After preliminary collections with suction traps at heights of 30 and 135 cm had shown that most mosquitoes were caught in the lower trap, suction trap catches were made for three years from about April to November in a wooded area in southern England. Flight periodicities of females of Aedes cantans (Mg.) and Ae. geniculatus (Ol.) and of both sexes of Anopheles plumbeus Steph. and Culex pipiens L. were determined by traps incorporating automatic segregating devices. In all species maximum flight activity was between 19.00–20.00 h GMT. The biting cycles of the first three species were similar to their general flight patterns. Mean hourly densities of all four species were calculated from the suction trap catches. Collections were made with traps placed at five different heights (23–223 cm) in 1968 and at eight heights (23–550 cm) in 1969 and 1970. In most species there was a well defined and rapid decline in aerial density of both sexes with increasing height, but more unfed females and males of Culex pipiens L. and females of Culiseta morsitans (Theo.) were caught in the highest trap. From about mid-August onwards, when adults of Culex pipiens were searching for hibernation sites, both males and females with fat reserves were commonest in the lowest trap. The slopes of the regression lines of log. density on log. height were calculated separately for Ae. cantans and C. pipiens, and for all adults combined for five less common species. In all catches, except those of C. pipiens, unfed females predominated.

A technique is described in which twelve symbols or fewer can be chosen to code insects with individual marks suitable for mark-recapture studies. The method has been tested on Acrididae and has the advantages that (i) the code is self-checking against loss of marks, (ii) the application is practical, as only one colour is applied to a given individual, (iii) the versatility of the coding permits thousands of individuals to be distinguished, and (iv) an individual can be identified in the field from distances up to three metres without disturbance or rehandling. Guitar oil paints gave the most persistent marks, and were applied with a fine tubular-nib pen.

Cyrtorhinus rectangulus from Kenya and C. caricisoides from Madagascar are described as new. A key is given for the eight species of Cyrtorhinus.

A laboratory colony of Glossina morsitans orientalis Vanderplank had been kept successfully in Edinburgh for 18 months, when reproduction ceased because of a high incidence of abortion and follicular degeneration. A comparison of these flies with imported Bristol-bred flies showed that the latter reproduced well under identical conditions, but since Edinburgh-bred progeny of imported flies also showed poor reproduction, a genetic difference between the two populations could be ruled out. Comparisons of the progeny of flies fed on human and rabbit blood, and of the progeny of flies fed on rabbits maintained on different diets, produced strong biological evidence for a toxicant in one of the diets which produced reproductive abnormalities in the Ft generation of flies. The trouble was thus traced to a change in rabbit diet which took place about a month before the appearance of the reproductive disorders. It is suggested that the toxicant, which remains unidentified, is concentrated by the parent female in the accessory gland secretion and thereby incorporated into larval tissues during intra-uterine development.

An account is given of glasshouse experiments in Jamaica to determine the effects of agronomic practice on the fecundity of the sugar-cane pest Saccharosydne saccharivora (Westw.). Eggs (up to one egg per ovariole per day) develop throughout adult life. On young vigorous plant cane the pre-oviposition period was 5·3 days; egg production was highest during the first six days of the oviposition period and declined markedly after 12 days. Mean daily egg production per female over 12 days was taken as an index of fecundity.

The effects of fertiliser application (ammonium sulphate and potassium chloride), wet and dry water regimes, variety (B41227, B42231 and B4362) and crop cycle (plant and ratoon cane), all at different stages of crop development, were observed in four series of experiments involving 1 000 female S. saccharivora. Potassium (K2O) and phosphorus (P2O5) per cent lamina dry matter varied comparatively little, but nitrogen content declined with the age of the plant, increased with application of ammonium sulphate, and was unaffected by crop cycle or variety. Egg production was highest on young cane (up to a mean of 12·0 eggs per female per day), but declined on older cane; it increased with the application of ammonium sulphate but was unaffected by potassium chloride. A direct linear correlation between egg production and the nitrogen content of the leaf (r2 = 0·69, 0·81, 0·52 and 0·69 in series I–IV, respectively) suggested a causal relationship. The pre-oviposition period lengthened and the proportion of females failing to lay any eggs increased in the absence of fertiliser and with increasing plant age. Variation in leaf nitrogen under field conditions could affect egg production.

Descriptions are given of all growth stages of Valanga nigricornis nigricornis (Burm.). The hopper instars (normally six in the male and seven in the female) could be distinguished by the development of the external genitalia. Under laboratory conditions (mean 27–9°C and 80% r.h.), the life-cycle was completed in 6½–8½ months, and the females had a mean fecundity of 158. Crowding slowed the growth rate of the adults, extended the pre-oviposition period from 60 to 65 days at 30–9°C and reduced fecundity. It is concluded that the low fecundity and slow life-cycle preclude the possibility of the species becoming a widespread pest.

During November and December 1969, larvae and adults of the Anopheles gambiae complex from the Kisumu area of Kenya were identified by cytogenetical methods as species A and B. There appeared to be no difference between their choice of larval habitats. Although adults of both species were common in village huts, species B comprised 80·6% of the exophilic population. Adults of both species caught from huts and out of doors had fed predominantly on bovids; the incidence of human feeds was below 40%. The impact of residual insecticidal house-spraying would depend on the relative sizes of the endophilic and exophilic populations of species B.

The arrival of mosquitoes at human bait under natural conditions could be divided into three behavioural phases, the exploratory, the penetration and feeding periods. The duration of these periods was recorded in Mansonia richiardii (Fie), Anopheles plumbeus Steph., Aedes punctor (Kby.), Ae. detritus (Hal.), Ae. cinereus Mg. and Ae. cantans (Mg.). Adults of M. richiardii took the longest (about 4 min) and those of Ae. cinereus the shortest (about 2 min) time to obtain a blood-meal. Penetration by the mosquitoes' mouthparts was felt in about 17% of the feeds, and irritation was caused by about 18% of the mosquitoes during feeding. The natural host preferences of these, and 11 other species, were determined by precipitin tests on blood engorged mosquitoes. Adults of Culex pipiens L., C. torrentium Mart, Culiseta morsitans (Theo.) and C. litorea (Shute) were essentially avian feeders; three adults of the latter two species had also fed on unidentified reptiles. Most adults of the other species had fed mainly on mammals. There were few multiple feeds. Although the ability of a mosquito to take a blood-meal quickly from a host was recognised as important, other phenomena such as uninterrupted feeding, simultaneous feeding by large numbers of mosquitoes and host desensitisation to bites were also considered important in contributing to the success or failure of a mosquito in obtaining a blood-meal.

Insulaspis pinea Borchsenius, originally described from North Korea on Pinus sp., is redescribed from specimens collected in Hong Kong on Pinus taeda. A key is presented of all known Insulaspis species on Coniferae. The second species of Thysanofiorinia is described as new from Nephelium sp. (lychee) from specimens collected in Hong Kong and Taiwan.

Laboratory experiments showed that the mated status of male sheep blowflies (Lucilia sericata (Mg.)) can be reliably detected a week after mating, but subsequently the test is less accurate. Injection of 4–36 Ϝg tepa/male fly induced approximately 95% sterility. Tepa-injected flies mated freely, and the treatment did not interfere with the mated status test subsequently performed. The test has potential value in sterile male release studies.

The taxonomy of 39 species of mealybugs (Pseudococcidae) attacking sugar-cane, rice and sorghum is discussed. Twenty-seven species are described, eight of them as new. Some aspects of the biology derived from the literature are added, together with a key to the 39 species, and host and distribution records of each.

Three species of Pediobius Walker associated with the oil palm Hispid beetle are studied. One is identified as P. coffeicola (Ferrière), comb.n. The other two are described as new, and a key separating one of them from P. nigripes (Waterston), comb.n., and P. amaurocoelus (Waterston), comb.n., is given. Two new species of Achrysocharis Girault are described, one a parasite of Dipterous leaf-miners in coffee, one reared from galls on mango.

A successful colony of Glossina morsitans orientalis Vanderplank was initiated at Langford in early 1967 with 94 females imported as pupae from Rhodesia. In September 1969, further pupae were received from Rhodesia. Experiments were undertaken in which the four possible combinations of crosses were made between males and females from the Langford colony and from the 1969 importation from Rhodesia. Females of Langford origin performed equally well irrespective of the origin of their mates and it is concluded that there is no evidence that the Langford colony of G. morsitans is either performing abnormally well, because of adaptation to the laboratory, or abnormally badly, because of adverse effects of inbreeding. The poorer performance of females of Rhodesian origin was manifested in poorer survival rather than a lower fecundity; it is attributed to adverse effects on these flies caused by handling of the pupae in the field and/or the stress of the journey from Rhodesia to Langford. It would seem that to avoid any risk of inbreeding in laboratory colonies, wild males only should be introduced periodically.

When virgins of both sexes of the sheep blow-fly Lucilia sericata (Mg.) are placed together in cages, the cumulative mating frequency curve has a regular form: the shape of this curve is believed to be largely a consequence of the progressive decrease in the density of flies available for mating. A model based on this hypothesis is successfully tested against experimentally obtained data. A mating rate coefficient is proposed.

Abgrallaspis pictor is described as new from specimens collected on Cymbidium sp.in a nursery in England. It damages the plants by causing leaf-spotting. The orchid plants were collected in North India in 1968.

The spectral sensitivity of gravid female Aedes aegypti (L.) was investigated in the laboratory using their responses to oviposition sites illuminated by light of defined intensity and spectral composition. An inverse relationship between the illumination of an oviposition site and its selection for egg-deposition enabled the sensitivity of the mosquitoes to narrow wavelength bands to be assessed. This species showed low sensitivity to long (red) wavelengths; a peak of maximum spectral sensitivity near 550 mμ (yellow-green) with a range of significant sensitivity about this maximum between 450 (violet) and 630 mμ (orange); and positive sensitivity at 366 mμ (ultraviolet) which, from the different order of effectiveness in deterring oviposition, may represent a second, independently functioning, light receptor system. This pattern of sensitivity is sufficient to explain all published observations on the responses of mosquitoes, in physiological conditions other than gravidity, to coloured stimuli. It may, therefore, represent the spectral sensitivity of mosquitoes in general.

Populations of Culex pipiens fatigans Wied. were exposed to infection by Plistophora culicis (Weiser) by allowing eggs to hatch in water containing a known concentration of spores. At 26°C–28°C (mean 27°C) exposure of newly hatched larvae to a concentration of 6 000 spores/ml resulted in a 12–9% reduction in the net reproduction rate, and exposure to a concentration of 12 000 spores/ml to a reduction of 24·0%. These reductions were due to an increase in the rate of female mortality and an increase in the number of eggs laid which were non-embryonated and hence did not hatch. At 33°C–35°C (mean 34°C), although the spores of the microsporidian were not killed, development of P. culicis in the mosquito was inhibited. At 19·5°C–20·5°C (mean 20°C), the net reproduction rate of a population exposed as newly hatched larvae to a concentration of 1 890 spores/ml was reduced by 35·6%, due to a greatly increased rate of female mortality. P. culicis, with the inocula tested, is not considered of practical use against C.p. fatigans; more infective spore inocula are not feasible with the present methods of propagating the parasite.

Experiments in a glasshouse have shown that the most favourable conditions for transmission of cabbage black ringspot virus by Myzus persicae (Sulz.) to turnip plants with two foliage leaves were as follows: an acquisition access period of five minutes; a test-feeding period of not less than two hours; the use of nine viruliferous aphids per test plant; the use of aphids from uncrowded colonies; the use of the third leaf from the base of an infected turnip (5-leaf stage) as virus source; and inoculation of the younget leaf of a test plant. Darkening plants for 24 or 48 h did not increase susceptibility to aphid inoculation, but increased it to mechanical inoculation in the summer. When the youngest leaf was inoculated, the age of the test plants (10-25 days after germination) did not influence transmission by aphid or mechanical inoculation.