Numerous experiments have been performed to study the specific effect of hydrogen ion concentration, CO2 and oxygen content of water on may-fly larvae, which warrant the following conclusions :—

1. While hydrogen ion concentration is a factor of great significance, the carbon dioxide pressure is of greater importance and should afford a very reliable index of the suitability of water as a habitat for true aquatic insects.

2. May-fly larvae, and presumably other insects as well, can stand a very low concentration of oxygen, below 1·0 cc. per litre. In view of the fact that in nature oxygen content seldom goes down to such a low figure, insects should not, as a rule, die of lack of oxygen.

Basic laboratory investigations have been carried out on a method for giving house-flies, Musca domestica L., relatively large doses of insecticide, with a view to possible applications in controlling, or preventing the appearance of, resistant strains of flies. The principle is that a relatively large drop of mineral oil will hang on the lower end of a thin vertical or near-vertical wire (e.g., a drop of up to 3 μl. on a wire 0·3 mm. in diameter), and a fleeting contact of a fly with the drop will generally transfer to the surface of the fly a substantial volume of oil. For investigational purposes pins were inserted obliquely into rods (e.g., about 700 pins into a rod 60 cm. long), and drops of up to about 1 μl. were formed on the ends of the pins by dipping the pin-bearing rods into solutions of insecticide in oil. In a typical experiment a rod with suspended drops was hung vertically from the ceiling of a chamber into which flies were released; flies then collected doses of insecticide when attempting to alight on the rod.

The melon weevil, Acythopeus curvirostris (Boheman), is a speciescomplex comprising at least four allopatric forms, here regarded as subspecies. Of the seven available species-group names, three are retained for subspecies and four placed in synonymy; an eighth name is proposed for the fourth subspecies. The generic and subgeneric placements of the melon weevil and its relatives are discussed. The following check-list of the species of Acythopeus (Carpobaris) summarizes the present position (synonyms all new): A. (C.) curvirostris (Boheman) (=traegardhi (Aurivillius)), A. (C.) c. granulipennis (Tournier) (=colocynthae Voss, globulicollis Voss, cucumidis Voss), A. (C.) c. persicus subsp. n., A. (C.) c. citrulli Marshall, A. (C.) alcyoneus (Erichson) (=atrocoeruleus (Boheman)), A. (C.) cucurbitae (Marshall), A. (C.) speciosus (Gerstaecker), A. (C.) coelestis (Pascoe). (Acythopeus francisci nom.n. = A curvirostris Pascoe, 1874, nee Boheman, 1844.) Simple biometric procedures indicate differences between the subspecies of A. curvirostris; some characters show clinal variation. The melon weevil occurs across the Sudan Belt, in the Middle East, Iran and South India. It is generally a minor and transient pest of cucurbit fruits. One parasite and one predator are known.

Such knowledge as we have of the family Lacciferidae is very largely embodied in an excellent monograph published in 1923 and 1925 by J. C. Chamberlin (Bull. Ent. Res. 14, pp. 147–212 and 16, pp. 31–41). The comparatively speaking limited geographical distribution of the various generic groups is well brought out in this monograph. Thus, for instance, the genera Tachardiella and Austrotachardiella are apparently confined to North and South America, Metatachardia to Ceylon, Austrotachardia to Australia, Tachardia to India and the Far East. Chamberlin further states (p. 149) “ in general it may be said that the species of this group are tropical or sub-tropical, apparently reaching their greatest abundance in regions of limited rainfall.” How far this comparatively limited and well-defined zonal distribution of the various genera will hold good as further material is collected will prove of the greatest interest.

The author discusses the restriction of the genus Lepidosaphes to nine Holarctic species by Borchsenius and his assignment to other genera of most species previously placed in Lepidosaphes. These changes in generic assignment have affected the names of many species of economic importance. A key is presented to 13 genera allied to Lepidosaphes.

Although within the last few years—chiefly owing to the diagnostic ability and brilliant technical skill of Professor Robert Newstead, F.R.S.—several additions have been made to the list of recognised species of Glossina, the numerical total of which now stands at nineteen, the Glossina morsitans Group has not received a single accession. Peculiar interest therefore attaches to the discovery of the species described below, not only by reason of its apparent pathogenic importance,* but also on account of its systematic position within the genus.

Decreased reliance on pesticides can be achieved through a clever use of eco-evolutionary knowledge via intercropping economically valuable crops with companion plants that can hamper pest outbreaks. We created a greenhouse multi-layered microcosm system to test two potato peach aphid clones, performing alone or in competition, on mixes of genetically variable cultivars of cabbage, with and without onion. The onion acted as a nuisance/disturbance for the pest, which was generally for the benefit of the cabbage albeit both plants sharing space and nutrients. The onion effect was context-specific and differed by aphid genotype. Onion variable nuisance negatively affected the numbers of one aphid genotype (green) across all contexts, while the other genotype (pink) numbers were decreased in two contexts only. However, the green performed better than the pink on all cases of cabbage di-mixes despite its numbers being capped when the onion was present. Further, there was also a general aphid propensity to wander off the plant along with a differential production of winged morphs to escape the onion-affected environments. Moreover, through a comparative increase in dry mass, which was subject to onion and aphid effects, a diversity effect was found where the cabbages of fully genetically variable microcosms sustained similar final dry mass compared with non-infested microcosms. Our findings provide fresh insights into the use of multi-layered contextual designs that not only allow disentangling the relative effects of genetic variation and modes of interaction, but also help integrate their benefits into pest management in view of companion planting.

Diabrotica speciosa is an important pest of several crops in South America, including soybeans. Adults cause severe defoliation in soybean plants, and damage is significant when cotyledons are attacked. This study evaluated feeding non-preference to D. speciosa adults using 10 soybean genotypes, testing (i) 15-day-old whole plants and (ii) leaf disks of 60-day-old plants, through assessments of soybean attractiveness and leaf area consumed (LAC). Foliar contents of flavonoids and nutrients, and leaf trichome density were quantified for potential correlations with soybean resistance to adult of D. speciosa. In the whole young-plant experiment, under free-choice conditions, the lowest LAC was observed in IAC 100 and PI 227687. In no-choice, PI 227687 and IGRA RA 626 RR showed lower LAC than the other genotypes. In the leaf disk test, in free-choice, the genotypes IAC 100, PI 274454, PI 227687, DM 339, and BR 16 were the least preferred by adult of D. speciosa. In no-choice, PI 274454 was one of the least preferred, similarly to IGRA RA 626 RR, Dowling, and PI 227687. In the whole plant experiment, a high rutin content and low amounts of zinc, calcium, sulfur and manganese were associated with less consumption of D. speciosa on leaves of resistant genotypes. In contrast, in the leaf disk test there was a significant influence of trichomes in soybean resistance to the pest. In conclusion, the PI lines herein assessed are also promising sources for developing cultivars resistant to D. speciosa.

The silkworm Bombyx mori (Lepidoptera: Bombycidae) is a lepidopteran model insect of great economic importance. The parasitoid Exorista sorbillans (Diptera, Tachinidae) is the major pest of B. mori and also a promising candidate for biological control. However, the molecular interactions between hosts and dipteran parasitoids have only partially been studied. Gene expression analysis by reverse-transcription quantitative real-time polymerase chain reaction (RT-qPCR) is indispensable to characterise their interactions. Accurate normalisation of RT-qPCR-based gene expression requires the use of reference genes that are constantly expressed irrespective of experimental conditions. In this study, the expression stability of 13 traditionally used reference genes was estimated by five statistical algorithms (ΔCt, geNorm, Normfinder, BestKeeper, and RefFinder) to determine the best reference genes for gene expression studies in different tissues of B. mori under E. sorbillans parasitism. Specifically, TATA-box-binding protein was the best reference gene in epidermis and testis, while elongation factor 1α was the most stable gene in prothoracic gland and midgut. Elongation factor 1γ, ribosomal protein L3, actin A1, ribosomal protein L40, glyceraldehyde-3-phosphate dehydrogenase and eukaryotic translation initiation factor 4A were the most suitable genes in head, silk gland, fat body, haemolymph, Malpighian tubule and ovary, respectively. Our study offers a set of suitable reference genes for gene expression normalisation in B. mori under the parasitic stress of E. sorbillans, which will benefit the in-depth exploration of host-dipteran parasitoid interactions, and also provide insights for further improvements of B. mori resistance against parasitoids and biocontrol efficacy of dipteran parasitoids.

The larvae and pupae of Elachiptereicus abessynicus Becker and of Pachylophus lugens Lw. are described and illustrated and those of the latter species are compared with those of Pachylophus beckeri Curr. A previous misidentification of P. beckeri is recorded and additional records of host plants and distribution are given for all three species.

Glossina pallidipes does not readily attack objects moving along the edge of vegetation forming its habitat; fewer tsetse attack under humid than Under dry conditions, but those that do seem to range further.

Parties of men moving out of heavily infested thicket did not carry tsetse far into the open. Few tsetses attached themselves to the men and these became gorged within a few yards of the thicket edge. Similar results were obtained when bait cattle were used.

Experimental catches in a glade showed, even during the humid season, an extraordinary reluctance on the part of G. pallidipes to approach a party moving through the glade even at so short a distance as 8 yards from the thicket, but further experiments showed that a party staying in the glade for a short time made a much larger catch.

Insects breathe using one or a combination of three gas exchange patterns; continuous, cyclic and discontinuous, which vary in their rates of exchange of oxygen, carbon dioxide and water. In general, there is a trade-off between lowering gas exchange using discontinuous exchange that limits water loss at the cost of lower metabolic rate. These patterns and hypotheses for the evolution of discontinuous exchange have been examined for relatively large insects (>20 mg) over relatively short periods (<4 h), but smaller insects and longer time periods have yet to be examined. We measured gas exchange patterns and metabolic rates for adults of a small insect pest of grain, the red flour beetle, Tribolium castaneum (Coleoptera: Tenebrionidae), using flow-through respirometry in dry air for 48 h. All adults survived the desiccating measurement period; initially they used continuous gas exchange, then after 24 h switched to cyclic gas exchange with a 27% decrease in metabolic rate, and then after 48 h switched to discontinuous gas exchange with increased interburst duration and further decrease in metabolic rate. The successful use of the Qubit, a lower cost and so more common gas analyser, to measure respiration in the very small T. castaneum, may prompt more flow-through respirometry studies of small insects. Running such studies over long durations may help to better understand the evolution of respiration physiology and thus suggest new methods of pest management.

Experiments were carried out in West Bengal to ascertain whether the Paddy Stem Borer, Schoenobius incertulas (Wlk.) could be controlled by “Tetrax” 1, a systemic insecticide containing technical schradan equivalent to approximately 42 per cent, octamethyl pyrophosphoramide + approximately 25 per cent, triphosphoric acid pentadimethylamide.

In a preliminary experiment, treatment had little effect on the damage caused by the borer but the yield of grain was higher from a treated plot than from a control plot.

A further experiment was carried out, the following year, in which the seed was soaked in a 0·1 per cent, water solution of “Tetrax” 1 for eight hours before sowing in the seed beds. The seedlings were lifted about 2½ months later and steeped in 0·1 per cent. “Tetrax” 1 for eight hours before transplanting into two plots, each 32 ft. × 32 ft. About three weeks later the plants were sprayed with a solution of the same strength. Two plots of similar size, in which the paddy had received no treatment, were maintained as controls.

Again there was very little difference, between the treated and untreated plots, in the damage caused to the ear heads by the pest, but the treated plots produced 108·68 lb. of grain as against 77·27 lb. for the untreated plots. The increase was largely due to an increase in the number of ear heads per plant.

The incidence of the borer was too low in both experiments to determine whether “Tetrax” 1 exercised any appreciable control, but the treatment did give rise to a higher yield of grain under the conditions of the experiments.

The following is a list of the more important insects collected in the Province of Mozambique (Portuguese East Africa) and which in some stage of their existence may be harmful to men or animals. During the writer's stay in Mozambique it was impossible to make a complete survey of that immense colony, but as much collecting was done as opportunity offered and this list may be considered a fairly representative one.

The Oyani Valley is in the South Kavirondo native reserve of Kenya Colony. The river from which the valley takes its name rises in the Kilgorris groups of hills in and near the south-west corner of the Masai Reserve. The Oyani enters South Kavirondo at a point about 1°0' South by 30°35' East; it flows in a general north-westerly direction through the Kanyamkago location and joins the Kuja River about eighteen miles above the junction of the Kuja and the Gori Rivers.

Omnivory involves numerous feeding relationships and a complex web of interactions. When using omnivores in biocontrol, these interactions need to be understood to maximize feeding on the target species and minimize non-target interactions. Dicyphus hesperus is used along with Encarsia formosa for biocontrol of whiteflies in greenhouse tomato crops. Dicyphus hesperus is a generalist omnivore which feeds on all components of the system. To quantify these interactions, stable isotope analysis was used to identify trophic position with nitrogen isotopes (δ15N) and plant sources with carbon isotopes (δ13C). Feeding trials were used to establish baseline isotopic data for D. hesperus and their diet, including Verbascum thapsus, an alternative plant food. Cage trials were used to monitor population abundances and the isotopic signature of D. hesperus. In feeding trials, D. hesperus were enriched relative to their food, suggesting an elevated trophic position. However, large amounts of isotopic variation were found within all diet components, with only V. thapsus exhibiting a distinct signature. In cage trials, the average δ15N and δ13C of the omnivore declined over time, coinciding with declines in total available prey, though it may be confounded by changes in temperature. The range of δ13C, but not the range of δ15N, also declined over time. This suggests a change in the plant source within the diet, but also some unquantified variability within the population. We suggest that diet variability exists within D. hesperus populations, declining as prey become less abundant.

Genetic methods to eliminate females prior to releasing sexually sterilized males in sterile insect technique programmes generally involve the translocation onto the Y chromosome of a readily selectable gene (here designated F). However, such strains often show instability with regard to sexual dimorphism. Concerted attempts to determine the most probable causes of such instability have rarely been successful, and appropriate countermeasures have generally not been implemented. We have developed a computer model which simulates the progression of instability in such strains. Here we simulate the effects of contamination in association with a range of genetic and biological parameters and assess the patterns and rates of progression of the ensuing instability. A single event of contamination alone was found to contribute relatively little to the progression of instability and invariably resulted in an equilibrium within the population. However, strong effects were produced by reduced fitness and mating competitiveness of both the f/f genotype and the translocation carriers, a reduction in the parameters involving the f/f genotype resulting in the virtual elimination of f/f, while a reduction in the translocation parameters had the opposite effect of virtually eliminating the F/ – phenotype. The sex ratio was affected only by a change in the relative fitness of the f/f genotype and the translocation. Several characteristic patterns contributed to distinguish clearly the effects of contamination from those of male recombination in unstable genetic sexing strains. With such knowledge appropriate measures may be taken to counter or alleviate the effects of instability in mass reared genetic sexing strains.

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.