The coffee leaf-miner Leucoptera meyricki Ghesq. is the most serious insect pest of Coffea arabica in Kenya. Until recently, sprays containing parathion, methyl-parathion or diazinon have been recommended for its control.

Field trials were carried out there during 1962 with these three insecticides and two others, fenthion and fenitrothion, that had shown promise in laboratory trials described in an earlier paper. The greater part of the investigation was carried out on the larval stage. Single-tree plots were used, arranged in randomised blocks, and sprays were in most cases applied by knapsack machines. Spraying in all trials was timed to coincide with the presence of large numbers of half-grown larvae. Suitable dates could be forecast because the generations of L. meyricki follow a denned cycle with a single stage dominant at any one time. Mortalities of larvae were assessed, four days after application of the insecticide, by dissecting freshly mined leaves selected at random. Where necessary, a spray of coarse droplets of a poison bait was applied before a trial in order to reduce populations of parasites and mortality due to them to a low level.

At a concentration of 0·02 per cent., a spray of parathion gave a. significantly higher kill than one of methyl-parathion. Diazinon, fenthion and fenitrothion were available as emulsifiable concentrates containing 60, 55 and 50 per cent, active ingredient (w/v), respectively. These were tested at equivalent dilutions. At a dilution of 1¼ pints concentrate in 100 gal. water (affording concentrations of 0·094, 0·086 and 0·078 per cent, active ingredient, respectively), which was the volume per acre required to give full cover, fenitrothion gave a significantly higher kill than fenthion or diazinon, there being no significant difference between mortalities achieved by the latter two insecticides. The addition of a supplementary wetting agent to sprays of fenitrothion increased kill significantly, as did a reduction in spray volume with fenitrothion and parathion. The possible reasons for this are discussed.

The field trials described generally confirm the results obtained in earlier laboratory tests and support the view that any insecticide which shows promise in the laboratory will also give good results in the field.

A small-scale trial on potted seedling coffee plants was carried out to test by the dipping technique the ovicidal properties of concentrations of parathion, diazinon, fenthion and fenitrothion equal to one-half or two-thirds those necessary to give satisfactory field control of mining larvae. Mortality of eggs varied with their age, but in all tests with the first three insecticides it exceeded 90 per cent. In a comparison between fenthion and fenitrothion, the former was significantly more toxic than the latter, which killed only 38·1 and 82·1 per cent., respectively, of eggs ½ and 5½ days old.

The correct timing of sprays against Leucoptera is very important and should follow about seven days after the peak of moth numbers.

The insecticides used in these experiments are considered in the light of the characteristics, which are listed, that are desirable in those to be recommended for the control of Leucoptera on coffee. Those recommended, with rates (Ib. per acre), are parathion (0·4), fenitrothion (0·9) and fenthion (1·0). Diazinon and methyl-parathion are no longer recommended.

Brief notes are given on the distribution of 34 species of sandflies (Phlebotomus) recorded in Kenya. Mention is also made of two other species not so far known from Kenya but from areas close to its border, since these may ultimately be found within it.

The distributions of the 36 species in Kenya and bordering areas, based on published work supplemented by many unpublished records, are shown on a series of maps.

Previous records and new data on trypanosome infection rates in Glossina morsitans submorsitans Newst. in Northern Nigeria are presented, and discussed in relation to the hosts fed on by this tsetse fly. The new observations were carried out in three areas: at Mando and Gamagira, both lying in a fly-belt north of Kaduna, and in the Yankari Game Reserve in Bauchi Province.

Infection rates were obtained by dissection of flies, and the trypanosomes were identified by their locus; the validity of this method of identification is discussed. All infections with Trypanosoma spp. were attributable either to the vivax group or to the conrgolense group; no brucen-group trypanosomes were identified. More than 260 flies from each area were examined during March 1962, at the end of the dry season, and similar numbers during October 1962, at the end of the wet season.

There was no significant difference between dry-season and wet-season infection rates in any area. Taking the two seasons together, the rate at Yankari (12%) was significantly higher than the rates at Mando (5%) and Gamagira (3%), which did not differ significantly. These contrasting infection rates could be related to the host species principally fed on by flies in the different areas as shown by blood-meal determinations. The lowest infection rates occurred where Suidae furnished a high proportion of meals (Mando, 51%; Gamagira, 67%) and Bovidae a small proportion (Mando, 16%; Gamagira, 9%). The high infection rate at Yankari was associated with a high proportion of Bovid meals (53%), especially from buffalo (Syncerus nanus) and bushbuck (Tragelaphus scriptus), and a lower proportion of Suid meals (33%). For the three areas the relationship between infection rate and percentage of Bovid meals was statistically significant.

The species groups of infecting trypanosomes showed further contrasts between the three areas which were unrelated to the total infection rates. At Gamagira, 81 per cent, of infections were congolense group, and this proportion was significantly higher than that at Mando (45%) or Yankari (37%). The differences could be related to the types of host from which blood-meals were principally derived. The highest proportion of congolense-group infections occurred where the highest percentage of meals came from Suidae (Gamagira, 67%), and lower proportions occurred at Mando and Yankari where Suid feeds were relatively fewer (51% and 33%, respectively).

These findings are discussed in the light of existing evidence on the factors governing infection rates in Glossina. It is concluded that, within the over-riding influence exerted by temperature through geographical latitude, infection rates are determined by the type of host that forms the principal source of food. In some populations of Glossina the influence of the nature of the main food source can be sufficient to obscure the general effect of temperature in determining the level of infection. Some of the reasons for these relationships are discussed.

Nine species of Cecidomyiid midges, including Contarinia sorghicola. (Coq.), C. andropogonis Felt, C. caudata Felt, C. palposa Blanch., Stenodiplosis sp., ? Lestodiplosis sp., Clinodiplosis sp., a species of Lasiopterariae and an undescribed species of Bifila, have been recorded from the inflorescences of cultivated sorghums (Sorghum vulgare) and related wild hosts. New morphological and other studies of this complex, involving the use of new techniques which are described, have elucidated the complex without recourse to biological testing.

Contarinia, sorghicola with which C. andropogonis and C. palposa are placed in synonymy, and a new species, Stenodiplosis sorghi, here described, are the only valid species which are primary feeders on cultivated and wild species of the genus Sorghum. Contarinia caudata is a distinct species reared from the grass Apluda varia. Contarinia gambae, a second species described as new, on the basis of specimens reared from the grass Andropogon gay anus, was formerly misidentified as C. sorghicola. C. sorghicola, S. sorghi and C. gambae are described and figured in detail. A species tentatively placed in Lestodiplosis and a species of Clinodiplosis are comparatively rare and of no economic importance. The record of a species of Lasiopterariae from a wild sorghum is believed probably to have been based on a misidentification of the host, and a species previously referred to as the ‘ 3rd Bifila ’ from A. gayanus has no real connection with the sorghum midge complex.

Investigations of the natural history of the virus of Kyasanur Forest disease since its discovery during 1957 in Shimoga District, Mysore State, south India have concentrated much attention on ticks of the genus Haemaphysalis in the region, as virus has repeatedly been isolated from them.

Keys are provided for larvae, nymphs and adults of both sexes of the 14 species of Haemaphysalis that have been taken in the area, with supplementary comments on six other species of the genus recorded, or likely to occur, elsewhere in south India. Illustrations are given showing the characters of the larvae and nymphs that are used in the keys.

The insecticidal potencies of γ-BHC and a range of chlorinated cyclodiene compounds have been measured for normal and resistant strains of both Musca domestica L. and Lucilia cuprina (Wied.). Apart from minor discrepancies, the relative potencies presented similar pictures in the two species, and the resistance spectra were also similar.

Moderate to high insecticidal potency is shown by a variety of compounds with a chlorinated bicyclo-heptene nucleus in the molecule, including Diels-Alder condensation products and chlorinated camphenes. Various additions and sub-stituents on the nucleus affect the potency quantitatively but not qualitatively. In contrast, γ-BHC is almost unique among poly-halogenated cyclohexanes.

When resistance develops to any of the chlorinated cyclodiene compounds, it invariably extends to all others and to γ-BHC and chlorinated adamantane. The resistance level, in most cases, is proportional to the original potency of the compound; this is apparently because resistance is usually complete, so that the more toxic compounds have more to lose. There are, however, a few puzzling exceptions.

The consistency of the cross-resistance spectrum to all members of the group implies a common defence mechanism. This suggests a common mode of toxic action, resistance being due to insensitivity at the site. A common mode of action for the cyclodiene series is understandable; the anomalies are γ-BHC and chlorinated adamantane. Their conformity with the cyclodiene insecticides was investigated by the following observations with normal insects: (a) signs of poisoning; (b) relative potency to different species; (c) tests with mixtures. The general conclusions were not unfavourable to the hypothesis of a common mode of action, though secondary features of the intoxication process somewhat complicated the results.

The influence of a deep river valley system on the distribution of dispersing Aedes mosquitos was studied during 1958–59 in the vicinity of Edmonton, Alberta, Canada. Mosquito breeding within an area extending two to three miles beyond the city limits was prevented by anti-larval measures, and almost the only remaining breeding places were situated on the plains several miles to the north-west and south-east, yet considerable numbers of mosquitos appeared every spring in that part of the city included in the valley-ravine system of the North Saskatchewan River. Previous work had suggested that mosquitos dispersing across the plains were collected by the valley-ravine system and entered the city by passing down the main valley. The present paper attempts to account for this directed dispersal in terms of the behaviour of Aedes mosquitos in response to certain physical factors in the environment. The species mainly concerned were Aedes cataphylla Dyar, A. fitchii (Felt & Young), A. excrucians (Wlk.) and A. stimulans (Wlk.).

The initiation of dispersal flight downwind across the plains at twilight was observed. This took place soon after emergence and was not prevented by moderate winds. It was shown experimentally that neither high wind speeds nor turbulence inhibited the flight of newly emerged Aedes mosquitos, but that individuals several days old were reluctant to take flight in turbulent conditions. Since wind speeds on the plains were generally higher than those in the valleys, these reactions would tend to confine older mosquitos to the valleys while not preventing dispersal of newly emerged mosquitos across the plains.

The direction of the initial dispersal flights from the breeding places was observed in mosquitos escaping from rearing cages. Take-off was characteristically into the wind, but re-orientation downwind took place when the mosquitos began to be blown backwards in flight. It was shown experimentally, by releasing mosquitos in the field when the wind was very light, that the preferred direction of flight uninfluenced by wind was towards the lowest part of the horizon, both on the plains and in the valley. This response would tend to cause mosquitos on the plain to fly into ravines and valleys, and thence down-stream within them. Dispersing mosquitos would thus tend to be held by any valleys or ravines in their path.

Swarming was never observed near the pools from which the mosquitos emerged, but was mainly seen in the valley or on the edge of the valley and ravines. Swarming of A. cataphylla took place during the evenings after the initial dispersal. The swarms were predominantly male but mating occurred during swarming. A cohesive factor seemed to be involved in the behaviour of the swarms, and further dispersal also seemed to occur gregariously; the movement of large male swarms down the river valley was observed.

By the application of optomotor theories of insect flight to previously published data on the flight speed and behaviour of A. aegypti (L.) and A. punctor (Kby.), the relationships between wind speed and permissible heights of flight of these species upwind and downwind were calculated. These relationships were consistent with the observations on dispersal of Aedes mosquitos in the Edmonton area, and could largely explain the mechanism by means of which deep valleys attracted and held dispersing mosquitos.

In contrast to the open plains, the wooded river valley provides a more favourable environment for adult mosquitos. The supply of nectar is greater, saturation deficiency and wind speeds are lower and less variable, and shaded resting sites are more abundant.

Observations on mosquitos in chambers with either vertical or horizontal humidity gradients suggested that the behaviour of Aedes mosquitos is not greatly influenced by humidity.

The number of eggs produced by females of Anobium punctatum (Deg.) (Col., Anobiidae) was determined at Auckland, New Zealand, during annual emergence in December 1957. The females were collected before mating and egg-laying occurred. Each female was weighed and then confined, with males, to an egg-laying block of sapwood of Podocarpus dacrydioides. The average number of eggs per female was 54·8, far higher than obtained from field-collected females, and additionally the egg-laying distribution was neither skewed nor censored. Following a short preoviposition period, eggs were laid rapidly, egg-laying being virtually finished by the 15th day after emergence. Females lived a few days after egg-laying had ceased, maximum length of life being between 24 and 31 days.

For about 60 per cent, of females the number of eggs laid was closely related to the initial weight of the female, but the remaining females laid fewer eggs in relation to their weight.

The egg production and development of Trogoderma anthrenoides (Sharp) has been studied over a range of temperatures from 17·5 to 37·5°C. and in relative humidities of 70 per cent, and near 0 per cent.

At 70 per cent. R.H., the minimal temperature for development was between 17·5 and 20°C. and the maximum between 35 and 37·5°C. Adult females, which apparently required no food, lived on average 18 days at 37·5°C., this period increasing with falling temperature to 146 days at 17·5°C. The greatest number of eggs, a mean of 54 per female present, were laid at 27·5°C. The quickest development occurred at 35°C., females taking a mean of 44.7 days (egg 6; larva 34·3; pupa 4·4). Male larvae developed slightly faster and male adults died a little earlier than females.

Near-zero humidity shortened adult life, reduced egg production and prevented the development of larvae.

Some larvae entered a condition that is probably a facultative diapause resembling that of T. parabile Beal. The diapause was terminated by an increase in volume of food combined with a change of temperature.

The biology of T. anthrcnoides resembles that of two minor pests, T. parabile and T. inclusum Lee., more than that of the important pest T. granarium Everts. The first two species show no signs of becoming serious pests. It is concluded that T. anthrcnoides probably has the potential only of a minor pest.

The effect upon the three-dimensional dispersion of experimental populations of Tribolium castaneum (Hbst.) of internal pockets of grain at 18 per cent, moisture content, either mouldy or free from mould, and superficial ones of 25 per cent, moisture content, in a larger bulk of 14 per cent, moisture content, was investigated at 25°C. The behaviour under these circumstances of insects reared and maintained at 70 per cent, relative humidity was compared with those conditioned at 40 per cent. R.H. for 14 days. It was found that insects reared at 70 per cent. E.H. did not accumulate in the damp grain whereas conditioned ones did. The underlying response was shown to be hygrokinetic and the mechanism an orthokinetic one. The rate of movement of unconditioned adults in grain of 18 per cent, moisture content was approximately twice that in grain of 14 per cent, moisture content. Conditioned adults moved very slowly in the damper grain. There were no significant variations in irregularity of pathway (klinokinesis) under any of these circumstances. When grain of 18 per cent, moisture content supporting a mould growth was used, unconditioned adults did, however, accumulate in it due to trophic behaviour.

While there is considerable plasticity of behaviour in this species a synthesis is attempted of the causal behavioural mechanisms underlying the spatial structure of populations in ecological situations involving humidity gradients; the results are also discussed in relation to grain storage conditions, and the detection and control of the species.

Trials were carried out from 1958 to 1961 at Fassouri Plantation in Cyprus to assess the value of dimethoate (0,0-dimethyl S-methylcarbamoylmethyl phosphorodithioate) against California red scale, Aonidiella aurantii (Mask.), on orange, lemon and grapefruit trees. This pest has hitherto been controlled in Citrus plantations by annual programmes of sprays containing parathion, malathion or white mineral oil, singly or in combination.

Sprays were applied to Citrus trees at high pressure by means of hand-lance or motor-driven equipment in such a way that all parts of the tree were thoroughly wetted. Treatments were replicated in Latin square experimental designs. Results were assessed by counting the numbers of scales on samples of leaves, fruits, twigs and bark taken at various intervals after spraying and also, in some trials, before spraying. The earlier trials were concerned with the numbers of scales killed after single applications and the later trials with the level of control resulting from full seasonal spraying programmes.

A preliminary trial in 1958 showed that very high kill of the scale was produced by a spray containing 0·2 per cent, of dimethoate. In 1959 a range of concentrations from 0·01 to 0·15 per cent, was compared with the standard parathion/malathion mixture against the scale on orange and lemon trees. At 0·03 to 0·06 per cent., dimethoate gave a level of control equal to that of the standard spray and at higher concentrations it was superior to the standard. This superiority was confirmed in trials carried out during 1960 using dimethoate concentrations from 0·06 to 0·1 per cent., the observations being extended to include immature stages of the scale. A high kill of all developmental stages was produced by all the concentrations used, and at 0·08 to 0·1 per cent, dimethoate gave higher kills than the standard spraying mixture.

The effect of dimethoate against late-season infestations of fruits was next investigated, using mixtures with white mineral oil as well as dimethoate alone. Standard late-season sprays of mineral oil with or without parathion were included for comparison. Dimethoate alone at 0·08 per cent., or at 0·05 per cent, with 1·0 per cent, mineral oil, gave good control of the scale, on fruit. Both these sprays were superior, to the standard oil or parathion/oil mixtures. The results suggest that dimethoate may be especially valuable against scale on full-sized fruits, the control of which has hitherto been difficult.

During 1961, full seasonal spraying programmes with the standard compounds were compared with others using dimethoate at concentrations suggested by the earlier trials. The treated plots were large and the spraying methods approximated to normal estate practice. The final results were based on the level of infestation of fruits at harvest, and comparisons between standard and dimethoate programmes were made by means of Ebeling's corrected relative infestation index (C.R.I.). Values of the C.R.I, below 100 indicate that the degree of control achieved by the standard has been exceeded by the test spray. In the first trial, where early-season infestation was not heavy, the standard programme consisted of an initial parathion/malathion spray followed later by an application of white oil, and the test programmes comprised sprays of dimethoate at 0·04 or 0·06 per cent., both followed by white oil, or 0·08 or 0·1 per cent, without a second treatment. The C.R.I, values from these four programmes were 24, 22, 58 and 7, respectively, showing that all were better than the standard. The second trial was carried out in a plantation with a heavy early-season infestation of the scale; the same standard programme was compared with dimethoate sprays at 0·04 and 0·08 per cent., both followed by white oil. The C.R.I. values for these two programmes were 144 and 36, respectively. In the third trial single seasonal applications were compared, using a spray containing 1·5 per cent, white oil as the standard. The four test sprays comprised white oil 1·5 per cent, plus malathioii 0·05 per cent., white oil 1.0 per cent, plus dimethoate 0·04 per cent., dimethoate 0·04 per cent., and dimethoate 0·08 per cent. The respective C.R.I, values of the test sprays were 68, 38, 56 and 29.

In trials against other pests of Citrus trees dimethoate gave control of Coccus hesperidum L. at concentrations of 0·04 and 0·08 per cent. It was effective against Aceria sheldoni (Ewing) at concentrations of 0·08, 0·04 and 0·02 per cent., but was found to be ineffective against Phyllocoptruta olcivora (Ashm.).

During the trials a number of different formulations were used, including miscible oils and wettable powders. One of the miscible oils caused severe scorch marks on fruits; this was shown to be due to the formulating materials and not to dimethoate. A certain amount of leaf-drop was noticed in some trials, and this requires further investigation. Dimethoate is a comparatively safe compound from the point of view of hazards to operators, and toxic residues in sampled fruit have been found to lie within the limits that have been suggested as safe.

The principal conclusion from these trials was that dimethoate is a valuable addition to the limited range of insecticides available for use against Aonidiella aurantii. At fairly high concentrations (0·08%) it gives better control than spray mixtures in current use, and this suggests that it may be possible to devise programmes giving satisfactory control with fewer applications. At lower concentrations (0·04%) it is about as effective as present insecticides. Although dimethoate is both a contact and systemic insecticide, observations suggested that the former function was mainly involved in its action against this scale.

The susceptibility of Musca domestica nebulo F. and M. d. vicina Macq. to topical applications of p,p' DDT, technical dieldrin and γ BHC was determined in Aligarh, India, and the effects of using acetone, Eisella oil or ethanol as solvents were also investigated. Of the three insecticides examined, BHC was found to be the most toxic to both forms of house-fly, and DDT the least toxic, though the latter would be effective for control purposes at concentrations exceeding 1 per cent. Solutions of the insecticides in ethanol were more toxic than solutions at the same concentration in Eisella oil, and the latter were slightly more toxic than solutions in acetone. The two forms of house-fly were about equally susceptible to DDT, but M. d. vicina was somewhat more susceptible to dieldrin and BHC than M. d. nebulo. Males of both forms were more susceptible than females to all three insecticides.

This paper records the ovarian condition of sylvan Culicine mosquitos caught resting and biting in Uganda. Information provided for the commoner species includes Sella's stages of blood-digestion, Christophers' ovarian stages (modified) for nullipars and pars, and sac stages for pars.

The distribution of Sella's stages among resting populations indicates that the several species differ widely in the resting sites chosen by blood-fed females. Among the species studied, Mansonia, fuscopennata (Theo.), M. africana (Edw.), M. uniformis (Theo.) and Culex annulioris Theo. are unusual in that many females probably rest outside forest after a blood-meal.

The ovarian stage in which nullipars and pars come to bite is often characteristic of a species. Nullipars and pars of one species may bite in the same ovarian stage, or in different stages. In species of Mansonia (Coquillettidia) nullipars are typically more advanced than pars, apparently because there is extensive use of food reserves which are exhausted before the first blood-meal; in such species ovarian development can also be discerned in pars between oviposition and a blood-meal, but it is extremely slight. In certain Aedes (subgenera Finlaya and Stegomyia), pars are typically more advanced than nullipars, and among those studied here it is only species of this type which to any extent show the pattern long regarded as normal in Anophelines. Wide variation in ovarian stages of biting nullipars of Aedes raises the possibility that limited autogeny may exist in some of the species studied.

In view of the promising results obtained with insecticidal smokes against the common furniture beetle, Anobium punctatum (Deg.), a field trial was conducted to study the effect of deposits from lindane/dieldrin smoke on adults of the death-watch beetle, Xestobium rufovillosum (Deg.), emerging from infested roof timbers of a college chapel in Cambridge, England, in 1963. Quantitative determination of the insecticidal deposits was made and methods were devised for studying the effect of the treatment on the numbers of beetles emerging subsequently in order to assess the long-term value of annual treatments for reducing the population. Beetles collected from an untreated building were used for comparison.

Fewer males were found than in preceding years and it is postulated that some may have been prevented by the insecticides from emerging. The normal sequence of beetles dropping from roofing timbers—males predominating first, then females—did not occur. Both sexes dropped nearly uniformly, a fact suggesting, particularly in the case of the females, that the insecticides had caused them to drop before their normal time. Mating was considerably reduced. Examination of females showed no signs of their having laid eggs, this being attributed to the action of the insecticide deposits. Beetles obtained from an untreated building and placed on wood surfaces which had been exposed to the smoke treatment were affected but laid some eggs, of which a small proportion hatched; larval boring into such surfaces was, however, completely prevented.

From these results it was inferred that the deposits from the treatment with lindane/dieldrin smoke prevented emerging adults from causing reinfestation of the roofing timbers and it is argued that, provided that this can be achieved annually by a succession of treatments, the beetle population should ultimately be eliminated or, at least, greatly reduced. Other possible effects which might result from annual smoke treatments are accumulation of the insecticide deposits with a consequent increase in toxicity of the timber surfaces and sorption of the deposits by the timber to a point where they might exert a toxic effect on larvae or pupae beneath the surface.