The attractiveness, to mosquitoes, of human subjects breathing normally and wearing a breathing apparatus which removed 95·5% of expired carbon dioxide were compared in the field. Significantly fewer mosquitoes approached the subject with a reduced carbon-dioxide output. Species differences were apparent in the degree of reduction of mosquitoes at the bait, as measured by the ratio of numbers attracted to subjects without and with the breathing apparatus. From the results of trials in the Gambia, West Africa, this ratio gave values of 0·67 for Mansonioides spp., 0·46 for Anopheles gambiae Giles/A. melas Theo. and 0·19 for Culex thalassius Theo., while complementary work in southern England gave a value of 0·34 for Aedes cantans (Mg.)/Ae. annulipes (Mg.). A reduced carbon-dioxide output had no effect on the proportion of mosquitoes attempting to feed once within close range of the host. These findings confirm that carbon dioxide is a long- or medium-range attractant.

Spodoptera exempta (Walker) occurs very widely in Africa south of the Sahara and in south-western Arabia, and more intermittently in the eastern Indian Ocean and Pacific areas. Throughout its range, the extent and frequency of its attacks have increased markedly, especially in the last 10–15 years. In parts of Africa and in south-western Arabia it is now regularly a seasonally important pest; examples are given of monthly distribution maps of the frequency of its attacks in this region. Maps such as these provide a useful and wide-based perspective for those concerned with prediction, survey and control of S. exempta in a more limited area and with little or no access to information from other territories. Year to year variations within the general patterns derived from many years' records are illustrated by the distribution of outbreaks in three recent seasons, in all of which there were outbreaks in at least seven countries of central and eastern Africa, in two years in Arabia, and in one year also in southern and western Africa.

Mating behaviour, sex pheromone attraction and reciprocal breeding of Cotesia flavipes Cameron (Hymenoptera: Braconidae), C. sesamiae (Cameron) and C. chilonis (Matsumura) were studied. These three putative species comprise the Cotesia flavipes complex. Wing fanning and antennal vibration were the initial courtship signals from the males. Antennal stroking by the male was also an important contact signal and a prerequisite to successful mounting and copulation. Interspecific crosses revealed that males of C. flavipes exhibited courtship behaviour, and mounted and copulated with females of C. chilonis and C. sesamiae; the males transferred sperm but progeny from these crosses did not include females. Males of C. sesamiae copulated with females of C. chilonis and the progeny included viable females. The progeny backcrosses of the hybrid females to male parents also included viable females. Sex pheromone experiments were conducted in a Y-tube olfactometer and in large field cages. Males and females of C. flavipes perceived and responded to odours emitted by the opposite sex. There was no significant response to odours from conspecific individuals of the same sex in any of the three species. Pheromone bioassays in field cages using sticky traps baited with live virgin C. flavipes females attracted conspecific males.

The sterile insect technique (SIT) has been proposed as an area-wide method to control the South American fruit fly, Anastrepha fraterculus (Wiedemann). This technique requires sterilization, a procedure that affects, along with other factors, the ability of males to modulate female sexual receptivity after copulation. Numerous pre-release treatments have been proposed to counteract the detrimental effects of irradiation, rearing and handling and increase SIT effectiveness. These include treating newly emerged males with a juvenile hormone mimic (methoprene) or supplying protein to the male's diet to accelerate sexual maturation prior to release. Here, we examine how male irradiation, methoprene treatment and protein intake affect remating behavior and the amount of sperm stored in inseminated females. In field cage experiments, we found that irradiated laboratory males were equally able to modulate female remating behavior as fertile wild males. However, females mated with 6-day-old, methoprene-treated males remated more and sooner than females mated with naturally matured males, either sterile or wild. Protein intake by males was not sufficient to overcome reduced ability of methoprene-treated males to induce refractory periods in females as lengthy as those induced by wild and naturally matured males. The amount of sperm stored by females was not affected by male irradiation, methoprene treatment or protein intake. This finding revealed that factors in addition to sperm volume intervene in regulating female receptivity after copulation. Implications for SIT are discussed.

The UK glasshouses in which the western flower thrips Frankliniella occidentalis (Pergande) is prevalent offer protection from adverse winter conditions. As such, F. occidentalis may not have been exposed to selection for cold tolerance that would allow successful overwintering in the field. In this study, the cold tolerance of larval and adult F. occidentalis has been assessed in the laboratory. Both age groups show pre-freeze mortality in chronic and acute cold exposures though adults are more cold hardy. Larvae and adults are both able to increase their cold tolerance in response to a combination of lower temperatures and decreased photoperiod. Field experimentation confirmed that F. occidentalis is unlikely to survive for the duration of a harsh UK winter, but a level of cold tolerance that would be adequate for survival in mild winters or for short exposures at sub-zero temperatures was observed.

The landing preferences of fed males of Glossina morsitans morsitans Westwood and Stomoxys calcitrans (L.) were measured under constant conditions in a two-choice situation. Pairs of black-and-white landing targets were presented on the grey walls of an arena ca 60 cm in diameter. In a simple choice of blackness vs whiteness, G. m. morsitans showed a ninefold greater preference for black; S. calcitrans displayed no preference. G. m. morsitans landed twice as frequently on a 15×30-cm vertical black stripe as on a horizontal one, but S. calcitrans preferred the horizontal one. Comparisons between a vertical stripe (or a horizontal one) and similar stripes sloping at various angles indicated that at about 50° G. m. morsitans distinguished the sloping stripe from the vertical (or the horizontal), but did not well distinguish slopes closer to the vertical (or horizontal). Tests with multiple vertical stripe patterns indicated that G. m. morsitans did not significantly distinguish between a single 15-cm stripe and two- or three-striped targets of the same total black area, but landed significantly less frequently on targets of four or five stripes, implying an angular, behavioural visual ‘resolution' of roughly 17°; S. calcitrans responded similarly. Both species showed a marked preference for landing near the edge of the black on all targets, with G. m. morsitans strongly biassed to the black side of an interface.

A total of 18 873 mosquitoes comprising 18 species in 4 genera was collected during a series of 12 monthly all-night collections on bovid baits near the village of Sattoki, Punjab Province, Pakistan. Anopheles pulcherrimus Theo. and usually An. Culicifacies Giles and An. Stephensi List. had unimodal biting rhythms. Mansonia uniformis (Theo.), An. Annularis Wulp and An. Nigerrimus Giles had essentially unimodal rhythms, with most feeding occurring early in the evening but with occasional very slight morning increases.Aedes caspius (Pall.), Culex pseudovishnui Colless, C. tritaeniorhynchus Giles and usually An. Subpictus Grassi had distinctly bimodal biting rhythms, with well-defined early evening and predawn peaks. An. culicifacies, An. Stephensi and An. Subpictus occasionally had multimodal rhythms or were arhythmic. Some species exhibited more than one type of biting curve. In species having a distinct bimodal curve, the amplitude of the predawn or dawn increase varied considerably from month to month. The anophelines, especially An. culicifacies, An. Stephensi and An. Subpictus, exhibited a marked seasonal shift in feeding times, with most biting occurring at dusk during the cold period and late at night during the warm period. However, all components of the biting curves for these species were maintained at varying magnitude throughout the year, perhaps suggesting seasonal variations in the relative frequency of more than one behavioural genome. The remaining species exhibited little or no seasonal change in biting rhythms

Earlier investigations of the effects of extreme temperatures on different stages of Aëdes aegypti (L.) were supplemented by studies of eggs, larvae and pupae in water, and of eggs and adult females in air at various relative humidities.

Larvae of the same stage, young pupae (defined as those less than half-an-hour old) and old pupae (at least 36 hours old), in groups of 100, 25 and 25, respectively, were kept for various periods at low temperatures in incubators, or, at high temperatures in glass cylinders closed at their lower ends by cloth filters and inserted into water baths, and then transferred to water at 28°C. and the mortality determined from the numbers surviving 24 hr. later (in the case of larvae) or becoming adult (in the case of pupae). Eggs in batches of 1,000 were similarly treated, except that periods of 24 hr. in water at 28°C. with yeast as food added were alternated with 24-hr. periods of drying, and mortality determined on the number that hatched and survived to the third or fourth stage. Adult females (four days old) were exposed in groups of 50 for various periods in jars over appropriate solutions giving a complete range of relative humidities and kept at low, medium and high temperatures. Eggs in batches of 1,000 were subjected to the same treatments. The adults were kept at 28°C. and 60 per cent. R.H. before treatment and for 24 hr. afterwards and mortality then determined. Mortality of eggs was determined after alternate 24-hr. periods of wetting and drying at 28°C., as in the case of eggs treated in water. The results of all the experiments were expressed as the exposure-times required to give 50 per cent. mortality (T50), calculated from the observed data.

The responses of Culex quinquefasciatus Say to traps baited with carbon dioxide, 1-octen-3-ol, acetone, butyric acid and human foot odour were studied in the field in Muheza, north-east Tanzania using Counterflow Geometry (CFG) and Centers for Disease Control (CDC) traps. It was found that significantly more C. quinquefasciatusresponded to foot odour collected on nylon stockings than to clean nylon stockings (P < 0.05). Significantly more mosquitoes were caught in a CFG trap baited with carbon dioxide than in traps with either human foot odour, acetone or butyric acid. It was also found that in an outdoor situation a carbon dioxide baited CDC unlit trap collected over 12 times more C. quinquefasciatus than an unbaited CDC unlit trap and nine times more mosquitoes than CDC traps baited with 1-octen-3-ol alone (P < 0.05). The number of mosquitoes caught in a CDC trap baited with 1-octen-3-ol did not differ significantly from that of the unbaited CDC trap (P > 0.05). These results indicate that the Afrotropical C. quinquefasciatusrespond significantly better to traps baited with carbon dioxide than to either octenol, acetone or butyric acid, and that human foot odour contains stimuli to which C. quinquefasciatus is attracted under field conditions.

This paper is a study of the southeast Asian forms of the Anopheles hyrcanus complex with special reference to those of the Malay Peninsula, and it is to the latter forms that the detailed descriptions apply. The group is distinguished from all but a few other species by the presence in the adult female of a tuft of scales on the clypeus on each side, together with pale bands on the palps and a ventral tuft of scales on the seventh abdominal segment. For a complete diagnosis see page 6.

The usual practice has been to recognise only two oriental forms of hyrcanus: varieties sinensis and nigerrimus. It is shown that these varieties as recognised up till now are heterogeneous, and that at least in southeast Asia, ‘hyrcanus’, is a group of sibling species of which there are no less than seven or eight in the Malay Peninsula. For convenience, and where the exact species is not known, the name ‘hyrcanus’ in inverted commas is used, meaning hyrcanus sibling species group.

There is no doubt that these sympatric forms are distinct species for although individual characters, such as the width of the pale bands on the hind tarsi, are variable and the range of variation between two or more species may overlap, by using a combination of characters there is no difficulty in identifying individual adult specimens of either sex. Furthermore, offspring reared from eggs are always of the same form as the female parent. Larvae, pupae, and eggs can usually be identified, and keys are given for the identification of these stages as well as the adults.

Seven named species are described, but only one of these, A. crawfordi, is regarded as new, the others have all been described at various times, and the names later sunk as synonyms of sinensis and nigerrimus.

All seven species have been recognised also outside the Malay Peninsula, and some have a wide range from western India to the Philippines or Moluccas. Except for sinensis, the species belong to southeast Asia, where Assam, Burma, Siam, the Malay Peninsula and Sumatra support the largest number. A. sinensis also occurs in these countries, but the centre of its range is more to the northeast towards China and it does not appear to have penetrated further into the archipelago than the Malay Peninsula and Sumatra. Towards the limits of the Oriental region in northwest India and central and northern China, the southeast Asian species of hyrcanus are few or absent, and are replaced by other forms of hyrcanus of palaearctic type. In China, the name sinensis probably covers two overlapping forms, a southerly oriental one presumed to be Wiedemann's type form which lays a wide decked egg, and a northerly palaearctic form laying a narrow decked egg.

Species of which sufficient numbers have been seen from different countries show geographical variation. The effects of this variation are most marked in the relatively isolated Philippine Islands, where out of three forms occurring there, one, pseudosinensis, is regarded as a species peculiar to the Philippines, though clearly derived from the same stock as the widespread nigerrimus which does not occur there. A second, lesteri, is probably a subspecies of the form of lesteri found in Borneo and the Malay Peninsula. The group thus seems to conform to the classical pattern of speciation by geographical isolation. Much of the evolution and distribution of the species probably took place in pleistocene times.

Broadly speaking A. ‘hyrcanus’ can be described as a swamp breeder, with a preference for animal blood. But it is evident that the individual species show important differences in their biology. Some breed in sunlit waters and their larvae are often green; others seem to prefer shaded places, though not in jungle, and their larvae are usually dark coloured. A. sinensis and lesteri at least, can breed in moderately saline waters, sometimes in company with A. sundaicus and baezai.

It appears that most of the species will bite man freely out of doors shortly after dark, but are reluctant to enter rooms in search of human blood. However, the degree of reluctance to bite man probably varies to an important extent between different species. All species can usually be captured at night at cattle sheds. The adults do not often rest indoors by day, and the outdoor resting places of indiensis and lesteri are described.

In southeast Asia, though ‘ hyrcanus ’ is not one of the principal mosquito vectors of malaria or filariasis, it has been found infected on a number of occasions. In most cases the exact species cannot be determined now, but where this is possible, it has been A. nigerrimus Giles in every instance. Venhuis (1939) showed that his A. hyrcanus var. X (=nigerrimus) was a vector of malaria in Celebes and Java, and Kariadi (1941) implicated it in the transmission of malayan filariasis in southeast Borneo. In Malaya, examination of preserved specimens showed that nigerrimus was the principal or only vector during an outbreak of malaria at Kuala Lumpur which Hodgkin (1933) had shown to be due to hyrcanus, and recently nigerrimus has been found to play a part in the transmission of malayan filariasis in Kedah and Province Wellesley. Experimental infections with Wuchereria malayi, the worm which causes malayan filariasis, showed that nigerrimus was less readily infected than the principal vectors (Mansonia spp.), and some other members of the hyrcanus group, but that it bit the human carrier more readily than the latter. A. sinensis, though probably harmless in Malaya, is a vector of malaria and bancroftian filariasis in parts of China, but the exact identification of the vector is now in doubt, since there appear to be at least two forms in China included under the name sinensis.

The agricultural importance of the Collembola has in the past usually been regarded with some scepticism by economic entomologists. Recently, however, the activities of certain species, particularly those belonging to the genera Bourletiella and Smynthurus, have resulted in an increasing amount of publicity for this order of primitive insects. The subject of the present investigation is Smynthurus viridis, Linn., which, from its jumping habits and the depredations it causes to lucerne (alfalfa), has come to be known commonly as the “Lucerne Flea,” although the damage it causes to clovers is equally serious.

Published laboratory measurements of the levels of fat and haematin in Glossina following a blood-meal were used to develop a prediction of the relationship between fat and haematin during the course of the feeding cycle. The fat-haematin relationship appears to be nearly linear over the later part of the feeding cycle. Data from three field studies onG. morsitans Westw.,G. swynnertoni Aust. and G. fuscipes Newst. were analysed in the way suggested by the prediction, and the observed rates of fat depletion were used to estimate flight activity of male flies towards the end of each feeding cycle. Results for G. palpalis (R.–D.) and G. tachinoides Westw., obtained in other studies with new electric sampling devices as well as by men with hand nets, illustrated particularly clearly the fat-haematin relationship over the whole of the feeding cycle. This was made possible by the electric traps catching more flies nearer to the start of their feeding cycle than the men with hand nets. A comparison between the different areas suggested that the fat level may trigger the onset of feeding behaviour inGlossina.

Perfusion of the isolated heart of Periplaneta americana with caffeine, digitalin, acetylcholine, nicotine and lobeline shows that the pacemaker of this heart is different from the “ myogenic centre ” of the vertebrate heart.

The action of strychnine, morphine and apomorphine on this heart preparation affords evidence of the existence of a neurogenic pacemaker.

This pacemaker is stimulated by suitable concentrations of acetylcholine, nicotine, lobeline and pilocarpine, while it is inhibited by atropine. Acetylcholine and tetraethyl pyrophosphate show a synergistic action. Atropine and tetraethyl pyrophosphate, like acetylcholine and curare, show an antagonistic action. These results prove that the neurogenic pacemaker possesses cholinergic properties.

Adrenaline stimulates the insect heart and ergotamine inhibits it, thus suggesting that the insect heart probably also has adrenergic properties.

On the basis of the present work and the results obtained by other investigators, a theory is put forward that the heart mechanism of most arthropods consists of a neurogenic pacemaker with adrenergic properties, controlled by a cholinergic accelerating nerve. This mechanism bears some resemblance to the sympathetic nerve system of vertebrates.

Rotenone strongly counteracts the action of acetylcholine, tetraethyl pyrophosphate, nicotine, lobeline, pilocarpine and digitalin on the insect heart. Its point of action, however, remains obscure at the moment.

The opposing action of rotenone and tetraethyl pyrophosphate is an indication that a combination of these insecticides for pest control is not to be recommended.

Similarities and differences in foraging behaviour between first and third instar Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae) on Vigna radiata (L.) R. Wilczek (Fabaceae) (mung bean) were determined by frequent, repeated observation of insects on whole plants. The time apportioned to feeding, resting and searching by these two larval instars differed. Third instars were often found feeding on exposed areas of the plant and, if in the terminal parts, would leave these areas more frequently than first instars. Third instars fed at fewer sites and spent less time searching and resting, fed in longer bouts and spent 20% more time feeding than first instars. Although both instars tended to move upwards to the top of the plant, this applied to approximately half of the third instars observed compared to all of the first instars. First instars were found to have a higher relative growth rate than third instars. The results show that it cannot be assumed that first instars are just smaller versions of late instars.

The biochemical properties of the digestive alpha-amylase from Tecia solanivora larvae, an important and invasive insect pest of potato (Solanum tuberosum), were studied. This insect has three major digestive α-amylases with isoelectric points 5.30, 5.70 and 5.98, respectively, which were separated using native and isoelectric focusing gels. The alpha-amylase activity has an optimum pH between 7.0 and 10.0 with a peak at pH 9.0. The enzymes are stable when heated to 50°C and were inhibited by proteinaceous inhibitors from Phaseolus coccineus (70% inhibition) and P. vulgaris cv. Radical (87% inhibition) at pH 6.0. The inhibitors present in an amaranth hybrid inhibited 80% of the activity at pH 9.0. The results show that the alpha-amylase inhibitor from amaranth seeds may be a better candidate to make genetically-modified potatoes resistant to this insect than inhibitors from common bean seeds.

Rapid, precise and timely identification of invasive pest insects such as aphids is important and a challenge worldwide due to their complex life cycles, parthenogenetic reproduction, sex and colour morphs. In this respect, DNA barcoding employing a 658 bp fragment of 5′ region of the mitochondrial cytochrome oxidase I (CO-I) gene is an effective tool in addressing the above. In the present study, we employed CO-I for discriminating 142 individuals representing 32 species of aphids from India. Sequence analyses revealed that the intraspecific and interspecific distances ranged from zero to 3.8% and 2.31 to 18.9%, respectively. In addition, the study also showed for the first time the prevalence of three cryptic species, namely Brevicoryne brassicae (Linnaeus), Hyperomyzus carduellinus (Theobald) and Brachycaudus helichrysi (Kaltenbach) from India. Our work has clearly demonstrated that DNA barcoding is an efficient and accurate method for identification of aphid species (including cryptic species), an approach that potentially could play an important role in formulating viable pest management strategies, more especially biocontrol.

A prerequisite to studying the specific interactions involved in the persistent transmission of luteoviruses such as the potato leafroll virus (PLRV) is the characterization of both the virus and its vectors. A range of techniques was used to assess genetic differentiation among 27 clones belonging to the Myzus persicae complex (M. persicae (Sulzer), M. antirrhinii (Macchiati) and M. nicotianaeBlackman) and showing different efficiencies in transmitting PLRV isolates. All M. persicae/M. nicotianae clones belonged to one of two karyotypes, both 2n = 12, either normal or carrying an autosomal translocation (A1,3), and all M. antirrhinii clones had 13 or 14 chromosomes. Amplified esterase 4 genes were detected by PCR–REN assay in M. persicae/M. nicotianae taxa, with gene expression being modified by methylation. Similarly, amplified E4 genes were revealed in M. antirrhinii but they all showed unmethylated. Two allozyme and 11 microsatellite loci discriminated 10 different genotypic classes among the 27 clones. Analysis of genetic relatedness between these genotypic classes revealed that M. nicotianae clones were very closely related to M. persicaeclones, whereas the genetic differentiation between M. antirrhinii and M. persicae was greater. The implications of these results for the taxonomic status of these genotypes within the complex, and the transmission of PLRV, are discussed.

Using regression analysis the early season dynamics of Helicoverpa punctigera (Wallengren) were determined from long series of light trap catches (10–19 years) from three sites in Australia (Narrabri and Trangie in New South Wales, and Turretfield in South Australia). The size of the second spring generation (G2, the one causing major pest problems in summer cropping regions) was strongly related to the size of the first spring generation (G1). In most cases, rainfall in early winter had a positive influence on the size of G2, whereas rainfall in spring had a negative effect. Regressions were found to account for 49 to 93% of the annual variation in G2, depending on site. The use of light trap catches and weather data to forecast pest levels from a few months to a few weeks in advance is discussed, along with the improved understanding of early season H. punctigera dynamics.

Areas in Argentina, Bolivia, Brazil and Paraguay were searched for the cassava mealybug, Phenacoccus manihoti Matile-Ferrero. The mealybug was located in the Paraguay River basin in the Santa Cruz de la Sierra area of eastern Bolivia, the Mato Grosso do Sul state in South-Western Brazil and in Paraguay east of the Paraguay River. Mealybug populations were extremely low in all areas but there was a period of increase from August to December. Eighteen species of natural enemies were found attacking P. manihoti: the most abundant and also most important were a solitary, internal parasitoid, Epidinocarsis lopezi (DeSantis) (Hymenoptera: Encyrtidae), Hyperaspis notata Mulsant and Diomus spp. (Coleoptera: Coccinellidae), and Ocyptamus spp. (Diptera: Syrphidae). Collections of a closely related mealybug, Phenacoccus herreni Cox & Williams yielded two additional encyrtid parasitoids, Epidinocarsis diversicornis (Howard) and Aenasius sp. nr vexans Kerrich, but they did not survive on P. manihoti. Four parasitoids (E. lopezi, E. diversicornis, Parapyrus manihoti Noyes and Allotropa sp.) and four predators (H. notata, Diomus sp., Sympherobius maculipennis Kimmins, and Exochomus sp.) were sent for quarantine. With the exception of Parapyrus manihoti, all mentioned natural enemy species were forwarded to the International Institute of Tropical Agriculture at Ibadan, Nigeria for mass rearing and subsequent release.