A historical account of the Ox Warble Flies, Hypoderma lineatum and H. bovis, is given and the economic importance of the two species is discussed. Certain aspects of their biology and control have been studied over a period of several years in South Wales culminating in intensive investigations in the years 1945 and 1946.

The adults of H. lineatum emerge from their puparia in early May and those of H. bovis a month later. The adults of both species in their persistent endeavours to oviposit, worry cattle, whenever the weather is sunny and calm, from the end of May to early September but they tend to avoid the vicinity of water and shade.

The degree of incidence is high in Britain, at least in South Wales, judging by the larval populations present in the backs of cattle. Over 80 per cent. of the cattle included in the surveys conducted in 1945 and 1946 harboured infestations of varying intensity; in one case 152 larvae were recorded on a Shorthorn heifer.

The larvae spend, on an average basis, 42·5 days in the subcutaneous tissues of the backs of their hosts. They begin to depart in order to pupate much earlier than is normally assumed to be the case in Britain, more particularly in Worcestershire, where the proportion of larvae pupating prior to March 28th was as low as 1·4 per cent. compared with over 20 per cent. in the present studies.

The marked variations commonly observed in the seasonal incidence of the larvae in their final instars on cattle are correlated with the relative prevalence of the two species in different districts.

The incidence of both species, judging by the intensity of infestations, is associated with the topographical conditions of the locality. For instance, herds on upland pastures are generally less liable to severe attacks than those on lowland farms.

Cattle under three years old normally carry much heavier infestations of the larvae of both species than those exceeding this age when kept under identical conditions during the oviposition period.

Diphenyl-dichloro-trichlorethane and benzene hexachloride preparations are ineffective for destroying the larvae, at least in their final instars, but emulsions of the former insecticide when applied in the form of a spray to the legs and flanks of cattle during the period of oviposition proved highly promising and warrant further investigations.

The variations in susceptibility of different varieties of peas to attack by the Pea Moth was investigated and an attempt made to determine and measure the factors concerned. Six varieties of peas differing widely in haulm length and earliness of maturation were used in each of two trials. In the first trial (sown 29th March) the early maturing varieties came into flower before the moths were recorded on the crops and suffered the lowest attacks. The later varieties were exposed to attack over a much longer period and suffered the heaviest infestations. In the second trial (sown 3rd May) the attack was more uniform over all varieties with the early varieties more heavily affected than in the first trial; they were exposed to attack from the beginning of flowering until harvesting.

An estimate of the changes in the active moth population during the flight period was obtained and the varieties were compared in relation to the proportion of this population to which each had been exposed. There was a strong positive correlation between the degree of exposure and the incidence of attack on the different varieties.

The infestation of the varieties was also found to be influenced by the amount of cover which each provided; those with the most dense cover suffered the heaviest attacks.

Statistical analyses showed that the two factors, exposure and plant cover, were closely associated and exerted a joint influence on subsequent attack.

Data from other trials corroborated these findings and showed that strains of peas bred to mature early suffered substantially lower pea moth attack than did the later maturing types from which these had been bred.

An account is given of the life-history of Auchmeromyia luteola in a laboratory culture maintained in London for two-and-a-half years. Attention was centred on the bloodsucking larva, known as the Congo Floor Maggot, which is an intermittent ectoparasite specific to man. It was reared chiefly on the natural host, but a strain has been maintained on shorn guinea-pigs through several generations. It was also found possible to rear the larva on free blood.

The known distribution of A. luteola is reviewed on the basis of published records, museum collections and information from scientists in Africa. The species is highly successful in both the wettest and the driest parts of the Ethiopian region, but does not seem to extend south of Durban. It can flourish only where man occupies permanent settlements and makes his bed on the floor within reach of the maggot. Strains originating in Nyasaland, in the western part of the Belgian Congo, and in the Anglo-Egyptian Sudan were successfully cross-mated and produced fertile eggs. The second generation from these crosses, however, was not always fully fertile.

The method of cultivation of the material is described.

Batches of eggs hatched 36–60 hours after oviposition when kept at 26–28°C. and 50–50 per cent. R.H. In drier atmosphere development was delayed and took from 3 to 7 days at 23°C. and 10 per cent. R.H.

The habits of the larvae are discussed and it is shown that larvae took 20 minutes to gorge (although newly hatched specimens often stopped feeding after 10 minutes). Given the opportunity, a meal was taken daily except for a day missed before each moult. No larva could be induced to bite twice in one day unless the first feed had been interrupted.

The rate of growth of the larvae was found to be strongly influenced by the feeding schedule, those receiving. 4 meals a week having a much higher rate than those receiving only 2. There was also a correlation between rate of growth and temperature but the correlation with relative humidity was less well marked. After fasts of several days, meals of the order of two and a half times their own weight were taken by larvae of all three instars.

Larvae which were fed four times a week and kept at 23°C., besides growing faster than others fed at less frequent intervals, reached higher maximum and pupal weights and started to pupate on the 26th day. Larvae fed at less frequent intervals took larger meals but lighter pupae and flies were produced.

The time of moulting appeared to be directly related to weight and only through this to the environment. The first moult occurred after the larva had gorged to a weight of 1·5–2·1 mg. (usually at the 2nd or 3rd meal), the second moult after it had reached 12–19 mg. (at the 4th to 7th meal).

There are wide limits of weight between which the onset of pupation can occur, the upper limit being higher for female than male larvae. If the feeding schedule (in relation to climate) is favourable, the larvae reach a maximum weight which induces the onset of pupation regardless of other factors. If the meals are scarce, growth is retarded more than metabolism and time becomes the limiting factor; then, the scarcer the meals, the smaller, not the later, the pupae. If the meal schedule is so adverse that the larvae cannot reach the minimum weight for pupation (about 97·5 mg.) in the time set by their metabolic rate in the given climate, death ensues without pupation.

No larva has been known to complete an instar on a single meal. The minimum for complete development in any climate is probably six meals, two in each stage. Larvae reared at 28·5°C. in 60 per cent. R.H. on five meals a week, moulted after the rd and 7th meals and pupated after the 16th or 17th.

Failure to moult, followed by death, occurred in all strains in the laboratory. It is believed that this is sometimes due to overcrowding and sometimes to the larva being disturbed when ready to moult. Inability to moult was commonest in the dry atmospheres and among larvae fed only twice a week.

Saturated air was fatal to the larva but not to the pupa. The species tolerates a wider range of atmospheric humidity than most insects, and was even reared successfully in an atmosphere of 10 per cent. R.H.

Female larvae in the third instar take more blood than males and lose more by excretion ; they also grow larger and produce heavier pupae and adults.

The temperature lethal in one hour to larvae having completed the second moult is denned within about one degree (42·5–43·5°C.) and does not appear to vary according to atmospheric humidity.

The Floor Maggot can survive fasts perhaps longer than any other Dipterous larva. At 28·5°C. and 90 per cent. R.H. survival of first-instar larvae, unfed, after one meal and after two meals, was 9–20, 8–21 and 4–21 days respectively ; third-instar larvae after moult (i.e. at 12·19 mg.), and at about 90 mg. survived 17–18 and 28–47 days respectively. At the same temperature but 10 per cent. R.H. much more weight was lost and the survival time was much less. At 23°C. newly hatched unfed larvae survived 5–37 days at 60 per cent. R.H. and 9–22 days at 10 per cent. R.H., while third-stage larvae survived 25–48 days at 90 per cent R.H. and 9–19 days at 30 per cent. R.H. Newly hatched larvae lived for 3–8 days at 35°C. in 60 per cent. R.H.

The pupal stage lasts about 9 days at 34°C., 11 days at 28·5°C. and 15–16 days at 23°C. and is unrelated to atmospheric humidity. Losses in weight at different atmospheric humidities were studied; the proportion lost was about 16 per cent, at 90 per cent. R.H. and about 25 per cent, at 10 per cent. R.H.

The habits of the adult flies are discussed ; human faeces appear to be the staple diet. The male seeks the female persistently and mating is protracted and occurs repeatedly. One male can fertilise several females. Oviposition and development continue all the year round without diapause. In the laboratory at 22–23°C. a female normally laid about 54 eggs at her first oviposition, and in one case a female laid as many as 6 batches of fertile eggs. In warm weather, the first batch was laid about 16 days after emergence (or after 20–23 days at 23°C), smaller batches being laid subsequently at intervals of 5–8 days. The female lived in the laboratory up to 93 days and the male up to 85 days.

The life-cycle under natural conditions is roughly estimated as 10 weeks, so that five generations a year might be expected.

Female ticks are almost entirely confined to head, axillary and inguinal regions of cattle. Larval and nymphal stages attach on the head and below the hock joints on the fore- and hind-legs.

The percentage of females on the forequarters of cattle increases during the course of the season, whether in spring or autumn; during the early stages of a season's activity the hindquarters carry a greater number than the forequarters. Later in the season the position is reversed. Suggestions are put forward to account for this phenomenon.

The head, axillary and inguinal regions are the major attachment sites of the female tick on sheep. In ewes the head region carries the higher percentage, but on lambs the axillary region is the most heavily infested. This difference may be due, to some extent, to the fleece of the ewes forming a barrier to the movement of unfed ticks towards the axillary and inguinal regions.

Lambs carry a heavier infestation between the 21st April and 6th June than ewes on the same grazing. This phenomenon has been discussed in the light of previous work in Northern England.

There is no reliable method of estimating the total infestation on cattle. A good picture of the seasonal incidence of the female tick on the host can be obtained from the hindquarters count. The standard count (the forebody) on sheep may be used for estimating total infestations.

The entomology of swollen shoot of cacao is a complex and unique problem involving the inter-relations in the field of over 120 insect species of four insect and two arachnoid orders. Briefly, there are 17 species of pseudococcids, 75 species of ants, 16 species of hymenopterous parasites, three predatory beetles, one predatory dipteran, and three arachnid species involved in vector relationships directly, with a further 18 Coccid species involved indirectly (it is possible, of course, that further work will show that some of these 18 species are directly concerned as vectors).

In the present paper an attempt has been made to reduce this assemblage of insect material to some semblance of order. The Coccid species are named and a series of preliminary observations on their biology and field behaviour detailed. The ant species, some of which are obligatorily associated with certain vector species, have been sorted into groups where specific determination has proved impossible or unnecessary and information has been included on their field habits and relative abundance.

There are three distinct but complementary ecological niches involved in the problem. The first, and most important, is the association between the mealybug virus vectors and the Myrmicine coccid-tending ants. The second is the association between mealybugs of the genera Paraputo and Formicococcus and the wild forest tree hosts of swollen shoot virus, and the third is the negative association between the mealybug tending Myrmicine ants and Oecophylla and Macromischoides, the latter species acting in certain circumstances as barriers to the spread of the mealybugtending species and hence to the spread of mealybugs and virus. These problems will be dealt with on a quantitative basis in a further paper.

Endrosis lactella is widely distributed in Britain, where it is a minor pest of stored products, especially of grain and seeds.

The incubation period of the egg varied between 42 days at 10°C. and 6·0 days at 26°C. It was almost unaffected by changes in relative humidity.

Survival of eggs was low at high temperatures and low humidites, and the mean survival from complete batches of eggs at 70 per cent. R.H. 25°C. was 44 per cent. The highest survival recorded was 81 per cent.

On a diet of middlings the larval stage lasted 133 days at 90 per cent. R.H. 10°C, and 38 days at 90 per cent. R.H. 25°C. No adults were reared from larvae grown below 80 per cent. R.H. At 90 per cent. R.H. and 25°C. there were 7 instars.

On various foodstuffs at 90 per cent. R.H. 20°C, duration of the larval stage varied between 40 days on dead moths and 109 days on macaroni. Survival to the adult stage varied between 75 per cent. on whole wheat and 20 per cent. on groundnuts.

The pupal incubation period was 58 days at 10°C. and 10·4 days at 25°C, and was approximately the same at all humidities.

The time required for complete development from egg to adult was 235 davs at 10°C. and 62 days at 25°C. (90 per cent. R.H.).

There was a significant correlation between the weight of a female moth at emergence and the number of eggs laid. Egg output was lower at 25°C. than at 15°C, was not significantly affected by relative humidity, but was increased by provision of drinking water. Weights of females varied from 2·9 mg. to 9·4 mg. and egg output from 14 eggs to 231 eggs.

The sex ratio of the adults in the dried grass culture was found to be 1 male to 23 females.

Longevity could not be correlated with weight in all experiments, but, in the case of mated females, was dependent upon temperature, humidity and availability of drinking water. The mean adult life in days was 3–0 at 30 per cent. R.H. 25°C.; 5·0 at 90 per cent. R.H. 25°C.; 9·1 at 90 per cent. R.H. 15°C.; and 8.9 at 70 per cent. R.H. 25°C. + drink. Mated males were very short-lived (2–4 days at 70 per cent. R.H. 25°C).

The only important predator was the mite, Cheyletus eruditus, which attacked the young larvae.

Three interconnecting cages, the largest of which was about 2 feet square, were used in experiments with Anopheles vagus bred from wild-caught larvae.

Variations in the arrangement of these cages showed that:

1. The mosquitos are quiescent by day, if not disturbed, whether kept in the light or in darkness.

2. If they are in complete darkness by night, as in a photographic darkroom, they fly vertically upwards. They will readily escape from a cage about one foot square, with a hold half an inch in diameter in the top, in their continued attempts to fly upwards.

3. They are attracted by a dim light at night and will fly sideways or to a lesser extent slightly downwards, in opposition to the tendency to vertical upward flight. In this way they can pass through openings which they would miss if in complete darkness. Light will not cause them to fly vertically downwards.

4. Anopheles maculatus is less responsive to light under these conditions, than A. vagus.

Using A. vagus, tests were made of the toxicity and residual effect of DDT, BHC and Chlordane as wettable powders on plywood panels. The order of toxicity when fresh was found to be BHC, Chlordane, DDT; the order of the residual effectiveness was DDT, BHC, Chlordane.

A considerable mortality occurred amongst mosquitos surviving the overnight tests with DDT and BHC, if they were kept for a further 48 housrs.

A larger proportion of females was killed than of males, especially by DDT and Chlordane.

BHC was shown to have a marked repellent effect, comparable with that of citronella, but whereas citronella repelled without killing, BHC repelled, but also caused a high subsequent mortality.

A. maculatus was tested once against DDT, and once against BHC in the main series of tests, and was much more readily killed than A. vagus, presumably because of its weaker response to light causing it to remain longer in the main cage in contact with the treated panels.