A full description is given of the life-history of Exenterus abruptorius, Thb., an important parasite of the pine sawfly, Diprion sertifer, Geoff.

The insect is univoltine, like the host. It oviposits on the last stage larva or prepupa and only hatches after the host has spun its cocoon. Only one-quarter of the primary larvae develop immediately, the remainder resting up to two and a-half months during the summer before proceeding with their development. On the completion of feeding the parasite larva spins its cocoon within the host cocoon and enters the prepupal stage, which can be divided into two distinct phases, eonymphal and pronymphal. Hibernation is always in the eonymphal stage. In Sweden 37 per cent. of this species remained in hibernation for two winters, but in Hungary all emerged in the spring following the year of development. Further than this, in Sweden the sexes were in approximately equal proportions; in Hungary females exceeded males by four to one. This may indicate the existence of biological races.

Other Ichneumonidae exhibit the prepupal stage, with eonymphal and pronymphal phases, in their development. The typical facies of this is analogous to that in the prepupal stage in Tenthredinidae, in which, however, ecdysis precedes this stage, which is then a distinct instar. It is suggested that an instar is lost in the development of the Ichneumonidae, though the facies of the prepupal stage is retained.

Pin-hole borer damage to timber, caused by beetles of the families Scolytidae and Platypodidae, is associated chiefly with recently felled logs and occasionally with standing trees which are in an unhealthy condition. Information collected within recent years by the Forest Products Research Laboratory, Department of Scientific and Industrial Research, suggests that attack in standing trees may, however, be of more frequent occurrence than has been commonly supposed. In this connection, an interesting case of damage to English ash by the Platypodid beetle, Platypus cylindrus, F., is worthy of record.

Echthromorpha tirathabae, sp. n.

This species belongs to Group D of Krieger's monograph of this genus (Mitt. zool. Mus. Berlin, 4, 1909, p. 341).

A severe outbreak of the Spruce Sawfly (Diprion polytomum, Htg.) in Eastern Canada led to a request to Farnham House Laboratory to investigate, and if possible collect and export, the parasites of this insect in its native home in Europe.

Work started in 1932 and it was found that D. polytomum was a comparatively rare insect in Europe, though widely distributed. It is heavily parasitized, 31 species of Hymenopterous and Dipterous parasites having been found up to the present. Nearly twenty-eight million parasitized cocoons and eggs of this and other species of Diprion have been collected and despatched from Europe, and work is still continuing.

Previous to the present work only 13 species of parasites, a list of which is given, were recorded from this host.

Of the 31 species now known, 15 are primary, 5 can be primary or secondary, and 9 secondary only; in 2 cases the status is not known.

Descriptions of all the species are given and in the case of the obligatory and facultative primaries, the biology and immature stages are also described and notes added on their suitability for introduction into Canada. A key to the adult parasites is given, and a key to the larval stages of the primary and facultative primary parasites. Some practical notes are also given, including methods of accelerating the emergence of parasites in winter and methods of preparing parasite larvae for examination and identification.

In 1927, 1931 and 1935, the writer published three papers on the food-plants of Nigerian insects in this Bulletin (18, pt. 1 ; 22, pt. 2 ; and 26, pt. 2). The present paper contains additional data obtained between November, 1934, and March, 1936. On the advice of the Botanical Section, Nigerian Agricultural Department, certain changes have been made in the nomenclature of economic plants. In the previous papers the nomenclature employed in the Kew Bulletin entitled “ The Useful Plants of Nigeria ” was adopted. The following list shows the English or native name of the crop and the old and new scientific names.

An investigation of the “ fly-belts ” in the Ol Orokuti area of the Masai Reserve was carried out early in April 1934, in response to a request from the European farmers of the Sotik district.

The Capsid described in the present paper came under observation in Malaya some years ago but was not then specifically determined. Mr. W. E. China, of the British Museum (Natural History), was kind enough recently to examine it, and came to the conclusion that a new genus should be erected to contain it. Specimens were returned to me by Sir Guy Marshall, Director of the Imperial Institute of Entomology, along with some notes made by Mr. China which would be of use in the preparation of the diagnosis of the new genus.

1. Temperature does not affect wing development in Aphids.

2. A great percentage of Aphids developed wings when they were crowded, or when they were forced to feed on stale or wilted food. This was due to the small amount of food and particularly of water which each individual Aphid obtained.

3. A reduced percentage of water in the food of Aphids, as well as a low atmospheric humidity, are primary factors causing wing development.

4. All the factors such as light, temperature, crowding, humidity, precipitation, growth of plant, etc., exert, directly or indirectly, an influence on the water balance in the body of the Aphid, which in turn causes wing development.

Phyllocoptes lycopersici, Massee, sp. n.

Tryon, Rept. Queensland Agric. Dept. 1916–17, pp. 49–63. (No description.)

Body spindle-shaped, stout, tapering sharply towards anal end. Thoracic shield triangular, sides sinuate, apex produced and rounded, not completely covering rostrum. Centre of shield smooth, sides ornamented with two longitudinal furrows at end near lateral margins. Shield 44 μ long.

Sheep scab has existed from early times. It was known to the ancient Greeks and Romans ; it was familiar to the Hebrews ; and writers on agriculture in the Middle Ages were acquainted with its ravages, and suggested means of preventing and curing it. Laws to control the disease were introduced in Britain at the beginning of the eleventh century, and subsequently other countries also adopted legislative measures against it. Regulations have been renewed and amended from time to time to conform with the progress made in the studies of the disease and its cause. The strictness with which they are applied vary in accordance with the economic importance of the sheep industry in any particular country, and their success as preventive measures is dependent upon their stringency and upon the co-operative support given to them by all sheep-owners.

A number of species of this genus of Encyrtid parasites are known to be, and others are suspected to be, secondary parasites ; but apparently the complete life-history has not been observed in any one case. As the genus has an almost world-wide distribution and is doubtless of considerable economic importance, the following observations made in Southern California in part of 1935 and 1936 are recorded.

1. Male G. swynnertoni were placed in a cage in the middle of a grass enclosure (to curtail their sight) and their powers of smell tested by recording their reactions when a span of six oxen (with two men) passed to windward outside the enclosure. Reactions were obtained at the ranges of 110 and 180 ft. but failed at 300 ft.

Female G. swynnertoni reacted at 110 ft. but were not tested at greater ranges.

2. Men in groups of two and eight were substituted for the oxen, and human scent was found to be attractive, but in spite of this there was evidence that the oxen and not the men with them were the main attraction in the scent experiments with the oxen.

3. The scents of kamba (onion-scented bark rope), hessian and manure were tested at 110 ft. and were not attractive. There was evidence, however, that the exhaust of a lorry at 300 ft. was attractive.

4. The tsetses did not react to shouting, the trampling of oxen or the noise of a lorry.

5. These results are discussed and the experimental conditions compared with the conditions in the natural environment.

6. Wind of a strength from 1½ to 5½ m.p.h. outside the cage (i.e., from about ¾ to 2½ within it) successfully bore the scent of the oxen at a range of 110 ft. to the tsetses. Lower and higher velocities were not tested.

7. The powers of sight of male G. swynnertoni were tested by passing the span of oxen to leeward of the enclosure, from the circumference of which an arc had been cut. The direction of the wind ensured that the tsetses could receive no scent. A maximum tonal contrast was obtained (to human eyes) by using black oxen against a light background and carrying out the experiments in bright sunshine. Positive results were obtained up to and including a range of 450 ft., but at 600 ft. there was no reaction.

Female G. swynnertoni reacted at 110 ft. but were not tested at greater ranges.

8. There was evidence that as the tonal contrast between the oxen and their background became less (through a weak sun or the background in semi-shadow) so the distance at which the tsetses could see diminished. This was supported by an experiment at 110 ft. in which the effect of a dark-blue background was greatly to reduce the reactions.

9. A small dark screen at 110 ft. gave as good reactions as the span of oxen.

10. The results of the sight experiments are discussed and the experimental conditions compared with those in the natural environment.

1. The main food hosts of Glossina swynnertoni in a district of Tanganyika appear to be (a) one or more Bovids, perhaps kudu or roan, exhibiting a close blood relationship to ox or buffalo ; (b) giraffe ; (c) pig. There is evidence that monkey or baboon is also made use of and that zebra definitely is not.

2. With regard to G. palpalis on Maboko Island, crocodile and hippopotamus are important hosts. But they are far less important than we had supposed. The majority of flies appear to have fed on some animal not yet determined.

1. The object of the investigation is the study of possible methods of control of injurious insects in pine areas in Britain, with special reference to bark-beetles and to Myelophilus piniperda, L., in particular.

2. Reference is made to the economic status of the pine beetles in Britain as compared with other countries, and it is pointed out that in this country control measures must be of a more intensive character than in countries where large tracts of natural forest occur.

3. An analysis of the various types of damage caused by Myelophilus is made, and it is shown that although the actual amount of damage caused in any particular year may at the time appear comparatively slight, the effects of successive outbreaks are cumulative, and frequently result in a great reduction in the value of the crop.

4. The occurrence of bark-beetle outbreaks and the conditions under which they occur are briefly described.

5. The factors influencing the pine beetle population are discussed, and it is pointed out that the effects of climatic and physical conditions on the development of the host-plant under forest conditions are of fundamental importance in determining the density of the bark-beetle population in standing pine woods. It is stated that apart from abnormal increase brought about by exceptional breeding facilities as a result of fire, windfall, and felling operations, the conditions favouring the increase of bark-beetles and wood-boring insects in pine forests are considered to be mainly due to exceptionally favourable conditions for vigorous growth during the early stages of the crop's development, resulting in large numbers of trees being suppressed and killed in the pole stage, by rapidly increased shade as a result of the abnormal development of predominant trees. This is inevitable when Scots pine plantations are formed on soils too rich and situations too favourable. On the other hand, exceptionally favourable conditions for bark-beetle development occur when conditions are unfavourable for the healthy development of the crop owing to bad drainage conditions and water-logging of the soil.

6. The effect of overcrowding among the brood is considered to be one of the most important factors in the limitation of the bark-beetle population. Examples of how this factor operates are given and it is shown that the practical application of this factor can be brought about by the limitation of the supply of suitable breeding material.

7. The relative value of various parasites and predators as factors in the control of bark-beetles is discussed.

It is considered that pathogenic organisms are of little importance in the control of bark-beetles, as although these organisms may cause an epidemic when the pest has reached its maximum abundance, the object of our control measures must always be to prevent the bark-beetle population from approaching that stage of density.

Evidence is cited from the literature as to the effects of Nematode worms in reducing the egg-laying capacity of bark-beetles. It is suggested that the difference in the results obtained by various writers may have been influenced by the state of the insects at the time the observations were made, since the state of development of the reproductive organs of bark-beetles varies considerably during different stages, and although they sometimes appear to be shrivelled, they are capable of recuperation after a period of feeding. In any case it is impracticable to utilise Nematode worms in control measures, and it seems probable that their usefulness as parasites of bark-beetles will be neutralised by their effects upon the Coleopterous predators.

A list of the Hymenopterous parasites of pine beetles found during the progress of the investigation is given, together with notes on their relative abundance, and their importance as controlling factors is emphasized.

A list of the Coleopterous predators found associated with the bark-beetles is given with notes on the most important species. It is pointed out that some species of Coleopterous predators are probably more injurious than beneficial owing to the destruction of parasite larvae ; Thanasimus formicarius and Elaterid larvae are examples. On the whole, the Coleopterous predators are considered to be of even greater importance than Hymenopterous parasites as agents in the control of bark-beetles.

The larvae of several species of Diptera are very numerous in the bark-beetle brood-galleries. A list is given of the species which have been identified. Although listed as predators of bark-beetles, these Diptera are regarded as being of greater importance as destroyers of parasite larvae and are therefore being studied with a view to their possible elimination.

The economic status of birds in relation to bark-beetle control is briefly discussed, and it is pointed out that although under certain conditions birds do undoubtedly destroy large numbers of adult bark-beetles, it is probable that this useful work is counterbalanced by the destruction of parasite larvae in winter. On the whole, birds are not regarded as being of importance in the control of pine beetles in Britain.

The effects of competition between different species of bark-beetles is discussed, with special reference to Crypturgus cinereus, Hbst., and its influence in the control of Myelophilus minor.

8. A detailed description is given of some large-scale thinning experiments which have been in progress in the New Forest since 1933.

The scheme on which the experiments are based is the result of observations carried out by the writer over a period of years during which he noted that parasites and predators of the pine beetles are most numerous in young pine stands in the pole stage, previous to the first thinning operations. The conviction was formed that under those conditions a state of biological control existed which might, under favourable conditions, be continued throughout the rotation of the crop. One of the necessary conditions for the maintenance of a permanent resident population of parasites and predators is the presence of a permanent host population. This, in turn, necessitates a continuous supply of suitable breeding material. The density of the host population is largely governed by the quantity of suitable breeding material available, and the requirements of an increasing bark-beetle population demand a corresponding increase in the amount of suitable breeding material from year to year; so long as this increase in suitable breeding material continues, the host population is maintained at a higher level than that of the parasites and predators. When, however, the supply of suitable breeding material ceases to meet the requirements of the increasing bark-beetle population, a point is reached where overcrowding of the brood takes place. The intersection and intermingling of the larval tunnels facilitates the work of destruction by the predator larvae and the balance is, for a time, turned in their favour. The increased density of the host population also favours the increase of the parasites at the expense of the host. Limitation of the supply of suitable breeding material also results in a high rate of mortality among the bark-beetle larvae. The combined effects of the increased parasite and predator population, accompanied by overcrowding in a limited supply of food material, will result in a sudden reduction in the bark-beetle population, which is followed by a corresponding reduction in the parasite and predator populations. It will be seen, therefore, that under natural conditions there is a considerable fluctuation in the rise and fall of the numerical ratio of the host population and that of the parasite and predator population. The time occupied by each cycle may be extended over a considerable period of years, the peak of each host infestation giving rise to a periodic outbreak, corresponding with the period of maximum density of the crop. The automatic opening up of the canopy results in a temporary reduction in the amount of suitable breeding material. Under silvicultural conditions, however, the sudden increase of available breeding material produced when a thinning takes place and the material is allowed to remain on the area provides abnormally favourable conditions for the sudden increase of the bark-beetle population, and an outbreak is precipitated. The occurrence of these outbreaks has led to the popular belief that the remedy lies in what is called “ clean forestry.” In theory, the elimination of all suitable breeding material would solve the bark-beetle problem, but in practice the method is often impracticable when large areas of forest have to be dealt with, as is clearly demonstrated by the frequency with which bark-beetle outbreaks occur as a result of thinning operations.

The object of the experiment was, therefore, to devise a method by which the state of biological control can be continued throughout the rotation, by the provision of the amount of breeding material necessary to maintain a permanent population of hosts which would be kept at a level of economic control by the parasites and predators, and at the same time to bring into practical application the factor of overcrowding as an automatic governor to check any undue increase of the bark-beetle population. The results of the experiments are given in detail, and it is shown that the rate of growth of the crop is a decisive factor.

A scheme is outlined for the study of the use of billets and trap-stems.

Reference is made to operations which tend to upset the balance of insect populations.

Control measures in felling, burnt, and windfall areas are also discussed.

1. Anopheles maculipennis, Meigen.

The larvae are found in the low-lying districts of the Island in shallow pools and irrigation ditches containing a medium amount of aquatic vegetation yet well exposed to sunlight. They are sometimes present along the edges and in the back-waters of drainage canals with an appreciable current, and frequently in slightly brackish(up to 10 per cent. salinity) waters by the sea-shore. They are most plentiful in Lake Antiniotissa among the floating masses of Monostroma (? bullosum, Roth-Wittr.) at the mouths of several fresh-water springs which flow into that shallow and slightly brackish mere from the south.

The adult bites most frequently after sunset and is the principal transmitter of the malarial parasite in the Island.

The paper deals with Anopheles funestus and its allies as they occur in East Africa. The species dealt with are A. funestus type form, A. rivulorum, A. rivulorum var. garnhamellus and A. leesoni.

1. Differences between adults are so slight that they have until recently all been regarded as A. funestus. They may, however, be separated from one another by the points given in the Key (above). Differences between larvae of the species are much more pronounced.

2. It is also shown that, in this part of Africa at least, A. funestus, though reared from identical larvae and pupae, has four main forms of wing pattern. One of the forms of A. funestus appears to be absent from Uganda, while another form is much more prevalent in coastal regions than inland. A. rivulorum occurs in Uganda, but only two specimens were taken in Tanganyika. A. rivulorum var. garnhamellus is widely distributed throughout E. Africa. A. leesoni was found only in Uganda.

3. A. funestus, A. rivulorum and A. leesoni breed in similar situations, i.e., clear, shaded water with growing vegetation. The larvae are more frequently found among grass than among other types of vegetation. Such breeding-places occur in rivers, streams, pools and swamps. Light readings taken at breeding-places corrobate the many reports that these larvae prefer shaded situations and are absent from exposed waters. Larvae of A. rivulorum var. garnhamellus are found most frequently associated with Pistia stratiotes, though on at least two occasions they were found in water where this plant was absent.

4. All the adults were taken inside buildings and none outside, in spite of continuous searching. Almost all were A. funestus, the remaining few were A. rivulorum and A. rivulorum var. garnhamellus; adults of A. leesoni were not taken at all. At several places, though adults of A. funestus were common in houses, very few or no larvae of this species were found; but larvae of the other forms were present. It is concluded that A. funestus is therefore an habitual house-frequenter and the others are not. Human blood was found in roughly half of the female A. funestus examined (239 out of 456); a very few contained ox blood and the remainder (204) were negative for ox and human blood. They were not tested for other bloods. Of 122 female A. funestus examined for malaria parasites 15 were found infected.

As a result of several years work in the Anglo-Egyptian Sudan (Maxwell-Darling, 1934, 1936, 1936 a), it was concluded that the only outbreak centres of the Desert locust in north-eastern Africa were on the Red Sea coast. It appeared probable, however, that there existed other outbreak centres in Arabia, and unless those could be discovered and controlled, an outbreak originating in Arabia would spread into Africa and the Near East.

1. Reference is made to the proven capacity of aphides of the genus Capitophorus to transmit virus disease among strawberries, and attention is drawn to the confusion existing as to the actual synonymy of the insect principally concerned.

2. For the first time sexual and asexual forms of the species commonly present in England have been observed together. Evidence is considered which suggests that the aphis is Capitophorus fragariae, Theo., and that American forms are in reality other, but closely related, species.

3. The incidence of the aphis in the field is considered, and the biology as observed in field and laboratory is discussed.

4. The economic significance of the aphis is referred to, and attention is drawn to the practical difficulties attending efforts to keep it in control, particularly in commercial strawberry-growing areas.

The species of Encyrtidae and Aphelinidae described as new or listed in this paper were among a lot of Coccid-inhabiting parasites received from the Entomological Branch, Department of Agriculture, New South Wales. This material was obtained in Kenya and Uganda during August to October 1935 by William B. Gurney, Entomologist, Department of Agriculture, N.S.W., mostly from Ceroplastes spp. Except for Scutellista sp., only species of Encyrtidae and Aphelinidae are reported upon in this paper. Mr. Gurney visited Kenya and Uganda for the purpose of finding and despatching living parasites of White Wax Scale (Ceroplastes spp.) in East Africa to establish in New South Wales for control of White Wax Scale of citrus trees and shrubs. While in Africa he arranged for Mr. H. Wilkinson, Entomologist, Kenya, and Messrs. H. Hargreaves and T. H. C. Taylor, Entomologists in Uganda, to continue to despatch further consignments of parasitised White Wax Scale after he had left.

An actograph apparatus is described for recording in 24-hour periods, under controlled conditions, the activity of Locusta migratoria migratorioides (R. & F.) in terms of distance travelled.

Great variation was observed in the amount of activity shown by different individuals and the activity of any one individual is shown to vary considerably over each stadium, the highest level occurring about half-way between moults, and falling off towards the beginning and end of each stadium.

An insect is shown to be capable of very intense activity immediately before a moult if no convenient moulting place is found.

No significant difference is found between the activity of males and females, but the average distance travelled in a 24-hour period in the 4th and 5th stadia is shown to be greater than that in the 2nd or 3rd.

The daily activity of adults is shown to vary considerably from day to day, and the diurnal distribution of the activity of adults up to seven days old is shown to be similar to that of nymphs.

The unequal distribution of activity over each 24-hour period is shown to be due to absence of fresh food in the second half of each record, and the effect of this starvation is shown to vary according to the stage of development of the insect.

The effects of changes in relative humidity on the amount and distribution of activity are shown to be very slight or none.

A diurnal periodicity is shown to be induced in the insects when reared under alternating 12-hour periods of light and dark. The longer the conditioning lasts, the more clear-cut is the periodicity. In constant darkness the periodicity is retained for only a few days and gradually disappears.

A tendency for periods of high activity to recur every 2–2½ hours is demonstrated in certain records. In the other records, constituting actually the majority, it is suggested that the periodicity is masked or that the locust's nervous mechanism is inadequate to maintain it.

Preliminary experiments with a form of trophograph suggest that the 2–2½ hour periodicity may be associated with a hunger rhythm.