Some types of joint action of insecticides described by previous authors are discussed, and experiments described on the joint action on Periplaneta americana (L.) of the γ and δ isomers, and of the γ and α isomers, of benzene hexachloride. The values of the mortalities obtained are given in tables and compared with calculations of those that would be expected according to several models of joint action in which no interaction occurs. From statistical evidence it is concluded that only one of these models, namely, independent action with a strong positive correlation of the susceptibilities to the two poisons, can give an appropriate explanation of the results. These results, however, can also be explained by suggesting that antagonistic effects play a part in the joint action of the BHC isomers investigated.

Fourth instar larvae of a new strain of Culex quinquefasciatus Say from Tanzania (TANGA) were tested for insecticide resistance. Initially, the resistance ratio (RR) to chlorpyrifos was 41.8, to temephos 30.8, to propoxur 3.7. After 2–3 years of laboratory culture, resistance to chlorpyrifos and propoxur had declined (chlorpyrifos 5.7, 3.8; propoxur 1.9, permethrin 1.9). Significant synergism was found between s, s, s-tributyl trithiophosphate (DEF) and chlorphyrifos, reducing the RR from 8.0 to 2.5. Synergism between piperonyl butoxide and permethrin was less than in a susceptible control strain. Twelve esterase isozymes of different relative mobilities (Rm) on polyacrylamide gel electrophoresis were identified, ten of which remained when the strain was reinvestigated two years (approximately 32 generations) later. Null activity for all but one of these bands was observed in some larvae. Four esterase bands (Rm 0.25, 0.27, 0.31, 0.34, designated A2, A3, B2, B3) showed polymorphism in activity, with very intense bands in some larvae. The mean frequency of bands with activity greater than standard, declined as organophosphorus (OP) resistance declined, but resistance was unconnected with the frequency of nulls at these positions. In mass larval assays of in vitro sensitivity of acetylcholinesterase (AChE) to propoxur, the I50 exceeded 10x10−4M, compared with 0.1x10−4M in a reverted resistant strain (RANGOON). Single larvel assays revealed heterogeneity, which was interpreted on the basis of an AChE resistance allele (AceR) with a frequency of 0.23.

When carrying out an investigation into the mosquitos of New Zealand, * the writer found that a very common species bred in saline and semi-saline pools above high water mark along the rocky parts of the North Island coast line. For some time it was considered that this mosquito was unrecorded, but it appears that Hutton described it as a Tipulid under the name Opifex fuscus.† This was pointed out to me both by Mr. G. V. Hudson, of Wellington, who is in possession of Hutton’s Tipulid types and had seen the illustrations here reproduced, and later on by Mr. F. W. Edwards, of the British Museum, who published a short account of the insect from material recently sent to him by Mr. Hudson.‡

During recent years a great deal of research work has been carried out in connection with the control of the black currant gall mite Eriophyes ribis (Westw.) Nal. This work has necessarily included the very careful study of the mites themselves, in order that the life-cycle might be fully understood, with the final object of trying to exterminate the mites at a period when they offered least resistance and were not living within the buds, which afford them adequate protection.

While examining some black currant bushes in the late spring and summer months of 1923, in order to locate the position and determine the habits of the mites during that season, a rather peculiar form of mite was noticed to be present in small numbers. This new mite, when examined in the field, appeared to be very much stouter and of a darker colour than the familiar black currant gall mite. However, for some time it was regarded as being an immature stage of the common species. After some months this mite turned up again in greater numbers, and it was decided to examine it in detail in the Laboratory. The species proved to be a new one belonging to the genus Phyllocoptes.

Among a number of insects sent in for identification by Dr. J. J. H. Szent-Ivany, of the Department of Agriculture, New Guinea, were several species of weevils that are reported as causing serious injury to cacao and coffee plants. Four of these are described below, and the types have been deposited in the British Museum (Natural History).

The white-backed planthopper, Sogatella furcifera (Horváth) (Hemiptera, Delphacidae), has emerged as a serious rice pest in Asia. In the present study, 12 microsatellite markers were employed to investigate the genetic structure, diversity and migration route of 43 populations sampled from seven Asian countries (Bangladesh, China, Korea, Laos, Nepal, Thailand, and Vietnam). According to the isolation by distance analysis, a significant positive correlation was observed between genetic and geographic distances by the Mantel test (r2 = 0.4585, P = 0.01), indicating the role of geographic isolation in the genetic structure of S. furcifera. A population assignment test using the first-generation migrants detection method (thresholds a = 0.01) revealed southern China and northern Vietnam as the main sources of S. furcifera in Korea. Nepal and Bangladesh might be additional potential sources via interconnection with Vietnam populations. This paper provides useful data for the migration route and origin of S. furcifera in Korea and will contribute to planthopper resistance management.

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.

Tools that could be used to subvert the insect diapause response offer potential for insect pest management as well as for the experimental manipulation of insects and the facilitation of mass rearing procedures. In some cases, it is desirable to break diapause on demand and in other cases, it may be attractive to exploit diapause for long-term storage of biocontrol agents or valuable experimental lines. This review highlights some of the diapause disruptors reported in the literature, as well as chemical and physical manipulations that can be used to extend diapause or even induce diapause in an insect not programmed for diapause. The insect hormones are quite effective agents for breaking diapause and in some cases for extending the duration of diapause, but a collection of other chemical agents can also act as potent diapause disruptors, e.g. organic solvents, weak acids and bases, carbon dioxide, imidazole compounds, LSD, deuterium oxide, DMSO, ouabain, cholera toxin, cyclic GMP, heavy metals, and hydrogen peroxide. Physical manipulations such as artificial light at night, anoxia, shaking and heat shock are also known diapause disruptors. Some of these documented manipulations prevent diapause, others terminate diapause immediately, others alter the duration of diapause, and a few compounds can induce a diapause-like state in insects that are not programmed for diapause. The diversity of tools noted in the literature offers promise for the development of new tools or manipulations that possibly could be used to disrupt diapause or manage diapause in controlled laboratory experiments and in mass-rearing facilities.

Insect crop pests are a major threat to food security in sub-Saharan Africa. Configuration of semi-natural habitat within agricultural landscapes has the potential to enhance biological pest control, helping to maintain yields whilst minimising the negative effects of pesticide use. Fall armyworm (Spodoptera frugiperda, J. E. Smith) is an increasingly important pest of maize in sub-Saharan Africa, with reports of yield loss between 12 and 45%. We investigated the patterns of fall armyworm leaf damage in maize crops in Ghana, and used pitfall traps and dummy caterpillars to assess the spatial distribution of potential fall armyworm predators. Crop damage from fall armyworm at our study sites increased significantly with distance from the field edge, by up to 4% per m. We found evidence that Araneae activity, richness and diversity correspondingly decreased with distance from semi-natural habitat, although Hymenoptera richness and diversity increased. Our preliminary findings suggest that modifying field configuration to increase the proximity of maize to semi-natural habitat may reduce fall armyworm damage and increase natural enemy activity within crops. Further research is required to determine the level of fall armyworm suppression achievable through natural enemies, and how effectively this could safeguard yields.

Distortion, a severe stunting and deformation of plants of guineacorn (Sorghum vulgare) in Northern Nigeria, has been shown to be caused by Heterococcus nigeriensis Williams feeding on the plants.

The symptoms are striking; affected stems are much shorter and wider than normal and leaves are mis-shapen, with irregularly divergent veins and white tissue between the veins. Symptoms in the field vary from small patches of distortion on other normal plants to whole plants affected. The abnormal leaves of a plant with severe distortion are crumpled and remain rolled together. Growth of the plants virtually ceases if the mealybug infestation continues but, in the absence of mealybugs, affected plants recover and produce normal leaves.

Distortion has been found in the field, commonly on Sorghum vulgare, Zea mays and Cynodon dactylon, and once only on Pennisetum typhoides and Chloris pycnothrix, respectively, and has been produced experimentally on Z. mays, C. dactylon, P. typhoides, Triticum aestivum, Oryza sativa and Digitaria exilis by transferring mealybugs from affected guineacorn.

An experiment was carried out in 1968 in the Lossitete Forest area of northern Tanzania to compare the fly-round and the Langridge-trap as sampling techniques for assessing the effectiveness of 0·4% pyrethrum applications on Glossina pallidipes Aust. when applied from the air. From fly-rounds, population reductions of 64%, 36% and 29% after the first, second and third applications, respectively, were estimated, whereas from Langridge traps the reductions were 11%, 7% and nil, respectively. Taking into consideration the efficiency of the Langridge-trap and the limitations of the fly-round in sampling G. pallidipes populations, it is concluded that the fly-round may give a false assessment of reduction of G. pallidipes after insecticide application.

A new species of scale insect from coconut trees in Trinidad is described and named Parlagena bennetti. The generic assignment is tentative. A key to the four known species of Parlagena is provided.

A photographic apparatus is described for obtaining a record of oviposition and larval eclosion at intervals through the night. By the use of electronic flash a negative silhouette image is produced and the method used does not appear to disturb the moths during oviposition. A second apparatus incorporating a moving pen is also described for studying and recording the times of emergence of moths from their pupae.

Length of body (one male), 2·3 mm.; length of wing, 1·6mm.; greatest breadth of wing, 0·5 to 0·6 mm. A large, dark brown species resembling C. nigripennis, C.I. & M.

In the autumn of 1931 I received for determination from Dr. R. B. Jackson a small number of Culicine larvae collected in Hong Kong. These included two specimens of a Uranotaenia with very remarkable antennae, which seem well worth describing as a further example of the striking and unexpected deviations of structure which occur in various members of this genus. As the specimens sent were whole larvae and not skins, the identity of the species is somewhat uncertain, but an adult of U. testacea, Theo., was obtained by Dr. Jackson at the same time as the larvae, and it is most probable that the larvae belong to that species. Incidentally, U. testacea has not been recorded from Hong Kong before.

The majority of plant viral disease is transmitted and spread by insect vectors in the field. The small brown planthopper, Laodelphax striatellus (Fallén), is the only efficient vector for rice black-streaked dwarf virus (RBSDV), a devastating plant virus that infects multiple grain crops, including rice, maize, and wheat. Adenosine triphosphate (ATP)-binding cassette (ABC) transporters participate in various biological processes. However, little is known about whether ABC transporters affect virus infection in insects. In this study, RBSDV accumulation was significantly reduced in L. striatellus after treatment with verapamil, an effective inhibitor of ABC transporters. Thirty-four ABC transporter genes were identified in L. striatellus and expression analysis showed that LsABCF2 and LsABCG9 were significantly upregulated and downregulated, respectively, after RBSDV infection. LsABCF2 and LsABCG9 were expressed during all developmental stages, and LsABCG9 was highly expressed in the midgut of L. striatellus. Knockdown of LsABCF2 promoted RBSDV accumulation, while knockdown of LsABCG9 suppressed RBSDV accumulation in L. striatellus. Our data showed that L. striatellus might upregulate the expression of LsABCF2 and downregulate LsABCG9 expression to suppress RBSDV infection. These results will contribute to understanding the effects of ABC transporters on virus transmission and provide theoretical basis for virus management in the field.

The recent attack by Pulvinaria iceryi (Sign.) on sugar-cane in Mauritius is discussed in the context of other attacks by sap-sucking Hemiptera in the Mascarenes. P. iceryi is compared with its allies P. elongata Newst., P. saccharia DeLotto, P. sorghicola De Lotto and P. tenuivalvata (Newst.). The name of P. longisqua De Lotto is sunk as a synonym of P. elongata and a key is presented for the five related species.

This subject has been discussed very fully by Dr. T. A. M. Nash and the writer in two recent papers (Bull. Ent. Res. 24, 1933, pp. 135, 475–477). There is, however, one point which it is felt should be made clear. Dr. Nash states that the writer, “working in the Western Kondoa fly-belt, finds the more normal type of obvious concentration. In the dry season tsetse become more numerous in Berlinia-Brachystegia woodland immediately surrounding ‘vleis.’ Owing to the small size of these ‘vleis,’ which are only about 75 yards across, the fly appears to an observer to be concentrated in them; in reality they are probably living in the shade of the surrounding weeds and fly out to attack the investigator. Passing through Berlinia woods in this country one finds fly more numerous on the edge of “vleis,” probably because the trees are almost non-deciduous owing to sub-soil water.”

The diurnal flight and biting activity patterns of Culicoides phlebotomus (Will.) were investigated during ten all-day (06·00–19·00 h) trapping sessions at Las Cuevas Bay, north Trinidad. A comparison was made of the results obtained by biting catches, paddle trapping (in which a piece of greased wire screen was swung in front of the collector's legs) and truck trapping. Biting activity persisted throughout the day, with peaks of activity one to two hours after sunrise and again at sunset. Truck trapping recorded little variation in flight activity of empty females during daylight hours, but that of engorged, half-gravid and gravid females was greater during the afternoon than in the morning. Male flight activity was high in the early morning and mid-afternoon but declined rapidly towards sunset. Paddle trapping alone recorded a substantial increase in the blood-seeking activity of parous females after sunset. The paddle-trapping technique was found to be a useful alternative to biting collections for the study of anthropophilic Culicoides.

The purpose of this paper is to place on record my notes on the distribution of the mosquitos obtained by myself during an Expedition to Central Abyssinia made, in company with Mr. J. Omer Cooper, from September 1926 to January 1927. We were engaged in collecting insects of many Orders and some other animals, as well as plants, so that it was not possible to devote more than a limited time to Culicidae. Nevertheless, I purposely gave rather special attention to this family and got together a series of some 103 specimens of the adult insects, belonging to 13 (or possibly 14) species. Examples of each species were pinned immediately, when freshly killed, with fine pure-silver pins, while in a few places where large numbers of one species occurred the surplus specimens were placed in spirit. No detailed investigation of the larval or pupal stages was undertaken ; a few examples of these may later be forthcoming among the collection of aquatic organisms which are Mr. Omer Cooper's special province, but they are not dealt with here.