Examination of Newstead's specimen has confirmed the substantial accuracy of his description and drawings, with the exception of the genital pump. The form of the aedeagus alone leaves no possibility of confusion with P. perniciosus, of which there has been available an adequate series of Italian specimens for comparison. The view of Adler and associates that the sixth spines are aberrant is thoroughly reasonable. P. mascittii is therefore an easily recognizable species, as to the male, from existing descriptions and drawings, and represented by the sole known cotype in the British Museum, which is hereby designated the lectotype.

The question of the distinguishing characters of the female is bound up with the whole matter of the identity of P. mascittii and P. larroussei. The evidence already published, involving both males and females, certainly constitutes a strong case for the identity of these two species. There may be cited: (a) the character of the wing venation which seems to be constant in both sexes; (b) the general agreement as to the male genitalia; (c) the fact that one of Saccà's specimens was caught within a few hundred metres of the type locality and the others in the same city. In the absence of any contrary evidence there is no reason to doubt the soundness of the view shared by Saccà and Parrot that these two species are identical.

A method is described for studying the life-cycle of Melophagus ovinus. The female ked matures in 6 to 7 days and the male in 10 to 11 days. Copulation takes place 16 hours after emergence and the first pupa is deposited by the female about 13 days after its emergence. The second and successive pupae are deposited at intervals of seven to eight days. The pupal stage covers 20 to 26 days (an average of 22·5 days for 28 observations). The life-cycle is completed in 33–36 days. Experimental conditions did not affect the duration of the various stages observed in the life-cycle.

An investigation of the periodic fluctuations in the infestation of a flock of Welsh sheep showed that the degree of infestation is influenced by the transference of keds between the sheep. Before lambing, keds are transferred from hoggs to two- to three-year old ewes and, after lambing, from ewes to lambs. The peak infestation of ewes and hoggs occurs before lambing. The maximum infestation of lambs occurs before shearing. At shearing the majority of adult keds and pupae are removed with the fleece. Adults surviving after shearing are killed at dipping. Depending on the nature of the dip, re-infestation results from pupae hatching in fleece or by the transference of keds from infested sheep coming into contact with the dipped flock. Keds disappear from the fleece through being devoured by the sheep, by the activity of insectivorous birds and through natural death. The transference of keds between sheep is achieved through contact and occurs readily when the ked is on the surface of the fleece. The vertical migration of the insect in the fleece is controlled by temperature and is not influenced by light.

The distribution of pupal and adult stages of M. ovinus in the fleece of lambs, hoggs and ewes is given. The position of attachment to the pupae is controlled by the depth of the fleece, deposition occurring on the wool fibres at a point where the temperature is suitable for their development. The age of the sheep influences the distribution of the ked, young sheep being more susceptible than older animals. In a flock, the higher infestation of hoggs compared to older ewes may be due to the higher initial infestation of the hoggs after dipping. Open fleeced sheep are more susceptible to ked infestation than tight fleeced sheep.

A campaign to control the weed, Cordia macrostachya (Jacq.) Roem. & Schult. (Boraginaceae) by biological means is in progress in Mauritius (Williams, 1948). This hardy perennial shrub was accidentally introduced from Central America in the last decade of the nineteenth century. It is today a serious pest of nearly all land of agricultural value which is not intensively cultivated (Wiehe, 1946).

Bis(bis dimethylamino phosphonous)anhydride is shown to be a systemic insecticide when sprayed on the leaves of numerous plants. The translation of it from one part of the plant to another, over distances varying from the thickness of a leaf to three feet, was shown with Aphis fabae, Myzus persicae, Brevicoryne brassicae, Macrosiphoniella sanborni and Pseudococcus citri.

Plants treated with it are shown to be toxic to 14 Aphid species, one Aleurodid, one mealy-bug, two Jassids and two species of red spider.

It is not found to be toxic to non-plant-sucking insects, notably predators and parasites. It is, therefore, a selective insecticide for the control of Aphids, and field experiments have shown that treatment with it gives plants prolonged toxicity to Aphids and allows the parasites and predators to keep in check any survivors or newly arrived individuals.

Non-selective organic phosphorus insecticides such as Parathion, Paraoxon and HETP give a high mortality, but the Aphid population builds up again very rapidly after treatment with them, leading, in many cases, to a heavier infestation than before.

Plants treated with bis(bis dimethylamino phosphonous)anhydride, on the other hand, keep free from Aphids for prolonged periods (2 to 5 weeks depending on the species of Aphid, the stage of growth of the plant and its physiological condition).

The spreading of larvicidal oils is hindered by the presence of natural films upon the surface of standing water. The film pressure, which measures the resistance offered to the spreading of oil, can be determined in the field by a simple method depending on the use of standard spreading liquids.

It seemed reasonable to suppose that by making tests on the waters at many different places it should be possible to estimate the optimum spreading properties required in a larvicidal oil before its distribution began in a particular district. An attempt to do this was made in a part of the Gold Coast in 1944 and the investigation showed that in that region, and at that time, the spreadability of an oil with spreading pressure equal to 30 dynes/cm., approximately, would have been adequate for larvicidal purposes. It was also found that the natural films, which could be either visible or invisible, were of two physical types distinguishable as “uniform” and “non-uniform” according to the observed variation of the film pressure at a single site.

Railway trains running through tsetse-infested country between Mombasa and Nairobi in Kenya Colony carry G. longipennis, G. pcdlidipes and G. brevipalpis on to stock-farming areas beyond the natural limit of the fly belt, thus being largely responsible for outbreaks of animal trypanosomiasis and a reluctance on the part of European, Asian and African settlers to develop the land, affected by this form of fly dispersal, to its full capacity.

The country through which the trains travel is described together with an account of a survey of the fly distribution.

Tabulated figures are given of the monthly totals of tsetses collected from passenger and goods trains by teams of fly boys posted at Emali and Sultan Hamud railway stations about 17 and 25 miles respectively outside the fly belt towards Nairobi More than 24,000 flies were collected over a period of one year and many, not collected by the de-flying teams, were carried up-country even as far as Nairobi, 101 miles from the fly belt.

Tsetses were collected from inside passenger trains, but very much larger numberswere taken from the outer surfaces and undercarriages of goods trucks.

Reference is also made to the rôle of motor traffic, especially when in convoy in the dispersal of tsetses.

The incidence of animal trypanosomiasis along the line of the railway is dealt with and the association of the disease with tsetses carried by trains is supported by results of laboratory experiments on the transmissibility of Trypanosoma congolense, T. vivax and T. brucei by the three species of flies concerned.

Bush-clearing on stock farms outside the fly belt will not protect the cattle from infection carried by flies brought by trains but bush-clearing in specified localities of fly concentration in the infested country is recommended as a measure to reduce the numbers now attracted to trains. It is considered that the spraying of trains will bring considerable relief to farmers ; but, so far, no suitable spraying apparatus has been devised nor has a reasonably cheap insecticide been found for this purpose.

The depth and habits of pupation, shown by the three main species of sheep blowflies (Lucilia sericata, Chrysomyia chloropyga, and C. albiceps) are discussed in relation to parasitism by the Pteromalid, Mormoniella vitripennis.

Experimental series showed that the majority of Lucilia larvae pupate in situations which are inaccessible to the parasite, a result which agrees with field observations; whereas the two species of Chrysomyia have a large proportion of their pupal populations exposed freely to attack by the parasite. The degree of protection thus sought by the larvae appears to be directly proportional to the suitability of the puparia of the species as hosts for the parasite.

Because of this difference in pupation habits, a large proportion of the Lucilia population which survives the competition for food and the predatory attacks of C. albiceps on the carrion will produce adult flies; whereas the more exposed C. albiceps and C. chloropyga populations will be further reduced and in a proportionate manner by parasitism. This explanation is put forward as one of the main reasons for the comparative success shown by field populations of Lucilia and the unexpectedly small field populations observed in the case of C. albiceps.

It is pointed out that this phenomenon is a disadvantage where natural control of the primary flies is concerned since C. albiceps is an important controlling factor in larval populations of Lucilia.

The objects of the investigation were to describe the process of maturation of the ovaries, to clear up the question of the relation between copulation and sexual maturity, and to determine whether any relation exists between weight and sexual maturity.

The locusts used were of the transiens phase. They were kept at temperatures between 32°C. and 37°C. and relative humidities between 50 per cent, and 70 per cent.

The maturation of the ovaries was followed, and is divided into four stages distinguished chiefly by the sizes of the eggs.

It is shown that the average number of ovarioles per female does not change significantly with age.

The numbers of ovarioles in the two ovaries of an individual often shows asymmetry, which probably increases with age.

Some of the ovarioles are small. The percentage small ovarioles increases with development of the eggs. Variation between individuals in the total number of ovarioles also increases with age.

The number of egg rudiments per ovariole was calculated for different ages and stages. The differences were not significant. It is concluded that new rudiments are produced during the oviposition period.

It was found that when the food supply was relatively short, female locusts became mature and oviposited if allowed to pair, but did not mature if males were not present. With abundant food, unmated females matured, but more slowly than mated ones and fecundity was reduced. It is concluded that under unfavourable conditions pairing may be necessary for maturation of the ovaries.

Average weights of female locusts in each of the four stages were compared. Locusts in stages III and IV, i.e., those which are mature, were found to be significantly heavier than those in stages I and II. The average weight of a number of stage I locusts 13–18 days old (whose development had been retarded by unsuitable conditions) was also found to be significantly less than that of a number of stage III locusts of the same age. It is concluded that weight depends primarily on the development of the ovaries.

The relation between weight and age was investigated. Rate of increase of weight is rapid at first, is reduced for about two days, then increases again and maintains its value until the weight is about 2 gms. During the oviposition period it fluctuates irregularly.

It is shown that if conditions are unfavourable to maturation the weight rises to a certain value, after which it remains constant, or falls. The fall was best seen in stage II locusts over 14 days old.

There is little relation between weight and egg-size in stages I and II, but in stages III and IV the relation is closer. Rate of increase of weight with egg-size is at first low, but above an egg-length of about 4·5 mm. the rate of increase of weight becomes greater. It is suggested that this is because early growth of the eggs is due to transference of fat from the fat body and later stages to the laying down in the eggs of substances derived directly from the food.

Estimates were made of water and fat content of locusts of various ages. Percentage water falls rather rapidly in the first few days of adult life after which it remains approximately constant. Percentage fat rises to a maximum at about 14 days, then falls slowly. Most of the increase in weight during maturation is due to water intake.