Ten insecticides were assayed for toxicity against an unselected and a resistant strain of Myzus persicae (Sulz.). Of the six topically applied insecticides parathion was the most effective, followed by diazoxon, diazinon, aldrin, dichlorvos and p, p′DDT in that order, while the resistance levels were, in descending order, parathion, dichlorvos, diazinon, diazoxon, p, p′DDT and aldrin. Of the four systemic insecticides, pirimicarb was most toxic, followed by dimethoate, phorate and demeton in that order, while resistance ratios were in descending order dimethoate, phorate, demeton and pirimicarb. The organophosphorus resistance spectrum for M. persicae indicated that more than one resistance mechanism is involved, and that resistance acts against diethoxy and dimethoxy compounds.

Melicharia obtusanguloides sp.n. (Flatidae) infesting tea in southern India is desscribed and compared with M. obtusangula Distant and Idume plicata Melichar whose male genitalia are illustrated. The male type of M. obtusangula is designated as lectotype. Brief notes are given on the habits of Ketumala thea Ghauri (Flatidae) and Ricania fenestrata (F.) (Ricaniidae), and the male genitalia of the latter species are figured.

Examination of the cephalic lobes of larvae of Psila rosae (F.) by means of light and scanning electron microscopes revealed the presence of 24 sensilla, ten campaniform, eight basiconic, four ampullaceous and two styloconic. By comparison with the known functions of similar sensilla in other insects, it is suggested that the ampullaceous and basiconic sensilla respond to plant emanations in soil, air and water, respectively, and that styloconic sensilla determine the palatability of the root hairs; the role of the campaniform sensilla is obscure.

Apterous adult Myzus persicae (Sulz.) of a glasshouse strain differed greatly in their ability to colonise sugar-beet according to the plant on which they and their forebears were cultured. Those from Chinese cabbage (Brassica pekinensis) settled least readily on beet, whilst aphids from broad beans (Vicia faba) produced larger populations than those cultured on sugar-beet. When reared wholly on groundsel (Senecio vulgaris) young adults differed in their ability to colonise Chinese cabbage, sugar-beet and broad bean according to their parents' culture host species, and these differences were detected in a second generation reared wholly on groundsel. The responses of clones isolated from cultures maintained continuously on Chinese cabbage and broad bean were similar, showing that the effect was caused by the aphids' host-plant experience, and was not due to fixed, heritable characters of the sub-cultures. Some, but not all clones of M. persicae collected from the field showed enhanced colonising ability after culture on broad bean as compared with Chinese cabbage. This was apparent on sugar-beet and lettuce (Lactuca sativa). These effects of former hosts on the ability of M. persicae to colonise plants may be important both in work on resistance to aphids and in the epidemiology of aphid-borne diseases.

As part of a research project directed at the genetic control of Teleogryllus commodus (Wlk.) in Australia, hybridisation studies have been carried out between T. commodus and the sibling species T. oceanicus (Le Guillou). A cytological examination of a hybrid strain (male progeny of T. commodus × T. oceanicus backcrossed to T. oceanicus) was made in the F4 generation when meiotic stability had been reached. The karyotype was very similar to that of T. oceanicus, suggesting that only those combinations in which the chromosomes were structurally homologous to T. oceanicus survived. But the stridulation pattern of the hybrid males, intermediate between that of the two parental species, and a consistent sex ratio of 2:1 in favour of the males, indicate profound genetic differences from T. oceanicus. These effects are attributed to introgression, with chromosomal material from T. commodus being incorporated in the T. oceanicus genome as an outcome of the initial hybridisation of the two species.

Pedronia festeriana Lizer y Trelles is found on Cereus aethiops, Cleistocactus baumannii, Eriocereus bonplandii and E. martinii in Argentina. It severely distorts the growing tips and could possibly be used to control these weed cacti. The species is transferred to Hypogeococcus and redescribed from material collected recently in Argentina. Pseudococcus eriocerei is described as new also from the roots of Eriocereus bonplandii.

Catches in light-traps adjoining cotton were obtained at the time of seasonal southward movement of the Inter-Tropical Front (ITF) in October, and during most of the following two months. Taxa studied were mostly Orthoptera and moths, many associated with sorghum, others long-distance migrants. Suction-trap catches at three heights up to 50 ft were obtained for short periods in October and November, and aircraft catches at 250 ft were also available on two days. Suction-trap catches of grass-feeding Homoptera suggest that displacement of these insects was associated with changes in wind direction marking movement of the ITF in October. The exact form of the displacement system in relation to the front cannot be reconstructed from catches at a single place, but it seems likely that proximity of the front at or soon after the time of a brief period of crepuscular activity stimulates insects to take flight and rise to 50 ft or more so that they are displaced. In many taxa, light-trap catches showed a regular pattern of increase, with only slight nightly fluctuations from a logarithmic trend, following full moon. Other increases were superimposed on this pattern at times when the ITF passed north of the trap site, and in some taxa particularly when it was far north. The pattern of change after full moon, shown most clearly in taxa with source populations close to the trap, was related to the moon's influence on the range of trap effectiveness. But various qualitative variations suggest that, in addition, aspects of behaviour or development may have adaptive relationships to the lunar cycle; variations include differences between taxa, particularly in timing of catch changes, and increasing proportion and decreasing maturity of females of certain taxa at the time of the regular increases in catch.

Investigations were carried out on the ecology of Aedes (Aedimorphus) dentatus (Theo.) in the Ngong Forest near Nairobi between 22 June and 10 September 1971. Five 24-h collections on human bait showed that Ae. dentatus is predominantly a daytime biter with a peak of activity around sunset. At the time of its greatest activity none came to bite on the 7- or 10-m platforms. Of 94 blood-meal specimens, 50 were of Bovid origin (cattle), 18 from unidentified Bovids, 13 from unidentified mammals, one from a bird, three from any primate and nine did not react with the antisera used. Resting adults were frequently found underneath leaves of Hypoestes verticillaris, a herb which grows in partly shaded areas in the forest near the forest edge. A few adults came to bite in a house outside the forest not far from the forest edge. Breeding places were not found. The evidence for Ae. dentatus being a vector of yellow fever is inconclusive. The 33 other species of mosquitoes collected are listed.

In the tropics, the amount and the pattern of distribution of moonlight at and just after full moon produces alternating periods of continuous illumination and darkness which could provide photoperiodic cues for insects. Examples of possible photoperiodic effects induced by moonlight, taken from the published literature, include the flight activity and oviposition patterns shown by females of Heliothis zea (Boddie) and Diatraea saccharalis (F.) and crepuscular activity of mosquitoes. It is suggested that photoperiodic responses to moonlight could form the basis for a simple method of predicting such events.

An intensive study was made of the ecology of species A and B of the Anopheles gambiae Giles complex at Kaduna, Nigeria, in October 1971. In collections comprising 383 larvae and 678 adult females from six villages, species A represented 82% of the larvae and 86, 89 and 91% respectively of the adult females caught by spray catches indoors, by biting catches outdoors and by exit traps fitted to windows. Larvae of species A and B occurred together in 42% of 57 breeding sites and showed no differential distribution among the various categories of site. Minor variations among the proportions of A and B females captured by different methods in the six villages showed no consistent contrasts. The only significant variation of the A/B ratio occurred at a temporary Fulani camp of cattle herdsmen, near Anguwun Maaza village, where an enhanced number of species B females were present indoors. At this Fulani camp a considerable number of both A and B females were feeding on cows outdoors and resting indoors during the day. Human blood indices of indoor-resting females were 88% for species A and 39% for species B at this camp, compared with 100% for both species at villages without cattle. Larval breeding places harboured an expectable range of insect predators. Predators of adult A. gambiae were not investigated although a predacious Emesine bug, Tinna elongata Villiers, was recorded in some huts. Numerous pathogen infections of larvae were observed, namely, Thelohania in 19%, Coelomomyces in 16%, unidentified gregarines in 7% and black-body virus in 3% of gambiae-positive breeding sites. Thelohania, Coelomomyces and gregarine infections were also encountered in adult females. Malaria sporozoite rates were 9·3% in species A and 5·5% in species B females. Some infections of stage III larvae of Wuchereria bancrofti were also seen in species A females.

The genus Obtusiclava, allied to Homoporus Thomson, is erected for the new species O. oryzae, a larval–pupal parasite of Pachydiplosis oryzae (Wood-Mason) in India and Ceylon.

The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined. There is a brief review of stylet structure and movement and the possible sensory nature of these organs, followed by a detailed review of the characteristics of aphid stylet paths in plant tissues. The penetration of epidermis and vascular tissues is treated separately while that within the intermediate tissues is covered in relation to leaves and stems, roots, trees, galls and excised tissue as well as in separate sections on Aphis fabaeScopoli and Myzus persicae (Sulzer). Stylet destinations and behaviour in the sieve tubes are discussed together with general features such as rate and depth of penetration, guidance to the feeding site, effects of tissue hardness and stylet withdrawal. The ingestion rate of plant sap is reviewed and its constitution and importance examined together with the significance of artificial diets. The salivary secretions including sheaths and tracks, their functions and their role in the transference of material between aphid and host are dealt with. The nature of the physical and internal damage resulting from aphid feeding is briefly covered, and also some plant-insect interrelations. The aphid species whose stylets have been examined in plant tissue are listed.