The tick infestation patterns observed during 1966–73 are described for wild animals and cattle on the northern plateau of north-eastern Zambia, the eastern plateau and the intervening Luangwa valley. The seasonal periodicity of adult Amblyomma sparsum Neum., as observed on buffalo, was similar to that of A. variegatum (F.). Five major depart ures from the patterns of infestation previously found in the Central Province were observed. Boophilus decoloratus (Koch) was partially or totally replaced on cattle by B. microplus (Can.).Rhipicephalus appendiculatus Neum. although present on wild fauna in the valley, was absent from cattle on the eastern plateau. R. evertsi Neum. was absent from much but not all of the northern plateau and occurred in very low numbers only on the cattle of the eastern plateau, yet was present on the wild fauna of the Luangwa valley. Hyalomma marginaturn rufipes Koch was practically absent from cattle on the northern and the eastern plateaux and from the wild fauna, except buffalo, of the valley; H. truncatum Koch was abundant on cattle on the northern plateau and on the wild fauna of the valley, but on the eastern plateau cattle it occurred in low numbers only. A. pomposum Dön, was found on cattle in one area of the northern plateau, the only specimen of Amblyomrna on that particular herd. These anomalous findings are discussed in relation to the situation elsewhere in Zambia and in neighbouring territories.

In this paper the present status of insect chemosterilants is reviewed. Chemosterilants may be categorised into eight main chemical groups. Practical control measures involving the use of chemosterilants are discussed, also the persistence of these substances when applied to the insect. The gross effects of chemosterilants on insect reproductive systems and also the effects on egg develpment when female insects are mated to chemosterilised males are described, including dominant lethality, reciprocal translocation, enzyme inhibition and sperm inactivation. The possibilities of recovery of fertility and insect resistance to the sterilising effects of chemosterilants are discussed. Endocrine misfunction and chemosterilant action are related. The only practical chemosterilants as control agents are the aziridines although mutagenic hazards associated with these substances preclude their widespread usage. The sterilising activity of certain insect hormone analogues and related substances encourages the belief that safe insect specific sterilising agents can be found.

Although Aphytis lingnanensis Compère is an important parasitoid of California red scale Aonidiella aurantii Maskell, several ‘races’ of A. lingnanensis exist which parasitize white louse scale Unaspis citri Comstock. The reproductive status of a white louse scale ‘race’ of A. lingnanensis that originated in Thailand was examined in relation to several populations (from Queensland, California and the Philippines) that parasitize California red scale. None of the wasps from red scale mated with individuals from white louse scale in small cages within 10 min, whereas control crosses all mated in that time. The two ‘races’ would therefore constitute independent reproductive entities (species) in sympatry in the field, although no consistent anatomical differences could be found between them, even with the aid of discriminant function analysis on the number of setae on the delta region of the forewing and the mesoscutum.

Aphytis lingnanensis from California red scale in Queensland mated readily with wasps derived from the same host species in California and the Philippines, and mating took place at random among individuals in mate choice tests. Although such results are equivocal, there are no reasons for suspecting that these different populations of A. lingnanensis from California red scale also comprise more than one species. The results obtained indicate that cross-mating tests designed to quantify reproductive isolation between sexual populations are inappropriate. They should rather be designed to establish whether individuals recognize one another as potential mates. The design of cross-mating tests should therefore consider the usual time to mating, of known conspecifics, under the experimental conditions to be used.

The distribution of the almond wasp, Eurytoma amygdali End., as a major pest of almonds in areas of the eastern Mediterranean, a general outline of its seasonal history, and studies on the biology of the adult in Israel, have been reported previously (Plaut, 1971a). This paper presents data obtained in 1964–71 on the biology of the immature stages.

Aphid–plant interactions depend on genotypes of both organisms, which determine the two-way molecular exchange that leads to compatible or incompatible outcomes. The underlying genes are mostly unknown, making it difficult to predict likelihood of aphid success or host resistance, and hampering crop genetic improvement. Here we screened eight pea aphid clonal genotypes collected from diverse legume hosts, on a species-wide panel of Medicago truncatula (Mt) genotypes. Aphid virulence was measured by survival, fecundity and growth rate, together with scores for chlorosis and necrosis as host response indicators. Outcomes were highly dependent on the specific aphid–host genotype combinations. Only one Mt line was fully resistant against all clones. Aphid-induced host chlorosis and necrosis varied greatly, but correlated with resistance only in a few combinations. Bi-clustering analysis indicated that all aphid clones could be distinguished by their performance profiles across the host genotypes tested, with each clone being genetically differentiated and potentially representing a distinct biotype. Clones originating from Medicago sativa ranged from highly virulent to almost completely avirulent on both Medicago species, indicating that some were well adapted, whereas others were most likely migrants. Comparisons of closely related pairs of Australian Mt genotypes differing in aphid resistance revealed no enhanced resistance to European pea aphid clones. Based on the extensive variation in pea aphid adaptation even on unfamiliar hosts, most likely reflecting multiple biotype-specific gene-for-gene interactions, we conclude that robust defences require an arsenal of appropriate resistance genes.

The European winter moth, Operophtera brumata, is a non-native pest in the Northeastern USA causing defoliation of forest trees and crops such as apples and blueberries. This species is known to hybridize with O. bruceata, the Bruce spanworm, a native species across North America, although it is not known if there are hybrid generations beyond F1. To study winter moth population genetics and hybridization with Bruce spanworm, we developed two sets of genetic markers, single nucleotide polymorphisms (SNPs) and microsatellites, using genomic approaches. Both types of markers were validated using samples from the two species and their hybrids. We identified 1216 SNPs and 24 variable microsatellite loci. From them we developed a subset of 95 species-diagnostic SNPs and ten microsatellite loci that could be used for hybrid identification. We further validated the ten microsatellite loci by screening field collected samples of both species and putative hybrids. In addition to confirming the presence of F1 hybrids reported in previous studies, we found evidence for multi-generation asymmetric hybridization, as suggested by the occurrence of hybrid backcrosses with the winter month, but not with the Bruce spanworm. Laboratory crosses between winter moth females and Bruce spanworm males resulted in a higher proportion of viable eggs than the reciprocal cross, supporting this pattern. We discuss the possible roles of population demographics, sex chromosome genetic incompatibility, and bacterial symbionts as causes of this asymmetrical hybridization and the utility of the developed markers for future studies.

Monthly observations were made of the numbers and nutritional state of Glossina morsitans morsitans Westw. and the numbers of game animals in an 11 km2 block of woodland in Rhodesia. After 31 months the block was enclosed by a warthog-proof fence and nearly all of the warthog inside were removed rapidly. Tsetse diet switched from 80% warthog to 40–80% bovid (mainly kudu), 20–50% elephant and 0–20% warthog. Six months later elephants were driven from the block and bovids then formed about 90% of tsetse diet for the next year. Although the selective removal of hosts produced a clear stress, it had no drastic effect on the numbers and nutritional state of tsetse when compared to these features of a control population. Movement of tsetse into the enclosed area can account partly, but not fully, for this. The effects of routine hunting operations on a tsetse population are also reported.

An often encountered problem associated with augmentative and inundative biological control programmes is the high cost of producing sufficient numbers of natural enemies necessary to suppress pest populations within the time constraints imposed by ephemeral agroecosystems. In many arrhenotokous parasitoids, overproduction of males in mass-rearing cultures inflates costs (per female) and thus limits the economic feasibility of these biological control programmes. Within the context of existing production technologies, experiments were conducted to determine if the sex ratio of Catolaccus grandis (Burks), an ectoparasitoid of the boll weevil Anthonomous grandis Boheman, varied as a function of boll weevil larval size. Results from natural and manipulative experiments demonstrate the following behavioural characteristics associated with C. grandis sex allocation behaviour: (i) female C. grandis offspring are produced on large size hosts and male offspring are produced on small hosts; (ii) whether a host is considered large or small depends upon the overall distribution of host sizes encountered by a female parasitoid; and (iii) female parasitoids exhibit a greater rate of increase in body size with host size than do male parasitoids. The observed patterns cannot be explained by sex-specific mortality of immature parasitoids developing on the different host size categories. In subsequent experiments, laboratory cultures of C. grandis exposed daily to successively larger sizes of A. grandis larvae produced successively greater female biased offspring sex ratios, cultures exposed daily to successively smaller sizes of host larvae produced successively greater male biased offspring sex ratios, and cultures exposed daily to equivalent host size distributions over time maintained a uniform offspring sex ratio. By increasing the average size of A. grandis larval hosts exposed to C. grandis by 2.5 mg per day in mass rearing cultures, the percentage of male progeny can be reduced from 33% to 23% over a period of four consecutive exposure days.

The cixiid species Reptalus quinquecostatus, R. cuspidatus, R. panzeri and R. melanochaetus are widely distributed in Europe and are receiving growing attention because of their potential role as phytoplasma vectors. Identifying the Reptalus species is restricted to a few specialist entomologists and relies on the morphology of the male genitalia, hampering the identification of juveniles and females. This study provides the tools for species discrimination by integrating the morphological description, which is primarily for the genus identification, with new molecular assays, based on both ribosomal and mitochondrial DNA. PCR-RFLP assays carried out on the mitochondrial cytochrome oxidase I gene (COI) with AluI provided species-specific profiles for the four Reptalus species. Amplification of a ribosomal internal transcribed spacer (ITS2) region produced species-specific fragments of different sizes for R. quinquecostatus, R. melanochaetus, R. cuspidatus and R. panzeri. The digestion of the ITS2 PCR product with TaqI allowed the discrimination of these latter two species. This molecular identification key ensures reliable results and can be successfully applied not only to adults, but also to the nymphs feeding on the roots. The identification of the nymphs (i) extends the collection period of these monovoltine species to the whole year (adults are present for a short summer period) and (ii) allows the unambiguous identification of their actual host plants because nymphs are steady on the root system while adults tend to disperse onto other plants. Fast and reliable identification of the Reptalus species provides useful help in monitoring activities and, therefore, in designing rational control strategies to protect crops from phytoplasma infection.

Egg parasitoid rearing on factitious hosts is an important step to reduce costs and increase availability of the biocontrol agent but it requires quality control to achieve success in field conditions. To this end, this study evaluated the quality of Telenomus remus (Hymenoptera: Platygastridae) reared on Corcyra cephalonica (Lepidoptera: Pyralidae) for until 45 generations. In the first bioassay, we evaluated the body size of the laboratory-produced parasitoids. In the second bioassay, flight activity was examined, measuring the percentage of ‘flyers’, ‘walkers’ and ‘deformed’ parasitoids. The third bioassay assessed parasitism on Spodoptera frugiperda (Lepidoptera: Noctuidae) eggs. Our data indicate that the laboratory-reared parasitoid neither lost its ability to fly nor to parasitize S. frugiperda eggs. In conclusion, quality did not decrease significantly during 45 generations, and therefore rearing of T. remus on C. cephalonica as factitious host promises to be successful.

The gracillariid leaf miner Dialectica scalariella (Zell.), which occurs in Mediterranean Europe, North Africa, the Middle East and the Canaries, is a potential biological control agent for the weed Echium plantagineum in Australia. The moth has a high fecundity and oviposits on the leaves of Echium spp. and other Boraginaceae. The larvae destroy the leaves by forming large bulbous blotch mines. There are 5-7 generations per year. Host restriction of D. scalariella to Boraginaceae was tested by exposing a wide range of cultivated plants considered to be most at risk from it because of their close relation to Boraginaceae, because they were of Australian or non-European origin, because they did not occur in the same ecoclimatic region as D. scalariella, because their entomological fauna was poorly known, and because they or related plants were known to be attacked by insects closely related to D. scalariella. The host restriction of the moth was confirmed as only boraginaceous plants were attacked. It was concluded that both in terms of effectiveness and specificity D. scalariella could serve as a biological control agent in Australia for E. plantagineum.

Host characteristics, hyperparasitism, larviposition behaviour and generation time of Sarcophaga penicillata Villeneuve a parasitoid of the conical snail, Cochlicella acuta Müller (Mollusca: Helicidae) in southern France are described. Only snails which aestivated on vegetation were found to be parasitized by S. penicillata. Sarcophaga penicillata preferred C. acuta which were both significantly higher off the ground and larger in size than the population averages. Of the 2768 snails collected at the study site, 4% (112) were parasitized by S. penicillata, of which 36.6% (41) failed to emerge while 34% (38) were hyperparasitized. The predominant hyperparasite was Novitzkyanus cryplogaster Bouček (Hymenoptera: Pteromalidae) which was responsible for 79% (30) of the hyperparasitism. Larvipositing S. penicillata were observed to fabricate a hole in the epiphragm of resting snails in which they deposited one larva. After larviposition, female S. penicillata remained with the freshly parasitized snail a mean time ± SE of 25.2 ± 10.3 min. It is suggested that this may be an adaptive response to avoid superparasitism. The mean generation time of S. penicillata when reared in the laboratory was 18 days, indicating that more than six generations are possible during summer in the south of France. During winter, S. penicillata enters diapause in the pupal stage within a host snail for up to 6 months. The possible utility of S. penicillata as a biological control agent of introduced conical snails is discussed.

Field studies were conducted in Florida to investigate the behaviour of night-flying mosquitoes including Aedes sollicitans (Wlk.), Ae. taeniorhynchus (Wied.), Anopheles atropos D. & K., An. crucians Wied., Culex nigripalpus Theo., Culiseta melanura (Coq.), Deinocerites cancer Theo., Psorophora columbiae (D. & K.) and (Uranotaenia lowii Theo.) in relation to visually conspicuous objects. Adults of all species except Ae. sollicitans were taken in greater numbers in a large weathered plywood suction trap covered with black panels than in one without panels. However, both traps were attractive, as a transparent plastic suction trap covered with weathered plywood panels took larger numbers of all species except U. lowii than a transparent trap without panels. Buried suction traps furnished with visible risers (extensions) that made captures at 1·2 m elevations always captured proportionately larger numbers than buried traps with visible baffles that captured mosquitoes at ground level. A woodland species, C. nigripalpus, was captured in larger numbers toy traps furnisihed with visible risers and baffles than in traps furnished with transparent risers and baffles; however, collections of field species, e.g. Ae. taeniorhynchus, were smaller. The distribution of blood-fed and gravid females in collections from these traps provided some evidence that blood-seeking females are more responsive to visible objects than engorged or gravid females. These results are compatible with the hypotheses that (1) mosquitoes are attracted from a distance to visible objects, (2) in close proximity an avoidance action occurs and mosquitoes then pass over or around the visible object and (3) woodland species approach visible objects closely (<30 cm), whereas field species pass by at greater mean distances. Consequently, a larger percentage of visually attracted woodland mosquitoes than of visually attracted field species will be captured by suction traps. Depending upon trap design and specific behaviour, increasing the visibility of a suction trap can either increase or decrease trap collections

The development of adults of Nilaparvata lugens (Stål) reared on one susceptible and one resistant variety of rice plants of different ages was compared. Throughout the range of plants tested there was an overall trend for the newly moulted adult to synthesise and store a reserve of lipid and to lose most of the stored glycogen accumulated during the nymphal stage. N. lugens has two wing morphs, and whilst lipid deposits were greatest in the macropterous ‘migrant’ males, in females it was the brachypterous ‘reproductive’ insects that had the highest lipid deposits and also the greatest residual body weight. However, because of their lower body weight, the macropterous females had the greater percentage of lipid. Both flight willingness and the percentage of macropterous females showing flight-orientated physiological development increased with the age of the host-plant. Both survival and migration potential were lower in insects reared on the resistant rice variety compared to those reared on the susceptible variety. The pattern of post-flight resynthesis of fuels suggests that more than one major migration is unlikely.

The taxonomic status of the western Palaearctic crop plant pests Trioza nigricornis Först., T. tremblayi Wagn. and T. brassicae Vasil'ev is discussed, and a related species T. trigonica sp. n. (of which the probable host-plant is carrot) is described. Each species is fully illustrated, and a key to them is provided.

The biased nature of the catches of Glossina swynnertoni Aust. made on fly-rounds at Shinyanga, Tanganyika Territory, which show an unduly low proportion of females, nearly all of which are hungry, and lack of knowledge of the fly's habits when inactive, has led to a search for resting flies.

Previous recorded observations on resting tsetse flies are briefly reviewed. These show that the resting sites chosen differ according to species and even within a species. Differences of the second kind probably reflect seasonal changes.

Diagnostic molecular markers for the females of Phlebotomus (Paraphlebotomus) caucasicus and P. mongolensis were sought by characterizing from individual Iranian specimens a gene fragment, namely mitochondrial cytochrome b, that had previously proven useful for the taxonomy of phlebotomine sandflies. Males of both species were used as reference material because their external genitalia provide the only diagnostic morphological characters. A phylogenetic analysis of the new sequences, and those previously reported for P. grimmi, found no support for recognizing more than one species (P. caucasicus s.l.) in Iran. Most of the genetic variation was geographical. An absence of lineage sorting was demonstrated, and it is proposed that any search for species-specific molecular markers for these three taxonomic species should be continued by applied biologists only if there is better evidence for associating any one of them with phenotypes important for understanding the transmission of Leishmania species in foci of zoonotic cutaneous leishmaniasis.

A method of calculating survival rates and population size from mark-recapture experiments for bait-caught haematophagous insects is presented. The method fits the data to a series of simultaneous equations. This procedure is not affected by the cyclical nature of the recapture rate experienced in this type of experiment. Methods are presented which allow estimates of the confidence limits on the estimated parameters. Unlike earlier methods based upon a regression analysis of the log (number recaptured), this method allows estimates of the population size in addition to the survival and length of the feeding cycle of the mosquitoes. The methods have been applied to data collected in Papua New Guinea and give estimates of the total number of Anopheles feeding per night in different villages ranging from 3000 to 46 000.

Laboratory experiments with juvenile hormone analogues on Cydia pomonella (L.) showed that Cecropia C17 juvenile hormone (methyl 10,ll-epoxy-3,7,ll-trimethyl-2,6-dodecadienoate) was the most active of the 28 compounds tested. When applied to four-hour-old eggs at 0.1 μg/egg, the hormone caused 100% failure in embryogenesis, while the other compounds were at least five times less effective. Depending on the time since ecdysis and the dose, juvenile hormone mimics applied to last-instar larvae resulted in a wide range of intermediate forms. Against three-day-old last-instar larvae, the Cecropia C17 hormone gave 100% inhibition of development at a dose of 1 μg/larva, while three other compounds (methyl 10,11-epoxy-3,7,11-trimethyl-2,6-dodecadienoate, ethyl 11-chloro-3,7,11-trimethyl-2-dodecenoate and ethyl 3,7,11-tri-methyl-2,4-dodecadienoate) gave the same effect at 2–5 μg/larva. Against newly emerged adults, the last two compounds at 10–50 μg/insect reduced fecundity and fertility to 0–81% and 0–50%, respectively, of their normal levels.

A method is described for optimizing models by linking simulation procedures with a non-linear regression programme. It is then possible to work towards a parsimonious model which contains those, and only those, variables required for an optimum fit. Using the observed values, and the predicted values from each simulation, the optimizing routine calculates the value of an appropriate loss function. It then makes small changes in the parameters governing the simulation, recalculates the predicted values and the first and second derivative of the loss function with respect to each parameter. The algorithm uses this information to minimize the loss function for a given formulation of the model. The model is improved by adding variables which can be shown statistically to improve the fit, and by removing those which do not. The use of the technique is illustrated with reference to a series of weekly estimates of the total numbers, births and survival probabilities of a population of male and female tsetse flies Glossina morsitans morsitans Westwood. Simulation involved following the lives of cohorts of flies, and of all their progeny, from the time they were deposited as larvae. Development and reproduction were regarded as fixed functions of temperature, but mortality rates of pupae and of adult flies depended on meteorological and biological variables, plus the level of trapping imposed on the population. Potential factors were added singly and the model thereby improved in an objective, stepwise manner. The best fit was achieved when effects on adult survival due to maximum temperature, various modes of trapping, and an annual cycle were included in the model. The optimized simulation technique has been used here in improving a model which describes a biological population but it could equally be used to improve models in any situation where data are fitted using simulation procedures.