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.

Observations were made on Camptocerus aeneipennis (F.), C. aterrimus Eggers, C. niger (F.) and C. aquilus Wood infesting felled trees in the gallery and valley forests of the north-eastern Mato Grosso between September and December, 1968. The lifecycles of all four species are completed in 7–10 weeks. The gallery systems resemble those of the Xyloterini and Scolytoplatypus. The maternal galleries penetrate the wood and either lie in the transverse plane or run longitudinally, depending on the stem diameter. Trees of the family Burseraceae are especially attacked. The larvae are mycetophagous, developing in cradles which they enlarge as they grow. Larvae were attacked by an ectoparasitic Braconid wasp and predatory beetle larvae. Larval mortality is lower when one or both parents remain in the gallery. The potential forest importance of the four species could be contained by bark removal and rapid drying.

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.

Cross-mating occurred under laboratory conditions between Diparopsis castanea Hmps. and D. watersi (Roths.), although this subsequently resulted in only a slight egg hatch. Assays involving the use of virgin female traps demonstrated cross-attractancy between the two species. Since abdominal tip extracts of D. watersi females after gas chromatography produced the same pattern of electroantennogram responses as D. castanea female tip extract, it is probable that the sex pheromones of the two species are identical.

Two species, Aethognathus unicolor and A. bicolor, are described as new. The four known species of Aethognathus are parasitic on Stictococcus and Saissetia spp. in Africa. A key to the species and a host-parasite list are provided.

The responses of adult Glossina morsitans Westw. to large slowly moving visual stimuli were tested in the laboratory. The standard stimulus, lasting 60 s, consisted of a vertical black stripe (5° wide) on a white background moved 12 times past a window (25° wide) at 13·5°/s. The kinetic responses (take-off), but not orientation towards the stripe, went through a daily cycle with morning and evening maxima some 500% greater than the mid-day response. Kinetic responsiveness in both sexes and all ages of fly increased in an overall linear manner during five days' starvation, though pregnant females were about half as responsive as mature males. The intensity of orientation also increased with starvation, at least in males. For take-off, the minimum stripe width eliciting responses subtended ca 0·6° to the flies, and the optimum angular velocity was 3–7°/s, for orientation, 2–20°/s; the distance of the stripe appeared unimportant. Human odour elicited take-offs in the absence of the visual stimulus, and enhanced the visual responses if these were tested within three minutes of the start of odour stimulation; these effects were much greater in teneral than in mature males. It is concluded that the differences between the sexes and physiological stages of fly are mainly quantitative, and that the accepted view of four physiologically distinguishable phases of behaviour is therefore unsatisfactory. Instead, it is proposed that tsetse behaviour is the outcome of continuously variable responsiveness to visual host stimuli, and not a succession of behavioural entities.

The response to short photoperiod (10 h) of the F1 and F2 sexual generations of Myzus persicae (Sulz.) resulting from a cross between oviparae from a holocyclic clone and males from an androcyclic clone were examined and compared in experiments done at Imperial College Field Station, England. F1 and F2 progeny segregated into three distinct phenotypes; holocyclic, androcyclic and intermediate. Intermediate clones reared at 10 h photoperiod produced alatae which were physiologically intermediate between gynoparae and virginoparae, because their progeny consisted of oviparae, apterous virginoparae and intermorphs. Intermediacy was not affected by temperature and seems to be genetically determined. Segregation ratios in the F1 and F2 indicate that the androcyclic condition is induced by a recessive ‘ switch-gene ’ which completely suppresses the production of sexual females, and partially suppresses male production. This gene could be present in the heterozygous condition in a large proportion of parthenogenetic lines of the aphid, and thus confer a latent potentiality for anholocycly on populations even where conditions will not regularly permit this method of overwintering. Conversely where anholocycly is strongly favoured many aphids would be homozygous for the recessive, androcyclic character, but the potential for gamic reproduction could remain widespread.

A new tribe allied to the Telsimiini and Sticholotini and a new genus are erected for Ghanius karachiensis sp. n., a Coccinellid predator of Cerococcus hibisci Green in Pakistan.

Collections of Anopheles gambiae Giles complex, A. funestus Giles group and other mosquitoes were made by spray-catch from twelve catching stations indoors and by hand-catch from pit shelters at two catching stations at Segera, Tanzania, between January 1970 and June 1971. Females of A. gambiae were identified cytotaxonomically as sibling species A or B of the complex. In houses during 1970, A. gambiae species B was more numerous at first than A, but A became predominant during the long rains of March-May. In the cool dry weather of June-November both A and B densities declined and the A:B ratio surpassed 50:1. The short rains in December produced a population explosion of species B and less multiplication of species A, the B:A ratio reaching >11:1. In 1971, hot dry weather during January-March caused declines of species A and B with a maximum B: A ratio of 13:1. Long rains, coming in late March, provoked a resurgence of A and a concurrent decline of B, so that the A:B ratio again reached 20:1 in June. Similar cycles of species A and B were observed outdoors, although the relative numbers outdoors/indoors averaged 2·3 times more for species B than for species A. In A. funestus, A. gambiae species A and A. gambiae species B Human Blood Indices were 97·5%, 91·2% and 60·9% indoors and 24%, 2% and 7% outdoors, respectively. Respective malaria sporozoite rates were 1·62%, 4·23% and 0·32% and minimum rates of stage-Ill filarial infection were 0·33%, 0·44% and 0·57%. Sporozoite-positive and sporozoite-negative mosquitoes exhibited similar HBF's in species A and discrepant HBI's in species B. The HBI's were higher in filariapositive A and B females than in filaria-negative females. Gregarines occurred in 1·36% of species A and 0·38% of species B. Trematode cysts were seen in two specimens of species A.

Of A and B females 28% and 4%, respectively, had four-banded palps. It is shown mathematically that the discrepant malaria sporozoite rates in species A and B may be explained by extrapolating from the man-biting rate and probable daily survival rate for each species. This implies that no unrecognised factors play a major role in causing the contrasting efficiency of these two sibling species as malaria vectors.

A survey of Simuliidae in three areas of Pakistan in May and June 1963 yielded 845 pupae, some larvae and 143 captured adults, bringing the number of species for the area from seven to 31. Three species are described as new, and notes are given on other new but unnamed species. A key is given, based mainly on pupae. The previously unknown male, pupa and larva of Simulium indicum Becher are described, together with a new subgenus, Himalayum, for this species. It was breeding on vegetation in a fast river, occurring at 700–1450 m above sea level in spring and autumn, and at higher altitudes in summer. Pupae of S. mediterraneum were found in polluted water. Three species were phoretic, and several were found on or near man or domestic animals.

In laboratory experiments individual male Glossina austeni Newst. were each mated, at two- or three-day intervals, to nine different females. In one series of matings the males were restricted to one pairing and in a second series the sexes were left together for 24 h, when more than one copulation could have occurred. The technique followed in the second series was repeated with G. morsitans morsitans Westw. when the males were presented successively with 12 different females. The fecundity of female G. austeni, after mating with males previously mated on 0 to 5 occasions, was consistently higher when left with their mates for 24 h (mean puparia produced per mature female day=0·102) than when restricted to a single copulation (0.085). When the sexes were left together for 24 h, female fecundity of both species was maximal when mated with males used for up to six times (ca 0·10 puparia produced per mature female day) but became progressively poorer as the males were used more frequently (0·022 for G. m. morsitans females mated with males used for the twelfth time). The testes of muchmated males are markedly smaller than those of virgin males of the same age. Maximum disposable output of males from colonies of Glossina engaged in production for the sterile insect release method could be obtained by using males retained in the colony for mating on six occasions. It is speculated that in nature the absence of both teneral and old males from the following swarm ensures the presence of only fully sexually potent males in the swarm.

Laboratory cultures of Cicadulina mbila (Naudé), C. storeyi China and C. parazeae Ghauri derived from field wheat at Salisbury, Rhodesia, during August 1967 were maintained on caged pots of dwarf wheat seedlings. At constant temperatures of 23, 25 and 30°C developmental periods for eggs and adults were similar for all three species. Cultures of C. mbila were reared at a wider range of temperatures (15–30°C) and developmental rates for eggs, and male and female adults were shown to be well expressed by logistic equations. Mean durations are given for the five nymphal stages reared at 26°C. In C. mbila males and females had a similar life span, fecundity was greatest at 28°C, and there was a predominance of males reared from eggs laid by females less than 15 days old.

The effects of soil-applied thionazin on field populations of Carabidae were assessed in two fields of potatoes in Berkshire, England. Broadcast at 11·2 or 44·8 kg/ha in a light sandy loam soil, thionazin considerably reduced numbers of Carabids for up to eight weeks after application. Lower catches occurred again six months later when treated soils were rotavated after lifting of the potato crop; these were attributed to the exposure of Carabidae to thionazin residues which had leached into deeper layers of the soil. Dosages of 2·24 or 8·96 kg/ha applied in rows sometimes increased numbers of Carabidae trapped, possibly because of sublethal effects increasing locomotor activity. Carabidae affected most by the treatments were the small diurnally active species such as Bembidion lampros (Hbst), B. quadrimaculatum (L.), and Trechus quadristriatus (Schr.) which were also abundant at the time when the treatments were applied. Larger species such as Harpalus rufipes (Deg.), Pterostichus vulgaris (L.), P. madidus (F.) and Calathus fuscipes (Goeze) were also affected but were generally less susceptible partly because they appeared later in the season when the pesticide had partly disappeared. The rapid disappearance of thionazin from the surface 1·3 cm of soil could account for the low susceptibilities of non-burrowing species; Asaphidion flavipes (L.) which rarely burrowed was less susceptible and Harpalus aeneus (F.) which readily burrowed was more susceptible than other species of similar size.

Distances moved by Cicadulina spp. were investigated at Salisbury, Rhodesia, during 1968–69, by using small plots of oats to trap adults dispersing from populations breeding in Pennisetum clandestinum or Eleusine indica grasses. The shape of the curves constructed for fall of numbers with distance confirmed laboratory findings that populations are composed of long and short distance fliers. The curve for numbers of infective Cicadulina punctures estimated from the gradient of maize streak infection falling from adjoining cereals was also of similar shape. Mean flight times indicated that a steep fall for about 10 m from source is due largely to short distance fliers making trivial movements, and the subsequent gentle fall is due to long distance fliers which may disperse many kilometres depending on the wind speed. There were higher proportions of long distance fliers amongst C. mbila (Naudé) compared to C. storeyi China, and amongst females compared to males dispersing downwind. A predominance of long distance fliers dispersing from drying grasses during April–September, and of short distance fliers present in irrigated grasses and cereals during October–March, causes seasonal differences in the patterns of maize streak infection and in the effectiveness of barriers of clear ground as a preventive measure.

The flight periods of eight species of Adelgids were deduced from suction trap catches in a mixed woodland site at Alice Holt, Hampshire from 1965 to 1970. Nine species from other natural forest areas in the northern hemisphere occurred on trees in the study area, but some immigration may have contributed to the numbers trapped. Large catches (often >200 individuals per day) of three pest species, Adelges laricis Vall., A. cooleyi (Gill.) and Pineus pini (L.), occurred during late May and June. Only small catches (<10 individuals per day) were obtained during July–September. The sexuparae from the non-Picea hosts occurred mainly in May and June whereas the gallicolae from Picea hosts flew during certain periods from June to September. Analysis showed that the threshold temperature for flight was 16°C and that 64% or more of the total monthly catch occurred in the afternoon (13·00–19·00 h). The variation in length of the early summer flight period by ± one week was related to air temperature maxima, but the fluctuation ( ± one week) in the mean date for flight of each species in the early summer period is probably connected with the phenological condition of the host-plant.