摘要:

Abstract.Communal oviposition by theSimulium damnosumcomplex of Afrotropical blackflies (Diptera: Simuliidae) was investigated under controlled laboratory conditions, using wild‐caught flies in Sierra Leone. Volatile compounds emitted bySimuliumeggs were trapped using a closed collection system, and their attractiveness to gravid flies was tested in a two‐choice behavioural bioassay. Significantly more female blackflies oviposited on substrates baited with freshly laid eggs (100% chose the baited substrate), or with the volatiles collected from freshly laid eggs (85% chose the baited substrate), in preference to the relevant control substrates. Substrates baited with volatiles from 12‐h‐old eggs were not significantly more attractive than controls (only 31% chose the baited substrates; P = 0.33). Gas chromatographic analysis of the egg volatiles consistently showed two peaks emanating from fresh eggs, but significantly lower amounts from 12‐h‐old eggs (P<0.05). A novel system for collecting the volatiles from this and other blackfly species, as they laid eggs on a substrate in flowing water, is described. Volatiles collected using this method showed identical gas chromatographic profiles to those of fresh eggs alone, indicating that the flies themselves produced no other volatile chemical signals during oviposition. Evidently communal oviposition byS. damnosum s.l. was mediated by a pheromone emanating from fresh eggs. The role of pheromone‐mediated egg aggregation in blackfly ecology is discussed, and its possible manipulation

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00165.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Three models for feeding in female tsetse are considered. Model I: there is a prolonged non‐feeding phase after each meal followed by feeding at a constant rate, with a constant probability of dying as a consequence of feeding. Model II: the feeding rate increases linearly after each meal. Model III: the feeding rate increases exponentially after each meal. In Models II and III the feeding hazard is a linear function of the probability of feeding. Production of viable female offspring is estimated under each model, making allowance for losses of adults due to starvation and to background and feeding mortality, losses of pupae due to predation and parasitization, and losses of young flies if their mothers take insufficient blood during pregnancy. Under Model I, if females require three meals to produce viable pupae in 9 days, then for a non‐decreasing population with a background mortality of 1%/day, and 25% pupal losses due to predation and parasitism, the feeding risk must be ≤5%/feed. At this maximum level the non‐feeding phase should be 2–2.5 days for optimal productivity, with a mean feeding interval of 60–72 h. If the background mortality is 2%/day, feeding losses cannot exceed 1%/feed for a non‐decreasing population. If four or five meals are required for the production of fully viable pupae, the optimal values of the non‐feeding phase and mean feeding interval tend towards 1 and 2 days respectively. Under Models II and HI the mean feeding interval is 50–60 h for optimal productivity (with variances 3 times as large as for Model I), in good agreement with estimates from recent models for feeding and digestion. Field evidence suggests that feeding tsetse take greater risks as their fat levels dwindle. This should result in feeding (and feeding mortality) rates which increase during the feeding phase ‐ as assumed in Models II and III but not in Model I. These models allow greater flexibility than Model I, because flies can feed early in the hunger cycle, at low probability, as long as the feedi

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00166.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.The incorporation of soybean trypsin inhibitor (SBTI) into the diet of the buffalo fly,Haematobia irritans exigua(De Meijere), results in increased mortality and reduced fecundity. A trypsin‐like enzyme which binds to SBTI was isolated by affinity chromatography on a Sepharose‐SBTI column followed by ion‐exchange chromatography. The enzyme was inhibited by benzamidine, phenylmethylsulfonyl fluoride, ovomucoid, leupeptin and a‐2 macroglobulin. The enzyme was not inhibited by EDTA or p‐chloromecuribenzoic acid and had a broad pH optimum of pH 7–9. Vaccination of sheep produced antibodies specific for the trypsin‐like enzyme which inhibited enzyme activityin vitrobut did not affect the survival of flies maintained inin

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00167.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.As the composition of natural sugars in the diet of adult sandflies (Diptera: Psychodidae: Phlebotominae) may affect the development ofLeishmania(Kinetoplastida: Trypanosomatidae) in sandfly guts, and so play an important role in the epidemiology of leishmaniasis, there is increasing interest in the sources of sugars for wild sandflies. Advanced chromatography techniques have provided indirect evidence that wild sandflies feed on honeydew, a substance released by aphids (Hemiptera: Aphididae) when feeding. Our objective was to determine whether sandfly density can be influenced directly by the local density of aphids. Aphid density was determined by counting absolute numbers of aphids on alfalfa stems in Purisima Valley, Peru, where sandflies transmitLeishmania peruvianacausing Andean cutaneous leishmaniasis (uta). Sandfly relative abundance was measured using sticky trap sampling repeatedly in alfalfa fields.Lutzomyia verrucarumaccounted for 92% of the total sandflies collected. As there was a female bias in sandflies collected close to houses, only the numbers of male sandflies were used in analysis. Most of the adult aphids found feeding on alfalfa were eitherTherioaphis trifoliiformamaculata(97%) orAcyrthosiphon pisum(3%). By regression analysis, a significant relationship was found between the density ofLu. verrucarummales and the density of adults of both aphid species. This is the first ecological study to support the hypothesis that aphid honeydew may be a source of sugar for sandflies.

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00168.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.The effect of repeated infestations ofIxodes ricinus(L.) nymphs on BALB/c mice was studied. Four successive infectations resulted in an increase of tick feeding success. Tick yield and mean engorged weight increased and the length of the feeding period was reduced significantly(P0.05). The blastogenic response of spleen lymphocytes to T‐cell mitogens (Con A and PHA‐P) was unimpaired or slightly enhanced, whereas the response to B‐cell activators (LPS and PWM) was suppressed, as was the total antibody generationin vitro.The numbers of mast cells in murine skin at the tick attachment sites slightly decreased during the third infestation. The suppression of B‐cell competence and of antibody generation, together with decrease of skin mast cell numbers in tick attachment sites, are considered to be responsible for enhancement of tick feed

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00169.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.In preparation for a trial of polystyrene beads and pyriproxyfen for the control ofCulex quinquefasciatusmosquitoes, surveys of their breeding were carried out in two contrasting areas of Dar es Salaam, Mikocheni and Ilala, during the dry season.Sanitation structures (latrines, soakage pits, septic tanks and cess pits) were the most prolific breeding places, totalling 780 in Mikocheni and 1544 in Ilala. Those in Mikocheni were estimated to contain about 1.4 times more mosquito pupae, per site, than in such structures in Ilala. This was both because a higher proportion of sites contained visible water and because sites with water were more likely to contain pupae in Mikocheni. The relative importance of the different types of structure, in terms of productivity, was the same in both areas. Although septic tanks and cess pits made up only 10.5% of the on‐site sanitation structures in Ilala, they contained 53% of the total number of pupae in enclosed sites; they were therefore particularly important targets for treatment with polystyrene beads. A survey during the rainy season of sites in Ilala revealed little change in the proportion that were wet, or in the frequency of breeding in those with visible water.The number, type and area of open breeding sites varied greatly between the two study areas. In Mikocheni the area of open breeding sites was 100 times greater than in Ilala, with 97% of the13,000 m2being flooded grassland. In Ilala all but four of the sixty‐six open breeding sites were puddles of sullage water derived from bathrooms. Different strategies for control in open breeding sites are required in the two areas of Dar es Sal

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00170.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.In two contrasting areas of Dar es Salaam (Ilala and Mikocheni) all enclosed breeding sites ofCulex quinquefasciatus, such as latrines and septic tanks, were treated with a floating layer of expanded polystyrene beads. 7 months later checks in both study areas revealed only one site (from which the polystyrene had been removed during emptying) containing immature stages ofCx quinquefasciatus.Open breeding sites such as areas of flooded land and blocked drains were treated with pyriproxyfen (an insect growth regulator) at a concentration of 0.1 ppm. Emergence ofCx quinquefasciatusadults from these sites was inhibited for 4 weeks during the rainy season and for up to 11 weeks during the dry season.The problem of mosquito breeding sites caused by bathroom sullage water was addressed through a combination of health education and indirect pressure from the Urban Malaria Control Project (UMCP) via local community leaders. Households responsible for these sites were encouraged to eliminate them by diverting the water into an enclosed drainage structure, usually a pit latrine. After two weekly visits 64.7% of households had complied and 93.4% had complied after five visits. 5 months later, only 15.7% had reverted to allowing sullage water to collect into puddles.Densities ofCx quinquefasciatusadults dropped by 76.7% in Mikocheni and by 46.2% in Ilala following intervention, but increased by 84.9% and 25.6% in two untreated comparison areas. The reasons for differential success of the combined interventions in the two treated areas are discussed.

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00171.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Host blood effects onTrypanosoma congolenseestablishment inGlossina morsitans morsitansandGlossina morsitans centraliswere investigated using goat, rabbit, cow and rhinoceros blood. Meals containing goat erythrocytes facilitated infection inG. m. morsitans, whereas meals containing goat plasma facilitated infection inG. m. centralis.Goat blood effects were not observed in the presence of complementary rabbit blood components. N‐acetyl‐glucosamine (a midguMectin inhibitor) increased infection rates in some, but not all, blood manipulations. Cholesterol increased infection rates inG. m. centralisonly. Both compounds together added to cow blood produced superinfection inG. m. centralis, but not inG. m. morsitans.Midgut protease levels did not differ 6 days post‐infection in flies maintaining infections versus flies clearing infections. Protease levels were weakly correlated with patterns of infection, but only inG. m. morsitans.These results suggest that physiological mechanisms responsible for variation in infection rates are only superficially similar in these closely‐related

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00172.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Dispersal of the Old World screw‐worm fly,Chrysomya bezzianaVilleneuve, was studied in Papua New Guinea by releasing radio‐isotope labelled, laboratory‐reared flies and collecting their labelled egg masses from sentinel cattle. A log‐linear model was developed to describe recapture rate. Distance was found to dominate the model and was represented by a bilinear (‘broken‐stick’) term as log‐distance. Further terms in the model such as attractiveness of the site (estimated from the number of non‐labelled egg masses), the season of the year and a time trend were statistically significant but of minor importance. From the model, the median distance females dispersed before depositing an egg mass was 10.8 km. The maximum distance from the release site that egg masses were recovered was 100 km.The dispersal ability ofC. bezzianais discussed in terms of its impact on the prospects of eradicating this species using SIRM if an outbreak occu

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00173.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY

摘要:

Abstract.Hessian curtains impregnated with deltamethrin 50 mg/m2were hung in the eaves and doorways of eight one‐roomed huts in Madurai, Tamil Nadu State, South India. Statistically significant reductions of indoor‐resting and man‐biting densities of the mosquitoesAnopheles subpictusandCulex quinquefasciatuswere observed for 14 weeks, in two field trials. Bioassays on curtains in the field showed over 50% mortality ofCx quinquefasciatusandAn. stephensifor up to 8 weeks. The curtains were highly acceptable to the community, and cost approximately Rs.33.15 (US1.05) for material and Rs.10 (0.32) for deltamethrin per hut, totalling Rs 53.15 (1.70) for two impregnations giving 6 months protection. Comparative costs of house‐spraying with residual insecticides are estimated as Rs.1.92 (0.06) for two rounds of DDT at lg/m2, or Rs.40 (1.27) for three rounds of malathion at 2g/m2. Therefore the relative annual cost of protection using deltamethrin‐impregnated hessian curtains is 28× or 1.3× more than for house‐spraying with DDT or malathion, respectively (excluding operational

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1995.tb00174.x

出版商:Blackwell Publishing Ltd    

年代:1995

数据来源: WILEY