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Preliminary field observations on the flight speed of a phlebotomine sandfly
138 TRANSACTIONS OF THE ROYAL SOCIETY OF TROPICAL MEDICINE
Preliminary R.
field observations
AND HYGIENE (1986) 80, 138-142
on the flight sandfly
T. J. WILKES, M. BAILLY, of Pure and Applied Biology, Imperial
KILLICK-KENDRICK*,
Department
speed of a phlebotomine I. BAILLY AND L. A. RIGHTON College,
London
SW7 4AZ
Abstract
From observationswith a portablewind tunnel usedin the field in southernFrance, it is estimated that the maximumflight speedof Phlebowmus ariasi is in the range0.65-0.70m/set(2.3 to 2.5 km/h).
KENDRICK et al. (1984).
by a cloth sleeve to a tent containing two people (Fig. 1). Nine fans at the back of the tunnel sucked host-conditioned air from the tent and blew it down the tunnel (Fig. 2). Wild hungry female sandflies were attracted up the odour plume and entered the tunnel seeking the source. On meeting the electric grid, they were killed (Fig. 3). By varying the air speed in the tunnel, an estimate was made of the maximum speed of air against which the flies could fly and, thus, of the maximum flight speed of the flies. In nine experiments lasting 20 min, and one of 15 rnin, the air speeds were varied from 0.35 (two ex eriments 0.40 (one), 0.50, (four), 0.60 (one) to 0.70 (two f misec. Ae air speeds were measured with a DISA type 54N50Low Velocity Flow Analyzer placed in front of the centre of the grid. The air speed on the left side, when looking up the tunnel, was about 12% slower than that at the centre whereas that on the right side was about 12% faster. The electrocuted flies were in excellent condition with only minor damage to the legs and wings. None was charred, and they were easy to dissect. Samples of female sax&lies were identified by their spermathecae as P. ariasi. It is confidently assumed that all sandties were the same because other species of Phlebotonws known to be present (P. pemiciosus and P. mascittii) are apparently in very low densities and are seldom encountered in the valley where the work was done. A Vent Axia fan trap (KILLICK-KENDRICK et al., 1985) was set up in the host-conditioned air 5 m in front of the tunnel to monitor the numbers of ilies responding to the odour during the period of each experiment (Fig. 4). The numbers of female sandflies electrocuted in the tunnel were then expressed as a percentage of the total carch (from the
with the prevailing nocturnal wind. The tunnel was attached
*MRC External Scientific Staff
Introduction
In mark-release-recapture studieson the dispersal of Phlebowmus ariasi Tonnoir, 1921in the south of France, one female fly wasrecaptured 2.2 km in a direct line from the placeof release;it had movedthis distance in only 68.5 hours. A number of other femaleswere recapturedat distancesof about 1 km (KILLICK-KENDRICK et al., 1984). P. ariasi is the provenvector of Leishmania infanturn in the Cevennes focus (KILLICK-KENDRICK& RIOUX, 1981)and the movementof the flies wasconsideredasone way in which leishmaniasis could be spreadin that part of France and, possibly, in other foci. The questionarisesasto whether santies actively fly suchcomparativelylong distancesor whether the movement is assistedby wind as it is with many insects,includingseveralvectorssuchassomespecies of blackflies, mosquitoesand midges (PEDGLEY, 1983; SELLERS,1983).We therefore made preliminary observationson the flight speedof P. ariasi to find out if the distancesthe markedfliesmovedcould have been achievedby active flight alone. Materials
and Methods
TheworkwasdonefrommidJulyto midAugust,1984,in thecommune of Roquedur,department of Gard,France,in theCCvennes focusof visceralleishmaniasis. Descriptions of the placearegivenby RIOUX et al., (1979)andKILLICKA windtunnel(1 x 0.3 x 0.3 m) with an electrocuting grid(RIGHTON et al., 1985) was set up in an orchard in line
Table I-Numbers of female sandflies killed in a wind tunnel and caught in a Vent Axia fan trap 5 m in front of the tunnel with tunnel air speeds from 0.35 to 0.70 mkec; except where indicated, all experiments were run for 20 min
Tunnel air speed (mkec) o-35 o-35 * 0.40 E8 0.50 0.50 0.60 0.70 0.70
* 15 minute run.
No. of flies caught in fan trap
% of total catch killed
113 125 178
44 40 i:
72-O 75.8 68.2
47 2;
51 f:
1: 9 3
2;
56.0 37.8 41.6 33.0 26.3 14.1 11.1
N&$
E
tunnel
24
in tunnel
R.
Fig.
1. Wind
FIN 2. Wind
tunnel
tunnel
attached
showing
to a tent
containing
KII.LI(:K-KENDRICK
139
f?Z al.
two people.
set of 9 fans (F:, gauze filters
(G), electrocutmg
grid (E!, high voltage
unit CH) and 3 battery
pods pownng
fans !B!.
140
FLIGHT
tunnel and the fan trap). Comparisons could results obtained During each
on different
SPEED
OF
PHLEBOTOMINE
thus be made of
nights.
experiment, records were kept of the ambient temperature, relative humidity and wind speed and direc-
tion.
All observations
midnight.
were made between
22.30
hours and
Results
At external wind speedsof >05 msec very few flies were caught in the tunnel. However, when the wind speedwas<0.5 msecfor at leasthalf of the time of an experiment, the temperaturewas ~16°C and tunnelair speedswerelow, many sandfliesenteredthe tunnel and were killed on the electrocution grid. The numbers of female sandfliescaught in the tunnel and the fan trap in 10 experimentsat suitable temperaturesand wind speedsare shownin Table I. When the percentageof the lliescaughtin the tunnel (of the catchesin -me tunnel and the fan trap) are nlotted and a regressionline fitted (Fig. 5), the approximatemaximum Ilight speedof ‘the flies (i.e. the maximum speedof wind againstwhich any flies can fly) appearsto be about 0.75 m/set. However, tunnel air speedswere measuredat the centre of the grid but the fliesdetectedand generallyfavoured the
SANDFLIES
left sidewhere the speedwasabout 12%slowerthan at the ooint of measurement(Fix. 3). If this is taken into ac’count,a truer estimate‘of’kightspeedis in the range O-650.70 msec (2.34 to 2.52 km/h). Discussion
In studieson host-findingbehaviouror flight-speed, electrocutinggrids have beenusedto intercept tsetse fliesand mosquitoes in tight (VALE, 1974; GILLIES et al., 1978).There are, however, no reports of grids being usedto intercept flying sandflies,presumably because of the problemsof makinga high voltagegrid with wires close enough to ensure that sandllies cannot passthrough without being killed. The grid used in the presentwork was highly efficient and required little maintenanceother than daily cleaning with alcohol and occasionaleasingof the springs tensioningthe wires.However, the tunnel in which it wasfitted wasnot aerodynamicallydesignedand there wereminor variationsin air speeds in different places. We consideredthe possibility that the flies had hoppedup the tunnel whenit would be expectedthat the majority would be killed only a few centimetres abovethe floor. To test this point, we photographed the grid throughouta 30min control experimentwith
Fig. 3. Sand&s being electrocuted on the grid; the camera shutter was kept open (at f 4 with Ilford HP4 film) for 30 min and the white spots are flashes caused by sandflies hitting the grid; note fly in Aight showing size in relation to gaps in the wire (arrowed); tunnel air speed was 0.35 misec.
R.
Fig. 4. Vent
,35
Axia
fan trap
(F) set up 5 m in front
et
KILLICK-KEXDRICK
al.
of tunnel
I LO
l-‘lg. 5. Percentages of female sand&es of the total number of flies caught
-45
55
60
1 --L.-T+-
70 r turd i m I secj in the wind tunnel at tunnel wmd speeds from 0.15 to 0.70 m~sec. (The figures plotted m the tunnel and in the fan trap 5 m in front of the tunnel.) 50
-65
/i
a,r speed
killed both
are percentages
142
FLIGHT
SPEED
OF
PHLEBOTOMINE
a tunnel air speed of 0.35 m/set (Fig. 3). The photograph suggests that, at that speed, the flies did not hop up the floor of the tunnel but generally flew up the slowest air speed on the left. We have no information on the behaviour of the llies at higher air speeds. In experiments similar to ours, GILLIES & WILKES (1981) estimatedthat the maximum flight speedof severalsnecies of African Anotheles andMansmia was from 1.4 to 1.8 m/set (5.0-65 km/h). Our results suggestthat a similarestimatefor sandfliesis a little lessthan half that sneedCO.65 to 0.70 msec = 2.3 to 2.5 km/h). It is, theieforej clearthat the sandflywhich moved2.2 km in 68.5 h (KILLICK-KENDRICK et al., 1984)could easily have flown that distancein that time without the assistanceof wind, even on the assumptions that (i) its movementwasconfinedto the hours of darkness,(ii) it did not fly in a direct line, (iii) it did not fly at its maximumspeedand (iv) that tt rested for considerableperiods. Acknowledgements This work is part of a study in collaboration with Prof. J-A. Rioux, Faculte de Medecine, Montpellier, France, on the bioloav of P. ariasi: we acknowledee with warm thanks his help and encouragement. Finan& support from the Medical Research Council, London and the WHO, Geneva, is gratefully acknowledged. References Gillies, M. T., Jones, M. D. & Wilkes, T. J. (1978). Evaluation of a new technique for recording the direction of fhght of mosquitoes (Diptera: Culicidae) in the field. Bulletin of Entomological Research, 68, 145-152. Gillies, M. T. & Wilkes, T. J. (1981). Field experiments with a wind tunnel on the flight speed of some West African mosquitoes (Diptera: Culicidae). Bulletin of Entomological Research, 71, 65-70.
SANDFLIES
Killick-Kendrick, R. & Rioux, J-A. (1981). The Cevennes focus of leishmaniasis in southern France and the biology of the vector, Phlebotomus ariasi. In: Parasitological Topics, E. U. Canning (Editor). Society of Protozoologists Special Publication No. 1, pp. 136-145. Killick-Kenderick, R., Rioux, J-A., Bailly, M., Guy, M. W., Wilkes, T. J., Guy, F. M., Davidson, I., Knechtli, R., Ward, R. D., Guilvard, E., P&i&es, J. & Dubois, H. (1984). Ecology of leishmaniasis in the south of France. 20. Dispersal of Phlebotomus ariasi Tonnoir, 1921 as a factor in the spread of visceral leishmaniasis in the Cevennes. Annales de Parasitologic humaine et comparie, 59, 555-572. Killick-Kendrick, R., Wilkes, T. J., Alexander, J., Bray, R. S., Rioux, J-A. & Bailly, M. (1985). The distance of attraction of CDC light traps to phlebotomine sandflies. Annales de Parasitologic humaine et comparee, (in press). Pedgley, D. E. (1983). Windborne spread of insecttransmitted diseases of animals and man. Philosphical Transactions of the Royal Society, London, B 302,463-470. Righton, L. A., Killick-Kendrick,, R. Wilkes, T. J. & Bailly, M. (1985). An electrocution grid for intercepting sandflies in flight (laboratory demonstration). Trunsactions of the Royal Society of Tropical Medicine and Hygiene, 79, 279-280. Rioux, J-A., Killick-Kendrick, R., Leaney, A. J., Turner, D. I’. , Bailly, M. & Young, C. J. (1979). Ecologic des Leishmanioses dans le sud de la France. 12. Dispersion horizontale de Phlebotomus ariasi Tonnoir. 1921. Exoeriences prtliminaires. Annales de Parasitologic huma& et cornparke, 54, 673-682. Sellers, R. F. (1983). Seasonal variations in spread of arthropod-borne disease agents of man and animals: implications for control. Philosophical Transactions of the Royal Society, London, B 302, 485-495. Vale, G. A. (1974). New field methods for studying responses of tsetse flies (Diptera, Glossinidae) to hosts. Bulletin of Entomological Research, 64, 199-208.
Accepted for publication
1st February,
1985.
Preliminary R.
field observations
AND HYGIENE (1986) 80, 138-142
on the flight sandfly
T. J. WILKES, M. BAILLY, of Pure and Applied Biology, Imperial
KILLICK-KENDRICK*,
Department
speed of a phlebotomine I. BAILLY AND L. A. RIGHTON College,
London
SW7 4AZ
Abstract
From observationswith a portablewind tunnel usedin the field in southernFrance, it is estimated that the maximumflight speedof Phlebowmus ariasi is in the range0.65-0.70m/set(2.3 to 2.5 km/h).
KENDRICK et al. (1984).
by a cloth sleeve to a tent containing two people (Fig. 1). Nine fans at the back of the tunnel sucked host-conditioned air from the tent and blew it down the tunnel (Fig. 2). Wild hungry female sandflies were attracted up the odour plume and entered the tunnel seeking the source. On meeting the electric grid, they were killed (Fig. 3). By varying the air speed in the tunnel, an estimate was made of the maximum speed of air against which the flies could fly and, thus, of the maximum flight speed of the flies. In nine experiments lasting 20 min, and one of 15 rnin, the air speeds were varied from 0.35 (two ex eriments 0.40 (one), 0.50, (four), 0.60 (one) to 0.70 (two f misec. Ae air speeds were measured with a DISA type 54N50Low Velocity Flow Analyzer placed in front of the centre of the grid. The air speed on the left side, when looking up the tunnel, was about 12% slower than that at the centre whereas that on the right side was about 12% faster. The electrocuted flies were in excellent condition with only minor damage to the legs and wings. None was charred, and they were easy to dissect. Samples of female sax&lies were identified by their spermathecae as P. ariasi. It is confidently assumed that all sandties were the same because other species of Phlebotonws known to be present (P. pemiciosus and P. mascittii) are apparently in very low densities and are seldom encountered in the valley where the work was done. A Vent Axia fan trap (KILLICK-KENDRICK et al., 1985) was set up in the host-conditioned air 5 m in front of the tunnel to monitor the numbers of ilies responding to the odour during the period of each experiment (Fig. 4). The numbers of female sandflies electrocuted in the tunnel were then expressed as a percentage of the total carch (from the
with the prevailing nocturnal wind. The tunnel was attached
*MRC External Scientific Staff
Introduction
In mark-release-recapture studieson the dispersal of Phlebowmus ariasi Tonnoir, 1921in the south of France, one female fly wasrecaptured 2.2 km in a direct line from the placeof release;it had movedthis distance in only 68.5 hours. A number of other femaleswere recapturedat distancesof about 1 km (KILLICK-KENDRICK et al., 1984). P. ariasi is the provenvector of Leishmania infanturn in the Cevennes focus (KILLICK-KENDRICK& RIOUX, 1981)and the movementof the flies wasconsideredasone way in which leishmaniasis could be spreadin that part of France and, possibly, in other foci. The questionarisesasto whether santies actively fly suchcomparativelylong distancesor whether the movement is assistedby wind as it is with many insects,includingseveralvectorssuchassomespecies of blackflies, mosquitoesand midges (PEDGLEY, 1983; SELLERS,1983).We therefore made preliminary observationson the flight speedof P. ariasi to find out if the distancesthe markedfliesmovedcould have been achievedby active flight alone. Materials
and Methods
TheworkwasdonefrommidJulyto midAugust,1984,in thecommune of Roquedur,department of Gard,France,in theCCvennes focusof visceralleishmaniasis. Descriptions of the placearegivenby RIOUX et al., (1979)andKILLICKA windtunnel(1 x 0.3 x 0.3 m) with an electrocuting grid(RIGHTON et al., 1985) was set up in an orchard in line
Table I-Numbers of female sandflies killed in a wind tunnel and caught in a Vent Axia fan trap 5 m in front of the tunnel with tunnel air speeds from 0.35 to 0.70 mkec; except where indicated, all experiments were run for 20 min
Tunnel air speed (mkec) o-35 o-35 * 0.40 E8 0.50 0.50 0.60 0.70 0.70
* 15 minute run.
No. of flies caught in fan trap
% of total catch killed
113 125 178
44 40 i:
72-O 75.8 68.2
47 2;
51 f:
1: 9 3
2;
56.0 37.8 41.6 33.0 26.3 14.1 11.1
N&$
E
tunnel
24
in tunnel
R.
Fig.
1. Wind
FIN 2. Wind
tunnel
tunnel
attached
showing
to a tent
containing
KII.LI(:K-KENDRICK
139
f?Z al.
two people.
set of 9 fans (F:, gauze filters
(G), electrocutmg
grid (E!, high voltage
unit CH) and 3 battery
pods pownng
fans !B!.
140
FLIGHT
tunnel and the fan trap). Comparisons could results obtained During each
on different
SPEED
OF
PHLEBOTOMINE
thus be made of
nights.
experiment, records were kept of the ambient temperature, relative humidity and wind speed and direc-
tion.
All observations
midnight.
were made between
22.30
hours and
Results
At external wind speedsof >05 msec very few flies were caught in the tunnel. However, when the wind speedwas<0.5 msecfor at leasthalf of the time of an experiment, the temperaturewas ~16°C and tunnelair speedswerelow, many sandfliesenteredthe tunnel and were killed on the electrocution grid. The numbers of female sandfliescaught in the tunnel and the fan trap in 10 experimentsat suitable temperaturesand wind speedsare shownin Table I. When the percentageof the lliescaughtin the tunnel (of the catchesin -me tunnel and the fan trap) are nlotted and a regressionline fitted (Fig. 5), the approximatemaximum Ilight speedof ‘the flies (i.e. the maximum speedof wind againstwhich any flies can fly) appearsto be about 0.75 m/set. However, tunnel air speedswere measuredat the centre of the grid but the fliesdetectedand generallyfavoured the
SANDFLIES
left sidewhere the speedwasabout 12%slowerthan at the ooint of measurement(Fix. 3). If this is taken into ac’count,a truer estimate‘of’kightspeedis in the range O-650.70 msec (2.34 to 2.52 km/h). Discussion
In studieson host-findingbehaviouror flight-speed, electrocutinggrids have beenusedto intercept tsetse fliesand mosquitoes in tight (VALE, 1974; GILLIES et al., 1978).There are, however, no reports of grids being usedto intercept flying sandflies,presumably because of the problemsof makinga high voltagegrid with wires close enough to ensure that sandllies cannot passthrough without being killed. The grid used in the presentwork was highly efficient and required little maintenanceother than daily cleaning with alcohol and occasionaleasingof the springs tensioningthe wires.However, the tunnel in which it wasfitted wasnot aerodynamicallydesignedand there wereminor variationsin air speeds in different places. We consideredthe possibility that the flies had hoppedup the tunnel whenit would be expectedthat the majority would be killed only a few centimetres abovethe floor. To test this point, we photographed the grid throughouta 30min control experimentwith
Fig. 3. Sand&s being electrocuted on the grid; the camera shutter was kept open (at f 4 with Ilford HP4 film) for 30 min and the white spots are flashes caused by sandflies hitting the grid; note fly in Aight showing size in relation to gaps in the wire (arrowed); tunnel air speed was 0.35 misec.
R.
Fig. 4. Vent
,35
Axia
fan trap
(F) set up 5 m in front
et
KILLICK-KEXDRICK
al.
of tunnel
I LO
l-‘lg. 5. Percentages of female sand&es of the total number of flies caught
-45
55
60
1 --L.-T+-
70 r turd i m I secj in the wind tunnel at tunnel wmd speeds from 0.15 to 0.70 m~sec. (The figures plotted m the tunnel and in the fan trap 5 m in front of the tunnel.) 50
-65
/i
a,r speed
killed both
are percentages
142
FLIGHT
SPEED
OF
PHLEBOTOMINE
a tunnel air speed of 0.35 m/set (Fig. 3). The photograph suggests that, at that speed, the flies did not hop up the floor of the tunnel but generally flew up the slowest air speed on the left. We have no information on the behaviour of the llies at higher air speeds. In experiments similar to ours, GILLIES & WILKES (1981) estimatedthat the maximum flight speedof severalsnecies of African Anotheles andMansmia was from 1.4 to 1.8 m/set (5.0-65 km/h). Our results suggestthat a similarestimatefor sandfliesis a little lessthan half that sneedCO.65 to 0.70 msec = 2.3 to 2.5 km/h). It is, theieforej clearthat the sandflywhich moved2.2 km in 68.5 h (KILLICK-KENDRICK et al., 1984)could easily have flown that distancein that time without the assistanceof wind, even on the assumptions that (i) its movementwasconfinedto the hours of darkness,(ii) it did not fly in a direct line, (iii) it did not fly at its maximumspeedand (iv) that tt rested for considerableperiods. Acknowledgements This work is part of a study in collaboration with Prof. J-A. Rioux, Faculte de Medecine, Montpellier, France, on the bioloav of P. ariasi: we acknowledee with warm thanks his help and encouragement. Finan& support from the Medical Research Council, London and the WHO, Geneva, is gratefully acknowledged. References Gillies, M. T., Jones, M. D. & Wilkes, T. J. (1978). Evaluation of a new technique for recording the direction of fhght of mosquitoes (Diptera: Culicidae) in the field. Bulletin of Entomological Research, 68, 145-152. Gillies, M. T. & Wilkes, T. J. (1981). Field experiments with a wind tunnel on the flight speed of some West African mosquitoes (Diptera: Culicidae). Bulletin of Entomological Research, 71, 65-70.
SANDFLIES
Killick-Kendrick, R. & Rioux, J-A. (1981). The Cevennes focus of leishmaniasis in southern France and the biology of the vector, Phlebotomus ariasi. In: Parasitological Topics, E. U. Canning (Editor). Society of Protozoologists Special Publication No. 1, pp. 136-145. Killick-Kenderick, R., Rioux, J-A., Bailly, M., Guy, M. W., Wilkes, T. J., Guy, F. M., Davidson, I., Knechtli, R., Ward, R. D., Guilvard, E., P&i&es, J. & Dubois, H. (1984). Ecology of leishmaniasis in the south of France. 20. Dispersal of Phlebotomus ariasi Tonnoir, 1921 as a factor in the spread of visceral leishmaniasis in the Cevennes. Annales de Parasitologic humaine et comparie, 59, 555-572. Killick-Kendrick, R., Wilkes, T. J., Alexander, J., Bray, R. S., Rioux, J-A. & Bailly, M. (1985). The distance of attraction of CDC light traps to phlebotomine sandflies. Annales de Parasitologic humaine et comparee, (in press). Pedgley, D. E. (1983). Windborne spread of insecttransmitted diseases of animals and man. Philosphical Transactions of the Royal Society, London, B 302,463-470. Righton, L. A., Killick-Kendrick,, R. Wilkes, T. J. & Bailly, M. (1985). An electrocution grid for intercepting sandflies in flight (laboratory demonstration). Trunsactions of the Royal Society of Tropical Medicine and Hygiene, 79, 279-280. Rioux, J-A., Killick-Kendrick, R., Leaney, A. J., Turner, D. I’. , Bailly, M. & Young, C. J. (1979). Ecologic des Leishmanioses dans le sud de la France. 12. Dispersion horizontale de Phlebotomus ariasi Tonnoir. 1921. Exoeriences prtliminaires. Annales de Parasitologic huma& et cornparke, 54, 673-682. Sellers, R. F. (1983). Seasonal variations in spread of arthropod-borne disease agents of man and animals: implications for control. Philosophical Transactions of the Royal Society, London, B 302, 485-495. Vale, G. A. (1974). New field methods for studying responses of tsetse flies (Diptera, Glossinidae) to hosts. Bulletin of Entomological Research, 64, 199-208.
Accepted for publication
1st February,
1985.