1. The history of the occurrence of Merodon equestris in various countries is related and a list of known food-plants given.

2. The immature stages of the fly are described in detail.

3. The biology of the fly is fully discussed and additions made to our knowledge regarding it.

4. Control measures are reviewed and additional information is given, particularly with reference to the use of a poison-bait spray against the adult flies.

5. Recommendations are made as to the most satisfactory combination of methods to use for the purpose of obtaining control of the fly under field conditions.

6. A list of literature cited is given.

Adding together all the hoppers listed above, we find that 637 individuals were reared in these experiments from 34 different pairs of adults; 394 were reared in complete isolation, and 243 under crowded conditions, but each crowd consisted of the progeny of one pair only. The majority of those isolated were placed in isolation on the day of hatching, but some first lived in a crowd for a week or two before being used to replace isolated individuals that had died.

Comparing the results in Tables XXI and XXII, we noted that the isolated hoppers acquired the solitaria characters, while those crowded tended to develop the gregaria characters, regardless of whether the parents had been gregaria or solitaria. Only two isolated hoppers from the pair L.p.352 showed gregaria characters, and one of these had lived in a crowd and had acquired gregaria characters before it was placed in isolation in its second instar. Table XXIII shows that crosses between gregaria and solitaria gave the same results.

In the second generation (Table XXIV) the progeny of the P1gregaria pair 352 reacted to isolation and crowding in the same way as all other hoppers, and the same was true of the F2 back-cross to gregaria (L.p.569).

Examining the hypothesis of Potgieter in the light of these experiments, we find that the data presented in Tables XXI to XXIV are in direct contradiction with the three phases enumerated above. Instead of giving a majority of gregaria, the matings of gregaria by gregaria produced both gregaria and solitaria according to the conditions under which the progeny were reared. According to the second thesis, the crossing of solitaria and gregaria should always result in a majority of gregaria, but Table XXIII shows that 90 isolated hoppers all became solitaria. Thirdly, the mating of solitaria with solitaria is supposed never to produce gregaria progeny; Table XXII shows that the progeny of these crosses developed gregaria characters when crowded and solitaria when isolated.

Following the method of procedure already outlined, the life-history of Smynthurus viridis, its bionomics in sensu stricto, and the influence of environmental factors under controlled laboratory conditions, having been considered, the next step is an examination of the seasonal cycle of events as occurring in nature. Part II is, therefore, devoted largely to an analysis of the field data, coupled with an interpretation thereof as substantiated by critically planned and controlled laboratory experimentation; this reinforcement being rendered necessary on account of a multiplicity of factors acting simultaneously in nature. The chief difficulty in an investigation of this kind (as with all problems concerned with fluctuations in the numbers of organisms) lies in the fact that there are few methods for obtaining quickly and easily an accurate quantitative sample of the numbers and kind of organisms; and, secondly, there is the difficulty of finding (in a long-inhabited country like Britain) a “normal” environment, i.e., one in which purely natural agencies have been allowed free play over a sufficient interval of time to allow a state of equilibrium to have become established between the various members of the community to which Smynthurus belongs, in their relationship to the physical factors of the environment and to each other.

Pteronidea ribesii, Scop., the common gooseberry sawfly, is widely distributed in Middle and Northern Europe and in North America, and appears to be confined to food-plants of the genus Ribes, particularly R. grossularia and R. rubrum. It has an extensive literature, one of the best and most recent accounts being that of Kemner (1924). In the present account, therefore, only a summary of the author's investigations are given, with emphasis on points of special interest or significance in relation to the present series of studies.

A Section of the Division of Economic Entomology of the Commonwealth Council for Scientific and Industrial Research is devoted to the attempted control of noxious weeds by means of their insect enemies.

Through the kindness of Prof. Mazza, Buenos Aires, Dr. P. A. Buxton, of the London School of Tropical Medicine, and Prof. Brumpt, Paris, I have had the opportunity of examining a collection of sandflies from South America. It appears that, as in the sandflies of the Old World, the structure of the buccal cavity and spermatheca, and to a smaller degree that of the pharynx, affords an easy mean of distinguishing the five species at my disposal.

(1) For the first time sodium fluosilicate has been tested as a poison against the hoppers of Locusta migratoria migratorioides. This poison was found to be as effective as sodium arsenite in baits when used at the same concentration, viz., 2·44%, but was slower in its action. When guinea-corn bran is used as the carrier it is necessary to add salt to the bait as an attractant; the reason for this is not known, fluosilicate baits containing sawdust, chopped hay and chaff from cereal crops respectively were effective without salt being added.

(2) From an examination of the results of experimental work on the relative toxicities of sodium fluosilicate and arsenical compounds to domesticated animals in various parts of the world, it is concluded that the former is less toxic to stock, but that the increased degree of safety acquired through the use of sodium fluosilicate is not so great as is popularly supposed. A definite advantage of baits containing fluosilicate is that they are repellent to many animals, whereas baits containing sodium arsenite are attractive to stock.

A summary is given of the results obtained from the collection of large numbers of the puparia of G. tachinoides and G. morsitans in the Gadau-Sherifuri area and the breeding of tsetse and parasites therefrom. Totals of 106,047 puparia of G. tachinoides and 17,346 of G. morsitans have been dealt with during the two breeding seasons of 1930–31. It is concluded that the Bombyliid, Thyridanthrax argentifrons, Aust., is in this area the only naturally occurring pupal parasite of Glossina of any importance. This fly has formed as much as 6 per cent. of total emergences from G. tachinoides puparia in the month of March, and 2 per cent. of total emergences from G. morsitans puparia for the month of April.

Early in the month of January 1931 a large swarm of the Pyrrhocorid bug, Melamphaus faber, F., invaded trees of Hydnocarpus anthelmintica, Pierre, and H. wightiana, Blume, at the Government Experimental Plantation, Serdang, Selangor, Federated Malay States.

The association between insects and virus diseases of plants and the suspicion which at present rests on Jassidae, amongst others, may result in members of this family becoming of increased importance as potential vectors of virus diseases of crop plants. In America leaf-hoppers are already serious pests of cereals and of grape-vines, and in the cotton-growing area of Central and South Africa a Jassid forms one of the most important obstacles to the successful cultivation of this crop, so that in these countries a considerable amount of attention has been demanded by this group of insects. In this country, however, the leaf-hoppers have only been regarded as of minor importance, though in recent years increasing interest has been taken in certain species infesting potatoes and glasshouse crops. It was suggested to the writer that further knowledge of the biology of these insects was desirable, especially in view of the extreme importance of a nearly related species in many of the African cotton-growing areas, and it was accordingly decided to use the common species infesting glass-houses as a type for investigation with cotton as the food-plant.

From the formation of the Froghopper Investigation Committee in 1925, the chemico-ecological relations of the froghopper have engrossed the greater part of the attentions of the scientific workers on this pest, and a considerable volume of precise knowledge on these lines has been accumulated by Hardy and his colleagues. From representations made by Dr. J. G. Myers, however, the necessity for more strictly entomological work was realised, work which should be “comparable in precision and in extent with that already amassed by the Committee.” The present paper is an account of a part of the work undertaken with this somewhat ambitious end in view. The studies of which an account is given here were commenced in September 1929, but owing to absence on duty abroad, the real beginning of the work did not occur until March 1930.

Blow-flies and house-flies (grouped in the Dipterous family MUSCIDAE in the older sense, including CALLIPHORIDAE) are outstandingly abundant throughout New Zealand. The influence of these insects upon the health of man and domestic animals is well known. Though this work deals with the MUSCIDAE as a whole under local conditions, its main object is to record investigations upon the blow-flies with special reference to the depredations of their maggots upon New Zealand sheep.

Illingworth (1926) published his experiences with Sarcophaga fuscicauda, a fly regarded by him as being of medical importance, and he also suggested it was being transported over the Orient by shipping. There can be little doubt concerning the identity of the fly, this being identical with that published under the same name by Senior-White (1924); both authors included Queensland in its distribution.

1. An analysis of rice-field and canal waters was made over a period of 1 year.

2. The incidence of Anopheles tarsimaculatus in these fields and canals was noted.

3. The chemical factors estimated were pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates, phosphates and ammonia nitrogen.

4. No correlation was found between the incidence of A. tarsimaculatus and the following factors: pH, carbon dioxide, organic nitrogen, dissolved oxygen, nitrites, nitrates and phosphates.

5. In nature the female A. tarsimaculatus seemed to prefer waters with a low ammonia nitrogen content, larvae being rarely found in water with a content greater than 0·04 parts per 100,000. In the laboratory the larvae of A. tarsimaculatus lived several days in waters with an ammonia nitrogen content as high as 0·12 parts per 100,000. Therefore it was concluded that ammonia nitrogen had some bearing upon the prevalence of this Anopheles, affecting the oviposition of the female rather than the growth of the larvae.

(1) It has been assumed that parasites oviposit in their hosts purely at random, not discriminating between healthy hosts and those already parasitized.

(2) Only one Collyria calcitrator can develop in each Cephus pygmaeus so that parasites of this species ovipositing in hosts already parasitized endanger or doom their progeny.

(3) 3,761 larvae of Cephus pygmaeus were dissected; 1,049 were unparasitized and 2,712 were parasitized by Collyria calcitrator; 2,195 contained one, 332 two, 98 three, 49 four, 18 five, 7 six, 4 seven, 5 eight, 2 nine, 1 eleven, and 1 sixteen parasites.

(4) These observed data do not agree, even when corrected for several factors, with the values to be expected from random distribution of the eggs one at a time.

(5) The observed data indicate a degree of discrimination on the part of the ovipositing females.

The so-called short-horned locusts are frequently, for convenience sake, regarded as comprising two classes: the true locusts (Arabic: Girad) and the short-horned grasshoppers (Arabic : Gabura). It is difficult, however, to find definitions of these classes by means of which every species may be correctly assigned to its true place. The swarming habits of the true locust are often cited as connoting this class only, involving, as these habits do, the periodical appearance of excessive numbers of both hoppers and adults. Moreover the true locust is gregarious, in that the hoppers move in bands from one place to another, and the adults fly in vast swarms often over long distances. The fact that the grasshoppers are solitary in habit and manifest mutual independence of action is often taken as their chief distinguishing character. There is no doubt that these features do partly separate these two classes of insects from each other, but there are certain species which appear to occupy a position intermediate between the two. One normally solitary may, in certain circumstances, multiply rapidly and give rise to hoppers, which in certain respects act like those true locusts. Moreover the winged adults may undertake short massed flights resembling the migrations of swarms. On the other hand the fact, now fully established, that most true gregarious locusts have their solitary forms, which never associate, places even them in this respect with the grasshoppers.

The Anglo-Egyptian Sudan has, so far as may be ascertained, always been liable to plagues of the migratory locust, Schistocerca gregaria, Forsk., generally referred to as the desert locust. In the summer of 1930 in addition to this species swarms of another migratory locust, Locusta migratorioides, Rch. & Frm., locally known as the hairy-chested locust, appeared. In most districts natives stated that they had never before seen this second species, but elderly inhabitants of Darfur and northern Kordofan recognised it as having occurred some forty-two years previously for two successive seasons; the first year in large numbers, the second in but small numbers. It was hoped that history would repeat itself and that the hairy-chested locust would be relatively scarce in its second year, but unfortunately this hope has not been realised; L. migratorioides was a more serious plague in 1931 than in the preceding year.

1. Primary fly-belts round Makongo consisted of three different vegetational communities: a Cynometra-Vitex association along the main length of the Makongo river, on a clay soil; a Ficus congensis association along the river close to the town, on a sandy soil; and Isoberlinia doka woodland on moist sandy soil north-west and south of Makongo.

2. Secondary fly-belts of less dense vegetation occur in the orchard bush savannah round Makongo, and these are not colonised until the commencement of the rainy season.

3. Glossina tachinoides and G. palpalis both occurred in the riverside communities, and G. palpalis alone in the Isoberlinia woodland.

4. Along the river G. palpalis outnumbered G. tachinoides by 3:1 in the dry season. At the commencement of the rains G. tachinoides increased more quickly than G. palpalis, bringing their numbers very nearly equal, but at the end of the rains there was a decrease in G. tachinoides which restored the original proportion.

5. G. morsitans had been found at Makongo formerly but was not met with at the time of this investigation, its absence being due to the disappearance of the larger antelope from the neighbourhood.

6. Smaller game animals, small mammals and reptiles afforded an adequate food supply for tsetse in the fly-belts, and also passing herds of cattle, as well as natives from the village and travellers.

7. The distribution of G. palpalis within the fly-belts was markedly influenced by the proximity of a cattle road along which herds of cattle passed almost daily, and by village water-holes.

8. During the dry season the primary foci were always found to be the places of greatest relative humidity, and the fly does not tend to move out of these until the general atmospheric humidity has reached a certain fairly high degree.

9. In clearing the fly-belts the removal of all primary foci within a quarter of a mile of the town and of thick bush within 100 yards of water-holes was undertaken. The work lasted from the beginning of February to the end of March 1931.

10. The effect of clearing the Isoberlinia doka woodland was to banish G. palpalis completely, and it never returned to these clearings.

11. On clearing the riverside Ficus congensis fly-belt, G. tachinoides was practically eliminated for the first three months, but reappeared in the clearings in June when there was a general increase and up-stream migration of this fly. G. palpalis remained in this clearing in fluctuating numbers up to June, when observations were suspended.

12. 565 marked tsetse were liberated in the fly-belts immediately previous to clearing. Of G. palpalis 12·7% were recaptured in the clearings and 11% outside the clearings. Of G. tachinoides 5·5% were recaptured in the clearings and 6·8% outside.