Influence of Larval Density or Food Variation on the Geometry Of

7/28/2019 Influence of Larval Density or Food Variation on the Geometry Of

1/7

Influence of larval density or food variation on the geometry of

the wing ofAedes (Stegomyia) aegypti

N. Jirakanjanakit1, S. Leemingsawat2, S. Thongrungkiat2, C. Apiwathnasorn2, S. Singhaniyom3, C. Bellec4 and

J. P. Dujardin5

1 Center for Vaccine Development, Institute of Science and Technology for Research and Development, Mahidol University, Salaya,Nakhonpathom, Thailand

2 Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand3 Department of Biostatistics, Faculty of Public Health, Mahidol University, Bangkok, Thailand4 Institut de Recherche pour le Developpement, Montpellier, France5 Institut de Recherche pour le Developpement, Center of Excellence for Vectors and Vector borne Diseases, Mahidol University,

Bangkok, Thailand

Summary background and method Variation in wing length among natural populations of Aedes (Stegomyia)

aegypti (L.) (Diptera: Culicidae) is associated with different vectorial capacities. Geometricmorphometrics allowed us to use a more powerful estimator of wing size (centroid size), as well as to

visualize the variation of wing shape, to describe the effects of density or food variation at larval stage on

20 anatomical landmarks of the wing of A. aegypti.

results Almost perfect correlations between (centroid) size and larval density or size and larval food

were observed in both sexes: a negative correlation with increasing density and a positive one with

increasing amount of food. The allometric component of shape change was always highly significant, with

stronger contribution of size to shape under food effects. Within each experiment, either food or density

effects, and excluding extreme conditions, allometric trends were similar among replicates and sexes.

However, they differed between the two experiments, suggesting different axes of wing growth.

conclusion Aedes aegypti size is highly sensible to food concentration or population density acting at

larval stages. As larger individuals could be better vectors, and because of the stronger effect of food

concentration on size, vector control activities should pay more attention in eliminating containers with

rich organic matter. Furthermore, as a simple reduction in larval density could significantly increase thesize of the survivors, turning them into potentially better vectors, the control activities should try to

obtain a complete elimination of the domestic populations.

keywords Aedes aegypti, food, density, allometry, wing geometry

Introduction

The environment for Aedes (Stegomyia) aegypti (L.)

proliferation includes water-filled containers for immatures

(Christophers 1960), nectar and blood as energy source foradults and egg development, and shady habitats for resting

and oviposition (Clements 1992). Habitat characteristics

may affect the suitability of containers as breeding sites for

A. aegypti (Vezzani & Schweigmann 2002). In addition to

temperature, two of the most important factors influencing

habitat quality are food and density (Clements 1992).

Deficiency in food is expected to produce a smaller size in

adult. Under similar food conditions, size could be

inversely affected by population density. These predictions

were verified for A. aegypti (Dye 1984; Clements 1992;

Russell 1998) and other mosquitoes (Gorla et al. 1992;

Renchaw et al. 1993; Lord 1998; Gleiser et al. 2000).

The body size of the mosquitoes reveals many bionomicfactors such as their survival, their vector competence, and

their response to repellents and insecticides (Landry et al.

1988; Xue et al. 1995; Sumanochitrapon et al. 1998).

Bigger insects consume larger blood meals, affecting their

fecundity and longevity (Nasci 1986; Briegel 1990; Nasci

& Michell 1994). Large mosquitoes have greater reserves

than small ones, and this might induce a different feeding

behaviour before oviposition (Naksathit et al. 1999). The

Tropical Medicine and International Health doi:10.1111/j.1365-3156.2007.01919.x

volume 12 no 11 pp 13541360 november 2007

1354 2007 Blackwell Publishing Ltd


2/7

response to insecticide also appears to be influenced by

body size, as the bigger mosquitoes may be less repelled by

N,N-diethyl-m-toluamide (DEET) (Xue et al. 1995; Xue &

Bernard 1996). It then appears necessary to better under-

stand the natural causes of size changes, and their effect onshape, if any.

Direct measurement of a mosquito body is not a

satisfactory estimation of size because of the hunch shape

of the insect and variation in dryness of the abdomen.

Weight might be a good estimator of size, but it could

differ greatly depending on blood feeding, gravidity or

other circumstances, such as sugar or water provided. A

linear measurement of wing length is frequently used as an

estimator of global body size in mosquitoes (Lounibos

1994; Lehmann et al. 2006). We used the centroid size

(CS) as defined in geometric morphometrics to estimate the

global size (Bookstein 1991): it presents the advantage to

be sensible to various directions of change, reflectingmodifications in either the longitudinal, oblique, or lateral

directions.

Geometric morphometrics is a powerful and cheap

characterizing tool for many organisms, including medi-

cally important insects (Dujardin & Slice 2007). So far, it

has been successfully applied to natural populations of

sand flies, the vectors of leishmaniasis (Dujardin et al.

2002); triatomines, the vectors of Chagas disease (Villegas

et al. 2002; Feliciangeli et al. 2007; Dujardin et al. 2007);

and tsetse flies, the vectors of sleeping disease (Camara

et al. 2006). In A. aegypti, geometric morphometrics can

discriminate different laboratory strains (Jirakanjanakit &

Dujardin 2005).However, characterizing and discriminating are

descriptive tasks, not contemplating the underlying bio-

logical mechanisms. Geometric morphometrics allows us

to decompose the metric variation into size and shape, as

well as to visualize the shape changes. Are these features

equally affected by environmental changes? Is the size of

the adult modified when larval density drops? What shape

modification can we expect to see in case of such an

environmental perturbation? Here we show for A. aegypti

the accuracy of geometric morphometrics in detecting size

and shape changes in response to larval density and food

supply. We show that the geometric variation is signifi-

cantly affected by size variation, and we detail the locationon the wing of allometric shape adjustment.

Materials and methods

Mosquitoes

Aedes aegypti larvae were collected in October 2004 from

Chanthaburi province, located in the east of Thailand.

Approximately 200 founders were reared in the insectary

at 2528 C and 5060% relative humidity (RH). Larvae

were fed with dog food (Alpo) and adults were provided

with 10% sugar solution. Mosquitoes were also allowed to

feed on Swiss mice twice a week. After the blood feed,mosquitoes were allowed to lay eggs into a small cup lined

with paper and half filled with water. The same batch of

eggs from the fifth generation was used for all tests. Each

replicate test of both experiments was performed from the

hatched larvae of the same tray.

Density experiment

First-stage larvae were raised at varying densities of 100,

200, 300, 400, and 500 larvae in plastic trays of the same

size filled with 2 l of water and covered with nylon mesh.

Excess food was given twice daily to avoid the effect of

starvation. Pupae were transferred to 30 30 cm cages toallow adult eclosion. One replicate procedure was per-

formed from the same generation of mosquitoes of the

same source.

Food experiment

The food experiment used always the same density of

larvae: 200 first-stage larvae in plastic trays of the same

size, filled with 2 l of water and covered with nylon mesh.

They were provided daily with 0.1, 0.2, 0.3, and 0.4 g of

food (dog food, Alpo). One replicate procedure was

performed in the same manner from the same generation of

mosquitoes of the same source.

Samples preparation and data collection

Mosquito wings were detached from the thorax, placed on

a clean microscopic slide, and then secured with Euparal

under the cover slip. The slides were positioned on the

phase contrast microscope with a 4X lens. A digital camera

(4 mega pixels) was used to capture the wing images. A set

of 20 landmarks (Figure 1) covering most of the wing

surface was selected and digitized using TPSdig software

(http://life.bio. sunysb.edumoph).

Size and shape

The mean and variance of CS, i.e. the square root of the

sum of squared distances of a set of landmarks from their

centroid, were compared using non-parametric, permuta-

tion methods. The mean value and standard deviation of

each group was plotted onto food concentration

(Figure 2a) and density (Figure 2b) values, and correlation

coefficients were computed for each replicate.

Tropical Medicine and International Health volume 12 no 11 pp 13541360 november 2007

N. Jirakanjanakit et al. Geometry of the wing ofAedes (Stegomyia) aegypti

2007 Blackwell Publishing Ltd 1355


3/7

The Generalized Procrustes Analysis (Rohlf 1990) was

used to produce shape variables (i.e. the non-uniform and

the uniform components of shape; partial warps or shapevariables are used here to indicate both these compo-

nents). Shape variation along microenvironmental clines

was explored by principal component analysis (producing

the so-called relative warps).

The residual relationship between shape and size vari-

ables was explored by multivariate regression and permu-

tation test procedure for statistical significance (Good

2000). An estimation of the contribution of size variation

to shape differences among groups was obtained after

linear regression of the first canonical factor (derived from

shape variation) against size variation.

Was the relationship of shape with size similar among

groups? To test for a common allometric model, amultivariate analysis of covariance (mancova) was con-

ducted mixing all the groups of one replicate, or all of

them except the groups reared in extreme conditions.

Statistical significance was obtained by the Wilks statistics

(Table 1).

Did the shape change in a similar way when driven by

food or by density variation? To answer this question, we

used the two-state multivariate phenotypic change

(TSMPC) analysis as described by Collyer and Adams

(2007). In this latter analysis, non-parametric procedure

tests for the significance of shape change in terms of

intensity (Euclidian distances between states), and orien-

tation (the angle between these distances). The analyseswere performed excluding groups at the extreme levels of

food or density range because of their possible distorting

effect on the common allometric trend (see Results). The

shape change was examined in the direction of size

increase. Thus, the change from the 0.2 g to 0.3 g

groups of the food experiment was compared with the

change observed between the 300 and 200 groups of the

density experiment.

Shape changes were visualized by deformation grids and

vectors describing landmark displacements magnified 10

times (Figure 3). For all these analyses, as sexual sizedimorphism is well known in A. aegypti, males and females

were considered separately.

Software

TPSdig was used to digitize the images (Rohlf 2003).

Procrustes and statistical analyses were performed using

various modules that we had developed (http://

www.mpl.ird.fr/morphometrics): (i) VAR to compare

means and variances (module developed in collaboration

with H. Caro-Riano); (ii) MOG to produce the shape

variables (the partial warps, including affine and non-

affine components of shape); (iii) PAD to produce canon-ical factors and perform regression analyses; and (iv) COV

to compute and test Euclidian distances among groups

based on relative warps (the principal components of

partial warps), to perform multivariate regression of shape

on size, to test for a common allometric model (mancova)

and to perform the TSMPC analyses of Collyer and Adams

(2007). Finally, TPSregr (Rohlf 2003) was used to produce

for each sex deforming grids associated with shape changes

in each experiment.

Results

Centroid size

The correlations between CS and density values or food

concentrations were almost perfect in both sexes for each

replicate. These effects were illustrated mixing both repli-

cates of each experiment (Figure 2a,b). Size correlated

negatively with larval density values: females, replicate 1,

R2 = 0.92 (P = 0.010) and replicate 2, R2 = 0.86

(P = 0.020); males, replicate 1, R2 = 0.97 (P = 0.002) and

1

16 14

13

17 18

15

19

8

9

10

12

20

11

7

65

4

32

Figure 1 Landmarks on female Aedesaegypti mosquito wing. The central area ofthe wing is characterized by eight land-

marks (landmarks 1219). The posterior

border is represented by seven landmarks

(from 5 to 11). These two sets of landmarks

showed different changes to external

conditions (see Figure 3).





4/7

replicate 2, R2 = 0.79 (P = 0.040). Size was positively

correlated with the amount of food: females, replicate 1,

R2 = 0.95 (P = 0.020) and replicate 2, R2 = 0.94

(P = 0.020); males, replicate 1, R2 = 0.97 (P = 0.010) and

replicate 2, R2 = 0.96 (P = 0.020). In most cases, pair-wise

comparisons of size were significant (after Bonferronis

correction) between varying conditions of density (3140)

or food concentration (2224), for both males and females

(detailed results not shown).

Variances of size at each density or at each food

concentration were similar except one of each condition inmale replicate 2 (200 vs. 300 density and 0.3 g vs. 0.4 g

of food; detailed results not shown).

Shape

Change of shape according to density and food was

observed at different sets of landmarks, one corresponding

to the central area of the wing, and another corresponding

to the posterior margin of the wing (Figures 1 and 3). The

first set of landmarks showed similar directions of changes

with size in both sexes whatever the effect, food or density.

These changes seemed visually stronger for food effect, a

subjective observation which was not confirmed by theTSMPC analysis. The other set of landmarks (the ones

located along the posterior margin) showed opposite

directions of change according to the environmental

variable. This was fully confirmed by the quantitative

analysis (TSMPC).

Allometry

Size and shape correlated significantly in each experiment

(P < 0.001). Significant contributions of size to shape were

found at various levels according to the experiments and

replicates. In the experiment on density, the residual

allometries on the first canonical factor ranged between6% and 14% for females, 2% and 25% for males,

according to replicates. For different food concentrations,

residual allometries on the first canonical factor were as

high as 39% and 18% for females and 36% and 35% for

males, according to replicates.

Without the extreme conditions (lowesthighest density

values or food concentrations), similar directions (common

slope) of allometries were observed in both sexes, except

(a)

(b)

1076.88

927.58

1396.29

1205.77

1075.95

984.81

1452.41

1295.12

100 200 300 400 500

0.1g 0.4gLarval_food_Males

0.1g

100 200 300 400 500

0.4gLarval_food_Females

Larval_densities_Males

Larval_densities_Females

Figure 2 (a) Correlation4 of centroid sizes (vertical axis) and

amount of food in males (top) and females (bottom) of Aedesaegypti. Both replicates were mixed. Vertical lines are standarddeviations. (b) Correlation of centroid sizes (vertical axis) and

density in males (top) and females (bottom) of A. aegypti. Bothreplicates were mixed. Vertical lines are standard deviations.





5/7

for one replicate (replicate 2, Table 1). The most perturb-

ing extreme conditions on allometric trends seemed to bethose with the least food and the lowest density (Table 1).

Two-state multivariate phenotypic change analyses

The interaction between subgroup effect (increasing size

from 0.2 g to 0.3 g food, or from 300 to 200

densities) and group effect (the causes of size change,

either food or density) was always significant after Wilks

test (from P < 0.0001 to P < 0.0070). The intensity of

shape changes from one environment to another did not

differ between food and density experiments (except for

females in the replicate 1), while the direction of shape was

always statistically different (P < 0.0140 to P < 0.0001).This was visualized by the opposite directions of shape

changes at the landmarks delimiting the posterior margin

of the wing (Figure 3).

Discussion

As long as commercial vaccine is not available, it is

admitted that reduction of Aedes population is the only

way to prevent dengue virus transmission (Gubler 2002).

Size and weight of adult mosquitoes are supposed toprovide information on their fitness and their effectiveness

as a vector (Briegel 1990; Nasci & Michell 1994; Suma-

nochitrapon et al. 1998). If this relationship is true, and

according to our data, incomplete control procedures that

reduce the density of larvae in individual containers should

produce larger insects and could aggravate dengue trans-

mission. This agrees with the abundance of A. aegypti in

the endemicepidemic areas which are not always related

to dengue incidence rates (Kuno 1997). On the other hand,

more attention should be paid to containers enriched with

organic matters, such as flower pots, water supplies for

domestic animals, and so on. According to our data, such

containers would indeed produce larger individuals.As far as we know, the present study is the first report on

experiments exploring the environmental effect on wing

shape and allometric traits ofA. aegypti. We found that the

changes in shape as a result of density or food variation,

although not completely similar, were mainly driven by

allometric effects. The central part of the wing showed

similar variation with size whatever the cause of size

change, either food or density variation, but a different

Table 1 Analysis of allometry, and tests

for a common slope model of allometry

among groups submitted to different

conditions of larval food supply or larval

densityExperiments

Density variation Food variation

Allometry

Common

slope Allometry

Common

slope

Female R1

All conditions 0.0000* 0.0006* 0.0000* 0.0061*

Without extreme conditions 0.0000* 0.1176 0.0000* 0.1811

Without highest condition 0.0000* 0.0027* 0.0000* 0.0452

Without lowest condition 0.0000* 0.0488 0.0000* 0.0699

Female R2

All conditions 0.0000* 0.0000* 0.0000* 0.0000*

Without extreme conditions 0.0000* 0.0000* 0.0000* 0.0000*

Without highest condition 0.0000* 0.0000* 0.0000* 0.0000*

Without lowest condition 0.0000* 0.0000* 0.0000* 0.0000*

Male R1

All conditions 0.0000* 0.0000* 0.0000* 0.0031*


Without highest condition 0.0000* 0.0017* 0.0000* 0.0044

Without lowest condition 0.0000* 0.0096 0.0000* 0.0134Male R2

All conditions 0.0000* 0.0157 0.0000* 0.1110


Without highest condition 0.0000* 0.0288 0.0000* 0.0625

Without lowest condition 0.0000* 0.0357 0.0000* 0.7150

For densities, all conditions means we compared densities 100, 200, 300, 400, and

500, while without extreme conditions means we compared only densities 200, 300,

and 400. For food concentrations, all conditions means we compared food concentra-

tions 0.1 g, 0.2 g, 0.3 g, and 0.4 g, while without extreme conditions refers to

comparison of 0.2 g and 0.3 g only. R1, replicate 1; R2, replicate 2. Asterisks indicate

significance (P < 0.05) after Bonferronis correction.





6/7

behaviour was apparent for the posterior border of the

wing (Figure 3). Besides, the common allometric model

was not verified when extreme conditions were included in

the sample, either very low food supply, very low densities,

very high food supply, or very high densities.

These data provide first clues to understand the possible

metric variation of A. aegypti among natural populations.

They indicate that environmentally induced changes

primarily affect the size of the insect, and that this change

has a predictable direction. Our data also indicate thatlarval food and density may influence the shape of the

wing, and that this shape adjustment contains a significant

amount of allometric effect. In other circumstances shape

variation is sometimes completely free of allometric

content (Dujardin & Slice 2007). Such findings of signifi-

cant shape changes without corresponding size variation

would probably not be related to local conditions of food

and densities, but rather to genetic differences.

Our data also indicate that different causes of size

variation could affect shape in a different way: the central

part and the posterior margin of the wing follow more or

less the same direction of landmark displacement under

food variation influence, while they follow differentdirections under density variation, suggesting different axes

of wing growth. Such differences could correspond to slight

genetic variation among experimental groups, although

there was no detectable difference between replicates, or

possible chemical modification of the water at high larval

density (Clements 1992).

As the phenotypic development of A. aegypti seems

to influence its vectorial capacity, we believe that it is

important to understand our own tools to evaluate

phenotypic changes. The present laboratory experi-

ments represent the first step in this direction. As a

first indication, they suggest that it might be danger-

ous to just reduce the vector population density, andthat it is important to eliminate waters with organic

material.

Acknowledgements

The authors thank Dr Sutee Yoksan, Center for Vaccine

Development, Mahidol University, Thailand and Dr Jean-

Paul Gonzalez, IRD Unit 178, Faculty of Sciences, Mahidol

University, Thailand, for all their support on this project.

They also thank Napaporn Kuatrakool and Sadanun

Boonsatien for their help in mosquito rearing and wing

slides preparation. This research work was supported by

Faculty of Graduate Studies, Mahidol University, academicyear 2006.

References

Bookstein FL (1991) Morphometric Tools for Landmark Data:

Geometry and Biology. Cambridge University Press, Cam-

bridge, 435 pp.

Briegel H (1990) Metabolic relationship between female body size,

reserves and fecundity of Aedes aegypti. Journal of Insect

Physiology 36, 165172.

Camara M, Caro-Riano H, Ravel S et al. (2006) Genetic and

morphometric evidence for isolation of a tsetse (Diptera: Glos-

sinidae) population (Loos islands, Guinea). Journal of Medical

Entomology 43, 853860.

Christophers R (1960) Aedes aegypti (L.), the Yellow Fever

Mosquito: Its Life History, Bionomics and Structure. Cam-

bridge University Press, Cambridge.

Clements AN (1992) The Biology of Mosquitoes, 1. Chapman and

Hall, London, UK.

Collyer ML & Adams DC (2007) Analysis of two-state multi-

variate phenotypic change in ecological studies. Ecology 88,

683692.

DensityF (500->100)

DensityM (500->100)

Food

F (0.1g->0.4g)

Food

M (0.1g->0.4g)

Figure 3 Shape changes at each landmark, magnified 10 times, in

relation to density (two top wings) and food (two bottom wings)

variation. Each graph of Table 1 was derived from the pooled

replicates of each experiment, as each replicate had the same

profile (not shown). Arrows indicate the direction of each land-

mark displacement along the increasing size gradient obtained

with decreasing densities (see density, 500 -> 100, top) or withincreasing concentrations of food (see food, 0.1 g -> 0.4 g, bot-

tom). F, females; M, males.





7/7

Dujardin JP & Slice D (2007) Geometric morphometrics. Contri-

butions to medical entomology. In: Encyclopedia of Infectious

Diseases. Modern Methodologies, Chap. 25 (ed. M Tibayrenc)

Wiley, 435447.

Dujardin JP, Le Pont F & Baylac M (2002) Geographic versusinterspecific differentiation of sandflies: a landmark data anal-

ysis. Bulletin of Entomological Research 93, 8790.

Dujardin JP, Beard B & Rykman R (2007) The relevance of wing

geometry in entomological surveillance of Triatominae. Infec-

tion, Genetics and Evolution 7, 161167.

Dye C (1984) Competition among larval Aedes aegypti: the role of

interference. Ecological Entomology 9, 355357.

Feliciangeli MD, Sanchez-Martin M, Marrero R, Davies C &

Dujardin JP (2007) Morphometric evidence for a possible role of

Rhodnius prolixus from palm trees in house re-infestation in the

State of Barinas (Venezuela). Acta Tropica 101, 169177.

Gleiser RM, Urrutia J & Gorla DE (2000) Body size variation of

the floodwater mosquito Aedes albifasciatus in Central Argen-

tina. Medicine and Veterinary Entomology 14, 3843.

Good P (2000) Permutation Tests: A Practical Guide to Re-sam-

pling Methods for Testing Hypotheses. Springer, New York

Gorla DE, Luduena Almeida FF & Serra G (1992) Effect of food

competition on Culex pipiens quinquefasciatus under laboratory

conditions. Ecologa Austral 2, 5761.

Gubler DJ (2002) Epidemic denguedengue hemorrhagic fever as a

public health, social and economic problem in the 21st century.

Trends in Microbiology 10, 100103.

Jirakanjanakit N & Dujardin JP (2005) Discrimination of Aedes

aegypti (Diptera: Culicidae) laboratory lines based on wing

geometry. Southeast Asian Journal of Tropical Medicine and

Public Health 36, 858861.

Kuno G (1997) Factors influencing the transmission of dengue

viruses. In: Dengue and Dengue Hemorrhagic Fever (eds DJ

Gubler & G Kuno) CAB International University Press, Cam-

bridge, UK.

Landry SV, De Foliart GR & Hogg DB (1988) Adult body size and

survivorship in the field population ofAedes triseriatus. Journal

of American Mosquito Control Association 4, 121128.

Lehmann T, Dalton R, Kim EH et al. (2006) Genetic contribution

to variation in larval development time, adult size, and longevity

of starved adults of Anopheles gambiae. Infection Genetic and

Evolution 6, 410416.

Lord CC (1998) Density dependent in larval Aedes albopictus

(Diptera: Culicidae). Journal of Medical Entomology 35, 825

829.

Lounibos LP (1994) Geographical and developmental components

of adult size of neotropical Anopheles (Nyssorhynchus). Eco-

logical Entomology 19, 138146.

Naksathit AT, Edman JD & Scott TW (1999) Partitioning of

glycogen, lipid, and sugar in ovaries and body remnants of

female Aedes aegypti (Diptera: Culicidae) fed human blood.

Journal of Medical Entomology 36, 1822.

Nasci RS (1986) The size of emerging and host seeking Aedesaegypti and the relationship of size to blood feeding success in

the field. Journal of the American Mosquito Control Assococi-

ation 2, 6162.

Nasci RS & Michell CJ (1994) Larval diet, adult size and sus-

ceptibility of Aedes aegypti (Diptera: Culicidae) to infection

with Ross River virus. Journal of Medical Entomology 31, 123

126.

Renchaw M, Service MW & Birley MH (1993) Density-dependent

regulation of Aedes cantans (Diptera: Culicidae) in natural and

artificial populations. Ecological Entomology 18, 223233.

Rohlf FJ (1990) Rotational fit (Procrustes) methods. In: Proceed-

ings of the Michigan Morphometrics Workshop. Special Publi-

cation Number 2 (eds FJ Rohlf & FL Bookstein) The University

of Michigan Museums, Ann Arbor, MI, 380 pp., pp. 227236.

Rohlf FJ (2003) TpsDig version 1.34 and TpsRegs version 1.27.

Available at: http://morph.bio.sunysb.edu./morph/index/

html.Departement of Ecology and Evolution, State University of

New York.

Russell RC (1998) Larval competition between the introduced

vector of dengue fever in Australia, Aedes-aegypti (L), and a

native container-breeding mosquito, Aedes notoscriptus (Skuse)

(Diptera, Culicidae). Australian Journal of Zoology 34, 527

534.

Sumanochitrapon W, Strickman D, Sithiprasasna R, Kittayapong

P & Innis B (1998) Effect of size and geographic origin ofAedes

aegypti on oral infection with dengue-2 virus. American Journal

of Tropical Medicine Hygiene 58, 283286.

Vezzani D & Schweigmann N (2002) Suitability of containers

from different sources as breeding sites of Aedes aegypti (L.) in a

cemetery of Buenos Aires City, Argentina. Memorias do Insti-

tuto Oswaldo Cruz 97, 789792.

Villegas J, Feliciangeli MD & Dujardin JP (2002) Wing shape

divergence between Rhodnius prolixus from Cojedes (Venezu-

ela) and R. robustus from Merida (Venezuela). Infection,

Genetics and Evolution 2, 121128.

Xue RD & Bernard DR (1996) Human host avidity in Aedes

albopictus: influence of body size, parity and time of day.

Journal of American Mosquito Control Association 12, 58

63.

Xue RD, Bernard DR & Schreck CE (1995) Influence of body size

and age ofAedes albopictus on human host attack rate and the

repellency ofDEET. Journal of the American Mosquito Control

Association 11, 5053.

Corresponding Author J. P. Dujardin, Institut de Recherche pour le Developpement (UMR IRD-CNRS 2724), Center of Excellence

for Vectors and Vector borne Diseases (CVVD), Faculty of Sciences, Mahidol University, Bangkok, Thailand. Tel./Fax: +66 224410227

E-mail: [email protected]




Documents

Influence of Larval Density or Food Variation on the Geometry Of