♂♀. Derm piceous, shiny, with dense grey scaling more or less mottled above with dark brown patches.

1. Quantitative methods of recording the activity of blowflies are described.

2. With constant temperatures the greatest activity occurs near the centre of the temperature range, whereas with rising temperature it immediately precedes the upper thermal death-point.

3. Rising temperature causes activity to occur at a lower range of temperatures than does constant temperature.

4. Rising temperature causes the appearance of “distress activity” at high temperatures, but constant temperature does not.

5. For the development of the necessary energy for full crawling and flight activity at the most favourable temperatures, rather long exposure to these temperatures is necessary.

6. Flight and, to a lesser extent, crawling occur in bursts of activity whether the temperature is rising or constant.

7. Differences in the reactions to temperature of the closely related species Lucilia cuprina and L. sericata are very distinct.

8. The curves for general activity and temperature preference correspond to the known distribution of the four species examined.

9. Frequency of regurgitation is definitely associated with high temperature.

10. There are strong indications that the conditions of the experiment were suitable for the flight of L. cuprina but unsuitable for that of the other species examined. This may have been due to the lack of bright sunlight, or to the confined space of the observation-jars.

11. It is shown that activity is a complex phenomenon, and that the character of the results obtained is influenced by the kind of activity examined, by the methods of measurement used, and by the nature of the temperature conditions to which the insects are exposed.

1. From a block of country of four square miles, infested by Glossina swynner-toni and a few G. pallidipes, grass-fires have been excluded for three years in succession. The tsetse-population has decreased in that time by nearly nine-tenths (from 9.4 to 1.0 flies per 1,000 yards of transect). In a block of two square miles it has decreased in two years without burning to the same average of one fly per thousand yards of transect from a high previous figure unmeasured. Two “barrier” strips following roads that previously were highly infested have also been unburned for three and four years respectively and have become similarly inhospitable to the flies.

2. In a control block of only 1¾ square miles, the grass has been burned in the ordinary native fashion annually during the same period. The average fly-catch per thousand yards of transect has increased since this was done from 4.2 to 13.1.

3. In each of these blocks game is about as plentiful as it was at the first. The 4-square-mile block shows a slight gain.

4. In the four experimental blocks and strips, but not in the controls, extensive thicket is growing up everywhere in the grass as a result of the exclusion of the fires. Thus the previous marked difference, both spatial and seasonal, between the respective densities of the different vegetational communities is commencing to disappear. Much grass-country remains but its average condition is one of long grass rising from a mulch, thick or thin and sometimes absent, of the previous year's grass that keeps the soil damp after rain—the more so since run-off is checked. Longer and denser grass is encroaching into the previously very open concentration sites of G. swynnertoni, which are also being invaded by thicket.

5. The contrasts between burned and unburned country are especially strong in the short wet season. At this time in burned country the flies have just gone through a period of intense desiccation, short hunger cycle and hardship, and the population is at its annual minimum. The ground, however, is very open and visibility of the other sex and of food animals and breeding-places is unimpeded. Conditions are suddenly made ideal by the advent of the rains. Humidity is added to temperature; the hunger cycle is lengthened; the openness and insolation of the ground now probably play a further beneficent part by preventing an excess of humidity. The flies are active, they breed freely, the shade conditions enable them to spread, and the density curve soars upward.

On the unburned ground the water-content of the soil is increased in the early rains, dampness is retained between showers, the temperature is lowered, evaporation is reduced, and light intensity in the grass becomes less (Scott, 1934). The activity and breeding of the flies is quite likely affected. The striking increase in the population that characterised unburned country in the early rams and short dry season is absent, and the density, having failed to rise at this time, continues low or falls further.

6. In two cases (G. morsitans, Nash 1933, at Kandaga; G. swynnertoni in Block 11 at Shinyanga) the second annual impetus to breeding, associated normally with the advent of the long dry season, duly produced its usual effect on the tsetse-populations of country that was in its first year of no burning. In the case of the block that has been unburned for three years this effect has been slight.

7. That the conditions, though deteriorating, are as yet not lethal through hunger, due to poor visibility or otherwise, is suggested by the fact that the very small fly populations referred to maintain a nearly stationary balance in at least the larger experimental block and do not show special hunger or other sign of distress. It is possible that most of the diminution hitherto has been caused merely by emigration to better conditions, for the blocks are not yet fully isolated. On the other hand, were the main effect on the breeding, distress would not be detected and the result might take place independently of any emigration. Reduced visibility of food animals may become operative later.

8. It is suggested by the results so far on the tsetse and by the present appearance of the country in these four experiments that with the further advance of the vegetational succession towards its natural climax the remaining fly population will probably dwindle further and disappear—at least if the areas are isolated; the growing homogeneity in the density of the whole vegetation will reach a point at which it is unlikely to satisfy the daily and seasonal needs of an insect which for food, breeding and regulation of moisture and temperature, has a separate and vital use for each of the three densities furnished by thicket, savannah wooding and nearly open hard-pan and vlei.

9. The concentration sites of G. swynnertoni combine in a small space the types of vegetation the flies need, both the denser and the more open. They are important at all times but especially as refuges from unfavourable conditions elsewhere and as meeting-grounds of the sexes when the population is reduced. They are operative all the year round, and an effective change in these refuges alone in either the wet season or dry should be a shrewd blow at the fly. In experiments elsewhere in Shinyanga the clearing of the thickets at these places has quickly brought down the fly-population through its dry-season effect. In Blocks 4A and 10A the cessation of grass-burning is apparently already affecting these sites by hemming them in with areas presenting unfavourable conditions—probably mainly through excessive shade and over-humidity in the rains. The cessation of burning might even suffice if confined to these concentration sites and their neighbourhood.

10. As regards the probable effect of not burning the grass on other species of tsetse, it is considered that the method may prove useful against G. morsitans under moderately extensive vegetational conditions, though it may in this case take much longer and may not apply to large areas. Berlinia-Brachystegia wooding went to thicket in the writer's early experiments in a specially high rainfall area in Rhodesia, and (under lower rainfall) the exclusion of fire for five years at Itundwe (Central Province, Tanganyika) has produced strong densification in the Berlinia. In the Kikore plots (5 years protected) savannah type seedlings are being suppressed by the new conditions, but the flourishing state of the few shade-tolerating thicket plants suggests that all that is wanted is the introduction of a suitable seed-supply. This will be necessary in any case in all places without natural regeneration.

11. In an observation by Nash (Kandaga, Central Province) G. morsitans reacted initially in much the same way as G. swynnertoni, but the experiment was interrupted. In Itundwe G. morsitans and its pupae are much less numerous in the unburned Berlinia than in the burned.

12. The reaction of G. pallidipes, as distinguished from that of its habitat, is uncertain but so far has been promising under Shinyanga conditions; but the new conditions at Itundwe look as though they might favour this fly. G. brevipalpis is definitely likely to be favoured by the effect of not burning the grass.

13. The increase in humidity and lowering of the temperature produced by not burning the grass may be expected to be specially effective towards the wet side of a tsetse-fly's range. Towards the dry side it might even at first assist the fly.

14. Experiments to test the possibility of success against morsitans are being taken in hand, as are experiments on larger pieces of country infested by swynnertoni and pallidipes.

15. The control of grass-fires offers difficulties, but our experience over a wide area and many years shows that with determination and organisation it is quite possible, though an occasional minor set-back must be expected. The advantages of this measure from other points of view than that of tsetse extirpation, and the means of restoring the pasture, are referred to on p. 425.

The presence in Southern Nigeria of a well defined group of mosquitos whose breeding is confined to holes in trees has been known for some time, and Dalziel (1920) recorded a number of such species from Lagos.

1. The egg, vermiform larva, and the nymphal stages of ph. gregaria are described. It is shown that six stages occur, or seven instars including the vermiform larva. These stages can be distinguished by (a) the number of antennal joints, (b) the degree of backward prolongation of the pronotum, (c) the differentiation of the terminal abdominal structures. Measurements of the pronotum and femur served to distinguish the stages in material from the same swarm, but the absolute measurements cannot be used to distinguish material from different sources.

2. The colour pattern of ph. dissocians is analysed, and colour changes are indicated as divergences from the gregaria pattern. Forms of ph. dissocians observed in the field are grouped into several types the relationships of which are illustrated, and the environmental factors which produce them are discussed.

3. Hoppers believed to be of ph. congregans could not be distinguished from certain forms of ph. dissocians.

4. Cage experiments in which hoppers were reared under varying degrees of crowding are described. It is strongly indicated that activity which is induced by crowding influences the development of gregaria colouring. The green colouring of dissocians hoppers appears to be associated with high humidity conditions and the presence of green food. Other colours of dissocians hoppers are conditioned by those of the environment.

5. An aberrant pallid type of hopper is described and its origin is ascribed to the effects of parasitism by Nematodes and possibly also by Dipterous larvae.

6. Certain inferences regarding the processes in the formation of the colour pattern are inferred from a consideration of the effects of parasitism and of dissocians producing factors.

7. The colourings of young adults of ph. gregaria a few days after the ultimate moult and of types taken from large swarms in August are described. It is shown that colour changes occur gradually in the field, the conspicuous pattern of light and dark coloration of the young adult being obscured and finally hidden by the development of a bright red pigmentation.

8. The colouring of young adults of ph. dissocians is described. These show a pattern of light and dark coloration similar to that of the young adult of ph. gregaria, from which it is indistinguishable, immediately after the ultimate moult. In ph. transiens no marked colour change takes place throughout the life of the individual except the development of a purple coloration on the hind wings.

9. Factors influencing adult colouring are discussed. Adults crowded in cages and derived from hoppers reared under crowded conditions did not undergo the colour changes observed in the field. Material taken from large swarms in the field and showing some development of swarm colouring were maintained under crowded and uncrowded conditions. The red pigment of the body changed to a dark brown in both cases. Under uncrowded conditions no further change took place except a conspicuous development of purple coloration on the hind wings in all individuals. Under crowded conditions the brown pigment spread, its final distribution resembling that of the red pigment in later swarm types from the field, but the red colouring of the hind wings was developed only to a very slight extent in a few individuals. In the case of individuals isolated completely the swarm colouring was lost entirely.

10. It is inferred that swarm colouring in the adult is associated with crowding and possibly with activity and that development of the red and purple coloration on the hind wings in gregaria and transiens is affected by different factors and possibly differs in composition.

11. Biometrical data obtained from a variety of types is tabulated and discussed. Material varied from types taken from very large and dense swarms to what might be described as “solitaria beginning to congregate.”

12. It is shown that certain measurable characters, especially the relative size of the sexes, the degree of development of the femur in relation to the wing, and the relative length and degree of constriction of the pronotum differ greatly in gregaria and transiens types and may be used to distinguish them.

13. In the case of material from very large and dense swarms and from very small loose swarms no differences in the characters on which the types could readily be distinguished were observed. It may be that these small groups were derived from larger swarms.

14. Interesting aberrations occur in the case of a swarm believed to have been one of the earliest to migrate any considerable distance after the commencement of swarming. The quantity of material was insufficient to permit of very reliable comparison but it would appear that in these forms the pronotum of the female was generally not shortened or constricted to the same extent as in extreme gregaria, although the construction of the pronotum of the male approximated fairly closely to that of more extreme gregaria

Observations in the laboratory on the larva of Glossina tachinoides and G. submorsitans show that in both species it is slow in crawling and burrowing and often cannot burrow at all. It penetrates coarse sand more readily than fine, and fine sand than wood ash, and burrows easily in fine sand with pebbles. In nature it probably always burrows eventually, unless it is attacked by predators or parasites to which its behaviour renders it vulnerable.

Previous field work indicates that the depth to which the larvae burrow influences the effect of predators and parasites and sometimes of solar radiation on the puparia. Records of breeding-places suggest that larvae often crawl over hard soil to reach suitable places in which to burrow, and that unless the female fly, before depositing a larva, carefully selects such a place, the mortality due to other insects is probably high.

Most of the mosquitos described here were collected by Dr. H. de Rook and the author during a tour of investigation of filariasis in the eastern part of the Malay Archipelago. The tour was undertaken with a grant from the “Koningin Wilhelmina Jubileum-Stichting” in Batavia.

The egg, the five larval instars, cocoon, prepupa and pupa of Bracon tachardiae, Cameron, are described.

Two series of larvae, one male and one female, occur, these series overlap very considerably and it is only towards the maximum and minimum of the range that larvae are respectively entirely female or male.

It is shown that the five larval instars of B. tachardiae may be grouped by the widths of the head-capsule, and that an instar can be characterised by the head-width, particularly if only averages are considered. The actual range of head-width in each instar is rather large, and in some cases the extremes overlap. In actual practice head-width is a safe indication of the instar of a larva as the extremes rarely occur; the widths calculated on Dyar's principle also approximate sufficiently closely to the observed widths to preclude the chance of an ecdysis having been overlooked.

The length of the mandible is for practical purposes identical in a larva of any given instar and in its exuviae. The larval instars and their exuviae can be grouped by the lengths of the mandibles, particularly if averages are considered; the range for a given instar is wide but the extremes do not overlap. The lengths calculated on Dyar's head-width principle approximate closely with the observed lengths, sufficiently so to preclude the possibility of overlooking an ecdysis, and making possible the identification of the instar of fixed and mounted specimens of larvae or exuviae, for which purpose head-width is useless.

The factors of increase of head-width and mandibular length are fairly similar, falling near to 3 √2 =1.26, and for practical purposes one may be substituted for the other, the calculated widths and lengths so obtained still approximating to the observed widths and lengths.

Various uses of this fact are indicated. Preliminary investigations point to the fact that similar observations apply to Aphrastobracon flavipennis, Ashm., an ectoparasite of Eublemma scitula, Ramb. It is suggested that similar observations may be true for other ectoparasitic Braconids.

The growth of the body of the larva from instar to instar is independent of the growth of the head-capsule, larvae increasing in weight and in volume by a figure lying between 3 and 4 times from instar to instar. The actual figure obtained theoretically for volume increase was 3–6. The head-size increases by the usual double at each moult.

1. Collections of Cydia pomonella were made in France in 1928 and 1929–30.

2. The numbers of moths and parasites that emerged from the collections are given.

3. The biology and host-lists of the parasites are dealt with, and information on the larval anatomy is given.

4. Low percentages of parasitism of the larvae were found, and it is concluded that predacious birds, and the removal of larvae with the crop, must be important factors in the control of the Codling Moth in France.

This paper records a number of parasitic and phytophagous species of Chalcididae that have been reared in U.S.S.R. during recent years. The material was partly collected by the author herself, or received for identification from various persons and institutions.

For years the territory adjacent to the rivers on the floors of the Sacramento and northern San Joaquin valleys in California has been deluged each spring with hordes of fiercely biting “black gnats.” Certain areas locally known as “black alkali” locations seemed to form the foci from which these pests were blown by winds over wide areas, constituting such a pest in some seasons that agricultural field work was brought to a standstill and even town dwellers were driven indoors until nightfall. The bites are extremely irritating, causing nodular, inflamed swellings that itch persistently for several days or even weeks. In some individuals, particularly those inclined to be stout, the swellings caused by the bite become vesicular, rupture, and produce a moist open lesion that “weeps” a serous exudate for weeks, finally healing with a definite red scar. The insects insinuate themselves beneath the clothing and apparently prefer to bite at some point where their progress is impeded, such as around the hat band, at the belt line, or where the sleeves are closely rolled against the arms, and at the shoe tops. The usual repellents that are effective against mosquitos are of little use against these insects, the only casualties noted being the ones that were actually trapped or drowned in the oily applications used.

Owing to the deposition of resin, the females assume two shapes, one somewhat circular in which the mouth-parts are situated ventrally about the middle of the body, and the other pyriform, in which the mouth-parts are situated at the extreme anterior end. In the former type of females the mouth-parts are posteriorly directed and in the latter anteriorly. The rostrum lies outside the body cavity between the anterior pair of oral lobes. The rostralis opens into the pharynx which lies in the tentorium. The oesophagus is elongated and passes into the colo-rectum to be succeeded by the convoluted ventriculus. The ventriculus on leaving the colo-rectum leads into the intestine, which is marked into the mid and hind intestine by the junction of the ampulla of the Malpighian tubes. The intestine after forming a loop round the greater part of the colo-rectum re-enters it close to the point of its commencement from it and continues closely attached to the outer side of the ventriculus from its distal to its proximal end; after this it comes out of the colo-rectum and runs alongside it to open into it near the anterior third of its length. The convolutions inside the colo-rectum are comprised of the ventriculus and the part of the hind intestine running outer to it. The “colon caecum” is absent. The colo-rectum opens at the anus situated at the posterior end of the insect and is divided into colon and rectum by the opening of the intestine into it.

The salivary glands consist of two branches of ovoid and spherical bodies. The common duct of the salivary gland of each side runs close to the ventral ganglion and joins the opposite duct to form the terminal duct near its anterior end, which then opens into the pharynx.

The nervous system consists of a bilobed cerebral ganglion which lies anteriorly to the mouth-parts in females in which the tentorium is directed posteriorly, and either laterally or ventrally to it in females in which the tentorium is directed anteriorly and lies at the extreme anterior end. The cerebral ganglion is joined by a pair of connectives to the ventral ganglion, which lies dorsal to the tentorium in females in which it is directed posteriorly, and posterior to the tentorium in which it is directed anteriorly and lies at the extreme anterior end. The ventral ganglion is followed by the nerve chord, which varies in length in either type of female. The main nerves arising from the central nervous system are described.

It was in December 1929 that the writer first tried to reduce the terrible mosquito nuisance which each winter plagues the City of Calcutta. His efforts were naturally confined to an attempt to alleviate conditions in the Bengal-Nagpur Railway's Headquarters Colony at Garden Reach, but it soon became obvious that by control in the relatively small area of land belonging to the railway very little could be accomplished, and that to achieve anything appreciable a very much larger acreage would have to be put under control. So when in the ensuing winter of 1930–31 other property owners in the vicinity became aware that this railway was attempting to do something and evinced interest in the matter, advantage was taken of this to form the Garden Reach Anti-Malaria Association, the initiation of which also received a considerable impetus from the virulent outbreak of malaria in the previous autumn at Budge Budge, some 18 miles down-river from the City. This outbreak, and the organisation of and area covered by the Association, are described by Covell (1932).

1. The shore of Lake Chad was suspected of being a reservation of both the Migratory Locust and the Red Lcoust. In 1931 a preliminary survey of the shore was made, as a result of which it was tentatively concluded that about one-half or less of the shore of British Chad may offer conditions suitable for the production of swarms of the Migratory Locust from the solitary phase. The Red Locust was present only in the southern half of the shore. A village named Kalkala, at the south-western corner of the Lake, was selected as the most suitable locality in which to carry out ecological research.

2. The ecology of the two species of locusts and of about 60 other species of ACRIDIDAE was studied at Kalkala during the first six months of 1933. A description is given of agricultural and climatic conditions in the Kalkala area and some notes on the hydrography of Lake Chad are included. The vegetation, soils, fauna and microclimates of the habitats frequented by ACRIDIDAE are described.

3. Collections of Acrididae were made each month in all the principal habitats. It was found that the Acridinae occurred principally in the wettest habitats and that this subfamily exhibited a small degree of ecological plasticity. The Oedipodinae consisted chiefly of geophilous species which were most abundant on bare soil in farm-land. The Pyrgomorphinae were most abundant in two non-gramineous habitats, but were not uncommon in Cynodon dactylon; one species was associated with Calotropis procera. The Catantopinae showed a greater degree of ecological plasticity than did any of the other subfamilies; the majority of the species encountered were most abundant in the drier habitats.

4. Bionomical notes are given for the majority of the species of Acrididae met with in 1931 and 1933 in the Chad area. Evidence was obtained that many species of Catantopinae have a prolonged imaginal diapause. Certain species of Acridinae and Catantopinae are characterised by an embryonic diapause during the hottest months of the year, and one species of Pyrgomorphinae has a nymphal diapause during the early part of the dry season.

5. The Red Locust frequents tall grass habitats from November to the end of April, the adults then gradually move to short grass and farm-land and begin to breed in late June. The imaginal diapause lasts from early October to late July. Biometrical examinations of adults and other data indicate that the Red Locust is in phase transiens (congregans). There is no evidence that swarms have left the Chad area. It seems probable that conditions in this area are unsuitable for the production of phase gregaria.

6. The solitary phase of the Migratory Locust was present in the survey area throughout the six months; it was never numerous and decreased steadily in numbers from January to June in spite of the fact that it was breeding from late February to June. The decrease in numbers is thought to have been due, chiefly, to the attacks of the Carmine Bee-eater and to bush fires.Phase transiens (dissocians) was found until mid-March; there is no doubt that most of the locusts present were derived from the survivors of hopper bands which had been baited or trenched in the autumn of 1932. Swarms arrived in late May and early June and repopulated the area. The principal habitats of the Migratory Locust were Cynodon dactylon, Brachiaria ramosa and Chloris gayana. The scarcity of this species in the southern half of Chad indicated that this area is unlikely to be a reservation; but research over a number of years is necessary to confirm this opinion.