Field observations indicated that a strain of Boophilus microplus (Can.) in the Rockhampton area in Queensland was resistant to an organophosphorus insecticide, dioxathion (applied as Delnav), which had previously controlled it successfully. Ticks of this strain were despatched to the Cooper Technical Bureau in England, where a culture was established and maintained under selective pressure from dioxathion.

The non-parasitic stages of the culture were maintained in an incubator under controlled conditions, and the parasitic stages on cattle in a tick rearing house designed for the purpose. Careful security precautions were taken to ensure that there was no dissemination of tick life outside the confines of the culture. The tick rearing house was provided with double doors, the inner ones of which were screened with copper gauze to prevent the possible transmission of anaplasmosis by biting flies.

The activities of 23 insecticides against larvae of this strain and larvae of a strain of B. microplus susceptible to organophosphorus poisoning were compared. The test method was an immersion technique, usually employing the insecticide in the form of an emulsion. Mortality was assessed 17 hours after treatment. These comparisons indicated that the strain was resistant to the organophosphorus insecticides carbophenothion (62 ×), dioxathion (25 ×), diazinon (15 ×), parathion (10×) and a carbamate, carbaryl (38×). It is suggested that these resistances may be due to a specific mechanism effective against these compounds.

Nine other organophosphorus insecticides, one carbamate and rotenone were subject to low-order resistance by this strain significant at P ≤0·05. This was considered to be non-specific resistance.

Dioxathion had been in use for tick control on the property concerned for four years before resistance was demonstrated. The property is situated in an area where the tick season lasts for ten months. In other parts of the world, dioxathion has been in use against Boophilus ticks for seven years without the development of resistance to it. The length of time resistance has taken to develop suggests that the resistance mechanism is not the expression of a single dominant gene, as has been demonstrated for dieldrin-resistance.

The results suggest that resistance to one or more organophosphorus insecticides will not necessarily prevent the use of other members of this wide and diverse group for tick control. Several of the insecticides shown here to be subject to low-order non-specific resistance are known to be effective tick dips, and one of them, ethion, has been used with success against the resistant strain.

An interesting corollary of the results was that the organophosphorus thions showed greater activity than their corresponding oxons against the susceptible strain.

An account is given of the disappearance in Kaduna, Northern Nigeria, of Culex nebulosus Theo. from the town streams and drains and other polluted collections of water, habitats in which until comparatively recently it appears to have been the dominant species, and its replacement by C. pipiens fatigans Wied., which was formerly rarely recorded in these sites. Similarly, the latter species has replaced the former as the commonest Culicine mosquito resting in houses. Increased urbanisation and the widespread use of residual organo-chlorine insecticides within recent years have both been advanced as possible explanations for this change.

A laboratory experiment with larvae of C. p. fatigans from Kaduna and of C. nebulosus from villages on its perimeter showed the latter species to have a slightly, but significantly, quicker rate of larval development than C. p. fatigans; this would possibly confer an advantage on it in circumstances where the two species are in competition for the same larval habitats. Field and laboratory observations showed that both species can tolerate high organic pollution in their larval habitats. There appeared to be little evidence in Kaduna, or in other towns in Nigeria, to support the theory that urbanisation has been responsible for the replacement of C. nebulosus by C. p. fatigans. Laboratory and field trials demonstrated that larvae of C. nebulosus were extremely sensitive to DDT, and although resistance was not found in C. p. fatigans, this species showed tolerance of the insecticide. It is believed that, in Kaduna and most probably in other towns, the application of DDT as a larvicide to streams and drains has been responsible for the eradication of C. nebulosus there, and in the absence of competition from C. nebulosus and because of the greater tolerance of DDT shown by C. p. fatigans the latter has been able to establish itself as the dominant species.

Many crops in southern Tanganyika are attacked by termites, especially those grown in the miombo woodland (Brachystegia-Pseudoberlinia), which covers much of the southern and western parts of the country. The termites chiefly concerned are Microtermes albopartitus (Sjöst.), M. redenianus (Sjöst.), Ancistrotermes latinotus (Hlmgr.) and Allodontermes tenax (Silv.). A pit dug to investigate their nest systems showed that M. albopartitus was the most numerous, 425 occupied cells being recovered from an area 50 × 24 ft. excavated to a depth of 6 ft. Cells of the other species included 166 of M. redenianus, 54 of Ancistrotermes latinotus and 49 of Allodontermes tenax. The cells of Ancistrotermes latinotus were aggregated into small clusters connected by long runways; those of the other species were more or less randomly scattered. The greatest concentration of cells of all species was within the top 2 ft. of the soil, but a number of cells were found at greater depths and it is certain that 6 ft. is not the maximum nesting depth. Descriptions of the nest systems and fungus combs are given.

Observations at Nachingwea in 1959–63 showed that loss of maize stands from termite attack averaged 27 per cent, over the five years, and that of soya 33 per cent. The damage was often great on individual plots, as much as 90 per cent, being recorded from one plot of maize. Plant-population counts over three growing seasons showed that maize is lost mainly towards the end of the season, whereas soya may be attacked any time after planting, increased losses occurring during dry spells and at the end of the season.

Control was achieved by the use of aldrin or dieldrin applied as dusts to the soil before planting or used in seed dressings. It was found in a series of field trials that good control of termites was afforded by aldrin worked into the soil along the planting ridges at a rate of 1 lb. active ingredient per acre, but that in practice ½ lb. per acre gave nearly as good results when measured by yields. In spite of the considerable losses, it was considered uneconomic to use aldrin to protect soya from termite attack, but the increased yields of 200–400 lb. maize per acre justified the expenditure on insecticide. The aldrin dust protected both crops for at least one further year after application, the effects on yield being of the same order as before.

A seed dressing of 75 per cent, dieldrin gave excellent control and was considerably cheaper than soil application of aldrin. The cost was only a few shillings an acre when the dressing was used at the rate of 0·1 oz. per 1 lb. seed, and the effect was to raise yields of maize by 330–500 lb. and of soya by 110–180 lb. per acre.

Trenches were dug to investigate the effects of soil treatment with aldrin on the nest systems of the termites. There was little effect on cell density eight months after application, but after 20 months there were signs of a reduction, especially in the top 9 in. of the soil.

Details are given of a trap for Phlebotomine sandflies attracted to a small mammal placed in a cage incorporated in the trap. It was developed in British Honduras for the purpose of studying the sandflies attracted to proven or possible hosts of Leishmania, other than man. The results of initial tests carried out at Central Farm from November 1964 to February 1965 are reported. These provided evidence that the sandflies caught in the trap were attracted to the rodents used as bait, and did not enter by chance; unbaited traps caught virtually no flies. In traps baited with rodents known to be reservoir-hosts of Leishmania, the species caught in greatest numbers was Phlebotomus apicalis Floch & Abonnenc, and amongst those caught in smaller numbers were P. cruciatus Coq. (including P. diabolicus Hall) and P. deleoni Fairchild & Hertig; it is suggested that all three are possible vectors of leishmaniasis in British Honduras. The relative numbers of the sandfly species caught in the traps were very different from those caught on man in British Honduras and by direct catching on animals in Panama.

Taxonomic characters of the adult, pupa and larva of the coconut flat moth, Agonoxena argaula Meyr., are compared with those of the three other known species comprising the family Agonoxenidae, and keys to the species are provided. One new species, A. phoenicia, is described from northern Queensland. The systematic position of the family and the generic status of the four species are discussed. Although differences of possible taxonomic importance have been noted, the species are considered sufficiently homogeneous to allow assignment to the single genus Agonoxena Meyr. Haemolytis miniana Meyr. is transferred to Agonoxena, and Haemolytis Meyr. is suppressed as a junior synonym.

Sticky traps were operated over sugar-beet crops at Rothamsted Experimental Station (Hertfordshire), Broom's Barn Experimental Station (Suffolk) and elsewhere for five years to gain information about the flight of the aphids that transmit beet yellowing viruses and to aid in the spray warning scheme for sugar-beet growers.

Numbers of Myzus persicae (Sulz.), Aphis fabae Scop, and of all aphids caught per week are given. Records of aphids trapped at Rothamsted over a period of 23 years have been published; but no repeating pattern of aphid abundance from year to year has been detected. M. persicae flew early in 1960 and 1961, when beet viruses spread extensively, whereas in 1962, 1963 and 1964, when alates of this species did not fly early but were trapped in relatively larger numbers later in the year, yellows spread much less. Large numbers of A. fabae flew in 1963, but beet viruses spread little.

In 1960–63, fifteen field trials were carried out on tea estates in Ceylon to find whether dieldrin at 1–5 or 3 Ib. per acre applied as a spray to the tea bushes immediately after pruning would afford control of the shot-hole borer, Xyleborus fornicatus Eichh. Koutine sampling by a method that is described was carried out for three years after spraying, and fluctuations in the numbers of live stages and galleries of the Scolytid were recorded.

In unsprayed plots, the beetle population left in the old wood of the tea bushes after pruning at first declined, but began to rise about nine months later. Sampling was then continued in the new wood that grew after pruning. In this, the numbers of galleries and live stages increased to a major peak late in the second or early in the third year and then declined; there was a smaller increase later in the third year in several of the trials. By comparison, dieldrin at 1·5 lb. per acre greatly delayed the build-up of attack and effected an average reduction in gallery numbers of 81 per cent, by the eighteenth month and 70 per cent, by the twenty-fourth month. The main peak of attack was delayed until the early part of the third year, and the maximum level averaged only about half of that on unsprayed plots; but control in the third year was less satisfactory and more variable than in the second year. Spraying with dieldrin at 3 lb. per acre did not give better control, and no difference in effectiveness was found between 1·5 lb. applied as a high-volume (90 gal. per acre) and a low-volume (8 gal.) spray.

Special sampling in two trials revealed that reinfestation of sprayed plots began at edges adjacent to infested unsprayed plots and continued progressively inwards. It is concluded that the duration of control from spraying will be influenced by the size of the area sprayed and the proximity of infested tea fields, and that on estates, where fields of 20–40 acres would be sprayed, the level of control will be at least as good as that observed in the trial plots of 5–10 acres.

The main drawback to the use of dieldrin is that it induces outbreaks of tea tortrix, Homona coffearia (Nietn.), by killing off the parasite Macrocentrus homonae Nixon. The possible use of less persistent insecticides is discussed, together with the timing of chemical control measures in relation to cultural practices.

The numbers of open galleries (entrances visible) were closely correlated with those of live stages of the beetle up to the time of peak attack and less closely afterwards, probably because the entrance holes healed up at varying rates. The proportion of immature stages (eggs, larvae and pupae) in the population fell from the first to the third year; the fall was most rapid in unsprayed plots after the second-year peak of attack. One-tenth of adult beetles counted were males, but the true proportion in the broods was estimated to be between one-third and one-fifth. The frequency distribution of gallery numbers showed that invasion of new wood starts at random and becomes increasingly over-dispersed (more uniform) as the density rises. This would be expected if there is a maximum density of galleries that is much the same in all the tea bushes. There was some evidence for a density-dependent regulation of borer numbers brought about by intra-specific competition for wood suited to gallery formation and brood-rearing. Other possible factors influencing density are discussed.

The four commonest species of Sitona injuring leguminous crops in Israel were found during a survey in 1957–62 to be S. lividipes Fhs., S. hispidulus (F.), S. crinitus (Hbst.) and S. lineatus (L.). Adults of all four were collected in the field in December-January each year, at the termination of diapause, and kept in the laboratory for observations on their bionomics. Larvae and pupae did not survive in the laboratory, and therefore these stages were reared in the soil outside (where suitable food-plants had been grown) from eggs laid by the adults in the laboratory and kept at known temperatures until they were about to hatch. The soil was later examined daily for pupae.

Egg-laying began in December, larvae were found in January–March, pupae in March–April, and adults of the new generation in April–May. These adults fed freely but did not oviposit, and in June–July they sought shelter and entered diapause, which lasted until the close of the year. Feeding was then resumed, oviposition began shortly afterwards, and death occurred up to 250–300 days later.

The eggs of all four species are creamy or yellowish white when laid but soon become glistening black. High humidity was necessary for hatching; no eggs of S. lividipes or S. hispidulus hatched at relative humidities of 76 per cent., or less, and virtually none of S. crinitus or S. lineatus at 56 per cent, or less. In favourable humidities, the percentage hatching was reduced at constant temperatures exceeding 25°C., except in S. lineatus, in which it was not affected up to 29°C. The threshold temperatures for development of eggs of S. lividipes, S. hispidulus, S. crinitus and S. lineatus were 4·8, 4·6, 5·8 and 6·5°C., respectively, and the thermal constants were 180, 211, 166 and 145 day-degrees C. The mean larval and (in brackets) pupal periods outdoors were 52 (23), 58 (34), 36 (25) and 38 (21) days, respectively. The average numbers of eggs laid were 843, 719, 519 and 1,113 per female, and the mean numbers laid per day were 10·2, 8·5, 9·6 and 17·5. These data were obtained by feeding adults on a variety of food-plants throughout their life in the laboratory. In another series of observations, adults were fed on the same type of food-plant throughout. Egg production of S. lividipes and S. hispidulus was greatest on clover (Trifolium alexandrinum) and least on broad bean (Vicia faba) and pea, respectively; that of S. crinitus and S. lineatus was greatest on pea and least on broad bean and clover, respectively.

The taxonomy of African species of Antestiopsis, some of which are important pests of coffee, has hitherto been in confusion owing to the difficulty of finding decisive morphological characters. In the present study an attempt is made to clarify the relationships of the coffee pest species and some of their close allies by the use of both biological and morphological characters.

The species of Antestia and Antestiopsis occurring on coffee in Africa are differentiated in a key, and descriptions are given of the following: Antestiopsis orbitalis (Westw.), with three clearly distinguishable subspecies, orbitalis, bech-uana (Kirkaldy) and ghesquierei Carayon, several local colour forms of these, and a few variable populations that cannot be referred definitely to any one of the subspecies; A. intricata (Ghesq. & Carayon); A. facetoides sp.n. for the species hitherto known as “ faceta ” in eastern Kenya and Tanzania; A. crypta, sp.n. confined to Katanga; A. falsa (Schout.), a rare and imperfectly known species; A. lepelleyi sp.n., which does not feed on coffee; and A. littoralis sp.n., from the Kenya coast, known to the writer only from museum specimens.

Evidence for the arrangement adopted is discussed, and the taxonomic value of certain morphological characters is assessed. The distributions presented on maps are discussed, and it is concluded that the activities of man are unlikely to have obscured the natural patterns. A list is given of known host-plants, which, except for those of A. orbitalis orbitalis and form facetus, are with only a single other exception members of the Eubiaceae. The distribution on a local scale and recent changes of abundance of species in competition are discussed, and it is shown that A. orbitalis ghesquierei and A. o. bechuana appear to be spreading at the expense of A. intricata in Uganda and A. facetoides in Tanzania, respectively. Kesults of crossing East African species and forms show that those here regarded as species will not cross but that the subspecies of A. orbitalis will do so, producing intermediates that, when allowed to interbreed, are not as viable as pure strains. Finally an attempt to find morphometrical characters is discussed, and the results are given of a calculation of discriminant functions based on two characters. These, while, not conclusive, support the conclusions drawn from other evidence.

When fasting fifth-instar larvae of Rhodnius prolixus Stål were poisoned with a lethal dose of DDT, the rate of oxygen consumption increased from the onset of hyperactivity, reached a marked peak shortly after knockdown, and then declined. For some days after the peak the oxygen consumption was markedly in excess of that prior to poisoning with DDT. Eventually, the oxygen consumption fell below the pre-teatment value and continued at this low level for some days, although the insect was then undoubtedly dead and in one case had been bisected. There was no marked discontinuity in the declining phase of oxygen consumption and therefore there is no indication of when death occurred. It is concluded that the time of death in DDT-poisoned larvae of Rhodnius cannot be determined by measurements of oxygen consumption.

The total oxygen consumed from poisoning until death was always less than that consumed in the normal use of all metabolic reserves by the fasting insect, and these experiments do not support the hypothesis that death in DDT poisoning is due to total exhaustion of metabolic reserves. However, it is pointed out that, in Rhodnius, some of the metabolic reserves are contained in the undigested residue of the blood-meal and in the massive endocuticle and that there is no reason to think that either digestion of the remaining blood-meal or resorption of the endocuticle could be speeded up during DDT poisoning. Hence there is a strong possibility that, in DDT-killed Rhodnius, death is brought about by exhaustion of the available reserves.

The peak rate of oxygen consumption during poisoning was greatest in very recently fed larvae and decreased as the interval between moulting and DDT-treatment was increased. This suggests that knockdown occurs when the fuel demands of the DDT-induced activity exceed the rate at which the fuel can be mobilised from the metabolic reserves.

It had been noticed in earlier work that there was a lack of close relationship between the intrinsic and contact toxicities of various compounds to adults of Anopheles stephensi List., the intrinsic toxicities being determined by topical application of solutions and the contact toxicities by exposure to dry deposits. Since the reasons probably lay in the relative rates at which compounds penetrated the cuticle from solution and from the solid state, and since these rates are likely to be differently affected by the physical properties of the compounds, the intrinsic and contact toxicities to A. stephensi of some closely related carbamates and of a miscellaneous group of organophosphorus compounds were determined, together with the solubility in n-hexane and the partition coefficient between n-hexane and water of each, and the results were compared.

No definite pattern in the relationship between these physical properties of the compounds and their intrinsic and contact toxicities emerged from consideration of the results. However, there were indications that very low solubility is a limiting factor in the uptake and penetration into mosquitos of a solid insecticide and is associated with low contact toxicity, and that, when solubility is high enough to ensure solution in the wax layer of the cuticle, contact activity is favoured by a low value for the partition coefficient between hexane and water.

Larvae of Pieris brassicae (L.) were reared very successfully on a semi-synthetic diet containing a small amount (1·4% by wt.) of dried powdered green Brassica leaves. At 20°C., development of newly hatched larvae to the time when 50 per cent, had pupated took an average of 23 days, as compared with 21 days for larvae fed on fresh cabbage leaves. Pupal weights and emergence of adults were normal. The cabbage-leaf powder could be omitted if it was replaced by sinigrin and linseed oil, but on this diet development was prolonged by a further one or two days and the average pupal weights were lower. It seems likely that the stocks could be maintained indefinitely on either of these diets. The larvae made satisfactory growth on standard diet which had been stored at – 20°C. for two months.