Realized heritability, h2, of resistance in European corn borer, Ostrinia nubilalis (Hübner), to Bacillus thuringiensisBerliner ssp. kurstaki endotoxins was examined in five resistant laboratory colonies. These colonies were reared on a meridic diet that incorporated a commercial formulation of B. thuringiensis, Dipel ES. Resistance in these colonies reached 42–67× by the seventh to twentieth selected generations and then plateaued. The realized heritability of resistance averaged 0.17–0.31 over all selected generations for the five colonies. In the three Iowa colonies, the highest realized heritability, 0.18–0.33, occurred during the second period of selection (seventh to thirteenth selected generations). In the two Kansas colonies, the highest realized heritability, 0.36 and 0.46, occurred during the first period of selection (first to sixth selected generations). In the absence of selection pressure, resistance in the southwest Kansas colony decreased from 62× to 42× after two generations, and remained at about that level for the next five generations.

Anagyrus mangicola Noyes, a primary parasitoid of the mealybug Rastrococcus invadens Williams, a pest of fruit crops in West Africa, was studied under controlled conditions at 27°C and 75% r.h. Data are given on the larval stages, their morphology and duration of immature development. The sex ratios of emerging parasitoids, adult longevity, host stage preference, the relationship of the size of the emerging parasitoid to host stage and development time are also investigated.

In the lower South-East of South Australia, adults of Aphodius tasmaniae Hope, which is an economic pest of improved pastures, emerge from the soil 2–3 days after rain has fallen in summer. The females may lay two batches of eggs. The first batch (about 35 eggs) is developed at the expense of the fat-body and is laid 3–6 days after emergence; a second batch (about 20 eggs) can be developed and laid after the female has fed on dung.

The beetles are crepuscular and fly after sunset if the weather is suitable for flight. The first batch of eggs may or may not be laid before flight, depending on the weather. Until the fat-body is largely depleted, beetles fly with the wind and are attracted to lights, but after that stage has been reached they fly upwind to dung and are not attracted to lights. After feeding on dung for a few days the females become gravid again, and apparently change their responses to light and wind once more. The distribution of larvae in the field suggested that adults aggregated and laid eggs in specific places. The factors which promote aggregations of adults were therefore studied.

The survival-rate of the females and the number of eggs they laid in two soils, a sand and a clay loam, were related to the ‘available water’ in soil as measured by the pF scale. Females survived in largest numbers and laid most eggs in the range of pF 2·8–3·2 in both soils. Similarly, when given a choice of a number of water contents in soil, beetles aggregated in largest numbers within the range 2·8–3·2 in one soil and pF 2·8–3·5 in another. In the latter soil, however, the pF values that were tested were more widely spaced, and it is suggested that the combined data are only intelligible if there was an optimum range of pF within the vicinity of 2·8–3·2 in both soils. These and other experiments indicated that moisture in soil was the major factor capable of' promoting aggregations of adults.

When water was not limiting, aggregations of beetles occurred on loose as opposed to compact surfaces. However, ‘shelter’ (dry grass stems broken off the parent plant, dung, etc.) was capable of promoting aggregations even if the soil underneath ordinarily inhibited burrowing. Aggregations of beetles also occurred on surfaces into which other beetles had previously burrowed; this was probably due not to any attraction of beetles to other beetles, but to loosening of the surface soil by the original beetles, which permitted later arrivals to burrow rapidly.

It is probable that the patchy distribution of larvae in the field is due to the aggregation of the adults in the field mainly in relation to moisture in soil, type of surface and shelter. It is also suggested that aggregations of larvae that occur around conspicuous objects, such as trees, result from beetles colliding with these objects by chance when they are flying after dark, dropping to the ground and burrowing into the soil to lay eggs there.

The establishment of the predatory histerid beetle, Teretrius nigrescens Lewis, following its field release in south eastern Kenya in 1992, and its impact on populations of the larger grain borer, Prostephanus truncatus (Horn), in woodland habitats is evaluated. Pheromone trap catch data show a single strong peak of P. truncatus from November to January, coincident with the short rains. Comparisons of P. truncatus pheromone trap catches before and after predator establishment, and in areas with and without T. nigrescens, show a sustained decline of over 80% in P. truncatus abundance over a 5-year period, following the establishment T. nigrescens. Concurrent laboratory studies of the impact of T. nigrescens on populations of P. truncatus raised on a wood substrate showed a 77% reduction in the growth of the pest population. These results are compared with published findings of the impact of T. nigrescens as a biological control agent of P. truncatus in west Africa.

By means of a laboratory spraying technique, ten comparisons were made of the resistance to rotenone of samples of adult apterous viviparous parthenogenetic females of the Pea Aphid, Acyrthosiphon pisum (Harris), reared on broad bean and on clover, respectively. In nine of the tests, the Aphids from clover were more resistant than those from broad bean, the ratios ranging from 1·1 to 2·5. These differences were not all significant. In the remaining test the Aphids. from broan bean showed a very small increase in resistance over the Aphids from clover which was not significant.

The Aphids from the clover were generally smaller than those from broad bean. Figures are given to show that while the total amount of poison retained by the larger individuals from broad bean was more than that retained by the smaller individuals from clover, the amount of poison retained per unit body weight was greater with the smaller individuals. It appears, therefore, that while the results obtained might be due, at least partially, to the greater total weight of poison retained by the larger individuals from broad bean, the difference in resistance between the insects from broad bean and clover, respectively, might be even greater if the poison were applied on the basis of equal weight of poison per unit of body weight. Since the difference in resistance between the Aphids from the two host-plants did not appear to depend primarily on difference in size, the assumption might be made that it is due to difference in nutrition. It was found that Aphids reared on clover had a significantly higher proportion of dry matter in their composition than those reared on broad bean, which may be taken as evidence that differences due to nutrition are being produced. These may lead to differences in resistance.

A description is given of the life history, biology and feeding habits of the cetoniine beetle Pachnoda interrupta (Olivier) (Coleoptera: Scarabaeidae) studied in pearl millet (Pennisetum glaucum) fields in north-west Mali. The third instar larva of this beetle, reared from the progeny of field captured adults, is also described and figured. Yield losses to a range of beetle densities (1–5 and 10 beetles/head) on millet heads have been estimated to range from 9 to 48% in caged trial experiments. The regression equation generated from these data may be used to establish economic injury thresholds and predict losses resulting from varying beetle densities.

Precipitin tests show that, on Ukara Island, Tanganyika, man and ox are the chief sources of blood to hut-resting mosquitos. Anopheles gambiae Giles and A. funestus Giles feed almost entirely on man. A. pharoensis Theo. feeds more on man than on ox. Culicines feed more on ox than on man.

Hand-catches off man, cow and goat in a hut confirm the results of precipitin tests on hut-resting mosquitos.

An account is given of the mosquito fauna of natural and artificial outdoor resting places and of the results obtained in precipitin tests on blood-fed mosquitos from outdoor resting places.

Blood-fed mosquitos resting indoors and outdoors were examined for nucleated red corpuscles in blood-meals. A. gambiae and Gulex annulioris Theo. feed on domestic fowl.

Experiments in the laboratory, to find the facility with which different species of mosquito will feed on small wild animals of the island, show that A. gambiae and certain Culicines feed on a wide variety of hosts.

A. gambiae and A. funestus are incriminated as almost entirely responsible for the transmission of bancroftial filariasis on Ukara Island. A little transmission may take place by A. pharoensis.

In the British Museum (Natural History) Ruwenzori Expedition 1934–35 vol. II nos. 3 (1939) and 4 (1940) generic keys to the Muscinae and Coenosiinae and specific keys to Graphomyia, Musca and the Coenosiinae of the Ethiopian region have been published. As there seems no possibility of the Museum issuing any more of these reports in the near future, it has been agreed that suitable extracts from the manuscript of the third part be published in this Journal, so that the keys and some other necessary data shall be available for the use of Entomologists in Africa.

The effect of aphid resistance in plant cultivars on parasitism of Myzus persicae(Sulzer) and Brevicoryne brassicae (Linnaeus) by Aphidius colemaniViereck was investigated under laboratory conditions using three cultivars of common cabbage, Brassica oleracea var. capitata. Significantly greater aphid populations were found on cv. Derby Day (green-leaved, susceptible to both aphid species), regardless of the presence or absence of parasitoids, compared with cv. Minicole (green-leaved, partially resistant with antibiosis factors for B. brassicae) or cv. Ruby Ball (red-leaved, partially resistant with antixenosis factors for B. brassicae). Minicole had the greatest proportion of parasitized aphids and Derby Day the least. A significantly lower percentage of emerged parasitoids were recorded on Minicole for both aphid species compared with Derby Day and Ruby Ball. The implication of the results are discussed in relation to the integrated control of aphids.

A technique is described in which twelve symbols or fewer can be chosen to code insects with individual marks suitable for mark-recapture studies. The method has been tested on Acrididae and has the advantages that (i) the code is self-checking against loss of marks, (ii) the application is practical, as only one colour is applied to a given individual, (iii) the versatility of the coding permits thousands of individuals to be distinguished, and (iv) an individual can be identified in the field from distances up to three metres without disturbance or rehandling. Guitar oil paints gave the most persistent marks, and were applied with a fine tubular-nib pen.

The Cicadellid, Empoasca lybica de Berg, is an important pest of cotton in the Sudan Gezira, where over 300,000 acres of cotton are grown annually under irrigation. Cotton is sown in mid-August, and the plants are uprooted and burnt the following May. The life-cycle of E. lybica from egg to gravid adult takes 16–24 days, and the adults live for up to 40 days. There is no diapause. During the 100 days from late August to early December when breeding on cotton is of economic importance, a single male and female could give rise to some 50,000 progeny.

During May to July, when crops are confined to irrigated gardens and river banks, E. lybica is widely distributed in such places and can be found also on tree hosts, which are numerous especially in the southern Gezira and along river banks. There is circumstantial evidence of displacement over long distances, and the great majority of catches of E. lybica in sticky traps were made before the increase in population on cotton that occurs from September onwards.

Of the 53 species of host-plants that have been recorded, only Solanum dubium, Rhynchosia memnonia, Hibiscus spp. and Abutilon spp. are of importance in the ecology of E. lybica. The first two especially are common weeds in fallows, which comprise more than half the land under rotation. Populations of E. lybica in Gezira fallows at the time of cotton germination tended to be greatest where pre-sowing rains (i.e., those falling from 1st July to 15th August) were highest. Correspondingly, initial infestation of cotton was highest in seasons and places receiving the most pre-sowing rains, although density of infestation in any place was affected by sowing date and proximity to irrigated fields and gardens which supported weed host-plants.

In order to develop a system of sampling for infestations of E. lybica in the cotton crop, the distribution of nymphs on cotton plants was examined. It was found that nymphs were most numerous in the leafiest zones of the plant and a random choice of leaves seemed an appropriate means of sampling for infestation. The distribution of nymphs within and between cotton fields was also investigated and a standard sampling procedure adopted.

Peak infestations on cotton could not be predicted from the level of initial colonisation, or from surveys a month later. Peak infestations were usually inversely related to the level of initial colonisation, especially when comparisons were made between seasons, as at the Gezira Research Farm. That is to say, high levels of initial infestation, which occurred in seasons of good pre-sowing rains, tended to be followed by low rates of increase, and in years of poor pre-sowing rains, initial infestations tended to be low and rates of increase high.

The relationship of these findings to those of Cowland & Hanna (1950) and Hanna (1950) are discussed; the hypothesis that pre-sowing mud-splash is a major factor controlling numbers of E. lybica in the Sudan Gezira is discounted, although it is accepted that this factor temporarily reduces populations.

The rate of increase of infestations of E. lybica was found to be positively correlated with the concentration of nitrogen recorded 2–4 weeks previously in the cotton leaf. This concentration affected not only the rate of increase of the initial colonisers, but also the rate of recovery of populations during November and December after spray-applications of DDT. The nitrogen concentration in the leaf was increased by nitrogenous fertiliser, with a corresponding increase in infestations of E. lybica. It was also found to be negatively correlated with pre-sowing rains, which, if low, prevent the nitrate in the top 12 in. of Gezira soil being washed to lower levels, but the data presented provide no evidence that the relationship is causal.

It is concluded that localities and seasons of poor pre-sowing rains favour a high rate of increase of small populations of E. lybica because of high nitrogen concentration in cotton leaves during September and October. This tendency is augmented by application of nitrogenous fertiliser. A regression equation relating the peak infestations of E. lybica with pre-sowing rainfall and with nitrogenous fertiliser is given and the infestations computed from this are shown not to differ significantly from those recorded in the Gezira as a whole, and in the four main divisions of it separately, during the eight years 1949–1956.

The cigarette beetle, Lasioderma serricorne (Fabricius), is a common pest of stored foods. A study of digestive proteinases in L. serricorne was performed to identify potential targets for proteinaceous biopesticides, such as proteinase inhibitors. Optimal casein hydrolysis by luminal proteinases of L. serricorne was in pH 8.5–9.0 buffers, although the pH of luminal contents was slightly acidic. Results from substrate and inhibitor analyses indicated that the primary digestive proteinases were serine proteinases. The most effective inhibitors of caseinolytic hydrolysis were from soybean (both Bowman Birk and Kunitz), with some inhibition by chymostatin, N-TOSYL-L-phenylalanine chloromethyl ketone, and leupeptin. Casein zymogram analysis identified at least eight proteolytic activities. Activity blot analyses indicated one major proteinase activity that hydrolysed the trypsin substrate N-α-benzoyl-L-arginine ρ-nitroanilide, and three major proteinase activities that hydrolysed the chymotrypsin substrate N-succinyl ala-ala-pro-phe ρ-nitroanilide. The absence of cysteine, aspartic, and metallo proteinases in L. serricorne digestion was evidenced by the lack of activation by thiol reagents, alkaline pH optima, and the results from class-specific proteinase inhibitors. The data suggest that protein digestion in L. serricorne is primarily dependent on trypsin- and chymotrypsin-like proteinases.

Common house flies, Musca domestica Linnaeus, were reared to pupation with exposure to ivermectin, washed, and then exposed to parasitism by Muscidifurax zaraptor Kogan & Legner. Pupae exposed to ≥ 0.25 ppm ivermectin produced 63% fewer parasitoids than did control pupae. Pupae exposed to 0.01 ppm ivermectin produced 23% more parasitoids. Exposure to 0.10 ppm ivermectin had no detectable effect. Treatments did not affect the developmental time of male or female F1parasitoids. Treatments did not affect the production of adult F2 progeny by F1 females, nor the sex ratios of these offspring. This study documents an indirect effect of ivermectin residues across trophic levels. It identifies altered host quality as another mechanism by which faecal residues of ivermectin may affect insect activity in dung of treated cattle. The importance of this phenomenon under field conditions is undetermined.

The effects of host and non-host plant odours on the foraging responses of the banana weevil, Cosmopolites sordidus (Germar), were investigated in the laboratory through arena and olfactometer bioassays. Contrary to previous reports that banana rhizome and pseudostem were the most attractive parts to the weevil, dead leaves were most preferred. Comparison of dead banana leaves with dead leaves of other plants showed that attractant odours were present in yam, cocoyam and dead grasses but absent in cocoa and soybean leaves. Complete leaf senescence while the leaf was attached to the mother plant proved necessary for the development of the dead-leaf-based odours but the involvement of microbial organisms could not be demonstrated. It is possible that dead-leaf-based attractants could be used in combination with microbials such as entomogenous fungi and nematodes in integrated management of C. sordidus.

The cabbage stem weevil (Ceutorhynchus pallidactylus (Mrsh.)) (Col., Curculionidae) is a serious pest of winter oilseed rape (Brassica napus L. var. oleifera Metzg.) in central and northern Europe. Although host-plant resistance is a key tool in integrated pest management systems, resistant genotypes are not yet available for this species. Resynthesized rapeseed lines (B. oleracea L.×B. rapa L.) are broadening the genetic diversity and might have potential as sources of resistance to pest insects. The host quality, of nine resynthesized rapeseed lines and six genotypes of B. napus to cabbage stem weevil, was evaluated in laboratory screening tests and in a semi-field experiment. In dual-choice oviposition tests, female C. pallidactylus laid significantly fewer eggs on five resyntheses and on swede cv ‘Devon Champion’ than on the moderately susceptible oilseed rape cv ‘Express’, indicating a lower host quality of these genotypes. Results of laboratory screenings were confirmed in a semi-field experiment, in which twelve genotypes were exposed to C. pallidactylus females. The number of larvae was significantly lower in two resyntheses and in cv ‘Devon Champion’ than in oilseed rape cv WVB 9. The total, as well as individual, glucosinolate (GSL) content in the leaves differed substantially among the genotypes tested. The amount of feeding by larvae of C. pallidactylus, as measured by a stem-injury coefficient, was positively correlated with the indolyl GSL compounds 3-indolylmethyl and 4-methoxy-3-indolylmethyl, and with the aromatic GSL 2-phenylethyl, whereas it was negatively correlated with 4-hydroxy-3-indolylmethyl. Thus, the composition and concentration of GSL compounds within the plant tissue might be a key factor in breeding for pest resistance in oilseed rape.

Pieris brassicae (Linn.) is a destructive cosmopolitan pest of cruciferous crops. It is present wherever its host plants occur, and it is considered to be one of the most widely distributed of all the Lepidoptera. We investigated the affect of various host plants on the food consumption and utilization by P. brassicae. We quantified consumption of food, larval duration, pupal duration and weight on cabbage (Brassica oleracea var. capitata), cauliflower (Brassica oleracea var. botrytis), radish (Raphanus sativus), broccoli (Brassica oleracea var. italica) and mustard (Brassica campestris) under laboratory conditions. Insect-host relationships can be better understood by knowing the rate of food consumption, its digestibility and conversion of food eaten to body tissue. The consumption of food generally increased with the advancement of larval age. In our study we found that consumption of food was highest on radish and lowest on broccoli. The highest consumption of a particular host does not always indicate greater suitability of that host, until and unless other factors like consumption index (CI), relative growth rate (RGR), efficiency of conversion of ingested food (ECI), approximate digestibility (AD) and efficiency of conversion of digested food (ECD) are also considered. In the current investigation, factors like CI, RGR, ECI and ECD were highest on cabbage. Low body weight of pupa is associated with rapid development. On cabbage, the weight of pupa of both sexes was found lowest. Thus, from the present study, it can be concluded that cabbage is a more suitable host for P. brassicae than other host plants evaluated. Hence, on cabbage, the values of Waldbauer indices were highest and P. brassicae developed with a faster rate.

The diamondback moth (DBM) (Plutella xylostella) is one of the main pests of brassicaceous crops worldwide and shows resistance against a wide range of synthetic insecticides incurring millions of dollars in control costs every year. The DBM is a prime example of the introduction of an exotic species as a consequence of globalization. In this study we analyzed the genetic population structure of the DBM and two of its parasitic wasps, Diadegma semiclausum and Diadegma fenestrale, based on mitochondrial DNA sequences. We analyzed DBM samples from 13 regions worldwide (n = 278), and samples of the two wasp species from six European and African countries (n = 131), in an attempt to reconstruct the geographic origin and phylogeography of the DBM and its two parasitic wasps. We found high variability in COI sequences in the diamondback moth. Haplotype analysis showed three distinct genetic clusters, one of which could represent a cryptic species. Mismatch analysis confirmed the hypothesized recent spread of diamondback moths in North America, Australia and New Zealand. The highest genetic variability was found in African DBM samples. Our data corroborate prior claims of Africa as the most probable origin of the species but cannot preclude Asia as an alternative. No genetic variability was found in the two Diadegma species. The lack of variability in both wasp species suggests a very recent spread of bottlenecked populations, possibly facilitated by their use as biocontrol agents. Our data thus also contain no signals of host-parasitoid co-evolution.

Cold winter temperatures significantly affect the biological control effort against water hyacinth, Pontederia ( = Eichhornia) crassipes Mart. (Pontederiaceae), in more temperate regions around the world. The population dynamics of the planthopper Megamelus scutellaris Berg. (Hemiptera: Delphacidae), a newly released biological control agent of water hyacinth, were recorded on the Kubusi River in the Eastern Cape Province (South Africa) over 15 months to determine the population recovery post-winter. Megamelus scutellaris incurred a severe population decline at the onset of winter when the water hyacinth plants became frost damaged. The combined effect of a population bottleneck and low minimum winter temperatures (6.12°C) below the agent's lower developmental threshold (11.46°C) caused a post-winter lag in agent density increase. Subsequently, the maximum agent population density was only reached at the end of the following summer growing season which allowed the water hyacinth population to recover in the absence of any significant biological control immediately post-winter. Supplementary releases of agents from mass-reared cultures at the beginning of the growing season (spring) is suggested as a potential method of reducing the lag-period in field populations in colder areas where natural population recovery of agents is slower.

Dormancy has been thoroughly studied for several species of economic importance in the genus Rhagoletis in temperate areas of North America and Europe. Much less is known on life history regulation for species inhabiting high-elevation areas in the subtropics at the southern extreme of their geographical range. Host plant phenology has been found to play a key role in generating allochronic isolation among sibling species and host races of Rhagoletis in the course of sympatric speciation, and has important implications for pest management. We compare the effect of winter length on survival to adult eclosion and dormancy duration among four species of Rhagoletis (three of them sympatric) exploiting hosts with different fruiting phenology in subtropical isolated highlands. Survival and duration of dormancy was found to be different among the four species. At 24°C, a very small proportion (<1%) of R. pomonella, R. turpiniae and R. zoqui completed development without becoming dormant, while in the case of R. solanophaga the majority of the population emerged after development within 40 days of pupation. Also, a large proportion of braconid parasitoids infesting Rhagoletis eggs and larvae emerged as adults without becoming dormant. Greatest survival after artificial winter was obtained for R. pomonella (50–60%) and R. zoqui (30%) after only four weeks at 5°C (a third of the time reported for studies on northern R. pomonella), while R. turpiniae, under identical environmental conditions experienced low adult emergence, and highest survival (11%) was recorded for flies exposed to 5°C during 10 and 12 weeks. For R. pomonella, there was a strong positive relationship between winter length and time to post-winter adult eclosion that was not observed for R. zoqui. In sum, for R. pomonella, mild winters in highland subtropical areas appear to select for flies better able to withstand longer periods of warm temperature before winter than flies exploiting late fruiting hosts and inhabiting northern latitudes. In the case of R. turpiniae and R. zoqui environmental cues such as fluctuations in humidity and/or different temperature thresholds (5°C) may play a more important role than winter length in life history regulation. Continuous host availability for R. solanophaga appears to have selected for non-diapausing flies. From an applied perspective our results are useful for handling flies in the laboratory to conduct research and suggest that non-diapausing strains of flies and parasitoids may be selected for SIT and innundative biological control programs.

Rice green leafhopper Nephotettix virescens (Distant) populations were collected in 1985 from fields planted with a leafhopper resistant rice, Oryza sativa cultivar IR64 in South Cotabato, Philippines. The populations were reared on IR64 for eight generations and tested on six cultivars, including susceptible TN1, moderately resistant IR26 and IR36, and resistant IR54, IR62, and IR64. Leafhoppers excreted larger amounts of basic honeydew, efficiently transmitted two tungro associated viruses, and showed greater population increase and lower nymphal mortality on all cultivars except IR62 than a greenhouse population reared on TN1. Nephotettix virescens were transferred and maintained on TN1, IR26, IR36, IR64, or a mixture of the four cultivars plus IR54 and IR56 in equal proportion. When the TN1-maintained colony was tested at the third generation, its feeding behaviour and tungro transmission rates on test cultivars were similar to those of the original population but amounts of basic honeydew excretion and the transmission rate on the resistant test cultivars were greatly reduced at the seventh or later generations. When the IR26-maintained colony was tested at the sixth, ninth, or 13th generation, it exhibited lower amounts of basic honeydew excretion on the resistant test cultivars but exhibited similar transmission efficiencies on other test cultivars. When the colonies maintained on IR36, IR64, or the cultivar mixture were tested similarly, their population characteristics and virus transmission efficiency were similar to the original population. These results indicate that N. virescens retain their ‘virulence’ to resistant cultivars when maintained on resistant cultivars, but quickly lose their ‘virulence’ when maintained on a susceptible cultivar. Colonies continuously reared on IR26, IR36 or IR64 showed ‘cross-virulence’ to many cultivars possessing a variety of genes for N. virescens resistance but often differed in feeding behaviour, virus transmission efficiency, and nymphal mortality on cultivars with the same genes for leafhopper resistance.