The continual recruitment of new individuals makes it difficult to study both the survival of multivoltine mosquitoes, and the size of the infectious reservoir in narural populations of malaria vectors. During long-term surveillance of a population of Anopheles gambiae Giles sensu lato in a Tanzanian village by daily light trapping, a temporary dry spell resulted in the cessation of recruitment for a period of 33 days, and a decline in numbers of A. arabiensis Patton caught from over 2000 to less than 10 in a sentinel house. Traps placed elsewhere in the village indicated similar proportionate declines although numbers caught varied according to location. A survival rate of 83% per day was estimated from the rate of population decline. Survival was unrelated to the size of the mosquitoes. The infectious reservoir (the chance of a mosquito acquiring an infection) was estimated to be 2% per feed. The exploitation of fortuitous events which temporarily eliminate a single stage in the life cycle has general applicability in the study of the bionomics of multivoltine insects.

Samples of larvae of Aedes aegypti (L.) were collected in three principal habitats, domestic, peridomestic and feral, in the Rabai area in eastern Kenya. The samples from the domestic habitat represent the population of the domestic form, A. a. aegypti, and the feral samples from tree holes from Bejumwa Forest represent the feral subspecies, A. a. formosus (Wlk.). The peridomestic samples from steps cut into trunks of coconut palms most probably represent hybrids between the domestic and the feral forms. These samples were brought to the laboratory where they reproduced in high numbers, and crosses were made between the three populations. Adults of the parental populations and those resulting from the crosses were marked with different colours of fluorescent pigments, released in the peridomestic habitat in the Rabai area and subsequently recaptured in biting catches on man in the domestic and peridomestic habitats. The results indicate that domesticity, particularly house-entering behaviour, in A. aegypti is genetically controlled and is a product of the action of several genes. The gene action in terms of house-entering behaviour is additive as can be clearly seen from the recapture data for the various crosses. The percentage entering houses was highest among mosquitoes of the form from inside houses (the domestic A. a. aegypti population (D)) and the percentages decreased progressively through the peridomestic (P) and hybrid forms to the feral population of A. a. formosus (F) in the following manner: D (45·)DP (15 ·5), PD (13·9), P (9·8), DF (5·7), FD (73·), PF (1·5), FP. (0·6) and F (0·6).The recaptures outdoors were in the reverse order, the highest percentage being for F (187·) and the lowest for D (8·5), DP (8·0) and PD (7·7). The data suggest that the larvae from the peridomestic habitat may represent hybrids between the domestic and feral forms

A model for the inheritance of behavioural characters in mosquitoes is presented. On the basis of isolating mechanisms and partial hybridisation, it is concluded that A. a. aegypti and A. a. formosus have developed as geographically isolated allopatric populations. This supports the existing polytypic concept of speciation in A. aegypti. Spatial distribution, non-random mating and the existing series of isolating mechanisms indicate that the domestic type form has been introduced into East Africa, most probably on ships.

For a number of years the western grass-stem sawfly, Cephus cinctus, Norton, has been accounted one of the major insect pests of wheat in Western Canada. Originally a grass-feeder, it began to attack wheat about the beginning of the present century, at first only occasionally and at the edges of fields in Manitoba, later much more commonly and with a very wide distribution throughout the wheat-growing areas of Manitoba, Saskatchewan, and Alberta. While this sawfly was confined to native grasses it was held in check by two principal factors (Criddle, 1922) : shortage of grass stalks suitable for oviposition, and parasites. When, however, it began to attack wheat, both of these restraints were evaded. In the first place the wheat fields provided an abundance of host-plants. In the second place, the natural parasites of the sawfly did not move with it into the grain fields—whether they are unaware of the presence of their host in wheat plants or are unable to attack it in that situation is unknown.

Termite damage is a major problem in tropical forestry especially where exotic tree species are used. Stressed tress are generally the most susceptible to attack. Dry-wood termites (Kalotermitidae) live and feed in dead wood but sometimes attack living parts of mature trees; generally, they are pests only in the humid tropics, causing local but sometimes serious damage. Coptotermes (Rhinotermitidae) causes more widespread and serious damage to mature trees, especially in Malaysia and Australia. The most serious losses (up to 100%), due predominantly to various Macrotermitinae (Termitidae) such as Macrotermes, Odontotermes and Microtermes, occur in young, exotictrees such as Eucalyptus in dry regions in Africa and India. Chemical control of dry-wood termites is not feasible; use of resistant trees is probably the only satisfactory strategy. Control of Coptotermes by various methods has been suggested; but only insecticide injection into nests within affected trunks (Australia) and destruction of nests with explosives prior to planting, followed by destruction of queens in subsequently located nests (Papua New Guinea), are effective and economically viable. Attack on seedings, especially by Macrotermitinae in Africa and India, can be prevented by the increasingly unacceptable persistent cyclodienes used as mound poisons or as a barrier around the roots preventing attack by subterranean species. Controlled-release formulations of otherwise non-persistent insecticides are being development but are expensive and not widely available. Many non-chemical measures have been suggested, but none has been rigorously evaluated; none will provide the almost complete protection afforded by cyclodienes. Biological control shows little promise. Use of resistant tree species and development of resistant varieties offers the only long-term solution, but until these are available there will be a need to continue using cyclodienes or rapidly to develop alternative control methods.

The B and Q ‘biotypes’ of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) have been invading many parts of the world and causing severe damage to a range of crops. Recent phylogenetic analyses indicate that B and Q are cryptic species within the B. tabaci species complex. Although various attempts have been made to examine the reproductive compatibility between B and Q, few studies have tested the fertility of the F1 females and so the extent of possible gene flow remains unclear. In this study, we conducted a series of crossing experiments and behavioural observations to examine in detail the reproductive compatibility between the B and Q biotypes collected from Zhejiang, China, a region recently invaded by these whiteflies. Crossing experiments between the two biotypes using either single-pairs or small groups demonstrated that proportions of females in the F1 progeny were only 0–2% in the inter-biotype crosses compared to 58–68% in the intra-biotype treatments. Furthermore, all inter-biotype F1 females were sterile. Continuous video observations showed that B and Q adults very rarely copulated, and copulation occurred only when adults of opposite sex from different biotypes were enclosed in dense cohorts for a relatively long period of time. These data show that the B and Q biotypes examined in this study are completely isolated in reproduction. The isolation was due to mainly a copulation barrier, but post-copulation barriers were also involved.

Arthropods cope with reduced oxygen and elevated carbon dioxide atmospheres with a reduction in metabolic rate, also called metabolic arrest. The reduction in metabolism lessens the pressure on the organism to initiate anaerobic metabolism, but also leads to a reduction in ATP production. The natural permeability of cellular membranes appears to be important for the survival of the arthropod under low oxygen or high carbon dioxide atmospheres. Despite the similarities in response, arthropod mortality is generally greater in response to high carbon dioxide as apposed to low oxygen atmospheres. There appears to be a greater decrease in ATP and energy charge in arthropods exposed to high carbon dioxide as compared with low oxygen atmospheres, and this may be due to greater membrane permeability under carbon dioxide leading to an inefficient production of ATP. Reduced oxygen and elevated carbon dioxide atmospheres can have an additive effect in some cases, depending on the concentrations used. The effect of these atmospheres on arthropods depends also on temperature, species and life stage. Additional work is needed to fully understand the mode of action of controlled atmospheres on arthropod pests.

Discriminant function and cluster analyses were performed on 19 morphometric variables of the aculeus, wing and mesonotum to determine whether populations of Anastrepha fraterculus (Wiedemann) from different parts of Mexico could be distinguished from populations from South America., Samples were collected from seven localities across Mexico, two from Brazil, and one each from Colombia and Argentina. Results showed there were statistically significant differences between Mexican and South American populations with respect to the aculeus (tip length, length of serrated section, mean number of teeth) and wing (width of S-band and connection between S- and V-bands). The degree of morphological variation observed among Mexican populations was extremely low, and as a consequence, the Mexican populations were identified as a single morphotype by discriminant analysis. The ‘Andean morphotype’ consisting of the Colombian population, and the ‘Brazilian morphotype’ consisting of the two Brazilian populations plus the single Argentinian population were also distinguished. It was concluded that the macro-geographical morphotypes from Mexico, Colombia, and Brazil plus Argentina correspond to three distinct taxonomic entities. Comparisons of results with those obtained from behavioural, karyotypic, isozyme and DNA studies suggest that sufficient evidence now exists to name a new Mexican species from within the A. fraterculus complex. This will be done in a separate publication. A provisional key to the morphotypes of A. fraterculus studied is provided.

Despite the large number of collection rocords available, there has recently been some debate concerning how host-specific ticks are. A quantitative data set is presented for the host preferences of African ticks. The results are based on 43,615 individual collection records from published sources covering most countries in mainland Africa. Out of 223 ticks species, 112 have been collected 20 times or more; 14 of these are generalists and at least 39 are potential specialists. Further collections are needed for greater clarity in many cases. It is important that people working on problems that relate to tick-host interactions are aware of the context in which these occur, lest they make false a prior hypotheses about the importance of hosts or parasites in the system.

Genetic similarities between 13 samples belonging to nine reference biotypes and two field populations of Bemisia tabaci (Gennadius), one field population of B. medinae Gómez-Menor and another of B. afer Priesner &Hosny, were evaluated using amplified fragment length polymorphism (AFLP) markers. The results indicate that B. tabaci biotypes can be grouped together with a minimum similarity coefficient of 0.32 and separated from the two other species with a similarity coefficient of 0.07. Bemisia tabaci biotypes were grouped in four clusters which comprised: (i) Near East and Indian subcontinent biotypes; (ii) B and Q biotypes plus a Nigerian population from cowpea; (iii) New World A biotype; and (iv) S biotype and a Nigerian population from cassava. These results were consistent with a previous grouping of biotypes based on RAPD-PCR analysis. The AFLP assay allowed the scoring of a total of 354 polymorphic bands in two reaction events with the use of two primer combinations.

Plant-mediated interactions between begomoviruses and whiteflies exert important influences on the population dynamics of vectors and the epidemiology of plant diseases. In this article, we synthesize the relevant literature to identify patterns to the interactions. We then review studies on the ecological, biochemical and molecular mechanisms underlying the interactions and finally elaborate on the most interesting issues for future research. The interactions between begomoviruses and the insect vector, the whitefly Bemisia tabaci, via their shared host plants can be mutualistic, neutral or negative. However, in contrast to a pattern of improved performance of vectors on virus-infected plants that has been observed with persistently transmitted RNA viruses, the number of cases exhibiting mutualistic, neutral or negative effects in the indirect interactions between begomoviruses and whiteflies appear evenly distributed. With regard to the mechanisms of plant-mediated positive effects on whiteflies, two case studies indicate that suppression of plant defence and/or alteration in plant nutrition as a result of virus infection can be important. Our review shows that we are only just beginning to understand the tripartite interactions between begomoviruses, whiteflies and plants. Future efforts in this area should try to expand the number and diversity of pathosystems for investigation to reveal the patterns of interactions, to investigate the molecular and biochemical mechanisms of the interactions using a multidisciplinary approach, and to examine the virus–plant–vector interactions in the field and in natural plant communities.

The international trade in live reptiles has grown dramatically in the last decade. Since many of these reptiles are infested with ticks, the number of ticks introduced to new exotic locations has also increased. This is causing concern in importing countries such as the United States because some of the reptilian ticks are known to be vectors of diseases of veterinary and economic importance, such as heartwater. Rational measures to control these tick species and to eradicate new introductions have been slow to develop due in part to the scattered and often obscure sources of available data on the exotic ticks. This review is an attempt to collate information on the geographical distribution, host range, life cycle and associations with diseases for four Amblyomma species, A. marmoreum Koch, A. nuttalli Dönitz, A. sabanerae Stoll and A. sparsum Neumann, and for four Aponommaspecies, A. exornatum (Koch), A. flavomaculatum (Lucas), A. latum(Koch) and A. varanensis (Supino), that have recently been introduced into Florida, USA on imported reptiles.

The results of a series of catches of biting insects at human bait on platforms in the canopy of the forest at Mongiro, Bwamba, Uganda, are reported. The catches were designed to investigate differences in the numbers taken, due to platforms, season and weather, but mainly to study the short-term changes in the activity of biting insects near the time of sunset. Each catch lasted from 3 hours before to 3 hours after sunset, and was divided into 10-minute periods from 30 minutes before to 1 hour after sunset. The main analysis is of catches made on five platforms on each of 100 evenings which covered the end of the dry and beginning and end of the wet season, 1948, and the end of the dry season, 1949.

A list of the species of biting insects encountered is given. Eight species (Anopheles (M.) gambiae, Taeniorhynchus (C.) fuscopennatus, Taeniorhynchus (M.) africanus and uniformis, Aëdes (M.) nigerrimus, Aëdes (S.) apicoargenteus and africanus, and Chrysops centurionis) were found to be abundant and data relating to them has been subject to more or less detailed analysis. The remaining 27 species or groups of species are discussed shortly.

Six of the eight abundant species show statistically significant differences between the catches on the five separate platforms. Arrangement of the five platforms in order of the total numbers taken, for each of these six species, gives results which are practically identical in three species (Anopheles (M.) gambiae, T. (M.) africanus and uniformis) and in two others (Aëdes (S.) apicoargenteus and africanus) ; however, the arrangements in these two species groups differ widely from each other. The arrangement for C. centurionis differs again.

These ordinal arrangements are compared with the obvious characteristics of the platforms and no consistent relationship is found. It is pointed out that the first three species are derived, largely or even entirely, from breeding places outside the forest, in or associated with the adjacent extensive areas of open swamp, while the last three are likely to be completely confined to the forest for breeding ; both the latter two mosquito species breed in tree holes, and dense shade is characteristic of the breeding places of species of Chrysops closely allied to C. centurionis. It is considered most probable that these platform differences in the numbers yielded are due to local differences in the densities of the adult populations which in turn are related to the abundance and proximity of breeding places.

Seasonal variations in the numbers of the abundant species are also studied and are considered to be almost certainly related to the amount and distribution of rainfall affecting the profusion of breeding places at least as far as the mosquito species are concerned. The tree-hole breeding species, however, suffered a reduction in numbers before the end of the wet season, an effect also noted by Mattingly in West Africa.

The amount of the reduction of the numbers of A. (S.) africanus in the dry season is of importance in assessing the possibilities of the survival of yellow fever virus in that mosquito as a host. The estimated reduction in the dry season of 1949 was to less than one twenty-third of the population existing at the end of the previous wet season (November, 1948).

C. centurionis occurred during all the catch series but was extraordinarily abundant in late March and early April, 1948. It is considered probable that this time of increase represents a yearly period into which hatching from the pupa is compressed. This conclusion is supported by the finding that during this period the biting population was composed of two groups one of which tended to bite before, and the other after, sunset.

Evidence is produced to show that the biting activity of Anopheles (M.) gambiae was depressed by wind, that of Aëdes (S.) africanus by wind and rain but that that of C. centurionis was little affected by either of these factors.

Studies of the biting-activity changes in the nine ten-minute periods extending from 30 minutes before to one hour after, sunset are presented. Each of the species which were known to be mainly active by night and which were sufficiently abundant for study, show activity increasing about sunset, rising to a maximum shortly after, and thereafter declining again to moderate levels. This initial peak is very clearly marked in the cases of Anopheles (M.) gambiae, T. (C.) fuscopennatus, T. (M.) africanus, Aedes (S.) africanus and C. centurionis, less so, but still distinct, in T. (M.) uniformis and A. (M.) nigerrimus. Its position differs in different species being earliest in the case of C. centurionis (18.10–18.20 hours) and latest in that of T. (M.) africanus (18.40–18.50 hours). However, in any given species the peak period of biting activity was subject to only slight movement in time in relation to sunset; in analyses of the data by different platforms, by season, and by types of weather it was the exception to find the time of peak activity to be shifted more than one ten-minute period away from the position which it occupied over the whole series. Further, in studies of the curves of biting activity on individual nights, three consecutive ten-minute periods centred on the period which showed the peak over the whole series, included the peak in 21 of the 23 A. (M.) gambiae cases available, in all five of the T. (M.) africanus, in eight of the 11 A. (S.) africanus and in 15 of the 20 C. centurionis, cases. The regularity of the occurrence of the peak period of activity in any given species is considered to indicate that it is largely controlled by changes in light intensity about the time of sunset.

These findings are discussed in relation to the general problem of the mechanism controlling the rhythm of activity in insects biting by night and a hypothesis, which is based on the conception that different population groups may have different biting habits, is advanced to account for the different types of cycle commonly encountered.

Ecological studies were undertaken from 1964 to 1966 on the mosquitoes that occurred in the Poole area of Dorset, southern England. The seasonal incidence was obtained of adults of Aedes cinereus Mg., Ae. punctor (Kby.), Ae. cantans (Mg.), Ae. detritus (Hal.), Culiseta annulata (Schr.), Mansonia richiardii (Fic.) and Anopheles plumbeus Steph. There were marked annual variations in their populations. With the exceptions of Ae. cinereus and Ae. cantans, their diel biting cycles were obtained. In most species maximum biting occurred around sunset and sunrise, with a reduction in biting at night. A comparison was made of the biting times of Ae. detritus and M. richiardii at sunset and sunrise in July and August. By dividing the catch into five-minute intervals peak biting times were related to crep values.

Several new traps were designed and tested against Glossina morsitans morsitans Westwood and G. pallidipes Austen in Zimbabwe. The best of the new traps, the F2, was three times as effective as a beta trap and ten times as effective as a biconical trap for G. pallidipes. A white biconical trap was only half as effective as an F2 trap for females of G. m. morsitans. The catch of males of G. m. morsitans was similar in all traps. The F2 trap was up to ten times as effective as a beta trap for Stomoxyinae. Catches doubled when acetone was released at 0·5 or 5·0 g/h near the traps. Catches from traps made of white cloth declined by 90% as the cloth yellowed with exposure but were restored when the cloth was painted white.

The rate of oviposition of isolated pairs of Tribolium castaneum (Hbst.) on finely divided wheatfeed was measured over the entire adult life at 25°C. and 70 per cent. R.H. It was also measured over a period of seven weeks from the start of oviposition at 30 and 70 per cent. R.H. at 25, 30 and 35°C., respectively, at 70 per cent. R.H. only at 22·5, 27·5, 32·5 and 37·5°C. and at 2 per cent. R.H. at 30°C.

At 25°C. and 70 per cent. R.H. each female laid, on the average, 360 eggs at the rate of 2·5 per day for about one hundred days and then at a decreasing rate for the next hundred days. When this experiment was repeated over a seven-week period, each female laid on average about 3 eggs per day. At 70 per cent. R.H., the optimum temperature for oviposition was about 32·5°C., at which about 11 eggs per day per female were laid over the seven-week period. These rates fell to just over 2 per day at 22·5°C. Only one egg was laid by 15 females at 20°C. At 37·5°C. the rate was about 10 eggs per day initially but it declined to about 3 per day by the end of seven weeks, whereas at lower temperatures the decline in laying was slight. Compared with 70 per cent. R.H., the oviposition rate at 30 per cent. R.H. was almost halved at 25°C., but was only slightly reduced at 35°C. At 30°C. and 2 per cent. R.H., females laid well, averaging over 4 eggs per female per day. The periodic provision of water for drinking at 25°C. and 30 per cent. R.H. depressed oviposition.

The preoviposition period was 2 days at 37·5°C. and increased steadily at lower temperatures to 10 days at 22·5°C. It also varied more between females at low temperatures.

The number of eggs recovered in this work was lower than the number obtained by Park & Frank (1948), who used considerably more food in their oviposition chambers. In this work, some eggs were eaten by the adult beetles. However, the innate capacity for increase of the species calculated on these data is extremely high, and could not be maintained for long because of the cannibalistic habits of this species.

In the coastal region of British East Africa three ant species, Anoplolepis custodiens, A. longipes and Pheidole punctulata may destroy the ant Oecophylla longinoda which is a valuable predator on the coconut pest Theraptus sp. (Coreidae). The three first-named species do not prey on Theraptus, which may severely damage palms occupied by them.

Nesting habits of the three ant species and their behaviour towards O. longinoda and certain other insects are described.

O. longinoda has been exterminated in the limited areas occupied by the two Anoplolepis species. P. punctulata is widespread and is usually common in areas occupied by O. longinoda and is also present, though relatively less common, in A. longipes areas.

The distribution of the Anoplolepis species, particularly A. custodiens, is correlated with sandy soils bearing a sparse ground vegetation. Where there are heavy soils or a thick ground vegetation of grasses and creepers the Anoplolepis species are absent and O. longinoda is usually present. It is suggested that the Anoplolepis species are limited by the relatively low temperature of soils shaded from sunlight by thick vegetation.

A Robinson 125-W mercury-vapour light-trap was operated at an exposed site near Cranfield aerodrome, south-eastern England. The effects of moon-light, temperature and wind speed on light-trap catch were investigated. The dependent variable, In (catch +1), was compared with the independent variables moonlight illuminance, air temperature and wind speed, using multiple regression analysis. An algorithm was developed and used to estimate moonlight illuminance. Increases in mean illuminance and mean wind speed were associated with a decreased light-trap catch. Increases in mean temperature were associated with an increased catch. When the moth catch was broken down into individual families and species, other trends became apparent. Catches of noctuid moths were unaffected by variation in mean illuminance, although they were influenced by variation in mean temperature and mean wind speed. On the other hand, catches of crambine moths were very sensitive to fluctuations in mean illuminance and mean wind speed although unaffected by changes in mean temperature. The multiple regression equations were used to predict future light-trap catches. The correlations between observed and predicted In (catch +1) for (a) all moths, (b) noctuid moths and (c) crambine moths, were very good. It is suggested that the observed moonlight trend for crambine moths is a consequence of changing behaviour as moonlight illuminance changes rather than the alternative of changing light-trap effectiveness.

The autumn migration of Helicoverpa armigera (Hübner) was observed with radar and two types of light-trap at Langfang, Hebei province, China in 2001 and 2002. The sudden increase in the proportion of H. armigera moths in the searchlight trap indicated migration into the area and catches increased 10-fold during the second half of the night due to the landing of migrants before dawn. The moths’ migratory flights took place at up to 2000 m above the ground, and moths flew differentially at times, and heights, when favourable (i.e. northerly) winds occurred. This facilitated the maximum displacement of moths towards the south during these ‘return’ migrations. The moths flew over the radar site at consistently high densities through the night, and the resulting flight durations of c. 10 h, at displacement speeds of 30–33 km h−1, would allow moths emerging in the far northeast of China (i.e. Liaoning and Jilin provinces and the Inner Mongolia autonomous region) to migrate into northern China (Hebei, Shandong and Henan provinces). The association of the seasonal migratory movements of H. armigera with crops in northern China is briefly discussed.

In Zimbabwe, studies were made of the numbers of tsetse (Glossina spp.) and stable flies (Stomoxys spp.) attracted to cattle of different nutritional status, age and sex. Host odours were analysed to determine the physiological basis of these differences and improved methods are described for measuring rates of production of kairomones. Seasonal fluctuations in host weight, related to changes in pasture quality, had no significant effect on attraction of tsetse or Stomoxys. However, both attraction to different individuals and carbon dioxide production by these individuals were strongly correlated with weight, suggesting a possible link. Attraction to the odour from different types of cattle decreased in the order ox > cow > heifer > calf, and oxen were twice as attractive as calves of less than 12 months old. Lactation did not alter the relative attractiveness of cows. Calves less than six months old produced lower levels of carbon dioxide, acetone, octenol and phenols than oxen, but for older calves and cows, levels of production of known kairomones and repellents were similar to those of an ox. Carbon dioxide produced by cattle varied according to time of day and the animal's weight; cattle weighing 500 kg produced carbon dioxide at a mean rate of 2.0 l min−1 in the morning and 2.8 l min−1 in the afternoon compared to respective rates of 1.1 and 1.9 l min−1 for cattle weighing 250 kg. Artificially adjusting the doses of carbon dioxide produced by individual cattle to make them equivalent did not remove significant differences in attractiveness for tsetse but did for Stomoxys. Increasing the dose of carbon dioxide from 1 to 4 l min−1 in a synthetic blend of identified kairomones simulating those produced by a single ox, increased attractiveness to tsetse but not to the level of an ox. The results suggest that the main sources of differences in the attractiveness of individual cattle are likely to be variation in the production of carbon dioxide and, for tsetse, other unidentified kairomone(s). The biological and practical implications of these findings are discussed.