In field studies on Glossina morsitans morsitans Westw. and G. pallidipes Aust. in Zimbabwe, various traps baited with attractive odour were used to study the behaviour of flies in each of several stages of response to traps, from the stage of being several metres from the trap to the stage of being retained in a cage on the trap. The numbers of flies that were caught by electrocution, or were observed, as they moved forwards through the stages of trapping were compared with the numbers caught or observed moving in a reverse direction. A variety of stimuli and modifications were investigated for their effects on these movements, leading to provisional recommendations for improving the speed and efficiency of trapping. The most important recommendations were: the outside of trap should be white, with black near the basal entrances, the entrances should be provided with tunnels projecting into trap, and the inside of trap should be made white at base and black at top. The top of the trap should be an open-ended tube around the cone of netting that leads to the retaining cage. Data for Stomoxyinae, non-biting Muscidae and Tabanidae are also presented.

New information on the intraseasonal progression of larval infestations of Busseola fusca (Fuller) in South Africa was obtained through repeated sampling in maize plantings of different planting dates over various seasons. Due to the occurrence of distinct periods of moth flight, variation in planting date had a marked influence on levels of larval infestation. Also, plants were found to be most attractive as sites for oviposition between three and five weeks after emergence, resulting in a definite pattern in the time distribution of different larval instars in different plant parts. In the pre-tassel stage of plant development, most larvae occurred in localized groups within the whorls, reaching maximum numbers eight weeks after plant emergence. The emergence of the tassel forced some larvae to migrate to adjacent plants, resulting in an increase of internally damaged plants without an increase in larval numbers. It is shown that scouting for eggs over a limited period of plant development can lead to better timing of spray applications and thus to more cost-effective control measures.

Eighteen strains of the complex of Culex pipiens L. from Africa, Asia and Europe were bioassayed for resistance to chlorpyrifos and electro-phoresed and stained for esterases. Susceptible strains showed only low activity esterase bands. The resistant strains of C. quinquefasciatus Say from hot countries (Liberia, Nigeria, Sri Lanka, Tanzania, Thailand) all showed the same two high intensity esterase bands (Rm 0·60 + 0·82). Different patterns of high esterase were found in resistant C. pipiens strains from cooler localities in Nairobi, Kenya (Rm 100), and Mont-pellier, France (Rm 0–50). Selection experiments on strains originally polymorphic for resistance and esterase pattern showed, without exception, that high esterase remained associated with resistance, and it is concluded that the association is almost certainly causal and not merely due to genetic linkage. The high intensity esterase bands were probably due to alleles of the loci Est-l, Est-2 and Est-3, separated by crossover distances of approximately 2·4 and 5·5 units, respectively. Strains monomorphic for what appeared to be the same high esterase pattern varied markedly in resistance level. Enzyme assays showed a direct relationship between levels of enzyme activity and resistance. Bioassays with fenthion and chlorpyrifos revealed differences in the relative resistance of C. quinquefasciatus from Colombo (Sri Lanka) and Dar-es-Salaam (Tanzania). Despite these differential degrees of cross-effectiveness, it is concluded that high intensity esterases are reliable indicators of organophosphate resistance in mosquitoes of the C. pipiens complex, although the possibility of other resistance mechanisms means that the lack of abnormally active esterases does not necessarily indicate the absence of resistance.

An account is given of a study of infestation of cowpea pods in the field in Northern Nigeria by the weevil, Piezotrachelus varius (Wagn.), and the Bruchids, Bruchidius atrolineatus (Pic) and Callosobruchus maculatus (F.). Oviposition by Bruchids did not commence until the pods were fully formed and light green in colour, whilst infestation by P. varius originated in the young pods. Observations indicated that a high level of parasitism of Bruchid eggs occurred, but that the majority of Hymenopterous parasites emerging from within the pods were related to P. varius.

When pods were harvested at regular intervals, large numbers of P. varius emerged from the early harvests only. B. atrolineatus was the predominant Bruchid species emerging, particularly from early harvests. In the case of a single final harvest of pods, large numbers of P. varius, and a higher level of infestation by B. atrolineatus than in pods collected at regular intervals, were recorded.

Shelling of four batches of pods indicated a mean of 11 per cent, of seeds attacked by Bruchids in the case of single final harvests, and a mean of only 3·5 per cent, in the case of regular harvests as pods became dry. It is concluded that a considerable improvement in quality would result from an adoption of the latter method by farmers, provided that some method of control in respect of the harvested pods were introduced.

From the observations made it is concluded that P. varius is a true field pest, B. atrolineatus primarily a field pest able to continue infestation in store to a very limited extent, and C. maculatus primarily a store pest able to commence its infestation in pods in the field and to build up in numbers rapidly during the immediate post-harvest storage period.

The normal manner of cultivation precludes the use of field methods of control at oviposition peaks but observations suggest that elimination of secondary hosts of P. varius and B. atrolineatus might be worthwhile. A reduction in oviposition by C. maculatus by treatment of stored cowpeas in growing areas, and treatment of pods during the immediate post-harvest storage period, should considerably reduce the level of infestation by this species.

Hibernation is still one of the obscure phenomena in the bionomics of Anopheles, for the nature of hibernation itself, as well as the associative changes of fat deposition and retarded ovarian development, have not as yet been made clear. Despite the extensive investigations on the subject, the factors responsible for hibernation remain unknown.

Seasonal population fluctuation of the coffee leafminer, Leucoptera coffeella (Guérin-Méneville & Perrottet) (Lepidoptera: Lyonetiidae), led to an investigation of its natural mortality factors during the rainy season when the population level is low and during the dry season when population peaks occur. Life-table data were colleted from insecticide-free plots within a 3 ha coffee plantation on the upper, medium and lower canopy. Leafminer mortality was similar among the canopy parts but varied in the two seasons studied. During the rainy season, the generational mortality averaged 94.3%, with 50.2, 33.7 and 10.4% occurring during egg, larval and pupal stages, respectively. During the dry season, total mortality was 89%, with 13.2, 61.0 and 14.8% occurring during egg, larval and pupal stages, respectively. Marginal mortality rates during the rainy season were highest for physiological disturbances, rainfall and egg inviability; but, in the dry season, they were highest for predaceous wasps, physiological disturbances and parasitoids. Egg and larval stages accounted for most of the mortality variation in the rainy season, while the combination of larval and pupal mortality better described the generational mortality in the dry season. Variation in mortality during the rainy season was primarily associated with egg inviability, rainfall and parasitoids. In contrast, predatory wasps and physiological disturbances were the main factors associated with mortality variation during the dry season. These results suggest that weather conditions, natural enemies and plant quality attributes are the main determinants of the population dynamics of L. coffeella.

Elucidation of the genetic variability of a model insect species, the grain aphid, Sitobion avenae (Fabricius), a predominantly asexual herbivore within the temperate agro-ecosystem tested, was initiated using molecular DNA markers (RAPDs). This revealed genetic profiles that appeared related to host adaptation at the specific level amongst the natural populations colonizing different grasses and cereals (Poaceae) within the same geographic location. These profiles were recorded either as ‘specialist’genotypes found on specific grasses, or as ‘generalist’ genotypes colonizing several host types including cultivated cereals or native grasses. These findings are compared with analogous systems found amongst insect species, including at a higher trophic level, i.e. interactions between hymenopterous aphid parasitoids. As the aphids and their respective plant hosts occur in the same geographical region at the same time, this appears to be a rare example of the evolutionary transition leading to sympatric speciation in insects. Hence, this study highlights the importance of understanding not only the demographic parameters to genetic diversity, but also the more intricate correlation of genetic diversity to host types in agricultural environments.

“ The condor lays a couple of eggs and the ostrich a score, and yet in the same country the condor may be the more numerous of the two ; the Fulmar petrel lays but one egg, yet it is believed to be the most numerous bird in the world. One fly deposits hundreds of eggs, and another, like the hippobosca, a single one ; but this difference does not determine how many individuals of the two species can be supported in a district.”—Charles Darwin, The Origin of Species.

The mealybug Maconellicoccus hirsutus (Green) occurs in many tropical and subtropical parts of the Old World and extends into some temperate areas. It has now reached the West Indies where it is causing extensive damage to plants. There is concern that it may be introduced to the southern USA and to Central and South America. A brief account is given of reported damage caused by M. hirsutus to some commercial and food crops in Asia and Africa and the species is redescribed. M. multipori (Takahashi), now known from a wide area in southern Asia, is redescribed, and M. ramchensissp. n. from Nepal, is described as new. These two species are closely related to M. hirsutus and can easily be mistaken for it. M. hirsutus and M. multipori are sometimes intercepted at quarantine inspection of plants and plant produce in the USA and Europe. In order to aid identification, a key is provided to the eight species presently included in the genus Maconellicoccus Ezzat.

Parasitoids of the Bemisia tabaci (Gennadius) species complex collected in Spain and Thailand were evaluated as biological control agents of B. tabacibiotype B in cole crops in Texas, USA. Parasitoids were identified by morphological and RAPD–PCR analyses. The most abundant parasitoid from Spain was Eretmocerus mundus Mercet with apparent field parasitism of 39–44%. In Thailand, Encarsia formosa Gahan, E. transvena Timberlake, E. adrianaeLopez-Avila, Eretmocerus sp. 1 and sp. 2 emerged, with apparent field parasitism of 1–65%. Identification and molecular classification of B. tabaciassociated with parasitoid collections and in the release site in Texas were accomplished using morphological traits and nucleotide sequence comparison of the mitochondrial cytochrome oxidase I gene (COI) (700–720 bp). Collections of B. tabacifrom Thailand grouped separately from B types from Arizona and Florida and the target B type from Texas, USA, a cluster from India, and other New World B. tabaci. The Spanish B. tabaci host of E. mundus which was laboratory and field-tested to achieve biological control of the B type was most closely related to non-B type B. tabaci populations from Spain and Sudan, the latter which formed a second group within the larger clade that also contained the B type cluster. Laboratory tests indicated that E. mundus from Spain parasitized more B. tabaci type B than did Eretmocerus spp. native to Texas and other exotic parasitoids evaluated. Eretmocerus mundus from Spain also successfully parasitized B. tabaci type B when field-released in a 0.94 million ha test area in Texas, and has significantly enhanced control of B. tabaci type B in California, USA. In contrast, parasitoids from Thailand failed to establish in the field in Texas, collectively suggesting a positive correlation between the centres of diversity of compatible parasitoid–host complexes.

Mosquitoes of the Anopheles maculipennis complex were collected in nine provinces of Iran (Esfahan, Fars, Gilan, Golestan, Kohkiluyeh va Boyerahmad, Mazandaran, Tehran, Azarbaijan-e Gharbi and Zanjan) between June 1983 and September 2002. The nuclear rDNA ITS2 sequences of 86 specimens were compared with those of seven species of the complex available in GenBank. Three genetically distinct species of the complex were distinguished: A. maculipennis Meigen, A. sacharovi Favre and a previously unrecognized species. The last species is most similar to, but clearly distinct from, A. martinius Shingarev and A. sacharovi. The taxonomy of A. martinius and A. sacharovi is critically reviewed, and justification is provided for formally recognizing the third species as Anopheles persiensissp.n. The new species is the first culicid to be characterized and named principally on the basis of DNA evidence. Anopheles persiensis was collected only in the northern Caspian Sea littoral provinces of Gilan and Mazandaran, and it seems likely that this species could be responsible for malaria transmission in this region that was previously attributed to A. maculipennis. A species-specific RFLP–PCR assay based on ITS2 sequences was developed to facilitate further studies of the three species in Iran.

The effect of artificial and natural sources of adult food on the survival and reproduction of the tropical fruit fly, Anastrephaserpentina (Wiedemann) was studied. Caged adult flies were exposed during their whole lifespan to water and one of the following diets: sucrose, intact fruit, open fruit, bird faeces, sucrose plus intact fruit, sucrose plus open fruit, sucrose plus yeast hydrolysate, and sucrose plus bird faeces. All flies exposed to intact fruit or bird faeces died within the first five days of adult life without laying eggs. Females exposed to open fruit exhibited the greatest mean longevity (56.7 days). The highest net fecundity rate was recorded from individuals exposed to sucrose plus yeast hydrolysate (164 eggs per female), followed by those exposed to bird faeces plus sucrose and open fruit (38 and 26 eggs per female, respectively). Some individuals were able to lay viable eggs late in life (>105 days of age). Only populations in which adult flies had access to either sucrose plus yeast hydrolysate, open fruit, or sucrose plus bird faeces exhibited positive intrinsic rates of increase (r). Flies offered a combination of dry sucrose plus open fruit exhibited greatly reduced net fecundity levels when compared with those individuals exposed to open fruit. Even more significantly, populations of flies offered the combination of open fruit plus sucrose exhibited negative rates of increase while those exposed to open fruit alone, grew. We postulate that this reduction in egg production can be explained by a ‘junk food syndrome’.

The population densities of Aedes aegypti Linneaus in four towns in Trinidad were studied using standard house-to-house inspections of all water-holding containers to determine whether persistently positive containers and premises existed over a three-month period in the wet season, from May to July 2002. From a total of 1503 houses inspected, 223 were positive with 41 persistently positive over the three month period and classified as ‘key premises’. The definition of the term key premises is described and the rationale for its utilization discussed. A total of 24,439 containers was inspected from Santa Margarita (6407), Mt Lambert (5709), St Augustine (5384) and Curepe (6939) of which 1.3% or 334 containers were positive for A. aegypti larvae and pupae. A total of 16,507 immatures of A. aegypti were retrieved from these containers which comprised 17 container types but when these were ranked according to productivity levels, only water drums (average 53.5%), buckets (22.2%), tubs and basins (8.0%), water tanks (5.4%), brick holes (4.2%) and tyres (2.0%) were significant (P < 0.001) producers. The role that key premises play in the introduction and re-infestation of A. aegypti-free communities is described and illustrated. These results suggest that A. aegypti control programmes could be more cost effective and sustainable by concentrating efforts on key premises and key containers to control mosquito densities and Dengue transmission while reducing manpower needs and insecticide use.

Dispersal of apterae from their natal plant was monitored for three aphid species (Myzus persicae (Sulzer), Brevicoryne brassicae (Linnaeus) and Megoura viciae Buckton), each on a different host plant. Some movement off the plant occurred even in the initial parental and second generations, when the plant appeared to be growing normally and when crowding was unlikely to be the cause. However, in most experiments the most marked increase in apterous dispersal coincided with a reduction or even cessation of plant growth. In nearly all the experiments this dispersal occurred when the population on the natal plant exceeded about 20 adults and their offspring per plant. The main emigrants were fourth instar apterae and prelarviposition adult apterae. The implications of this behaviour are discussed, and it is argued that apterous dispersal might be common in aphids, allowing a fuller utilization of the environment than would be likely by alate dispersal alone.

Four years of light-trap and crop survey data from the Namoi Valley of New South Wales are presented for Heliothis armigera (Hb.) and H. punctigera Wllgr. These suggest there are four generations a year. The associated seasonal sequence of major host-plants supporting successive generations, appeared to be: H. armigera—wheat; pre-flowering cotton; flowering cotton and sorghum; sorghum, flowering cotton and sunflowers; and H. punctigera—lucerne, linseed and medics; pre-flowering cotton; flowering cotton, sunflowers and soyabeans; lucerne, linseed and medics; pre-flowering cotton. On host-plants common to both species, a change in dominance from H. punctigera to H. armigera occured as each summer progressed. Suggested causes are: seasonal changes in the availability of host-plants, favouring H. armigera over H. punctigera; insecticide resistance in H. armigera; and the competitive superiority of H. armigera. Large numbers of H. armigera in cotton appeared to be related to: warm springs, which favoured moth emergence during the period of wheat anthesis; the incomplete control of infestations within cotton itself, leading to the development of resident populations; and the influx of moths from other host-plants, especially sorghum, during the latter half of the season.

An apparatus for determining the relative toxicities of contact insecticides is described in detail. It is so arranged that successive batches of insects are sprayed under conditions as similar as possible, so that on using various substances at different concentrations, the results are directly comparable.

The apparatus consists of a glass jar in the lid of which an atomiser is fixed. By means of compressed air at known pressure the atomiser throws a constant quantity of fine spray upon insects placed in a dish inside the jar. Photographs illustrating the details of the apparatus are given.

The method used in practice for the spraying of aphides in this apparatus is described, and examples are given in the form of a table and a graph of the type of results obtained when different concentrations of nicotine are sprayed upon apterous agamic females of A. rumicis.

Little is known about genetic differentiation and gene flow in populations of insect species that have a high genetic variability in dispersal but lack morphologically visible morphs that disperse. These characteristics apply to the codling moth, Cydia pomonella L. (Lepidoptera: Tortricidae), a major pest of fruits and nuts. Larvae were collected from three orchards each of pome fruits, stone fruits and nut trees in a major fruit growing area of Switzerland (Valais) and from six further (mainly apple) orchards throughout this country. Nine microsatellite loci were used to investigate genetic differentiation and the amount of gene flow among the sampled populations. All the loci were shown to be polymorphic in all populations. The number of alleles ranged from five to 15 over nine loci for the 15 populations. Significant genetic differentiation was noted among the populations from apple, apricot and walnut in the Valais region. Furthermore, among the eight populations sampled from apple in different geographic regions throughout Switzerland, AMOVA and pairwise FST analysis revealed significant population genetic differentiation even between populations collected from orchards ≪10 km apart. These results indicate that a distinct prevailing characteristic, in the present case the sedentary behaviour of the moth, can shape population architecture.

In urban landscapes, gardens provide refuges for bee diversity, but conservation potential may depend on local and landscape features. Foraging and population persistence of bee species, as well as overall pollinator community structure, may be supported by the abundance, richness, and spatial distribution of floral resources. Floral resources strongly differ in urban gardens. Using hand netting and pan traps to survey bees, we examined whether abundance, richness, and spatial distribution of floral resources, as well as ground cover and garden landscape surroundings influence bee abundance, species richness, and diversity on the central coast of California. Differences in floral abundance and spatial distribution, as well as urban cover in the landscape, predicted different bee community variables. Abundance of all bees and of honeybees (Apis mellifera) was lower in sites with more urban land cover surrounding the gardens. Honeybee abundance was higher in sites with patchy floral resources, whereas bee species richness and bee diversity was higher in sites with more clustered floral resources. Surprisingly, bee species richness and bee diversity was lower in sites with very high floral abundance, possibly due to interactions with honeybees. Other studies have documented the importance of floral abundance and landscape surroundings for bees in urban gardens, but this study is the first to document that the spatial arrangement of flowers strongly predicts bee abundance and richness. Based on these findings, it is likely that garden managers may promote bee conservation by managing for floral connectivity and abundance within these ubiquitous urban habitats.

Ninety-two individuals of Sitobion avenae (F.) collected throughout Britain in 1979 and 1980, were cloned and investigated genetically by electrophoresis of 14 enzymes representing 26 loci. Percentage polymorphism (P) differed considerably between years, 64% (16/25 loci) in 1979 and 19% (5/26) in 1980, whereas average heterozygosity () was low (ca. 2%) in both years and confined mainly to one locus, EST-1. The prevalence of homozygous allozyme variation supports ecological findings suggesting S. avenae to be largely anholocyclic in Britain. In 1981 and 1982, large populations, sampled from 11 sites in Britain and Spain, were examined at 13 loci. ranged from 2 to 7·6%, with heterozygosity restricted again mainly to EST-1. Some alleles were unique to certain geographical regions (including Britain or Spain); others showed significant spatial, and in two British populations examined in successive years, temporal frequency differences. Calculating Nei’s genetic identity (I) and distance (D) coefficients for each population pair mostly gave I>0·8, D<0·2 with overall means (± s.e.m.) of 0·896 ± 0·006 and 0·111 ± 0·006, respectively, which are comparable with geographical population values for other insects. D was poorly correlated with geographical distance, although values were slightly greater (ca. 0·025) for international population comparisons and did not overlap on a principal coordinates plot. The overall population similarity suggests substantial inter-population gene flow; geographical barriers may have restricted movements but seemingly have not led to allopatric race formation. P and values resemble those for many other aphids, but H values are lower than typically found in other insects. Possible causes of this heterozygote deficiency are discussed.