Experiments were conducted to investigate oviposition and host selection by Stenobracon deesae (Cam.), a Braconid parasite of certain Lepidoperous borers of sugar-cane, maize and sorghum in India. The fecundity and sex-ratio of this parasite and the duration of its life-cycle were also studied.

Chilo zonellus (Swinh.) and Corcyra cephalonica (Staint.) were used as hosts. The former is one of the principal hosts in the field, but the latter is not normally a host of this parasite.

The femal Stenobracon normally avoids laying eggs on hosts that are already parasitised by its own kind when unparasitised hosts are available; but in the absence of healthy hosts or when these are too crowded, parasitised hosts are attacked by it.

At a temperature of 26°C. and relative humidity of 75 per cent., the life-cycle of the parasite was completed, on an average, in 23·3 days, but under laboratory conditions at Delhi it took 14·1 days in June-July and 43·7 days in November-December. The average duration of adult life of females in June-February, mainly in ordinary laboratory conditions, was 35·7 days, and single females lived as long as 122 and 128 days. The adult male lived for 42·7 days on the average.

In the laboratory, the female lays about 24 eggs on an average, but only about one-third of them yield adults.

Males predominate. The sex-ratio appears to vary according to the host; among adults reared on Chilo larvae, 28·8 per cent. were females, but among others reared on Corcyra larvae, only 6·2 per cent. were females.

The phenomena of discrimination between parasitised and unparasitised hosts and of the change of sex-ratio with change of host are discussed. It is suggested that the ovipositor enables the parasite to recognise the host and that the stimuli received by the ovipositor from the host influence the functioning of the spermatheca which in turn controls fertilisation and finally the sex of the progeny.

The biology of Pullus impexus (Muls.), a Coccinellid beetle predacious on Adelges piceae (Ratz.) in Switzerland, Germany and France, was studied during 1950–1952. The present work is a part of the research on the complex problem of factors in the control of the Balsam Woolly Aphid in Canada.

The morphology of both the larva and the adult has been studied. Some information has been provided on the probable distribution of the species.

P. impexus has only one generation a year. The eggs are deposited during the late summer or early autumn on infested trees and the larvae hatch in April. The larvae develop and adults appear in May. The adults of the new generation are to be found in June together with adults of the old generation. In the biology, particular attention has been directed to the diet of the insect in each of its stages, in order to establish the value of the species from the standpoint of biological control.

Two new species of Hymenopterous parasites were found in Switzerland and in Germany, Scymnophagus mesnili Ferr., a parasite of pupae, and Centistes scymni Ferr., a parasite of the imagines. The life history of these species has been briefly studied. A cephaline gregarine species was noted in the mesenteron of adults of P. impexus and a nematode in the abdominal cavity of a female. The two Hymenopterous species provide an important limiting factor in the increase of the population of P. impexus.

An experiment was carried out in a small block of mixed bush in Tanganyika in an attempt to eliminate the two resident species of tsetse fly. Glossina morsitans Westw. and G. suynnertoni Aust., by means of bait cattle treated with DDT. Small cattle were used at the rate of 100 per square mile in herds of 12 or 13 per one-eighth of a square mile. Their numerical superiority over the large game was no more than about 3: 1.

The cattle were sprayed twice weekly. Originally a 10 per cent. suspension of the p.p′isomer was prepared from a commercial formulation of DDT. Later a laboratory-prepared emulsion (10 per cent. technical DDT) was used.

Extermination was expected with a reduction in numbers of old male tsetse of 99·9 per cent. In practice G. morsitans was reduced by 99·5 per cent. and G. swynnerloni by 92·5 per cent.

It is considered that there was sufficient immigration across the barrier clearing to account for the failure to achieve extermination of either species. It is not possible to say if extermination would have been attained in the absence of immigration.

It is considered that with the insecticidal formulations now available there is not much prospect of improving on these results in similar conditions although a great reduction in tsetse numbers is possible and might stop the carrying of disease. In the dry season, after the grass has been burnt, there is better prospect of success.

The biology of Melittomma insulare Fairm. (Coleoptera, Lymexylonidae), a wood-boring pest of coconuts in the Seychelles and northern Madagascar, has been studied from all angles, with the object of discovering practical means of control.

The stages in the life-history are figured and briefly discussed, supplementary details being given to the earlier accounts of Vesey-FitzGerald and others.

The feeding habits of the larvae ae described in some detail, with particular reference to their association with micro-organisms which were almost invariably detected in infested wood surrounding the tunnels. The larva is shown to feed on fluid extracted from the parenchymatous tissues and not on solid wood.

The course of the development of an infestation in an individual trunk is described in detail, culminating in the fall of the palm. Variations in this process are correlated with the age of the palm and other factors. The spread of infestations through plantations and islands is also discussed. A detailed account is given of the symptoms shown by attacked palms, together with a critical revision of certain changes which have in the past been attributed to Melittomma attack.

An account is given of the occurrence of M. insulare in certain palms other than coconuts, in which it has been found.

A series of 32 cloths, including 8 flannels dyed to Munsell standard colours, seven coloured satins and 17 service fabrics, were tested for their attractiveness to northern Canadian Aëdes mosquitos, and were assessed for their reflectivity of visible and ultra-violet light.

Their attractiveness was found to vary inversely with their reflectivity or brightness, although the different textures represented in the series tended to obscure the generalised relationship.

When comparisons were made within a series of identical texture, the correlation was good in the range between 475 and 625 mμ wave-length, but was not present in the red or infra-red, nor in the violet and ultra-violet ranges of wavelength.

Green tended to be less attractive, and white more attractive, than was expected from this relationship. For colour values of similar lightness or darkness, the order of attractiveness to Aëdes punctor and associated species was black, red, blue, brown, green, white, yellow.

Aneityum is the only Pacific island south of Latitude 20°S. from which Anophelines and autochthonous malaria have yet been reported. Both Plasmodium vivax and P. malariae were found there, the former species only being detected in the blood of children who had visited the nearby island of Tanna and the latter in that of children who had never left Aneityum. Autochthonous quartan malaria has not previously been reported from the New Hebrides. In the absence of any other Anophelines from this group, it must be assumed that Anopheles farauti Laveran is the vector of P. malariae at Aneityum.

The red bollworm attacking cotton in Nigeria has recently been shown to be Diparopsis watersi (Roths.), distinct from D. castanea Hmps., the southern African species previously assumed to be that occurring on cotton throughout Africa. Earlier work on cotton pests, including Diparopsis, in southern Nigeria (1664) is briefly reviewed, and the discovery and definition of the problems of cotton pests in northern Nigeria is outlined, and the climatic and agricultural background of the northern areas described.

The main object of the present work, centred at Samaru, was to determine; the annual cycle of activity of Diparopsis in northern Nigeria. The methods employed are described. The insect passes the dry season in diapause as a pupa in the soil. In late May or June, emergence from these pupae commences, but this is completely interrupted during July-September. In October, after the end of the rains, emergence recommences, and the main attack occurs on the crop during October and November. The proportion of pupae entering diapause rises rapidly from mid-October onwards, and activity ceases in early December.

When diapause pupae were incubated at controlled (86°F.) or indoor air (74–86°F.) temperatures, emergence was unimodal, extending from June to October, with the peak in July or August, respectively. It is concluded that the bimodal emergence in the field is caused by waterlogging, or some other factor restricting aeration of the soil during July-September, when the emergence from diapause pupae is interrupted

Trials of dates of sowing laid down at Samaru and Daudawa showed that early sowings, made in mid-June or early July, may suffer heavier bollworm attack than those made in mid- or late July. The earlier sowings nevertheless outyielded later ones. It is suggested that this results from their benefiting from a longer growing season, in which a greater production of fruiting points more than offsets greater losses from bollworms and other insects.

Elimination of ratoon and standover cotton would prevent breeding by the early emergence of moths from diapause pupae, and consequent red-bollworm attack on early sowings of cotton.

The possibility of producing a unimodal emergence from diapause pupae is worth further attention. This might be achieved by altering the soil conditions during July-September, and if successful would result in the main crop escaping almost entirely any attack by Diparopsis.

There appear to be no fundamental differences biologically between Diparopsis castanea and D. watersi, as illustrated by previous work reported from South Africa and Nyasaland, and the observations recorded here.

Aëdes (Stegomyia) polynesiensis Marks, Culex (Culex) pipiens fatigans Wiede-mann and Culex annulirostris Skuse were collected at Aitutaki, Southern Cook Islands, during a brief visit in 1958. Possible means of introduction of these mosquitos are discussed.

An investigation has been made of the deposition in open country of a coarse aerosol released from an aircraft flying at approximately 30 feet. A constant drop spectrum was used, with a mass median diameter of approximately 80 microns.

It is shown that the rate at which the aerosol deposits is greatly affected by the degree of atmospheric turbulence, a practical measure of which is described. The rate of deposition is approximately inversely proportional to the time interval elapsing between production of the aerosol and deposition, except for deposits laid down near the line of emission.

Droplets less than 10 microns in diameter are not deposited appreciably within any useful time interval, and it would be most uneconomical to attempt to produce deposits upon the ground by using drop spectra consisting mainly of such small droplets.

The solution used was a 10 per cent. w/v solution of technical DDT in a solvent consisting of 1 part of Shell Power Kerosene to 1 part of Shell Diesoline. Evaporation of the volatile constituents takes place very rapidly during the first few seconds after production of the droplets, and deposits formed immediately beneath the aircraft track have lost 50 per cent of their initial volume. Solvent losses increase significantly with time, but so slowly that for most practical purposes the solution strength of the ground deposit is very nearly constant for all important sampling points.

The mosquito fauna of New Caledonia and the Belep Islands is discussed, together with some features of the larval morphology of Culex (Culex) pipiens fatigans Wied., C. (C.) annulirostris Skuse and C. (Neoculex) pseudomelanoconia Theo. Culex (C.) bitaeniorhynchus Giles, herein recorded from New Caledonia for the first time, is probably a post-war introduction into the Noumea area from Australia. Culex (Lophoceratomyia) fraudatrix Theo., recorded from Art Island (Belep group), has not previously been known from the New Caledonian area. From the mosquito and blood-smear survey in the Belep Islands, it is concluded that these islands, like New Caledonia, are as yet free from Anopheles and malaria.

The life-history and bionomics of the Coreid bug, Theraptus sp., which causes premature nutfull of coconuts in Zanzibar, were studied in the laboratory and in the field.

From the various experiments carried out it is concluded that:—

The development of the insect from the egg to the adult took from 26–39½ days depending on temperature and the food available.

The average length of life of the female is 45 days during which time she may produce over 100 fertile eggs.

The primary host-plant of Theraptus is the coconut palm, but the bug readily infests mango, guava, cinnamon and cacao trees when they are fruiting.

The pest will attack and develop successfully on nuts from the newly emerged to the mature ones.

Agents which exert a measure of biological control include the tree-nesting ant, Oecophylla longinoda (Latr.), an internal Strepsipteran parasite, an unidentified Reduviid, two unidentified Hymenopterous egg-parasites and possibly some small ant species which prey on the eggs. Of these, only the ant, O. longinoda, is capable of giving complete protection to the palm which it occupies.

The work described in this paper has been carried out with two proprietary samples, designated Systox 50 emulsion and E 1059, of a systemic insecticide of which the active ingredient, subsequently referred to throughout as Systox, is a mixture of O,O-diethyl O-ethylmercaptoethyl thiophosphate and its isomer, O,O-diethyl S-ethylmercaptoethyl thiophosphate.

The samples were tested against Aphids for contact and systemic action.

It is concluded that, as a contact insecticide against Aphis fabae Scop, on broad beans, Systox is about equitoxic with paraoxon and so more toxic than schradan and dimefox.

Systox is readily absorbed by the roots of broad bean and cabbage plants from soil, sand and aqueous solutions and the translocated material is very effective as an insecticide against A. fabae on broad bean, and Myzus persicae (Sulz.) and Brevicoryne brassicae (L.) on cabbage.

Applied in this way, Systox is more effective than schradan, dimefox and paraoxon, and about equal to the most toxic compound previously tested, sodium fluoroacetate.

An experiment by the cut tap-root technique confirms these conclusions. A dose of 1 mg. of Systox per kg. of fresh bean-plant tissue gave a complete kill of A. fabae by the 10th day. The same amount of sodium fluoroacetate had previously been shown to give a complete kill in three days.

The plants were carefully watched for signs of damage during the tests. It was concluded that there was a considerable margin between the insecticidally effective and the phytotoxic concentrations.

Systox is also translocated from older to younger leaves of bean and cabbage plants and it may reach concentrations sufficient to kill the Aphids feeding on the untreated leaves. This effect was more consistently obtained in the broad bean than in cabbage plants. In both cases, however, the results were variable.

Solutions of Systox exert a direct fumigant action on Aphids, but there is little evidence that toxic material is transpired by treated plants.

Five experiments in the use of insecticides against Calandra oryzae (L.) in stored maize are described. The results with statistical analysis and deductions are given. The insecticides used were BHC, DDT, pyrethrum, pyrethrin-piperonyl butoxide mixtures; the diluting dusts used were a local diatomite, a local bentonitic clay, and a local soapstone.

Among the chief conclusions are the following:—

The insect damage in conditioned grain did not reach, throughout an eight-month period, the high level which it did in unconditioned grain, the conditioning process alone therefore is a valuable treatment for insect control.

Bentonite alone is not a protectant and its addition to grain may on the contrary provide a more favourable environment for Calandra.

A Kenya soapstone (from Kisii) is not an effective protectant but had some effect in reducing Calandra populations over the period when an initial increase was occurring in control bags.

Kenya diatomite is a protectant. It reduces the percentage of grain damaged, but when used in bagged grain this is not proved to be due solely to intrinsic toxicity, but may in fact be due chiefly to the slippery nature of the material inhibiting insect distribution through the bulk of grain.

Gamma BHC at 1 p.p.m. is completely effective for 16 months.

Gamma BHC at 0.5 p.p.m. has some protectant effect but is not fully effective.

DDT at 7 p.p.m. has not a protectant effect.

In British East Africa Oecophylla longinoda (Latr.) var. textor Santschi is locally common in the costal region. Inland it is absent from higher altitudes and from areas where there is a pronounced dry season.

In Zanzibar Island, O. longinoda at least 89 species of trees and shurbs; the largest populations occur on the clove (Jambosa caryophyllus), Citrus spp., Bridelia micrantha and Canthium zanzibaricum.

The nesting habits and colony composition of O. longinoda are such that one colony may spread over a number of adjacent trees; it contains only one gravid queen.

Winged virgin sexual forms are released at the beginning of the wet seasons and new colonies are initiated by a single queen, who uses her food reserves to bring the first batch of brood to maturity.

In Zanzibzr, O. longinoda tends a wide range of Homoptera that produce honey-dew, but apparently “ prefers ” certain Coccids, notably Saissetia spp.

The degree of attention afforded by an ant species determines the species of Homoptera which it is able to attend.

The insect species preyed upon by O. longinoda include the honey bee, Apis mellifera, and the driver ant, Dorylus nigricans, of which large numbers may be destroyed.

O. longinoda is of undoubted value for controlling certain coconut pests, notably Theraptus sp. (Coreidae), and its efficiency in coconut plantations could probably be much enhanced.

Theraptus sp. from Zanzibar, Pemba and Tanganyika have been inter-bred.

Individuals of the F1 generation are fertile, but a partial sterility in some crosses may exist.

It is concluded that there is only one species but possibly three varietal strains.

The mixture of O, O-diethyl O-ethlmercaptoethyl thiophosphate and O, O-diethyl S-ethylmercaptoethyl thiophosphate, known as Systox, which has been previously tested against Aphids, has now been tested as a systemic insecticide against the eggs and larvae of Pieris brassicae (L.) and the eggs, larvae and adults of Phaedon cochleariae (F.).

Systox is toxic by direct contact to all stages of these insects but is much less effective in this way than diethyl p-nitrophenyl phosphate (paraoxon).

As a systemic insecticide applied to the roots of teh host-plant, Systox again acts on all stages of the insects (except the eggs of Phaedom), but, compared with the dose which killed Aphids, about twice as much is required to kill Phaedon larvae and between 20 and 100 times as much to kill Pieris larvae, depending on the method employed.

When applied systemically Systox, like paraoxon, can prevent the emergence of Pieris larvae from the eggs.

Field observations on the Culicidae of Sardinia and Corsica were undertaken in 1944, during the period 1946 to 1950, and again in 1952. A total of 52 species are recorded as being present, 46 of which are known from Corsica and 35 (exclusive of Dixinae) from Sardinia. The faunal list of the latter island has been increased by 20 new records and that of Corsica by three. The total number of species by genus is as follows: Dixa (7), Chaoborus (3), Anopheles (12), Uranotaenia (1), Culiseta (6), Orthopodomyia (1), Taeniorhynchus (2), Aëdes (12), and Culex (8).

The previously unknown male of Taeniorhynchus buxtoni Edwards is described from Sardinian material. Culiseta litorea (Shute), heretofore known only from England, was found in two localities in Sardinia. Aëdes vittatus (Bigot) was rediscovered in Corsica, 83 years after its original description.

Keys are given to subfamilies, genera and species. Critical notes on species differentiation are included and biological characteristics briefly discussed.

A close association exists between the ant Oecophylla longinoda (Latr.) and the scale insect Saissetia zanzibarensis Williams.

Several factors cause the scale to be rare in the absence of the ant. Contamination by honey-dew and sooty moulds prevents increase of the S. zanzibarensis population above a relatively low level, while, in addition, insect parasites and probably predators virtually exterminate the scale. A fungal parasite may destroy honey-dew-contaminated S. zanzibarensis under humid conditions.

The attendant O. longinoda prevents contamination of the scale by honeydew. It gives absolute protection from Coccinellid predators and, although parasitism by Coccophagus spp. and predation by Eublemma spp. is not prevented, the mortality of S. zanzibarensis which they cause is thought to be of little significance.

O. longinoda workers benefit S. zanzibarensis in other ways. They remove débris from the scale clusters; they transport the nymphs and establish them at suitable feeding sites. The effect of these benefits is most marked when the ant population is high relative to that of the scale.

The silken shelters built by O. longinoda over S. zanzibarensis clusters protect the ant during adverse weather and may only incidentally benefit the scales.

S. zanzibarensis and other honey-dew-producing Homoptera are the major food source for O. longinoda. Other sources are sufficient to maintain only relatively low populations of the ant.

Specimens of the first of the new species here described were received by the Commonwealth Institute of Entomology from Mr. G. Swaine, Entomologist to the Department of Agriculture, Tanganyika Territory, who reported it as injurious to shoots and young fruits of the cashew nut, Anacardium occidentale L., and of the second through the British Museum (Natural History) from Mr. G. S. Dun, Senior Entomologist, Division of Plant Industry, New Guinea.

A method is described for rearing Drosophila melanogaster Mg., which provides a high and consistent yield of adult flies, of uniform age and size, for insecticide studies.