Hibernation is still one of the obscure phenomena in the bionomics of Anopheles, for the nature of hibernation itself, as well as the associative changes of fat deposition and retarded ovarian development, have not as yet been made clear. Despite the extensive investigations on the subject, the factors responsible for hibernation remain unknown.

The writer took over the Shinyanga fly-rounds in November 1934 from Mr. W. H. Potts, Senior Entomologist, under whose charge they had been since June 1932. The Maswa fly-rounds were not taken over until April 1935, when some of them had been in progress for a few months.

The Shinyanga area, its climate, topography, game and vegetation, have been described by Mr. H. M. Lloyd (1935), by Mr. C. F. M. Swynnerton (1923 and 1936), and by Mr. W. H. Potts in an hitherto unpublished paper, and no further general account is necessary. Table I gives in summarised form a synopsis of the seasons. The Maswa fly-belt lies to the east of the Shinyanga belt, separated from it by the Sukuma Cultivation Steppe, and was, until recently, part of the main G. swynnertoni belt that stretches from the bottom of the Serengeti Plains to Arusha and Moshi. As the result of reclamation measures carried out by the Tsetse Research Department during recent years, this belt has been severed from the main fly-belt, and the south-eastern section of this severed portion has again been cut off from the remainder by clearings. In this small isolated block of some 150 square miles an experiment in the exclusion of grass fires as a control measure against the tsetse was initiated in 1934, and fly-rounds were started in that area in order that a control might be kept on the progress of the experiment. Owing to administrative difficulties the experiment had to be discontinued in mid-1935, but the writer decided to continue the fly-rounds and to increase them by two additional rounds in the hopes of producing information, complementary and supplementary, to that from the Shinyanga rounds. The results of the fly-rounds from these two areas appear to throw light upon the vegetational preferences of G. swynnertoni and form the subject of this paper.

The eggs of Locusta migratoria migratorioides, R. & F., increase in size during development. The increase is due to the absorption of water from the surrounding moist soil.

The wet weight of a freshly laid egg is 0·0063±0·0008 gms, and of a fully developed egg 0·014±0·002 gms. The dry weight of a freshly laid egg is 0·003± 0·0004 gms. and of a fully developed egg 0·0024±0·0002 gms. The water-content of an egg increases from 51·92±3·53 per cent, of the wet weight in the freshly laid egg to 82·36±2·14 per cent, in the fully developed egg.

The egg-wall consists of an exo- and endochorion and a thick vitelline membrane. The latter has a felt-like structure in the freshly laid egg, but as the egg develops, this membrane increases in thickness and acquires a laminated character.

The micropylar apparatus consists of a ring of about 35–43 oblique, funnelshaped canals arranged round the egg near its posterior end.

1. The influence of atmospheric humidity on the various stages in the life-cycle of Microplectron fuscipennis, Zett., is examined. Both the longevity of the adults and the extent of oviposition are found to be proportional to the saturation deficiency of the atmosphere. Under favourable temperature conditions, functional activities are at their maximum in a moist climate, but a wide tolerance is exhibited so far as oviposition is concerned. At normal humidities no effect on the developmental period of the parasite is apparent when the humidity is varied, and this is shown to be due to the protection afforded by the host cocoon.

2. Temperature affects the parasite in a normal manner. The threshold of development is approximately at 8·3°C., and the zone of functional activity is from 15° to a little over 35°C. Optimum conditions for oviposition and development occur between 20° and 35°C. Death occurs at 40°C., while at the lower temperatures, near freezing point, starvation of adults takes place after a lengthy exposure. The hibernating parasite can withstand temperatures very much below freezing point, field records coming from countries where the winter temperature falls to so little as −37°C.

3. The relation of Microplectron to climate is discussed and an explanation is offered of the wide variation in natural parasitism occurring in European countries.

4. The actual and possible distributions of the parasite in Europe are discussed and a map is presented depicting the position as known at present.

5. The possible distribution of the parasite in North America, after liberations have been made, is dealt with and it is shown that the present trend of dispersal of Diprion polytomum is in the direction of climatic conditions that are more favourable to the parasite than are those in the area where the parasite has already become established.

As a basis for further work on the biology of termites, the need for which is now being generally recognized in view of the importance of this group of insects as pests in all tropical countries, the present list of the termites of Tanganyika Territory has been prepared. It incorporates the results so far obtained from the examination of a collection made by the writer during the past three years in a number of widely separated localities in Tanganyika, with the records given by Sjöstedt (1926). Previous records have been mainly from the Kilimanjaro-Usambara area in the extreme north-east of the Territory.

When studying the biology of the house-fly or any other fly annoying to man and domestic animals with a view to practical control, it is obvious that a correct knowledge of the breeding-places of the species is perhaps the most important problem which the investigator has to solve. As to the common house-fly (Musca domestica, L.) it is generally held that this problem has been completely cleared up by several workers years ago, but recent observations in Denmark have convinced the writers that this is not the case. We have arrived at conclusions regarding the chief breeding-places of the house-fly differing from those generally found in text-books.

Our work has not been limited to Musca domestica, for we have as far as possible studied the breeding-places of other flies occurring in houses or connected with domestic animals, first and foremost the stable-fly (Stomoxys calcitrans, L.). The knowledge of the biology of the stable-fly in Europe is surprisingly meagre, though the practical interest of this species as a tormentor of cattle and horses and a possible vector of infectious diseases is generally recognised.

As our observations may be of some interest to workers in other countries we have collected them in this paper, which constitutes the third of a series containing the main results of our investigations into the fly problem started under the auspices of the Health Organisation of the League of Nations and the Danish Committee of Rural Hygiene and with the support of the Danish Ministry of Agriculture and several private funds.

Some of the problems involved in the estimation of parasitism in populations of Heliothis eggs are discussed:—

(a) Effective parasitism of the “active fraction” of eggs as laid in situ is denned.

(b) The habits of the egg-laying moth in point of the duration of oviposition on individual crops and diversion of moth activity from one host to another are discussed in relation to releases of Trichogramma lutea. Data are given on the distribution of bollworm eggs in a crop and associated factors.

(c) Investigations on the dispersion of liberated parasites are described. Dispersion was found to be rapid and widespread; concerted activity by large numbers in given areas did not apply.

Investigations in rain-grown crops are described and results are quoted from a typical experiment in maize, wherein the percentages of parasitism recorded in a large number of equal sections of the crop are regressed on proportionate larval survival. Although the egg parasitism ranged from 21·2 per cent, to 82·3 per cent., differences in larval populations were inappreciable. An explanation for this is offered in an analysis of the effect of various mortality factors.

The parasite was relatively ineffective in cotton crops. The low degrees of parasitism found are assigned to the growth-habit of the plant, the scattered manner of egg deposition thereon and the impediment offered to the insect by the dense hair processes of the plant at many sites where eggs are commonly placed.

Investigations on irrigated (cool season) market-garden crops and citrus orchards are described. These form the principal breeding sources of summer bollworm. Oviposition is extensive and sustained for three to four months on these crops, thereby affording opportunity for continuous parasite activity and the cumulative participation of progeny bred in the field. In nature Trichogramma lutea does not, however, appear until the latter end of the egg-laying by Heliothis and the authors were unable to establish laboratory-bred representatives at an earlier period.

Another egg parasite, Phanurus ullyetti, is prevalent before Trichogramma appears and accomplishes much that was hoped for from the attempted earlier introduction of Trichogramma. In effect, the latter, as seen from diagrams furnished with the paper, becomes substituted for Phanurus toward the close of the winter season. It is probable that temperature is a determining factor in the biology of both parasites, although other causes for the observed relations are suggested.

Further investigations are needed on the subject of exploiting T. lutea in the cool season.

In common with the rest of southern-central Africa (Uvarov, 1933) the Nyasaland Protectorate was affected late in 1932 by the spread of the sixth generation of the red-winged locust. The course of the invasion, development of subsequent generations, and the damage done have been fully described in the Annual Reports of the Department of Agriculture for the years 1933 to 1934 (Smee, 1934, 1935).

1. There are four species of Otiorrhynchus which commonly, in both the larval and the adult stage, cause damage to strawberry plants.

2. The morphology of the first larval instar of these species is discussed from the point of view of their determination.

3. It is shown that although the larvae in this stage are superficially very similar, there are considerable differences in the chaetotaxy of the head and also in the form of the labrum and the setae situated upon it.

4. Similarly there are variations in the position and size of the setae on the dorsum of both the thorax and abdomen.

5. A table is drawn up summarising all these characters in each of the four species.

6. A brief description of the present knowledge of the biology of these species is also given. It appears that although all of them are usually parthenogenetic, it is at present uncertain whether they can ever reproduce sexually, since the presence of males has as yet not been recorded.

7. These species usually have only one generation in the year, ovipositing in mid-summer and over-wintering as well developed larvae. In the case of O. sulcatus and O. ovatus, however, adults may emerge late in the summer and, having hibernated as adults, lay eggs in the early spring following.

Fruit-piercing Lepidoptera constitute an important problem in some parts of the world, such as Africa, Australia and India; they also occur in Ceylon, Fiji, Dutch East Indies, Indo-China, Japan, Malaya, Samoa, and South America.

In Sierra Leone, grape-fruit, orange (sweet), mandarine, tangerine and sweet lime, are affected in addition to cashew, mango, bread-fruit and jak-fruit; whilst in other countries apple, apricot, banana, fig, grape, guava, litchi, nectarine, peach, pear and pomegranate, have been recorded as other adult food-plants; it is noteworthy that in South Africa grape-fruit does not appear to be attacked. Available information regarding fruit-piercing species and their biology is meagre compared with that of many other groups of economic insects, and it is considered desirable to place on record observations made in Sierra Leone.

Difficulties in the way of the study of these insects are the lack of knowledge regarding (a) larval food-plants; (b) characters and habits of the larvae; (c) the breeding areas and possible migratory habits of the larvae; (d) the breeding areas and possible migratory habits of the adults of some species.

Unless otherwise stated this account applies to Njala, where there is a plot of budded citrus; the trees were planted in 1925-1927 and mainly consist of Late Valentia and Washington Navel orange, and Marsh and Foster grape-fruit. The sweet lime, mandarine and tangerine are about ten years older.

A study of the variations of the population of Dysdercus fasciatus on cotton and on its wild host-plants is described.

The most important host of D. fasciatus in the Acacia savannah of Northern Rhodesia is Thespesia rogersii, and it is shown that at certain times a general flighting of stainer takes place from this host-plant caused by food shortage or defoliation. Generally a period of food shortage occurs during the earlier months of the year owing to rotting of the old crop and extensive destruction of the early new crop by the larvae of a Cossid moth. This causes an early influx into cotton, which leads to the establishment of a large population in the field at a critical period in the development of the bolls. When the early crop is retained on the trees a continuously increasing food supply is provided, and this first movement does not take place. A second movement from Thespesia, which is largely due to defoliation, begins generally in June. It has been shown that a second influx into cotton coincides with this later movement from Thespesia. A late influx such as this is of little practical importance since the greater part of the crop is picked in May and June.

The observations recorded indicate clearly that the movement of D. fasciatus into cotton is not due to any attraction exercised by the crop but is caused by a forced movement of stainers from Thespesia rogersii.

1. An ecological description of the Red Sea coast of the Anglo-Egyptian Sudan is given, with special reference to the occurrence of the solitary phase of Schistocerca gregaria in its different parts and zones.

2. The greatest numbers of solitary Desert locusts were found amongst raingrown dukhn (Pennisetum typhoideum, Rich.) cultivated in the Suaeda belt of the coast, near the sea.

3. The factors responsible for the higher population of solitary locusts among the cultivation are probably the soil consisting of soft loose sand, and the more or less evergreen condition of the weeds on cultivated plots. It appears possible, however, that in some localities with naturally loose sandy soil all areas suitable for vegetation are cultivated, and in this case the cultivation in itself is not of primary importance.

4. Incipient outbreaks were observed in the type of cultivated areas described above in 1933–34, and again in 1934–35 winter seasons. Hoppers of the phase congregans were found mostly on a weed, Heliotropium undulatum, which is preferred by young hoppers to other food-plants, and seemed to act as a concentrating factor for the hoppers. No hoppers of the ph. congregans were found on clean cultivation where this weed was absent.

5. The chief factor determining the commencement of an outbreak seems to be heavy winter rains (over 240 mm. during the season), starting early (end of October) and continuing late (end of February), which allows for the development of two successive winter generations, as follows:—(a) Early maturation of old adults (November); (b) plentiful oviposition of old adults (November-December); (c) hoppers beginning to emerge (end of November); (d) hoppers beginning to become adult (early January); (e) majority of hoppers adult (end January); (f) these young adults remaining among dukhn in a fairly crowded condition (February); (g) young adults maturing (end February); (h) young adults ovipositing (March); (i) hoppers hatching (end of March-April); (j) young hoppers crowded on Heliotropium, assuming congregans coloration and later forming marching bands (April); (k) emigration of young flying swarms (May).

6. The exact cause of the rapid maturation of young adults of the first winter generation has not been discovered, although a short period of very high humidity seems to have some effect. There is no doubt that late rains are necessary for most adults to mature and oviposit in the field.

7. The Red Sea coast of the Sudan is distinguished from the interior of that country by its higher air humidity, by winter rains, and by the fact that the rainy season can extend for a longer time than the summer rainy period inland. The northern parts of the coast, north of the latitude 20°N., are less likely to produce outbreaks only because heavy and prolonged rains are unlikely to occur there.

8. General conditions in Eritrea, south of the Sudanese border, are such that some outbreak areas should be expected to exist there.

9. It appears probable that the Arabian coast of the Red Sea also contains some outbreak areas. As regards inland parts of Arabia, their climate, the distribution and the life-cycle of the solitary locusts there, are too little known to estimate the possibility of the existence of outbreak areas, until a special investigation is made.

10. The results of the investigations on the Red Sea coast put under suspicion of harbouring outbreak areas of the Desert locust all those parts of the sea-coasts of Africa and Asia which may obtain in some years winter rainfall of not less than 240 mm. extending for a period sufficiently long to allow for the development of two successive winter generations of the locust.

During the testing of finely ground pyrethrum flowers as an insecticide for the control of Antestia lineaticollis, Stål, in coffee trees, it was noticed that the various instars showed different percentage death rates under the same conditions. The experiment which is dealt with here was primarily designed to discover the minimum effective dose of powder per tree, and was carried out as follows.

A block of 1,700 coffee trees was divided into seventeen square plots each containing 100 trees. Nine of these plots were treated with pyrethrum powder at rates varying from about 1 gram to 5 grams per tree; all the trees in the same plot receiving the same amount of powder. Two days later 36 trees from each of these plots, comprising all the trees from the centre of the plots (the two outer rows of each plot not being used in case migration of the Antestia should have taken place from the adjoining control plots) were heavily drenched with a strong kerosene extract of pyrethrum in order to bring down all the Antestia remaining on the trees; these Antestia were collected separately for each tree, sorted into instars and recorded. This method of testing is described fully by Le Pelley (1934).

In each of the eight control plots five trees selected at random were drenched with the kerosene extract of pyrethrum and the Antestia obtained were recorded in the same way. It was found that the average number per tree of Antestia and of each instar present in each of these control plots, which were themselves evenly distributed through the whole block, was practically constant. It was therefore assumed that the numbers of Antestia and of each instar was the same for the plots treated with pyrethrum prior to this treatment, and the number of each instar found on the trees after treatment subtracted from this figure represented the number which had been killed by the pyrethrum powder.

A short tour of northern Darfur was made by the author, on behalf of the Imperial Institute of Entomology, with the object of observing the solitary Schistocerca population, comparing it with that of northern Kordofan, and looking for any factors which might indicate the presence of potential outbreak centres of the desert locust.

The genus Cicadulina was established in 1926 (Bull. Ent. Res. 17, p. 43) to hold a new species, C. zeae, China, injurious to maize in Kenya Colony. Later (Bull. Ent. Res., 19, 1928, p. 66) it was shown that Balclutha mbila, Naude, recorded as transmitting the virus of streak disease of maize in Natal, also belonged to this genus, and two new species C. arachidis and C. similis were described from the Gambia, where they were reported as injurious to ground-nut and suspected of transmitting the virus of the rosette disease of that plant. Since that time Dr. H. H. Storey of the Amani Research Station has been investigating the possibility of transmission of the streak virus of maize by C. zeae. In attempting to breed strains capable of transmission of the disease certain crosses were made which showed conclusively that he was dealing with two distinct species. These species he was able to separate on the colour pattern of the abdomen. Dr. Storey has now sent to me material of both these species and a study of the genitalia corroborates his finding. One, of course, proved to be C. zeae, the other is new and I therefore propose to dedicate it to the discoverer.

The types of the new species described below have been deposited in the British Museum.

This is an account of laboratory experiments made with the tsetse Glossina palpalis. The results deal mainly with the effects of climatic conditions, temperature and humidity in particular, on the metabolism and life-cycle. Some work was also done on the activity and behaviour of the fly, but this is very incomplete, though it shows the importance of the problem and the need for further study.

The work was done during a visit of just over a year to East Africa, in 1935-36, as Wandsworth Scholar of the London School of Hygiene and Tropical Medicine. I spent most of the time at the Human Trypanosomiasis Institute, Entebbe, Uganda, and also visited tsetse areas in Kenya and Tanganyika. I am grateful to all those who helped to make my visit profitable. Among others, to the Directors of Medical Services of the East African territories, in particular the Hon. W. H. Kauntze of Uganda, and many members of their departments. To Mr. C. B. Symes, Medical Entomologist, Kenya, and to Mr. W. H. Potts, of the Department of Tsetse Research, Tanganyika. I am especially grateful to Dr. H. Lyndhurst Duke, Director of the Human Trypanosomiasis Institute, for many kindnesses. Considerable assistance was received from Mrs. Helen Mellanby, who was working on allied problems at Entebbe. And mention must be made of the intelligent and conscientious help of my laboratory assistant, Omw. Bonaventure Semalwadde.

1. All material was reared under constant conditions of temperature, light intensity and relative humidity. Two relative humidities were used—very wet and very dry. In some cases various coloured backgrounds were used. All material was solitaria, and was kept isolated.

2. Average weights were calculated from weighings made at all periods within the stadia, and thus represent the weights at the mid-points of the stadia.

3. The figures could not be fitted to the theory of a progression factor of 2.

4. Females are on the average 50 per cent, heavier than males even in the third instar; the sexes can probably be distinguished in this way much earlier.

5. The first three stadia are of about the same length; the fourth is longer, the fifth much longer.

6. The percentage rate of growth between the mid-points of successive stadia is of the same order for all pairs, though somewhat lower for the first and last pairs.

7. Hoppers kept in a very dry atmosphere are much lighter than those kept wet —proportionally more so in the later than in the earlier instars; on the other hand each stadium is lengthened—proportionally more so in the earlier than in the later stadia; the percentage rate of growth is just half that of hoppers kept wet.

8. The findings of Faure in regard to the causes of differences in coloration were fully confirmed.

9. The occurrence of a sixth instar in the females is due to an inherited factor.

10. This “ extra ” instar may represent an extra morphological third instar or an extra morphological fourth instar.