摘要:

Abstract.AdultAnopheles gambiaeGiles mosquitoes from Zanzibar were tested on a standard discriminating dose of DDT which reliably kills susceptible mosquitoes. Adults from wild‐caught larvae reared in the laboratory, and from the F1progeny of wild‐caught adults, showed less than 5% test mortality when newly‐emerged, but mortality rose with age to over 90% when they were 12–14 days old. Wild‐caught mixed‐age adults showed an intermediate mortality rate of 25%, close to the rate predicted from laboratory results for a fully resistant population with an age‐structure typical of this species in natural conditions.It is inferred that older, genetically resistant insects may be scored as susceptible, so that routine susceptibility tests with wild‐caught adults underestimate the frequency of resistance. In Zanzibar, such tests probably helped to persuade spraying authorities to continue spraying DDT in spite of resistance. Resistance which is restricted to younger insects may nonetheless reduce the effectiven

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00550.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00551.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Pupal parasitoids of muscoid flies were collected monthly on three farms in southern Israel in preparation for an IPM programme for the control of filth‐breeding flies.50% and 25.5% of viable puparia collected during 1985 and 1986/87, respectively, were parasitized. Three species ofSpalangiaLatreille and two species ofMuscidifuraxGirault&Saunders (Hymenoptera: Pteromalidae) accounted for 82.0% and 94.2% of parasitoids recovered in the two seasons.Variation in the seasonal abundance and distribution of the leading parasite species are discussed in connection with their conservation and possible use for augmentative releases within IPM project

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00552.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Laboratory studies at 25.5oC and 70–75% r.h. demonstrated that the average daily survival rate for females of the parasitoidSpalangia geminaBoucek (Hymenoptera: Pteromalidae) was 0.907 over a 20‐day period, with 50% mortality in 17.3 days. Mean immature developmental time ofS. geminawas 22 days and the population growth rate wasc.40‐fold per generation. The females successfully parasitized 1‐, 2‐ and 3‐day‐old pupae ofMusca domesticaL. and parasitism of 98–100% was obtained at parasitoid to host ratios of 1:0.5‐2.5. Parasitism of 81–87% was obtained at parasitoid to host ratios of 1:10. The male to female sex ratio was 1:1.59.S.geminaappears to have advantages over otherSpalangiaspp., which have immature development times of 28–32 days under comparable conditions, for the biologica

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00553.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1A simple artificial diet was devised for larvae ofLucilia sericataMeigen.2A basic diet of 20 g/1 agar with 20% horse blood and added yeast sustained normal growth and development, as compared with a lamb meat control.3When yeast was added to the blood agar diet at 50 gp>1, both peak and final larval weights were increased by 25–50% at higher larval densities (2–8 larvae/g diet) and the hatchling‐adult development period was reduced by about 3 days.4No adult insects emerged on an agar‐yeast diet without blood. Increasing the concentration of blood from 10% to 20% increased adult weight at emergence by 50%, though developmental period was not significantly affected.5Increasing larval density significantly reduced the weights of pupae and emergent adults (by up to 50%), both on the blood‐agar‐yeast diet and the lamb meat control. Percentage survival fell from 80–90% to below 10% on the blood‐agar‐yeast diet at the highest densities of 4 or 8 larvae/g diet, though survival on lamb was not significantly af

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00554.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.Microfilariae (mff) of the savanna and forest strains ofOnchocerca volvulus(Leuckart) were injected intrathoracically into adult females ofSimulium damnosumTheobaldsensu stricto, S.sirbanumVajime&Dunbar,S.squamosumEnderlein andS.mengenseVajime&Dunbar. Nine days post infection (pi) 27–29% of the savanna mff and 31–38% of the forest strain had developed to third‐stage larvae (L3), irrespective of the fly species, size or injection dose (5, 10 or 15 mff). Savanna flies supported the development of forestO. volvulusbetter than forest flies, in contrast to the results after perosinfections. Therefore, in these four species of theS.damnosumcomplex from Cameroon, the peritrophic membrane is considered to be the main factor limiting the success rate of microfilarial development following the ingestion of blood infections, while the fly's haemolymph and intracellular environment play minor

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00555.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The floating water fernAzolla microphyllaKaulfess was evaluated as a biocontrol agent against mosquitoes breeding in rice fields in Tamil Nadu, South India.Anopheles subpictusGrassi,Culex pseudovishnuiColless andCulex tritaeniorhynchusGiles were the predominant species of mosquitoes, with peak densities of late instar larvae and pupae occurring during the second week after transplantation of rice seedlings of short‐term (c. 80 days from transplantation to harvest) or medium‐term (c. 95 days) varieties.Immature mosquito populations were reduced by mats ofAzolla microphyllacovering more than 80% of the water surface. However, since 80% coverage byAzollawas achieved only 13–14 days after rice transplantation, its usefulness for mosquito control was limited.Azollamay have a greater potential in an integrated control programme, or in areas where long‐term varieties of rice are predominantl

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00556.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.The capacity of populations ofTriatoma infestans(Klug) (Hemiptera: Reduviidae) to survive and recover was assessed after application of insecticide (γ‐HCH at a rate of 0.5 g a.i./m2) at different seasons.T.infestanspopulations were maintained in experimental chicken houses under natural climatic conditions in a region of Argentina endemic for Chagas disease transmitted by these bugs. Based on previous studies ofT.infestanspopulations in these habitats, each experimental group was set up with a total of 626T. infestans, comprising 390 eggs, 204 nymphs of particular stages, fourteen male and eighteen female adults. The chicken houses were dismantled and rebuilt at monthly intervals to study the vector population changes over a period of 33 months.When the insecticide was applied during winter, spring or summer, populations ofT.infestansrecovered to untreated or precontrol levels during the next reproductive season (i.e. during the hot season, October‐March). In contrast, populations treated during autumn (March) remained at very low densities for 2 years and then increased rapidly to surpass the untreated populations. All populations of the bugs fell to very low numbers (sometimes less than twenty individuals) after y‐HCH applications, but none was driven to extinction. In all cases, the density of surviving populations was independent of their density before treatment. The fact that all treated populations recovered within 1–3 years, to at least the density of untreated populations, shows the high reproductive potential ofT. infestansto recover from very low population densities. Moreover, the additive effect of climatic‐induced mortality and insecticide‐induced mortality is only apparent when insecticides are applied just before the onset of the cold winter months during which reproductive rates are at

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00557.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.1The daily proportion of fed individuals in a population of the reduviid bugTriatoma infestans(Klug), maintained under natural climatic conditions in experimental chicken houses in central Argentina, was estimated from the proportion of bugs retaining colourless urine in the rectum.2From the estimates of feeding frequency throughout a 1 year period, it was shown that temperature has a dominant effect on biting rate, but density‐dependent effects became apparent during the warmest months.3These and other data on the determinants of blood consumption byT.infestans, were incorporated into a detailed hypothesis of density regulation in this specie

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00558.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY

摘要:

Abstract.FemaleGlossina pallidipesAusten trapped with baited NG2B traps were subjected both to detailed ovarian dissection and to nutritional analysis. Using a calibration curve derived from dissected wild‐caught, laboratory‐held flies, the field females were assigned by discriminant analysis to each day of the pregnancy cycle. Field females were most available to NG2B traps while carrying the first instar larva. The nutritional characteristics of trapped field females over the pregnancy cycle lead to the following main conclusions, (i) Fat levels increase most rapidly during the eggin uterostage, while CRDW increases significantly only during the larval stages, culminating in a 4mg increase during the last day of the third larval instar. (ii) The haematin content of the flies indicates that females feed at approximately 3‐day intervals and may feed on any day of the pregnancy cycle, (iii) The estimated time of feeding during the day corresponds with the observed time of peak activity, both of which are earlier in the day later in the pregnancy cycle, (iv) The rate of fat usage reveals significantly greater flight activity on day 5 of the cycle than on other days, agreeing with the high trappability on this day, and overall females appear to use fat at twice the rate of males. Reproductive data provide a much more accurate picture of the relative sampling efficiency than do nutritional data, although the latter reveal the general trends corr

ISSN:0269-283X    

DOI:10.1111/j.1365-2915.1991.tb00559.x

出版商:Blackwell Publishing Ltd    

年代:1991

数据来源: WILEY