The fall in level of grouping was highly significantly correlated with the number of days the nymphs had been isolated. Further experiments showed that the extent of loss of grouping behaviour could be significantly modified by the length of time the nymphs spent in crowded conditions before they were isolated, but the density during previous crowding did not have a consistent effect on reduction in grouping. It had been previously considered that S. gregaria nymphs lose very little of their gregarious tendency once it is acquired; this is now shown not to be the case. The behaviour of this species is very responsive to the social environment, whether the locusts are learning to form groups or are losing that tendency.

1. The shore of Lake Chad was suspected of being a reservation of both the Migratory Locust and the Red Lcoust. In 1931 a preliminary survey of the shore was made, as a result of which it was tentatively concluded that about one-half or less of the shore of British Chad may offer conditions suitable for the production of swarms of the Migratory Locust from the solitary phase. The Red Locust was present only in the southern half of the shore. A village named Kalkala, at the south-western corner of the Lake, was selected as the most suitable locality in which to carry out ecological research.

2. The ecology of the two species of locusts and of about 60 other species of ACRIDIDAE was studied at Kalkala during the first six months of 1933. A description is given of agricultural and climatic conditions in the Kalkala area and some notes on the hydrography of Lake Chad are included. The vegetation, soils, fauna and microclimates of the habitats frequented by ACRIDIDAE are described.

3. Collections of Acrididae were made each month in all the principal habitats. It was found that the Acridinae occurred principally in the wettest habitats and that this subfamily exhibited a small degree of ecological plasticity. The Oedipodinae consisted chiefly of geophilous species which were most abundant on bare soil in farm-land. The Pyrgomorphinae were most abundant in two non-gramineous habitats, but were not uncommon in Cynodon dactylon; one species was associated with Calotropis procera. The Catantopinae showed a greater degree of ecological plasticity than did any of the other subfamilies; the majority of the species encountered were most abundant in the drier habitats.

4. Bionomical notes are given for the majority of the species of Acrididae met with in 1931 and 1933 in the Chad area. Evidence was obtained that many species of Catantopinae have a prolonged imaginal diapause. Certain species of Acridinae and Catantopinae are characterised by an embryonic diapause during the hottest months of the year, and one species of Pyrgomorphinae has a nymphal diapause during the early part of the dry season.

5. The Red Locust frequents tall grass habitats from November to the end of April, the adults then gradually move to short grass and farm-land and begin to breed in late June. The imaginal diapause lasts from early October to late July. Biometrical examinations of adults and other data indicate that the Red Locust is in phase transiens (congregans). There is no evidence that swarms have left the Chad area. It seems probable that conditions in this area are unsuitable for the production of phase gregaria.

6. The solitary phase of the Migratory Locust was present in the survey area throughout the six months; it was never numerous and decreased steadily in numbers from January to June in spite of the fact that it was breeding from late February to June. The decrease in numbers is thought to have been due, chiefly, to the attacks of the Carmine Bee-eater and to bush fires.Phase transiens (dissocians) was found until mid-March; there is no doubt that most of the locusts present were derived from the survivors of hopper bands which had been baited or trenched in the autumn of 1932. Swarms arrived in late May and early June and repopulated the area. The principal habitats of the Migratory Locust were Cynodon dactylon, Brachiaria ramosa and Chloris gayana. The scarcity of this species in the southern half of Chad indicated that this area is unlikely to be a reservation; but research over a number of years is necessary to confirm this opinion.

The Garden Chafer, Phyllopertha horticola (L.) is the chief British representative of a type of world-wide pest. The following summary concerns the adult and its reproduction under laboratory conditions.

Adult feeding affects neither the number of eggs produced by the ovaries (productivity) nor the number laid (fecundity). Productivity depends entirely on the amount of fat-body stored away by the third-instar larva before hibernation.

The adult stage lasts about three weeks (3 to 35 days) in both males and females. Starvation shortens the life by a day or two. Females which lay no eggs (barren) are usually short-lived, i.e., they die before oviposition is due to start, and comprise 14 per cent, of the population.

The fat-body is exhausted and the eggs are all matured by about the end of the first half of the adult stage. Oviposition and feeding apparently do not begin until the manufacture of eggs is completed. Individually, oviposition lasts five or six days (1 to 23 days), the more eggs laid, the longer does the oviposition period usually last. The female dies two or three days (0 to 10 days) later. Starved females have a rather shorter oviposition period. Unmated females may lay a few non-viable eggs just before they die.

The average female lays 13 eggs (0 to 46 eggs). More than 70 per cent, of females lay all or nearly all of the eggs manufactured from the fat-body. Apart from barren females, there is no significant difference in length of life between females that lay all of their eggs and those that lay only some.

Females are larger than males, being on the average 1·2 to 1·3 times heavier. Productivity and fecundity are positively correlated with female body weight (which is, of course, proportional to weight of fat-body). Thus regressions may be calculated such as:

F = 0·113W − 6·60

where F = number of eggs laid and W = weight of pupa in milligrammes. Female pupal weights vary from 80 to 310 mg. Body weight is not associated with the occurrence of barrenness. If all individuals always fulfilled themselves, a population would increase eight-fold annually.

There is not the slightest evidence of a fixed oviposition pattern. Four eggs may take nine days to lay while 27 may take only 24 hours. The same number of eggs may take a longer or shorter time to lay in larger or smaller driblets, the numbers of eggs and the intervals between them being apparently quite random.

A female burrows down at a different point each time she has eggs to lay. At each burrowing she deposits her eggs within a radius of one inch from the vertical line passing through her entrance hole on the soil surface. Eggs are laid singly in small cavities about quarter of an inch apart (3/16 to 1 in.).

Eggs hatch out in 4 to 6 weeks at temperatures of 15 to 17°C. Eggs failing to hatch vary between 4 and 28 per cent, of the total laid. They comprise both unfertilised eggs and, to a lesser extent, eggs which have been fertilised but die from other causes. The proportion of unfertilised eggs increases with the age of the female at oviposition.

(1) The methods of breeding larvae of Capnodis are described.

(2) A description of the larva and of its methods of locomotion is given.

(3) A study of the reaction of the larva to external stimuli is presented. It is pointed out that phototropic or geotropic reactions have no influence on the activity of the larva and that it is guided to its food through stereotactic and chemotropic reactions.

(4) The larva can detect roots or twigs from a distance of about 40 cm., and it can distinguish between the odour of various plants.

(5) Of various fruit trees, the odour of stone fruit was most attractive, and of these, almond comes first and apricots second.

(6) After the larva has located the root, and moulted, the sense of smell weakens gradually until it disappears. A comparative morphological examination of the antennae of neonate and mature larvae shows the olfactory organs are not present in the latter, while distinctly developed in the former.

(7) The larva feeds on the bark, tearing off minute particles, which it chews and finally discards.

(8) The tearing off of the fibres is facilitated by a fluid secreted from the mouth of the larva which softens the wood.

(9) Physiological tests show this fluid to contain a cellulose, a pectinase and an amylase.

(10) Development from hatching to pupation at 33° C. lasts about 60 days, at 27° C. about 100 days.

(11) From empiric data it is apparent that the threshold of development is about 18° C.

(12) From measurements and calculations according to the law of Dyar, the larva must moult at least nine times before pupating.

(13) The larvae resist temperatures above 42° C. for eight hours, but die after a few days in such temperatures.

(14) Practical considerations for the fruit grower based upon this study are presented.

The effect of host nutritional quality on spruce budworm (Choristoneura fumiferana (Clemens)) parental and offspring performance was studied using field and laboratory rearing experiments, and foliar chemical analyses. Foliage of balsam fir (Abies balsamea (L.) Mill.), white spruce (Picea glauca (Moench) Voss) and black spruce (P. mariana (Mill.) BSP) was used to rear the parental generation in the field, whereas an artificial diet was used to rear the progeny under laboratory conditions. Important differences in the food quality were provided by the three hosts. Black spruce foliage had higher concentrations of certain monoterpene deterrents and total phenolics, together with stronger seasonal declines in nutrients such as N, P and Mg, compared with the other hosts. We hypothesise that this trend may be related to poor performance and survival of the progeny. Laboratory rearing showed that progeny of parents that fed on black spruce exhibited longer developmental times and greater mortality, and had lower pupal mass than progeny of parents fed on the other hosts. Further, artificial food-fed progeny of insects reared on black spruce reached sixth-instar later, with lower mass, and exhibited higher relative growth rate (RGR) than progeny of parents fed on the other hosts. These results suggest nutritionally-based parental effects. These results also confirmed that the quality of food consumed by the parents can influence the fitness of the next generation.

This paper deals mainly with species of Tanytarsus (CHIRONOMIDAE) at Khartoum, particularly the very common T. lewisi Freeman. These midges are a serious pest there, usually between November and April, causing great annoyance by swarming in vast numbers around lights during the first few hours after sunset and thus interfering with work and pleasure in the riverain area. They are probably responsible for a considerable amount of asthma and other conditions due to allergy. Little information is available about the biology of CHIEONOMIDAE in Africa, so reference is made to the Palaearctic T. mancus Walker, to which T. lewisi is closely related. Studies of Chironomids from the health point of view elsewhere have little relation to the Khartoum problem, but work on Chaoborus (CULICIDAE) is of interest.

The conditions under which these midges occur at Khartoum and the methods of study are described.

At least 26 species of CHIRONOMIDAE, including four of Tanytarsus, occur at Khartoum. The respiratory organs of some pupae are figured, and a key, based on the characters of these organs, is given for some of the species.

Observations on the biology of all stages are recorded, particularly on the vertical movements and drifting of larvae and pupae and the time of emergence. Many larvae and pupae drift downstream at night, and T. lewisi emerges mainly in the early morning.

Some exploratory field trials of larvicides were carried out. The results were inconclusive, and the difficulty of assessing them is pointed out. Thorough control by anti-larval measures would be extremely difficult owing to the large size of the river and the drift of pupae from upstream. It is believed that it might be possible but prohibitively expensive, and would have to be repeated annually, perhaps throughout the midge season. Various protective measures are discussed. It is considered that riverside dwellers who can do so should move inland, and that a barrier of trees parallel to the river would protect houses away from the river front. People who must be near the river in the evening can achieve considerable protection by clearing some vegetation, fogging with insecticide, or using air-cleaning or air-conditioning equipment.

Adult flies from five taxa (Bactrocera carambolae Drew & Hancock (formerly ‘Malaysian A’), B. dorsalis (Hendel) sensu stricto, B. melastomatos Drew & Hancock, B. papayae Drew & Hancock (formerly ‘Malaysian B’) and B. propinqua (Hardy & Adachi) of the Bactrocera dorsalis complex were analysed at 17 enzyme loci using horizontal starch-gel electrophoresis. Eleven loci—aAdh, Ald, Gpd, Ldh, aMdh, cMdh, Me, Pgm, Pgd, Sod-F, Sod-S—were represented by the most common allele in the five taxa. Of these 11 loci, seven showed intraspecific variation in one or more taxa. Among the five taxa, B. melastomatos could be distinguished from the rest by two loci (Acp and Gpi), while B. propinqua could be separated by four loci (Acp, Est-D, Idh90, Pep-C). Bactrocera dorsalis, B. carambolae and B. papayae did not possess any species-characteristic locus/allele, but B. carambolae could be distinguished from the other two taxa by Idh. The proportion of polymorphic loci in the Malaysian taxa ranged from 0.41 to 0.53. Bactrocera propinqua had the lowest average heterozygosity (H=0.05), while that in B. carambolae, B. melastomatos and B. papayae ranged from 0.09 to 0.11. The genetic identity values indicate closest affinity between B. dorsalis and B. papayae (I=0.99), followed by B. caramboiae (I=0.92), B. melastomatos (I=0.84) and B. propinqua (I=0.69). Bactrocera melastomatos showed closest affinity to B. carambolae (I=0.87) and was most distant from B. propinqua (I=0.64).

Ten fertilised female Glossina austeni Newst. reared from pupae with a weight range of 17–33 mg were maintained singly in small cages, and were offered food six days per week. The mean data for the flies were 151 days life span, 14–5 pupae per female and 25–4 mg pupal weight. One fly showed an abnormal digestive condition, and several failed to larviposit at the end of a cycle. The weight of pupae produced was related to the total amount of blood ingested in each normal cycle. A comparison between fertilised and virgin flies indicated that 50% of the blood ingested by the former was for pupal production. Large flies took larger blood-meals and fed less frequently than small flies.

Two experiments on factors affecting the size and composition of catches of tsetse flies, principally Glossina pallidipes Aust., were carried out in 1963 in South Busoga, Uganda. Eight attractants were distributed between eight sites on eight successive days in a Latin square design for each experiment. The attractants comprised two black Zebu oxen and Morris traps covered with ordinary hessian (brown traps) or with hessian dyed black (black traps). Three of the sites were on the edge of a large thicket, two were close to isolated clumps of thicket in the midst of grassland and three were in the open grassland itself. Catching took place for 12 hours each day. The total numbers and sex ratio were recorded for each catch, and also, from dissections, the age composition and pregnancy states of the female portion of the catch. Examples of G. brevipalpis Newst., G. palpalis fuscipes Newst. and of 13 species of Tabanidae were also caught, but in smaller numbers, and were recorded in less detail.

Catches of G. pallidipes at sites close to the thicket edge were considerably greater than at sites away from the thicket, but, apart from an increased proportion of nulliparous females at the clump and grass sites, the composition of the female sample was unaffected by the type of site. The bait-oxen caught larger samples than the traps, but a smaller proportion of females, and these contained a higher proportion of young flies and of flies carrying an egg in the uterus. In comparison with brown traps, black traps caught smaller numbers of G. pallidipes, and a smaller portion of females, but a larger proportion of these were nulliparous. Although the two oxen had been selected for similarity of size and colour, they differed in the samples they attracted: one of them consistently attracted a larger sample of all the common species and, in the second experiment, a larger proportion of females in the samples of G. pallidipes. Most examples of G. palpalis fuscipes were caught at the three edge sites, and all but one example of G. brevipalpis were caught on the bait-oxen.

All examples of the 13 species of Tabanidae caught on the oxen or in the traps were females. Apart from Tabanus par Wlk. they were poorly represented in the trap-catches, and there was no obvious effect of site upon the size of the samples.

In this paper the cockroach, a general name used here to include the commoner species of Periplaneta, Blatta and Blattella, etc., is approached from an economic and medical point of view. Special emphasis is placed on the possibilities of its control by biological methods, and to this end the whole field of its inter-relationships with other organisms in various parts of the world has been carefully surveyed. As a result some 73 parasites, predators and symbionts from such widely diverse groups as the Protozoa, Nematoda, Insecta, Arachnida, the Algae and Bacteria have been reviewed and classified.

The more important parasites, some 25 in number, have been placed along with the chief predators in a group (A) by themselves. Most of the former are members of the Hymenoptera-Parasitica, the more prominent being the Eulophid, Tetrastichus hagenowii (Ratz.), and the Evaniid, Evania appendigaster L., with six of its congeners. Amongst the predators of this group, certain Sphecoid wasps of the genus Ampulex, represented by seven distinct species, take pride of place. In the second big division (B) the individual species are mostly members of the Protozoa, with Endamoeba as a prominent genus, and of the Nematoda, with several genera, most of them in the Oxyuroidea.

The present paper, which is intended to serve as the introductory one of a series on the natural enemies of the cockroach, deals in detail with a very important parasite, namely the Eulophid, Tetrastichus hagenowii.

Solutions of six chlorinated-hydrocarbon insecticides in kerosene have been applied in drops of about 0·02 microlitre (µl.) to adults of Glossina morsitans Westw., 2–5 days old, one day after the first meal. This species is found to be unusually susceptible to this group of insecticides. In order of increasing toxicity they are: DDT and aldrin, γ BHC, dieldrin and endrin, Telodrin (1,3,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-methanophthalan). The LD50 of DDT was 0·0165 µg. (males) and 0·025 µg. (females), that of Telodrin was 0·00062 µg. (males). Susceptibility of the two sexes to DDT, γ BHC and dieldrin did not differ significantly. Two batches of flies tested with an interval of eight months differed by about two times in their response to dieldrin and γ BHC; but the response to DDT was unchanged. This difference was not seasonal.

For practical use, dieldrin is the best and cheapest available insecticide, a fact confirmed in the field. Only Telodrin might replace it.