In a study of the larval feeding preferences of eleven species of Elateridae, representing Lepturoidini, Pyrophorini and Elaterinae, from soil, sand and wood habitats, all larvae were found to feed more on animal than plant food when these were offered separately. When given a choice, the larvae of only one species, Lepturoides linearis (L.), selected animal food exclusively and only those of Limonius minutus (L.) selected plant food exclusively. No consistent relationship was found between food preferences and taxonomic group, habitat, size, or morphology of the sense organs of the species. It is suggested that under laboratory conditions differences in food preferences among species are mediated primarily by differences in the physiology of their sense organs, and these may be an expression of different nutritional requirements among certain species.

The coffee leaf-miners Leucoptera meyricki Ghesq. and L. caffeina Wshbn. are serious pests of arabica coffee in Kenya. At the present time sprays containing parathion, methyl-parathion or diazinon are used extensively for their control.

To facilitate preliminary investigations into various aspects of insecticidal control of the larval stages of these pests, a laboratory bioassay technique was developed. Larvae were reared on detached coffee leaves placed on moist filter paper in plastic boxes. When the larvae were in their third instar, the leaves were sprayed in a Potter tower and then kept in a moist air stream for three days before the mines were dissected to enable mortality counts to be made.

Of 22 new insecticides screened, only Sumithion (O, O–dimethy1 O–(3–methy1–4–nitrophenyl) phosphorothioate) and fenthion gave mortalities higher than those achieved with diazinon. Parathion gave somewhat higher mortalities than methyl-parathion, and emulsifiable formulations of these insecticides were more effective than wettable powders. The inclusion of additional wetting agents increased the efficiency of commercial formulations of these two insecticides. These results are subject to confirmation in field trials.

The mode of action of parathion was investigated. Dosage/mortality lines were constructed for parathion, methyl-parathion and diazinon so that resistance to these insecticides by L. meyricki could be detected should it develop at some future date. L. caffeina was found to be apparently more susceptible to these insecticides than L. meyricki and this was believed to be due to its greater rate of feeding.

A key to the fully grown larvae of 11 species of Phycitinae is given. Of these, the following eight are known in Britain either as stored-products pests or associated with imported food:— Ephestia elutella (Hb.), Anagasta kuehniella (Zell.), Cadra cautella (Wlk.), C. calidella (Gn.), C. figulilella (Gregson), Plodia interpunctella (Hb.), Mussidia nigrivenella Rag. and Ectomyelois ceratoniae (Zell.). The key is preceded by a brief account of the economic importance of these species in Britain.

The other three species are Ectomyelois decolor (Zell.), E. muriscis (Dyar) and Paramyelois transitella (Wlk.). Although these are native to the Americas and are unknown in Britain, they comprise, together with E. ceratoniae, the economically important species formerly of the genus Myelois Huebner.

The larvae of Mussidia nigrivenella, P. transitella and of the three species of Ectomyelois are described.

The nerve sheath of the thoracic ganglion of the house-fly (Musca domestica L.) is readily permeable to diazoxon but is impermeable to acetyl choline and acetyl thiocholine. Acetone and other lipoidal solvents, but not formaldehyde, were found to destroy the barrier to entry of the substrates, acetyl choline and acetyl thiocholine, and it is inferred that the barrier is lipoidal. At − 16°C., acetone does not destroy the cholinesterase of the ganglion.

Cholinesterase associated with the ganglion could be divided into three regions which showed different inhibition characteristics: (a) ‘ superficial ’ enzyme outside the nerve sheath, inhibited by 3·3 × 10−8M diazoxon; (b) ‘ peripheral ’ enzyme in the cellular region of the ganglion, inhibited by 3·3 × 10−8M and 3·3 × 10−9M diazoxon; (c) ‘ central ’ enzyme in the synaptic area, inhibited by not less than 3·3 × 10−7M diazoxon. Using inhibition of cholinesterase as an indicator of penetration, no difference in permeability was found between the ganglia of the susceptible and resistant strains. No difference was found in the inhibition of cholinesterase by diazoxon in the ganglia of susceptible and resistant strains.

It is concluded from this and previous work that if inhibition of cholinesterase of the nervous system is the cause of death there are no differences between the ganglia of the susceptible and resistant strains which affect resistance; and, furthermore, that inhibition of cholinesterase in the thoracic ganglion is unlikely to be the cause of death.

An account is given of the simultaneous control of three species of tsetse fly by the selective application of insecticide to vegetation within an area of 16 sq. miles along a seasonal watercourse in Northern Nigeria constituting a permanent habitat of Glossina palpalis (R.-D.) and G. tachinoides Westw. and a hot-season concentration area of G. morsitans Westw. subsp. submorsitans Newst. The ecological zones concerned centred on small lakes fringed, in succession outwards, by open swamp, swamp woodland, swamp forest, riparian forest and riparian woodland, the whole being bounded by savannah woodland populated by G. morsitans in the wet season. All except the forest elements were subject to seasonal fires.

Against G. morsitans, insecticide was applied to the principal resting sites of flies in their hot-season concentration habitats, namely, the basal 5 ft. of shaded tree trunks over 9 in. in diameter, or 5 in. where stands were dense, in, chiefly, riparian woodland and forest. Against the other species it was applied to a height of 2½ ft. on stems, trunks and exposed roots in riparian forest and the margins of swamp forest, which were favoured as pupation sites and in which it was therefore believed that adults might rest.

A wettable-powder suspension containing 3¾ per cent. DDT was applied by pneumatic knapsack sprayer in quantities short of run-off. Temporary reduction of the strength to 2½ per cent, had no detectable effect on control.

Regular fly patrols showed an initial reduction in apparent density of G. morsitans by four-fifths, but spot checks detected a residual population that persisted up to two months in small areas. These were resprayed so as to include trunks of 5 in. diameter and branches over 3 in. in diameter at heights of 6–12 ft. The apparent density of the other species declined after treatment by over nine-tenths, in both treated and untreated zones, but following catches of a few teneral adults, indicating persistent or recurrent populations in limited areas, these were resprayed using an emulsion containing 3¾ per cent, dieldrin.

Treatment began in January 1961 and to date (April 1963) no fly has been detected since April 1961, despite repeated re-surveys. The approximate cost of labour, equipment and insecticide was £3,000; an attempt at reclamation in 1926–29 by sheer-felling over seven sq. miles, which achieved only temporary success, had cost £3,000, with recurrent annual re-slashing costs of £250, equivalent to £12,000 and £1,500, respectively, at present-day costs for labour.

Fifty-two standardised weekly collections of female mosquitos were made by human catchers at ground-level in lake-side forest near Entebbe, Uganda. The numbers of nullipars and pars in each sample were recorded, in order to determine whether the capacity of these mosquito populations to transmit virus varied seasonally. Methods are described for handling large catches for the purpose of identifying and age-grading. The total sample comprised 31,978 mosquitos belonging to 37 or more species. Results for 15 species are presented in detail.

The nulliparous rate (i.e., the number of nullipars as a percentage of total females) differs markedly between species, but relatively little within species. Certain species of Mansonia (Coquillettidia), mainly swamp breeders, have the highest nulliparous rate, and species of Aedes and Eretmapodites, which breed in small containers, have the lowest. In some species, biting females show a lower nulliparous rate than those caught resting.

Culex annulioris Theo. and species of Mansonia, which are swamp breeders, have a main peak of abundance between May and July, during the main rains and when lake-level is highest. Species of Aedes (Stegomyia), which are tree-hole or small-container breeders, show small, irregular, short-term fluctuations in numbers.

The number of pars, an epidemiologically important parameter, is absolutely highest at or soon after the time of greatest abundance. For certain bird-biting mosquitos, namely, Culex annulioris and species of Mansonia (Coquillettidia), most pars are found during the main rains, when susceptible hosts are also most numerous. Implications of these findings on virus-isolation programmes are briefly discussed.

Brief notes are given on the distribution and habits of 42 species of Scolytidae and 34 of Platypodidae that occur as common forest insects in Ghana. A considerable number of these can be considered as beneficial insects because they do little damage but assist in the rapid break-down of dead trees and felling slash. Others are injurious mainly as timber borers, shoot borers or, generally to a lesser extent, as bark beetles and seed insects. Trachyostus ghanaensis Schedl and Doliopygus dubius (Samps.) are of outstanding importance in their constant or frequent habit of attacking the wood of living trees of commercial value; Platypus hintzi Schanf., Doliopygus conradti (Strohm.) and D. brevis (Strohm.) are probably the most important ambrosia beetle borers of newly felled timber; and Xyleborus semiopacus Eichh. has been known to destroy whole plantations of young forest trees.

Populations of the wingless form of Myzus persicae (Sulz.), infected with severe yellows (SBYV), mild yellows (SBMYV), and both viruses, were introduced to single sugar-beet plants which were growing in a normal crop.

The aphids and their progeny walked readily from plant to plant, both along and across the rows, during the following eight weeks. Although they were heavily attacked by ladybirds, their mobility saved the population from total destruction. They carried and transmitted the viruses; within a month patches of sugar beet more than 11 feet in diameter had become infected, and within two months the diameter had extended to about 20 feet.

SBMYV spread to more than twice as many plants as SBYV. When introduced alone, either virus spread to twice as many plants as when the two viruses were introduced together. The rate of increase of the infection fell off during the season; it was estimated as eight- to sixteen-fold per month in June—July, about three-fold in August, and 1·5- to 1·9-fold in September. Natural infections-appear to behave similarly.

Apterae of M. persicae are considered to be predominantly responsible for yellows virus transmission within the crop, and their mobility, in contrast to the immobility of those of A. fabae Scop., is considered to be the principal reason why M. persicae is a much more important vector than A. fabae.

The extent of spread of virus by apterae shown to occur in the root crop must inevitably be much greater in the seed crop, in which aphid populations are much higher. This consideration serves to explain why existing control measures in the seed crop do not protect the root crop from infection. The risk from the seed crop, which is the reservoir of the disease, would be countered if seed crops were grown only in alternate years.

Dispersion behaviour in adults of the saw-toothed grain beetle, Oryzaephilus surinamensis (L.), was studied under controlled laboratory conditions. The effect of density, temperature and moisture content on surface dispersion was studied using groups of insects in jars of 500 g. grain and vertical dispersion by using groups of insects in thin vertical plates of wheat held between two sheets of glass. The ethological basis of group behaviour was investigated by using isolated individuals.

Over the range of conditions used, 1–10 per cent, of the individuals comprising the groups studied appeared on the surface of the grain. In grain at 14 per cent, moisture content, at 25°C., 3·4 per cent, of the group appeared on the surface. A greater proportion was found on the surface of grain at 9 per cent, moisture content than at higher moisture contents at all temperatures tested (15–35°C.). At all moisture contents, surface numbers were relatively high at 15°C.

In grain at 14 per cent, moisture content and 25°C., individuals moved vertically and laterally at random but were more active in the evening than in the morning. In grain at 9 per cent, moisture, there was marked irritability, and at 15°C. and 14 per cent, moisture, there was continual but slow movement without any detectable diurnal pattern of activity. Activity was reduced at 30°C., and at 25°C. it was reduced in grain of 17 per cent, moisture content.

The significance of these results is discussed in relation to the detection of populations, group formation and the initiation of foci of heating in patches of damp grain.

The dispersion behaviour of Tribolium castaneum (Hbst.) and Cryptolestes ferrugineus (Steph.) was studied under controlled laboratory conditions. The effect of density, temperature and moisture content of grain on surface numbers was studied using groups of insects initially placed centrally in jars containing 500 g. wheat and vertical dispersion was studied by observing groups of insects in a thin plate of grain held vertically between two glass sheets. The underlying behaviour of group dispersion was studied, using isolated individuals. Over the range of conditions used (15–35°C, and 9–17 per cent. moisture content), 14–49 per cent. of groups of Tribolium and 0·2–4·0 per cent. of Cryptolestes appeared on the surface. Surface numbers in both species were depressed at each end of the temperature range. In the middle of the temperature range, more individuals of Tribolium were found on the surface in grain at 17 per cent. moisture content than at 9 per cent., the reverse being found with Cryptolestes.

Analyses of locomotory activity in Tribolium showed that in all conditions females moved around less than males. For both sexes, activity was relatively depressed in the driest grain and at the lowest temperatures. Change in position within the grain was almost totally absent at 35°C. although locomotory activity remained relatively high. In Cryptolestes, locomotory activity was likewise depressed at the lowest temperature but both sexes moved around apparently at random in grain at 14 per cent. moisture and 30°C. In grain at 9 per cent. moisture, nearly all individuals became inactive within 24 hours. These results are discussed in relation to the onset and detection of infestation in grain and to the associations of grain-infesting species.

A short history of the study of the six tsetse species of the group of Glossina fusca (Wlk.) that occur in Nigeria and the former British Southern Cameroons (now West Cameroun, part of the Federal Republic of Cameroun) is given. Extensive collections of these species were not made until after the scheme for the establishment of the West African Institute for Trypanosomiasis Research was initiated in 1947. More intensive studies, stimulated by the discovery of a technique of searching for the flies in their resting sites, were carried out in southern Nigeria, at the W.A.I.T.R. Field Station and elsewhere, from 1953 onwards.

The situation, climate and vegetation zones of Nigeria are described. Species of the fusca group occur only in the southern part of Nigeria and in West Cameroun and depend on some type of forest vegetation, ranging from relatively dry forest islands and riverine forest in savannah to dense, humid, wet rain forest, for their habitat. Rainfall and relative humidity, in general, decrease with increasing distance from the coast and are factors of great importance in determining the distribution of the fusca group.

Locality records for each species of the fusca group are listed according to the Province and nearest town or village to the place where they were collected, and the results are shown on maps. G. medicorum Aust. has only been recorded from the relatively dry northern part of the rain forest and forest islands or riverine forest in savannah in Western Nigeria. G. nashi Potts occurs in dense, wet rain forest in West Cameroun. G. tabaniformis Westw. occurs, especially, in forest reserves in Ondo and Benin Provinces of Western Nigeria and in wet rain forest in West Cameroun and adjoining forest country in Eastern Nigeria. G. haningtoni Newst. & Evans is common in wet rain forest in West Cameroun and there are also records 175 miles to the west in Delta Province of Western Nigeria. G. fusca occurs in a wider range of climatic conditions and habitat types than the other species; it has been recorded in vegetation varying from forest islands in savannah to wet rain forest. G. nigrofusca Newst. is a rare but widespread species in Nigeria and West Cameroun where it occurs typically in wet rain forest.

The dry and wet limits (indicated by mean annual rainfall) of the distribution of each species in Nigeria and West Cameroun are given, and the importance of climate, especially humidity, in determining these distributions is discussed. The climatic requirements of the six species are confirmed by their distribution outside the boundaries of Nigeria and West Cameroun. G. medicorum extends mainly to the west of Nigeria although there are also two records of the species from Gabon, widely separated from the main area of distribution of the species in West Africa. G. haningtoni and G. nashi, species typical of Central Africa (as here defined), extend only to the east and south of Nigeria (south in the sense of south of the latitude of Nigeria in territories in Central Africa). The remaining three species, those which occur in both reasonably dry and reasonably wet forest conditions in Nigeria and West Cameroun, extend both west and east and south of Nigeria and West Cameroun.

Some type of thicket or forest vegetation is the essential habitat for the survival of all six species of the fusca group. The main areas inhabited by the fusca group now are forest reserves in Western Nigeria and the relatively undisturbed forests of West Cameroun. The species are absent from much of southern Nigeria, and it seems certain that the increase of the human population over relatively recent times, and the effects that this increased density of population has had on the flora and fauna, has been the cause of the present-day discontinuous distribution of the fusca group in southern Nigeria. Man has an adverse effect on fusca-group tsetse populations through clearing of forest vegetation and the hunting and driving away of the game animals on which the flies depend for food. An inverse relationship between human population density and the number of records of the fusca group over southern Nigeria and West Cameroun is demonstrated.

Among larval populations of the mosquito Opifex fuscus Hutton from supralittoral pools on the east coast of South Island, New Zealand, some individuals in the second, third and fourth instars had only simple hairs in their mouth-brushes, others had pectinate bristles. All first-instar larvae had simple hairs, and samples of these from the same pool were reared in the laboratory at 25°C. Of 13 fed on dehydrated blood serum, only two developed pectinate bristles, but of 15 fed on fish food (particle size 0·1–0·6 mm.), all but one did. Of a later sample of 16 reared at room temperature on fish food in the first two instars and then on the blood serum, all developed pectinate bristles in the second instar but had reverted to simple hairs by the fourth. In nature, larvae of O. fuscus observed to be feeding by filtering were predominantly of the simple-hair type and those browsing of the pectinate-bristle type. Environmentally controlled dimorphism may increase the probability that an individual will develop to maturity.

Investigations have been made on the influence of environmental conditions on the contact toxicity to adult mosquitos (Anopheles stephensi List.) of two kinds of insecticidal deposits of importance in sprayed houses, superficial deposits from wettable powders and insecticides sorbed on dried soils.

Increasing the relative humidity from 43 to 80 per cent, during the contact period had no effect on the toxicity of wettable-powder deposits on plywood of dieldrin, Sevin and O-methyl O-(2,4,5-trichlorophenyl) ethylphosphoramidothioate. On the other hand, the availability of DDT, dieldrin and 3-isopropylphenyl N-methylearbamate sorbed on dried soils increased considerably as atmospheric humidity increased. The logarithm of the median lethal exposure time was linearly related to atmospheric humidity, and decreased by a factor of 2·8, 2·2 and 2·1 for the carbamate, dieldrin and DDT, respectively, for each 10 per cent, increase in relative humidity. There was also a linear relationship between the logarithm of the water uptake of a given soil and humidity.

Temperature affected the action of insecticides during both the contact period and the post-treatment period. Median lethal doses of dieldrin, Sevin and the phosphoramidothioate decreased, and that of DDT increased, as the post-treatment temperature increased from 20 to 30°C. These effects of the post-treatment temperature were also found when treatment was by exposure to residues. When these effects were eliminated it was found that the contact toxicity of superficial deposits on plywood and of insecticides sorbed on dried soils increased as the temperature during the exposure period increased. A simple relationship between median lethal time and exposure temperature was indicated.

Brief notes are given on five species of boring insects that attack date palms in Iraq and between them cause considerable damage, based on observations in 1957–62. They comprise the Pyralid Arenipses sabella Hmps., the larva of which mines the spathes and fruit stalks, preventing fruit maturation; the Cerambycid Pseudophilus testaceus Gah., the larva of which mines the frond bases and stem;the Dynastid Oryctes elegans Prell, of which the adult makes a surface mine in the frond mid-rib or fruit stalk and the larva develops, usually, inside the stem of dead or moribund palms; the Bostrychid Phonapate frontalis (Fhs.), which mines in the frond mid-rib; and the termite Microcerotermes diversus Silv., which makes covered galleries up the outside of the stem and mines within the stems and frond bases of weakly palms.

In its potential outbreak areas in Northern Ehodesia and Tanganyika, sexually immature populations of adults of Nomadacris septemfasciata (Serv.) tend to concentrate in the islands of grass that remain unburnt after the annual fires that occur during the dry season. The locusts use the tall grasses as roosting sites and descend in the daytime to feed on adjacent short grasses, where these occur as constituents of an internal mosaic within the islands, or, in the case of islands composed wholly of tall grasses, on the fresh grass-shoots on the burnt-over ground surrounding them.

Two methods are described whereby emulsified solutions of dieldrin were applied in the Central Bukwa plain, Tanganyika, in 1960 as a stomach poison at dosages of 2·9 and 4·5 oz. active ingredient per acre from aircraft to the whole of individual islands showing the internal mosaic pattern (4 trials) or at 2·9, 4·5 and 8·2 oz. per acre to a swath 20 or 40 yd. wide around the perimeter of tall-grass islands (8 and 4 trials, respectively). Results were assessed by counting the numbers of locusts flushed by a vehicle driven along strips parallel to one another and 0·1 mile apart, and checked by counts of dead locusts. Mortality reached at least 90 per cent, within four days, at either dosage, following the first method, and 21–89 per cent, within 14 days following the second, being significantly greater at the higher dosages but not with the wider swath.

These results are compared with those obtained in preceding years by the standard method of applying DNC from aircraft at 20 per cent, in oil as a contact insecticide; in the latter case, the cost of insecticide was more per acre sprayed, but less per 1,000 locusts killed because the density (5 locusts per sq. yd. of grass island) in the trials was greater than in those using dieldrin (1 per 3 sq. yd.). Even so, when dieldrin was used, many more locusts were killed per sortie flown, and the total cost (of flying plus insecticide) per island was much less, and per 1,000 locusts killed very much less, than in the standard method, which nevertheless has to be used against mobile swarms because DNC is quick acting.