In Lucilia cuprina (Wied.), cuticular bands are deposited most clearly on the mesothoracic post-phragmata, and up to ten such layers can be counted. The bands are deposited clearly only in response to fluctuating temperatures where the minimum temperature in a cycle falls below about 15·5°C. Growth bands are deposited whenever such a change in ambient temperature occurs and the deposition appears to show no inherent rhythmicity. The maximum width of the phragmata is more or less constant and the number of bands which can be distinguished depends upon how quickly the maximum width of the phragmata is reached. The rate of growth of the growth bands and their consequent width depends upon the maximum temperature experienced and the length of time the insect is maintained at that temperature in any cycle. Trials showed that the count of growth bands was an acceptable estimate of the actual age in days when temperatures rose 3·5°C or more above the threshold value of 15·5°C. With a greater temperature range, greater accuracy was achieved. The availability of protein food was shown to have little effect on the deposition of growth bands. A mean age in days was calculated for samples of field-caught flies of a uniformly young ovarian ‘age’ using the counts of growth bands and by working back in the temperature records from their sites of capture using the day-degrees method. Significant differences between the two estimates of age were taken to indicate the occurrence of developmental delays. These were attributable to shortages of protein food in the field and were associated with periods of drought. The method allows the demonstration that developmental delays have occurred but does not provide an accurate estimate of the duration of these delays. It does not permit the confident identification of delays imposed by shortages of oviposition sites.

An Agar/Parafilm membrane system, developed for feeding tsetse flies, was evaluated by comparing membrane-fed and goat-fed female Glossina morsitans morsitans Westw. with respect to the following: fly weight, meal size, trypsin levels and amount of protein in the posterior midgut, and the portion of midgut protein which is in the posterior midgut. In flies having the same prefeeding history, the digestive physiology of membrane-fed flies was not significantly different from those fed on goats. The offspring of membrane-fed flies were lighter, took smaller meals, and had less trypsin and protein in the posterior section of the midgut than did flies from the stock animal-fed colony. However the relationship between trypsin levels and protein in the posterior part of the midgut was the same in flies from animal-fed and membrane-fed colonies.

The Eriophyid gall mite, Aceria chondrillae (G. Can.), which is distributed from south-east Russia to Portugal, was studied in the Mediterranean region as part of a biological control programme against skeleton weed (Chondrilla juncea) for Australia. The mite induces the vegetative and flower buds of Chondrilla to form leafy galls in which the full life-cycle is completed, causing stunting of the plant and reducing seeding. The mite overwinters in the rosettes of C. juncea without inducing gall development or reproducing. Populations decrease markedly during winter, recover in spring and infestations spread rapidly during summer. Reproduction is sexual and spermatophores are deposited by the males. Amblyseius sp. preys on A. chondrillae without marked effect. Tests made by placing fully developed galls of A. chondrillae on 75 species of plant including certain Cichoriaceae closely related to Chondrilla showed that the mite was highly specific to Chondrilla. Comparative tests with four geographical strains of A. chondrillae against six forms of C. juncea of various geographical origins indicated that the strains were specialised to their usual host form of the plant. A Greek strain of the mite readily attacked the main Australian form of C. juncea, and this strain has been introduced into Australia as a biological control agent for the weed.

In the Jordan Valley of Israel, spread of tomato yellow leaf curl virus in tomatoes by Bemisia tabaci (Gennadius) was delayed by three field treatments: (1) a straw mulch at the time of sowing; (2) sprays every four days with azinphos-methyl or methidathion; and (3) a combined treatment of a straw mulch after germination plus azinphos-methyl sprays at four-day intervals starting ten days after germination. The protective effect of straw mulch lasted about three weeks, and then sharply declined. In laboratory tests adult whiteflies were attracted more to straw than to tomato leaves, and more to fresh (yellow) straw than old (grey) straw exposed to field conditions for 25 days.

Field studies with Glossina morsitans morsitans Westw. in Rhodesia showed that hand-net catches can reduce slightly the responses of males to mobile baits and can reduce female responses by three-quarters. Description is given of methods of operating baits in the absence of men and of methods of electrocuting flies as they fly near baits, alight on baits and respond to decoy tsetse. These techniques are more efficient and objective than hand-net catching.

A new species of sandfly, Psychodopygus lainsoni, is described from specimens captured in ‘ terra firme ’ rain forest at km 46 Altamira-Itaituba on the Transamazônica highway. In many respects the male resembles those of the squamiventris group, and the female is similar to those of other groups.

Descriptions are given of the collection and rearing of Psychodopygus lainsoni Fraiha & Ward and five sympatric species, P. carrerai (Barretto), a member of the P. squamiventris group, Lutzomyia anduzei (Rozeboom) and two undescribed species closely related to L. anduzei (Rozeboom) designated L. sp. no. 260.43 and 260.44, all from the Altamira region of the Transamazônica highway, Pará State, Brazil. Fungal contamination of rearing containers and a reluctance of reared flies to feed prevented the establishment of closed colonies of these silvatic species. Storage of P. lainsoni eggs at 15°C delayed hatching, and reduced hatch rates and larval viability. Pupal storage at 12°C failed to inhibit emergence. Diapause is reported in the egg stage of L. sp. 260.44.

Evidence gained using blowflies (Calliphora vicina R.-D., Lucilia sericata (Mg.), L. cuprina (Wied.) and Protophormia terraenovae (R.-D.) ), fleshflies (Sarcophaga spp.) and tsetse flies (Glossina spp.) in ligaturing experiments and by the injection of prepupal haemolymph (with added ecdysone) suggests that factors other than ecdysone, released in the posterior segments, may initiate pupariation. They could act as synergists for ecdysone. Puparium formation is reduced from 77·5±3·1% to 35·7±2·8% (P<0·001) if 50 ng α-ecdysone is injected through the anterior knot into the middle region of twice-ligatured Sarcophaga argyrostoma (R.-D.) larvae instead of into the abdomens of singly tied larvae. The pupariation score is increased to 57·2±4·8% if haemolymph from rounded-off prepupae is injected into the middle region of isolated abdomens. The uninjected posterior region sometimes darkens alone. Ligature of the abdomens of S. peregrina R.-D. and S. argyrostoma prepupae which have just reached the orange-peritreme stage before rounding-off confines the pupariation to the posterior segments.

The effects of retarding puparium formation for 12–24 h by the use of dopa decarboxylase inhibitors or by means of a loose constriction (‘ cummerbund‘) are reported because the location of the patches of cuticle which stabilise and darken as the inhibition slowly wears off implicates certain areas under the integument as the sites of production or secretion of puparial tanning hormone or ‘ posterior darkening factor ’. Retardation of pupariation results from the pressure stimulus applied to rounded-off prepupae because either a hormone is held back or an inhibitor is released as a consequence of the distortion of the cuticle by the cummerbund. When fleshfly larvae are tightly ligatured every hour in front of or behind the brain for 18 h after removal from a moist environment which inhibits pupariation, the percentage of larvae which pupariate in both situations suggests that the CNS itself can inhibit pupariation of the anterior region because of the presence of the stricture. This inhibition, which is not due to lack of oxygen, can be reversed by the presence of factors produced in the abdomen.

Circadian flight activity in the males and females of Anopheles gambiae Giles species A and B, A. melas (Theo.) and A. merus Dön. has been investigated using the acoustic actograph technique. In each species the pattern and timing of activity in males and females is almost identical. Cyclical activity continues in constant dark; the period of the cycle is approximately half-an-hour shorter in A. gambiae species A and half-an-hour longer in A. merus than in the other two species. In alternating 12 h light: 12 h dark, both sexes are active during the dark period, with peaks of activity following light-off and light-on. After light-off, the species become active in the following order: A. gambiae species A, A. melas, A. gambiae species B, A. merus. A. merus is approximately 20 min later than species A.

The neurosecretory cells of the pars intercerebralis, the corpus cardiacum and the corpus allatum were examined in histological sections of Glossina austeni Newst. females fixed at daily intervals over the first two cycles of pregnancy. Two groups of neurosecretory cells corresponding to the lateral and median cells of other insects were recognised. The median neurosecretory cells were found to undergo cyclic changes of net synthesis and net release, which were correlated with ovulation and larviposition. The single ellipsoid corpus allatum undergoes cyclic changes in volume and histological appearance which are correlated with changes in the volume of the milk gland.

Analysis by gas-liquid chromatography showed that flowers open at the time of the first generation of cabbage root flies, Erioischia brassicae (Bch.), contained nectars composed almost entirely of sucrose and fructose whereas those open during the second generation secreted fructose and glucose. There were qualitative as well as quantitative differences in the sugar composition of all the nectars analysed. In both generations, the most highly nutritive sources of nectars, 94% and 86% sugar solutions, were available from the umbellifers Anthriscus sylvestris and Heracleum sphondylium, respectively. Fructose and glucose were also the main sugars on pollen and anthers at the time of the second generation but, in addition, pollen samples contained large quantities of the sugar alcohol inositol. The surfaces of the pollen of the grasses Dactylis glomerata, Holcus lanatus and Arrhenatherum elatius all contained sufficient nutritive carbohydrates for maturation of the first batch of cabbage root fly eggs. One or more of the chemicals found only in water extracts of Arrhenatherum pollen was probably toxic to the flies. To obtain sufficient carbohydrates to mature the first batch of eggs, flies had to probe at least 1–2 mg of grass pollen each day, equivalent to the pollen produced daily by two flowering heads of Dactylis.

For three consecutive years the eggs, the immature stages and the emergent adults of Aedes cantans (Mg.) populations were sampled from a small woodland ditch in southern England with a view to constructing the life-table of the species. Estimates of the numbers of ‘viable’ eggs available for hatching and the size of the resultant adult population yielded an estimate of the probability of a ‘viable’ egg resulting in an adult. Estimating the mortality rates in different immature stages which occur simultaneously is known to be difficult. It was considered reasonable to rely on a generalised exponential survivorship model based on the assumption that the relative mortality rate during the duration of each instar of A. cantans is constant, but this rate may vary from instar to instar. The parameters of the model were estimated using experimental data on the duration and total incidences through regular sampling of different instars together with the estimate of the probability that a ‘viable’ egg would result in an adult. The survivorship picture thus obtained agreed closely with the survivorship pattern obtained using a graphical approach based on the construction of the stage-specific age distribution of the pre-adults, and then drawing a smooth curve through the age distribution to produce an approximation to the survivorship curve. Because mortality was similar in all three years, the three years' data were pooled to give estimates of the life-table parameters. These clearly showed that substantial population loss occurred in the first two larval instars of A. cantans.

The biology and host specificity of Dactynotus chondrillae (Nevsk.) and Chondrillobium blattnyi (Pintera) living on the weed Chondrilla juncea (Compositae, Cichoriaceae) have been studied in the Mediterranean region as part of the biological control programme against this weed for Australia. Both are recorded from south-eastern Russia to the western Mediterranean region. The two species are monoecious. D. chondrillae has a facultative sexual reproductive phase every year but Chondrillobium blattnyi reproduces indefinitely by parthenogenesis in the Mediterranean region. D. chondrillae feeds mostly on young shoots, has population peaks in the spring and in the autumn, and can damage Chondrilla in the field. Chondrillobium blattnyi is a leaf feeder capable of seriously injuring the rosettes, but it never occurs in large enough populations in nature to be damaging. To demonstrate specificity, both aphids were tested against various Cichoriaceae and other Compositae and also against 61 cultivated plant species belonging to 20 families. The two aphids were shown to be specific to the genus Chondrilla. In the laboratory D. chondrillae was less host restricted than the other aphid and it reproduced on Sonchus asper and Taraxacum officinale. Comparative testing with strains of the two aphids from various sources against various forms of C. juncea showed that each strain was adapted to the form of C. juncea occurring in its own geographic area. The southern French strain of these aphids was ill-adapted to the main Australian form of C. juncea, but a strain of D. chondrillae originating from the Italian Adriatic coast heavily infested this form. D. chondrillae was not considered to be specific enough to permit its introduction into Australia and the introduction of Chondrillobium blattnyi has been delayed until it can be shown that it cannot transmit virus diseases that affect lettuce.

Nymph and adult populations of Diclidophlebia eastopi Vondráček and D. harrisoni Osisanya were counted weekly on 3- or 4-year-old trees, Triplochiton scleroxylon, in Nigeria during 1966–71. D. eastopi showed successively larger peaks in late January or early February, mid-August, and early or mid-September; the smallest populations were in mid or late March. D. harrisoni showed peaks in February, late July or early August, and late October or early November, the second peak being the largest. Multiple regression analysis of Diclidophlebia populations against rainfall, saturation deficit, temperature and time showed that temperature had the greatest, although slight, effect on D. eastopi, while saturation deficit, through the host-plant, had a marked effect on D. harrisoni. D. harrisoni populations were dependent on the availability of young leaves. It is concluded that, to avoid attack by Diclidophlebia, transplanting of Triplochiton seedlings should be in late February or early March.

The dispersal and seasonal flight activity of the oak stem Phylloxerid (Moritziella corticalis (Kalt.)) was studied at three localities in southern England by means of field observations and by sticky trap and suction trap catches. Wind displacement of first-instar crawlers occurred mainly during the winter months (76.2%) when this stage of the life-cycle is most active and abundant. No desiccation of these larvae was observed. The flight period of the sexuparae extends from the end of July to the end of October, and in most years three peaks of flight activity were discernible. A succession of days with low temperatures sometimes prevented migration, but large catches usually followed these low temperature spells. Analysis has shown that the temperature threshold for flight was about 17·2°C. Individuals flying at the start of the flight period were significantly smaller than those flying at the end of the season, possibly because factors affecting the host-plant may also effect changes in breeding and development of the insect. In a frost gradient apparatus, the overwintering first-instar larvae of M. corticalis were cold hardy, the LT30 being -23·7°C.

Circadian flight activity in Anopheles stephensi List. has been investigated using the acoustic aotograph technique. In alternating 12 h light: 12 h dark (50 or 200 lx), both sexes are active during the dark period, with peaks of activity following light-off and light-on. Cyclical activity persists in constant dark and is inhibited and reset by prolonging the light period. There are small differences between the carriers of the alternative chromosomal arrangements 2R+ ( +/+) and 2Rb (b/b) and between the sexes. In +/+ females the period of the cycle in constant dark is approximately half-an-hour longer and, in LD 12:12, there is less activity at light-on than in both sexes of b/b or in +/+ males. The +/+ males appear to be less susceptible to the inhibitory effect of prolonging the light period, although the cycle is reset.

Sizes of young field-collected males of Glossina morsitans morsitans Westw. were compared with those of teneral males emerging in the laboratory from field-collected puparia. Based on the mean size, indications were that smaller flies in field populations were selected against for about seven months in the year. A method is described for estimating the proportion of flies lost in the field population, and for the calculation of standard deviations for the estimates. Estimates of the extent of elimination showed that up to 35·2% of the total fly population in the field was eliminated in the cool months and up to 75·5% in the hot dry months.

Psyllids are generally narrowly host specific and are restricted almost exclusively to perennial dicotyledenous plants. Psyllids are known vectors of plant diseases. In addition, the effects of salivary injection can be very severe, causing growth abnormalities in the plant. Psyllid development rates are related to the nutritive status of the host-plant and, as in aphids, the honeydew produced while feeding is low in nitrogen. Psyllids reproduce sexually and pass through five nymphal instars before becoming adult. The immature stages exhibit both morphological and behavioural adaptations to resist desiccation, and the life-cycle is often highly synchronised with host-plant phenology. Adult Psyllids are known to disperse up to eight miles on wind currents, although in general dispersal is less marked than in aphids. The mechanism of host-plant selection is probably chemo-gustatory. Capacity for population increase in Psyllids is more dependent on generation time than on female fecundity. Recorded Psyllid parasites include Diptera of the family Cecidomyiidae and a wide range of Hymenoptera. These parasite species are almost exclusively parasitic on Psyllids although there is little evidence for parasite–host specificity within the Psylloidea. Psyllid species from a wide range of geographical areas have similar predator complexes. Anthocorids, Syrphids, Coccinellids and Neuroptera larvae are the main predators. At high population densities nymphal mortality increases in a density-dependent manner with increasing density, whereas at low densities nymphal survival is enhanced by group feeding. Close parallels exist in the feeding biology of aphids and Psyllids, but aphids appear better adapted for the exploitation of unstable ephemeral food sources.