A rapid technique is described for characterizing and monitoring, in single insects, the insensitivity of acetylcholinesterase (AChE) to organophosphorus and carbamate insecticides. Ninety-six insects are homogenized simultaneously in a microtitre plate and portions (e.g. 0·05 for Musca domestica L.) assayed colorimetrically with acetylthiocholine in the presence and absence of diagnostic concentrations of insecticide. Reactions are monitored by a kinetic microplate reader linked to a microcomputer that determines mean AChE activities automatically by linear regressions of absorbance-time data. Mean inhibited activity is then expressed as a percentage of uninhibited activity. Several inhibitors can be tested against the same insect to yield an ‘insensitivity profile‘ of individuals and strains. In tests on M. domestica adults of known AChE genotype, the assay clearly distinguished not only between a sensitive and two slightly (3-15-fold) insensitive AChE variants but between all six genotypic combinations of these three alleles.

The establishment and survival of larvae of Chilo partellus (Swinh.) on two sorghum cultivars in the six days after hatching was investigated in the field in India. During this period relatively few larvae are present outside the whorls of the plants, and the numbers present six hours and three days after hatching are proportional to the numbers hatching. The number of larvae in the plants declines during these first three days, but subsequently is stable. Some dispersal to adjacent plants occurs during this period and, at the plant spacing used, approximately seven plants were infested by larvae from a single egg-mass of 40 eggs. The relative susceptibilities of the two cultivars, IS 1151 and IS 2205, altered with the age and size of the plants. This is a vulnerable period in the life-history of the insect and attention should be focused on it in developing resistant cultivars, but because the susceptibility of the plants changes with age it is important to decide the age at which protection would have the greatest economic value.

Only pyrethroid insecticides have so far been recommended for the treatment of mosquito nets for malaria control. Increasing resistance of malaria vectors to pyrethroids threatens to reduce the potency of this important method of vector control. Among the strategies proposed for resistance management is to use a pyrethroid and a non-pyrethroid insecticide in combination on the same mosquito net, either separately or as a mixture. Mixtures are particularly promising if there is potentiation between the two insecticides as this would make it possible to lower the dosage of each, as has been demonstrated under laboratory conditions for a mixture of bifenthrin (pyrethroid) and carbosulfan (carbamate). The effect of these types of treatment were compared in experimental huts on wild populations of Anopheles gambiae Giles and the nuisance mosquito Culex quinquefasciatus Say, both of which are multi-resistant. Four treatments were evaluated in experimental huts over six months: the recommended dosage of 50 mg m−2 bifenthrin, 300 mg m−2 carbosulfan, a mosaic of 300 mg m−2 carbosulfan on the ceiling and 50 mg m−2 bifenthrin on the sides, and a mixture of 6.25 mg m−2 carbosulfan and 25 mg m−2 bifenthrin. The mixture and mosaic treatments did not differ significantly in effectiveness from carbosulfan and bifenthrin alone against anophelines in terms of deterrency, induced exophily, blood feeding inhibition and overall mortality, but were more effective than in earlier tests with deltamethrin. These results are considered encouraging, as the combination of different classes of insecticides might be a potential tool for resistance management. The mixture might have an advantage in terms of lower cost and toxicity.

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.

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 field of ecological immunology currently relies on using a number of immune effectors or markers. These markers are usually used to infer ecological trade-offs (via conflicts in resource allocation), though physiological nature of these markers remains elusive. Here, we review markers frequently used in insect evolutionary ecology research: cuticle darkening, haemocyte density, nodule/capsule formation, phagocytosis and encapsulation/melanization via use of nylon filaments and beads, phenoloxidase activity, nitric oxide production, lysozyme and antimicrobial peptide production. We also provide physiologically based information that may shed light on the probable trade-offs inferred when these markers are used. In addition, we provide a number of methodological suggestions to improve immune marker assessment.

Saliva was obtained by applying capillary tubes to the mouthparts of the cattle tick, Boophilus microplus (Can.), after the subcuticular injection of pilocarpine hydrochloride. Acid-lipid extracts of this saliva showed prostaglandin (PG)-like activity on bioassay. Chromatographic studies confirmed this activity as being due to PGE2. Extracts from homogenates of B. microplus larvae and salivary gland tissue also showed prostaglandin-like activity. A role for PGs in B. microplus feeding mechanisms is discussed.

A major assumption of the high-dose/refuge strategy proposed for insect resistance management strategies for transgenic crop plants that express toxins from Bacillus thuringiensis is that resistance traits that evolve in pest species will be recessive. The inheritance of Cry1F resistance and larval survival on commercially available Cry1F corn hybrids were determined in a laboratory-selected strain of European corn borer, Ostrinia nubilalis (Hübner), displaying more than 3000-fold resistance to Cry1F. Concentration-response bioassays of reciprocal parental crosses indicated that the resistance is autosomal and recessive. Bioassays of the backcross of the F1 generation with the selected strain were consistent with the hypothesis that a single locus, or a set of tightly linked loci, is responsible for the resistance. Greenhouse experiments with Cry1F-expressing corn hybrids indicated that some resistant larvae survived the high dose of toxin delivered by Cry1F-expressing plants although F1 progeny of susceptible by resistant crosses had fitness close to zero. These results provide the first direct evidence that the high dose/refuge strategy currently in place to manage resistance in Cry1F-expressing corn is appropriate.

The tobacco whitefly, Bemisia tabaci (Gennadius), causes severe crop losses in many agricultural systems. The worst of these losses are often associated with the invasion and establishment of specific whitefly biotypes. In a comprehensive survey of biotypes present in central China between 2005 and 2007, we obtained 191 samples of B. tabaci from 19 districts in Hubei province and its surrounds. Biotypes were identified by RAPD-PCR and by sequencing the mitochondrial cytochrome oxidase I gene (mtCO1). We determined that these central Chinese haplotypes included the world's two most invasive B. tabaci biotypes (B and Q) and two indigenous biotypes (ZHJ1 and ZHJ3). The B biotype shared >99.7% identity with other Chinese B biotypes and the Q biotype shared >99.5% of its identity with Q samples from the Mediterranean, USA, Africa and East Asia. By 2007, the Q biotype was dominant over much of Hubei province and appeared to be supplanting all other biotypes, although both the invasive and indigenous biotypes existed in sympatry in some regions. The invasion and rapid establishment of the Q biotype in China mirrors events elsewhere in the world, and we suggest that this is a consequence of its reproductive isolation, its polyphagous nature and its broad-spectrum resistance to insecticides. Its dominance has severe implications for the sustainability of some insecticide groups and for the production of a number of crops.

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.

The insect growth regulator buprofezin was tested using a leaf-dip assay on immatures of Bemisia tabaci (Gennadius). The method was robust and repeatable, and baseline data were calculated for a laboratory strain and a number of field collections from Pakistan where the insecticide has not been used. A baseline LC50 of 0.53 ppm buprofezin was defined and compared to other field collections. Populations known or suspected to have been intensively selected with buprofezin showed substantial tolerance to the insecticide at both the LC50 and at specific diagnostic doses, with the highest resistance factor of 47 fold in a population from the Netherlands. Reasons for the variation between populations, biotypes and geographical areas are discussed and the dangers of human-assisted movement of resistance genes are highlighted.

A sandwich enzyme-linked immunosorbent assay (ELISA) test was developed to detect blood-meals in insects and identify the host fed on. The test proved both sensitive and specific. Very small quantities of fresh blood (about 0·02 μl) can be detected; in practice, this enables blood in mosquitoes which are about three-quarters gravid to be identified. In trials in both Zambia and Britain, positive reactions were easily identified visually; consequently, this enabled the ELISA technique to be used as a routine field test. In addition to those of mosquitoes, blood-meals of a few Culicoides species were also successfully identified.

A series of host-transfer trials using both laboratory-cultured and field-collected individuals of the aphid parasitoids Aphidius ervi Haliday and A. rhopalosiphi De Stefani Perez were done in order to clarify inconsistent results from several previous studies. A. ervi cultured on Acyrthosiphon pisum (Harris) produced very few mummies when confined with Microlophium carnosum (Buckton), whereas those cultured on M. carnosum produced as many mummies on A. pisum as they did on their original host. Mummy production was correlated with the attack rate of adult parasitoids on potential hosts. The production of mummies on M. carnosum by parasitoids reared on A. pisum was often greatly improved if their male parent had been reared on M. carnosum, suggesting that genotype strongly influences host preference. Aphidius rhopalosiphi from laboratory cultures produced significantly more mummies on Metopolophium dirhodum (Walker) than on Sitobion avenae (F.) regardless of their original host, but this preference was not shown by parasitoids from field populations. It is concluded that inadvertent selection occurs in laboratory cultures of aphid parasitoids as a result of low founder numbers, genetic drift and genetic bottlenecks and that this can strongly influence experimental results in biology and behaviour studies, which has important implications for biological control workers.

The dynamics of Bemisia tabaci (Gennadius) were followed during two years in treated and untreated cotton fields in three locations in Israel. Two parasite species, Encarsia lutea (Masi) and Eretmocerus mundus Merc., were the only important natural enemies, but percentage parasitism did not rise with increase in the host population. The whiteflies reached peak populations at the end of the summer. Their distribution upon the plants was not uniform, rather, they tended to concentrate on a few leaves. The leaf bearing the maximal population was the sixth or seventh until mid-July. From then on, its location was variable according to the growth pattern of the foliage. Insecticide treatments, in particular with aldicarb, resulted in depression of both whitefly and parasite populations, but neither was exterminated.

A comparative analysis was performed on 18 mitochondrial DNA sequences, or haplotypes, of Lutzomyia (Nyssomyia) whitmani (Antunes & Coutinho) isolated by PCR from 28 individual flies originating from 10 Brazilian locations 150–2500 km apart. A phylogenetic analysis using maximum parsimony indicated support for three to four major lineages (Outgroups were haplotypes of Lutzomyia (Nyssomyia) intermedia (Lutz & Neiva)). One L. whitmani lineage was found in the Atlantic Forest zone of the North East, including the species' type locality, and is distinct from a second monophyletic group of haplotypes located in the drier interior of Brazil, stretching from the Tropic of Capricorn to Teresina just outside Amazonia. This provides no support for a previous hypothesis that L. whitmani sensu stricto is a single form widely-distributed south of Amazonia, and characterized by derived anthropophilic and synanthropic behavioural traits. The ranges of both lineages include populations incriminated in the peri-domestic transmission of Leishmania braziliensis sensu stricto. A third, Amazonian, group of haplotypes was less well-defined. It appears to consist of two sub-lineages which, like the two Leishmania species associated with them, are strictly silvatic and are separated by the Amazon floodplain. The zoophily of the Amazonian populations was not shown to be an ancestral trait. The geographical distributions of the Brazilian lineages are concordant with the broad patterns of bioclimate believed to have persisted since the late Tertiary period. These findings are part of ongoing research on the behavioural genetics of L. whitmani sensu lato aimed at understanding the evolution and maintenance of peri-domestic transmission of human cutaneous leishmaniasis.

Weekly observations on two populations of Culicoides impunctatus Goet. were made in 1948 at Bannachra and Wester Bannachra, near Loch Lomond, throughout the whole of the C. impunctatus season by means of “ sticky ” traps. Each site had an area of 5 acres of which half was composed of woodland and half of moorland. Twenty-two catching stations, each consisting of three traps placed 2 ft., 6 ft., and 10 ft. above the ground were erected on each site, equal numbers being placed in the woodland and moorland. There were therefore 132 traps to be changed weekly and a total of 67,033 Culicoides were trapped of which 65,576 (97·9 per cent.) were C. impunctatus. In 1949 observations were repeated only in Bannachra woodland.

The results have been analysed in the light of two alternatives (1) that C. impunctatus is a single biological entity and (2) that C. impunctatus is composed of two biological races.

When the seasonal effect was eliminated the stations showed very real differences between their weekly catches. Some stations recorded a large catch every week whilst others always recorded low catches. The total seasonal catch at each station was plotted on plans of the two sites and it then became apparent that there were two centres of high C. impunctatus density at Bannachra, one in the woodland and the other on the moorland, whilst at Wester Bannachra there were two foci in the woodland and a very diffuse zone of high midge density on the moorland. It has been shown that the centre of high midge density in Bannachra woodland was associated with a concentrated breeding place which supplied all the adults for the woodland (2½ acres) and moreover this centre remained unaltered in 1949. The importance of these observations on the control of C. impunctatus is discussed.

After the breeding place in Bannachra woods was discovered it became clear that the majority of adult C. impunctatus moved in an eastward direction from the breeding place and very few went westwards. This was attributed to the influence of the prevailing SW. wind. Knowing the centre of breeding in Bannachra woods it was possible to calculate the regression of the midge density on the distance from the breeding site. It was found that there was a linear relationship between the logarithm of the catch and the distance from the breeding site. A useful statistic is the reciprocal of the regression which may be designated as the density coefficient. It is the distance at which the density has decreased to l/10th of its initial value. The density coefficients for male and female C. impunctatus are 62·5 yards and 64·9 yards respectively. An attempt has been made to separate the effects of “ dilution ” and “ mortality ” on the density of C. impunctatus.

The mortality of male and female C. impunctatus is shown to be normally distributed with respect to the logarithm of the distance flown. These distributions are male l·867±0·197 (=73·6 yds. ; 46·8–115·9 yds.) and female 1 ·885±0·197 (=76·7 yds. ; 48·8–120·8 yds.).

From the density/distance formula the average distances flown by male and female C. impunctatus have been calculated. They are 79·0 yards (males) and 81·4 yards (females).

The analysis of the vertical distribution of C, impunctatus revealed that each station had its own definite pattern. The stations sited amidst the birch saplings showed very real differences between themselves which were not related to the ground flora. It is suggested that these are related to the height of the leaf canopy. Evidence was also produced which pointed to the fact that in the oak wood where the base of the leaf canopy was about 20 ft. from the ground, C. impunctatus had a self-imposed “ ceiling ” of little more than 10 ft.

The ground flora was found to have an appreciable effect upon the vertical distribution of C. impunctatus on the moorland. Thus where the ground flora provided only very shallow shelter, i.e., about 6 ins. in depth, equal numbers of adults were captured at each height, but when the stations were sited amongst Juncus sp. or in small sheltered clearings in the herb layer then more adults were caught on the 2-ft. trap. However, the shelter provided by bracken Pteridium aquilinum appeared to be less attractive and there were fewer adults caught on the 2-ft. traps at stations sited in dense bracken than at other moorland stations.

In the woodland the females were slightly more abundant on the 2-ft. trap and the males more numerous on the 10-ft. trap but the differences in distribution, although significant, were small. On the moorland the males were more abundant at 2 ft. and the females at 6 ft.

Although the general pattern was very similar there were highly significant differences between the horizontal and vertical distributions of the two races of C. impunctatus.

Apterous aphids need to move from ageing to younger leaves in order to survive UK winters. This behaviour was studied at low temperatures in field and laboratory trials using Myzus persicae (Sulzer) clones representing all five recognized categories of esterase-based insecticide resistance found in UK populations. Both studies showed that the tendency of aphids to move from deteriorating leaves was inversely related to their insecticide resistance level. This maladaptive behaviour associated with greater insecticide resistance could lead to increased risks of aphids becoming separated from plants after leaf fall, and subsequent death from starvation when adverse cold and wet conditions prevent return. Revertant clones, that had spontaneously lost extreme resistance to insecticides by ceasing to express their amplified esterase genes, tended to show similar behaviour to aphids that had retained their high resistance phenotypes. This implies that rates of movement were not related directly to esterase production.

Response to the alarm pheromone, (E)-β-farnesene, produced by many species of aphids, was assessed in laboratory bioassays using an aphid pest, Myzus persicae (Sulzer), and its primary endoparasitoid, Diaeretiella rapae (McIntosh). This was done in three separate studies, the first investigating responses of a large number of M. persicae clones carrying different combinations of metabolic (carboxylesterase) and target site (kdr) insecticide resistance mechanisms, and the other two investigating the responses of young virgin female adult parasitoids. In M. persicae, both insecticide resistance mechanisms were associated with reduced repellence suggesting that each has a pleiotropic effect on aphid behaviour. In contrast, D. rapae females were attracted to the alarm pheromone source. The implications of this apparent fitness trade-off for the evolution and dynamics of insecticide resistance, and the potential for using beneficial insects to combat resistance development are discussed.

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.