Methods of preparing solutions of graded density for the accurate control of atmospheric relative humidity are described, and some pitfalls in their use and in the use of saturated salt solutions are indicated.

For graded solutions of potassium hydroxide and of sulphuric acid, data from the International Critical Tables or more recent sources are used as the basis of tables giving the concentrations (wt.%) and densities corresponding to relative humidities in steps of 5 per cent. R.H. Sources of similar data for calcium chloride, sodium hydroxide, sodium chloride, and glycerol solutions are given.

As an addition to the compilation of the available data on humidities in contact with various saturated salt solutions by O'Brien (1948), some more recent figures are quoted.

From a critical review of the literature, it is concluded that the role of carbon dioxide in host-seeking by mosquitoes comprises two distinct actions. Firstly, it acts as an ‘attractant’, orientation towards the host being mediated by kinesis and optomotor anemotaxis. When tested in the absence of moving air currents, orientation to the source is not possible and only the kinetic or ‘activating’ effect is manifested. Moreover, in the absence of other host factors, sustained flight takes place only in response to intermittent pulses of carbon dioxide; this response is not elicited in uniformly permeated airstreams. Secondly, carbon dioxide has a combined action with warm moist convection currents at close range and with odour factors at a distance from the host.

Aerial dispersal using silk (‘ballooning’) has evolved in spiders (Araneae), spider mites (Acari) and in the larvae of moths (Lepidoptera). Since the 17th century, over 500 observations of ballooning behaviours have been published, yet there is an absence of any evolutionary synthesis of these data. In this paper the literature is reviewed, extensively documenting the known world fauna that balloon and the principal behaviours involved. This knowledge is then incorporated into the current evolutionary phylogenies to examine how ballooning might have arisen. Whilst it is possible that ballooning co-evolved with silk and emerged as early as the Devonian (410–355 mya), it is arguably more likely that ballooning evolved in parallel with deciduous trees, herbaceous annuals and grasses in the Cretaceous (135–65 mya). During this period, temporal (e.g. bud burst, chlorophyll thresholds) and spatial (e.g. herbivory, trampling) heterogeneities in habitat structuring predominated and intensified into the Cenozoic (65 mya to the present). It is hypothesized that from the ancestral launch mechanism known as ‘suspended ballooning’, widely used by individuals in plant canopies, ‘tip-toe’ and ‘rearing’ take-off behaviours were strongly selected for as habitats changed. It is contended that ballooning behaviour in all three orders can be described as a mixed Evolutionary Stable Strategy. This comprises individual bet-hedging due to habitat unpredictability, giving an underlying randomness to individual ballooning, with adjustments to the individual ballooning probability being conferred by more predictable habitat changes or colonization strategies. Finally, current methods used to study ballooning, including modelling and genetic research, are illustrated and an indication of future prospects given.

A simple method is described of testing the susceptibility to acaricides of larvae of the cattle tick Boophilus microplus (Can.) in Queensland, Australia, by enclosing them in packets made from rectangular filter papers, folded once and secured along the remaining three sides by spring clips, that had been impregnated with Risella-oil solutions of DDT, dieldrin, or Bayer 21/199 (coumaphos), or with deposits from xylene solutions of Dilan. The response of susceptible engorged adult females to dieldrin was tested similarly. Five out of six experiments showed statistical evidence of repeatability of results in determination of relative DDT-resistance of larvae. There was a slight increase in susceptibility of non-resistant larvae to DDT with increasing age between 7 and 28 days for fresh packets but not for re-used packets. In three out of four tests, re-used packets were significantly more toxic (up to 1·40 times) to susceptible larvae than fresh packets. In one test a loss of toxicity occurred after storage of Bayer 21/199 packets for 23 days. The possible use of this method for measuring resistance in ticks is discussed.

The known external characters, and some new ones, for separating the sexes of pupae and adults of stored-products Coleoptera are described and in many cases figured.

In Rhodesia, field studies were made of the initial attraction of G. morsitans morsitans Westw. and G. pallidipes Aust. to mobile and stationary baits, using flight traps which surrounded baits or which were placed in the densest part of the attracted swarm. With stationary baits, many flies were attracted by host odour and visual stimuli assisted final orientation. With mobile baits, many flies were attracted by visual stimuli alone; odour did not increase attraction. With both mobile and stationary baits, there was no indication that major hosts are much more effective than minor ones as initial attractants, although stationary men were exceptionally poor baits, for G. pallidipes especially. The sex and species compositions of catches from stationary baits other than men were representative roughly of the inactive population—70% females of both species, and a roughly 1:4 ratio of G. morsitans to G. pallidipes. The sex and species compositions of catches from all mobile baits were biased—40% female G. morsitans, 60% female G. pallidipes, and a roughly 2:1 species ratio. Nearly all flies attracted to stationary baits were hungry whereas 10–25% of both sexes visiting mobile baits had fed recently. The use of a variety of electrocuting devices showed that compact persistent responses and alighting reactions of attracted flies were evident more for males than for females, more for G. morsitans than for G. pallidipes, more near model animals with host odour than near odourless models, more near models than near men, and more with tenerals and hungry non-tenerals than with recently fed flies. Men with mobile baits depressed greatly the alighting reactions and with stationary baits men inhibited greatly the initial attractions. Both effects of men were greater with females than with males and greater with G. pallidipes than with G. morsitans. Men were recognised by their upright appearance and odour. Only desperately hungry flies probed men whereas less-hungry flies probed an ox with men. Food-seeking flies of differing nutritional state were not shown to distinguish between mobile and stationary baits. Although the results support the conventional view that mating and feeding functions in the response to hosts occupy distinct phases of the hunger cycle, it seems necessary to modify the conventional view by placing more emphasis on the role of mobile baits as food sources and by envisaging a definite mate-seeking response by mature females.

Global warming may affect the future pattern of many arthropod-borne diseases, yet the relationship between temperature and development has been poorly described for many key vectors. Here the development of the aquatic stages of Africa's principal malaria vector, Anopheles gambiae s.s. Giles, is described at different temperatures. Development time from egg to adult was measured under laboratory conditions at constant temperatures between 10 and 40°C. Rate of development from one immature stage to the next increased at higher temperatures to a peak around 28°C and then declined. Adult development rate was greatest between 28 and 32°C, although adult emergence was highest between 22 and 26°C. No adults emerged below 18°C or above 34°C. Non-linear models were used to describe the relationship between developmental rate and temperature, which could be used for developing process-based models of malaria transmission. The utility of these findings is demonstrated by showing that a map where the climate is suitable for the development of aquatic stages of A. gambiae s.s. corresponded closely with the best map of malaria risk currently available for Africa.

The coffee berry borer, Hypothenemus hampei Ferrari, is a serious problem for the majority of the world‘s coffee growers and has proved to be one of the most intractable of present day pests. Despite a great deal of research, control still depends largely on the application of the organochlorine insecticide endosulfan, which is damaging to the environment, or a series of cultural and biological control methods which give variable and unpredictable results. This review summarizes the most important aspects of the biology and ecology of H. hampei and its control and identifies weak points in the knowledge about this pest. Emphasis is placed upon an analysis of the non-chemical control methods available and suggestions are offered for novel ecological and environmental factors worthy of further research, in the search for viable and sustainable control methods.

The factors responsible for determining the host-plants and feeding sites of aphids, and the various probing activities (the role of the labium, stylet insertion, surface saliva deposition, the behaviour of the aphid, virus transmission) are examined. There is a brief review of stylet structure and movement and the possible sensory nature of these organs, followed by a detailed review of the characteristics of aphid stylet paths in plant tissues. The penetration of epidermis and vascular tissues is treated separately while that within the intermediate tissues is covered in relation to leaves and stems, roots, trees, galls and excised tissue as well as in separate sections on Aphis fabaeScopoli and Myzus persicae (Sulzer). Stylet destinations and behaviour in the sieve tubes are discussed together with general features such as rate and depth of penetration, guidance to the feeding site, effects of tissue hardness and stylet withdrawal. The ingestion rate of plant sap is reviewed and its constitution and importance examined together with the significance of artificial diets. The salivary secretions including sheaths and tracks, their functions and their role in the transference of material between aphid and host are dealt with. The nature of the physical and internal damage resulting from aphid feeding is briefly covered, and also some plant-insect interrelations. The aphid species whose stylets have been examined in plant tissue are listed.

The sweet potato whitefly, Bemisia tabaci, harbors Portiera aleyrodidarum, an obligatory symbiotic bacterium, as well as several secondary symbionts including Rickettsia, Hamiltonella, Wolbachia, Arsenophonus, Cardinium and Fritschea, the function of which is unknown. Bemisia tabaci is a species complex composed of numerous biotypes, which may differ from each other both genetically and biologically. Only the B and Q biotypes have been reported from Israel. Secondary symbiont infection frequencies of Israeli laboratory and field populations of B. tabaci from various host plants were determined by PCR, in order to test for correlation between bacterial composition to biotype and host plant. Hamiltonella was detected only in populations of the B biotype, while Wolbachia and Arsenophonus were found only in the Q biotype (33% and 87% infection, respectively). Rickettsia was abundant in both biotypes. Cardinium and Fritschea were not found in any of the populations. No differences in secondary symbionts were found among host plants within the B biotype; but within the Q biotype, all whiteflies collected from sage harboured both Rickettsia and Arsenophonus, an infection frequency which was significantly higher than those found in association with all other host plants. The association found between whitefly biotypes and secondary symbionts suggests a possible contribution of these bacteria to host characteristics such as insecticide resistance, host range, virus transmission and speciation.

The internal classification of genus Anopheles is updated to reflect taxonomic actions published since the classification was last reviewed in 1994. Both formal and informal taxa are included. The classification is intended to aid researchers and students who are interested in analysing species relationships, making group comparisons and testing phylogenetic hypotheses. The genus includes 444 formally named and 40 provisionally designated extant species divided between six subgenera: Anopheles, Cellia, Kerteszia, Lophopodomyia, Nyssorhynchus and Stethomyia. Subgenera Anopheles, Cellia and Nyssorhynchus are subdivided hierarchically into nested informal groups of morphologically similar species that are believed to represent monophyletic lineages based on morphological similarity. Changes to the classification include additional species, eliminated species and changes to the hierarchical organization and composition of supraspecific groups, some as a result of molecular studies.

Among the invasive mosquitoes registered all over the world, Aedes species are particularly frequent and important. As several of them are potential vectors of disease, they present significant health concerns for 21st century Europe. Five species have established in mainland Europe, with two (Aedes albopictus and Aedes japonicus) becoming widespread and two (Ae. albopictus and Aedes aegypti) implicated in disease transmission to humans in Europe. The routes of importation and spread are often enigmatic, the ability to adapt to local environments and climates are rapid, and the biting nuisance and vector potential are both an ecomonic and public health concern. Europeans are used to cases of dengue and chikungunya in travellers returning from the tropics, but the threat to health and tourism in mainland Europe is substantive. Coupled to that are the emerging issues in the European overseas territorities and this paper is the first to consider the impacts in the remoter outposts of Europe. If entomologists and public health authorities are to address the spread of these mosquitoes and mitigate their health risks they must first be prepared to share information to better understand their biology and ecology, and share data on their distribution and control successes. This paper focusses in greater detail on the entomological and ecological aspects of these mosquitoes to assist with the risk assessment process, bringing together a large amount of information gathered through the ECDC VBORNET project.

This review describes the major stored-product insect species and their resistance to insecticides. The economic importance of the control of those pests is highlighted with a loss of more than one billion US dollars per year worldwide. A detailed common description of species resistance throughout the world has been developed, and we observed 28 recurrent studied species involved in resistance cases disseminated on the five continents. The different mechanisms, including behavioral resistance, were studied particularly on Oryzaephilus surinamensis. The role of detoxifying enzymes and studies on the genetic resistance, involving the kdr mutation mechanisms and the transmission of the genes of resistance, are also described. A chapter clarifying definitions on cross and multiple resistance is enclosed.

The oriental fruit fly, Bactrocera dorsalis (Hendel), is a major pest throughout South East Asia and in a number of Pacific Islands. As a result of their widespread distribution, pest status, invasive ability and potential impact on market access, B. dorsalis and many other fruit fly species are considered major threats to many countries. CLIMEX™ was used to model the potential global distribution of B. dorsalis under current and future climate scenarios. Under current climatic conditions, its projected potential distribution includes much of the tropics and subtropics and extends into warm temperate areas such as southern Mediterranean Europe. The model projects optimal climatic conditions for B. dorsalis in the south-eastern USA, where the principle range-limiting factor is likely to be cold stress. As a result of climate change, the potential global range for B. dorsalis is projected to extend further polewards as cold stress boundaries recede. However, the potential range contracts in areas where precipitation is projected to decrease substantially. The significant increases in the potential distribution of B. dorsalis projected under the climate change scenarios suggest that the World Trade Organization should allow biosecurity authorities to consider the effects of climate change when undertaking pest risk assessments. One of the most significant areas of uncertainty in climate change concerns the greenhouse gas emissions scenarios. Results are provided that span the range of standard Intergovernmental Panel on Climate Change scenarios. The impact on the projected distribution of B. dorsalis is striking, but affects the relative abundance of the fly within the total suitable range more than the total area of climatically suitable habitat.

The genus Locusta, L. (= Pachytylus, Fieb.) includes two of the most destructive swarming locusts of the Old World: the widely distributed L. migratoria, L. (with L. danica, L., and L. migratorioides, Rch. & Frm., as its forms; see below), and the South African L. pardalina, Walk. The literature on the economics, biology and especially on the means of control of these locusts is enormously extensive, but at the same time their systematic arrangement is in considerable confusion, and extremely contradictory opinions as to the mutual relationship of the different so-called species exist among specialists. As a direct consequence of this, the field research and control work of economic entomologists is apt to suffer through the difficulty in getting a particular species properly named, and thus it is often impossible to make a comparison of the records as to the biology and control of the same species in different countries.

Adult Bemisia tabaci (Gennadius) were tested with imidacloprid in a bioassay method using systemically treated cotton leaves. The method was simple, robust and repeatable and provided baseline data for a laboratory and a number of recently collected field strains. The LC50 for imidacloprid susceptible strains was calculated to be 1.7 ppm and a concentration of 16 ppm determined as diagnostic for imidacloprid resistance. Ten strains of B. tabaci collected from the Almeria region of Spain showed significantly less mortality at the diagnostic dose than the susceptible strains. The intensive use of imidacloprid in the Almeria region is considered the reason for the occurrence of resistance in this locality. Resistance to organophosphates, pyrethroids and endosulfan in B-type and non-B type B. tabaci did not confer resistance to imidacloprid.

The rate of development of six species of Bruchidae (Acanthoscelides obtectus (Say), Zabrotes subfasciatus (Boh.) and four species of Callosobruchus) attacking stored pulses was studied over a wide range of constant temperature and humidity and the rate of oviposition of five of them investigated over a range of temperatures at 70 per cent. R.H. and a range of humidities at 30°C.

A hatch of the order of 80 per cent, of the eggs of A. obtectus, which are scattered among stored seeds, was recorded over the temperature range 17·5–30°C. at both 30 and 90 per cent. R.H. and over the range 15–35°C. at 70 per cent. R.H. None hatched at 40°C. The optimum conditions for rapid development of the egg are close to 30°C. and 70 per cent. R.H., where the egg hatched in just under five days. The period to hatching is increased at both lower and higher humidities as well as at lower and higher temperatures. The optimum for the rapid development of the post-oval stages is also 30°C. and between 70 and 80 per cent. R.H., in which conditions the first beetle emerged 20 days after the larvae were placed on haricot beans (Phaseolus vulgaris), the mean developmental period to adult emergence being 22·5 days, or 27·5 days including the egg stage. No beetles emerged at 35°C. and few at 15°C. Low humidity and very high humidity retarded development.

The eggs of Z. subfasciatus and the species of Callosobruchus are stuck to the seeds, and data for the egg stage were not obtained separately. The optimum for the rapid development of Z. subfasciatus on haricot beans is close to 32·5°C. and 70 per cent. R.H., where the first beetle emerged in 23 days and the mean developmental period was 24·5 days. No adults emerged at 37·5 or 17·5°C. and few emerged at 20°C. or at low humidity at 35°C.

The optimum conditions for rapid development of the species of Callosobruchus are 32·5°C. and 90 per cent. R.H. for C. chinensis (L.), about 30°C. and 70 per cent. R.H. for C. rhodesianus (Pic), 32·5°C. and about 70 per cent. R.H. for C. analis (F.), and 32·5°C. and 90 per cent. R.H. for C. maculatus (F.). None of the species could complete development at 37·5°C. and all four fared poorly at 35°C. Two species, C. chinensis and C. rhodesianus, were able to develop at 17·5°C. and the other two at 20°C. The performances of all the four species on dried garden peas (Pisum sativum) were poor; all did much better on cowpeas (Vigna unguiculata). The rate of development was slower on garden peas, the percentage mortality was higher and the developmental limits more constricted. In addition, the developmental period in all conditions on garden peas was so variable that the mean gave an unreliable estimate of performance and the time to the first emergence was used instead. The shortest mean developmental periods in days recorded were 22·5 for C. chinensis, 23 for C. maculatus, 25 for C. rhodesianus and 27 for C. analis. The shortest developmental period for an individual bred in garden peas was 18 days for C chinensis, 21 for C. maculatus and 26 for C. analis.

The sex ratio was close to unity throughout. The developmental period of the female was slightly longer than that of the male in A. obtectus and C. chinensis, and also in C. maculatus when bred in garden peas but not when bred in cowpeas. At 30°C. on cowpeas, breeding in mass culture at a low density gave rates of development similar to those observed with isolated insects in the cases of A. obtectus, Z. subfasciatus and C. chinensis, but with C. analis and C. maculatus a large proportion of those bred in mass cultures grew much more slowly than did isolated insects.

On garden peas, more than 50 per cent, of the eggs of the species of Callosobruchus grew to the free-living adult stage only in the most favourable conditions. For these species on cowpeas, and for A. obtectus and Z. subfasciatus on haricots, over 80 per cent, completed development over a wide range of conditions. Normally most of the mortality was of eggs or very young larvae, but at high humidity (80–100 per cent.) and at low (22·5°C. and below) and high temperatures (32·5°C. and above) a considerable number of individuals died after completing larval feeding, some after pupating.

In all the species studied except C. analis, at emergence the female was on average heavier than the male by 0·75–1·25 mg. In Z. subfasciatus, the weight range of the two sexes at any condition rarely overlapped. Callosobruchus spp. bred from cowpeas were heavier than those reared in garden peas. The heaviest beetles were bred towards the bottom of the temperature range, at 50 and 70 per cent. R.H. The weight decreased slightly at 90 per cent. R.H., more markedly at low humidity, slightly up to 30°C. and more abruptly at higher temperatures.

The rate of development of C. maculatus at 30°C. was shown to be. relatively consistent on several varieties of cowpea, the mean developmental periods on the best seven covering a range of less than 2 days (22·1 to 23·8). This mean was a further two days longer (25·7) on the two remaining varieties. Only one seed (Phaseolus aureus) from a series of ten other legumes had a mean developmental period within this range, and only from this seed and from P. mungo, brown peas and the nine varieties of cowpea were 30 or more beetles bred from 50 eggs.

The lengths of the various instars of C. chinensis were determined by the dissection of samples daily, and some information on the pupae of C. rhodesianus was obtained by the use of soft X-rays.

All the five species used in oviposition experiments were short-lived and had very short preoviposition periods after emergence. All laid at a maximum rate after 2 or 3 days, the rate falling quickly at high temperatures and more slowly at low ones. The highest mean number of eggs laid was 100 by C. maculatus, 75 by C. analis, 70 by A. obtectus, 50 by C. chinensis and 40 by Z. subfasciatus. C. analis and C. maculatus laid best above 30°C., and A. obtectus and Z. subfasciatus at 25°C. C. chinensis laid most eggs at 22·5°C., but the performance up to 37·5°C. was only a little inferior and varied irregularly from temperature to temperature; it was poorest at 20 and 17·5°C. The higher humidities (70–100 per cent. R.H.) were most favourable for all species at 30°C.

Eggs of Z. subfasciatus laid at 15°C. did not hatch at that temperature, and likewise eggs laid at 37·5°C. did not hatch at 37·5°C. Very few eggs laid at 25°C. hatched at 15°C., but about half of a batch laid at 30°C. hatched at 37·5°C. Otherwise about 60 per cent, hatched at 20°C., nearly 80 per cent, at 35°C. and 80 per cent, or more at all intermediate temperatures. At 30°C. hatching was good at all humidities including 2 and 100 per cent. R.H.

The results given in published work are compared with those obtained in this work. The value of the results in determining the pest potential of these species is discussed, and suggestions for the most profitable future lines of work are made.

In laboratory experiments, the responses to short photoperiod (10 h) of clones of Myzus persicae (Sulz.) established from random samples of summer populations in southern England were generally stable and characteristic for each clone, and were of four distinct categories: (i) holocyclic, with clones terminated under short photoperiod by production of male and female sexual forms, (ii) intermediate, with a mixed response involving alatae intermediate between gynoparae and virginoparae, (iii) androcyclic, with production of some males along with continued parthenogenesis, and (iv) truly anholocyclic, with no significant response to short photoperiod. All four types can occur within one population, but holocyclic and androcyclic forms are most common. There were clear differences in the proportions of these forms occurring simultaneously on adjacent crops of different host-plants, and in different years on the same crop in the same field. Males of androcyclic clones were able to transmit their partially anholocyclic character through the sexual phase.

A history of the changes in nomenclature within the genus Spodoptera is outlined. A key to the imagines of the eight species occurring in Africa and the Near East is presented, together with keys to the larvae and pupae of most of these species, including all those of economic importance in this region, as well as brief notes for identifying the eggs of six species. For each species, a separate account is given of its taxonomic features and affinities, general world and more detailed African distribution, as well as host-plants, including those of economic importance, and its vernacular names. The subspecies Spodoptera leucophlebia malagasy Viette, recorded only from the Malagasy Republic, has been raised to full specific status, and should now be known as Spodoptera malagasy Viette, stat. n.

The worldwide distribution and extensive genetic diversity of the whitefly Bemisia tabaci has long been recognized. However, whether B. tabaci is a complex species or a species complex has been a subject of debate. Recent phylogenetic analyses suggest that B. tabaci is a cryptic species complex composed of at least 24 morphologically indistinguishable species. Here, we conducted crossing experiments and demonstrated reproductive incompatibility among three of the 24 putative species. Our data and those of previously reported crossing experiments among various putative species of B. tabaci were collated to reveal the pattern of reproductive isolation. The combined results provide strong support to the proposition that B. tabaci is a cryptic species complex.