The north-western European species of the glomeratus-group of Apanteles are revised. Sixty-four species are dealt with, of which twentythree are described as new. Two species, A. pieridis (Bouché) and A. pilicornis Thomson, are lifted from synonymy. Host records are based mainly on reared specimens examined by the author.

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.

Zanjoneura kenyana gen. et sp.n. is described from specimens collected on Caesalpinia spinosa in Kenya, and two species are transferred to Zanjoneura from Frutioidia. A key is given to the 18 genera of the Erythroneurini found in Africa.

More or less cursory examination of migrating birds in Cyprus revealed 115 of 2580 southward (fall) migrants and 177 of 22015 northward (spring) migrants to be infested by 167 and 797 ticks, respectively. Most ticks on fall migrants were Hyalomma marginatum marginatum Koch; others were Ixodes frontalis (Panz.), I. ricinus (L.), Haemaphysalis concinna Koch, and H. punctata C. & F., all representative of the Eurasian fauna. Most ticks on spring migrants were H. m. rufipes Koch; others were Amblyomma lepidum Dön., A. nuttalli Dön., and A. variegatum (F.), representative of sub-Saharan Africa, and Argas streptopelia Kaiser, Hoogst. & Horner, Ixodes eldaricus Dzhaparidze, and I. redikorzevi Olen. which probably attached to the hosts in the eastern Mediterranean area. In Africa and Eurasia, 16 arboviruses have been recorded from eight of these tick species, and also the agents of boutonneuse fever, Siberian tick typhus, Q fever, and tularaemia. The epidemiological potential of migrating birds is enhanced by the multiplicity of pathogens that may infect them and the biological diversity of ticks that may infest them. The remarkably wide distribution of Crimean-Congo haemorrhagic fever virus in Africa and Eurasia is likely to be due to intercontinental carriage of the virus and ticks by migrating birds.

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.

Screening of 38 selected juvenoids on Ceratitis capitata (Wied.) revealed that several aromatic compounds, mostly ethers of 6,7-epoxygeraniol and of 6,7-epoxycitronellol, inhibited hatching when administered to freshly laid eggs as 0·1% acetone solution. Application of juvenoids within 24 h before and after puparium formation caused disturbances in imaginal differentiation. Treated insects developed either into pupa-adult intermediates failing to emerge or into defective adults whose fecundity was severely decreased. Both earlier and later applications of juvenoids were less effective. The most active compound in topical assay on fully grown larvae was ethyl 10,11-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate, which inhibited emergence of 50% of treated insects at 0·01 μg/specimen and caused external deformities in 50% of emerged adults at 0·00001 μ/g/specimen. Four other aliphatic compounds (methyl 11-methoxy-3,7,11-trimethyl-2,6-dodecadienoate; ethyl 11-methoxy-3,7,11-trimethyl-2-dodecenoate; isopropyl 3,7,11-trimethyl-2,4-dodecadienoate; and isopropyl 11-methoxy-3,7,11-trimethyl-2, 4-dodecadienoate) and l-ethyl-4[(6,7-epoxy-3,7-dimethyloctyl)oxy] benzene were about five times less active. A concentration of 33 parts /106 of ethyl 10,ll-epoxy-5-oxa-3,7,11-trimethyl-2-dodecenoate in larval food caused deformities in 60% of emerged adults.

The results derive from three 24-h catches of Aedes aegypti (L.) (1190 females, 504 males) using human bait at Buguruni, Dar es Salaam, Tanzania, in April 1971. The diel periodicity of all females is predominantly diurnal (at least 99·83% arrive during daylight or twilight) and bimodal, with consistent peaks at 06.00–07.00 h (post-sunrise) and 17.00–18.00 h (pre-sunset). The diel periodicities of nullipars and pars, and of uninseminated and inseminated females are virtually identical. The diel periodicity of males is also bimodal but differs from that of females in that at least two-thirds (instead of about half) of the individuals arrive between noon and sunset, more activity occurs between 09.00 and 15.00 h, and the post-sunrise peak falls at 08.00–09.00 h. A large influx of nullipars one afternoon did little to modify the close correspondence between the diel periodicities of nullipars and pars on subsequent days. Females land on bait in all ovarian stages (I–V), but in these catches more than 80% of nullipars and pars were almost equally divided between stages I and II. Among nullipars relatively more uninseminated females, and among pars relatively more with relict eggs, land in stage I than do so in stage II. It is inferred that pars with relict eggs usually expel them between stages I and II. This work reveals the likelihood that (at least at Buguruni) the frequency of potentially infective bites on a given day could be monitored with acceptable precision by limiting the catch to seven hours and the part that was age-graded to two hours.

Studies were made of populations of adult Rhyssa persuasoria (L.) from various geographical regions. Morphometric analyses were based on the relative size of 32 maculae on various sclerites and the colour of the coxae and legs. Size was determined by measuring the wing length and thorax length. Various statistical procedures were applied to these data and also the ratios of wing length: maculation, and thorax length: maculation in an attempt to distinguish races of R. persuasoria from different localities. Regression analysis, analysis of variance and classification procedures separated some populations from others, the results of the different analyses being in broad agreement with each other. Within each population, maculation was typically linear, smaller specimens having relatively small maculae. Some sexually dimorphic differences were also demonstrated. There were two major geographical groupings: S.W. European and North African (W. France, Spain, Portugal and Morocco) and the remainder. There were some geographical differences within the remaining populations although all had links with one or more adjacent populations. The degree of maculation was shown to be related to the colour and texture of host-tree species, populations with low maculation scores being associated with tree species having dark, fissured bark and vice versa. It is suggested that degree of maculation is an expression of cryptic colouration, providing camouflage from predators. Determinations of heat-coma temperature for male R. persuasoria from climatically different areas showed that the response to high temperature differed between populations and was correlated with the temperature of the locality of origin. These differences between strains were apparent after several months of identical conditioning and are probably genetically based.

Potency in the male Culicoides melleus (Coq.) has been investigated by direct counts of spermatozoa liberated from spermatophores removed forcibly during copulation. At the first copulation, virgin males 12–24 h old transferred a mean (± s.d.) of 1156±210 sperm to the females. In a series of copulations in immediate succession (with a fresh virgin female at each mating in the series), the numbers of sperm transferred declined progressively to a mean of 72±88 at the seventh copulation. The percentage fertility was recorded in first egg batches oviposited naturally by females that partnered individual males at one of the copulations in an immediately successive series. Fertility remained essentially unchanged at its highest level (62–66%) for the first three copulations. It then declined through copulations 4, 5 and 6, and reached zero at the seventh copulation and beyond. The minimum number of sperm required to ensure full fertility in the first egg batch appeared to be about 600. Limited recovery of potency was exhibited by males mated three times in immediate succession, then kept 24 h and mated again.

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.

Precipitin tests of the blood-meals of the non-anthropophilic population of Aedes simpsoni (Theo.) in Bwayise showed that at least 62% of the meals were mammalian; none was certainly avian or reptile. The remaining 38% were mostly too far digested for identification. Of the positive mammalian feeds, 84% were of rodents and only 5%; were of primates, probably human. In laboratory choice experiments, approximately two-thirds of a sample of the Bwayise strain fed on rodent in preference to monkey. Precipitin tests on blood-meals of the Bwamba strain of Ae. simpsoni confirmed earlier findings that this strain is strongly anthropophilic. At least 86% of wild-caught individuals had fed on mammals, 65% of these specifically identified: 28% of the feeds were of rodents and 72% were of primates, mostly human. During a five-month study at Bwayise in 1969, eleven species of rodents were caught; 91% of the rodents diurnally active were Arvicanthis niloticus which contributed 38% of the total collection and was twice as active during the afternoon as in the morning. The remaining species were predominantly nocturnal. A close relationship was found between the times of activity of A. niloticus and the biting cycle of Ae. simpsoni. In feeding tests using the three commonest rodent species, Ae. simpsoni selected A. niloticus as often as, or more often than, the nocturnal rodent species. This preference was maintained over one generation reared in culture. It is suggested that A. niloticus is the major natural host of the Bwayise strain by reason of the synchrony between rodent and mosquito activity rhythms. The Bwayise strain does not normally feed upon wild primates, so explaining further the almost total absence of human cases of yellow fever in areas of Uganda where this mosquito is non-anthropophilic.

Long-term records of aphid catches on two sticky traps, one at Rothamsted (1942–64) and one at Broom's Barn (1960–64) are extended to 1973 and are supplemented by data from up to 12 sticky traps in sugar-beet crops in eastern England (1960–73). The incidence of yellowing viruses of sugar-beet between 1965 and 1973 showed no relation to aphid numbers, but between 1942 and 1973 the pattern of annual incidence was similar to that of numbers of Myzus persicae (Sulz.) trapped in May and June. Linear regressions of the incidence of yellowing viruses on numbers of M. persicae in May and June accounted for 28–57% of the variance, and on Aphis fabae group for 2–40% of the variance. It is concluded that sticky traps provide useful information for advisory entomologists and that there has been no general increase in aphid numbers over the last 30 years.

A knowledge of the often complex relationship between insect populations and their effects on the yield-forming processes of crops is useful for assessing pest status and for devising methods of minimising the effects of infestation on yield. After a preliminary section on definition of terms, consideration is given to ways in which insects injure plants and crops, particularly annual crops. Investigations into the yield-forming processes of unattacked crops can often provide useful insights into the likely effect of insect injuries on yield. The differences between the characteristics of individuals and populations are discussed, both of insects attacking plants, and plants responding to the attacks of insects. The distribution of insects on plants and on crops and the effect that this has on damage is considered, as is the time and duration of the attack in relation to the growth cycle of the crop. The components of plant resistance to insect attack are then discussed, especially tolerance and the various ways in which plants and crops compensate for injury. The review concludes with an examination of the quantitative relationships between numbers of insects or injuries and their effects on yield. The generalised response is a sigmoid curve relating an upper and lower plateau of yield where changes in the numbers of insects or injuries have little effect. Most relationships conform to some part of this curve, though few show all its features.

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.