This insect has been known for many years as the cause of serious loss to the wheat crops in this country and on the Continent, having been first recognised in 1882, although it probably occurred before that year. In some seasons the damage occasioned by this fly is so severe as to cause the almost complete destruction of the crop in some fields, although more often it results in the crop being made thin and patchy. The damage first becomes apparent in March and April, when the leading shoot of the young plants attacked turns yellow and the plant if small or weak dies off. The injury is caused by the older larva, which feeds within the young shoot. This destruction of the young plants usually occurs in patches about the field, and the bare patches so caused increase in size owing to the larvae moving in the soil from plant to plant, each larva being thus able to destroy several plants. In addition to winter wheat this pest can attack winter barley and winter rye, although such attacks are rare in this country. It can also attack couch grass. Neither oats nor any other crop is attacked. In Great Britain the most severe damage due to this insect has generally occurred in the eastern countries of England and Scotland, although serious injury has also occurred in various other districts, and the severity of the attack has varied enormously from season to season. Damage due to this pest has also been reported from Middle and South Russia, Germany, Austria, Holland, Sweden, Norway, Denmark, France, Tunisia and Mesopotamia.

The value of damage thresholds in determining the need for insecticide sprays against Helicoverpa armigera (Hübner) on cotton was evaluated in 1984 and 1985 in eastern Tanzania. Spraying at thresholds of 10, 20, 40 and 80% damaged squares was compared against spraying on a recommended prophylactic regime of six fixed-interval sprays. In both years, spraying on damage thresholds reduced the number of insecticide applications from six to between one and five without significantly affecting control of H. armigera, seed cotton yield or overall levels of damage to cotton.

Since writing my report on the establishment and work of certain predators on coconut-feeding scale-insects in Seychelles (Bull. Ent. Res., 31, 1940, pp. 253–283) some further records of their progress have been received. These records were taken by Mr. A. Michel under the direction of the Director of Agriculture of Seychelles, to whom I am indebted for the figures. The sampling was carried out in 10 of the localities sampled previously, so that the 1940 figures represent the fourth yearly count in each of these localities. The first count in 1937 was made before the predators had been liberated, while the subsequent counts show the yearly progress in scale reduction which has been achieved since they have been active.

This paper is intended as the first of a series in which it is proposed to record the results of an examination of a large collection of termites from various parts of the Australian continent. The greater part of this collection has been gathered in the northern districts of the Northern Territory, and in North Queensland, but during the past year it has been considerably increased by the addition of numerous small collections received from correspondents in Victoria, Western Australia and South Queensland, and now contains individuals from over 800 colonies. Through the courtesy of the authorities of the South Australian Museum I have been able to examine a number of co-type specimens which have been of the greatest assistance in clearing up many doubtful identifications. In addition to these, I have been able to study many species from localities not represented in my own collection.

Sixty-one Culicoides spp. were collected in Kenya, Uganda and Tanzania between January 1966 and December 1967 using light-traps at 35 stations on a NW-SE transect from the Indian Ocean to central Uganda to evaluate the distribution of Culicoides spp. among ecological zones. Most species were confined to one or at least very few similar habitats. The largest number of species (30) occurred in the forest zone, probably because of the many suitable breeding sites, whereas only three species were recorded from the dry bushland zone. Forests also contained more exclusive Culicoides spp., whereas savanna species showed a wider distribution, suggesting that the forest species are less adaptable than others. The disease vectors C. grahamii Aust. and C. pallidipennis C, I. & M. were among the most abundant and widely distributed species.

An experimental attempt was made to produce a fly-free corridor through a belt of savannah woodland containing the tsetse fly G. swynnertoni.

An area two miles wide and four miles long was treated with a coarse spray of a 4·6 per cent, w/v solution of DDT in Shell Diesoline. The dosage per application was 0·5 gallons per acre, and seven applications were made, at intervals of approximately two weeks, so that the treatment covered two pupal periods.

The fly density had fallen to a very low level by the end of the experiment, and the area remained virtually free from flies for the subsequent two months. An examination of the data suggests, however, that the fly population was maintained largely by immigrant flies, and was certainly subject to wide variations, and it seems certain that the effect of the applications would have been considerably less upon a stable, self-supporting population.

The drop spectrum of the ground deposit had a mass median diameter of 0·35 mm., and the recovery of insecticide in the area was approximately 60 per cent. Leeward and under sides of obstacles did not receive a dose although in some cases dosages were obtained on apparently leeward sides, probably because of local reversals of wind direction.

The effect of density of the Shin-Etsu twist-tie rope pheromone formulation (PBW rope L®) on mating of female pink bollworm, Pectinophora gossypiella(Saunders) was tested in Israel. The success of mating disruption was evaluated during 1997 by the mating table technique, comparing the percentage of mating of virgin sentinel females in pheromone-treated and control plots. Under low pest population pressure application of ‘long-life’ formulation of P. gossypiellapheromone, PBW rope L®, spaced 9 m, 11 m and 14 m apart, resulted in very high suppression of mating (96.5–100%) and complete shut-down of pheromone trap catch. These application rates were much lower than those now prevailing in Israel and elsewhere. Spacing of ropes 20 m apart resulted in less effective mating disruption of 65% only, and shut-down of pheromone traps was also incomplete. The tests during 1998 were carried out at high pest population and efficacy of treatments was assessed by the reduction of male capture in traps in pheromone-treated plots relative to catches in the control. The distance between pheromone sources proved to be the most critical factor determining success. In both years, any spacing significantly greater than 10 m gave markedly less than complete trap catch shutdown/mating suppression. Pheromone dosages and population density were also important in determining mating success. Results obtained in this study indicate the possibility of reducing the number of pheromone sources per unit area and the total amount of pheromone as compared with that in use today, only at very low pest populations. However at high population levels, dispensers closely-spaced, with increased dosages of pheromone, are required.

Mealybugs (Hemiptera: Pseudococcidae) are important pests for crops worldwide. Different species, cryptic taxa under the same species name or even populations within a species can differ in biological characteristics, such as phenology, resistance to insecticides, virus transmission and susceptibility to natural enemies. Therefore, their management efficacy depends on their accurate identification. Microsatellite genetic markers are efficient in revealing the fine-scale taxonomic status of insects, both at inter- and intra-specific level. Despite their potential uses, microsatellites have been developed only for one mealybug species so far. Hence, it is unclear whether microsatellites may be useful to assess mealybug population differentiation and structuring. In this work, we tested the feasibility of developing microsatellite markers in mealybugs by: (i) producing and characterizing microsatellite DNA libraries for three species: Pseudococcus viburni, Pseudococcus comstocki and Heliococcus bohemicus, and (ii) by developing and testing markers for Ps. viburni. The obtained libraries contained balanced percentages of dinucleotide (ranging from 15 to 25%) and trinucleotide (from 5 to 17%) motifs. The marker setup for Ps. viburni was successful, although 70% of the primers initially tested were discarded for a lack of polymorphism. Finally, 25 markers were combined in two multiplex polymerase chain reactions with 21 displaying no evidence of deviation from Hardy–Weinberg equilibrium. Ps. viburni markers were tested on one population from France and one from Chile. The markers revealed a significant genetic differentiation between the two populations with an Fst estimate of 0.266.

The so-called short-horned locusts are frequently, for convenience sake, regarded as comprising two classes: the true locusts (Arabic: Girad) and the short-horned grasshoppers (Arabic : Gabura). It is difficult, however, to find definitions of these classes by means of which every species may be correctly assigned to its true place. The swarming habits of the true locust are often cited as connoting this class only, involving, as these habits do, the periodical appearance of excessive numbers of both hoppers and adults. Moreover the true locust is gregarious, in that the hoppers move in bands from one place to another, and the adults fly in vast swarms often over long distances. The fact that the grasshoppers are solitary in habit and manifest mutual independence of action is often taken as their chief distinguishing character. There is no doubt that these features do partly separate these two classes of insects from each other, but there are certain species which appear to occupy a position intermediate between the two. One normally solitary may, in certain circumstances, multiply rapidly and give rise to hoppers, which in certain respects act like those true locusts. Moreover the winged adults may undertake short massed flights resembling the migrations of swarms. On the other hand the fact, now fully established, that most true gregarious locusts have their solitary forms, which never associate, places even them in this respect with the grasshoppers.

Aedes ledgeri Huang, A. soleatus Edw. and A. calceatus Edw. of the group of A. aegypti (L.) of the subgenus Stegomyia collected on the coast of Kenya are distinguished on the strength of ecological and genetic (isozyme) data. The preferred oviposition sites of A. ledgeri and A. soleatus were tree holes above ground level, whereas A. calceatus favoured abandoned gastropod shells. A. ledgeri was most abundant in ecotonal habitats and A. soleatus in undisturbed forest At least two diagnostic enzyme loci separated each of the three species pairs.

The damage caused to cotton by the yellow tea-mite,Hemitarsonemus latus(Banks),was first seen in Uganda in 1945 and is now known throughout the important cotton-growing areas of the country. Experiments on cotton in the Belgian Congo showed that sprays and dusts of several insecticides would control or prevent infestations of H.latus;earlier published work in Ugandasuggested that BHC reduced tea-mite damage and DDT increased it,when both were appliedas sprays from wettable powders.However,tea-mite damage was not noticeable on trials in which single rows of cotton were sprayed with DDT emulsion,or on large-scale trials using DDT formulated as a water-miscible liquid. These trials were all directed against the pest insects Earias spp. and Lygus vosseleri Popp.,the standard rate of application being 1 lb. active ingredientper acre applied four times at ten-day intervals.

The Onion Fly (Delia antiqua (Mg.)) was bred at Wye, Kent, under insectary and laboratory conditions to obtain further information on its biology and reactions to various temperatures.

A comparison of the times of emergence of overwintering generations of Onion Fly and Cabbage Root Fly (Erioischia brassicae (Bch.)) in an insectary showed that the former emerged consistently about a month later than the latter. This supported the observations of previous workers that the Onion Fly was not active in the field until late May.

A diet containing protein was necessary for oviposition. The length of the preoviposition period was affected by temperature. Flies maintained at 25°C. laid eggs in 10–24 days, with an average of 15 days. At spring and summer laboratory temperatures (12–29°C.) the preoviposition period was 10–25 days, with an average of 15 days; and in autumn and winter (11–20°) it was 11–46 days with an average of 21 days. Flies maintained at 6–8° did not lay eggs.

Flies in captivity laid up to 123 eggs at the rate of 1–45 per day. Intervals between batches of eggs varied from 1–9 days, and the oviposition period was 7–25 days. Flies lived up to 6 days after oviposition.

The incubation period depended on the temperature. Eggs at 25°C. hatched in 2 days; at 20° in 3–4 days; at 15° in 4–6 days; and at 7–10° in 9–14 days.

The temperature also affected the duration of larval and pupal stages. At 25°C. the successive larval stadia required 2, 2 and 5–9 days, respectively. Lowering the temperature increased the time for development until at 9–11° the three larval stadia required 8–12, 8–18 and 24–37 days, respectively. At 25° the pupal stage lasted 12–17 days; at 20° it was 16–25 days, and at 15° it was from 35 days to over a year. At 25–30° the development from egg to adult was completed in 25 days; at 25° it required 28 days; at 22–27°, 30 days; at 19–24°, 33 days.

At 25°C. the Onion Fly bred continuously without diapause. When larvae were reared at temperatures below about 18° pupal development was often retarded. Pupae formed from larvae reared at 12–18° and maintained at approximately that temperature, required 94–442 days to complete their development. By raising the temperature of pupae formed from larvae reared below 18°, it was demonstrated that a true diapause had been induced. Of 54 pupae raised to 25°, 8 (15%) completed their development in the expected time (13–16 days) and 46 (85%) required 94–208 days. Of 322 pupae formed from larvae reared in an insectary in May and June at 10–18° and exposed to July temperatures of 13–20°, 37 (11%) emerged in 25–35 days and 252 (78%) required 234–294 days. Similarly, of 283 pupae formed from larvae reared at 12–21° and exposed to a temperature of 15–23°, 30 (11%) completed their development in 21–31 days while 253 (89%) required 118–341 days. Exposure to low temperatures was not necessary to terminate pupal diapause.

This mosquito has only once been recorded from Palestine, namely, by Mr. P. J. Barraud (Tabgha 1918), and it was thought to have been introduced from Egypt by a transport of E. L. C. Mr. P. A. Buxton and I failed entirely to find it during two years’ collecting.

With the rapid development of Northern Nigeria, following the British administration and the completion of the railway from Lagos to Kano, problems hitherto of minor importance are continually coming into prominence. Amongst these the abatement of trypanosomiasis is a matter of medical and entomological interest. As the confidence of the people grows there is an increase of intercommunication, which inevitably involves a danger of the spread of such diseases as sleeping sickness from existing foci. In Northern Nigeria these foci are at present peculiarly isolated, but they will gradually lose their isolation as the efforts made to stimulate the agricultural development of the country meet with greater success and the growing demand for roads, feeders for the railway, and better means of transport, is satisfied. In a densely populated and naturally fertile country like Ilorin the problem of avoiding this danger is particularly insistent, but unfortunately also particularly difficult. In the neighbouring province of Kabba sleeping sickness is said to be endemic, and might readily move westwards with the opening up of the interior ; and in a large part of the province of Ilorin itself tsetse-flies already spread disease amongst the cattle and horses to such an extent that these animals cannot live. Nevertheless, during the dry season, herds of cattle pass, day after day, in an almost continuous stream along the highroads on their way to Lagos from the north. How many die on the journey no one can tell, for the fate of those that sicken is to be butchered by the way, and it is a common experience to come across a carcase hewn up and laid out for sale by the road-side (Pl. I, fig. 1).

Simulium metallicum Bellardi larvae were collected from a variety of sites in the three onchocerciasis foci in Mexico. Their head patterns and body coloration were scored before the larvae were cytologically analysed. Cytotypes A, B, H and I were collected and in the majority of cases they could be distinguished from each other by larval morphology. An undescribed cytotype (termed cytotype X) was found in Oaxaca which, on the basis of larval morphology, was indistinguishable from cytotype B.

Chlorphoxim resistance is found in forest strains of Simulium sanctipauli Vajime & Dunbar, in some areas of the Onchocerciasis Control Programme in West Africa. There is an increase in esterase activity in both adults and larvae in the resistant compared to the susceptible strain with the general esterase substrate 1-naphthyl acetate. This appears to be associated with the temephos and chlorphoxim resistance which are found in the same resistant strain. It is possible that one or more esterases are qualitatively and/or quantitatively changed in the resistant strain compared to the susceptible. Preliminary studies indicated that esteratic hydrolysis and oxidative cleavage were both involved in chlorphoxim metabolism in S. damnosum Theobald sensu latu. There was evidence of an increase in detoxication by both these routes in the resistant compared to the susceptible strain of the cytospecies S. sanctipauli. The increase in oxidative detoxication seen in the resistant strain was associated with a slight, but non-significant increase in cytochrome P450 as measured by the sodium dithionite reduced carbon monoxide difference spectra.

The bruchid Bruchidius atrolineatus (Pic) causes significant damage to the stored protein rich seeds of cowpea, Vigna unguiculata, in the West African Sahel. Twenty varieties of cowpea were evaluated for susceptibility to attack by B. atrolineatus in the laboratory. The bruchid showed differential response to the seeds in terms of developmental period, percentage adult emergence, seed weight loss due to feeding by one larva, adult weight at emergence and life-time fecundity of females reared from them. Based on these criteria, IT85F-2205 and IT84S-275-9 were the least susceptible varieties. The development of B. atrolineatus was most significantly delayed in these varieties. The beetle larvae consumed less of their seed material and adults reared from them were smallest and least fecund. The varieties IT87S-1393, IT90K-391 and IT84D-460 also had relatively lower susceptibility to the beetle than others. In a no-choice oviposition experiment, B. atrolineatus females laid equally on all varieties. Percentage egg hatch on the different cowpea varieties did not differ significantly. The results are discussed in relation to previous reports on susceptibility of cowpea and other legumes to bruchids.

All of the pupae, totalling over 3,750, produced by 320 laboratory-bred females of Glossina austeni Newst. allowed to feed from rabbits’ ears, were weighed soon after deposition. Pupal weights were relatively low initially but increased during the first 30 days of the females’ productive life, were high during the next 100 days or so and thereafter declined to less than the initial level.

In the absence of insecticide there may be intense selection against alleles conferring insecticide resistance, so that these alleles will decline in frequency. On the other hand, selection will act to favour alleles at modifier loci which cause resistance alleles to become coadapted and increase in fitness even in the absence of insecticide. The relative effectiveness of these two processes is of practical importance and theoretical interest. The fate of polymorphism for malathion resistance was studied in the saw-toothed grain beetle, Oryzaephilus surinamensis (Linnaeus). Five to six lines of each of four strains (8401, 8401sel, 8518B and L1040), each polymorphic for resistance phenotypes, were maintained in insecticide-free culture for up to nine generations, over which period the response of individuals to a discriminating dose of 65 mg m-2 malathion was determined. There was significant reversion to susceptibility in the related strains 8401, 8401se1 and 8518B. Assuming resistance to be primarily controlled by a single major locus, resistant homozygote and heterozygote fitnesses in the absence of insecticide were estimated to be 0.92, 0.83 and 0.68, respectively. The initial frequency of the resistant allele was inversely related to the time since last exposure to insecticide, and also to the fitness of the resistant allele. This could be explained by the selection of modifier alleles that reduce the fitness cost of resistance in the absence of insecticide. In strain L1040 the proportion of resistant individuals actually increased over time (after the second generation) in the absence of insecticide. The fitness of the susceptible allele in this case was 0.83. In all strains there was significant variation among lines in relative fitness and initial resistance allele frequency. Analysis of knockdown proportions revealed highly significant variation between generations that is not easily interpreted in genetic terms but is better explained by limitations of the knockdown bioassay.

Female oriental armyworm moths, Mythimna separata (Walker), emerged without discernible oocytes in the ovarioles, and reproductive maturity, on the criterion of onset of calling behaviour, was associated with an intermediate stage of oocyte development. Ingestion of carbohydrate was required for completion of oocyte development in the majority of females although a proportion matured when allowed only water. Among females kept alone, these were exclusively moths from a strain selected for early onset of calling but, in the presence of a male, a few females from an unselected line also called and achieved oocyte maturation, without access to carbohydrate. Thus factors other than ovarian development apparently influence the commencement of calling. The absence of an effect of carbohydrate uptake on pre-calling period supports a previous conclusion that this trait is determined primarily by genetic components in this species. It is concluded that ingestion of carbohydrate is important for the attainment of reproductive maturity in M. separata but that it has a differential effect in early and later-calling genotypes. The implications of the results for the reproductive and migratory strategies of M. separata, an important agricultural pest, are discussed.