Anthrenus verbasci (L.) (Col., Dermestidae) is a pest of dried animal materials and is widely distributed in temperate regions.

The effects of temperature and relative humidity on development have been studied. It is shown that the periods of incubation and pupation decrease with increase of temperature, the former from 54 days at 15°C. to 12 days at 30°C., and the latter from 89 days at 10°C. to 9 days at 25°C. Humidity differences have little effect.

The larval development is exceptional in that under constant physical conditions in the laboratory there is a rhythmical onset of the larval diapause, i.e., development is regulated into one or more cycles, each comprising a period of active growth followed by diapause. The length of this cycle under constant conditions is considerably less than a year. Larval development may extend over one or two cycles depending mainly upon the temperature. At low temperatures of 15°C., development extends over two cycles; at 20°C. and above, only one cycle is needed; at the intermediate temperature of 17·5°C., half the larvae require one and half require two cycles in which to complete their development.

When the larvae developed under constant physical conditions with malnutrition the rhythm of development was maintained, but the larvae tended to require an extra cycle for development compared with those fed on an adequate diet.

Under three sets of controlled alternating temperatures (ranging from 18 to 33°C.) the rhythm of development was similar to that which occurred in constant conditions at a temperature equal to the mean.

The number of larval moults increased both with temperature and the time spent as a larva. At the unfavourably high temperatures of 30 and 35°C., larvae moulted an excessive number of times; one larva at 30°C. moulted 19 times after the fully grown stage was reached; and, at 35°C., 30 per cent. R.H., 13 out of 20 larvae gradually decreased from about 5 mm. (the length when first put to 35°C.) to 2 mm., moulting a number of times in the process.

Under outdoor fluctuating conditions, the resting period in the cycle is extended, due to the winter temperatures prevailing for some time after the end of diapause. Active development commences again in the spring when the temperature rises, and in this way the cycle is synchronised with the seasons into an annual rhythm of development. The life-cycle under outdoor conditions may take one, two or more years to complete.

Field populations, developing both in attics of houses and under more outdoor conditions, pupated from January to May, the time of pupation being mainly dependent upon the ambient temperature prevailing after the termination of diapause.

Diapause is of value to A. verbasci because it induces a rhythm hi the life-cycle which synchronises with the rhythm of the seasons and ensures that the adults are present when the environment is favourable for their activity, i.e., during May and June when the maximum hours of sunshine favour flight and the preferred flowers are in bloom.

The mechanism by which the rhythmical onset of diapause is controlled has not been investigated.

Evidence is given, based on, field observations and experiments, of damage to fruits of cacao by two species of Amblypelta (A. theobromae Brown in New Guinea and A. cocophaga China in the British Solomon Islands); the nature of the damage is described.

A summary is given of the feeding habits generally, and the effects on the plants attacked, of members of the genus Amblypelta.

Comprehensive lists of the known food-plants of each species of Amblypelta are given.

Quantitative measurements of the sorption of γ BHC and dieldrin in Uganda mud blocks have been made. Gamma BHC diffused more rapidly than dieldrin, and within a few weeks had achieved an almost uniform concentration throughout the sprayed blocks. Only when the uniform concentration had been reached did loss by evaporation from the blocks become marked. Increased dosages of γ BHC gave increases in biological activity which were roughly proportional to the dosages used. Sorption on to mud greatly prolonged the residual life of γ BHC as compared with similar deposits on glass.

Dieldrin behaved in the same way as γ BHC although because of its slower rate of diffusion the distribution in the blocks had only reached in 48 weeks the stage reached by γ BHC in eight weeks. There was no appreciable loss of dieldrin during this time, whereas about 90 per cent. of the deposit on glass plates had been lost.

Gamma BHC, dieldrin and DDT were recovered from the adsorbed state on mud and identified. Any decomposition is therefore likely to be negligible. Dieldrin was also recovered from two soils which had much higher “surface acidities” than the standard.

Active mud can only sorb the portion of insecticide vapour from an evaporating deposit which happens to diffuse in its direction. This is to be expected, but the system has some peculiarities because the evaporation of γ BHC from filter papers over mud blocks is much faster than in the absence of the mud.

Measurements of the distribution of DDT and dieldrin in soils less active than the standard Uganda one showed that both the initial adsorption and subsequent diffusion were very much slower.

The activity of Uganda soil was not reduced by removal of material soluble in organic solvents, and was only partly reduced by complete extraction of iron compounds.

Variation in temperature over the range 20 to 30°C. had only small effects on the diffusion of DDT and dieldrin within mud blocks.

Repeated applications of DDT and dieldrin to the same blocks did not result in any observable slowing in the rate of disappearance. The concentration of insecticide in the successive layers of mud, did, of course, increase with successive sprayings.

The significance of Glossina morsitans submorsitans Newst. to the livestock economy of Northern Nigeria is mentioned. Differences in the ecology of the fly have been noted in the Guinea and Sudan savannah zones, respectively. In the former, its distribution is relatively widespread and diffuse, whereas in the latter it is restricted to linear strips associated with river flood plains. The area dealt with in the present work lies in the Sudan zone. The relationship of the fly to its vegetational environment is described, there being a marked concentration of almost the whole tsetse population in evergreen forest islands of relatively limited extent in the second half of the dry season. The source of food is mainly warthog, which were numerous in the area.

A focus of the fly, covering an area of seven square miles, in which the dryseason concentration sites, mainly forest islands, amounted to approximately 200 acres, was selected for an experiment. It was isolated from the main focus by a natural barrier five miles wide.

Possible eradication measures in this focus are mentioned and reasons given for adopting the application of a residual insecticide.

DDT, in the form of a 50 per cent, wettable powder as a 5 per cent, suspension of actual DDT in water, was applied, during the second half of the dry season, at an estimated rate of 20 lb. per acre to the evergreen forest islands, which had previously had paths slashed around and through them. Pneumatic knapsack sprayers were used. A preliminary trial showed that, for up to six weeks after application of the insecticide, examples of G. morsitans from unsprayed forest, placed in contact with sprayed leaves and bark, died in three hours, controls remaining alive for 24 hours. It is suggested that this good persistence may be attributable to the fact that the treated surfaces were in the shade, and that the application was made during the rainless season and at a time when the vegetation was dormant. There was a rapid decline in the population of G. morsitans after spraying. The flies persisted longest (5 weeks) in a site associated with Mitragyna inermis. One application only was given to one part of the focus and in many others one application would probably have sufficed, the second being given in most instances to control G. tachinoides Westw., which was also present, and only in two instances for the eradication of G. morsitans that persisted after the first application. One of these was the site associated with Mitragyna inermis, mentioned above. The last specimen of G. morsitans was caught five weeks after the first application, and none has been caught in the sprayed area for up to 18 months after spraying. The cost of the insecticide and labour to apply it amounted to £700 for an area of seven square miles of focus in which the dryseason concentration sites to which insecticide was applied amounted to approximately 200 acres. The final result regarding G. tachinoides was indefinite for reasons which are mentioned.

Changes in relative humidity had a very marked influence upon the biological activities of γ BHC, dieldrin and DDT sorbed on Uganda mud blocks. In agreement with field observations, kills of mosquitos increased as the humidity increased and this effect was rapidly reversible.

Disappearance of insecticide particles from the mud surface was inversely related to humidity, the rate increasing as humidity decreased. On the other hand, the rates of diffusion of sorbed insecticide away from the surface were greater at higher humidities.

It is suggested, therefore, that when the biological activity of a mud surface is increased by increasing the humidity, the insects acquire a greater dose of insecticide not because the concentration of insecticide in the surface layers is greater but because the insecticide that is already present acquires a greater mobility. This greater mobility results in a more rapid diffusion in the mud itself away from the treated surface and a greater potential for diffusion into insects resting on the mud surface.

Support for these conclusions was obtained by showing that on transferring dieldrin-treated mud blocks from low to high humidity the change in biological activity occurred at about the same rate as the increase in water content of the blocks.

The influence of humidity upon the sorption of DDT and dieldrin on a selection of soil samples of widely differing origin was observed. Both insecticides disappeared from the surface more rapidly at low than at high humidity on all the soils.

The rainfall of the Blue Nile valley diminishes towards the north, and the number of mosquitos tends to do the same, but the natural state of affairs has been somewhat altered by irrigation works in the shape of the Sennar reservoir and the watering of cotton, sorghum and sunt trees (Acacia arabica, Willdenow), and will be further altered when the proposed dam at Roseires is constructed.

The latter dam will form a large reservoir in the Kiri-Roseires area where conditions are likely to differ from those of the Sennar reservoir. Anopheles funestus Giles and many other species occurred in the stretch downstream between Roseires and Abu Hugar in which riverside basins, overgrown with sunt trees, were flooded when the river was high.

Farther downstream, between Karkoj and Sennar, breeding conditions were affected by the Sennar dam, water at full storage level reaching different heights in the basins according to their distance from Sennar. Near Sennar the dualpurpose dam had a particular effect on the aquatic vegetation and the mosquitos.

A. gambiae Giles bred among Najas pectinata (Parl.) Magnus which, however, only occupied a small area in the reservoir, A. rufipes (Gough) bred in small numbers in various places, and A. pharoensis Theo. in a large area of creeping grass growing on silt under conditions which caused it to form a raft that rose and fell with the water. Adults of A. pharoensis, which was by far the commonest Anopheline, rested near houses by day at certain times of the year. Control of the grass was difficult and liable, to favour more dangerous species of mosquitos. Differences between the Sennar and Jebel Auliya reservoirs are discussed.

In the riverain area between Abu Geili and Soba, A. gambiae bred in residual pools in the river-bed in the dry season and in flooded sunt basins in the rains. Control of larvae was very difficult in these basins and much reliance was placed on residual sprays against adults in houses.

Breeding conditions in the Gezira irrigated area are described with particular reference to the type of clay soil. There were many larvae of A. gambiae in field channels at the end of the rains when irrigation began, and in March when the summer started. The latter increase was not reflected by any increase in the number of adults, probably owing to the reduction in length of life of the latter in the very hot dry weather. A. rufipes was sometimes found in houses. Control measures are briefly described.

Some mosquitos of Khartoum and a few other areas within the Blue Nile valley are briefly considered.

An experiment on Geescroft field, Rothamsted, from 1951 to 1954, tested the direct and residual effects of BHC, DDT, aldrin and chlordane applied to control wireworms (Agriotes spp.) in wheat.

The treatments applied were BHC seed dressing at 2 oz./bushel of a dressing containing 20 per cent. γ isomer of BHC; BHC 3·5 per cent. dust, combine-drilled to give 3·8–4·0 oz. γ isomer per acre; DDT 5 per cent. dust, combine-drilled to give 7·5 lb./acre technical DDT; aldrin 1·78 per cent. dust, combine-drilled to give 3·56 lb./acre technical aldrin, and chlordane 5 per cent. dust, combine-drilled to give 5 lb./acre chlordane.

In the year of application, the first out of old grass, when wireworm attack was slight, the plots treated with BHC, aldrin and chlordane, combine-drilled, gave significantly greater yields than the control plots. In the following year, when wireworm attack was heavier, residual effects on yield were observed on plots initially treated with BHC, DDT, aldrin and chlordane, combine-drilled. In the third year, residual effects on yield were observed on the plots initially treated with BHC, aldrin and chlordane, combine-drilled.

No direct or residual effect of BHC seed dressing was observed.

The residual effects are closely associated with the effect of the treatments on the wireworm population.

The results are compared with those of previous experiments and the increases in yield from the various treatments are discussed briefly.

Successful emergence of examples of Contarinia sp. and associated parasites has been obtained at Rothamsted Experimental Station from midge-infested heads of sorghum received from India (Mysore State) and West Africa (Ghana).

Since typical pre-mating behaviour was observed on all of the few occasions when newly emerged males and females from the two continents were confined together, and actual mating was obtained between a male from Ghana and two females from Mysore in rapid succession, it is concluded that inter-mating will take place under suitable environmental conditions, although in the present series of experiments such conditions were rarely present.

It has not yet been possible to test the fertility of such inter-matings or to prove biologically that the species of Contarinia concerned is the C. sorghicola (Coq.) of Texas, although on morphological grounds there are apparently no reasons for their separation.

Two species of parasites, a Tetrastichus sp. (group of flavovarius, auct.) and Eupelmus popa Gir., were reared from the Indian material, and another species of Tetrastichus (group of flavovarius, auct.) and E. popa were reared from the West African material.

The effect of temperature on the growth rate and survival of the immature stages of Aëdes aegypti (L.) was studied by rearing them at each of a series of constant temperatures from 14–38°C. in water to which adequate food (bakers' yeast) was added. Larvae were hatched, by immersing eggs in water, in four successive groups with an interval of six hours between each, and six hours after the last group hatched, and every 24 hours thereafter, those surviving in each group were recorded and transferred to fresh water and food, the exuviae remaining being recorded. The average time at which any given stage was reached was taken as the mid-point of the 6-hr. period within which the number of individuals that had completed the previous stage reached 50 per cent, of the total that finally did so.

The curve relating temperature and time of development from newly hatched larva to adult is hyperbolic, except at the extremes. The later the instar, the lower is the temperature at which growth is most rapid. The threshold of development was between 9° and 10°C., the developmental zero 13.3°C., and the average thermal constant (between 16° and 32°C.) 2,741 degree-hours. The highest and lowest temperatures permitting development from newly hatched larva to adult were 36° and 14°C., respectively. The average durations of the four successive larval stages and the pupal stage, expressed as percentages of the time taken for newly hatched larvae to reach the adult stage, were 14.6, 13.9, 17.5, 33.3 and 20.6, respectively.

A method of estimating the damage inflicted on the developing fruit of the coconut palm by Pseudotheraptus wayi Brown is needed in order to assess the efficacy of measures for the control of this Coreid. The insect lives in the crown of the palm, populations are small in relation to the damage they cause, the adults take wing readily and the nymphs are agile and secretive. Direct estimation of populations by hand-collection, trapping, the use of knockdown sprays and marking-recapture methods, using paints or radioactive materials, were all unsuccessful, and indirect methods of estimation were therefore studied.

The growth, flowering and fruiting habits of the coconut palm are described. There is a single growing point, at which the leaves are produced in succession. From 12 to 18 inflorescences are formed each year; each is borne in a leaf axil and carries male flowers distally and female flowers proximally; the latter open, and are fertilised, almost together, after all the former have fallen off, and some 3–4½ weeks after the inflorescence has emerged from its spadix. All subsequent stages in the development of the fruiting body are dated from the latter event.

The young nut at first elongates rapidly and in the first six months attains over 80 per cent. of its final length; it is ripe at about a year.

In the absence of damage by insects, from 20 to 80 per cent. of the fruiting bodies are shed as nutlets, 1–2 weeks after fertilisation, the proportion depending on the variety of the palm and being less in those that bear few flowers and large nuts, but very few are shed at any other stage of their development. When an adult or a late-instar nymph of P. wayi feeds upon a developing fruiting body a characteristic lesion develops at the site of the puncture, which is concealed by the calyx, and if the fruiting body is less than three months old at the time (in which case it is locally termed a kidaka, plural vidaka) it is normally shed 4–7 days later. As the nut develops, it becomes less likely to be shed following attack by P. wayi, although the lesion formed may be invaded by fungi or by the weevil, Diocalandra frumenti (F.). Fruiting bodies attacked by the latter insect cease growth but are not shed. Experiments and field observations show that where damage by P. wayi is prevalent, a proportion of the vidaka are shed in the pre-fertilisation stage, even though they show no evidence of attack by the insect. The extent and implications of this phenomenon are not yet understood.

Fallen vidaka rot quickly and those that are found will reflect the damage that was inflicted 7–10 days previously. By collecting a sample of freshly fallen vidaka, removing the calyces and determining the percentage of them that shows damage by P. wayi, a measure is obtained that is termed the Vidaka Damage Rate (V.D.R.). The method advocated is to collect at random and at weekly intervals a sample of at least 100 vidaka per ten acres, excluding any with an overall length exceeding three inches. This size is reached at about 2½ months; older fallen nutlets invariably show damage from P. wayi or other causes. No significant differences have been found between values of the V.D.R. based on such collections and those based on collections from below individual palms, or rows of palms, taken at random. No significant difference was found between vidaka in the pre-fertilisation stage and those in the stage at which normal nutfall occurs as regards the proportion showing damage by P. wayi, and the former are therefore not excluded.

Comparison of the numbers of nymphs of P. wayi found by two trained entomologists at weekly intervals on 12 palms in each of two areas, one of which was treated with an insecticidal spray at monthly intervals and the other left untreated, and the V.D.R. determined a week later in the same area but on a larger sample of palms, showed a curvilinear association between the two quantities; the association between the logarithms of the quantities was linear but the correlation was not quite significant. In more detailed investigations, two 100-acre areas were used, one of which was undergoing insecticidal treatment, and in each a large but variable number of palms (from 100 to over 900) was examined during each week over a period from mid-October 1956 to the end of March 1957 by a team of climbers who had been trained to search for P. wayi. There was less variability in the data from the control than from the treated area; the latter showed a curvilinear relationship between the observed population of nymphs of P. wayi and the V.D.R. from the whole area one week later, but the correlation between the logarithms of the two variables was not significant.

If counts of first- and second-instar nymphs, which cause very little damage, were excluded from the data, together with any week in which no individuals were recorded, and the values of the V.D.R. were computed from that part of the area in which the insects were counted, then, when both variables were converted to logarithms, the transformed data showed a straight-line relationship with a highly significant correlation coefficient of −0·975. The regression equation indicates that where the number of palms that it would be necessary to search in order to find one 3rd- to 5th-instar nymph is 10, 100 or 1,000, the corresponding value of the V.D.R. would be 84, 13 or 2·4, respectively. It is concluded that where the V.D.R. is below 20, the population density giving rise to such a rate of damage is so low that its accurate determination by direct counts is unlikely to be possible.

Data on V.D.R. and yield were collected from a number of experimental plots and control areas; values from the latter were too uniform to give rise to significant correlations, but when a quarterly estimate of the V.D.R. in an experimental area, obtained from the totals of damaged and of undamaged fallen vidaka collected during successive three-month periods, was compared with the figure for yield obtained from harvesting the same area during the corresponding quarter the following year, a linear relationship was found between yield and V.D.R., the coefficient of correlation being significant in each of the five areas considered, and ranging from −0·7 to −0·984, and the values of a and b in the regression equation Y = a + bX, where Y is the yield in nuts per palm per harvesting and- X is the quarterly value of the V.D.R., ranged from 13·65 to 19·8, and −0·141 to −0·287, respectively. It is concluded that the V.D.R. is a good measure of expected yield, provided that the rate does not rise unduly in the interval between assessment and harvest; in such circumstances, the increased population of P. wayi that is reflected in the increased V.D.R. may damage the nuts at a later stage of their development and so reduce the yield below that expected.

In laboratory cultures of Wheat Bulb Fly, Leptohylemyia coarctata (Fall.), a daily oviposition rhythm was observed in which egg-laying was virtually restricted to the afternoon and evening with maximum laying occurring in the two hours before nightfall. The time of oviposition coincided with that part of the diurnal flight rhythm, earlier observed, in which the flies actively congregated on wheat and this, it is suggested, could account for the fact, already recorded, that laying has been found to occur mostly on sites close to an infested crop.

The oviposition rhythm was maintained for 24 hours in absence of light and therefore appeared to be partly inherent. However, it could be influenced by the times of exposure to light and disappeared in constant light. Darkness did not appear to affect the egg-laying rate but a temporary increase followed exposure to continuous light. Within the course of the experiments the rate was not affected by small changes in temperature.

The individual fly laid up to 180 eggs in the laboratory in periodic batches of up to 42 eggs laid over periods of 1 to 6 days. This periodicity was obscured in cages containing a number of flies. Disproportionately small decreases in the mean daily laying rate occurred with increases in this laying period. Within the laying period the rate progressively increased with each successive day. The total number of eggs laid was not related to the number of ovarioles. In the laboratory, the rate of laying increased with age and most of the eggs were laid by relatively few flies.

The rate of egg-laying and survival at different stages in the field is discussed and it is suggested that about two per cent. of the eggs successfully develop as matured females which lay an average of about 50 eggs each.

The larvae of Culicoides circumscriptus Kieff. are mostly negatively phototactic when extracted from mud and placed in water. Experiments show, however, that if kept without food over a period of time a large proportion becomes positively phototactic. The provision of food causes them to revert to a photonegative taxis which may be permanent as long as suitable food is given, or temporary if the food does not satisfy their nutritional requirements. On the other hand, the provision of a completely non-nutritive medium does not bring about such a reversion. The significance of this behaviour is discussed in the light of the habits of the larvae in the field.

Most of the experiments were carried out with batches of fourth-instar larvae, but in a few, third-instar larvae and fourth-instar larvae near to pupation were used. From the results it is suggested that the processes of ecdysis and pupation may bring about a reversal from photonegative to photopositive taxis independent of the need for food.

The significance of the behaviour of the larvae towards light stimuli is discussed in relation to their habits in the field. It is assumed that its function is to maintain the larvae on the surface of the mud while feeding and to drive them below when they have fed, and that some other type of tropism must initially drive them to the surface or keep them below according to their nutritional needs.

It is shown that the behaviour towards light stimuli of the larvae of C. maritimus Kieff. differs somewhat from that of C. circumscriptus and reasons are suggested for this.

A second series of experiments designed to throw some light on the food requirements of the larvae is described. In a discussion on the results of these it is shown that the larvae feed on material both on the surface of the mud and below the surface, and it is suggested that larvae which have fed on sub-surface food become positively phototactic when they require food from the surface and, having fed there, revert to photonegative behaviour. If, however, photopositive larvae have not previously had the opportunity to feed on sub-surface material they continue to act as completely starved larvae and remain photopositive in spite of their having fed on surface material.

The detailed constituents of the larval diet have not been worked out. The larvae appear to be detritus feeders, feeding mainly on vegetable matter and bacteria obtained on or below the surface of the mud, though green algae are not an important part of their diet. They are carnivorous on occasion but are normally not so when other food is readily available. They are selective in their choice of food and at least three factors, sapidity, texture and the size of particles, appear to influence this selection.

The Lepidopterous stalk borers that occur in Uganda in association with the Gramineae were studied there during 1954–1956 by collecting on all likely host-plants at two centres and by a country-wide survey in which stalk-borer damage in cereal crops was qualitatively assessed at five-mile intervals along the routes followed, and the species of borer present in such crops and, where possible, in nearby wild host-plants were determined. The commonest Noctuids were Busseola fusca (Fuller), B. segeta Bowden, Sesamia calamistis Hmps. and S. poephaga Tanas & Bowden. All these attacked sorghum, maize, sugar-cane and (except the last) finger millet (Eleusine coracana.); so also did S. botanephaga Tarns & Bowden, but only near swamps, in which it infested sedges (Cyperus spp.) and reeds (Typha australis), from which the other species were virtually absent. Only S. calamistis and S. botanephaga attacked rice. All attacked Pennisetum purpureum, Sorghum vertictlliflorum, Vossia cuspidata, and (except S. botanephaga) Panicum maximum, and also other wild grasses.

B. fusca is widely distributed but most abundant in areas of intensive cultivation, where crop residues abound in which the resting larvae can survive the dry season. B. segeta is the most frequent species in Pennisetum purpureum and Panicum maximum, which are extremely common over most of the country, but is rare in cereal crops. S. calamistis (to which earlier records of S. cretica (Led.) and S. vuteria (Stoll) must be attributed) is not numerous but occurs in every district except Karamoja, where it cannot survive the dry season; and S. poephaga is known only from northern and eastern districts and is unimportant.

Chilo zonellus (Swinh.), which may be a recent introduction, occurs in all the cultivated host-plants and most of the wild ones except Cyperus and Typha; it has not been found at altitudes above 4,000 ft. in the west or 5,000 ft. in the north and east, but elsewhere it is the prevalent borer and can cause severe damage in dry years and on out-of-season crops. It was the only species besides B. fusca found on bulrush millet (Pennisetum typhoides), the tough stem of which resists attack. On the western border, Eldana saccharina Wlk. attacks sorghum, maize and sugar-cane at high altitudes, and Maliarpha separatella Rag. attacks rice. A fourth Pyralid, Pectinigeria sp., occurs on maize.

When small plots of host-plants were grown in a matrix of sorghum, and also in a swamp, and the whole sampled at harvest for borer infestation, all the cultivated hosts and many of the wild ones suffered some attack, the percentage of stems bored varying from 10 (finger millet) to 89 (sorghum) amongst the former, and reaching 34 (Panicum maximum), 40 (Sorghum verticilliflorum) and 50 (Pennisetum purpureum) amongst the latter. Immature stages of C. zonellus and B. fusca greatly outnumbered those of Sesamia, especially in the more heavily infested host-plants.

Notes are given on the life-histories of the commoner species of borer and on their habits in the field. In the laboratory, the lengths of the life-cycles, in days, were 68–75 (B. fusca), 65–78 (B. segeta), 46–58 (S. calamistis) and 46–53 (C. zonellus). In the dry season, the larvae of B. fusca entered a resting stage, which prolonged the life-cycle to 200 days; such larvae were found only in living or dry stems of crop plants. C. zonellus and Sesamia spp. bred continuously, in the dry season the former being found chiefly in trash, stubble and volunteer tillers of sorghum, the latter in these and living stems of grasses.

Of the principal cereal crops in Uganda, sorghum is the most widespread. The main crop, sown after the longer of the two dry seasons, suffers little borer attack; second crops are more severely affected, but plants with thick stems or numerous tillers nevertheless yield heavily. Finger millet is the staple food crop in the north and west; borer damage is negligible and restricted to small patches of “dead-hearts” caused by larvae from single egg-masses of S. calamistis. Maize is grown on a large scale in the districts bordering Lake Victoria and in the highlands; borer attack is usually very late and, where rainfall is adequate, appears not to afiect yields.

Apanteles sesamiae Cam. and another, unidentified, Braconid probably control S. calamistis, but on the other stalk borers the incidence of parasites, which are listed, is low. Destruction of all crop residues and wild species of Sorghum around cultivated areas would considerably reduce borer attack at the beginning of the growing season, but chemical control was only partly effective and did not increase the yield.

A technique is described for counting the numbers of Pseudotheraptus wayi Brown on coconut palms, on which this Coreid is a serious pest in East Africa, Zanzibar and the neighbouring islands. The crown of each palm is systematically searched by an African assistant, the insects collected being classified by instars and then replaced. The adults can fly and very few are seen or captured.

Palms were examined by a team of searchers in five areas in a well-maintained plantation on Mafia Island, 3–4 separate samples, each of 61–138 palms, being taken in each area between mid-January and mid-February 1956. In all, 13 searchers participated, but not all were used on the same day; when they had become experienced their daily catches were of comparable size.

The total nymphal populations, and the proportions of them in the various stages, are sufficiently consistent to suggest that the searching technique may give reproducible results, and thus be of considerable value as a means of assessing the results of control measures.

The average catch was about one nymph for each palm that was searched, and recaptures from known numbers of bugs liberated indicated that about one quarter of the population present was being found. The nymphal population is not distributed at random among the palms.

The relation between fumigation techniques, mortality and sorption of fumigant was investigated by two factorial experiments in which adults of Calandra granaria (L.) and C. oryzae (L.) were exposed to hydrogen cyanide at concentrations of 12, 26 or 44 mg. per litre and pressures of 2, 27, 52 and 76 cm. mercury for 30, 60 or 90 min., or at given concentration-time products (36, 72 or 108 mg. hr. per litre), in each of which the time component was 1, 4 or 12 hr., and pressures of 2, 37 and 76 cm. mercury. The methods of fumigation and estimation of sorption and mortality were those used in earlier investigations and the results are shown in a series of graphs.

For both species, sorption of hydrogen cyanide increased as the total pressure was reduced, about three times as much being sorbed, in the first experiment, at a pressure of 2 cm. as at atmospheric pressure, the increase in sorptive capacity being greater in the case of C. oryzae than in that of C. granaria. In the second experiment, sorption by both species, for a given concentration-time product, was greater at a high concentration applied for a short period (1 hr.) than at a lower concentration applied for a long period (12 hr.); in the former conditions, C. granaria consistently sorbed more fumigant than did C. oryzae, in the latter, the reverse was the case, and in intermediate conditions (4 hr. exposure), the amounts sorbed by the two species did not differ materially. This result was inconsistent with that of the first experiment, in which C. oryzae sorbed more than did C. granaria during short exposures (30.90 min.).

These effects on sorptive capacity of differing conditions of fumigation could account for most of the reported departures from the rule that the biological effects of fumigation can be described by the product of the mean concentration of fumigant applied and the period of exposure. Comparison between mortality and sorption at pressures of 27–76 cm. in the first experiment showed, however, that while these were broadly associated, the increased mortality at higher concentrations was greater than would be expected from the associated increase in sorption, and this discrepancy was significantly larger for C. oryzae than for C. granaria.

With a view to providing information useful in practical control, the relative susceptibility to pyrethrins, and to pyrethrins plus piperonyl butoxide, of a series of stored product insects has been determined. Adult moths and beetles of 31 species were investigated, together with the larvae of 16 of these, and that of one other.

The insects were treated with 1.3 per cent, pyrethrins, and 0.3 per cent, pyrethrins plus 3.0 per cent, piperonyl butoxide, in a heavy, highly refined mineral oil (Shell Risella 17). Both formulations were applied in two ways: insects were exposed on sprayed filter papers or were directly sprayed. Insects were also treated with the oil alone by both techniques. While confined on films, and after being sprayed, the insects were kept at 25°C. and 70 per cent. R.H.

Large differences in susceptibility were encountered. The adult moths and Bruchids were susceptible, the adult Ptinids rather resistant, but otherwise susceptibility showed little correlation with systematic classification. The larva of a given species was usually more resistant than the adult. Among the adults of the different species, susceptibility to pyrethrum appeared to be correlated with high activity of the normal insect.

On the whole, 1.3 per cent, pyrethrins and 0.3 per cent, pyrethrins plus 3.0 per cent, piperonyl butoxide were of about equal toxicity.

Information on the world distribution and host-plants of the Groundnut Bruchid, Caryedon gonagra (F.), has been summarised from the literature. As a result of misidentification of the species that attacks groundnuts and of differing views about its generic assignment, this information has been given under several different names. The records brought together here are believed all to represent C. gonagra, and in a number of cases this has been confirmed by examination of the material concerned by Mr. B. J. Southgate.

C. gonagra is widely distributed in the Old World tropics and sub-tropics, but it is absent from Australasia, and it has only a restricted distribution in the New World tropics. Almost all its host-plants belong to the Leguminosae, the principal one being the tamarind, Tamarindus indica, in the pod of which the beetle has been found to develop more quickly than in the groundnut.

Data on the life-history and habits, and on the duration of pre-adult development and adult life, are summarised from the literature.

Experiments are described to determine the optimum conditions for multiplication of C. gonagra, using groundnuts as food. When adult females were allowed to lay large numbers of eggs on shelled and unshelled nuts, only a small proportion of the resulting larvae completed their development, the number of adults that emerged averaging about 2·4 per kernel in shelled nuts and 3·2 in unshelled ones. The developmental period at 70 per cent. relative humidity was 42 days at 30°C. and 91–98 at 25°C.; the former figure is less than any recorded in the literature at higher or lower temperatures, and all subsequent experiments were therefore made at 30°C. and 70 per cent. relative humidity.

Adults confined for three weeks, starting when four days old, at the rate of 25 pairs on 160 g. of a mixture of broken and intact kernels gave rise to some 314 F1 adults; this total was virtually unchanged when 50 pairs were used, but lower densities, though giving rise to greater yields per parent adult, gave much lower yields per weight of food. Emergence of adults began six weeks after the date of egg-laying and reached its peak from one to three weeks later.

The yield from ten females on intact kernels was greater than from the same number on the mixture, but differed little whether the parent adults were left on for one week or three weeks, indicating that the majority of the eggs are laid in the first 11 days of adult life. The yield from unshelled nuts was nearly twice as great as that from shelled nuts, and also significantly larger than that from shelled nuts with ground shell added. Possible causes of this are discussed.

The sexes can be distinguished in the adult stage by differences in the terminal abdominal segments.

The Cowpea Weevil, Callosobruchus chinensis (L.), has been distributed by commerce and now breeds throughout most of the tropics and sub-tropics, although in the southern part of Africa it is replaced by C. rhodesianus (Pic). The systematics of both species are discussed and redescriptions given of them and of C. subinnotatus (Pic), formerly regarded as a variety of Bruchus vicinus Gylh., together with an account of the genitalia of both sexes, and Tables distinguishing the first two species from one another and the third from the closely related species, C. maculatus (F.).