Five new species of Platygastridae associated with mango pests in India are described. Synopeas procon sp. n., S. temporale sp. n., S. mangiferae sp. n. and Inostemma oculare sp. n. parasitise mango leaf gall midges, Procontarinia spp. (Cecidomyiidae), while Inostemma apsyllae sp. n. is associated with the psyllid Apsylla cistellata (Buckt.). Notes on a further two species, the platygastrid Trichacoides indicus Jackson and the ceraphronid Aphanogmus sp., associated with Procontarinia are given. A key to separate these parasites as well as comments on their biology and distribution are presented.

Tetrastichus hagenowii (Ratz.) and T. asthenogmus (Wtstn.) are parasitic in cockroach oothecae and may themselves be attacked by a species of Tetrastichus of the group of T. miser (Nees). In Bangalore in 1976–79, the primary parasites were reared from oothecae of Periplaneta americana (L.), P. australasiae (F.) and P. brunnea Burm., and laboratory colonies of them were established on oothecae of P. americana. The hyperparasite, reared from field-collected oothecae of Periplaneta spp., was bred in the laboratory on oothecae of P. americana containing larvae of T. hagenowü. The immature stages of the three species of parasites were compared and their biologies studied. The eggs of the three species can be differentiated on the basis of their shape as can the pupae, but the larvae of the two primary parasites are indistinguishable. The duration of the developmental stages of the three species overlapped but the hyperparasite had a slightly shorter pupal period. Host finding by the T. hagenowii female was investigated. The two primary parasites were similar in most of their biological attributes. However, T. asthenogmus was inherently superior to the Bangalore strain of T. hagenowii in having lower levels of female sterility and its greater preference for the oothecae of P. brunnea, the predominant species of cockroach in Bangalore. T. hagenowii proved to be more tolerent of low temperatures than T. asthenogmus. The hyperparasite had an advantage over the other two species in possessing longer life-span and synovigenic females, and individual females parasitised more oothecae in their life-span than the primary parasites; but it was unable to distinguish healthy oothecae from those containing larvae of the other two species until it had drilled into them.

The literature on age-grading techniques of adult insects, published since 1968, is reviewed. The techniques described include those which deal with changes in the reproductive system, as well as somatic changes which take place with age. They also include techniques based on changes induced by wear and tear. Follicular relics found in different orders of insects are described, and their origin, fate and relative usefulness in age-grading studies are discussed. Attention is drawn to the formation of anomalous, or aberrant dilatations, particularly ones formed as a result of follicle resorption. The suitability of the various techniques to the study of different insect species is compared, and the advantages of using more than one type of age-grading method in the study of one species are discussed. Enough detail of each technique is given to permit field workers to choose and apply the technique most suitable for the study of the insect of their choice, and for the degree of accuracy required by them. Lists of species which have been studied by particular age-grading techniques, or combinations of them, are given. Finally, examples are cited of the types of problems entomologists have sought to solve, often successfully, using age-grading methods.

Following a long and varied history, Glossina control has become increasingly dependent upon the use of insecticides. There have been substantial successes with the use of chemicals, but reinvasion has been a constant, wide-spread problem. It is increasingly obvious that tsetse control must be approached on a large scale and requires international funding. Despite the proven ability of insecticides to reduce tsetse infestations there is a general reluctance to expand their usage and non-chemical methods are receiving increasing priority. In this paper, an attempt is made to put tsetse control into perspective. The literature relating to various insecticidal methods and tsetse control operations involving ground spraying, helicopter residual spraying, application of low dosage aerosols from fixed-wing aircraft and chemically impregnated traps is reviewed, and research and development relating to both the entomological and application aspects of chemical control are discussed. It is concluded that, given our present state of knowledge, insecticides provide the most reliable method for large-scale tsetse eradication. Of the methods available, applications of low dosage aerosols from fixed-wing aircraft have the greatest potential for rapid and effective control over large areas with minimal risk of non-target contamination, although refinements to improve efficiency and economy are needed. An integrated insecticidal approach combining the attributes of various chemical, and possibly non-chemical, control methods with the proven large-scale capability of spraying from fixed-wing aircraft could provide a realistic answer to the persistent Glossina and trypanosomiasis problems.

In certain areas of the Kenya coast, Culex quinquefasciatus Say is unable to maintain itself in breeding sites (flooded pit latrines) which it has to share with C. cinereus Theo. The pattern of settlement of the two species and the replacement of C. quinquefasciatus by C. cinereus were studied from May to November 1980 by monitoring newly emerged males as they departed from two breeding sites located in a small village near Mombasa. C. quinquefasciatus was the first species to be recorded from both sites, soon after they were flooded by the early rains. C. cinereus came later and did not increase markedly until after the late rains. The pattern of replacement of C. quinquefasciatus by C. cinereus was similar in the two breeding sites; the former species was unable to maintain itself once C. cinereus started to increase. Studies in another village showed that, after displacement, egg laying by C. quinquefasciatus continued but at a much reduced level. It is suggested that this is an example of competition-mediated succession occurring annually, with C. quinquefasciatus being better adapted to exploit rapidly the newly flooded sites but unable to sustain later competition from C. cinereus.

The effect of excluding the night-flying dung fauna, which included one abundant species of dung beetle (Scarabaeidae) in each of two areas, on the numbers of Musca vetustissima Wlk. emerging from cattle dung pads was studied in south-western Australia. Fresh dung pads were exposed to natural, daytime oviposition by M. vetustissima and half were covered at night. A test at one site before dung beetles emerged showed no effect of other nocturnal fauna on fly survival. In three experiments where Onthophagus ferox Har. was excluded, the numbers of flies emerging increased from 679 to 1019 per dung pad. In five experiments where Onitis alexis Klug was excluded, the number of flies emerging increased from 14 to 33 per dung pad. The mortality contributed by Onthophagus ferox was estimated to be around 27% and that by Onitis alexis around 15%.

Microencapsulated gossyplure or its component Z,Z-isomer were applied to 0·04-ha field plots in Arizona for disruption of sexual communication in adults of Pectinophora gossypiella (Saund.). In an initial efficacy test, the materials were placed on cotton plants in 50-μl drops by hand at a rate of 3·7 g a.i./ha (24 690 drops/ha). Trap catches were reduced by averages of 92 and 81% for the Z,Z-isomer or gossyplure treatments, respectively, during a one-week test period. Mating in mini-mating stations was reduced by 100 and 91% for Z,Z-isomer and gossyplure treatments, respectively. In a further test, sprays were applied using a Micron Herbi 77 hand-held spinning disc applicator that was calibrated to deliver 1·97 × 108 spray droplets/ha (about 250 μm in diameter and 0·01 μl/drop). The spray and drop methods were used to apply rates of 2·5 or 12·3 g a.i./ha of both materials to 0·04-ha field plots. The 12·3 g/ha rate of microencapsulated materials was necessary to give about 90% reductions in trap catches for the 9–12–day test periods. Gossyplure and its Z,Z-isomer gave similar reductions in catches when the same rates and method of application were used. However, comparisons of results for 50-μl drops vs. spray indicated that the drops generally resulted in significantly lower trap catches than sprays at the 2·5 g/ha dose rate. The results indicate that spray application of microencapsulated gossyplure or its Z,Z-isomer have potential for communication disruption of P. gossypiella.

The method and evaluation of a field application of rubidium chloride for the purpose of a mark-and-recapture experiment are described. In the Philippines, populations of the rice pests Nilaparvata lugens (Stål) and Sogatella furcifera (Horv.) were successfully marked by a foliar spray of rubidium chloride plus surfactant applied to a rice field at 1·03 g/hill. Individual insects marked with rubidium, which were easily distinguishable from unmarked individuals for at least seven weeks, were generated at this dose level, and even after one year elevated rubidium levels could be detected in pooled samples. Other phytophagous and entomophagous insects also became marked.

Widespread slight pyrethroid-resistance in Musca domestica L. on animal farms in southern England was correlated with strong resistance to trichlorphon and to malathion, and with the presence of an esterase, E0·39, detected by electrophoresis. In the laboratory, the frequency of E0·39 increased in response to selection with either pyrethroids or trichlorphon. Genetic analysis confirmed that this esterase, controlled by a gene on autosome 2, was closely linked with moderate resistance to trichlorphon and malathion and weak resistance to pyrethroids. When autosome 2 with the gene for E0·39 was introduced into a strain homozygous for the resistance mechanism super-kdr, resistance to pyrethroids increased by a factor equivalent to the weak resistance conferred by autosome 2 with E0·39 alone. Homozygosity for both mechanisms of resistance, and E0·39, was obtained by selecting the progeny of this cross with permethrin alone, permethrin and trichlorphon, or DDT and trichlorphon, demonstrating that very strong pyrethroid resistance can be achieved through the use of non-pyrethroid insecticides. E0·39 was absent from insecticide-resistant strains of M. domestica from Denmark but was present in several multi-resistant strains from other European countries.

Intensive monitoring of uncaged summer populations of Metopolophium dirhodum (Wlk.) (alienicolae) on winter wheat in southern England was carried out, mainly in 1979. Estimates for rates of development and reproduction are presented for both apterous and alate morphs. Relative nymphal instar lengths were calculated as percentages of the total juvenile period (instars I–IV inclusive), at a given mean temperature. The durations of the first three nymphal instars were uniform, but longer was spent in instars IV-apterous (21%) and IV-alatiform (45%) than in previous ones. Development rates are shown, firstly as cumulative summations of regression lines for individual instars, and secondly as a single regression for the whole period (I to IV inclusive), plotted separately against corresponding mean temperatures. A method of calculating the development threshold was devised that yielded an estimate of about 5°C for both morphs. Average and maximum daily rates of deposition (larviposition) are given for both morphs and, for apterae, results on the effects on this of leaf, date, temperature and aggregation are presented and discussed. Comparisons are made between this field study, and previous ones using M. dirhodum under constant temperature conditions in the laboratory. Development rates appeared to be similar under both constant and fluctuating temperatures, although slower in the field at low temperatures (10 or 11°C). Reproductive rates under the field conditions of this study appeared to be higher (on a daily rate basis) than those of previous studies, both in the laboratory (at constant temperature) and in the field. Reproduction in the field by apterae is considered to be concentrated over a shorter span of adult life than in the laboratory.

Scolytus intricatus (Ratz.) is a potential vector of oak wilt and is distributed throughout Europe wherever oak (Quercus) occurs. Its biology was studied in England in Monks Wood National Nature Reserve, Cambridgeshire, Alice Holt Forest, Surrey, and the New Forest, Hampshire, in 1977–83. S. intricatus was univoltine. Oviposition occurred from June to September in the bark of cut or weakened oak (Q. robur) over 5 cm in diameter. Eggs were laid in a single batch in maternal galleries cut across the grain of the cambium and phloem. The mean egg batch size was 17–36. Eggs hatched after 10–14 days, and the larvae ate the phloem and underwent five, or occasionally six, instars. The beetle overwintered as third-fifth-instar larvae, which were cold hardy and were located in cells in the phloem or outer xylem. Pupation occurred in spring, in cells in the bark or outer xylem. Emergence occurred between mid-May and mid-July and spanned a period of 3–4 weeks. The sex ratio was 1:1. Males and females differed externally by the presence of a tuft of setae on the frontal-clypeal suture of the head of the male. Newly emerged adults fed on twigs of live oak, but twig feeding was not obligatory for sexual maturation. Mating was observed during attacks on new hosts, which occurred in June-September. The eulophid Entedon ergias Wlk. was an endoparasite of larvae while larvae of the dolichopodids Medetera and Dolichopus and woodpeckers were predators.

Recent studies on the ecology of two cereal aphid species, Sitobion avenae (F.) and Metopolophium dirhodum (Wlk.), are reviewed. The most important factors affecting their abundance were used to construct decision trees to assess the risk of outbreaks of these species in the summer in England. These factors for S. avenae were crop sowing date, the size of the autumn migration, the severity of the winter, the size of the spring migration and the incidence of natural enemies in spring and early summer. For M. dirhodum, only the last two factors were considered as it does not occur on cereals until the spring in England. These decision trees were successfully tested using field data from 1983, when no outbreaks of either species occurred due to the effects of natural enemies.

The aphelinid Encarsia bennetti sp. n. is described from material collected in India and associated with Aleurocanthus woglumi Ashby, a pest of citrus.

Wavelength dispersive X-ray fluorescence spectrometry was used to make quantitative determinations of the elemental composition of adults of Noctua pronuba (L.) that had been reared on eight soil-plant combinations and a semi-synthetic diet. There were two host-plants, beans and lettuce, each grown in two clay soils of different acidity, a sand and a commercial potting compost. Analyses were done for fifteen elements: K, P, S, Mg, Ca, Cl, Zn, Si, Al, Fe, Cu, Mn, Ni, Cr and Ti. Two groups of elements were distinguished; the first six, or major elements, each with an average content about equal to or more than 1000 μg/g, and the last nine, or minor elements, each with an average content of <1000 μg/g. The second group was subdivided into four, Zn, Si, Al, Fe, each with an average content of >100 μg/g and four, Cu, Mn, Ni, Cr, of <100 μg/g; Ti was of erratic occurrence and was excluded from most statistical analyses. When all elements in all soil-plant combinations were considered, principal components analyses showed no distinction between insects reared on any soil-plant combination, probably because of interactions between host-plants and soils. When data were grouped into two host-plant subsets and only the major elements were analysed, soils were separable within each host-plant subset. In each case, the two clay soils were clearly separable from the other two soils but not from each other. In both host-plant subsets, sexes were distinguishable by a consistently higher K content in males. No clear separations were evident in either host-plant subset when all eight minor elements were considered or when these were separated into two further groups. This work indicates that (i) characteristic elemental compositions, or chemoprints, are present in N. pronuba; (ii) choice, not necessarily number, of elements is likely to be critical in describing and interpreting chemoprints; (iii) chemoprinting is unlikely to enable sources of populations to be identified in polyphagous species like N. pronuba; and (iv) the environmentally linked variation in chemical composition, affecting biologically essential elements, may have important consequences in the population dynamics of migratory and parthenogenetic species.

Tolerance of bioresmethrin, permethrin, deltamethrin and the natural pyrethrins with and without synergists (piperonyl butoxide and propyl prop-2-ynyl phenylphosphonate), and the frequency of kdr homozygotes (flies surviving a discriminating dose of DDT+FDMC (1,1-bis(4-chlorophenyl)-2,2,2-trifluoroethanol)) was investigated in 42 strains of Musca domestica L. collected on British pig farms and in one Canadian strain. Although all field strains were at least 4–10 times more tolerant of synthetic pyrethroids at the LD50 than the standard susceptible Cooper strain, and 27 strains (26 British + 1 Canadian) had detectable levels of kdr, pyrethroids failed to control flies on only nine farms where 10% of flies or more were homozygous for kdr and/or the LD50s (in μg/female) in bioassays equalled or exceeded 0·1 for bioresmethrin, 0·12 for permethrin, 0·012 for deltamethrin or 1·1 for pyrethrins. These figures correspond to resistance factors (Cooper strain = 1) of 20, 15, 30 and 4, respectively. Regression analyses showed a close relationship between the LD50s to pyrethroids and the frequency of kdr homozygotes. Cross-resistance to trichlorfon, which in part results in the 4–10-fold increased tolerance to pyrethroids observed in strains lacking kdr, was insufficient to cause control failure. The quantification of the relationship between the frequency of an insecticide-resistant genotype, levels of resistance as measured by bioassays and control failure in the field provides the means of forewarning when control failure is likely to occur and of confirming resistance as the cause when it has taken place.

Studies on populations of Zeiraphera diniana (Gn.) in Britain, where the tortricid has recently attained pest status, revealed differences in their structure and host-plant relationships when compared with populations at other European localities. A switch from the predominance of larch (Larix decidua) as a host in alpine Switzerland to pine (Pinus contorta) in upland Britain was governed by temperature which, during the egg stage, altered the phenological relationships between hatching caterpillars and foliage on the two conifers. Larvae which originated from populations on pine had higher survivorship on foliage of spruce (Picea) and larch than populations which originated on larch. Larval age heterogeneity, induced by a prolonged egg hatching period, was a marked feature of British populations and could have significant demographic consequences including an occasional reduction in the degree of temporal separation of racial units at the adult stage. Patterns of polymorphism in larval samples from Pinus contorta and Larix spp. in a variety of forests in Britain gave support to a hypothesis of racial hybridisation at the edge of the insect's range. There were overall differences between colour-type structure of larvae on larch at an English site and at a comparable Swiss locality, and also a similar trend in the change of a colour-type index with changes in population density between years. This suggests that similar selective forces may apply to the population dynamics of Z. diniana throughout its range.

Phorodon humuli (Schr.) was obtained from both wild and cultivated hop plants, cultured, and bioassayed using seven different foliar spray insecticides, and the results were assesssed by probit analysis to determine LC50s and LC95s. The wild aphids and their progeny were highly susceptible to the insecticides, whereas those from cultivated hops were generally resistant to them. The level of resistance was related to the source of the original aphid population and the insecticide used. Clones of insecticide-resistant and susceptible aphids were maintained under identical conditions, and individual adult apterae were assayed for total esterase and esterase isoenzyme activities. Total esterase activity was appreciably higher in resistant aphids than in susceptible ones. Resistant aphids were associated with high esterase isoenzyme activity of complex bands II–V, while in susceptible aphids these bands were virtually missing. An insecticide-resistant clone of P. humuli was selected for low esterase activity and a susceptible clone was selected for high esterase activity, over eight generations. Selection pressure was then reversed for a further eight generations. The resistant clone lost its esterase activity by generation six and it remained low thereafter, whereas that of the control stock remained high. By contrast, the esterase activity of the susceptible clone remained unaltered by selection. The resistant clone also lost its resistance to both methomyl and methidathion.

A rickettsia-free (aposymbiotic) stock of Aedes polynesiensis Marks (POLY-A) was crossed with (a) three symbiont-infected stocks of A. polynesiensis (POLY-S from Samoa and POLY-N and POLY-T from Fiji), (b) A. pseudoscutellaris (Theo.) (PSE) from Fiji, (c) A. alcasidi Huang (ALC), A. scutellaris katherinensis Woodhill (KATH), A. s. malayensis Colless (MAL) and A. s. scutellaris (Wlk.) (SCUT), which occur to the west of Fiji and (d) an aposymbiotic stock of A. cooki Belkin (CO) from Niue. It was bidirectionally compatible with CO, but in all other crosses compatibility was high when POLY-A was the male parent and very low when it was the female parent. Backcross data suggested that the crossing type was maternally inherited. ALC and KATH were bidirectionally compatible; both were virtually incompatible with POLY-S and PSE, compatible with SCUT when the latter was the female parent, and compatible with CO when the latter was the male parent. POLY-S females were moderately compatible with a third Fijian stock of A. polynesiensis (POLY-V), and POLY-N and POLY-V were compatible with PSE. If, as in Culex pipiens L., rickettsia-like symbionts are responsible for cytoplasmic incompatibility, then aposymbiotic males should cross successfully with symbiont-infected females, whereas the reciprocal cross should be unsuccessful. Since PSE, MAL and SCUT contain symbionts, their crossing relationships are consistent with the hypothesis. However, ALC and KATH appear to be aposymbiotic and their crossing relationships conflict with the hypothesis. There is little evidence of behavioural barriers to mating between species, but whereas male hybrids of two eastern species were capable of normal insemination, male hybrids between western and eastern species gave very low insemination rates. The egg-hatch rates from backcrosses of female hybrids between western and eastern species to the parents were reduced.

The effects of chlorpyrifos resistance on fitness in Culex quinquefasciatus Say was evaluated in terms of life-span, fecundity, fertility and rate of development, and these parameters were integrated by calculating the intrinsic rate of natural increase. A chlorpyrifos-resistant strain from Tanzania had very significantly reduced biotic fitness compared to a standard susceptible strain, CfCA, from Sri Lanka. However, after five generations of backcrossing the resistant gene into the genetic background of the susceptible strain, fitness was found to be closer to that of the susceptible strain. The reduced fitness of the original Tanzanian strain therefore appears to be mainly due to background genetic factors rather than to the major resistance gene itself.

Based on data collected during regular, biconical trap sampling of Glossina palpalis palpalis (R.-D.) over two and a half years during and after two insecticide programmes in Ivory Coast, various analytical techniques were developed which allow the estimation of mortality rates and life-time fertility from ovarian age distributions of female flies. Data from trapping-out experiments were used to calculate the natural resilience of local populations. The results reveal that the dynamics of the populations showed considerable local variation, with two major types of sites. At those sites with large numbers of domestic pigs, the fly population was dense and showed a high degree of natural resilience and a low mean mortality rate, so that it could be selfsustaining through reproduction alone. At sites with few pigs, the fly population was scarce and showed a lower degree of natural resilience and a higher mean mortality rate such that the population could only be maintained by continuous input of immigrant flies. Studies of the natural dynamics of tsetse can be used to predict the likely effectiveness of alternative control schemes; fly mortality rates must be permanently increased in order to reduce fly numbers or infection rates to below some threshold for disease transmission.