In several previously published papers dealing with African Diptera I have described a number of species belonging to the genus Sturmia, Desvoidy, but up to the present time have not had sufficient material available to warrant the preparation of a key to the species, nor have I had an opportunity of studying the species in sufficient detail to decide upon characters of value in their classification. However, since many species were reared and it was desirable to have names for them in order that they might be used in reports by various Entomologists in Africa, a number of the species were described, and it has since been possible to make considerable progress in the study of the whole. As a result a key to the species belonging to this genus is now presented, and it is hoped that it will be of assistance in identifying the representatives of this difficult group.

It is further hoped that arrangements may be made in the near future for the publication of a key to the genera of the Tachinidae, since it is obvious that with the very large number of genera described, the description of an additional genus, or even of new species in old genera, conveys little of the true relationships of the forms described and merely adds to the difficulty of making determinations.

Poeciloscytus cognatus, Fieb. (fig. 1) has already been recorded as injuring sugar-beet in Ukraine. In the summer of 1926 an enormous number of these bugs appeared quite unexpectedly in the districts of Poltava and Kharkov and caused great losses. Much attention has been given to methods of control on the plantations, but the following information is only of a preliminary nature and refers partly to the phenology of the insect.

In view of the fact that many blood-sucking Diptera are carriers of pathogenic micro-organisms of animals and human beings, the study of the structure of their mouth-parts has attracted the attention not only of zoologists but of medical men as well.

During the years 1925–7 an investigation was made of the Culicine mosquito fauna of Singapore, mainly with the object of learning which species were responsible for the local mosquito plague, and where they bred. In the course of this work numerous species were reared, the larvae of which have never been described, and descriptions of these are presented in this paper; these are supplementary to the descriptions published recently by Edwards (Bull. Ent. Res. xvii, pt. 2, 1926).

During the last few years a number of papers have been published by entomologists in connection with the hypothesis known as the “ Hopkins host-selection principle.” This principle, as defined by Dr. A. D. Hopkins himself, is that an insect species that breeds in two or more hosts will continue to breed in the host to which it has become adapted. Thus, according to this author, the mountain pine beetle, Dendroctonus monticola, will destroy mountain pine, yellow pine, lodgepole pine and sugar pine, but if it becomes established in one species of pine through many generations, the beetles on emergence show a decided preference for the species in which they have bred and will not, in fact, attack any other. In 1922 Craighead published a paper giving the results of experiments carried on during a number of years with about a dozen species of Cerambycids. He states that in practically all the species studied the adults show a marked predilection for the host in which they have fed as larvae, provided that they are not deterred by other factors. Continued breeding in a given host is said to intensify the preference for that host. With some beetles whose larvae can be transferred to another species of plant and successfully reared therein, this association with the new host for a year, or even less, during the latter part of the larval life is said to determine a preference for this in the resulting adults. The author believes that his experiments may indicate the mode of origin of certain closely related species or varieties. The conclusions at which he has independently arrived were long ago suggested by Walsh. That new forms do not thus arise more rapidly in Nature, Craighead considers to be due to the high mortality of the young larvae in the new hosts.

The present paper deals with a small collection of Tachinidae received from Mr. H. Hargreaves from Uganda, together with other material of the various species forwarded by the Imperial Bureau of Entomology. The types of the new species, unless otherwise stated, will be deposited in the British Museum of Natural History.

Aëdes argenteus, Poiret, is a very variable mosquito, and it was thought that it would be interesting to examine a number of freshly-hatched and therefore undamaged specimens and to note how many conformed to the original description. No difficulty was experienced in obtaining the necessary material, as collections of larvae are received daily from the Medical Officer of Health. One thousand of each sex of the species were mounted in the order of their emergence from the pupal case and were examined under the binocular microscope. The one constant feature was found to be the lyre-shaped marking on the thorax, although even here the outline and the centre lines varied in breadth and in colour, and the centre lines varied in length. But as the abdomen and the hind tarsus showed the greatest variations, the present paper is restricted to a description of these.

There are three main parasitoids and one very efficient predator associated with Perrisia pyri in France. Of these, at least during July and August, the predacious Capsid, Pilophorus perplexus, achieves the greatest destruction of midge larvae.

The two species of Platygasterids differ in several points of ethology from the species of the same or adjacent genera attacking Contarinia pyrivora. They are both egg-parasites, developing very slowly in the midge larvae during the growth of the host. Their action appears to be largely complementary, corresponding to morphological differences in the organs of oviposition. Their life-history is very imperfectly known.

Torymus abbreviatus is extremely efficient. Its eggs are laid within the curled leaf among well-grown midge maggots on which the larva lives as an ectoparasitoid. The duration and location of the pupa stadium is unfortunately not yet known.

Some half a dozen other enemies were found to play a less important part than the preceding.

The following article includes the results of observations on the number and species of mosquitos breeding in two tree-holes during a period of more than ten months.

The importation of parasites from the native home of introduced insect pests now constitutes a recognised part of entomological practice in most countries under civilised control. However, since the method is still in the experimental stage, and since long periods of time often elapse before the parasites colonised become sufficiently abundant to exert any appreciable influence on the host, the entomologist often finds it necessary, in order to avert disaster, to utilise remedies which, though temporary, are more immediately effective. To this end he employs some one or other of the various methods of mechanical control, by which the population of the insect pest can be at once greatly reduced.

But in many cases, these methods of attack affect the parasites as well as the hosts. It is therefore important to consider what influence they will have upon the progress of the natural enemies and whether, in order to obtain the temporary relief afforded by mechanical methods, we are not sacrificing the hope of permanent control.

We have at present no data permitting us to attack this problem from the experimental angle ; but it can be studied in a broad general way when reduced to mathematical terms.

(1) During studies on the mosquito breeding occurring in tree-holes in the vicinity of Lagos, Nigeria, water was collected from holes in 260 trees. This number included 36 species, consisting largely of fruit trees and those used for shade and ornamental purposes.

(2) Mosquito larvae were present in samples of water taken from 227, or 87·3 per cent., of the trees.

(3) The number of adult mosquitos bred out from all larvae collected totalled 12,285, with 14 species represented.

(4) Among the several species, Aëdes aegypti stood second in the number of trees in which it was found and fourth in the number of adults bred out.

(5) Aëdes aegypti larvae were taken from holes in trees at a distance of 350 yards from the nearest habitation.

(6) The amount of breeding of Aëdes aegypti found occurring in tree-holes was sufficient to demonstrate their importance as a source of mosquitos of this species and the necessity for their elimination as a measure in yellow fever control.

While engaged as entomologist to the Central Aguirre Sugar Company, owners of some 12,000 acres of sugar-cane lands situated on the south coast of Porto Rico, the writer continually recommended the importation into that island of certain larval parasites of Diatraea saccharalis, Fabricius (sugar-cane moth borer), as the one species indigenous to Porto Rico—Lixophaga (Euzenilliopsis) diatraeae, Townsend (Tachinidae)—alone, does not effect a sufficiently high percentage of control of the island's major sugar-cane pest.

The examination of a collection of fleas, obtained during the last two years in the course of the investigation of plague amongst the rodents of the South African veld, has resulted in the finding of three new species of Xenopsylla, which are described below.

My thanks are again due to Dr. K. Jordan and to Dr. G. A. K. Marshall for advice and help kindly given to me.

During the past few months the writer conducted observations to determine, first, if Aëdes aegypti preferred places of oviposition within habitations or those located outside with natural shelter near by, and, second, the distance from human habitations at which this species may breed. These investigations were carried out in, or near, the compound of the West African Yellow Fever Commission at Yaba, near Lagos, Nigeria.

The khapra beetle, Trogoderma granarium, Everts 1898, has been referred to in recent years as Trogoderma khapra, Arrow, and Attagenus undulatus, Mot. Investigations on the pest have been carried out by Barnes & Grove (1) in India, and by Dendy & Elkington (2), Mason (3), Parker & Long (4), and Morison (5) in England.

During the six-month period from December 1925 to June 1926, some observations were carried out on the mosquito breeding that occurred in a number of “ test ” water-containers placed in various locations in the compound of the headquarters of the West Africa Yellow Fever Commission at Yaba, near Lagos, Nigeria. The main purpose of these observations was an endeavour to obtain supplemental information on the bionomics of the yellow fever mosquito, Aëdes (Stegomyia) aegypti, Linn., in West Africa.

The specimens which form the basis of the following notes and descriptions were received by the writer from Mr. T. H. Colebrook Taylor, Assistant Entomologist, Fiji Islands, and were reared by him in the course of investigations looking to the introduction into the Fijis of parasites of Coccidae for the purpose of controlling the scale pests of coconut. One genus, two species and a variety are described as new.

(1) An effort has been made to find an explanation for certain problems involved in the selection of breeding-places of mosquitos in Queensland.

(2) Many of these problems must remain unsolved until it is possible by patient study of local conditions to bring all the factors involved into play.

(3) In order to explain the reason for the avoidance of natural water, where it exists, it is suggested that the soils that underlie them should first be taken into consideration, and that the waters should be examined with reference to their physical and chemical conditions.

(4) Observations and experiments, spread over a period of eighteen months, confirm the findings of previous authors that Characeae do not in themselves possess larvicidal properties.

(5) That food is the main determining factor in the choice of preferential breeding-places seems to be borne out by actual results obtained, and that when such are not available, mosquitos will resort to breeding-places of compulsion, such places being usually observed to be entirely or partly devoid of food supplies.

(6) It is suggested that the salts of alumina and iron in the ferrous state tend to destroy food organisms, and that where these conditions exist, the water is not selected preferentially.

(7) The presence of algae leads to the appearance of Anopheles annulipes.

(8) That Cladophora holsatica inhibits larval growth seems to be experimentally established.

(9) Bacterial scums are mainly due to B. subtilis and have a tendency to produce a slight alkalinity.

Blosyrus aequalis, Har. 1879.

This species, originally described from Angola, has recently been bred from larvae found in tubers of sweet potatoes at Haut-Lepori, Belgian Congo, by Lieut. J. Ghesquière.

During two years (1924 and 1925) spent in Samoa by Dr. P. A. Buxton and myself, while employed in research on filariasis for the London School of Hygiene and Tropical Medicine, we made notes of such agricultural pests as came our way, though (our main interests being medical) we were not able to investigate them at all thoroughly. For this reason the fact of an insect being recorded only on one occasion is no indication that it did not occur in other months, or even that it was uncommon, since we frequently did not continue to make notes of the occurrence of a species we had once recorded. Though our observations make no claim to completeness, they are perhaps worthy of publication in view of the scarcity of records from this group of islands. Our observations on medical and veterinary entomology have been published as a Memoir of the London School of Hygiene and Tropical Medicine. In that Memoir we have published maps, and short accounts of the structure, flora and climate, of Samoa.