New trap designs for tsetse (Glossinidae), stable flies (Muscidae: Stomoxyinae), and horse flies (Tabanidae) were tested in Kenya to develop a multipurpose trap for biting flies. Many configurations and colour/fabric combinations were compared to a simplified, blue-black triangular trap to identify features of design and materials that result in equitable catches. New designs were tested against conventional traps, with a focus on Glossina pallidipes Austen and G. longipennis Corti, Stomoxys niger Macquart, and Atylotus agrestis (Wiedemann). A simple design based on minimal blue and black rectangular panels, for attraction and contrast, with a trap body consisting of an innovative configuration of netting, proved best. This ‘Nzi’ trap (Swahili for fly) caught as many or significantly more tsetse and biting flies than any conventional trap. The Nzi trap represents a major improvement for Stomoxyinae, including the cosmopolitan species S. calcitrans (Linnaeus), with up to eight times the catch for key African Stomoxys spp. relative to the best trap for this group (the Vavoua). Catches of many genera of Tabanidae, including species almost never caught in traps (Philoliche Wiedemann), are excellent, and are similar to those of larger traps designed for this purpose (the Canopy). Improvements in capturing biting flies were achieved without compromising efficiency for the savannah tsetse species G. pallidipes. Catches of fusca tsetse (G. longipennis and G. brevipalpis Newstead) were higher or were the same as catches in good traps for these species (NG2G, Siamese). Altogether, the objective of developing a simple, economical trap with harmonized efficiency was achieved.

Polovodova's technique for determining the physiological age of mosquitos was used in a study in 1962–64 of the age-composition of populations of Anopheles gambiae Giles and A. funestus Giles resting in houses in two areas of Tanzania. One area was around Muheza, 25 miles from the coast, where the climate is humid and equable, and the other was around Gonja, 80 miles inland, where hardly any rain falls for five months of the year.

It was found that the age-composition was almost identical in populations of A. gambiae and A. funestus at Muheza, about 20 and 23 per cent., respectively, being 3-parous and older and 1 per cent. 7-parous and older in both species. At Gonja, the population of A. gambiae was much younger, 14 per cent, being 3-parous and older and only 0·3 per cent. 7-parous and older. The oldest mosquitos found at Muheza included one 12-parous female of A. gambiae and one female of A. funestus believed to have laid eggs 14 times. No examples of A. gambiae older than 8-parous were found at Gonja.

Dissections to determine the condition of the ovariolar sacs in A. gambiae at Gonja showed that in 87 per cent, of freshly fed parous females an interval of at least 24 hours had occurred since oviposition. At Muheza, 72 per cent, of individuals of this species in the cool season and 52 per cent, in the hot season were in a similar condition.

Marking and recapturing experiments were carried out with females of A. gambiae in order to be able to correlate calendar age with physiological age. The oldest recaptured was 34 days old and was found to have laid eggs 10 times. From data on 60 recaptures, it was concluded that, although there was some irregularity, the first gonotrophic cycle lasted 3–4 days and later cycles 3 days.

Age-specific sporozoite rates in A. gambiae rose from 4·1 per cent, for 3-parous to 32 per cent, for 7-parous and older females, and in A. funestus from 3·2 per cent, for 3-parous to 30 per cent, for 7-parous and older females. Most of the infected 3-parous females were gravid, indicating that few were infective at the beginning of the fourth cycle. On this account it was concluded that some 80 per cent, of malaria infections were transmitted in the fifth, sixth and seventh cycles.

Analysis of the distribution of age-groups indicated that both A. gambiae and A. funestus showed a deficiency of nulliparous females, presumably because greater numbers of this group rested outside houses. From the second to seventh cycles the proportions of successive age-groups in both species at Muheza declined regularly at a rate corresponding to a mortality of 37·8 per cent, per cycle for A. gambiae and 38·6 per cent, for A. funestus, or 14·6 and 15·0 per cent, per day, respectively. Beyond this age the mortality was considerably higher. At Gonja, the population of A. gambiae declined at a rate corresponding to a mortality of 51·5 per cent, per cycle for the second to sixth cycles, or 20·9 per cent, per day. Above this age, the mortality was estimated to be higher still.

From the regression of infectivity on age it was estimated that 6·8 and 6·1 per cent, of A. gambiae and A. funestus, respectively, became infected at each blood-meal.

These findings are discussed in the light of current epidemiological theory.

The phylogenetic relationships between genotypes of Bemisia tabaci were compared using ITS1 and CO1 nucleotide sequences. Phylogenetic and minimum spanning network analyses identified six major races, Asia, Bali, Australia, sub-Saharan Africa, Mediterranean/Asia Minor/Africa and New World as well as a large collection of genotypes from the Asia region with no strong association with any of the races. The term race is based on its usage in Mallet (2001). Mating incompatibility occurs between some races. There is insufficient data to raise races to species status, but the data supports the recognition of the six races and an unresolved core of ungrouped genotypes under the single Bemisia tabaci (Gennadius) species name. To clarify the identity of the race to which the B. tabaci under investigation is known, the following nomenclature is suggested, B. tabaci (Asia), B. tabaci (Bali), B. tabaci (Australia) B. tabaci (sub-Saharan Africa), B. tabaci (Mediterranean/Asia Minor/Africa) and B. tabaci (New World). Further, there is insufficient molecular or biological data to support the separation of B. tabaci and B. argentifolii Bellows & Perring and its use should be discontinued.

Heifers were treated with the recommended doses of ivermectin: 0.2 mg/ kg bw by subcutaneous injection or 0.5 mg/kg bw by pour-on. An analytic procedure is described and used for the detection of ivermectin residues excreted in dung. A large amount of the higher pour-on dose was excreted during the first five days after dosing due to a more rapid distribution to intestinal contents. Later faecal concentrations after the pour-on treatment were lower than those found after subcutaneous injection. No degradation of ivermectin was detected in pats exposed in the field for up to 45 days. Ivermectin excreted in dung voided 1–2 days after both treatments significantly reduced the number of dung inhabiting larvae of Aphodius spp. (Coleoptera: Scarabaeidae), but no effect was seen in dung deposited 13–14 days after treatments. Development of cyclorrhaphan larvae was inhibited in dung deposited up to 28–29 days after subcutaneous injection treatment, but only inhibited in dung deposited up to 13–14 days after pour-on treatment. The numbers of Nematocera larvae were not affected. In a laboratory bioassay the Diptera Musca autumnalis DeGeer and Haematobia irritans (Linnaeus) suffered higher mortality in dung from heifers treated by the subcutaneous injection 13–14 days earlier than in dung from heifers treated by pour-on at the same time. After subcutaneous injection, a significant reduction in the rate of decomposition was found in dung from heifers treated 1–2 days earlier, whereas pour-on led to a delayed decomposition in dung collected up to 13–14 days after treatment.

In the Zambezi Valley of Zimbabwe, the numbers of Glossina morsitans morsitans Westwood and G. pallidipes Austen electrocuted on grids placed across their flight paths as they arrived at various natural and synthetic odour sources demonstrated that ox odour comprises two broad fractions of attractants. One fraction can be trapped by a charcoal filter and, in part, consists of 1-octen-3-ol. A more volatile fraction passes through the filter and, in part, consists of carbon dioxide and acetone. Levels of acetone and 1-octen-3-ol in ox odour varied considerably, up to maxima of 24 mg/h and 0·025 mg/h, respectively. Catches were roughly doubled when octenol at 0·5 mg/h was added to ox odour, but declined when the dose was increased to 50–500 mg/h. A synthetic odour consisting of 2 litres of carbon dioxide/mm, 5 mg of acetone/h and 0·05 mg of 1-octen-3-ol/h, was nearly as effective as ox odour for G. m. morsitans but only half as effective as ox odour for G. pallidipes. Increases to the doses of each attractant in the synthetic odour increased the catches, to roughly double those with ox odour. Data for other Diptera are also presented.

An account is given of marking and release experiments with Anopheles gambiae Giles in a coastal area of Tanganyika. Laboratory-reared mosquitos were used, labelled either by the topical application of paint or by the introduction of radioisotopes into the larval breeding pans. Two different isotopes were used, 32P and 35S, and recaptures were recognised by autoradiography.

Routine catching stations were established within a circle of radius of 1¼ miles. Releases were made either in the centre or near the periphery of the experimental area, so that recaptures were possible up to a maximum of 2¼ miles.

The following results were obtained:

1. Of 132,000 mosquitos released, 1,019 were recaptured.

2. The mean flight range of females released in the centre was estimated to be 0·64 mile, and of males 0·52 mile. Of females released on the periphery, the mean range of dispersion was estimated to be 0·98 mile. Individuals of both sexes were caught at the maximum range of 2¼ miles.

3. The dispersion of recaptured mosquitos was shown to be non-random and to be related primarily to the distribution of human settlements.

4. In certain series of releases the direction of the prevailing wind had a definite effect on the dispersal of mosquitos. But in general this was a minor factor.

5. Dispersion during the first day or, in many instances, during the first two days after release was more restricted, compared with that of older mosquitos. But no difference in the distribution of catches was detected between those aged three-nine days and those more than nine days old.

6. Marked females were recaptured up to 23 days after release. Apart from the first two days, the regression of density on age amounted to a daily loss of 16 per cent, of mosquitos from the experimental area. The effect of emigration could not be assessed quantitatively, but it was held to be a minor component of the total daily loss. The relatively high level of mortality suggested by these figures is attributed to the use of laboratory-reared mosquitos.

7. The corrected sporozoite rate in marked females at the time of recapture was 0·8 per cent.

8. The survival of males was only slightly lower than that of females.

9. It is concluded from the survivorship curve that the mortality rate remained constant throughout the period in which marked females were recovered.

Chemical inhibition of feeding has been studied in detail for only a few insect species, but inhibitory chemicals play a considerable part in host-plant selection by a wide range of phytophagous insects from several orders. Many different chemicals are involved, some of them amongst the normal constituents of plants. A few have a general effect, preventing feeding by all the insects which have so far been tested, but the majority are effective only against some species.

Inhibition may function by blocking the input from receptors normally responding to phagostimulants or by stimulating specific ‘deterrent’ cells. The former may have a general effect on all insects, but chemicals in the latter category will only be effective if the insect has neurones capable of responding to them. Hence these will have more specific effects.

Inhibitory chemicals may be applied to plants in the same way as insecticides, their advantage being that the parasite/predator complex of species not feeding directly on the plant will be unharmed. An alternative approach is to breed resistant varieties of plants by selecting for inhibitory attributes. Although many varieties of crops are known which are insect-resistant, the basis of the resistance is generally unknown. A more thorough understanding of the mechanisms involved in inhibition of feeding by chemicals would enable a more logical approach to be made to the development of resistant plants.

It is felt that the 24-hour catch presents a valuable method of studying the biting-behaviour of mosquitos in the field, and further that conclusions concerning seasonal abundance, vertical distribution and times of biting-activity must be based on catches of this type if serious errors of interpretation are to be avoided.

The time-divisions of the catch should not exceed one hour, and even shorter intervals may be desirable. Timing should be related to the actual times of sunrise and sunset. Where possible, a series of consecutive catches should be carried out, and a shift system must be carefully considered in relation to the particular series projected.

Usually the results from different levels above ground should be treated separately in working out biting-cycles, and this may also apply to results from different seasons or different localities. Further, while in some instances the summation of long series of catches seems permissible, in others it is not, and in these detailed analysis of the figures may be necessary before consistent behaviour-patterns become apparent.

In cases where a measure of the central tendency is to be employed, the geometric mean as modified by C. B. Williams appears to be the most suitable.

Information relevant to invasion processes and invasive alien insect species management in Central Europe was extracted from two databases: a compilation of two inventories of alien insects in Austria and Switzerland, and a list of interceptions of non-indigenous plant pests in Europe gathered by the European and Mediterranean Plant Protection Organisation (EPPO) for the period 1995–2004. For one-third of the insects established in Switzerland and Austria, the region of origin is unclear. Others come mainly from North America, Asia and the Mediterranean region. Among the intercepted insects, 40% were associated with commodities from Asia, 32% from Europe and only 2% from North America. Sternorrhyncha, Coleoptera and Psocoptera were particularly well represented in the alien fauna compared to the native fauna. In the interception database, Sternorrhyncha were also well represented but Diptera accounted for the highest number of records. Sap feeders and detritivores were the dominant feeding niches in the alien insect fauna. In contrast, external defoliators, stem borers, gall makers, root feeders, predators and parasitoids were underrepresented. Nearly 40% of the alien insects in Switzerland and Austria live only indoors. Another 15% live outdoors but exclusively or predominantly on exotic plants. Less than 20% are found mainly in ‘natural’ environments. The majority of introductions of alien insects in Europe are associated with the international trade in ornamental plants. An economic impact was found for 40% of the alien insects in Switzerland and Austria, whereas none is known to have an ecological impact. The implications of these observations for further studies and the management of alien species in Europe are discussed.

The parasitoid Anagyrus kamali Moursi was recently introduced into the Caribbean as a biological control agent against the hibiscus mealybug, Maconellicoccus hirsutus Green. In the laboratory, parasitoid size, as measured by left hind tibia length, was positively correlated several indicators of the parasitoid‘s fitness: longevity, mating preference, fecundity, reproductive longevity, progeny emergence and sex-ratio. When fed ad libidum with honey drops, large male parasitoids lived significantly longer (29.1 ± 6.5 days) than small ones ± 5.7 days). Large females also lived significantly longer (35.4 ± 10 days) than small females (27.9 ± 9.6 days). Females showed no significant mating preference between large and small males. Lifetime fecundity was positively correlated with the size of adult females ranged from 37 ± 21 eggs for small females to 96 ± 43 eggs for large ones. The reproductive longevity, daily oviposition rate, and number of progeny were also higher among large parasitoids. The sex ratio of progeny from small female parasitoids was higher (0.76 ± than that of large individuals (0.47 ± 0.18).

The diamondback moth, Plutella xylostellaLinnaeus (Yponomeutidae), remains one of the most serious pests of crucifers in many parts of the world, particularly in South East Asia. This paper reviews the wide array of strategies which have been used in attempts to control P. xylostella over the last 40 years and consolidates the fragmented and sometimes hard-to-access literature on two and three level trophic interactions (e.g. host plant—herbivore, herbivore—natural enemy and host plant-herbivore—natural enemy interactions) involving the pest. Special reference is made to studies and examples from South East Asia, and in particular Malaysia, where P. xylostella and its primary parasitoids have been well studied owing to the great economic significance of the pest in this region. It is suggested that a multitrophic approach to research may assist in the development of more sustainable methods for the management of P. xylostella and overcome some of the problems inherent with insecticide-intensive methods.

A critical review is presented of the many and varied procedures for sampling adult mosquitoes. All sampling methods are subject to bias, but human-bait collections are probably the most reliable single method for detecting and monitoring populations of anthropophilic species. The estimation of realistic man-biting rates, however, remains difficult. The recent advances in computer technology have generated considerable interest in population modelling, with the aim of getting a better insight into the complexities of population dynamics, mosquito control and disease transmission. Although such approaches may be informative, it is stressed that models should be based on meaningful values of the critical parameters and that these are best obtained from field populations. The difficulties of interpreting mosquito collections in both attractant traps, such as animal-baited traps, carbon-dioxide-baited traps and light-traps, and in non-attractant ones, such as Malaise traps, sticky traps, ramp traps, rotary traps, suction traps and vehicle-mounted traps, are described. Suction traps probably provide the least biased catches of aerial populations of mosquitoes, but, if populations as a whole are to be considered, then resting adults also must be adequately sampled, and this may prove difficult. It is emphasised that different trapping techniques usually sample different components of a population, and that the choice of sampling methods depends much on the type and quality of information required. The limitations of using mark-recapture techniques to study adult dispersal and obtain absolute population estimates are discussed, together with the advantages and disadvantages of applying simple and more complex mathematical procedures for analysing recapture data.

Non-chemical control of termites in agriculture and forestry is attracting renewed interest following increasing restrictions on the use of persistent organochlorine (cyclodiene) insecticides. Non-chemical control involves methods which attempt, without using commercial pesticides, to (i) prevent termite access to the plants, (ii) reduce termite numbers in the vicinity of the plants or (iii) reduce susceptibility/increase resistance of the plants themselves. There have been few adequate trials of any of these methods. Numerous cultural procedures have been suggested, including measures to enhance plant vigour, to manipulate termite numbers and behaviour, and others whose mode of action is unclear. Many are simply part of good agricultural/silvicultural practice and to be recommended. Biological control by predators or pathogens is unlikely to be successful due to the termites' social structure and behavioural responses to infected individuals and to loss of individuals to predators. The use of ‘natural’ insecticides from locally available plant products may be effective in some cases but, as they are not subject to the same rigorous safety and environmental evaluation as commercial pesticides, their use cannot be sanctioned unconditionally. Other locally available products, e.g. wood ash, have not been adequately evaluated. Removal of reproductives from the nest and construction of physical barriers may have limited applications, but resistant species and varieties, combined with appropriate cultural methods and, perhaps, minimal use of modern pesticides in an integrated approach, offer the greatest potential for a long term solution. The lack of critical scientific evaluation of non-chemical control makes it a field wide open for research.

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.

Field infestation rates of an invasive fruit fly species, Bactrocera invadens Drew Tsuruta & White on mango was determined at different localities in Kenya. At most of the locations and especially at low elevations, B. invadens frequently shared the same fruit with the indigenous fruit fly species Ceratitis cosyra (Walker) but often occurred at higher numbers than C. cosyra. The level of infestation varied with location ranging from 3.0 to 97.2 flies per kg of fruit. There was a significant inverse relationship between numbers of flies per kg of fruit and elevation at which fruit was collected, suggesting that B. invadens is a predominantly lowland pest. On an artificial diet, development of B. invadens immatures lasted 25 days; egg incubation required 1.2 days, larval development 11.1 days and puparia-adult development 12.4 days. About 55% of eggs developed to the adult stage. Life expectancy at pupal eclosion was 75.1 days in females and 86.4 days in males. Average net fecundity and net fertility were 794.6 and 608.1 eggs, respectively, while average daily oviposition was 18.2 eggs. Daily population increase was 11% and mean generation time was 31 days. Results are discussed in relation to the biology and ecology of the insect and in the development of mass rearing and control measures for B. invadens.

In studies in the Zambesi Valley, Zimbabwe, carbon dioxide alone dispensed at 2·5 to 15 litres/min, or acetone alone dispensed at 0·3 to 300 g·h, increased by up to six times the catches of Glossina morsitans morsitans Westw, and G. pallidipes Aust. from stationary biconical traps, stationary electrocuting traps used with and without a visual target, and a mobile party of hand-net catchers. Catches were increased further when the chemicals were dispensed together. Carbon dioxide at 2·5 litres/min plus acetone at 15 g/h was about half as effective as ox odour for enhancing the catches from an electrocuting trap plus target; the efficacy of carbon dioxide at 15 litres/min plus acetone at 300 g/h was not significantly different from that of ox odour. Several short-chain ketones, and also formaldehyde and propionaldehyde, were attractive. Several long-chain ketones, and also heptaldehyde and caproic acid, were repellent. Carbon dioxide was attractive for Tabanidae, Stomoxyinae and non-biting Muscidae. Acetic acid was repellent for Stomoxyinae and non-biting Muscidae.

A successful technique for feeding colonies of Glossina morsitans morsitans Westw. and G. austeni Newst. in the absence of living hosts is described. Insects are fed through membranes made of silicone rubber or of agar and Parafilm, overlying blood pools poured onto grooved glass plates. The diet employed is fresh pig blood, collected at slaughter, and aseptic procedures are adopted at every stage of diet preparation and presentation. The reproductive performance of these in vitro-fed colonies in terms of adult survival, fecundity, and offspring size, is the same as that of colonies fed on living hosts, when compared over a long period of time. The fact that the technique is successful when used with a diet of pig blood, but is not successful when used with cow blood prepared in the same way, suggests that the technique per se is adequate to elicit a normal feeding response from these tsetse species. The nature of the nutritional superiority of pig blood is not understood.

The coffee berry borer Hypothenemus hampei (Ferrari) is the most serious pest of the world's most valuable tropical export crop. Since the last review on this insect was published six years ago, many new studies have contributed to an improved insight into the biology and ecology of the beetle, and have indicated new avenues for integrated and biological control. The latest developments in research, both laboratory and field, on the pest, its natural enemies and their implications for integrated control of H. hampei are summarized, with a particular focus on the situation in The Americas. Lately, the global coffee industry has changed radically; it has suffered a long cycle of lowest-ever world market prices caused by overproduction and technological change. At the same time, the advent of sustainable certification schemes has had a major impact on the industry. The role of integrated pest management and biological control of H. hampei in an era of changes in the coffee industry is discussed.

Eleven strains of Bemisia tabaci (Gennadius), including a laboratory susceptible strain, were bioassayed as adults with three organophosphorus (OP) insecticides, three pyrethroids and one OP/pyrethroid combination. The contemporary strains were from diverse geographical areas and hosts and included examples of the A-, B-, and non-B-biotypes. All recent collections were multi-resistant to these insecticides which have been used extensively for their control. The patterns of cross-resistance for the OPs were clear but less so for the pyrethroids. All populations that resisted profenofos and cypermethrin also resisted the combination of profenofos and cypermethrin. Although the importance of selection pressure on levels of resistance was not easily quantifiable the highly selected populations exhibited the highest levels of resistance. The significant within, as well as between, biotype variation in resistance factors clearly indicated that insecticide resistance and biotype were not directly related. The roles of acetylcholinesterase sensitivity and general esterase activity in resistance to OPs and pyrethroids are discussed.

The Lepidopterous stalk borers that occur in Uganda in association with the Gramineae were studied there during 1954–1956 by collecting on all likely host-plants at two centres and by a country-wide survey in which stalk-borer damage in cereal crops was qualitatively assessed at five-mile intervals along the routes followed, and the species of borer present in such crops and, where possible, in nearby wild host-plants were determined. The commonest Noctuids were Busseola fusca (Fuller), B. segeta Bowden, Sesamia calamistis Hmps. and S. poephaga Tanas & Bowden. All these attacked sorghum, maize, sugar-cane and (except the last) finger millet (Eleusine coracana.); so also did S. botanephaga Tarns & Bowden, but only near swamps, in which it infested sedges (Cyperus spp.) and reeds (Typha australis), from which the other species were virtually absent. Only S. calamistis and S. botanephaga attacked rice. All attacked Pennisetum purpureum, Sorghum vertictlliflorum, Vossia cuspidata, and (except S. botanephaga) Panicum maximum, and also other wild grasses.

B. fusca is widely distributed but most abundant in areas of intensive cultivation, where crop residues abound in which the resting larvae can survive the dry season. B. segeta is the most frequent species in Pennisetum purpureum and Panicum maximum, which are extremely common over most of the country, but is rare in cereal crops. S. calamistis (to which earlier records of S. cretica (Led.) and S. vuteria (Stoll) must be attributed) is not numerous but occurs in every district except Karamoja, where it cannot survive the dry season; and S. poephaga is known only from northern and eastern districts and is unimportant.

Chilo zonellus (Swinh.), which may be a recent introduction, occurs in all the cultivated host-plants and most of the wild ones except Cyperus and Typha; it has not been found at altitudes above 4,000 ft. in the west or 5,000 ft. in the north and east, but elsewhere it is the prevalent borer and can cause severe damage in dry years and on out-of-season crops. It was the only species besides B. fusca found on bulrush millet (Pennisetum typhoides), the tough stem of which resists attack. On the western border, Eldana saccharina Wlk. attacks sorghum, maize and sugar-cane at high altitudes, and Maliarpha separatella Rag. attacks rice. A fourth Pyralid, Pectinigeria sp., occurs on maize.

When small plots of host-plants were grown in a matrix of sorghum, and also in a swamp, and the whole sampled at harvest for borer infestation, all the cultivated hosts and many of the wild ones suffered some attack, the percentage of stems bored varying from 10 (finger millet) to 89 (sorghum) amongst the former, and reaching 34 (Panicum maximum), 40 (Sorghum verticilliflorum) and 50 (Pennisetum purpureum) amongst the latter. Immature stages of C. zonellus and B. fusca greatly outnumbered those of Sesamia, especially in the more heavily infested host-plants.

Notes are given on the life-histories of the commoner species of borer and on their habits in the field. In the laboratory, the lengths of the life-cycles, in days, were 68–75 (B. fusca), 65–78 (B. segeta), 46–58 (S. calamistis) and 46–53 (C. zonellus). In the dry season, the larvae of B. fusca entered a resting stage, which prolonged the life-cycle to 200 days; such larvae were found only in living or dry stems of crop plants. C. zonellus and Sesamia spp. bred continuously, in the dry season the former being found chiefly in trash, stubble and volunteer tillers of sorghum, the latter in these and living stems of grasses.

Of the principal cereal crops in Uganda, sorghum is the most widespread. The main crop, sown after the longer of the two dry seasons, suffers little borer attack; second crops are more severely affected, but plants with thick stems or numerous tillers nevertheless yield heavily. Finger millet is the staple food crop in the north and west; borer damage is negligible and restricted to small patches of “dead-hearts” caused by larvae from single egg-masses of S. calamistis. Maize is grown on a large scale in the districts bordering Lake Victoria and in the highlands; borer attack is usually very late and, where rainfall is adequate, appears not to afiect yields.

Apanteles sesamiae Cam. and another, unidentified, Braconid probably control S. calamistis, but on the other stalk borers the incidence of parasites, which are listed, is low. Destruction of all crop residues and wild species of Sorghum around cultivated areas would considerably reduce borer attack at the beginning of the growing season, but chemical control was only partly effective and did not increase the yield.