Nightly light-trap catches of insects, covering periods of 2–5 years, from two sites in Africa within 10° of the equator are examined in relation to the regular changes in night illumination of the lunar cycle. For several species average log catches at different phases of the moon are almost linearly related to (log) night illumination, catches of some species, such as Isoptera and Bostrychidae, increasing and of others, such as Marasmia trapezalis(Gn.) (Pyralidae), Lampyridae and Dorylus spp. (Formicidae), decreasing with moonlight. Relative catches of M. trapezalis and Bostrychidae varied by a factor of 30:1 between no moon and full moon. Analysis of whole-night catches gives some evidence on the pattern of insect activity through the night, identifying Syntomis monothyris (Hmps.) (Ctenuchidae) and Stemorrhages sericea (Dru.) (Pyralidae) in particular as early morning fliers. Evidence on how night illumination affects catch, and on the times of night when illumination has most effect, is consistent for the two sites and for different years. However, any adjustment of nightly catches to those expected under standard conditions of illumination can only be approximate. Although most of the differences between catches at different moon phases are accounted for by night illumination, many factors influence catch on an individual night, and moonlight is a major factor only for certain species. A hypothesis about how a light-trap may affect insect behaviour allows changes in catch of some species over the lunar cycle to be explained by the influence of background illumination on trap effectiveness.

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.

The efficiency of miniature CDC light-traps in catching West African malaria vectors was evaluated during two rainy seasons in a village near Ouagadougou, Burkina Faso. Traps were employed both indoors and outdoors using human baits protected by an insecticide-free mosquito-net and different sources of light. Indoors, light from incandescent bulbs increased the catch of Anopheles gambiae s.l. (mainly A. arabiensis Patton and the Mopti chromosomal form of A. gambiae s.s. Giles) and A. funestus Giles c. 2.5 times as compared to traps whose light bulb was removed. Conversely, the difference was not significant when a UV ‘Blacklight-blue’ fluorescent tube was compared to the incandescent bulb. Protecting the bait with a mosquito-net increased the catch c. 3 times for A. gambiae s.l. and c. 3.5 times for A. funestus. A prototype model of double bednet gave intermediate yields. Outdoors, the addition of incandescent bulbs to unlighted traps did not significantly increase the number of vectors caught, but the addition of the mosquito-net to the unprotected human bait did so by c. 1.5–4 times. Thus, the CDC light-trap hung close to a human sleeping under a bednet and fitted with an incandescent bulb, was considered the most practical and efficient in terms of numbers of vectors caught, consequently its indoor efficiency was compared to human landing catches on single collectors and estimated to be 1.08 times and density-independent. Outdoor light-trap catches were either not significantly correlated to biting collections (as for A. gambiae s.l.), or density-dependent in their efficiency (as for A. funestus); thus, they were not considered a reliable means for estimating malaria vector outdoor biting densities in this area. No difference was found in the parous rate of A. gambiae s.l. samples obtained with CDC light-traps and human landing collections.

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.

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.

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.

Flies attracted to odours from 500 to 11 500 kg of livestock were captured using electrified netting in the Zambesi Valley, Rhodesia. Catches of maleGlossina morsitansWestw., Tabanidae, Stomoxyinae and non-biting muscids reached maximum levels at odour concentrations produced by only 500–3500 kg of livestock, but catches of femaleG. morsitans and both sexes of G. pallidipes Aust. increased over the whole range of concentrations tested. With the maximum dose of odour, up to 7100 tsetse were caught in 3 h. The proportion of tenerals in catches of Glossina was not affected by odour concentration. Daily catches of Giossina were positively correlated with daily maximum temperatures. The maintenance of large catches of flies for 60 days and the indication that larger catches are possible suggest the feasibility of employing odour-baited traps for tsetse control.

This review identifies key ways in which manipulations of the crop environment based on detailed understanding of tritrophic interactions can contribute to improvements in the control of insect pests. Such approaches are likely to be of particular benefit against those pests, notably certain species of Lepidoptera and aphid, which are difficult to control with insecticides because of insecticide resistance or suppression of natural enemies. Particular attention is given to the compatibility (or otherwise) of partial plant resistance and biological control, citing examples which support contrasting tritrophic theories. Other areas considered and supported with examples include the use or effects of allelochemicals, refugia, intercropping, crop backgrounds, fertilization regimes, parasitoid conditioning (by host plants) and transgenic crops. Examples of manipulations involving use of selective insecticides which show compatibility with biological methods are also included owing to their possible suitability in integrated crop management programmes.

The development period from birth to adult of alate and apterous virginoparae of the green peach aphid, Myzus persicae (Sulzer), reared on Brassica campestrisssp. chinensis, was measured at 13 constant and five natural temperature regimes. The day–degree model, the logistic equation, and the Wang model were used to describe the relationships between temperature and development rate at constant conditions. The constant temperature–development curves derived from the three models were used with a Weibull function describing the distribution of development times, to simulate the development of individuals of cohorts reared at natural temperature regimes. Comparison of the observed with simulated distributions of adult emergence indicates that all three models can simulate the development of M. persicaevery well when the temperature does not go below 4°C, the notional low temperature threshold of the day–degree model. When accumulation of temperatures below 4°C becomes substantial, only the logistic curve with a low temperature threshold of 0°C can offer accurate simulations; the other two models give falsely longer durations of development. Methods for accurately simulating the development of M. persicae in the field are suggested. The significance of modelling insect development at low temperatures by nonlinear models is discussed.

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.

Predation on parasitized hosts can significantly affect natural enemy communities, and such intraguild predation may indirectly affect control of herbivore populations. However, the methodological challenges for studying these often complex trophic interactions are formidable. Here, we evaluate a DNA-based approach to track parasitism and predation on parasitized hosts in model herbivore-parasitoid-predator systems. Using singleplex polymerase chain reaction (SP-PCR) to target mtDNA of the parasitoid only, and multiplex PCR (MP-PCR) to additionally target host DNA as an internal amplification control, we found that detection of DNA from the parasitoid, Lysiphlebus testaceipes, in its aphid host, Aphis fabae, was possible as early as 5 min. post parasitism. Up to 24 h post parasitism SP-PCR proved to be more sensitive than MP-PCR in amplifying parasitoid DNA. In the carabid beetles Demetrias atricapillus and Erigone sp. spiders, fed with aphids containing five-day-old parasitoids, parasitoid and aphid DNA were equally detectable in both predator groups. However, when hosts containing two-day-old parasitoids were fed to the predators, detection of parasitoid prey was possible only at 0 h (immediately after consumption) and up to 8 h post consumption in carabids and spiders, respectively. Over longer periods of time, post-feeding prey detection success was significantly higher in spiders than in carabid beetles. MP-PCR, in which parasitoid and aphid DNA were simultaneously amplified, proved to be less sensitive at amplifying prey DNA than SP-PCR. In conclusion, our study demonstrates that PCR-based parasitoid and prey detection offers an exciting approach to further our understanding of host-parasitoid-predator interactions.

The effect of ground cover upon the communities of beneficial arthropods established in the canopy of lemon trees was investigated, by comparing three ground-cover management treatments applied: RV, resident vegetation; S, sowed selected species; and BS, bare soil by controlling weeds with herbicide. Over two consecutive years, arthropod communities in the tree canopy were sampled periodically by beating and suction techniques. Significantly higher numbers of beneficial arthropods were found in the RV and S treatments in comparison with bare soil. Spiders and parasitoid wasps were the two most common groups, representing, respectively, 70% and 19% of all catches in beating samples and 33% and 53% in suction samples. For the RV and S treatments, significant seasonal deviations from the bare soil treatment were observed using principal response curves. Similar seasonal patterns were observed over the two years. The RV and S treatments showed significant positive deviations from the BS treatment in late spring and summer, accounted for the higher numbers of parasitoid wasps, coccinelids and lacewings present. By contrast, the seasonal deviations observed for the spider community differed from those of the remaining arthropods. During late winter and early spring, the RV and S treatments presented a higher abundance of spiders in the tree canopy, in comparison with bare soil, whereas in the summer significantly more spiders were found in the bare soil treatment. Spider movements between tree canopy and ground vegetation layers may justify this result.

The use of chromosome translocations for the control of pests, with particular reference to Glossina, is proposed. A translocation arises if two non-homologous chromosomes in the same cell undergo breakage and the fragments re-join with the wrong partners. At meiosis in an individual heterozygous for a translocation, gamete nuclei with several different combinations of chromosomes are produced. Some of these are diploid for one part and lack completely another part of the normal chromosome set; when such unbalanced gametes fertilise normal gametes inviable embryos are produced. It has been found in a number of organisms that about half the gametes of translocation heterozygotes are of the unbalanced type and such heterozygotes are described as semi-sterile. If an individual inherits the same translocation from both parents it is described as a translocation homozygote; this is often inviable but, if not, its fertility is usually normal.

Adult males of G. austeni Newst. have been irradiated and each of their progeny are being screened for the occurrence of semi-sterility. Any individuals found to be semi-sterile would probably be translocation heterozygotes and their progeny will be inbred to try to produce a viable stock, homozygous for a translocation. If this can be done, large numbers of such translocation homozygotes could be reared and released into a wild population, where matings with wild types would produce heterozygotes, and hence a reduction in the fertility of the population.

Using simple assumptions, the effects of releasing translocation homozygotes were computed. Provided the numbers released were such that the translocation frequency approached the optimum value of 50 per cent., the reduction in population fertility would be prolonged for many generations after the releases had finished. It is shown that it would be more efficient to release the translocation homozygotes at successive generations rather than all at once and that the homozygotes released could with advantage be of both sexes. For this reason, and because of the prolonged effect of releases of translocations, it is concluded that the number of individuals that would have to be reared to achieve a given result by the translocation method might be considerably less than if the sterile-male method was used. However, the reduction in population fertility at each generation that can be achieved with the translocation method is limited, and the method would therefore be ineffective against populations whose size was strongly buffered by density-dependent factors.

Several methods, including the use of serology, are available for evaluating prey-predator relationships. Two basic methods involving precipitation and agglutination reactions have been utilised, both of which depend on the production of specific antisera with high titres. A critical account is presented of methods of preparing antisera, with particular reference to the amount of antigen required, the route of inoculation and testing antisera, together with a review of the five precipitation and two agglutination techniques available. The main limitations of serological methods are tje specificity of the arrtisera and the difficulties in quantifying results unless assumptions are made as to the number of prey eaten at each feed. Details of studies employing serological techniques to identify the predators of specific prey and the food od invertebrates are given intwo tables. The value of serological techniques is discussed in relation to the ecology of invertebrates by considering, as examples, te insect fauna on broon (Sarothamnus scoparius), predation of mosquitoes and the food of triclads. Errors in the quantification of predation may occur by including positive reactions resulting from carrion feeding or material ingested acidentally on plants by phytophagous arthropods.

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.

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.

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.

Virgin females of Lobesia botrana Denis & Schiffermüller were mated at ages of 1, 3, 5, 8, 12 and 16 days and the effect of mating delay on reproductive output assessed. Delayed mating did not affect female mating success but fertilization was reduced in 16-day-old females. Increased mating delays substantially affected daily oviposition pattern and resulted in a significant reduction of both fecundity and fertility, so that mean number of viable eggs laid decreased from 150 to 22 in 1- and 16-day-old mated females, respectively. Heavier females were more constrained than lighter ones by mating delays and female reproductive efficiency (no. viable eggs/female body weight) was also significantly reduced. Female longevity significantly increased and oviposition period gradually declined with mating delay. The number of viable eggs was positively correlated with both female weight and oviposition period; female longevity and female weight were also significantly correlated. However, the significance of these correlations declined with increased mating delay. Results overall indicated that mating delay drastically reduces female L. botrana reproductive output. The implications of delayed mating of females are discussed from an ecological perspective in relation to L. botrana control using mating disruption.

Bemisia tabaci (Gennadius) populations, collected from cassava and other plants in major cassava-cultivation areas of Sub-saharan Africa and from elsewhere around the world, were studied to determine their biotype status and genetic variation. Random amplified polymorphic DNA–polymerase chain reaction (RAPD–PCR) markers were used to examine the genetic structure of the populations. The dendogram obtained using the neighbour joining method (NJ) split the cassava-associated populations from the non-cassava types with a 100% bootstrap probability. Analysis of molecular variance (AMOVA) of the RAPD fragments revealed that 63.2% of the total variation was attributable to differences among populations, while the differences among groups (host) and within populations accounted for 27.1 and 9.8% respectively. Analysis of the internally transcribed spacer region I (ITS 1) of the ribosomal DNA confirmed that the cassava populations of B. tabaci populations were distinct from non-cassava populations. Experiments to establish whitefly populations on various host plants revealed that cassava-associated populations were restricted to cassava only, whereas B. tabaci from other hosts were polyphagous but did not colonize cassava. Hence, populations of B. tabaci from cassava in Africa represent a distinct group.

The effects of vegetative cover and soil type on the abundance and distribution of 50 species of scarabaeine dung beetle were examined during three successive days in January 1979 in Hluhluwe Game Reserve, South Africa. Pitfall traps baited with bovine dung were set at intervals of 20 m in a transect across a 20–ha patch of grassveld surrounded by Acacia bushveld. One end of the transect was on clay–loam soil and the other on sandy loam. In all, 32 936 specimens were caught, representing 71 species from 22 genera. Thirty–two species were diurnal and 18 were crepuscular or nocturnal. Twenty–six species were more abundant in bushveld than in grassveld, and eight species were more abundant in grassveld than in bushveld. Soil type influenced the relative abundance of 23 species. The degree of habitat specificity varied widely between species. During overcast weather, both bushveld and grassveld species became abundant in the transitional zone between bushveld and grassveld where the light intensity was similar to that in bushveld on a clear day. It is suggested that light intensity is one characteristic by which beetles recognise bushveld and grassveld.