A range of insecticides were tested on a resistant strain of bed-bugs (Cimex lectularius L.) from Israel. Resistance was restricted to organophosphorus compounds. Only some of the phosphorothioate compounds were involved, but there was no simple indication of the resistance mechanism on basis of structure of the compounds.

Nine malathion analogues were tested on the bed-bugs, and relative levels of resistance to them compared with insect strains specifically resistant to malathion. Distinct differences in the bed-bug spectrum suggested that a carboxyesterase was not solely responsible for resistance. This was further supported by the ineffectiveness of triphenylphosphate against malathion-resistance in the bugs.

The F1 progeny from reciprocal mass crosses were tested with malathion. Their response, in both cases, resembled the susceptible type, indicating a recessive autosomal character, a result unique in organophosphorus-resistance. Tests on F2 and backcrosses indicated that a single gene was responsible. Results using fenchlorphos were quite similar and probably the same gene (and mechanism) is involved.

Rearing experiments with Trogoderma granarium Everts were conducted to determine why the larvae fail to develop in certain pulses. The larvae were unable to penetrate whole grains of any of the nine pulses tested. In flour form, the pulses fell into three main groups. On flours of green, black, Bengal and kabuli grams, and cowpea and pigeon pea, development was as successful and rapid, or nearly so, as on wheat flour and showed little improvement from the addition of yeast. Development on flours of soybean and lentil was markedly slower, and showed marked improvement when yeast was added. By adding increased proportions of balanced diet, it was shown that the performance of larvae on soybean, lentil and even on French bean flours could be improved, but with the last two was not as good as with cellulose. It is concluded that lentils and French beans lack essential nutrients and may also contain a growth inhibitor.

A simple procedure for mass-rearing Megaselia scalaris (Lw.) is described, and the suitability of one-day-old adults for bioassay of organophosphorus insecticides is compared with that of Drosophila melanogaster Mg., and Musca domestica nebulo F. by exposure to films of parathion, dichlorvos and malathion. LC50 values of Megaselia scalaris for parathion and malathion, but not for dichlorvos, were of a different order to those of the other two test insects. Males were more susceptible than females to parathion and malathion. Mixed populations would therefore be useful in bioassay of organophosphorus compounds, but greater sensitivity would be achieved by using males.

An account is given of laboratory studies and field observations in Jamaica and British Honduras on the host-plants, life-history and habits of Saccharosydne saccharivora (Westw.), a major pest of sugar-cane. The original host-plants of S. saccharivora are shown to be two species of grasses, Andropogon glomeratus and A. bicornis. The immature stages of S. saccharivora are described and illustrated; the five nymphal instars may most easily be distinguished by their increasing size, the differentiation of the wing buds and the increasing spinosity of the metathoracic tibia and tarsus. Daily records of individuals of S. saccharivora show the duration of the different stages on fertilised plant cane at c. 80°F to be as follows: egg, 15–19 days; instar 1, 6–7 days; instars 2, 3 and 4, each 4–5 days; instar 5, 6–7 days; adult male, about one week; adult female, up to four weeks. The complete life-cycle took 6½–7 weeks, but was slower on unfertilised ratoon cane. In describing the habits of S. saccharivora, particular attention is given to feeding (feeding probes reach the bundle sheath cells and phloem of the lamina), oviposition (young leaves are the preferred oviposition site) and migration (immigration of adults on to young cane occurred at all times of year).

The factors of resistance to many insecticides were located and isolated in a homozygous condition from the diazinon-selected SKA strain of house-flies (Musca domestica L.) by inbreeding each of the five autosomes of the SKA strain into a susceptible multi-marker strain ac;ar;bwb;ocra SRS. The insecticides were: DDT, methoxychlor, tri-butyl tin, the methoxy and ethoxy analogues of parathion, chlorthion and malathion and their corresponding phosphates, diazinon and diazoxon.

The SKA flies' autosomes had the following factors of resistance:—autosome I—very slight resistance to ethyl-chlorthion; autosome II—gene a for low ali-esterase activity which conferred weak to moderate resistance against all organophosphates tested, and Deh (DDT-dehydrochlorinase) which gave great resistance to DDT, but none against methoxychlor; autosome III—Pen, which delayed knock-down by slowing down the entry of insecticides into the flies and had a negligible effect at death except against tri-butyl tin and methoxychlor, and a factor of resistance to Zectran unaffected by sesamex; autosome IV—Dld, the major factor of resistance to dieldrin; and autosome V—Ses, a sesamex-suppressed factor, which gave weak to moderate resistance against ethyl-malaoxon, diazoxon, diazinon, DDT and methoxychlor, but was ineffective against the other organophosphates tested.

TBTP (S,S,S tri-butyl phosphorotrithioate), an ali-esterase inhibitor, greatly synergised organophosphates only against insects with gene a. Pretreatment with sesamex, an inhibitor of microsomal activity, elicited two types of response: antagonism with most of the thioates, most pronounced in flies with gene a, and synergism with the phosphates, especially evident with flies with factor Ses. The possible reasons for differences in the response to organophosphates after pretreatment with TBTP or sesamex, and the nature of the resistance factors are discussed. High resistance in SKA flies against organophosphates arises through the interaction of resistance factors which singly give only weak to moderate resistance.

Investigations into some possible attractants of Glossina morsitans Westw. and G. pallidipes Aust. have been described. In small cages (8x8x11 in.) under laboratory conditions, flies with painted eyes survived longer than those that were untreated, whilst removing the antennae decreased longevity. Olfactory stimuli were probably more important than vision in orientating a fly towards a static guinea-pig used as a host in a moulded mesh insert into the cage. Field observations indicated that tsetse flies were orientated towards an ox at a distance mainly by vision and few flies found oxen concealed by screens. Olfaction may be used at relatively short distances to find hidden host animals, and G. pallidipes may respond to smell more readily than G. morsitans.

Tests in the laboratory and small field cages (6 ft3) indicated that tsetse were not attracted to any particular colour (red, yellow, blue) or shade (white, grey, black). However, in the field more flies were caught off a dark ox than a white ox. In the laboratory > 80% of male G. pallidipes responded to black light within four hours while with G. morsitans a similar proportion was attracted only after six hours. Responses by both species decreased with blue, red and white light and were least with yellow. In small field cages attraction to black light was reduced and only 20–38·6% of either species were caught by a “flap trap” in 6–13½-h test periods. Tests with either blue or red lights in these field cages trapped less than 9% of the released tsetse flies in similar periods. Field trials with black light indicated that this attractant was ineffective as a sampling technique since very few of a natural population were trapped.

In this experimental analysis of the teratology of Tribolium, we studied the effect of crowding and handling on a disorder associated with pupal eclosion. Handling increased the incidence of the abnormality which occurred infrequently in controls: the crowding level tested by us had no effect. T. confusum Duv., strain b-I produced more abnormal beetles than T. castaneum (Hbst.), strain c-IV-a. Handling older pupae increased the disorder to a greater extent than in young and non-pupae.

The handling procedure was quite vigorous and the threshold level required to produce the effect is not known. The phenomenon might be important in population ecology but the pathway through which handling produces it is unknown.

Experiments were carried out on the flight pattern of unfed female mosquitoes in an area of the Gambia adjacent to mangrove swamps. The mosquitoes were trapped in flight by the use of ramp-traps as they approached natural or simulated baits. The traps were arranged in series in four avenues of cleared bush, radiating out at right angles to each other. The baits were installed either at the centre of the cross formed by the avenue or at the outer end of one avenue. Trapping was carried out at six ranges simultaneously, extending from 5–80 yd (4·5–73 m) distance from the bait. The baits were either two small calves or carbon dioxide emitted from a cylinder at a rate equivalent to the expiration rate of the animals. A series of catches with no bait was also made.

The effects of tetramethrin on the behaviour and mortality of Anopheles gambiae Giles entering verandah-trap huts have been studied with the assistance of gaschromatographic techniques.

Fifty-three to 39% of A. gambiae were deterred from entering a corrugated-iron-roof hut treated indoors with a nominal dosage of 2 gm/m2 tetramethrin active ingredient.

Overall mortalities were 53–71% in the first month of application, but fell two to three months after application to 22–46%.

The tetramethrin deposit had marked effects on the behaviour of A. gambiae entering treated huts. Feeding was greatly inhibited, 69–90% of the mosquitoes being unfed. Also, as the residual toxicity of the deposit declined, increasingly higher proportions (40–70%) of recently blood-fed A. gambiae left the huts due to the irritant action of the insecticide. The chemical basis of the irritant effect was indicated to the extent that survivors leaving the treated hut showed 9·5–14·0 ng tetramethrin/individual. The minimum lethal dose was indicated by 17·5–21·7 ng/individual picked up by mosquitoes showing delayed mortalities after leaving the treated huts. Mosquitoes that died indoors picked up amounts ranging from 27·0 to 42·3 ng/individual.

The effects of tetramethrin on A. gambiae were in general similar to those of DDT and pyrethrum, and differed only in degree.

A species of Trichogrammatid reared from the eggs of Entypotrachelus meyeri Kolbe (Col., Curculionidae) is described as new and is named Oligositoides semicinctium.

An Ichneumonid, reared from egg-masses of weevils (Entypotrachelus meyeri Kolbe and E. micans Hust.) harmful to tea culture in Kenya, is placed taxonomically and is described under the name Sozites kerichoensis.

Three egg parasites, Sozites kerichoensis Kerrich (Ichneumonidae), Oligositoides semicinctium De Santis (Trichogrammatidae), and Platystasius benjamini Nixon (Scelionidae) were reared from egg-masses of two closely related Entypotrachelus species indigenous in the tropical rain forest of Kenya. E. meyeri Kolbe occurs west of the Rift Valley, and E. micans Hust. occurs in the foot-hills south and west of Mt. Kenya, east of the Rift Valley. When the forests are cleared, both species transfer from forest trees, weeds and shrubs to newly planted tea and Cinchona spp. where the larvae feed on the roots and the adults feed and oviposit on the leaves.

Grain losses per unit area in oats following shoot attack by frit fly (Oscinella frit (L.)) were assessed in plots at Rothamsted. Individual plants were marked, and two categories of attacked plants (tillers and both main shoot plus tillers attacked) were distinguished because losses in the former were low or negligible compared with those in the latter. There was no evidence of compensatory growth for lost or damaged plants, so that losses could be assessed by comparing actual yield with yield expected had no plants been attacked. The percentage loss, weighted according to incidence and effect of attack in the two categories, was calculated from hand-harvested samples. The loss per unit area was then estimated from the actual yield obtained by combineharvesting. Estimates of actual yield were affected by the method of harvesting, so that estimates of loss were not precise.

A description is given of an artificial stream for studying pupation times and pupal periods of Simulium spp., of emergence traps for studying emergence times in rivers, and of a convenient arrangement for rearing batches of pupae in the laboratory.

S. damnosum Theo., S. kenyae De Meillon and S. unicornutum Pomeroy pupate mainly by day, each species having a characteristic period of peak pupation.

In S. damnosum and S. kenyae the time of pupation influences the pupal period, and for these and other species the pupal period is prolonged by lower temperatures. The pupal period is partly independent of these influences in so far as emergence by night is normally avoided.

The timing of adult eclosion is influenced by the temperature on the day of eclosion. On warm days (midday temperature of the river 24·1–28°C) S. damnosum and other forest zone species show a peak of emergence between 06.00 and 09.00 h, while on cool days (midday temperature of the river 20·1–24°C) the peak is delayed until 09.00 to 12.00 h. On artificially cold days (refrigerator temperature 16–20°C), the peak is shifted to the late afternoon.

The study of the timing of adult eclosion from pupae brought into the laboratory is complicated by the fact that the normal pattern of emergence is liable to disturbance.

In the laboratory a seasonal fluctuation in the sex ratio of emerging flies occurred in S. damnosum.

Descriptions are given of six hypogeic mealybugs forming the genus Geococcus. A key to species and illustrations of five species are included. G. johorensis is described as new from Malaya where it is reported as damaging oil palms. Another new species, G. lawrencei, is described from the Solomon Islands. The history of G. coffeae Green is discussed together with its present distribution.

Individuals of Glossina pallidipes Aust. were reared separately on five developmental categories of guinea-pigs (infants, suckling mothers, pregnant females, mature virgin females, and mature males), from the time of adult emergence until they died, at 22±1°C and 40±5%r.h. More than 70% of the tsetse flies reared on infant guinea-pigs or on suckling mothers died within the first 10 days, before they reached sexual maturity. Of those reared on mature male guinea-pigs, 50% lived for more than 50 days.

Pregnant female and mature male guinea-pigs were the most favoured hosts for tsetse feeding: more than 90% of the flies exposed to these two classes of hosts succeeded in feeding, while only 61%, 70%, and 76%, respectively, of those exposed to infants, suckling mothers, and mature virgin females actually fed.

Anastatus sp. (Eupelmidae) is recorded for the first time parasitising a puparium of Glossina palpalis (R.-D.) in West Africa. Hitherto, the only records of Eupelmids parasitising tsetse flies have been of A. viridiceps Wtstn. and Eupelmella tarsata (Wtstn.) from G. morsitans Westw. in eastern and southern Africa. The parasite emerged through a large hole anterior to the polypneustic lobes. Parasitic Eupelmids do not normally utilise tsetse flies as hosts.

A laboratory technique is described which enables large numbers of Simulium larvae from field sources to be established in a narrow 12-in. long experimental channel in the laboratory where they can be maintained in a continuous flow of water. The apparatus was primarily designed for a critical study of the reactions of larvae exposed to various time/concentrations of larvicides and other chemicals. By exposing dense aggregations of many hundred larvae at a time, significant figures can be obtained regarding the number of larvae detached at various intervals during and after exposure to larvicide, and also regarding the subsequent survival or mortality of the different detached fractions.

Natality is more important than mortality in the determination of the number of first-generation adults of Scolytus scolytus (F.) to emerge. The reverse is the case for the overwintering generation. Temperature is a probable key factor for the first generation, and subcortical predators for the overwintering generation. These results are related to possible control of the beetle as a vector of Dutch elm disease by injection of systemic insecticides. It is suggested that control measures may only be necessary in the climatic conditions of the United Kingdom in hot summers when a large first generation is likely to emerge. Natural mortality factors will effectively reduce the beetle population that overwinters.

Examination of infested bean plants (Phaseolus vulgaris) showed that “bean fly” in East Africa consists of three species, Melanagromyza phaseoli (Tryon), M. spencerella sp. n. and Ophiomyia centrosematis (de Meij.). M. spencerella is described, and notes are given on the life-cycle, host-plants and distribution for all three species. Their importance in East Africa is discussed and it is concluded that M. spencerella is the most damaging because it oviposits and feeds in the hypocotyl, is frequently the most abundant species and is less effectively parasitised. Bean plants able to produce adventitious roots freely are able to grow away from the important early attack in the stems. Published work on chemical control measures is summarised.

The parasite complex associated with bean fly in East Africa was studied, and notes are given on the species present, the recognition of their early stages, their host ranges and abundance. Parasitism is discussed in relation to the infestations found on beans, with special reference to Opius melanagromyzae Fisch., the most important parasite of M. phaseoli, and Eucoilidea sp., the most important parasite of M. spencerella. It is concluded from graphical analysis that O. melanagromyzae is density-dependent and an important factor in limiting M. phaseoli populations in East Africa. Eucoilidea sp., on the other hand, shows signs of delayed density-dependence and is less effective in controlling its principal host. O. melanagromyzae has recently been sent to Hawaii for release against M. phaseoli; some field recoveries have been made already.