The apparatus previously used to demonstrate the repellent properties of DDT, fuel oil and methylated naphthalene auxiliary solvents towards certain Diptera was used in further studies of olfactory repellency in an attempt to narrow down the ingredients responsible for this effect, and consideration was given to the possibility of finding substitutes for them with less repellent or even attractive properties.

Light, medium and heavy fractions were obtained by fractional distillation of fuel oil and each of two methylated naphthalene auxiliary solvents. In all these spray components the repellent properties are inversely related to the boiling point, and appear to be non-specific both chemically and by insects. Tests with materials of low volatility, however, showed that the effect is not a simple broad relationship between volatility and repellency.

Butoxy-polypropylene glycol, widely used as a ‘repellent’ ingredient of livestock sprays, shows olfactory attractiveness to Musca domestica L. and Aëdes aegypti (L.). The odour of Drosophila melanogaster Mg. was shown to be attractive to the insect, regardless of sex.

It is concluded that there seems little hope of an economic non-repellent material.

It is suggested that the repellency of spray components might be counteracted by the addition of specific attractants, sex or other, to spray formulae. Alternatively, a useful space repellent spray, containing no toxicant, might be formulated from the lighter fractions of the solvent materials.

Previous records and new data on infection rates in species of Glossina inhabiting southern Nigeria and the Southern Cameroons are presented, and the probable economic importance of each species is assessed.

The trypanosome infection rates were highest in those species of tsetse which fed largely on Bovidae.

The rarity of human trypanosomiasis in southern Nigeria and the Southern Cameroons is attributed largely to impersonal man/fly contact; under such conditions a low proportion of infected flies is to be expected. G. palpalis (R.-D.) is not an important vector of sleeping sickness, as it is in northern Nigeria. The incidence of infection in G. palpalis was generally very low; cases of bovine trypanosomiasis do occur in areas where G. palpalis is the only tsetse species present, but it is not considered to be an important vector.

Little information is available on G. tachinoides Westw. and G. caliginea Aust. in southern Nigeria; both have probably been at least partly responsible for some of the rare outbreaks of sleeping sickness reported from the south. G. tachinoides may be of some significance as a vector of animal trypanosomiasis.

The infection rate in G. longipalpis Wied. at the West African Institute for Trypanosomiasis Research Field Station at Ugbobigha was 21·5 per cent.; this species is believed to be of major economic importance because its presence must prevent the keeping of cattle in large areas of potential grazing.

At least 13 per cent, of examples of G. medicorum Aust., G. fusca (Wlk.) and G. nigrofusca Newst. were infected in the populations examined, and the first two species are considered to be of economic importance because they penetrate potential grazing areas.

G. pallicera Big., G. tabaniformis Westw. and G. haningtoni Newst. are confined to rain-forest and were found to be lightly infected; they are therefore not considered to be of economic importance, except possibly as a source of infection to cattle on trade routes.

No data are available for G. nashi Potts.

A detailed tsetse-fly survey of 41,000 sq. miles in the inland savannah zone of the Gold Coast (Ghana) was completed in five years using an entirely African staff and working only six months each year.

This undertaking was made possible because studies of the species of Glossina concerned, G. palpalis (R.-D.), G. tachinoides Westw. and G. morsitans sub-morsitans Newst., had provided knowledge of their habitat, food-hosts and activity rhythm, on which could be based a standard yet simple survey technique, within the compass of independent native teams.

The restricted activity rhythm of the flies, subject to both daily and seasonal variations, meant that nothing less than a ‘day’ of eight hours of observation could be accepted as a valid sampling unit.

With tsetse flies at low densities, a day's search was inadequate, giving only 40 per cent, reliability compared with 6-day observations. Four days' search gave 90 per cent, reliability and was adopted as the minimum period of search.

Each survey team was under the charge of a Kecorder or Field Assistant, with fly-boys devoting the whole of their time to catching. Comparability of survey data was ensured by keeping teams to the same size, two fly-boys being the optimum, since it was found that the size of the catch was not always proportionate to the number of boys, the relationship varying according to a variety of factors.

In surveying G. palpalis and G. tachinoides the ‘picket’ system of more or less stationary teams, measuring their catches by the ‘day ’, was found overwhelmingly superior to the ‘fly-round’ technique.

The survey procedure described for savannah woodland country was not effective in sampling G. nigrofusca Newst. in the Ashanti forest or G. longipalpis Wied. in the coastal savannah, but Morris's ‘animal’ traps were found to take both species readily in places where they had not been detected or only occasionally caught by fly-boys. Experiments showed that trap catches were superior, both numerically and in giving a more representative sample of the tsetse population present. It was also shown that trapping could be a valuable means of studying the biology of these two ‘man-shy’ species of Glossina. Traps were also effective in taking G. pallicera Big. and G. medicorum Aust.

The greater value of traps compared with fly-boys as a means of sampling various species of tsetse fly is discussed, and suggestions are put forward for developing trapping as a method of survey.

The type of trap employed is regularly catching insects of several other families, including a number of species among the Tabanidae, and of several other orders.

An account is given of a study of infestation of cowpea pods in the field in Northern Nigeria by the weevil, Piezotrachelus varius (Wagn.), and the Bruchids, Bruchidius atrolineatus (Pic) and Callosobruchus maculatus (F.). Oviposition by Bruchids did not commence until the pods were fully formed and light green in colour, whilst infestation by P. varius originated in the young pods. Observations indicated that a high level of parasitism of Bruchid eggs occurred, but that the majority of Hymenopterous parasites emerging from within the pods were related to P. varius.

When pods were harvested at regular intervals, large numbers of P. varius emerged from the early harvests only. B. atrolineatus was the predominant Bruchid species emerging, particularly from early harvests. In the case of a single final harvest of pods, large numbers of P. varius, and a higher level of infestation by B. atrolineatus than in pods collected at regular intervals, were recorded.

Shelling of four batches of pods indicated a mean of 11 per cent, of seeds attacked by Bruchids in the case of single final harvests, and a mean of only 3·5 per cent, in the case of regular harvests as pods became dry. It is concluded that a considerable improvement in quality would result from an adoption of the latter method by farmers, provided that some method of control in respect of the harvested pods were introduced.

From the observations made it is concluded that P. varius is a true field pest, B. atrolineatus primarily a field pest able to continue infestation in store to a very limited extent, and C. maculatus primarily a store pest able to commence its infestation in pods in the field and to build up in numbers rapidly during the immediate post-harvest storage period.

The normal manner of cultivation precludes the use of field methods of control at oviposition peaks but observations suggest that elimination of secondary hosts of P. varius and B. atrolineatus might be worthwhile. A reduction in oviposition by C. maculatus by treatment of stored cowpeas in growing areas, and treatment of pods during the immediate post-harvest storage period, should considerably reduce the level of infestation by this species.

A detailed tsetse-fly survey of 41,000 sq. miles in the inland savannah zone of the Gold Coast (Ghana) was completed in five years using an entirely African staff and working only six months each year.

This undertaking was made possible because studies of the species of Glossina concerned, G. palpalis (R.-D.), G. tachinoides Westw. and G. morsitans sub-morsitans Newst., had provided knowledge of their habitat, food-hosts and activity rhythm, on which could be based a standard yet simple survey technique, within the compass of independent native teams.

The restricted activity rhythm of the flies, subject to both daily and seasonal variations, meant that nothing less than a ‘day’ of eight hours of observation could be accepted as a valid sampling unit.

With tsetse flies at low densities, a day's search was inadequate, giving only 40 per cent, reliability compared with 6-day observations. Four days' search gave 90 per cent, reliability and was adopted as the minimum period of search.

Each survey team was under the charge of a Kecorder or Field Assistant, with fly-boys devoting the whole of their time to catching. Comparability of survey data was ensured by keeping teams to the same size, two fly-boys being the optimum, since it was found that the size of the catch was not always proportionate to the number of boys, the relationship varying according to a variety of factors.

In surveying G. palpalis and G. tachinoides the ‘picket’ system of more or less stationary teams, measuring their catches by the ‘day ’, was found overwhelmingly superior to the ‘fly-round’ technique.

The survey procedure described for savannah woodland country was not effective in sampling G. nigrofusca Newst. in the Ashanti forest or G. longipalpis Wied. in the coastal savannah, but Morris's ‘animal’ traps were found to take both species readily in places where they had not been detected or only occasionally caught by fly-boys. Experiments showed that trap catches were superior, both numerically and in giving a more representative sample of the tsetse population present. It was also shown that trapping could be a valuable means of studying the biology of these two ‘man-shy’ species of Glossina. Traps were also effective in taking G. pallicera Big. and G. medicorum Aust.

The greater value of traps compared with fly-boys as a means of sampling various species of tsetse fly is discussed, and suggestions are put forward for developing trapping as a method of survey.

The type of trap employed is regularly catching insects of several other families, including a number of species among the Tabanidae, and of several other orders.

In plot trials with seed dressings on late-sown oats against shoot attack by frit fly, Oscinella frit (L.), chiefly near Cambridge, England, γ BHC, parathion, dieldrin, heptachlor, Rogor and WL 1650 (Telodrin) (1,3,4,5,6,7,8,8-octachloro-3a,4,7,7a-tetrahydro-4,7-niethanophthalan) (dry and wet) reduced the attack but the effect was variable and for the most part not appreciable.

In 1952 and from 1956 to 1960, trials were made on the effect of late sprays of various insecticides applied to late-sown oats when symptoms of frit-fly attack were already conspicuous and sometimes severe. An advantage of this type of treatment over preventive sprays is that it ensures that the treatment is applied only where and when necessary. Single sprays of parathion, dieldrin, γ BHC and Rogor prevented or markedly reduced further attack and they were most effective when applied within about 15 days of the beginning of egg-laying and when plants were in the young seedling stage. Compared with the best treatment of two early preventive sprays of DDT there was only a slight reduction in yield. Parathion and to lesser extent γ BHC killed many larvae inside the shoots and probably prevented others from entering the shoots.

Experiments were conducted with Trinidad strains of Oryzaephilus surinamensis (L.) and O. mercator (Fauv.), the average sizes of which were smaller than those given in the literature. Limited observations on their biology on cereal products showed that whereas the egg-production of O. mercator was comparable with that recorded by other workers under similar conditions, that of O. surinamensis was much lower.

Larvae of both species were able to complete their development on raw and yellow-crystal sugar, but there was a high mortality among those of O. surinamensis. Both species showed very low oviposition rates on sugar and this, together with a high larval mortality, would indicate that infestations of O. surinamensis on these products would die out. O. mercator, on the other hand, could multiply very slowly. Oviposition rates rise rapidly when females return from sugar to cereal products.

Unrefined sugars should accordingly not be disregarded as sources of Oryzaephilus infestation, especially in the humid tropics.

The daily distribution of G. pallidipes Aust. was studied on a spiral fly-round covering 180 acres in the South Busoga forest of Uganda in 1954–55. G. brevipalpis Newst. also occurred in the forest, and, rarely, G. palpalis fuscipes Newst. Seasonal changes occur in the size of G. pallidipes, but are less marked than those reported from other places. The size of G. brevipalpis also varies with season. Seasonal colour changes in G. pallidipes indicate that in the driest season about half the puparia experience relative humidity as low as 70 per cent.

Catching was done at 349 (later increased to 373) points on the spiral. Mathematically, the catches on a single day, or the sum of many days, conformed to a negative binomial distribution. Although this indicates an uneven distribution, it is pointed out that one negative binomial is compatible with many different distributions on the ground. For this reason the negative binomial is not a satisfactory summary of data which at present can only be shown satisfactorily on a map.

Comparison of maps of catches on successive days shows a confusing pattern of vague and ill-defined patches of flies moving about in an unpredictable fashion. A definitive pattern appears only when many days' catches are summed. Such apparently random movement explains the high variance between days' catches previously reported. Sometimes very large numbers of G. pallidipes were found in a small area. As an index of such concentrations, the smallest area which could contain half the day's total catch was determined. Arbitrarily, when half the day's total catch was found in 5 per cent, or less of the total area, a concentration was said to exist. During 16 months' work, concentrations of tsetse, as defined by this criterion, were observed 16 times. Sometimes, but not always, the concentrations followed immediately after the passage of a herd of elephants or buffaloes, and it is concluded that these animals probably caused these concentrations, although the manner in which they may do so remains obscure.

A dieldrin emulsion spray containing 3 per cent, dieldrin (w/v) was applied once to the putative resting places of Glossina morsitans Westw. throughout a comparatively isolated 17-sq.-mile fly-belt in the Kabiganda Valley in southwestern Uganda between October 1957 and September 1958. Concentration areas of the fly consisted of one or more tall trees with associated understorey and thicket. The lower sides of the branches of an average of 6·75 such trees per acre were treated at a rate of about one-fifth of a pound of dieldrin per acre and at a cost of about £250 per sq. mile.

Chemical analysis showed a deposit of approximately 0·8g. dieldrin per sq. metre on the surface sprayed, and although 90 per cent, of this had disappeared from the surface after about four months, it is thought that the application remains effective for this period.

A very great reduction in the tsetse population was achieved. Small numbers of flies continued to be caught, but it was thought possible that these were being brought in from neighbouring valleys by buffalo, and, hence, that insecticidal application of this sort, if carried out over a wide enough area, might eradicate a tsetse population.

The distribution of cholinesterases hydrolysing acetyl- and butyrylthiocholine in the brain and thoracic ganglion of Musca domestica L. was examined histochemically in untreated flies, and in flies poisoned with diazinon (O,O-diethyl 0–2–isopropyl–4–methyl–6–pyrimidinyl phosphorothioate) of both susceptible and resistant strains.

The inhibition of cholinesterase after poisoning was, to a greater or lesser extent, confined to the peripheral region of the ganglia, and to other specific areas such as the suboesophageal ganglion and lamina ganglionaris. The extent of inhibition increased with increasing doses of poison, and increasing time after treatment. The degree of inhibition could be broadly correlated with the condition of the fly; badly affected or moribund flies having less active cholinesterase than living and unaffected flies. Together with these areas of more or less complete inhibition were other areas, especially in the neuropile or synaptic regions, in which there remained large amounts of active enzyme. Active enzyme was still present in these areas 24 hours after apparent death of the fly. Total inhibition of cholinesterase throughout the central nervous system was rarely seen, even after very high doses of diazinon causing over 99 per cent. kill.

Inhibition did not occur in the ganglia of living flies of a diazinon-resistant strain after a dose which caused inhibition and death in the normal susceptible strain. With 25 times this dose, causing approximately 99 per cent, kill in the resistant flies, cholinesterase was inhibited in them also, although to a somewhat lesser extent than in the susceptible flies given a comparable lethal dose.

The data provided strong evidence that if death is caused by inhibition of cholinesterase of the nervous system it is due to local inhibition and not to generalised inhibition.

Coconut poonac, the cake left over after the extraction of oil from coconut pulp, has been used very successfully for breeding Musca d. vicina Macq. in the laboratory in Ceylon. The fly lays its eggs in the poonac and the larvae live and pupate in the same medium.

The observation in Kenya that Aëdes (Skusea) pembaensis (Theo.) associates with the crab, Sesarma meinerti, was duplicated in Lumbo, on the northern coast of Mozambique. Eggs were seen abundantly on crabs inhabiting certain colonies among mangroves at the edge of a tidal estuary. Females of A. pembaensis were caught in gradually decreasing abundance at collecting sites progressively further inland from the head of the estuary, while males were almost totally confined to the breeding area. Swarms of males were not seen, and it was suspected that mating took place within crab burrows.

Populations of A. pembaensis in 1959 and 1960 were approximately equivalent at Lumbo, whereas some other mosquito species with fresh-water larval stages were reduced in 1960 owing to failure of the rains. The estuarine environment, regulated by the tides, is apparently more stable than are terrestrial habitats. Cycles of A. pembaensis may therefore be less variable than among dry-land forms.

Females of A. pembaensis disturbed at a crab colony were found to bite spontaneously in the day-time. Captured specimens showed a marked discrimination in biting preference for one human out of three tested. The preferred individual experienced a severe reaction to the bites, while the other two had none whatsoever.

Precipitin tests indicated human beings as the only source of blood in A. pembaensis, although the method of collection probably lends bias to this observation. Eight strains of an apparently new virus were isolated from females of A. pembaensis in 1959 and four in 1960. In addition, two strains of a virus of the Bunyamwera group were isolated in 1960. The source of these viruses and their significance in A. pembaensis require further investigation.

The rearing of a complete generation of Mansonia (Coquillettidia) aurites (Theo.) is described with notes on the methods used.

Variation in the leg ornamentation of the adults forming the progeny of a single egg-raft was found to cover the range usually observed in this species.

A plea is made for conformity in the use of terms describing the various kinds of aggregations of eggs.

Egg-rafts are discussed, and a tentative key is given to the eggs of six of the Ethiopian species of Coquillettidia, based on egg-raft shape.

A modification of the ‘natural’ arrangement is suggested for the Ethiopian species of Coquillettidia, based not only on adult and larval characters, but on oviposition behaviour as judged by egg-raft shape.

The possibility of natural interspecific hybridisation is mentioned.

The general slowness in many of the life processes found in the genus is put forward as an adaptation to its peculiar mode of life.

As part of a general study of the conditions required for satisfactory maintainance of Pieris brassicae (L.) in laboratory culture, an investigation was made of the factors affecting mating behaviour. Notes are given on certain characteristics of the culture from which the experimental material was drawn.

It was established that P. brassicae, over one day old, mated readily at temperatures between 20 and 32°C. provided the daylight illumination was above about 200 lumens/sq. ft. Mating occurred more readily at the higher temperatures and illumination levels than at the lower. It was depressed at very high atmospheric humidities. The size of the cage in which the insects were held was not critical, and pairs formed readily in cages as small as one cubic foot. The population density in the cage was also varied over wide limits without significantly influencing the rate at which pairs formed.

Mating took place much less readily in the artificial lights which were tested than in daylight. The most satisfactory light was found to be bilaterally arranged ‘daylight ’-type fluorescent lamps. The level of mating in this light would probably have been sufficient to maintain a culture but it was far lower than in daylight of the same intensity.

After mating, the females do not usually pair again for five or more days. The males, however, mate more frequently and will often pair several times in the same day.

Field trials were conducted in certain eastern counties of England in the years 1957–1959 to assess chemical control methods applied at sowing time against wheat bulb fly, Leptohylemyia coarctata (Fall.). Combine-drilled treatments, using fillers of aluminium silicate, brick dust, granular clay, superphosphate or compound fertiliser, included aldrin at rates from 0·3 to 5·5 lb., dieldrin at 2 and 4 lb., and heptachlor at 2 lb. active ingredient per acre, respectively. Seed-dressing treatments applied with organo-mercury fungicide included 40 and 60 per cent. dieldrin and heptachlor, 40 per cent. aldrin, 60 per cent. Thiodan, 40 per cent. γ BHC with and without organo-mercury, all applied at 2 oz. per bushel of seed; 60 per cent. dieldrin, heptachlor and Thiodan were also tested at double the intended rate of 5 oz. per bushel.

No form of chemical control was completely effective in suppressing damage but all gave some, and usually a great, improvement, particularly on late-sown or backward crops. Most of the insecticides tested gave closely comparable results. Seed dressings containing at least 40 per cent. heptachlor, dieldrin, aldrin or γ BHC were slightly more effective than combine-drilled insecticidal treatments, with the added advantage of applying only relatively small amounts of persistent insecticides to the soil.

Slight symptoms of phytotoxicity were observed on two sites in 1958 following the use of γ BHC and dieldrin seed dressings applied at the normal rate of 2 oz. per bushel and severe symptoms on two trials in 1959 to seed over-dressed with insecticide and organo-mercury; elsewhere the seed dressings employed appeared to have no adverse effect upon plant establishment.

Dieldrin, aidrin, heptachlor and Thiodan seed dressings behaved similarly in killing a high proportion of larvae within attacked shoots; γ BHC reduced the number of larvae entering the plant, but those which did succeed in entering developed in an apparently normal manner.

On fields where drilling was delayed and the attack severe, the optimum rate of combine-drilled aldrin was probably between 1 and 2 lb. active ingredient per acre. No significant increase in yield was obtained at rates much higher than 2 lb. per acre. While fine-dust formulations gave effective results, the use of a granular fertiliser base improved the flow through the combine-drill and gave increased tillering with slightly higher yields. Heptachlor combine-drilled at 2 lb. active ingredient per acre was slightly superior to aldrin at the same rate.

No adverse effects were recorded when insecticidal seed dressings and combine-drilled aldrin were used together, and at high levels of infestation the double treatment gave increased yields, though insufficient to justify its use on fields having only moderate egg populations.

A study has been made of the length of life, fecundity, oviposition and the effects upon them of adult nutrition in the varied carpet beetle, Anthrenus verbasci (L.).

The length of the inactive (unmated) life for males and females at 20°C. and 70 per cent. R.H. was 7·5 and 7·7 days, respectively. This period, which is spent in the moulted last larval skin, decreased with rise in temperature, from a mean of 32·4 days at 10°C. to 3·8 days at 25°C. Humidity differences had relatively little effect.

The effects of various diets on the length of life, oviposition cycle and fecundity of active adults were observed. The experimental diets were water, water with pollen, water with albumen, sugar solution, sugar solution with pollen, sugar solution with albumen, and the control group in which the beetles were deprived of food and water. The sugar solution was a mixture of equal parts of glucose, sucrose and fructose in water.

There were no differences in length of life between male and female beetles (males 18·2–20·9 days, females 22·1–26·1 days) given water, water with pollen, water with albumen and those deprived of food and water. But there was an increase for both sexes when the beetles were given sugar solution, and a further increase, to a mean of 58·3 days for males and 69·5 for females at 20°C. and 70–90 per cent. R.H., when albumen was added to the sugar solution. However, although sugar solution with pollen increases still further the length of life of the males, that of the females was no different from what it was on sugar solution alone.

The preoviposition period ranged from 3–14 days with a mode about the fourth day.

The oviposition cycle consisted of three clearly denned peaks of oviposition on about the 6th, 12th and 17th days. There was a similar pattern in all the groups except that those given sugar solution continued to lay, at a low rate, after the end of the third peak.

The fecundity of beetles deprived of food and water was 50·3 eggs; for beetles given water, water with albumen and water with pollen there was a significant decrease; for beetles given sugar solution there was an increase which became significant when pollen or albumen were given in addition to the sugar. Maximum fecundity occurred on a diet of sugar solution with albumen.

There was significant correlation between length of life and weight on emergence for males given water, water with pollen, or water with albumen, and for females given water with pollen or water with albumen. There was significant correlation between fecundity and emergence weight for females deprived of food and water, given water alone and water with pollen.

Observations in eastern England during 1957, 1958 and 1959 showed natural mortality of pupae of wheat bulb fly, Leptohylemyia coarctata (Fall.), to be high. The part of this due to parasitisation is considered in some detail.

At Rothamsted, the main parasite was Trybliographa spaniandra Kerrich & Quinlan, and this affected about 10 per cent, of the population in 1957 and about 5 per cent, in 1958. At Whittlesey and Peterborough, in 1959, parasitisation affected 5·5 and 13·7 per cent, of the populations, respectively. The two main parasites found were Aleochara bipustulata (L.) and A. inconspicua Aubé (Coleoptera, Staphylinidae). Phygadeuon trichops Thoms. (Hymenoptera, Ichneumonidae) also occurred but was much less frequent. Notes and original observations on the biology of these parasites are given.

Several insects and other small arthropods were observed to prey on various stages of wheat bulb fly. Details of these and notes on the biology of some of them are given.

It is suggested that the attachment of the immature stages of certain species of Simulidae to mayfly larvae and to crabs is primarily an adaptation whereby the immobile Simulium pupa can obtain protection against disorientation with respect to the current, and against damage, in an environment where available inorganic substrata are liable to be displaced by violent water movement.

The principal evidence for this is that these associations typically occur in fast-flowing streams or rivers, and that the attached stages of Simulium include a disproportionately high number of pupae and large larvae. Any direct benefit the Simulium larvae themselves may derive from the association is regarded as a secondary feature of it.

Certain responses to physical factors, which might be expected in simulium larvae achieving successful attachment, are briefly discussed.

Pygostolus falcatus (Nees), an endoparasitic Braconid of the subfamily Blacinae, was reared from Sitona lineatus (L.), S. hispidulus (F.) and S. humeralis Steph. of Swedish origin. The life-history and immature stages of P. falcatus were studied in the laboratory at 74°F. and in field cages preparatory to its liberation in Canada as a control agent of the sweetclover weevil, S. cylindricollis Fhs.

The immature stages develop in the haemocoele of the weevil. After deposition, the egg increases in volume to a maximum of 335 times. At eclosion, the cells of the trophamnion dissociate and increase in volume in relation to the growth of the larva. Supernumerary larvae are eliminated soon after eclosion, and one larva only develops in a host weevil. At 74°F., the final-instar larva emerges from the host weevil 15–16 days after deposition of the egg. Development of many first-instar larvae in a wide range of Sitona species was arrested by diapause. Five larval instars are described and illustrated. Oviposition is prevented in weevils in the summer of their development and eliminated in overwintered weevils by the parasite egg and first-instar larva. The weevil dies within hours of emergence of the parasite larva.

Reproduction is parthenogenetic and thely tokous. The maximum number of eggs laid by a female was 46; the number of eggs laid per day per female varied from 0 to 11. Oviposition takes place both in light and in complete darkness and a preference among species of Sitona was not evident. The maximum number of weevils parasitised by a female in a field cage was 39; the number parasitised per day varied from 0 to 8.

The species overwinters as a first-instar larva in weevils which became adult in the previous summer. There were two discrete parasite generations in 1958 in Swedish weevils, both of which developed in early and mid-summer within overwintered weevils. The maximum rate of parasitism of S. lineatus by larvae of the mid-summer parasite generation in 1958 was 73·3 per cent.

The value of P. falcatus as a control agent of Sitona populations is limited by low parasitism of the new weevil generation of the current year and diapause of the first-instar larva.

The history of the use of pyrethrum formulations to control Antestiopsis spp. on arabica coffee in Kenya is reviewed.

The material with which the present work was done comprised three distinct forms of Antestiopsis of doubtful taxonomic status; these were not observed to differ in their response to the insecticidal treatments used.

Laboratory experiments showed that Antestiopsis was highly susceptible to pyrethrum and that the addition of piperonyl butoxide, a pyrethrum synergist, did not affect this response.

Preliminary field experiments showed that concentrations of pyrethrins higher than those found effective in the laboratory were required. A hypothesis is advanced and established that this was due to a variable proportion of insects becoming paralysed and falling off the tree before acquiring a lethal dose.

These observations and experiments suggested a two-phase method of control, using pyrethrum as a non-persistent foliage spray at an economical but effective concentration of 0·005–0·006 per cent, pyrethrins, coupled with a 5 per cent. DDT or 0·5 per cent, dieldrin dust applied to the bole of the tree to form a persistent toxic barrier. The spray removed the bugs from the tree whilst the dust prevented the return of or killed those that had only received a sub-lethal dose of pyrethrum. It seemed unlikely that such a localised application of the persistent insecticide would have any appreciable effect on beneficial insects.

This two-phase treatment has been used successfully both in trials and in commercial practice for the control of Antestiopsis. When the initial population is in excess of 20 per tree, two spray applications and one dusting are necessary to effect control.