Studies were carried out in Jamaica on the larval biology of Leptoconops becquaerti (Kieff.) in 1962–63.

Larvae were reared on natural breeding sites in chambers constructed from large tins, by methods that are described in detail. The features of the breeding sites are illustrated and briefly discussed.

The developmental period from egg hatching to adult emergence probably occupies four to eight weeks, depending to a certain extent upon temperature and hence on time of year. It is unlikely that the adult stage is ever reached in much less than three weeks under natural conditions. Under experimental conditions, overall survival to the adult stage was frequently greater than 20 per cent., and occasionally over 50 per cent. It is considered that survival in natural populations is probably also quite high.

Larval mortality in the experimental chambers apparently occurred maintly in the first instar, and this probably happens in nature. The results showed a relationship between percentage survival and egg number such that proportionately fewer adults were obtained from chambers with greater numbers of eggs. This was interpreted as being due to progressively more severe starvation of very young larvae in the more crowded chambers.

There was no marked tendency for adults of the more same sex to emerge first in the chambers. The sex ratio among the total of 1,039 adults obtained was 1:1.

In an experiment to investigate the diel rhythm of adult emergence, 71 per cent. of adults of L. becquaerti emerged in the four-hour period of 0300–0700 hr., and a further 27 per cent. appered between 0700–1100 hr. This is earlier than found in Culicoides furcns (Poey) in a previous experiment.

Emigration of moths of the Noctuid Spodoptera exempta (Wlk.) from their developmental sites occurred within a few hours of emergence, and captive moths have lived in semi-outdoor conditions for several weeks. Flight has been recorded at all times of night in the Kenya highlands, and has shown a very marked association, seasonally, nightly and even hourly, with rain; it has been observed at temperatures down to 13°C, and inferred at temperatures several degrees lower, so that over the greater part of eastern Africa flight activity is very unlikely to be restricted by low temperatures.

The breeding season of S. exempta differs markedly and consistently in different parts of eastern Africa; outbreaks of larvae recorded over the past forty years in Kenya, Tanzania and Uganda have been confined to November-July (very largely to December-May), alternating with those recorded over the past twenty years in Ethiopia, which have been confined to March-December (very largely April to August). The progressive establishment of a network of fifty light-traps in these countries since late 1962 has repeatedly recorded the arrival of invading moths before the first infestations of larvae, and has also provided evidence of a strikingly complete seasonal evacuation of much of the region; all traps in Kenya and most of those in Tanzania have revealed a period of several months in every year without a single moth of S. exempta.

Seasonal successions of moth catches and outbreaks of larvae have provided repeated evidence of a progressive northward movement of populations of S. exempta, developing in March in Tanzania and Kenya, and extending across Ethiopia, in some years as far as northern Eritrea by June. The extent of these inferred displacements is consistent with the evidence so far available on behaviour and other factors affecting range of flight, which has been examined in as much detail as the limited data permit.

Evidence of a return migration southwards to Kenya and Tanzania is relatively scanty. There are some indications of a north to south sequence of moth catches and outbreaks; the heaviest infestations in Kenya and Tanzania during the four-year period of detailed study were preceded by the largest catches so far recorded at the relevant time of year in Ethiopia; and in several years the first moths arriving in Kenya and Tanzania, in November-December, have appeared with the onset of the north-east monsoon, representing the southward movement of the intertropical convergence zone. Conversely, appearances of moths towards the northern limits of their inferred seasonal migration, in Ethiopia and around the Gulf of Aden in June, have shown an analogous association with the establishment of the south-west monsoon, i.e., with the northward movement of the intertropical convergence zone. Brief reference is made to evidence of seasonal migration in other parts of Africa; possibly in some years the eastern African populations may be supplemented by migrants from the south.

Two recorded moth ‘ swarms ’ have been associated with weather systems characterised by particularly vigorous wind-convergence. It is suggested that wind-convergence may have contributed to the density of the ‘ swarms ’ and of the subsequent infestations of larvae.

The overall effect of the seasonal changes in distribution which have been demonstrated is to bring the population into areas experiencing seasonal rains. Such a pattern of seasonal migration is likely to be of particular survival value for grass-eating insects, and such concentration of the insects as may be attributable to the associated wind-convergence may be significant in relation to the status of such insects as pests of cereal crops.

Records in the literature of long-range geographical displacements of some other Lepidoptera have been found to be associated in a similar manner with analogous systems of wind and weather in other parts of the world.

The inheritance of carbamate resistence in the Fc strain of Musca domestica L. was investigated by the method described by Nguy & Busvine (1960) and more than one gene, most probably two genes, were found to be responsiple for carbamate resistence. A further experiment showed organophosphate and carbamate inheritance to be linked. As it was already known that the genes for organophosphate resistence were on the third and fifth chromosome, the third and fifth chromosomal resistence factors were separated by use of marker genes. Both factors gave low to moderate levels of resistence to organophosphates and carbamates. The third chromosomal factor appeared to be associated with increased oxidative activity and the fifth chromosomal factor with a modified aliesterase mechanism. The effect of the two genes was cumulative.

Larvae of Arenipses sabella Hmps., a serious pest of date palm trees in Israel, developed normally on inflorescences, immature or ripe rates and on green fruits of Phoenix canariensis, and their development at 30°C. took 34–45 days. Survival of males and fertilised famales was 10.8–12.0 days at 25°C. and 7.0–8.2 days at 27°C. No difference was found between survival of males and females, but unfertilised females lived rather longer than fertilised famales. The total production of eggs per female was 285 eggs at 25°C. and 328 at 27°C. At 25°C. 825 per cent. of the eggs were laid during the sixth and seventh nights of the female’s life, at 27°C. 74 per cent. were laid during the third and fourth nights. The total number of eggs laid by unfertilised females was lower than that of fertilised ones. The number of females fertilised was dependent on the number of males present in the rearing cage.

In Israel, only two generations of A. sabella— those in the spring and in the late autumn—become sufficiently large to be of economic importance. Damage occurs during only a short period in spring, when inflorescences, toung fruits and fruit stalks are attacked. In autumn and winter most larvae enter diapause. In the laboratory, the moth passes through four generations a year and even at the relatively high temperatures maintained during the winter the larvae entered a diapause.

Cadra figulilella (Gregson) is a serious pest of ripening dates in Israel and damages fruit still on the tree and also after it has been picked, if it is not then fumigated.

The time taken for development at 30°C. was 54–65 days. At this temperature adults lived for 4–6 days and the average number of eggs laid per fertilised female was 160. Unfertilised females laid fewer eggs. Most of the eggs were laid during the second and third nights after emergence of the female. The number of fertilised females depended on the number of males present in the rearing cage.

A few larvae were observed in the plantation in dropped, decaying dates throughout the year, but attack on the bunches started only when the fruit began to ripen.

Azinophos-methyl (E.C.20%) 0.5 per cent. and diazinon (E.C.25%) 0.5 per cent. were the most effective of the compounds tested. Application when the colour of the fruit began to change and again three or four weeks later resulted in excellent control of the pset.

An account is given of the life-history of Agrilus acutus (Thnb.) (Buprestidae), a pest of ‘mesta’ (Hibiscus cannabinus) in india. The eggs are ovate and scale like, and are laid singly on the stem, usually near a leaf scar, and when kept at 31°C. and 73 per cent. relative humidity hatched on average in 12.4 days. The larva bores through the lower surface of the egg directly into the stem and feeds under the bark forming a sprial tunnel. A raised weal develops on the surface of the stem overlying the tunnel. Before each moult, the larva bores into the wood and makes a vertical chamber in which moulting occurs. There are normally three moults in the active feeding stages, but exceptionally four, and a prepupal moult. The rate of tunnelling is at first about 56 mm. per day and later eaches about 107 mm. The larval stage lests 26 days. The fully grown larva is 21 mm. long and bores into the wood to pupate, making a pupal chamber 11 mm. long into which it fits itself by adopting an asymmetrical U-shaped posture. After a prepupal stage of 2.5 days it pupates. The pupal period occupies about 11.7 days and a further seven days are spent by the adult in the pupal chamber. The adult female mates within a day of emergence from the stem. but does not oviposit until at least seven days have elapsed.

The effects of infestation by Contarinia nasturtii (Kieff.) on the growth and yield of swedes were observed in a centric-systematic-area sample consisting of 720 individually tagged plants. Severe infestation by the first generation caused multiple haeding and some reduction of yield, though it was attack by the second generation that more strongly depressed yield. From the results of laboratory experiments described it is inferred that it should be possible to achieve satisfactory control by simple cultural procedures designed to bury the pupal cocoons too deeply in the soil to permit successful emergence of the adult midges.

A new Japanese species of Atherigona Rond., A. shibuyai sp.n., described from material reared from sugar-cane.

Field studies on the biting habits of Culicoides barbosai Wirth & Blanton were made near Montego Bay, Jamaica, during 1959 and 1960. Females of C. barbosai were collected in sufficient numbers for analysis in. seven experiments, six from Florida beach and one from Beading. Four positions were marked out on each site. Begular meteorological observations were made in the middle of the catching positions. An experiment consisted of four trials held on different days, each trial being composed of four collecting periods of 15 min. separated by 5-min. intervals. In each period four individuals collected, two exposing an arm each and two a leg. Individuals collected in a different position in each period of a trial.

Catches were logarithmically transformed for analysis and tests of significance. The experiments were designed to provide correction factors for limbs, positions on Florida beach, and collectors, for use in other experiments. Correction factors are given as logarithms for application to transformed catches.

More C. barbosai were collected from arms than legs, and catches in position IV were significantly higher than those in positions I, II and III. Five collectors (C, D, K, L and S) were compared. The ratio between leg/arm catches from D, who collected in only two experiments, was significantly different from those of C, L and S. The differences between the catches of C, K and L were insignificant, but all three caught significantly more than S. The catches from L were smaller after sea bathing and, compared to C and S, L’s catches increased significantly immediately after sunset. For this reason and to avoid inhibiting winds, quantitative studies on females of C. barbosai are best conducted in the early morning (dawn + 40 min.).

The experimental errors (residual variances) were homogeneous with probabilities of 0.1 (C. barbosai—7 experiments) and 0.4 (C. furens (Poey)—8 experiments).

Specimens of seed bugs are recorded as pests of groundnuts, sorghum and cotton in Africa, usually under the name Aphanus apicalis Dall. or Rhyparochromus apicalis (Dall.). It is shown that these pests belong to the genus Naphius Stål and, further, that not all should be placed in the species N. apicalis (Dall.). A study of the genus Naphius shows that there are seven distinct species in the Ethiopian region. The true N. apicalis is shown to be the species that is known to cause damage to pumpkin in Rhodesia and sorghum in Nigeria: the pest of groundnuts in Senegal and Gambia is N. zavattarii (Mancini), not N. apicalis. To date, the other species of Naphius in Africa are not reported as pests. The known distribution of the two pest species is illustrated; N. apicalis occurs throughout tropical Africa, but N. zavattarii seems to be confined to the northern and eastern parts of Africa south of the Sahara, with the latter also present in the Canary Is, and cape Verde Is.

In an attempt made in 1966 to reduce the tsetse fly population in an experiment area of eight square miles in northern Tanganyika to a density low enough to permit safe settlement, undiluted technical fenthion (95% active ingredient) was applied three times at three-week intervals at 0.0041 gal. per acre from a Cassna 185 aircraft fitted with rotary atomisers. The total cost was £95 per sq. mile. Catches in the four weeks immediately following treatment on a flyround of 23,500 yd. sampling the area showed a reduction of over 90 per cent. when compared with those in the four weeks preceding treatment in the case of Glossina swynnertoni Aust. and G. pallidipes Aust. Five months after spraying, the reduction of the former species still exceeded 80 per cent, and that of the latter, 90 per cent. The reduction was smaller in G. morsitans Westw., the most numerous species; a fourth application would probably have improved the kill. The results are compared with those of an earlier experiment in the same area using endosulfan. Some settlement took place in the part of the area where G. swynnertoni predominated.

Sufficient pupae of G. pallidipes Aust. for testing were available from the Zambezi valley only between September and early November and were of all ages. These pupae or the adult fly were exposed to gamma-radiation from a 60Co source at rates between 54 and 122 rads per min., and reproduction and mortality were studied by described procedures.

Effective pupal mortality due to radiation increased, and the proportion of males among the viable emerging flies decreased, with dosage between 4,000 and 16,000 rads. Eeproduction and survival of adult males emerging from treated pupae decreased with an increase in dosage and a decrease in pupal age at the time of treatment. Irradiation of adult males within three days of emergence produced slightly lower levels of sterility and similar survivals. Complete male sterility was rarely obtained with any of the treatments, though all the females, with one exception, were sterilised from 4,000 rads upwards, but the flies were fully competitive with untreated males and reduced reproduction below expected values. Treated males were fully capable of inseminating female flies and the sperm was motile and apparently behaved normally. Dominant lethality in the males appeared to be expressed by the failure to produce pupae and in the females by the complete failure of oogenesis.

Laboratory studies were undertaken to find out if the increased degree of infestation by certain moth species, Cadra cautella (Wlk.), plodia interpunctella (Hb.) and Corcyra cephalonica (Stnt.) following the chemical control of beetles including Tribolium castaneum (Hbst.) in stacks of groundnut (Arachis) in Nigeria could be due to relaxation of inter-specific competition.

All test insects were reared and studied at a constant temperature of 25.5°C. and 70 per cent. ralative humidity. All experiments were conducted on shelled nuts (or germs of nuts) in specimen tubes, crystallising dishes or jam jars. The survival and development of the immature stages of the moth species was studied and the numbers of eggs laid by the adults recorded in the presence of adults of T. castaneum; the reciprocal effects of moth larvae on T. castaneum were also briefly studied.

The most important harmful effects of T. castaneum were on copulating moths and on moth eggs. Adults were frequently disturbed and sometimes killed or, if they survived, laid fewer eggs; eggs were also eaten, especially those laid loose in the medium. Adults of T. castaneum also attacked and killed moth larvae and pupae, but this was considered to be of minor importance. The silk produced by moth larvae was inimical to larvae of T. castaneum, but the effect on the population of T. castaneum was probably offset by the beneficial effect of moth cocoons, which provide shelter for larvae of T. castaneum from cannibalism.

It is conculaded that as a result of competition for food and/or space between T. castaneum and the moth species the moth populations are likely to be exterminated despite their apparently higher intrisic rate of increase.

No method has so far been available for the laboratory culture of Pachydiplosis oryzae Wood-Mason or for the controlled infestation of rice plants with this pest. Suitable techniques for the above have been developed and are described.

For the laboratory culture of P. oryzae, exposure of rice seedlings to gravid females for oviposition and the subsequent maintenance of the plants at a very high humidity in a mist chamber gave high infestation rates but results were not consistent. But this method is suitable for the maintenance of a laboratory culture of this insect.

A special oviposition tube was developed for inducing oviposition on limited areas of muslin, and this permitted easy observation, collection and handling of eggs.

It was found that oviposition tended to occur most frequently between 1900 and 2200 hr. and that the midges most commonly laid 200–285 eggs.

Eggs developed normally and hatched after seventy-two hours when the muslin carrying them was kept on barely moist filter paper in petri dishes.

Sixty-hour-old eggs could be stored for up to five days at 80 ± 2°C. with the percentage hatch decreasing gradually from the first to the fifth day. Low temperature affected development and hatching of thirty-six-hour-old eggs more severely, and hatching was completely inhibited if eggs of this age were exposed to this low temperature for more than two days. Hatching was normal when eggs were maintained at relative humidities of and above 88.8 per cent., but below this level some eggs collapsed as a result of desiccation. At relative humidities below 94.8 per cent., larval movement was initially limited and thereafter inhibited and the larvae were contracted. Such larvae resumed normal activity on immersion in water. These immobilised larvae, obtained by exposure of fully developed eggs to a relative humidity in the range 92.9–94.8 per cent., could be revived by immersion in water and used for infesting paddy plants.

Fully developed eggs, freshly hatched larvae and larvae subjected to relative humidities in the range 92.9–94.8 per cent. and subsequently revived, were transferred to rica plants bt spraying, or by pipetting on the leaf at the ligules or by pipetting on to the soil at the bases of plants. All these mathods proved successful but pipetting on to the soil between rows of plants was the simplest and is to be preferred for controlled infestation of plants.

A very high relative humidity and wet plant surfaces as obtained in the mist chamber used in these studies were essential for successful infestation of rice plants by the gall midge larvae.

Investigations, using tantalum-182, into the behaviour of Glossina morsitans Westw. in large field cages are described. Individual straight-line displacements occurred on average about every three hours and were generally small and erratic in direction. The perimeters of the cages tended to ‘ trap ’ an enclosed population, but flies appeared to move to the walls more quickly when they were shaded by an outer covering of hessian. Horizontal distribution and movements of flies did not appear to be associated directly with the enclosed vegetation, artificial roosting sites or host animals. Observations on vertical displacements indicated diurnal movements to and from boles of trees and changes in roosting heights. The majority of flies rested between six and ten feet above the ground, though individuals were seen from ground level to 30 ft. Few observations were done at night, but two flies were seen on the underside of leaves.

The species of Sesiidae reared from larvae feeding in the vines and tubers of sweet potato (Ipomoea batatas) in Kenya are described as new and named Synanthedon leptosceles and S. dasysceles, respectively. Illustrations are given of the adults and male and female genitalia of both species. S. leptosceles is differentiated from the superficially similar East African species S. erythromma Hmps., which also is associated with sweet potato. Aegeria pyrostoma Meyr. is synonymised under S. erythromma following the examination of type material. S. dasysceles is noted to be readily distinguishable from these and other known species of Synanthedon by the rough scaling and white markings of the legs.

Virgin females of Glossina morsitans Westw. derived from pupae collected on the field were exposed in the laboratory to virgin sterile males and later to virgin normal males; the resulting productivity was an indication of multiple mating by females. Females inseminated once with sterile sperm and then held for 0, 24 or 96 hr. before being allowed to mate with fertile males produced about equal numbers of progeny 29–56 days later; however, subequal numbers of progeny were produced the first 28 days after the initial mating because of the relationship between the time of the second insemination and ovulation. Females given the opportunity to mate repeatedly for 96 hours with their first mates also mated again with new groups of males, but the incidence of this second mating was lower. Thus, multiple mating of females in the laboratory is established, but its frequency in nature is unkown.

When groups of males were exposed to successive new groups of virgin females, the minimum mean number of females inseminated per male renged from 4.9 to 5.6. However, the later inseminations were progressively less effective, and once the complement of sperm of an individual male was depleted, fertility was not recovered. The multiple mating of male and female G. morsitans is not expected to affect the use of sterile males for population control.

The feeding of Eupteryx melissae Curt. (Cicadellidae) on the leaves of ssge gives rise to the appearance of chlorotic spots, as a result of damaged mesophyll cells becoming filled with air. The length of the mandibular stylets in this species (as averaged from the adult and five nymphal instars) is 67 per cent. of that of the maxillaries, both types of stylet being slightly larger in females. The mandibular stylets when inserted do not penetrate much below the leaf surface where they are held by barbs and a salivary sheath, and the total extent of their insertion is only 29 per cent. of that of the maxillary stylets. The latter are the main penetrating organs; the stylets may move together or independently and are not surrounded by a sheath. Mandibular and maxillary penetration is greatest in fifth-stage nymphs, the mean (and maximum) distances being 97 (205)μ and 177 (340)μ respectively. It increases progressively from the first nymphal stage, and in the adult shows mean values near those of nymphs in the third or fourth stage. Rate and depth of stylet penetration is very variable, due to repeated maxillary protraction and retraction, and there is little correlation between the lengths to which the mandibular and the maxillary stylets are extended. Exuvial stylets, particularly the mandibulars of fifth-stage numphs, consistently show a graeter degree of extruction than is to be found in nymphs when feeding normally: such deeper insertion may help to anchor the insect more firmly during ecdysis.

Stylet insertion is by pressure, intracellular, and very rapid (attaining rates up to 115μ per minute). The sex of the individual insect and the leaf-surface attacked have no effect on depth of penetration, at least in certain nymphal stages, and all tissues of the lamina are available for feeding, even to first-stage nymphs, in consequence of the relatively greater development of the stylets in the younger insects. During penetration the mandibular stylets move alternately and initially lead, but quickly come to rest, and further penetration is by the maxillaries which follow a mainly intracellular path. Protrusion of one maxillary stylet beyond the other (up to a maximum distance of 112μ.) was observed in plant tissue and observations of feeding on stripped epidermis show that such a stylet can empty cells at its apex. Protoplasts are removed from a cell within a few seconds, and as this appears to be too short a time to allow digestion, it is assumed that chloroplasts must be mechanically fragmented on passage into the food canal. Removal may be a two-stage process, and if it is assumed that sometimes only the first stage is completed, and is accompanied by saliva injection, it is possible to explain the occurrence, as unimbibed residue, of plasmolysed degenerating chromophilic cells scattered throughout damaged tissue, which occurs mainly in the palisade and spongy parenchyma, and only seldom in vascular tissue. There is no evidence for diffusion of any salivary toxin from damaged cells or from the sheath. Stylet-tracks in damaged areas are unbranched and short and rarely give any indication of the cells fed upon or of the repeated probing by the maxillary stylets that is known to occur.

Detailed descriptions are given of the adults, larvae and pupae of Mallophora media sp.n., Asilidae, which occurs in Trinidad, W.I. The larvae live in the soil and prey upon larvae of Scarabaeidae. The affinities of the new species are discussed.

Investigations into the survival and breeding of the tsetse fly Glossina morsitans Westw. in large and small cage volumes under insectary and ambient climatic conditions in the Zambezi valley, and using oxen as host animals, are described. Under ambient conditions, flies emerging from puparia collected at Kariba, and held in the insectary, survived longer than flies emerging from puparia collected at Chirundu. Flies caught from the bush did not live as long as flies emerging from puparia held in the insectary, and generally lived longer under variable than under constant climatic conditions. The survival of ‘ wild ’ flies decreased during the hot, dry months under ambient conditions. Flies lived longer and were more reproductive in small cages than in large cages. Reproduction in small cages was higher when the flies were exposed to a variable climate instead of controlled conditions, but two colonies of ‘ wild ’ flies declined under both climatic conditions. Eeproduction was better in the small, standard cages (8 × 8 × 11 in.) than in Petana boxes, while Geigy 25’s were intermediate in this respect, but survival and mean puparial weights tended to be similar. The results show a complete failure to breed G. morsitans in large cages.

The increase in tolerance to topically applied chlorinated hydrocarbon insecticides shown by pregnant female tsetse flies was investigated in Glossina pallidipes. Solvent extracts of male and pregnant female flies, traeted with DDT and endosulfan labelled with carbon-14, were analysed by thin-layer chromatography and autoradiography of the developed chromatograms. No metabolites of these compounds were detected in the internal and faecal extracts. It was considered, therefore, that detoxication of absorbed insecticide was not the machanism responsible for the lower susceptibility to insecticide in the pregnant female fly. It was shown, however, by the above technique, that insecticide was absorbed by the in utero larva.

Measurement of labelled DDT absorbed by the larva was carried out by liquid scintillation counting. The results indicated that this insecticide was slowly taken up by the larva, in an amount increasing with time, and it was suggested that inert storage of toxicant in the larva is a pregnant female. This would be in addition to the effects of increase in weight and other possible physiological factors.