The group of Anopheles barbirostris Wulp is shown to consist of some 11 closely similar species, five of which are described as new. Keys for identification are provided. The group is divisible into two parts, the subgroups of A. barbirostris and A. vanus Wlk.

Two (or possibly three) species in the barbirostris subgroup are disease vectors.

A. barbirostris sensu stricto is the commonest and most variable species of the group and has the widest range, occurring probably from India to the Moluccas excluding only Borneo and the Philippines. Larvae can be found in a variety of breeding places in still or slowly moving water. Throughout its range, except perhaps in the Celebes, it appears to be largely zoophilous and not a vector of disease.

A. campestris sp.n. is very closely related to barbirostris. It appears to be confined to the alluvial plains of coasts and deltas, and may be limited to the mainland of Asia. It is common on the west coast of the Malay Peninsula where it is anthropophilous and an important vector of human (and possibly also simian) malaria, and of filariasis due to the periodic form of Brugia malayi. It is probably at least a minor vector of malaria and filariasis in the plains of Thailand.

A. donaldi sp.n. is the principal member of the group in Borneo, and is locally common in Malaya where the larvae are usually found in more shaded places than those of barbirostris. In Borneo it is a minor vector of malaria and filariasis, and possibly in Malaya also.

A. franciscoi sp.n. is the Philippine representative of the barbirostris subgroup.

A. hodgkini sp.n. is widespread (Thailand, Indo-China, Malaya and Borneo), but seldom common. It is a species of the forest and forest edge.

A. pollicaris sp.n. is an uncommon but easily recognised forest species only known at present from Malaya.

The vanus subgroup consists for the most part of uncommon species having little contact with man and usually associated with forest. A. vanus sensu stricto occurs in the Celebes and Moluccas where it is common, and also in Borneo and the Philippines; A. barbumbrosus Strickl. & Chowd., replaces vanus in the western half of the archipelago and on the mainland; A. ahomi Chowd., is known from Assam; A. manalangi Mendoza is confined to the Philippines; finally there is an unnamed species in Ceylon with speckled legs which was previously identified wrongly as A. pseudobarbirostris Ludl.

Laboratory and field tests were made to investigate the acaricidal properties of Tedion (2,4,5,4′-tetrachlorodiphenyl sulphone) and Kelthane (l,l-di(p-chlorophenyl)-2,2,2-trichloroethanol) and to compare them with Akar 338 (ethyl 4,4′-dichlorobenzilate), malathion (in field tests only), lime sulphur and the organophosphorus compounds Rogor (O,O-dimethyl S-methylcarbamoyhmethyl phosphorodithioate) and Ekatin (O,O-dimethyl S-2-(ethylthio)ethyl phosphorodithioate) against the red spider mite, Oligonychus coffeae (Nietn.), on tea in Assam during 1958–60. The materials were available at the following concentrations of active ingredient: Tedion emulsifiable concentrate (8 per cent, w/v), Kelthane wettable powder (18·5 per cent, w/w), Akar 338 emulsifiable concentrate (25 per cent, w/v), malathion emulsifiable concentrate (56 per cent, w/v), lime sulphur solution (24–26 per cent, polysulphide), Rogor emulsifiable concentrate, (40 per cent, w/v) and Ekatin emulsifiable concentrate (20 per cent. w/v). Tedion was also available as a wettable powder (8 per cent, w/w) and Kelthane as an emulsifiable concentrate (18·5 per cent. w/v). In the laboratory, the first three and Rogor were usually diluted to 1 part in 500 with water, Ekatin to one part in 1,000 and lime sulphur to 1 in 40, but Tedion was also tested in some experiments at 1:750, 1:1,000 and 1:1,500. Using a single-leaf technique in the laboratory, 2 ml. of spray were applied to each leaf. Sprayed directly on to the eggs, Tedion and Kelthane gave equally good kills (97·7 and 90·7 per cent., respectively) and were more effective than Akar 338 (47·9%) or Ekatin (27%). There was some evidence that Tedion may be more effective as a deposit on which eggs are subsequently laid than as a direct spray. It also has a toxic effect on the eggs developing in the ovary, maximum effect (0·5 per cent, viability) being observed in eggs laid on unsprayed leaves on the second day after spraying of the female. The effect declined slowly towards the fifth day and by the ninth day had practically been lost. Rogor was not tested against the eggs. At the concentration effective against eggs, Tedion had only a limited effect (38·7 per cent, mortality) on nymphs and adults 24 hr. after application. However, in two laboratory trials carried out on potted plants to compare the toxicities of Tedion, Akar 338 and lime sulphur under these conditions and to ascertain the persistence of their effects against nymphs and adults, whereas Akar 338 and lime sulphur were significantly more effective than Tedion after 24 hr. at the concentrations used, after one week the effect of the two former showed little change, whilst that of Tedion had increased greatly, and after two weeks was significantly greater than that of Akar 338 in both trials and in one of them after four weeks. The effect of lime sulphur at four weeks was not significantly different from that of Tedion and was superior to that of Akar 338 in one trial. Kelthane, Akar 338, Eogor and Ekatin, and also lime sulphur, gave 100 per cent, kill of nymphs and adults 24 hr. after application by the single-leaf technique. Kelthane, Rogor and Ekatin were not tested for persistence of effect. In the field, all sprays were applied at 100 gal. per acre. The same dilutions of Tedion, Kelthane, Akar 338 and lime sulphur as were used in the laboratory were applied, giving rates of 2·6, 6, 8, and 100 oz., respectively, of active ingredient per acre. Malathion was diluted to 1 part in 500, giving 18 oz. active ingredient per acre, and Eogor and Ekatin to 1 part in 1,000, giving 6·4 and 3·2 oz. per acre, respectively. Counts of numbers of mites on leaf samples taken 3, 7 and 15 days and one month after application in two trials in 1959 and one in 1960 indicated that, at the concentrations used, Tedion, although at almost every count it had reduced the mite population by over 90 per cent., as compared with the control, was not consistently significantly superior to Akar 338, Kelthane and Rogor. There was some indication that Ekatin and malathion might be less effective than Akar 338, Kelthane and Eogor. Lime sulphur was effective for a period up to 7–15 days.

Investigations were undertaken in Jamaica to determine whether or not the application of malathion for the control of the West Indian cane-fly, Saccharo-sydne saccharivora (Westw.), disturbed the natural control exerted by Lixophaga diatraeae (Tns.) on its host Diatraea saccharalis (F.). It was demonstrated, by exposing caged adults of Lixophaga, that adults present in the field at the time of insecticidal application would be killed but because of the short residual action of malathion the reduction in the parasite population would only be temporary. A comparison of the degree of parasitism in sprayed and unsprayed fields did not reveal any evidence of reduction in the rate of parasitism. The extent of damage by Diatraea in sprayed fields was significantly less than in unsprayed ones and factors which might account for this are discussed.

Hofmannophila pseudospretella (Stnt.) is a very widespread and common omnivorous scavenger in Britain. It is able to digest keratin and, while rarely occurring in large infestations, has a nuisance value as a textile pest in dwellings. It is commonly found breeding in birds' nests and dry organic débris likely to be found in attics and roof spaces, and mature larvae wandering from the feeding site are probably the only cause of damage to domestic textiles which, according to our records, are principally carpets.

A method of maintaining cultures in the laboratory and obtaining standardised larvae for mothproofing tests is described.

Adequate protection against newly hatched larvae was given by 0·1 per cent. Dielmoth (25 per cent, dieldrin) and 1·0 per cent. Mitin FF (an unknown percentage of N-(3,4-dichlorophenyl)-N′-2-(2-sulpho-4-chlorophenoxy)-5-chlorophenyl urea, sodium salt), while six-week-old larvae were not controlled by 0·15 per cent. Dielmoth or 1·0 per cent. Mitin FF. No protection against larvae in the wandering stage was given by Dielmoth in concentrations up to 0·63 per cent, or by 1·0 per cent. Mitin FF.

Both six-week-old and wandering larvae were controlled by 5·0 per cent. Mystox B (20 per cent, pentachlorophenol) and the latter also by 4·0 per cent. Mystox LPL (100 per cent, commercial pentachlorophenyl laurate).

The work described in this paper forms part of an investigation into the conditions which influence the breeding of Pieris brassicae (L.) in captivity. Observations have been made on the behaviour of the females at the time of oviposition, on factors which influence oviposition, on the appearance and weight of the eggs and on their fertility and hatching.

Females which are ready to lay seek out green surfaces and, as they respond eagerly to plants from which they are separated by glass, it seems that plant odour plays little part in the attraction. Once they have alighted, however, the insects drum on the surface with their fore legs to test its suitability. Normally they lay only on plants which contain the mustard-oil glucosides, but they have been observed to oviposit on broad bean (Vicia faba), on which the larvae do not survive. Sinegrin applied to green paper stimulates the female to lay. Provided she is standing on an acceptable surface she will oviposit on any other surface, for example, filter paper or glass. The eggs are normally deposited on the under surface of the leaves. This is largely due to a preference for the physical underside but the insects also seem to prefer the morphological under surface of the leaf to the upper surface. When laying an egg, the female locates one previously laid with the tip of her abdomen and so builds up the regularly arranged batches.

The females lived and oviposited as well in small cages as in large cages. They laid more eggs per day, and more eggs in a batch, at 30°C. than at 20°C. Both numbers increased until the female was about six to seven days old and then declined. Oviposition occurs at low light intensities. Fertilised females laid very many more eggs than virgin females. Oviposition occurred two to three days after copulation, and most females oviposited six or seven times in eight days. The number of eggs laid by starving insects is low: it is higher for insects given water or one per cent, honey solution and very much higher for insects given ten per cent, honey solution. Sucrose solutions are as satisfactory as honey solution.

When first laid, the eggs of P. brassicae are yellow in colour and become more orange as they develop. Some batches of newly laid eggs are of a distinctly darker yellow than others but, as it is believed that the eggs are fertilised only just before oviposition, it seems that this colour difference cannot be due to the eggs being in somewhat different stages of development. The number of ribs on the shells seems to vary in different cultures.

Batches of eggs which are laid within an hour of each other may begin to hatch several hours apart, and the time taken for all the eggs in one batch to hatch was found to range from two hours to about seven. A fertilised female lays scarcely any infertile eggs. The fertility after one mating falls below 100 per cent, after about 14 days, but normally the female mates again before this time. Temperature naturally affects the time taken by the eggs to hatch. The shortest time was about 3¾ days at 28°C.; the longest observed was 17 days at 12·5°C.

The eggs cannot be stored for more than ten days at 3·5°C. and 50 per cent, relative humidity. Eggs will develop and hatch at very low humidities. If the eggs are detached from the surface on which they are laid by the use of acetone their capacity to develop and hatch in air dried over phosphorus pentoxide is substantially reduced.

An account is given of work carried out since that of Wootten & Sawyer (1954) on the pick-up of spray droplets by flying locusts. The same species, Schistocerca gregaria (Forsk.), was used. The values given in their work for the amounts of spray collected were confirmed, but when observations were extended to cover smaller droplets (less than 50-μ. diameter), locusts were found to collect these much less efficiently.

Other factors affecting pick-up were sex (females collected more spray than males) and flying speed (faster-flying locusts tended to collect less spray per unit of distance flown). When the angle of approach of the droplets to the flying locusts was varied between 1 and 11° from the horizontal no difference in the pick-up of spray could be detected.

For droplets between 60- and 300-μ diameter, the dose of insecticide collected by the locusts is given by the formula 9xPC μg. for males, and 11·5xPC for females, when the locusts fly through a concentration of spray of C ml. per cu. m. for a distance P m. and the spray solution contains x per cent, (w/v) of insecticide.

Earlier types of suction sampling apparatus, driven by electric or petrol motors, are briefly reviewed and their disadvantages for work in remote areas indicated. To overcome these a cheap, simple, hand-operated model has been developed and the construction of this is described. However, unlike some of the motorised models, it does not extract all the fauna from the area sampled.

The tsetse fly population of Block 9 at Shinyanga, Tanganyika, consisting of 40–50 square miles of thorn bush, was studied from 1935 to 1957 by means of fly-rounds with a total length of 30 miles. The mean annual apparent density (A.D.) of Glossina swynnertoni Aust., taken as the geometric mean of the 12 monthly figures, is plotted on a graph covering 23 years, together with data for 1930–36 from another block which, however, is only doubtfully comparable. Four peaks and five troughs occur on the graph of Block 9, the highest value being 18 times the lowest. The history of the natural and artificial events which have occurred in the block are detailed as far as they are known. The minimum A.D. was that of 1938, after a number of wild animals had died of rinderpest; thereafter, the A.D. rose for several years, in spite of certain anti-tsetse measures, and none of the fluctuations subsequent to 1938 can be associated with any natural or artificial event. The amplitude of the fluctuations is small compared with records in the literature for other animal populations, and their occurrence is irregular; the last peak observed was in 1954, but limited observations in 1959 gave catches little, if at all, below those of 1954.

The data were also analysed for seasonal variations. The least monthly mean catch was that of November, the greatest, differing from the least by a factor of only 1·34, that of April. Earlier published accounts of G. morsitans Westw. (based, however, on relatively short periods) give later maxima and greater amplitudes. Annual and seasonal records of the percentage of teneral individuals among male flies and the percentage of females among non-teneral flies are also given, but these data cannot be interpreted at present.

Research on Lepidopterous stem borers of Nigerian cereals began in 1951. Preliminary surveys finished in 1954 and from 1955 to 1961 the author studied these pests in Northern and Western Nigeria.

Guineacorn (Sorghum vulgare) and millet (Pennisetum typhoides) are the most important cereal crops in Northern Nigeria, and maize (Zea mays) is the only cereal of any importance in Western Nigeria. The crops are sown early in the wet season, which alternates with a dry season of two to seven months, and mature in three to five months. They are cultivated by hand and few farmers grow more than one acre of any one cereal.

The host ranges of all the known species of Nigerian cereal stem borers (viz., Busseola fusca (Fuller), Sesamia calamistis Hmps., S. penniseti Tams & Bowden, S. poephaga Tarns & Bowden, S. nonagrioides botanephaga Tams & Bowden, Manga basilinea Bowden, Coniesta ignefusalis (Hmps.), Chilotraea sp. ? argyrolepia (Hmps.), Chilo sp. ? phaeosema, Martin, Maliarpha separatella Rag. and Eldana saccharina Wlk.) are summarised and their distribution in Nigeria and relative importance there are discussed.

B. fusca and Coniesta ignefusalis are the most important stem borers of guineacorn and millet, respectively, and detailed accounts of their life-cycles and seasonal cycles are given, together with observations on adult activity, light-trap catches, larval migration, larval morphology and the effects of larval feeding patterns on plants of guineacorn and millet. Differences between the pupae of the three Noctuid genera (Busseola, Sesamia, Manga) and all stages of C. ignefusalis are illustrated. Some information on the biology of S. calamistis, S. poephaga and M. basilinea is also given.

At Samaru, the life-cycles of B. fusca and G. ignefusalis are completed in about two months under field conditions and in the absence of diapause. Three generations develop during the growing season, larvae of the third entering diapause until the next season. Many diapause larvae survive the dry season in crop residues, and the local practice of stacking stems for later use in building, etc., ensures reinfestation of subsequent crops, particularly near villages. The diapause ends between late April and early June, so that adults of the diapause generation emerge about three weeks after millet and guineacorn have germinated. Experiments indicate that diapause is terminated when larvae are provided with moist food or drink water. The relative abundance of B. fusca and C. ignefusalis in guineacorn, millet and maize largely reflects host selection by ovipositing females. C. ignefusalis lays freely only on millet and is therefore mainly confined to this crop, whereas B. fusca, though favouring guineacorn, also lays on the other two crops. Experiments indicate that more eggs are laid on larger plants.

Early millet and maize are harvested before borer populations reach their highest level. Guineacorn tolerates the considerable damage done by the high populations present at the end of the season but late millet and second-crop maize do not. Any factor hindering normal crop development tends to increase the damage done.

A provisional list of 14 primary parasites, three hyperparasites, one predator and four diseases is given. Tetrastichus atriclavus Wtstn., Apanteles sesamiae Cam., and Pediobius furvus (Gah.) were always present on B. fusca at the end of the season. Syzeuctus sp. was the most important parasite of C. ignefusalis and was regularly reared from diapause larvae, and other common parasites of this species later in the season were Sturmiopsis parasitica (Curran), T. atriclavus and Hyperchalcidia soudanensis Steffan. The over-all rate of parasitism seldom exceeded 10 per cent, of all larvae and pupae collected. Bacillus thuringiensis killed many diapause larvae of B. fusca and was the most important disease recorded.

The results of experiments relating yields to stem-borer attack in maize, early millet, late millet and guineacorn are presented and discussed. Early-sown maize suffers little damage but second-crop maize at Ibadan suffers losses of stand which, in local farms, generally exceed 20 per cent. In experiments, loss of stand did not always result in loss of yield, and evidence is presented that, under certain conditions, loss of stand is compensated for by the production of heavier cobs. At Samaru, the development of single larvae of B. fusca in otherwise healthy stems reduced their yielding capacity by 28 per cent, of the mean cob weight of healthy stems (P <0·001).

In six experiments on early millet, little reduction in yield occurred, even when infestations were much higher than those normally experienced, but late millet suffered almost complete loss of yield in two experiments and more than 90 per cent, of the stems were bored in. two other experiments, in which yields were low. These results and general observations indicate that stem borers, particularly C. ignefusalis, play a major part in limiting yields of late millet.

In six experiments on guineacorn, significantly so in three of them, the yield per bored stem was higher than that per unbored stem, and it appears that borers concentrated on or were concentrated on the larger, higher-yielding stems, possibly as a result of selective oviposition. In one other experiment, stems bored by first-generation larvae yielded significantly less than unbored stems but neither in this nor in any other experiment was over-all borer attack related to a reduction in yield and it is generally true that excellent yields of guineacorn can be obtained in the presence of high populations of borers.

Reduction of the carry over of diapause larvae, by destroying or composting crop residues or removing them from the field, has given good control on the experimental farms at Samaru but it is difficult to extend these measures to local farms. Farmers should clean up their fields before the beginning of the rains and stems that are to be used for building should be exposed in the open during the dry season; to reduce populations of diapause larvae. Insecticidal control has as yet shown little promise and plant breeding for resistance has not begun.

The necessity for further work to confirm the general conclusions drawn here is stressed and possible lines of investigation are indicated.

During recent work on the coconut leaf moth, Agonoxena pyrogramma Meyr., in New Britain, Mr. R. W. Paine has found that this insect, whose larvae live in the leaflets of the coconut palm, is parasitised by a very small Tachinid fly which belongs in the genus Actia R.-D.; this same Tachinid was briefly alluded to as an unidentified dipterous parasite of Agonoxena pyrogramma by O'Connor (1954). The Actia species concerned belongs in the group of species in which the fifth wing-vein (M3 + 4) is setulose, and seemed on first examination to be almost indistinguishable from A. darwini Mall., an Australian species common in Queensland. However, examination of the male genitalia has shown striking differences from A. darwini and it is evident that a new, closely allied, species is involved; this new species is described below. Following the description I have given a key to the Indo-Australasian species of Actia in which the fifth vein is setulose, so that A. painei sp.n. can be placed.

The termites most injurious to crops and trees in West Africa are subterranean or mound-building species of the Termitidae, mainly Macrotermitinae with some Amitermitinae and Nasutitermitinae. Insecticides for their control may be applied generally to the soil, locally around the plant or directly to the colony.

In investigations in Northern Nigeria, dusts containing aldrin or dieldrin were mixed with the top six inches of soil of a type commonly cultivated (a slightly humic, brown, loamy sand), exposed to weathering in the field and tested for persistence of the insecticides by bioassay at intervals, using workers of Trinervitermes ebenerianus Sjöst., a locally common surface-foraging species. The concentration of the insecticide in the soil was measured in terms of the time in days taken for 50 per cent. of the insects to be killed (T50). After 33–34 months, between one-third and one-fifth of the insecticide remained in soil originally treated with 0·5, 2 and 5 lb. active ingredient (a.i.) per acre.

T. ebenerianus proved very sensitive to dieldrin; the T50 value was 1·48–4·10 days for single samples, from each of five colonies, exposed to filter paper containing 0·0018 parts per million, as compared with 10–24 days for the controls. It is suggested that general soil treatments should be used with caution until more is known of their effects on termite populations, which are important in facilitating aeration, and penetration of water, in tropical soils.

Application of dieldrin emulsion, at a dose equivalent to 1 lb. a.i. divided among the planting holes for one acre (1,225), during planting of one-year-old, root-pruned seedlings of Eucalyptus camalduensis, resulted in a mean survival after 2½ years of 60 per cent. of the young trees, as compared with 17 per cent. in untreated controls. Pot-grown seedlings of Eucalyptus spp. were similarly treated at 8 oz. a.i. dieldrin per 700 pots prior to setting out in the field, when they showed very low mortality due to termites over the next 1½ years, attack only occurring where too short a pot allowed access by Macrotermes natalensis (Hav.) to the tap root. Four hundred pot-grown cacao seedlings similarly treated with 4 oz. a.i. dieldrin showed only four deaths due to termites one year after planting out. Pre-treatment of potting soil for Eucalyptus seedlings at 5–10 oz. of 2 per cent, dieldrin dust per cubic yard (sufficient for 500 pots) has given promising preliminary results.

Colonies of M. natalensis, which constructs large mounds, were successfully poisoned with 2½ fl. oz. of aldrin 40 per cent, emulsifiable concentrate in six gallons of water applied through three auger holes made into the central ‘ hive ’, containing the queen cell and associated chambers. It is considered that this dose could safely be reduced.

Many mature larvae of the khapra beetle, Trogoderma granarium Everts, enter a facultative diapause and leave stored food to cluster in crevices in the storage buildings over the whole range of temperature in which larval development occurs (20 to 40°C.). The effects of changing temperature and food conditions on the behaviour of these diapause larvae have been studied in the laboratory.

After an increase from one constant temperature to another, fewer diapause larvae move from the food to the crevices, and those already dormant in crevices tend to emerge, feed and pupate. Some larvae emerge but do not pupate and later return to the crevices. These activities increase with temperature: they are slight at 20 to 25°C., intermediate at 30°C. and great at 35 to 40°C. However, if the temperature is held at 30°C. without change from the hatching of the egg (controls), there is little activity during diapause, although early larval development is fast at 30°C. Large jumps in temperature, e.g., 20 to 30°C., are more effective in breaking diapause than small ones, e.g., 30 to 32·5°C., and changes in the upper part of the range are effective, e.g., 35 to 37·5°C. There is much variation between individual larvae in the time elapsing between the increase in temperature and pupation. Pupation is probably delayed slightly by heavy accumulation of faecal pellets in the food. Sex and the length of the diapause period do not influence the breaking of diapause, which can take place within a month, and probably much less, of the onset of diapause.

Diapause is broken by gradual as well as abrupt temperature increases, but regular daily fluctuations, such as between 25 and 40°C., are ineffective unless preceded by a period of cooling (e.g., 1 month at 20°C.). The renewal of food badly fouled with faecal pellets at 30°C. breaks the diapause of some larvae, but changes in temperature regarded as moderate are more effective.

These results provide additional evidence about the degree of diapause in T. granarium. Some features, including the breaking of diapause by cooling followed by a return to a favourable temperature, are typical of classical diapause, but the breaking of diapause soon after it begins and the effect of a jump in temperature in the upper half of the developmental range without prior cooling are not typical, suggesting that diapause is broken by a trigger effect starting or stopping some physiological process. It can be concluded that mature, dormant larvae of T. granarium undergo a fairly weak facultative diapause with some unusual features before becoming prepupae. This diapause is compared with that of other insects.

The diapause appears to be particularly suited to the environment in dry food stores. It helps larvae to survive cool periods and food shortage, until warming combined with loading of new food breaks the diapause and allows breeding at the beginning of favourable periods. It appears likely that in grain stores in the Punjab (Pakistan) the life-cycle of T. granarium is largely governed by the climatic seasons. In the very erratic, non-seasonal environment in British malt stores, the ease of breaking diapause at almost any time after it has begun, with or without cooling, enables T. granarium to breed as soon as conditions are favourable, without seasonal control. Some other features of the diapause are well suited to this environment.