A field study was made of the effects of γ BHC, Sevin, toxaphene and ronnel (fenchlorphos) used as sprays on the numbers of ticks infesting cattle at Shika stockfarm in the Northern Guinea Savannah zone of Nigeria.

The tick population included Boophilus annulatus (Say), B. decoloratus (Koch), Amblyomma variegatum (F.), Hyalomma truncatum Koch and Rhipiccphalus simus simus Koch, and its distribution on the host is described.

Significance tests of treatment difference were carried out for initial kill and reinfestation rate. In both dry- and wet-season trials toxaphene proved to be the most effective ixodicide. A satisfactory degree of control was given by γ BHC but not by Sevin or ronnel.

It is concluded that spraying at 21- and 7-day intervals during the dry and wet seasons, respectively, with either toxaphene or γ BHC will maintain a stable, satisfactory level of tick parasitism and premunity to tick-borne diseases in the herd.

The larval populations of Busscola fusca (Fuller), a major pest of the guineacorn (Sorghum vulgare) crop, which survive the dry season in and around villages near the Research Station, Samaru, Northern Nigeria, were assessed by sampling. The larvae of B. fusca survive the five to six rainless months in diapause in crop residues, most important of which are guineacorn stems, which are stacked in the fields after harvest. Between 1956 and 1962, 100-stem random samples were collected from as many stacks as possible within an area of about six square miles. Each of the 348 samples was dissected immediately after collection and the number of living larvae of B. fusca per sample was recorded. The mean number of larvae per sample varied annually and ranged from 7 in the 1960–61 dry season to 33 in the 1959–60 dry season. The mortality of larvae is comparatively low between January and March, when most samples were collected, and it is concluded that the date of sampling did not unduly influence the estimates of annual variations of the population. The location of sampling areas also had surprisingly little effect and, despite uneven growth of the crop, the estimates of larval populations were remarkably uniform throughout the ten sampling areas and between samples within the main sampling area of Bomo village.

It is concluded that there is considerable variation in dry-season populations from year to year. The factors causing this variation have not been determined, and it is suggested that other workers might profitably continue and expand these investigations.

Cryptolestes pusilloides (Steel & Howe) has, since 1944, become a regularly occurring pest of stored cereals in South America, Australia, South Africa, and to a lesser extent, East Africa, and apparently occurs also in North America as well as in Portugal (where it has recently been found on stored almonds), but has not established itself in flour mills in the U.K., notwithstanding its frequent introduction. Prior to that time it appears to have been very rare. Its life-cycle resembles that of C. ugandae Steel & Howe, and in common with that species and with C. turcicus (Grouv.), it is unable to breed successfully at relative humidities below 50 per cent. Its temperature range is 15–35°C., the optimum for development and fecundity being at about 30°C. at 90 per cent. R.H. Survival was greatest at 27·5°C. and newly formed adults weighed most at 22·5°C. In general, males weighed more than females and their developmental period under any one set of conditions was slightly longer than that of females. The biological information now available shows that C. ferrugineus (Steph.) and C. capensis (Waltl), which are taxonomieally associated by exhibiting sexual dimorphism in the structure of the mandibles, are species that can withstand dry conditions, whereas C. ugandae, C. turcicus, C. pusillus (Schönh.) and C. pusilloides, all of which show sexual dimorphism in the antennae, are unable to breed at relative humidities much below 50 per cent.

An original method of breeding Phlebotomus papatasii (Scop.) in the laboratory in the Egyptian climate was evolved, whereby the development of a fungal growth, a well-known obstacle, was prevented by incorporating, in the larval feeding medium, living material from cultures of a bacterium, Alcaligenes viscosus, which had been found to be the predominant micro-organism in samples of soil collected from breeding places of P. papatasii in the field. Later, eight other Schizomycetes were also found to keep in check the development of mould. Certain fungicides also gave satisfactory results. Breeding pots made of unglazed earthenware were used. A layer of finely sieved sand (18 meshes) about 5 cm. deep was placed at the bottom of the pot and moistened with sterile water. To a mixture of one part dried, ground, sieved guineapig faeces (60 meshes) and two parts sieved dry earth (60 meshes), sufficient of a water suspension of the bacterium was added to impart a damp but friable condition. Granules of this larval feeding medium were then scattered over the sand in a loose layer about 1 cm. thick. Each breeding pot was stood in a petri dish of water and was placed in a small muslin cage to which adult insects were introduced. The females, which obtained their blood-meals from three-day-old white mice, oviposited within the pots, and no eggs were laid elsewhere. Development from egg to adult was completed successfully in this medium, and a healthy culture of the insect was maintained in the laboratory for several years.

The means whereby sugar-beet yellows viruses and their predominant vector, Myzus persicac (Sulz.), overwinter in Britain are reviewed. M. persicae overwinters mainly on cultivated secondary host plants that are not associated with the viruses: the viruses overwinter principally in the mangold and sugar-beet seed crops, which are the main source of infection in the following summer; mangold clamps may be a minor source and weeds seem unimportant.

Despite autumn certification of first-year sugar-beet seed crops, visible infection within them in the following June is never negligible, and rapid spread of virus within these crops during their second year can cause a high proportion of the plants therein to be infective, although still symptomless. The many aphids that may leave these crops and the uncertified seed crops are an important source of infection for the root crop.

It is suggested as a new control measure that seed crops of beet and mangolds should be grown in Britain in alternate years only. Consideration of the low frequencies of winds of a speed and direction suitable for carrying viruliferous aphids from Continental beet-growing areas to Britain, and of the low incidence of virus yellows in areas of Britain that are free of seed crops and comparable, in distance and direction relative to the main British beet-growing areas, with those of the latter in relation to the Continent, suggests that the effectiveness of the proposed measure is unlikely to be nullified by intrusion of infected aphids from the Continent.

Of 26 amino-acids tested against a solvent control for their attractiveness to females of Aedes aegypti (L.), lysine was the most attractive and six others (threonine, 1-methylhistidine, arginine, tyrosine, glutamine and alanine) were significantly attractive; nine amino-acids were significantly repellent. Lysine converted to the monopicrate, then to the dihydrochloride and then back to the free base was attractive. The degree of attractiveness of lysine was in direct proportion to the amount of uncombined CO2 it inevitably adsorbs. It is also proportional to the amount of carbamino CO2 combined in the molecule. Some commercial samples of lysine contain repellent principles removable by distillation. It is concluded that the attractiveness of lysine to A. aegypti is due to its ability to act as a vehicle for CO2, both adsorbed and in carbamino combination.

Decorticated groundnuts (Arachis) are stored in bags in pyramid-shaped stacks in Northern Nigeria over the period November to October. In Kano the dry season extends from October until March and is followed by a short hot season preceding the rainy season, which usually commences during May.

The seasonal distribution within such pyramids of the various insect species infesting groundnuts is considered in some detail, with particular reference to the primary pest Tribolium castaneum (Hbst.). This distribution is discussed in relation to temperature and moisture content of the kernels and to the effect on the environment of covering pyramids with tarpaulins, the normal practice for protection during the rainy season. T. castaneum is the only species present on groundnuts initially and throughout the storage season. It is concluded that the elimination, during storage, of other species also present initially, i.e., Cadra cautella (Wlk.), Plodia interpunctella (Hb.), Corcyra cephalonica (Stnt.) and Oryzaephihis mercator (Fauv.), and the ultimate concentration of infestation by T. castaneum within peripheral bags is the result of changes in physical conditions. It would appear that Cryptolestes ferrugineus (Steph.), which was not found until late in the storage season, is a pest of secondary importance.

The significance of the results obtained in relation to control measures is discussed, bearing in mind that all but one of the pests considered were found to be present on groundnuts when received at the Kano central storage area from buying stations. It is concluded that a programme of surface spraying of pyramids with insecticides is of little value and recommendations for the introduction of initial fumigation of pyramids have been put forward.

Dispersion behaviour of the adult of the lesser grain borer, Rhyzopertlia dominica (F.), was investigated under controlled conditions by observing the numbers occurring on the surface, or at various depths below it, in small bulks of grain. The effects of population density, temperature and moisture content of the grain on numbers at the surface were studied by using groups of insects in 500 g. wheat, and on dispersion in the vertical plane by confining beetles within a monogranular plate of wheat held between vertical glass sheets, through which the positions of individuals could be observed.

In grain at 25°C. and 14 per cent, moisture content (70 per cent. R.H.), the proportion of a group on the surface averaged approximately six per cent, for densities of 5–100 insects in 500 g., and the proportion was higher than in grain at the same temperature and 9 or 17 per cent, moisture, or at the same moisture content and 15 or 35°C.

In grain of 14 per cent, moisture content, the level of individual locomotory activity increased from 15 to 35°C. At 25°C., locomotory activity was depressed in grain of 9 and 14 as compared with 17 per cent, moisture content. These results are discussed in relation to group formation and dispersal of R. dominica and its contact with Sitophilus granarius (L.) if both species are present in the same grain bulk.

A technique is described whereby a small bulk of grain can be broken down, all insects infesting it recovered and their positions recorded. A Perspex box, 12 inches cube, is loaded with 64 three-inch-cube bags of Terylene net (10 meshes to the inch) each holding 390 g. of Manitoba wheat, and the test insects (adult grain beetles) released on the surface, after which the box is sealed and left in darkness for the required time. The bags are then removed, the insects sieved out, and their numbers and positions recorded, thus enabling the pattern of group dispersion to be plotted. The net used did not appear seriously to impede the movement of the adults of Sitophilus granarius (L.), the largest species used in the study. Temperature gradients may be introduced and measured by thermocouples built into the bulk.

Glossina, palpalis (R.-D.) was studied in three localities near Voinjama, in a forest region in north-west Liberia, where human trypanosomiasis persists only as sporadic cases. Sites were chosen with different degrees of contact between man, fly and game, in transitional vegetation on the Zeliba River, and in primary forest on the Lofa and Lawa Rivers. The general features, fauna and climate of these areas are described. Catching by nets was found to be preferable to the use of traps. Trap catches averaged about one-quarter of the corresponding net catches. The theoretical basis of ‘animal’ traps is too uncertain for their use in quantitative studies, and under forest conditions there are practical difficulties in siting them in optimum positions; they failed to catch at all at very low fly densities. Heavy rain and the dry season were unfavourable to the fly, particularly outside the forest canopy. A wet-season resting site on horizontal twigs near to the ground is described. The percentage of females in the total catch differed significantly between different habitats, but apparently was not indicative of the degree of hunger in the population. There were no great differences between the sexes in activity patterns, and activity was greatest during the apparently unfavourable climatic conditions of early afternoon. The willingness of the fly to penetrate unfavourable surroundings suggests that the clearing of forest at potential places of transmission is unlikely to afford an effective means of protection. There is some evidence that breeding was curtailed during the rains. Very few engorged flies were found. Fly numbers and distribution were not affected by normal game movements. There is no evidence that the fly was ever dependent on man for food. Where game was driven away the fly tended to follow it. Occasional human foci did not affect the number or distribution of the fly, and fly activity was not correlated with human activity. Intimate and prolonged contact between man and fly did not occur.

Fecundity in the garden chafer, phyllopertha horticola (L.), is extremely variable. Fecundity depends entirely on reserves laid down by the larva.

Previous work in Britain showed that (a) early larval feeding periods in the field produce heavy pupae; (b) in an experiment comparing early with late-hatched larvae, the heavier diapause larvae developed from the early batch; (c) in the field, the earliest larvae to enter diapause were the heaviest.

Further data (hitherto unpublished) showed that larvae reared at 25°C. entered diapause heavier than larvae reared at field temperature, although mortality was high. The above data also indicated that time of entry into diapause was fixed and unaffected by temperature.

A repeat of the field experiment (b) showed the same result and also showed how a population of feeding third-instar larvae can be destroyed by frost while larvae in diapause deeper in the soil are unaffected. Thus a late season produces light larvae and a high risk of death before diapause.

Observations on larvae kept at constant temperatures (12, 16 and 18°C.) showed that the temperature threshold of development is about 12°C. in the first instar but is lower in succeeding stages; the length of the first and the second instars decreases with rise in temperature; high temperature probably produces larger larvae by the end of the second instar, but the effect was small and none at all was detected at the first moult.

The length of the third-instar feeding period is not affected by temperature in the range 12–20°C. Kate of growth (increase in weight) increases with temperature. The higher temperatures (perhaps as a result) produce heavy diapause larvae and pupae in both sexes. Entry into diapause is hindered at 20°C. The weight of a larva at the second moult is positively correlated with its diapause weight.

It is suggested that the temperature effects described can be most simply explained by postulating the existence of differential temperature coefficients for the various growth processes.

The garden chafer, Phyllopertha horticola (L.), has been recorded in most counties of England and Wales (43 out of 52) and is probably to be found in all. It is more abundant the warmer and wetter the region, i.e., it is more abundant in the west and south and most abundant in the south-west. It flourishes best in permanent pasture on light soil in hilly country, and occurs from sea-level to an altitude of at least 1,160 ft.

Patchiness in local distribution was investigated on the pastures of fell farms in the Lake District.

An infested fell pasture includes from one to five plant associations which are described as (1) Grass, (2) Sparse Bracken, (3) Bracken Bed, (4) Heath Rush and (5) Common Rush. Typically, all five are present in a pasture. The proportions of ground covered by grass turf (Agrostis-Festuca) in these associations are (1) 100 per cent., (2) 99 per cent., (3) 0 per cent., (4) 80 per cent, and (5) 50 per cent., the grass turf in the rush associations (4 & 5) filling the spaces between clumps of rushes. Soil stages of the garden chafer are found only in the grass turf and so the Bracken Bed association is never infested. In terms of density per unit area of ground, the other four associations exhibit the following relation between their infestations: Grass>Sparse Bracken>Heath Rush>Common Rush. This relation is only partly explained by the similar relation between proportions of ground covered by grass turf (see above). As to other factors that might be partly responsible, no correlation exists between botanical characteristics of grass turf and infestation but there are two negative correlations among physical characteristics which are suggestive: Grass and Sparse Bracken-<Heath Rush and Common Rush with respect to toughness of turf; and Grass<Sparse Bracken<Heath Rush<Common Rush with respect to wetness.

Grassland, an unbroken expanse of grass sward, is, in the Lake District, by far the most important habitat since it carries by far the greatest part of the garden chafer population.

In grassland no evidence was found of an association between density of soil stages and proximity to bracken.

The population of any soil stage, from egg to pupa, is always much greater in drier than in wetter parts of grassland.

Sampling at intervals within a generation indicated that the mortality rate is higher in the wetter parts of grassland. This is not due to any lack of food, or difficulty of utilising it, or to the presence of more enemies (competitors, predators, parasites and pathogens) in the wetter parts, but, as established by laboratory and field experiments, is attributable to a direct effect of moisture. Further experiments suggested that the egg stage is most and the feeding stages are least resistant to excessive moisture.

Field experiments also indicated that the so-called ‘effective bee-liners’, females characterised by a direct and sustained flight from their roosting sites and that lay some eggs far afield, exercise some degree of discrimination in the choice of oviposition sites, the majority tending to choose the drier parts of grassland, the kind of site that does in fact, become more highly infested. Less than a quarter of all females become effective bee-liners and as such lay only about 15 per cent, of all eggs deposited by a population.

There is a dynamic aspect to the phenomenon that population is greater in drier than wetter parts of grassland. Although population is always greater in the drier parts, the magnitude of the population ratio between drier and wetter parts can change considerably from one year to the next as a result of either excessive rain or excessive drought during the larval feeding period. The mechanism of such change is indicated.

Spatial distribution on grassland was assessed statistically by employing Fisher's Coefficient of Dispersion. Eggs, and hence newly hatched larvae, are strongly aggregated. This strong degree of aggregation is gradually lessened, however, by the subsequent wanderings of the larvae in the course of feeding. Nevertheless, even in the final instar, larvae are still appreciably aggregated and hence so also are pupae. By the end of the feeding period, average dispersal from the hatching point is probably not more than 12 inches.

Apart from proper food, which is provided by grassland, the most important living condition for the garden chafer in the soil appears to be proper soil moisture. Although actual limits have not been specified, survival clearly depends on the soil containing neither too much nor too little water for too long.

As regards geographical distribution in England and Wales, the finding that the garden chafer is more abundant the warmer and wetter the climate is explained as follows. Females grow larger, and hence produce more eggs, where the larval feeding period is warmer, and more larvae survive where the climate is wetter, because the greater rainfall means less chance of too little water for an animal that has to live in freely draining soil to avoid too much water.

Fundamentally, the patchy local distribution of the garden chafer is mainly a matter of the patchiness of soil-moisture conditions. The patchiness determined by these conditions is maintained and intensified by the reproductive behaviour of the adults.

Accounts of other species in this and other countries suggest that, for pasture scarabs in general, soil moisture is the chief factor concerned in determining spatial distribution.

A description is given of the life-cycle in Britain of Theocolax formiciformis Westw. (Pteromalidae), a parasite of Anobium punctatum (Deg.) (Anobiidae). Adults emerge from infested wood in large numbers from April to June. Eggs are laid through the wood surface and use was made of this habit as a means of rearing this parasite under observation in the laboratory. Anobium larvae were placed individually in channels gouged in the surface of 3-inch squares of plywood. They were covered with tracing paper and the parasites were caged on this by means of a glass ring covered with a glass plate. Development from egg to adult at 22 and 25°C., and 75 per cent, relative humidity, averaged about five and six weeks, respectively, compared with 12 weeks outdoors in summer. The number of progeny per female was highest (approximately five) at 22°C., at which the ratio of males to females was 1:3. Only about one per cent, of the adults reared were winged. The use of Theocolax as a biological-control agent is not considered practical.

A method of rearing Gryllus pennsylvanicus Burm. is described, designed to yield large numbers of first-instar nymphs of uniform age for toxicological investigations Nymphs are reared to the fourth instar in glass vessels containing a little soil, which prevents cannibalism, and then transferred to glass-topped stock cages having sides and floors of aluminium screening and each accommodating 250 individuals. A mixture of dog-food pellets, oatmeal and milk powder, with fresh oats or clover, is provided throughout as food, and petri dishes of moist fine sand for oviposition. After separation from the sand by sieving, the eggs are incubated in moist soil at 24°C. for one month, subjected to 4°C. for three months to eliminate the obligate diapause, and then returned to 24°C., when 70 per cent, hatch after 15–18 days. The diapause enables eggs to be stored at 4°C. until required. At 24°C., the nymphal stage lasted about 81 days, the adult males and females, which are produced in equal numbers, survived about 62 and 56 days, respectively, oviposition extended over 11 weeks and the average number of eggs laid per female was 970·6.