Dactylopius tomentosus is composed of biotypes adapted to different Cylindropuntia species. One biotype is an important biological control agent of C. imbricata in South Africa while another has the potential for the control of C. fulgida var. fulgida. These two weed species occur in sympatry in some areas of South Africa, so the introduction of the second biotype could result in hybridization, which, in turn, could impact on the biological control programs through altered host specificity and fitness of the hybrids. To anticipate what might happen, reciprocal crosses were made between the two biotypes, and the biological performance of the resultant hybrids was compared with that of each parental lineage on C. imbricata and C. f. var. fulgida. The biotypes interbred freely and reciprocally in the laboratory. Comparisons of crawler and adult female traits showed differences in performance that were dependent on the origin of the maternal and paternal genomes. However, when all traits were combined into a ‘fitness index’, both hybrids clearly outperformed the parental lineages. The increase in fitness shown by the hybrids over their maternal lineage was greater on the alternative host of the maternal parent than on the natural host of the maternal parent. Therefore, in areas where the two cacti occur in sympatry, hybridization between the biotypes is not expected to be detrimental to the biological control of either weed.

A portable wooden hut with two windows, on opposite sides, fitted with traps to catch mosquitos as they entered the hut was tried, with human bait, as a sampling device for mixed populations of Anopheles gambiae Giles and A. gambiae var. melas Theo. in and near Keneba village in the West Kiang district of the Gambia.

In eighteen night catches, between 24th August and 22nd September 1954, 5,901 females of this species and its variety were taken in the traps, five high catches (642 to 1,240 females) being made before 3rd September and thirteen low catches (27 to 306 females) between 6th and 22nd September. Possible causes for the different size of catches in the two periods are discussed with the conclusion that the differences in catch are not simply attributable to erratic functioning of the hut as a trap.

Four night catches of 186, 741, 797 and 1,240 females of A. gambiae and its variety are reported in detail. They reveal that mosquitos were taken virtually exclusively in the leeward trap if the wind persisted from one direction. But if the wind was variable, or conditions were calm, they were taken in both traps, entering the traps alternately as the wind shifted in the first instance and, perhaps simultaneously in calm. The results show that the use of only one trap could give misleading information about the numbers of mosquitos available outside the hut.

There is no doubt that, with wind, the mosquitos approached the host in the hut from down-wind. Since much of the catching occurred in darkness it would seem that the mosquitos were attracted by the emanations of the host and that their approach to the hut was not directed by a visual mechanism controlling up-wind flight.

Heavy rain for about seven hours did not prevent flight.

From hourly collections, made from dusk to dawn, a curve of activity for A. gambiae with its variety melas was obtained resembling the biting cycle reported elsewhere by other authors, the greatest activity occurring between midnight and 0600 hr. All the females (except two instances of incomplete fresh blood-meals) were unfed and, in a small sample, ovarian development was stage II or earlier. First entries occurred just before complete darkness in the evening and the last in good light about 30 minutes after sunrise.

No males of A. gambiae or var. melas were taken in the traps.

The numbers, all females, of other species taken were: 1 of A. funestus Giles, 1 of A. rufipes var. ingrami Edw., 59 of Taeniorhynchus (Mansonioides) spp., 30 of Culex nebulosus Theo., 19 of C. thalassius Theo., and 15 of unidentified species. Some Culicoides occurred in the traps and in the hut itself.

The hut, if modified to include a window trap in each of the four walls and a cowl over each window to keep out rain, appears to be a simple and convenient sampling device for certain types of investigations on the biology and behaviour of A. gambiae and its variety melas.

Traditional approaches to studying the effects of genetically modified (GM) crops on beneficial insects involve either field assays, comparing insect population levels between control and GM crops or tritrophic bioassays with contaminated insects – usually larvae or eggs of Lepidoptera – as preys. Here, we report the results of a bioassay using an artificial diet, suitable for predatory Coleoptera, to supply Bacillus thuringiensis (Bt) solubilized Cry1Ab and Cry3Aa as well as trypsin-activated Cry1Ab to Atheta coriaria and Cryptolaemus montrouzieri adults and young larvae of Adalia bipunctata. Water, solubilization buffer and trypsin-treated solubilization buffer were used as controls. In total, 1600 insects were assayed. Assays showed a relatively low mortality rate in the controls, ranging from as low as 7% after 15 days (C. montrouzieri) to about 15–20% after five days (A. bipunctata) or 15 days (A. coriaria). For all three predators, there were no statistical differences between the mortality recorded in any of the treatment groups and the corresponding controls. These results indicate a lack of short- (A. bipunctata) and long-term (A. coriaria and C. montrouzieri) mortality associated with oral ingestion of Cry1Ab and Cry3Aa at the high dose tested (50 μg ml−1). We discuss the relevance of these findings for the ecology of beneficial Coleoptera and compatibility with Bt and GM Bt crops.

The woolly apple aphid Eriosoma lanigerum (Hausmann) is one of the most damaging apple pests in South Africa. Information on its genetic diversity is lacking and this study, in which the genetic structure of parthenogenetic E. lanigerum populations was characterized in the Western Cape Province of South Africa, represents the first local study of its kind. A total of 192 individuals from four different regions were collected and analysed using amplified fragment length polymorphism (AFLP). Using five selective AFLP primer pairs, 250 fragments were scored for analysis. Results indicated that a low level of genetic variation was apparent in E. lanigerum populations in the Western Cape (H = 0.0192). Furthermore, populations collected from geographically distant regions were very closely related, which can partly be explained by the fact that agricultural practices were responsible for dissemination of populations from a common ancestor to geographically distant areas. The low level of variation found indicated that the possibility of controlling E. lanigerum in the Western Cape using host plant resistance is favourable. This is the first report of AFLP being used to characterize the genetic structure of an aphid species. Results indicate that this marker may be useful for analysis of other aphid species.

Approximately 300 000 larvae of Phthorimaea operculella (Zell.) infected with granulosis virus were collected from virus-treated potato crops in Western Australia. Modified crop culture and releases of laboratory-reared adults were used to boost the natural populations. Virus was applied as an aqueous suspension of pulverised diseased larvae. Infested foliage was collected into large polythene bags; the larvae were forced from their mines by heat and collected by washing in water. Collection and extraction took 100 h; field propagation of virus is thus inexpensive. The purification of the virus was carried out by differential centrifugation and separation on sucrose gradients. A total of 35 g of pure freeze-dried material containing approximately 1·35×1015 particles was obtained.

Circadian flight activity in the males and females of Anopheles gambiae Giles species A and B, A. melas (Theo.) and A. merus Dön. has been investigated using the acoustic actograph technique. In each species the pattern and timing of activity in males and females is almost identical. Cyclical activity continues in constant dark; the period of the cycle is approximately half-an-hour shorter in A. gambiae species A and half-an-hour longer in A. merus than in the other two species. In alternating 12 h light: 12 h dark, both sexes are active during the dark period, with peaks of activity following light-off and light-on. After light-off, the species become active in the following order: A. gambiae species A, A. melas, A. gambiae species B, A. merus. A. merus is approximately 20 min later than species A.

The rate of digestion, as reflected in the rate of excretion, on a blood-meal was measured in males of Glossina morsitans Westw. (subsp. orientalis Vanderplank) under identical conditions of temperature and relative humidity but varuing conditions of other factors. The rates of excretion in non-teneral males captured after feeding on bait-oxen in two different habitants were identical and were significantly higher than those of non-teneral field-collected males fed on guineapig in the laboratory. The latter excreated the meal more rapidly than non-teneral males that emerged and were fed on guinea-pig in the labortory. That the variations were not due differences in blood type was shown by feeding teneral laboratory-emerged males on different hosts; the rates of excretion of meals from different mammals did not significantly one from another. Teneral laboratory-emerged flies excreted more rapidly when fed on reptilian or avian blood than when fed on mammalian. The lower rate of excertion in laboratory explanations in terms of a metabolic uncoupliing and pre-feeding behaviour are described.

The principal pest of sugar-cane in northern Tanganyika is the Red Cane Beetle, Cochliotis melolonthoides (Gerst.) (Melolonthidae). Descriptions of adults and larvae of Cochliotis and of allied beetles found in the same area are given.

The bionomics of Cochliotis have been studied in the field over two seasons. The life-cycle is annual with adult swarming in early October and a season of maximum larval damage in July–August.

The intensity of infestation and the nature of the losses are discussed, and the mortality factors which act upon Cochliotis in nature are reviewed.

Cultural control measures suggested include the deferment of planting until July to October, when larval activity has waned; introduction of quick-maturing varieties, mechanically cultivated so that long ratooning can be gradually eliminated; regulation of the water table by control of irrigation, and the trial of resistant varieties. The Mauritius varieties M. 134/32 and M. 165/38 are suggested in this connection.

Biological control is discussed and a review of the parasite species that might possibly be introduced is made largely from the writer's Mauritius work on Clemora smithi (Arr.).

Experiments in the chemical control of Cochliotis are described and the final recommendation is the application at planting of ½ lb. per 50 ft. of furrow of a BHC powder containing 2·5 per cent, of γ BHC. This practice has been adopted by the infested estate with successful results in virgins and first ratoons.

Further work is suggested on the chemical protection of second and later ratoons by surface application of BHC or aldrin.

The estimation of tsetse fly mortality rates from life-table data is central to opulation dynamics studies and to the development of tsetse fly control programmes. For a population at equilibrium with a stable age distribution, the age-specific mortalities may be estimated directly from the number of individuals in each age class, but a correction must be applied when the population is growing or declining. Furthermore, if the mortality rates are changing with time, inaccuracies will be introduced into estimates of the mortality rates derived from the age structure of the population since the population will take time to reach a new stable age distribution. In this paper we use the Euler-Lotka equation, which relates the age-specific mortality and fecundity to the overall growth rate of the population, to study the loss rate of the tsetse fly Glossina pallidipes (Austen) as a function of pupal mortality, adult mortality and mortalities applied to each age class seperately. We then present a simulation model in order to quantity and to set limits on the precision of estimates of mortalities when the mortalities are themselves changing.

Pear psyllids (Hemiptera: Psylloidea: Psyllidae: Cacopsylla spp.) belong to the most serious pests of pear (Pyrus spp.). They damage pear trees by excessive removal of phloem sap, by soiling the fruits with honeydew which, in turn, provides a substrate for sooty mould, and by transmission of Candidatus Phytoplasma spp., the causal agents of the pear decline disease. The morphological similarity, the presence of seasonal dimorphism that affects adult colour, size and wing morphology and uncritical use of species names, led to much confusion in the taxonomy of pear psyllids. As a result, pear psyllids have been frequently misidentified. Many of the entries attributed to Cacopsylla pyricola and other species in the GenBank are misidentifications which led to additional, unnecessary confusion. Here we analysed DNA barcodes of 11 pear psyllid species from eastern Asia, Europe and Iran using four mitochondrial gene fragments (COI 658 bp, COI 403 bp, COI-tRNAleu-COII 580 bp and 16S rDNA 452 bp). The efficiency of identification was notably high and considerable barcoding gaps were observed in all markers. Our results confirm the synonymies of the seasonal forms of Cacopsylla jukyungi ( = C. cinereosignata, winter form) and C. maculatili ( = C. qiuzili, summer form) previously suggested based on morphology. Some previous misidentifications (C. chinensis from China, Japan and Korea = misidentification of C. jukyungi; C. pyricola and C. pyrisuga from East Asia = misidentification of C. jukyungi and C. burckhardti, respectively; C. pyricola from Iran = misidentification of C. bidens, C. pyri and Cacopsylla sp.) are also corrected. There is no evidence for the presence of European pear psyllid species in East Asia.

Studies were made of the susceptibility of wild-caught females of Glossina pallidipes Austen to deposits of DDT, dieldrin and deltamethrin on cotton canvas and Terylene netting. Aqueous suspensions of 3% dieldrin wettable powder, 3% dieldrin emulsifiable concentrate, 5·0% DDT wettable powder and 0·0625% deltamethrin flowable concentrate, were sprayed on the canvas at 0·36% litre/m2 Over 95% of the flies resting for 45 s on fresh deposits of these insecticides died within 72 h. Deposits of dieldrin, DDT and deltamethrin exposed to the sun during 140 days of the dry season produced mortalities of 100, 0 and 10% compared with 100, 75 and 100% for shaded deposits. The concentration of dieldrin and deltamethrin on exposed canvas was about 1% that on shaded canvas, but dieldrin produced photodieldrin upon exposure to the sun. Flies colliding with Terylene netting that had been immersed in 0·75–6·0% suspensions of dieldrin wettable powder and 0·01–0·1% suspensions of deltamethrin flowable concentrate produced mortalities of 100%. Deltamethrin deposits were resistant to weathering by rain, but dieldrin deposits were not. It is suggested that deltamethrin flowable concentrate should be used during the wet season and that dieldrin wettable powder should be used during the dry season. Dieldrin sprayed on an electrocuting target reduced the catch, but deltamethrin did not.

Further analysis of results obtained from a study of populations of Coccinellids on three plots of Vicia faba infested with Aphis fabae Scop, at Rothamsted during 1952 are presented. The distributions of coccinellid egg batches and older larvae (mostly 3rd and 4th instars) on bean stems of five arbitrary classes of aphid infestation, emphasise the differences in the manner of increase of the predator and prey populations considered here; at the same time, the results throw light on the oviposition behaviour of the adult Coccinellids.

The degree of correlation between coccinellid egg batches and Aphids on the plots (as indicated by regression analysis) varied inversely with the size of the aphid populations on the plots. On one plot, where Aphids were extremely numerous, this correlation was negligible; on the two other plots, where Aphids were less abundant, the correlation was more marked, being highest at the plot where the aphid numbers were lowest. The degree of correlation between egg batches and Aphids was determined apparently by the rate of increase of aphid numbers. It is pointed out that while these coccinellid populations increased additively (by immigration of ladybirds to the beans), populations of A. fabae increased multiplicatively (by reproduction) and at much higher rates.

During the early stages of the aphid infestations on the bean plots, when aphid-infested stems were comparatively few, there was no statistically significant association between coccinellid eggs and the presence of Aphids on the bean stems; but when all stems had become infested, egg batches tended to occur most frequently on the stems with the most Aphids. From these and other observations it is concluded that the female Coccinellids do not need the stimulus of the presence of Aphids before laying their eggs on beans, and that they concentrate on well-infested bean stems where they tend to stay and feed on the Aphids and probably oviposit on those stems. The distributions of older coccinellid larvae (3rd and 4th instars) indicate that they, too, tend to concentrate on well-infested stems.

The oviposition habits of the female Coccinellids are discussed in relation to the feeding problems of the newly-hatched larvae.

The numbers of Glossina pallidipes Aust. and G. morsitans morsitans Westw. flying in and out of a large clearing in Zimbabwe were estimated from catches on unbaited electrified nets placed on the perimeter of the clearing. By estimating the numbers of flies that would encounter visual and olfactory attractants in the middle of the clearing, and from measurements of the numbers caught responding and estimates of the efficiency with which responding flies were caught, it was calculated that 80–100% of flying tsetse responded to stimuli they encountered. The importance of flight as a means of encountering host stimuli in woodland and open areas, and with mobile and stationary baits, is discussed.

Host-seeking female tabanid flies, that need mammalian blood for the development of their eggs, can be captured by the classic canopy trap with an elevated shiny black sphere as a luring visual target. The design of more efficient tabanid traps is important for stock-breeders to control tabanids, since these blood-sucking insects can cause severe problems for livestock, especially for horse- and cattle-keepers: reduced meat/milk production in cattle farms, horses cannot be ridden, decreased quality of hides due to biting scars. We show here that male and female tabanids can be caught by a novel, weather-proof liquid-filled black tray laid on the ground, because the strongly and horizontally polarized light reflected from the black liquid surface attracts water-seeking polarotactic tabanids. We performed field experiments to reveal the ideal elevation of the liquid trap and to compare the tabanid-capturing efficiency of three different traps: (1) the classic canopy trap, (2) the new polarization liquid trap, and (3) the combination of the two traps. In field tests, we showed that the combined trap captures 2.4–8.2 times more tabanids than the canopy trap alone. The reason for the larger efficiency of the combined trap is that it captures simultaneously the host-seeking female and the water-seeking male and female tabanids. We suggest supplementing the traditional canopy trap with the new liquid trap in order to enhance the tabanid-capturing efficiency.

Mitochondrial ribosomal DNA is commonly used in DNA-based dietary analyses. In such studies, these sequences are generally assumed to be the only version present in DNA of the organism of interest. However, nuclear pseudogenes that display variable similarity to the mitochondrial versions are common in many taxa. The presence of nuclear pseudogenes that co-amplify with their mitochondrial paralogues can lead to several possible confounding interpretations when applied to estimating animal diet. Here, we investigate the occurrence of nuclear pseudogenes in fecal samples taken from bottlenose dolphins (Tursiops truncatus) that were assayed for prey DNA with a universal primer technique. We found pseudogenes in 13 of 15 samples and 1–5 pseudogene haplotypes per sample representing 5–100% of all amplicons produced. The proportion of amplicons that were pseudogenes and the diversity of prey DNA recovered per sample were highly variable and appear to be related to PCR cycling characteristics. This is a well-sampled system where we can reliably identify the putative pseudogenes and separate them from their mitochondrial paralogues using a number of recommended means. In many other cases, it would be virtually impossible to determine whether a putative prey sequence is actually a pseudogene derived from either the predator or prey DNA. The implications of this for DNA-based dietary studies, in general, are discussed.

To determine whether the brain medial neurosecretory cells (MNC) provide a hormone regulating ovulation and larviposition in females of Glossina austeni Newst., the effects of MNC ablations, sham operations, MNC implantations, and MNC extract injections were investigated. Ablation almost always inhibited ovulation and interfered with larval development and larviposition; it did not appreciably influence blood feeding, digestion or egg maturation. However, surgical brain trauma and even general stress also inhibited ovulation in control flies to some extent, though inhibition was more frequent and prolonged after greater trauma or incisions closer to MNC. A similar relationship existed between proximity of incisions to MNC and success of larval development and larviposition. MNC implants and extracts failed to induce ovulation in ablated flies. Most evidence indicates that MNC ablation affects ovulation and larviposition, not by removing a source of stimulatory hormone, but by interfering with nervous pathways necessary either for hormone release at some other site or for direct stimulation of the reproductive tract musculature.

Diurnal activity patterns and host preference of Glossina fuscipes fuscipes Newstead were studied in forest and linear habitats along Lake Victoria shore, Kenya. The objective was to identify the preferred hosts of G. f. fuscipes, the emanations of which may be attractive to this species. Hourly catches of flies in biconical traps were related to changes in the weather and the prevalence of hosts in the vicinity of traps. Flies were mainly active between 0800 and 1600 h, with males peaking around 1100 h and females around 1300 h. Activity of flies correlated directly with light intensity and temperature, but indirectly with relative humidity. Humans, livestock and the monitor lizard, Varanus niloticus, were the predominant hosts, although a significant positive correlation with fly catches could only be established with the prevalence of lizards. Blood meal identification by microscopic and serological methods showed that 73—98% of G. f. fuscipes fed on monitor lizards irrespective of host prevalence, season or location. The significance and possible epidemiological importance of the relationship between G. f. fuscipes and monitor lizards are discussed.

Why is the ground brown, when detritivores and decomposers have the numbers and ability to speed up the turnover of dark-coloured soil organic carbon? We consider this soil analogue to the ‘green world’ hypothesis measuring in the field how fast termites occupied cellulosic baits of varying quantity and quality and how predation risks by ants affect such encounters. Single baits with ants were occupied by termites later than triple baits without ants, implying that termites may spend longer searching for suitable food than feeding on it, thereby delaying decomposition rates of both chosen and neglected items. Because termites' feeding speeds up dissimilation of polymers by decomposers, such results may imply that bottom-up and top-down forces, ultimately, impair carbon processing and release from soil. We argue that the ground is brown partly because of delays imposed upon termites' use of resources by bottom-up and top-down forces.

Electrical penetration graphs (EPGs) were used to examine the probing behaviour of adult apterous Rhopalosiphum padi (Linnaeus) on barley seedlings grown under conditions of nitrogen or water stress. Aphids took significantly longer to reach and ingest from sieve elements of nitrogen-deficient seedlings than from nitrogen-sufficient seedlings but there were no such differences between water-stressed or well-watered seedlings. On both nitrogen and water-stressed seedlings the average length of each individual period of salivation into the sieve element was significantly greater compared with their respective unstressed controls.

The oviposition behaviour of Simulium decorum Wlk., S. vittatum Zett., S. verecundum Stone & Jamnback and S. vernum Macq. is described, with emphasis on the approach by the females to the egglaying sites, the substrates selected and the behaviour of the flies while laying. The eggs and egg-masses of these four species and S. longistylatum Shewell are described; the eggs can be distinguished on the basis of size, and a key is provided to aid their identification. Eggs of S. vittatum completed embryonic development and hatched more quickly than those of S. verecundum of the same age at both 15 and 24°C. The hatch rate of the eggs of both species exceeded 90% when the eggs were present in single-layered masses. The position of an egg Within a multi-layered mass had an important effect on its ability to complete development; significantly lower proportions of eggs of both S. verecundum and S. vittatum in the lowermost layers of large egg-masses hatched, compared with the hatch of those in the top layer. The location of an egg within an egg-mass must be considered a major factor of mortality in the egg stage. The eggs of neither S. verecundum nor S. vittatum were resistant to drying; mortality due to desiccation was related to both the duration of the drying period and the stage of embryonic development when they were subjected to drying.