Rapid isolation of anopheline mosquito eye-colour mutants, based on larval colour change

Abstract. A method is presented for the rapid isolation of eye-colour mutants in anopheline mosquitoes based on their inability to undergo a background-stimulated morphological colour change. For application of this method, larval mosquitoes, whose grandfathers had been mutagenized, were reared in black containers and examined with the naked eye en masse during the third or fourth instar. The vast majority of larvae became dark-coloured; however, rare exceptional pale larvae were observed and examined individually microscopically. Approximately half of the pale types examined were eye-colour mutants. By this method, seven sex-linked mutations in the mosquito Anopheles gambiae s.s. were easily isolated. Additional existing anopheline eye-colour mutants in An. gambiae and An. stephensi were tested and were found to be unable to undergo colour change. Several applications of this simple technique are suggested.     

Effects of permethrin at different temperatures on pyrethroid-resistant and susceptible strains of Anopheles

The influence of temperature (16, 22, 28, 37 degrees C) on effects of permethrin was investigated for susceptible and pyrethroid-resistant strains of the mosquitoes Anopheles gambiae and An. stephensi (Diptera: Culicidae). Young unfed female adult mosquitoes were exposed to 0.25% permethrin test papers or to polyester netting treated with permethrin 500mg a.i./m2. The time to 50% knockdown (KT50) declined as temperature increased, i.e. there was a positive temperature coefficient of this effect of the pyrethroid. Resistance ratios (comparing KT50 values) between resistant and susceptible An. stephensi ranged between 2.5 and 4.4 at the different temperatures. Comparative tests of pyrethroid tolerance of different strains would be valid over the 22-28 degrees C range but, when using a discriminating dose to detect resistance, more precise temperature control is desirable. Mortality 24h after exposure to 0.25% permethrin of both susceptible and resistant strains of An. stephensi showed a negative correlation with temperature between 16 and 22 degrees C and a positive correlation at higher temperatures. In An. gambiae, however, the correlation was positive over the whole range. Irritancy of permethrin-treated netting to Anopheles females (measured as time lapse until first flight take-off, and the number of take-offs during 7.5 min exposure) was positively correlated with temperature in all four strains and was much greater for the susceptible than the resistant strains.     

The relative efficacy of repellents against mosquito vectors of disease

Laboratory tests of insect repellents by various different methods showed that An.stephensi Liston was consistently more susceptible than An.gambiae Giles, An.albimanus Wiedemann or An.pulcherrimus Theobald. The six repellents tested were di-ethyl toluamide (deet), di-methyl phthalate (DMP), ethyl-hexanediol, permethrin, citronella and cedarwood oil. Testing systems in which the mosquitoes were presented with a choice gave consistently lower ED50 values than when there was no choice, i.e. the standards of tolerance are not absolute but depend on the options available. In field tests in an experimental hut a curtain with a high dose of di-ethyl toluamide (deet) reduced biting in the hut but had to be re-impregnated frequently. Deet-impregnated anklets gave about 84% protection against Culex quinquefasciatus Say for 80 days after one impregnation, in a trial in which the anklets were brought out of sealed storage and tested for 2 h nightly. Similar protection was found against An.funestus Giles but the protection against An.gambiae s.l., An. coustani Laveran and Mansonia spp. was not as good. There were highly significant differences between the four collectors' mosquito attractiveness but this varied highly significantly between the mosquito species.     

Rubidium marking of Anopheles mosquitoes detectable by field-capable X-ray spectrometry

We present a mosquito marking technique suitable for mark-release-recapture that can be used with a hand-held, portable X-ray fluorescence (XRF) spectrometer, which is practical for field measurements. Third instar Anopheles gambiae Giles sensu stricto (Diptera: Culicidae) and Anopheles stephensi Liston larvae were cultured to pupation in water containing rubidium (Rb) Cl at concentrations up to 1000 p.p.m. Rb. Anopheles gambiae larvae survived to adulthood at concentrations as high as 1000 p.p.m. Rb but suffered pupal mortality and reduced adult longevity at high concentrations. We were able to culture An. stephensi at Rb concentrations as high as 300 p.p.m. The presence of Rb in adults was evaluated using a portable XRF analyser, and we were able to reliably detect Rb above background levels in 10-day-old females and 4-day-old males at concentrations causing minimal pupal or adult mortality. We observed that Rb marking was not permanent, and the concentration declined significantly as adults aged. The low cost of labelling with RbCl and the field portability of the spectrometer provide a useful means for labelling mosquitoes via breeding sites or in the laboratory for mark-release-recapture experiments.     

Activity and mating competitiveness of γHCH/dieldrin resistant and susceptible male and virgin female Anopheles gambiae and An.stephensi mosquitoes, with assessment of an insecticide-rotation strategy

The effects of gamma HCH/dieldrin resistance genes on flight activity and mating competitiveness were investigated in males from backcrossed strains of Anopheles gambiae Giles and An.stephensi Liston. Activity of males and virgin females of both species, as recorded in an acoustic actograph, occurred mainly at dusk (the E peak). The activity pattern of An.gambiae males was not affected by resistance genes; in mating competition and predator avoidance experiments, however, RR males were less successful than RS males which were less successful than SS males. The activity pattern of An.stephensi differed from An.gambiae in that the E peaks of RR males and females in a gradual dusk regime were out of synchrony with those of SS and RS, the E peaks of RR occurring slightly later. Thus, RR males and females tended to mate assortatively in mate competition experiments. When a sudden dusk regime was substituted for the gradual dusk regime, activity of RR An.stephensi became synchronized with SS and RS activity, but in mating competition experiments RR still tended to mate assortatively. Estimates of male competitiveness, together with previously-obtained estimates of female fitness, were included in population genetics models. Computer simulations showed that the frequency of resistance in populations of An.gambiae and An.stephensi should decrease in the absence of insecticide at a rate comparable with known field reversions.     

Pteridine concentrations differ between insectary-reared and field-collected Anopheles albimanus mosquitoes of the same physiological age

Biopterin, isoxanthopterin and 6-pterincarboxylic acid were identified in the head of the malaria vector mosquito Anopheles albimanus Weidemann (Diptera: Culicidae) by HPLC. Total pteridine concentrations (TPC) were estimated in heads, body parts (BP: abdomen, legs and wings) and whole bodies of insectary-reared and field-collected females, by spectrofluorometry, to investigate whether they could be used for age determination. Pteridine concentrations diminished with age in both mosquito groups. TPC correlated with chronological age in insectary-reared sugar-fed females (heads: r2 = 0.35, BP: r2 = 0.34, P < 0.001), but lower correlation occurred in blood-fed females (heads: r2 = 0.22, BP: r2 = 0.27). TPC differed among females of the same age fed with blood at different times (P < 0.05), indicating that bloodmeals modify the diminution rate of pteridines with age. Nevertheless, a polynomial significant correlation was documented for TPC and the number of ovipositions (heads: r2 = 0.24, BP: r2 = 0.27, whole body: r2 = 0.52, P < 0.001) in insectary-reared mosquitoes. This correlation was lower in field-collected mosquitoes (heads: r2 = 0.14, BP: r2 = 0.10, P < 0.05), which showed a remarkable pteridine increase in one-parous females. The correlation of TPC in whole body with physiological age was much less (r2 = 0.03). These observations indicate that TPC determination by spectrofluorometry is not a reliable method to estimate the age of An. albimanus females from the feral population.     

Observations on the Anopheles gambiae complex in the Senegal River Basin, West Africa

1. Three sibling species of mosquitoes of the Anopheles gambiae complex are found in the Senegal River Basin: An. melas Theobald, An. gambiae Giles and An. arabiensis Patton. 2. An. melas is restricted to the river delta and environs where saltwater breeding places are present. 3. An. gambiae and An. arabiensis are sympatric in the study area; An. arabiensis predominates in coastal zones where it breeds also during the dry season; An. gambiae predominates in inland areas where breeding is mostly restricted to the rainy season (July-September). 4. An. arabiensis is chromosomally polymorphic all over the study area, with much variation of inversion frequencies, particularly for the 2Ra arrangement. 5. An. gambiae is characterized by a very high frequency of the 2Rb-2La inversion arrangement which is typical of the Savanna chromosomal form.     

斯氏按蚊中Toll受体参与抵抗微生物感染和调控肠道菌群稳态

【目的】Toll信号通路是昆虫天然免疫系统的重要组分,其中Toll受体在激活昆虫病原菌侵染免疫应答方面发挥了关键作用。本研究旨在探究斯氏按蚊Anopheles stephensi Toll受体基因在抵抗微生物侵染和维持肠道菌群稳态过程中的功能。【方法】根据冈比亚按蚊Anopheles gambiae Toll受体家族的蛋白氨基酸序列,通过序列同源比对鉴定斯氏按蚊中相应的Toll受体基因;运用荧光定量PCR检测Toll受体基因在未感染病原菌的斯氏按蚊脂肪体中的相对表达量,以及在真菌球孢白僵菌Beauveria bassiana和革兰氏阴性细菌胡萝卜软腐欧文氏菌Erwinia carotovora subsp. carotovora侵染斯氏按蚊过程中的表达变化;最后,在斯氏按蚊雌成蚊胸部显微注射AsToll1A和AsToll5A的双链RNA进行RNA干扰后,检测RNAi处理的斯氏按蚊受真菌侵染后的存活率、肠道细菌含量变化以及抗菌肽基因表达变化。【结果】在斯氏按蚊中共鉴定到8个Toll受体基因,即AsToll1A, AsToll5A, AsToll6, AsToll7, AsToll8, AsToll9, AsToll10和AsToll11。通过荧光定量PCR检测发现,未感染病原菌的斯氏按蚊雌成蚊脂肪体中AsToll5A表达量最高,AsToll1A表达量次之,其余Toll受体基因表达量极低。在球孢白僵菌和胡萝卜软腐欧文氏菌侵染过程中,与对照(注射PBS)比较,AsToll1A和AsToll5A在斯氏按蚊中的表达量显著升高,其余Toll受体基因表达变化不显著或降低。RNA干扰结果表明,AsToll1A或AsToll5A的表达受到抑制后,斯氏按蚊对球孢白僵菌的抵抗能力显著降低,肠道细菌总量与对照(dsGFP)比较显著增多。而且,抑制AsToll1A后抗菌肽基因DEF1和GAM1的表达受到显著抑制;抑制AsToll5A后仅有GAM1表达量下调。【结论】斯氏按蚊Toll受体在结构和功能上具有高度的保守性,其中AsToll1A和AsToll5A能响应病原真菌和革兰氏阴性细菌侵染并且影响肠道菌稳态。     

Analysis of the sporozoite ELISA for estimating infection rates in Mozambican anophelines

Comparisons were undertaken to investigate cost‐effective methods of implementing the enzyme‐linked immunosorbent assay (ELISA) for sporozoite determination in anophelines when large numbers require processing. Comparisons between ELISA plate reader and visual assessments were performed with Anopheles funestus and Anopheles gambiae s.l. (Diptera: Culicidae), as were comparisons between whole‐body mosquito samples, heads and thoraces, and abdomens alone. Rates obtained from pools of five or 10 mosquitoes were compared with those for individual mosquitoes, as were rates obtained using different sampling methods. A total of 41 792 An. funestus and 9431 An. gambiae s.l. collected in light traps, and 22 323 An. funestus and 6860 An. gambiae s.l. from exit collections were analysed. Visual assessments gave results similar to those of machine readings. Sporozoite rates were similar in both species, as were rates by collection method. The use of whole mosquitoes increased estimates of infection rate by 0.6%. Pool size did not affect infection rates of An. gambiae s.l., but rates were higher among individually tested An. funestus than among those tested in pools. For large‐scale surveys, the use of whole mosquitoes in pools of 10 mosquitoes, with correction for overestimation, and the noting of results according to a simple three‐stage visual assessment of positivity is the most cost‐effective approach and is sufficient to obtain reliable data for comparative purposes.     

Maturation of the tsetse fly Glossina pallidipes (Diptera: Glossinidae) in relation to trap-orientated behaviour

ABSTRACT The fat free dry weight or residual dry weight of the thorax (Trdw) increased linearly for the first 10 days of adult life in both sexes of G.pallidipes in the laboratory as their flight muscles developed. Using ovarian dissection to estimate the ages of nulliparous adult females of G.pallidipes , the Trdw was also found to increase linearly for at least 14 days in the field. Significant increases in pteridine fluorescence with age were measured in both laboratory-reared males and females of known chronological age and in wild-caught nulliparous females whose ages were estimated by ovarian dissection. A linear relationship existed between pteridine fluorescence and wing fray category for a wide range of ages of field-caught flies of both sexes. A stationary trap baited with ox odour was selective in that only the hungrier portion of the flies attracted to it actually entered. However, it was not selective in terms of the mean ages of flies caught. Comparisons were made of the age compositions of catches of both sexes of G.pallidipes attracted to a stationary trap baited with synthetic odours or to a mobile electrified net by plotting Trdw values against pteridine fluorescence. Nulliparous females were not attracted to the stationary trap, but were attracted to the mobile bait. Males of all ages appeared to be equally attracted to both. It is concluded that nulliparous females do not respond to host odour stimuli until they are ready to mate, perhaps relying on the energy-conserving strategy of watching for a moving host animal before attempting to feed. Alternatively, synthetic odours may differ from natural host odours in terms of their attractiveness to young females. Males, however, probably exhibit dual sexual and feeding behaviour by responding to an odour-baited stationary trap even when young.     

Comparative fecundity and associated factors for two sibling species of the Anopheles gambiaecomplex occurring sympatrically in The Gambia

Abstract. For two sibling species of mosquitoes belonging to the Anopheles gambiae complex of malaria vectors, the effects of body size (wing length) and bloodmeal size (haematin excretion) on fecundity of wild females were investigated in The Gambia, West Africa. Freshly blood-fed individuals from sympatric populations of An.arabiensis and An.gambiae sensu stricto were sampled by collection at 07.00–09.00 hours from within bednets during July/August 1993, at the beginning of the rainy season. The possible confounding effect of infection with Plasmodium parasites was removed by eliminating infected mosquitoes from the study samples. An.arabiensis females comprised 75% of the An.gambiae sensu law population and were significantly larger (greater mean wing length) than those of An.gambiae s.s. mosquitoes. Mean egg production per female (for the subsequent gonotrophic cycle, excluding pre-gravids) for the two species was not significantly different, though the relationship between wing length and egg production showed An.gambiae s.s. to be more fecund than the An.arabiensis of the same size. Pre-gravid An.gambiae s.s. had consumed significandy smaller bloodmeals than gravid females but the mean wing length of these two gonotrophic categories was not significantly different. In contrast, An.arabiensis pre-gravids were smaller and had consumed smaller bloodmeals than the gravids.     

Population genetic confirmation of species status of the malaria vectors Anopheles willmori and An.pseudowillmori in Thailand and chromosome phylogeny of the Maculatus group of mosquitoes

Among the Anopheles (Cellia) maculatus group of Oriental mosquitoes, positive assortative mating occurs within sympatric and synchronous populations of An.willmori and An.pseudowillmori in the presence of populations of An.maculatus and An.sawadwongporni, judged from the occurrence of inversion homozygotes and the absence of any heterozygotes in their distinctive, polytene chromosomes. Genotypic frequencies for enzyme electromorphs give additional evidence for the species status of An.pseudowillmori and a practical means of identification in field studies of malaria vectors. Autosomal rearrangements are referred to those of An.stephensi which is unique for 4y. An.willmori differs by a single inversion, 4x; An.pseudowillmori by three Arm 2 inversions; and An.dispar by one Arm 2 inversion and 4x. Fixed autosomal rearrangements in the Maculatus group are summarized and their phylogenetic distribution suggests some unknown, intrinsic mechanism by which genome structure is disrupted in association with speciation events. This could be relevant to the potential genetic manipulation of malaria vectors.     

Optimal life stage for radiation sterilization of Anopheles males and their fitness for release

Mating by male Anopheles mosquitoes (Diptera: Culicidae) was evaluated in the laboratory to assess fitness effects of radio-sterilization applied during different life stages of the malaria vectors An. stephensi Liston and An. gambiae Giles sensu stricto. After reproductive sterilization by gamma-irradiation (120 Gy), equal proportions of sterile and fertile (unirradiated) male adults were released into cages with virgin females and allowed to compete for matings. Radio-sterilization was applied when the males were pupae aged 0-7 h or 24-32 h, or adults aged <24 h or 24-55 h. After being radio-sterilized in the adult stage, males of both species competed effectively with unirradiated males, whereas those sterilized in the pupal stage obtained significantly fewer matings than unirradiated males from the same cohort. There was no evidence of females obtaining multiple inseminations. These findings emphasize the need to radio-sterilize males as adults in order to minimize the fitness cost. Such males may be intended for sterile insect technique population suppression or for trial releases of transgenic anophelines.     

Discriminative feeding behaviour of Anopheles gambiae s.s. on endemic plants in western Kenya

Anopheles gambiae Giles s.s. (Diptera: Culicidae) is known to feed on plant sugars, but this is the first experimental study to consider whether it discriminates between plant species. Thirteen perennial plant species were selected on the basis of their local availability within the vicinity of human dwellings and larval habitats of An. gambiae s.s. in western Kenya. Groups of 100 or 200 mosquitoes were released into cages either with a cutting of one plant type at a time (single-plant assay) or with cuttings of all 13 plants simultaneously (choice assay), respectively, and left overnight. In the choice assay, direct observations of the percentages of mosquitoes perching or feeding on each plant were recorded over four 1-h periods each night. For both types of assay, mosquitoes were recaptured and the percentage that had fed on plants was assessed by testing them individually for the presence of fructose. To identify which plants the choice-assay mosquitoes had fed on, gas chromatography (GC) profiles of samples of mosquito homogenates were compared with GC profiles of extracts from relevant parts of each plant. Four of the plants that were observed to have been fed on most frequently in the choice assay (Parthenium hysterophorus L., Tecoma stans L., Ricinus communis L., and Senna didymobotrya Fresen) were also shown to have been ingested most often by mosquitoes in both types of assay, suggesting that An. gambiae is differentially responsive to this range of plants, regardless of whether the plants were presented singly or mixed together. Significantly more females than males fed on plants, with the exception of P. hysterophorus L., one of the plants most frequently fed on. For most plant species (ten of 13), GC profiles indicated that An. gambiae obtained sugars primarily from flowers. The exceptions were P. hysterophorus L., Lantana camara L. and R. communis L., on which An. gambiae fed more often from leaves and stems than from flowers.     

The effect of repellents Ocimum forskolei and deet on the response of Anopheles stephensi to host odours

The behavioural response of Anopheles stephensi Liston (Diptera: Culicidae) to incubated host odours (from human and goat) and to human odour in combination with a repellent plant, Ocimum forskolei (Labiatae), or deet (N, N, diethyl-toluamide) (20%) was tested in a dual-port olfactometer. An. stephensi was significantly attracted to both host odours compared with air alone, but showed no preference when given a choice between both host odours simultaneously. In choice tests, the addition of deet to human odour did not significantly divert mosquitoes to human odour alone, but did divert them to goat odour. O. forskolei combined with human odour diverted mosquitoes to goat or human odour alone. Combinations of human odour and O. forskolei, and human odour and deet were both as unattractive as air alone, and attracted mosquitoes equally when offered simultaneously. The results indicate that use of O. forskolei as a repellent would be beneficial in reducing vector biting if used in communities in areas with partially zoophilic mosquito species such as An. stephensi, and where animals are present.     

Feeding frequency and survival of Anopheles gambiae in a rice-growing area in Ghana

Mortality rates, determined by dissection, of predominantly M form female Anopheles gambiae (Diptera: Culicidae) were estimated. Mosquitoes were collected in tent traps and light traps in an irrigation project village in Ghana in June and July 2010, when much of the area was flooded. Both M and S form larvae were collected from rice fields (74 of 80 specimens were M form). Adults were collected in equal proportions from the two traps (90 of 107 specimens from the light trap and 106 of 116 specimens from the tent trap were M form). During the study, collection numbers rose from 105 to 972 per night. A total of 1787 of the 15 431 An. gambiae collected were dissected. Of these, 953 (53%) were found to have taken their first bloodmeal, either as virgins or following mating. The age profiles of mosquitoes collected alive and dead, respectively, were similar. Eighteen of 2933 (0.61 ± 0.49%) specimens were found to be positive for sporozoites in an enzyme-linked immunosorbent assay (ELISA). Lagged cross correlations among the different age groups implied that the mosquitoes fed on days 2 and 4 following emergence prior to oviposition and every 2.65 ± 0.17 days thereafter. The best model to describe the observed population patterns implied a daily mortality of 84%. The results are discussed in relation to possible mosquito control measures for the village.     

P elements are found in the genomes of nematoceran insects of the genus Anopheles

We report the identification of genomic sequences in various anopheline mosquitoes (family Culicidae: suborder Nematocera: order Diptera) showing homology to the class II, short inverted-terminal-repeat (ITR) transposable element P from Drosophila melanogaster (family Drosophilidae; suborder Brachycera: order Diptera). Anopheles gambiae appears to have at least six distinct P elements. Other anopheline species, including four additional members of the An. gambiae species complex (An. arabiensis, An. merus, An. melas and An. quadriannulatus), Anopheles stephensi (all subgenus Cellia), An. quadrimaculatus (subgenus Anopheles) and Anopheles albimanus (subgenus Nyssorhynchus) also possess P elements similar to those found in An. gambiae. Ten distinct P element types were identified in the genus Anopheles. At least two of the An. gambiae elements appears to be intact and potentially functional. Phylogenetic analysis of the anopheline P elements reveals them to belong to a distinctly different clade from the brachyceran P elements.     

Movement of Anopheles gambiae s.l. malaria vectors between villages in The Gambia

ovement of mosquitoes belonging to the Anopheles gambiae complex (mixed wild populations of An.arabiensis, An.gambiae and An.melas ) between three neighbouring rural villages in The Gambia was investigated by mark-release-recapture. A total of 12,872 mosquitoes were collected in bednets, marked with a magenta fluorescent powder and released over a 15-day period in one of the villages. A further 15,507 mosquitoes were collected in exit traps, marked with a yellow powder and released over the same period. Mosquitoes were captured daily in all three villages using pyrethrum spray catches, as well as bednet and exit trap catches. The catching period extended for 6 days after the last day of release.
Of the mosquitoes released, 372 (1.3%) were recaptured 2–21 days later. Of these recaptures, 272 were caught in the release village, and 98 were caught in other villages situated 1–1.4 km away. The 'movement index' between villages was calculated as 17.2% (12.2–22.4% confidence limits) for mosquitoes released after feeding and 20.1% (14.7–25.3%) for those released unfed.
These results suggest that movement of mosquitoes between neighbouring villages in The Gambia seriously affects the entomological evaluation of pyrethroid-impregnated bednet programmes in areas where treated and untreated villages are interspersed.     

Unexpected anthropophagic behaviour in Anopheles quadriannulatus

The strongly anthropophilic behaviour of Anopheles gambiae Giles sensu stricto (Diptera: Culicidae), the most important malaria vector in Africa, has been demonstrated by field and laboratory studies. Other members of the An. gambiae complex express varied degrees of anthropophily. Anopheles quadriannulatus (Theobald) species A and B are more zoophilic members of the complex and hence are considered to be of no medical importance. Olfactometer experiments with An. quadriannulatus species A have demonstrated attraction to both human and cow odour. To extend these olfactometer observations a choice experiment was conducted in an outdoor cage with a human and a calf as baits, using laboratory-reared mosquitoes. Anopheles gambiae s.s. (from Liberia) and two strains of An. quadriannulatus species A (SKUQUA from South Africa, SANGQUA from Zimbabwe), marked with different coloured fluorescent powders for identification purposes, were released simultaneously and given an equal opportunity to feed on either host. The experiment was repeated six times. Bloodmeals were identified using the precipitin technique. Anopheles gambiae s.s. showed highly anthropophagic behaviour, taking 88% of bloodmeals from the human host. In contrast, both strains of An. quadriannulatus fed with equal frequency on the human or the calf; the response to either host was not significantly different. These results confirm the olfactometer findings and demonstrate anthropophagic behaviour not previously recorded in this species. This finding has implications for prospective manipulation of host preference for genetic control purposes.     

Feeding and survival of the malaria vector Anopheles gambiae on plants growing in Kenya

The propensity of the malaria vector mosquito Anopheles gambiae Giles (Diptera: Culicidae) to ingest sugars from various plants, and subsequent survival rates, were assessed with laboratory-reared males and females offered eight species of plants commonly cultivated and/or growing wild in western Kenya. In cages (no-choice bioassay), mosquitoes given the opportunity to feed on castorbean (Ricinus communis L.) had the longest survival times (mean and median survival time of 6.99 +/- 0.23 and 5.67 +/- 0.17 days, respectively), comparable to mosquitoes given 6% glucose (mean and median survival time of 8.70 +/- 0.23 and 6.67 +/- 0.33 days, respectively). Survival rates of An. gambiae were low on the other plants, comparable to mosquitoes given only water. Three plants: sweet potato (Ipomoea batatas L.), wild sage (Lantana camara L.) and castorbean provided levels of sugar ingestion by both sexes of An. gambiae detectable using the cold anthrone method, showing a positive correlation between median survival and sugar consumption (Spearman rank correlation coefficient = 0.905, P < 0.0001). Equal numbers of males and females were released in an enclosed semi-field screenhouse system containing a range of local plants, but no host for blood, and allowed to feed ad libitum: 6.7 +/- 0.5% (11/64) of those recaptured were found to contain detectable fructose (all females). Common plants are clearly a viable source of nutrition for adult female An. gambiae, as well as males, and may constitute and important resource for this important malaria vector.