At the time of writing, 1949, field work on mosquitoes has been carried on in Bwamba County, western Uganda, for a period of ten years, with very few intermissions. The topography and vegetation of this area have been described elsewhere (Haddow, 1945a). The main effort has centred round the search for forest vectors of yellow fever, but much work has also been done in native plantations, huts, etc. While genera such asAëdes and Taeniorhynchus have, inevitably, required special attention, records of all mosquitoes encountered have been kept throughout the investigation, whether or not they seemed likely to be involved in the local epidemiology of yellow fever. Certain sections of the work have already been published (Mahaffy & others, 1942; Haddow, 1945a, 1945b, 1945c, 1946 and 1948; Haddow & others, 1947; Haddow & Dick, 1948; Haddow & Mahaffy, 1949), but a great part of it has not as yet been submitted.

Weekly observations on two populations of Culicoides impunctatus Goet. were made in 1948 at Bannachra and Wester Bannachra, near Loch Lomond, throughout the whole of the C. impunctatus season by means of “ sticky ” traps. Each site had an area of 5 acres of which half was composed of woodland and half of moorland. Twenty-two catching stations, each consisting of three traps placed 2 ft., 6 ft., and 10 ft. above the ground were erected on each site, equal numbers being placed in the woodland and moorland. There were therefore 132 traps to be changed weekly and a total of 67,033 Culicoides were trapped of which 65,576 (97·9 per cent.) were C. impunctatus. In 1949 observations were repeated only in Bannachra woodland.

The results have been analysed in the light of two alternatives (1) that C. impunctatus is a single biological entity and (2) that C. impunctatus is composed of two biological races.

When the seasonal effect was eliminated the stations showed very real differences between their weekly catches. Some stations recorded a large catch every week whilst others always recorded low catches. The total seasonal catch at each station was plotted on plans of the two sites and it then became apparent that there were two centres of high C. impunctatus density at Bannachra, one in the woodland and the other on the moorland, whilst at Wester Bannachra there were two foci in the woodland and a very diffuse zone of high midge density on the moorland. It has been shown that the centre of high midge density in Bannachra woodland was associated with a concentrated breeding place which supplied all the adults for the woodland (2½ acres) and moreover this centre remained unaltered in 1949. The importance of these observations on the control of C. impunctatus is discussed.

After the breeding place in Bannachra woods was discovered it became clear that the majority of adult C. impunctatus moved in an eastward direction from the breeding place and very few went westwards. This was attributed to the influence of the prevailing SW. wind. Knowing the centre of breeding in Bannachra woods it was possible to calculate the regression of the midge density on the distance from the breeding site. It was found that there was a linear relationship between the logarithm of the catch and the distance from the breeding site. A useful statistic is the reciprocal of the regression which may be designated as the density coefficient. It is the distance at which the density has decreased to l/10th of its initial value. The density coefficients for male and female C. impunctatus are 62·5 yards and 64·9 yards respectively. An attempt has been made to separate the effects of “ dilution ” and “ mortality ” on the density of C. impunctatus.

The mortality of male and female C. impunctatus is shown to be normally distributed with respect to the logarithm of the distance flown. These distributions are male l·867±0·197 (=73·6 yds. ; 46·8–115·9 yds.) and female 1 ·885±0·197 (=76·7 yds. ; 48·8–120·8 yds.).

From the density/distance formula the average distances flown by male and female C. impunctatus have been calculated. They are 79·0 yards (males) and 81·4 yards (females).

The analysis of the vertical distribution of C, impunctatus revealed that each station had its own definite pattern. The stations sited amidst the birch saplings showed very real differences between themselves which were not related to the ground flora. It is suggested that these are related to the height of the leaf canopy. Evidence was also produced which pointed to the fact that in the oak wood where the base of the leaf canopy was about 20 ft. from the ground, C. impunctatus had a self-imposed “ ceiling ” of little more than 10 ft.

The ground flora was found to have an appreciable effect upon the vertical distribution of C. impunctatus on the moorland. Thus where the ground flora provided only very shallow shelter, i.e., about 6 ins. in depth, equal numbers of adults were captured at each height, but when the stations were sited amongst Juncus sp. or in small sheltered clearings in the herb layer then more adults were caught on the 2-ft. trap. However, the shelter provided by bracken Pteridium aquilinum appeared to be less attractive and there were fewer adults caught on the 2-ft. traps at stations sited in dense bracken than at other moorland stations.

In the woodland the females were slightly more abundant on the 2-ft. trap and the males more numerous on the 10-ft. trap but the differences in distribution, although significant, were small. On the moorland the males were more abundant at 2 ft. and the females at 6 ft.

Although the general pattern was very similar there were highly significant differences between the horizontal and vertical distributions of the two races of C. impunctatus.

Laboratory experiments showed that piperonyl butoxide (PB) is a powerful synergist of pyrethrins in Shell oil P31.

The toxicity of PB alone to different species of insects was determined. Tribolium castaneum was resistant to direct sprays of PB in P31, but appreciably susceptible to films : the toxic action of the films on this species was unusually delayed. Ptinus tedus and Calandragranaria were resistant to films, but C. oryzae somewhat susceptible.

In view of claims that PB makes pyrethrum films more persistent, an experiment specifically designed to reveal such an effect was carried out. This failed to show that PB makes the films any more persistent.

A formula was obtained giving the approximate pyrethrin equivalent of different pyrethrin-PB mixtures applied to T. castaneum as films on filter paper. It was shown, however, that the pyrethrin equivalent of a given pyrethrin-PB mixture could differ according to the method of application and according to the species of test insect.

The Citrus Leaf-miner (Phyllocnistis citrella) has been recorded from plants belonging to several widely differing botanical families.

It is shown that the true food-plants of this pest are the various species of Citrus and Aegle marmelos.

Elephant lemon (Citrus medica), which has comparatively succulent leaves, is the most susceptible species of Citrus, whilst lime (C. aurantiifolia), with its comparatively thick and coarse leaves, is the least susceptible. Aegle marmelos is not of any importance as the attack in this case is negligible.

C. medica should be excluded from citrus orchards as it is of least economic importance, and is highly susceptible to attack. C. limonia, which is usually grown as a hedge around gardens, provides an undisturbed breeding ground for the pest and should as far as possible not be planted around citrus plantations.

The habits and habitations of the natives in the Bwamba lowlands, Uganda, are briefly described.

A series of catches designed to assess the relative importance of the various species of biting insect and of various routes of transference in the transmission of yellow fever virus from the monkey population of the forest to the nearby human population is reported.

The microclimate in a native hut is discussed.

The species of biting insect encountered are listed, the results of the catches given, and the relative importance of the different species and routes assessed by means of indices.

It is concluded that yellow fever virus is most likely to be transferred to the native population by A. (S.) simpsoni in plantations, the infection in this insect being derived from forest monkeys which raid the plantations for food.

A number of leaf-eating insects have been studied with the object of selecting species suitable for rearing in the laboratory.

Four species have proved satisfactory for large-scale rearing throughout the year. These are Plutella maculipennis, Plusia gamma, Diataraxia oleracea and Phaedon cochleariae. A number of species possess certain disadvantages : (1) apparently obligate diapause (Mamestra brassicae, Sphinx ligustri). (2) The same as (1) with the additional disadvantage of lack of food-plant in winter (Lymantria dispar). (3) Uncertain copulation and oviposition (Pieris brassicae). When available, these species may be reared satisfactorily in large numbers.

Mesographe forficalis, Xanthorhoë fluctuata, Lema melanopa and Crioceris asparagi have been reared in relatively small numbers. They possess certain disadvantages but should be satisfactory for large scale rearing at any rate during some part of the year.

At present laboratory rearing of Phlogophora meticulosa, Agrotis segetum, Triphaena pronuba, Aclypea opaca and Athalia colibri is considered impracticable. A number of leaf-eating species, particularly Hymenoptera, which appear to possess suitable qualities for laboratory rearing, have not yet been obtained and studied in the laboratory.

Particular attention has been paid to factors influencing development of leaffeeding insects with the object of determining the conditions under which healthy stocks of uniform resistance can be maintained. The results of experiments on the effect of food-plant, temperature, humidity and illumination are described. Studies on the factors influencing diapause in the various species are mentioned. Descriptions, are given of the rearing techniques that have been developed.

Living specimens of Megarhinus brevipalpis were transported from southern Natal to Johannesburg to establish an insectary-bred colony. The natural habitat of these predatory mosquitos consisted of small isolated patches of sub-tropical forest, in which the rainfall is 40–50 ins. (102–127 cm.) with a mean winter temperature of 64°F. (17·7°C.) and an annual range of 27°–33°F. (15°–18°C). The breeding places were leaf axils of Strelitzia nicolai (a plant resembling a wild banana), small rot holes in trees and larger ones in Strelitzia stumps. The larvae were collected from leaf axils with an apparatus consisting of a rubber bulb to which were attached lengths of glass and rubber tubing.

The insectary was a room 9 ft.×8 ft. 6 ins. and 9 ft. high which was kept at tropical heat and humidity. Mating of the adults was observed, copulation being effected while at rest or in flight. Oviposition was usually accomplished in flight but also while at rest on the surface of the water. In the summer time two females, which were tested, laid about 85 eggs each during the month following emergence from the pupa, six or seven days elapsing after emergence before the first oviposition. In the middle of the winter, oviposition (with later generations) became very irregular in spite of the temperature and humidity remaining constant. The adults, which were comparable to those of the natural habitat, were fed on sugar solution, honey and fruit juice. One bred out as a gynandromorph.

When given an abundant supply of larvae of laboratory bred Aëdes aegypti, the life-cycle of M. brevipalpis was normally : egg (incubation), less than two days ; larva, 11–20 days (average 14·5 days) ; pupa, five days. This does not include a small number of exceptional cases in which the life as a fully grown larva was abnormally prolonged (in one case nearly four months) for reasons which are not absolutely clear. The larvae killed from 100 to 200 or more Aëdes larvae during the normal larval life, but many of these were not eaten when the brevipalpis were in the late fourth instar. By a special technique they were also induced to eat dead tissues including minced pork brawn, minced maggots and minced flies. Except for the latter these were not satisfactory foods although there was slow development.

Fourth-instar larvae were kept out of water for three to four weeks (without food), in a damp atmosphere, and afterwards when fed most of them developed normally, but pupation was sometimes suspended for a considerable time. They have been sent by post (out of water) in tubes with damp cotton wool and filter paper.

The egg differed from that of other Megarhinus species in having a crown of projections at one end with a cup-like structure in the centre. The exochorion had roughly hexagonal cells but without numerous tubercles as in other species.

First-instar larvae remained in the egg-shell after hatching when the eggs-were out of water but on a damp surface and in a saturated atmosphere. They survived like this for up to six days or about the same time as the larvae survived in tap water if there was no food. When liberated in water the head of the first-instar larva was comparatively small with the mouth parts folded in. Within two hours of liberation in water the head enlarged considerably and the mouth parts came into position ; the larva was then ready to catch its Culicine prey. When in water containing dead leaves, these larvae survived from a few days to over four weeks and some grew to the third instar without any Culicine food.

Cannibalism was investigated. Fourth-instar larvae did not attack each other readily ; they devoured smaller larvae of their own species and small to medium size larvae resorted to cannibalism, particularly in the absence of Culicine prey. There was evidence that fourth-instar Aëdes aegypti occasionally ate first-instar Megarhinus.

The discussion traces attempts which have been made in certain Pacific islands, notably Hawaii and Fiji, to use Megarhines for biological control of disease-carrying mosquitos. M. brevipalpis has a shorter life-cycle than the species introduced into these islands and the conclusion reached is that laboratory breeding, to enable large numbers to be released in certain areas, would be a suitable adjunct to a programme of general control, in this part of the world. Airmail consignments of larvae are being sent to Hawaii with the object of starting a laboratory colony there.

Over 3,000 examples of G. palpalis were age-grouped and dissected for T. vivax over a period of a year. The incidence of infection throughout was highest in Age-group 3 and lowest in Age-group 1. There was a marked seasonal fluctuation, the incidence being highest during the months of heavy rainfall, i.e., August to October, and lowest in the driest.

It has been suggested that the rise in the rate of infection during the rains is merely due to the increasing average age of the fly population, but by the method of age grouping it is shown that this is not the case.

The degree of infection in G. palpalis in Sierra Leone is comparable with that of G. tachinoides in Nigeria.

It is not thought that the seasonal variation in the incidence of infection can be ascribed to changes in the type and abundance of food. The true cause of the fluctuating incidence of infection like the source of infection is unknown.

The failure to recognize seasonal differences in the rate of infection has led to some important practical misconceptions.

Eurygaster integriceps is a serious pest of wheat in Syria against which various methods of control have been tried.

Laboratory tests with a 0·8 per cent. parathion dust applied at the rate of 0·1 mg./sq. cm. are described.

Three sets of field experiments were carried out with 0·75 per cent. and 0·8 per cent. parathion dust. Applied at a rate of 75 kg. /ha. these were very efficient but not economical. Applications of 0·8 per cent. dust with a knapsack duster at between 15 and 17·5 kg. /ha. gave about a 20 per cent. reduction in the infestation. A larger experiment in which 0·75 per cent. dust at a rate of 48 kg. /ha. was applied to a hectare of wheat, by means of a 6 h.p. duster mounted on a Jeep fitted with a drag sheet, gave a 70 per cent. control.

Records are given of the localities (with altitudes) and habitats of 11 species of Diatraea Guild., all reared from known food-plants in northern Venezuela. The larvae of several of these moths are important pests of sugar-cane and maize. Among the eight previously described forms, D. busckella rosa Heinr. is here raised to specific rank, and D. busckella Dyar & Heinr. is treated as a polytypic species, in which typical subsp. busckella has three well-defined forms, two of them, viz., f. falconensis nov. and f. setariaeoides nov., being described, while others are indicated ; the subsp. setariae nov. is also described. The diagnostic characters of D. rosa and D. busckella are discussed and their genitalia are illustrated. The various subspecies and forms of D. busckella are discussed in relation to each other and to D. rosa, these two species being considered as together comprising a supraspecies. Hybrids have been reared in the laboratory among certain of the components.

Three new species, D. andina, D. pittieri and D. silvicola, are described and illustrated, all from northern Venezuela.

The relationship was studied between susceptibility of a number of different species of insects to HCN fumigation and the recovery of HCN from them immediately after fumigation.

The test insects used were Tribolium castaneum, seventh stage caterpillars of Corcyra cephalonica, first-and second-instar nymphs of Drosicha sp., third-and fourthinstar nymphs of Drosicha sp. and adult females of Drosicha sp.

The apparatus and methods used in the fumigation and in the recovery of HCN from the fumigated insects are fully described.

Preliminary expsriments showed that the processes of distillation and redistillation did not affect the recovery of HCN but that the result obtained for recovery from distillation could be affected if some volatile reducing substance were produced and carried over to the distillate. It was found that this did actually take place in the case of one of the test insects—T. castaneum—but that redistillation got rid of the impurity.

In the main experiments it was shown that, on the assumption that the concentration of HCN to which insects are exposed is the effective dosage, the susceptibility of the test insects varied in the following descending order : firstand second-stage nymphs of Drosicha sp. > third- and fourth-stage nymphs of Drosicha sp.>C. cephalonica> T. castaneum>the adult females of Drosicha sp.

When the same insects were arranged in descending order of the quantities of HCN recovered per 100 gm. of body weight, the order was identical except for the nymphs of Drosicha sp. which occupied a different relative position. The two categories of nymphs of Drosicha sp. were found to occupy a different relative position again with regard to the other three test insects when exposed to a superlethal concentration and assessed for recovery of HCN per 100 gr. body weight.

Parallel batches of T. castaneum and C. cephalonica were fumigated and the HCN was recovered from the dead and survivors. More HCN was recovered from the dead insects than from those that survived.

Both recovery and sorption of HCN were estimated separately in parallel batches of insects (adult females of Drosicha sp. and C. cephalonica). Recovery was found to be less than sorption showing that a part of the HCN absorbed is converted into a non-recoverable state. Further, that the weight of HCN sorbed per gram body weight of adult females of Drosicha sp. is much less than in the case of C. cephalonica under similar conditions of fumigation and that the amount of HCN converted into non-recoverable products is less in Drosicha adults than in C. cephalonica.

A comparison of the water content of T. castaneum, C. cephalonica and Drosicha sp. (adults) showed that there was a positive correlation between water content and higher susceptibility to HCN and greater recovery of HCN was also indicated. It is suggested that this may be a factor in the “ Surface Resistance ” of an insec to a fumigant.

The observations of previous workers that larger amounts are sorbed by or recovered (after fumigation) from more susceptible species than for those less susceptible was corroborated by the results obtained with C. cephalonica, T. castaneum and adult females of Drosicha sp. but not with those from nymphs of Drosicha sp.

When dosage-mortality graphs were prepared by taking the amount of HCN recovered per gram body weight as an index of internal dose, the order of resistance of different test insects based on this new criterion was found to be entirely different from that based on the usual criterion of the concentration of HCN in the fumatorium being the index of effective dosage.

These apparently anomalous observations may be explained by assuming that the resistance shown by an insect in an actual fumigation operation, i.e., to the concentration of HCN to which it is exposed (external dose) is what may be called the total “ Effective Resistance ” and that this “ Effective Resistance ” is the resultant of (a) “ Surface Resistance ” to the entry of fumigant and (b) “ Internal Resistance ” to the amount of HCN which actually gains entry into the body in some way or other. Thus the “Effective Resistance ” of an insect may be due to a combination either of low “ Surface Resistance ” and high “ Internal Resistance ”, giving a very low “ Effective Resistance ” as in the case of C. cephalonica, or vice versa giving the maximum “ Effective Resistance ” as in adult females of Drosicha sp. The lower recovery of HCN from the nymphs of Drosicha sp., although they were more susceptible to fumigation than C. cephalonica, is explained by their higher “ Surface Resistance ” combined with a very much lower “ Internal Resistance ”, leading to a lower “ Effective Resistance ”.

The breeding-place of Simulium neavei Roub. has remained undisclosed, despite many attempts to discover it, ever since Dr. S. A. Neave first collected the females in 1911. In May of that year Neave made collections near the Yala River, Kenya, and in November of the same year caught more specimens in Western Ankole, Uganda. Roubaud described and named the species in 1915. Dry in 1921 captured some specimens feeding on man at Ngoina, near Kericho, Kenya, and made the important observation that the local natives connected the fly with the occurrence of a chronic skin disease in this district which has since been identified as onchocerciasis.

A combination of historical, geographical, and epidemiological studies has given sufficient insight into the ecology of sleeping sickness to enable the main factors influencing the development and spread of an epidemic to be traced.

The evidence shows that in West Africa sleeping sickness is not primarily a disease of the forest, where tsetse flies are most abundant, but belongs essentially to the dry country in the north of the savanna woodland zone, where the earliest occurrences and severest outbreaks have been located.

The first mention of sleeping sickness comes from the upper Niger and dates back to the 14th century. By the beginning of the present century intense though localised epidemics were devastating parts of the Mossi, Grounsi and Lobi country of the upper Volta rivers. At this time the disease was unknown on the coast and of sporadic occurrence only in the forest. A severe trans-Volta epidemic covering 60,000 square miles, developed between 1924 and 1940, but was confined to the north of the inland savanna zone with nothing comparable in the forest.

The epidemic spread in three principal ways : (1) Outwards from original foci of infection because of the dynamic nature of the disease. This produced a concentration of infection around headwaters, a feature characteristic of advanced epidemics. (2) Through the agency of travellers, originally from north to south but subsequently in both directions : a rapid method of spread producing linear distribution of infection along trade routes. The tempo was greatly increased on the pacification and development of West Africa after 1900. (3) A gradual southward shift in the main epidemic zone appears to be resulting from a long-term change in the African climate which is combining with man's activities to produce a southerly extension of xerophytic vegetation types and a regression of forest.

The most important spread was that caused by the trading caravans, more especially the cola traders, who have been coming down to the cola-nut areas in the Ashanti forest from the big markets on the Niger and Upper Volta since the 11th century. The caravans were formerly very large, up to one or two thousand strong, and were frequently made up of Mossi and Grounsi from the territory that was so heavily infected by the beginning of the present century. It is certain that a continuous introduction of infection would have been taking place into the forest ever since trypanosomiasis was prevalent in the north, that is for 100 years at least. And infection has been known in the forest for about that period, yet always to a mild degree, never reaching epidemic form. It has been sought for, because conditions in the forest, with the vector Glossina palpalis in contact with every village and path, appeared to be ideal for the transmission of infection and this drew the particular attention of the early workers from 1908 onwards. But the most that could be found was a threatened epidemic in north-west Ashanti, very significantly centering on the big cola markets which formed the termini for the northern traders.

This historical evidence and the reasoning from epidemiology lead to the conclusion that conditions in the forest are not conducive to the development of epidemic sleeping sickness and that the low state of endemicity found there is maintained by the constant introduction of infection from the true epidemic areas in northern savanna.

From this conclusion arises a practical point of the greatest importance. If the sources from which infection is introduced into the forest could be eliminated the disease there should eventually die out and the tsetse, from the human point of view, would be harmless. Tsetse control in the forest may prove difficult and expensive, and if it is attempted by clearing this might end in the literal destruction of the forest. Such measures would be hard to justify, so many other factors of possibly greater importance than trypanosomiasis are involved, both the intrinsic value of a forest for its products and the wider value through its influence on climate, soil and water.

In formulating a plan for the control of sleeping sickness, the habits of both vectors, human as well as insect, should be considered. The tsetse plays a major role in the development of the high infection rates characterising the epidemic outbreaks in northern savanna ; the human vector distributes infection from these sources along trade routes and into the forest. The elimination of the disease at its source, in true epidemic centres, which can be most effectively accomplished by eradication of the tsetse, will check the distribution of infections to the secondary areas of lighter infection which could then be cleared up by quite minor control measures or might even disappear spontaneously.

This plan is now in operation in the Gold Coast. The validity of the arguments on which it was based is being shown by the results that are already apparent : the high rates of reduction in the epidemic areas and the pronounced lowering of infection in neighbouring, uncontrolled areas, more particularly in the forest region of north-west Ashanti where it is entered by a trade route coming from the previously heavily infected country.

An account is given of an attempt to estimate changes in the rate of egg laying in a warehouse and in an unheated outbuilding at the laboratory. Small samples of food were placed on pieces of newspaper on the floor, and were renewed regularly, weekly or fortnightly in the warehouse and daily at the laboratory. Larvae were bred from these food samples and counted.

The rate of oviposition was found to depend on temperature, especially in winter, and on relative humidity, especially in summer. It was seldom cold enough indoors, in unheated premises, to prevent oviposition entirely for more than a few days at a time, 5°C. being the approximate minimum temperature for oviposition. It was never so dry at the laboratory that egg laying stopped but this did happen at the warehouse in July, 1946. Free drinking water is necessary for continued oviposition and this was available from rain in both buildings.

Darkness causes an increase in activity and in oviposition and most of the eggs in the foods supplied were laid at night. Foods placed near the daytime hiding places of adults were most used for oviposition.

Cordia macrostachya (Jacq.) R. & S., is a Boraginaceous shrub indigenous to the West Indies, Central America, and northern South America. It was accidentally introduced into Mauritius about 1890, probably from British Guiana, and became a weed of major importance.

A comparative ecological study of Cordia in Mauritius and in Trinidad showed that its invading power in the former island rested upon a profuse production of viable fruits, whereas in Trinidad, where the plant is of no agricultural concern, fruit production was controlled by the combined action of a number of insects. It was accordingly decided to introduce suitable species of these insects into Mauritius.

The first to be introduced was a leaf-eating Cassidid beetle, Physonota alutacea, but as described elsewhere, this introduction, which took place in 1947–48, was not a success.

The introduction of the second species, Schematiza cordiae Barber, and its result, is described in the present paper. This Galerucid is also a leaf-feeder, but it will sometimes feed upon the inflorescences.

Through the agency of the Commonwealth Bureau of Biological Control, air consignments of Schematiza were received between June and September, 1947. Breeding was started, and after feeding tests in both Mauritius and Trinidad had established its specificity to C. macrostachya, the release of laboratory reared adults was commenced in March, 1948. In February, 1949, after about 18,000 had been released, breeding was no longer necessary for large populations had developed in the field and were inflicting severe injury to Cordia scrub. Dispersion of the insect over the island followed quickly, and was assisted by the collection and distribution of about 60,000 adults. Schematiza became extremely abundant so that by the middle of 1950 most expanses of scrub in the island had either been stripped of leaves and inflorescences, or had generally been severely defoliated.

As a result, much scrub is dead owing to a prolonged period without foliage, much is being subjugated by other vegetation, while partial defoliation and direct inflorescence attack have reduced the reproduction of other bushes.

This rapid control of C. macrostachya is attributed to the high fecundity of the Schematiza combined with its freedom from parasites and important predators, and to its suitability to the climates of all Cordia infested regions.

Thanks to the courtesy of Mr. G. S. Dun, Government Entomologist to the Territory of Papua and New Guinea, we have been able to study three interesting new species of Mirids found damaging cacao plants in New Britain. The first was discovered by Mr. Dun early in 1950 in abundance at Kabeira Plantation about six miles from the Lowland Experimental Station at Keravat where considerable damage had been done to the crop. This species was at first thought to be the West African Bryocoropsis laticollis Schumacher, 1917, which might have been accidentally introduced into New Britain. Closer investigation showed that it belonged to a distinct genus and species (Parabryocoropsis typicus, gen. et sp. n.). In September 1950, Mr. Dun found a second species attacking an isolated block of Cniollo cacao at the Keravat Experimental Station. On examination this proved to belong to still another genus and species (Pseudodoniella pacifica gen. et sp. n.).

The populations of Nomadacris septemfasciata described in this paper were all of solitaria or neai-solitaria phase.

Sexual maturation as measured by the developing ovaries took place rapidly though irregularly through the population. Its onset coincided with an increase in the daily number of hours of relative humidity at or above 75 per cent., and abundance of green food; Copulation, which started after the first wide-spread rain, took place before the ovaries of many females were completely mature.

Caged locusts gave a mean fecundity of 183 eggs contained in 2·4 pods which is probably a minimum figure. Pods were laid at intervals of about two weeks and each was laid before the next batch had visibly developed.

The period spent in the egg was at least 39 days, at most 46 days and probably 42 days. Adults appeared 67 days after the first hatchings. Both these periods are greater than those recorded in phase transiens or gregaria.

Solitaria locusts were found to pass through seven instead of six nymphal instars as do gregaria. This difference seemed to be constant. The extra instar was probably interpolated between the second and third of gregaria but was not an exact duplicate of any other instar.

The number of vertical dark eye-stripes is a convenient and fairly constant indicator of the instar. The number of antennal segments in the later instars and in the adult, and also the number of adult eye-stripes, is greater in the solitaria phase.

Amongst the hoppers three main types of coloration were encountered and are briefly described but they could not be closely related to phase. The amount of dark pigment present in late stage nymphs was reflected in the young adult, the appearance of which is described in some detail. Subsequent changes during the dry season are briefly noted, in particular the pink of the hind wing, which becomes faintly visible within a month of the last moult.

The changes in pigmentation which take place during sexual maturation are described in detail. In addition to pronounced darkening of the tegmina which completely changes the appearance of the solitaria locust, certain bright pigments are laid down which are later obscured by a general blackening. It is unsafe to classify Nomadacris septemfasciata as to phase on colour alone unless the date of capture and its relation to the breeding season in the locality is taken into consideration. Solitaria do not normally develop the general reddening of the body which is shown by migrating swarms, even when these are only transiens in phase.