J.
MecL EntolDol.
Vol. 14,
DO.
25 NovelDber 1977
2: 201-203
PRELIMINARY OBSERVATIONS OF TABANIDAE AT A TSETSE PICKET IN THE REPUBLIC OF ZAMBIA By S. N. Okiwelul Abstract: The species composition and settling behavior of tabanids at a tsetse picket located at the edge of a tsetse- and tabanid-infested miombo woodland were studied during 1 rainy season, Nov. I975-April 1976. Sticky traps (on fallen logs, bushes, treetops, wooden gate and fence posts) were used to trap tabanids at various distances from the picket. Tabanus cOlli/omlis, T. tamiola, Haematopo/a dis/inc/a, H. s/imulans, H. per/urbans, H. decora, and T. sandersolli were collected off vehicles and traps at the picket; H. pallidimarginata and H. hirsutitarsis
The tsetse picket is a device directed at the "carried" fly and involves the establishment of barriers manned by guards who apply insecticides to vehicles, bicycles, etc., and who defly motorists, cyclists, and pedestrians from tsetse-infested areas. The commonly used insecticide is Pybuthrin2, a pyrethrum-based contact insecticide; this is applied by a small portable mechanically operated spray pump. In Zambia, these barriers are usually wooden or metal gates, although in a few cases traffic is channelled through concrete or wooden enclosures where insecticide is applied. Although the latter arrangement has been found more effective, it has not been possible to use it more frequently because of prohibitive construction costs. The tsetse picket has not been widely discussed as a control measure in tsetse literature; but it has been in use in the Republic of Zambia since the early 1950s, and its importance is reflected in the increase in the number of pickets from 162 in 1966 to 274 in 1971 (Dept. Vet. and Tsetse Control Services 1972, 1973). The growing concern about the role of tabanids in the mechanical transmission of cattle trypanosomiasis in the country has intensified the search for effective control measures against them; one of the suggested measures was the catching of "carried" tabanids at tsetse pickets. An attempt was therefore IPest Research Unit, National C-;;~cil-f~rSc:ientificResearch, P. O. Box 49, Chilanga, Zambia. Present address: Chemonics, Anll'rican Embassy, Bamako,' Mali, West Africa. 'Product of Cooper, McDougall and Robertson (Zambia) Ltd.
MATERIALS
AND METHODS
The study area is in the Chakwenga Game Reserve, a plateau lying between the Zambezi and Lusemfwa Valleys, 29°15'E and 15°13'S. The dominant vegetation is a miombo woodland of deciduous trees with a lightly closed canopy, 1521 m high. The picket is in a woodland area which was totally cleared in 1970, approximately 1200 m from the edge of a tsetse- and tabanid-infested miombo woodland. The following species are known to occur in the woodland (Okiwelu 1975b): Tabanus taeniola, T. sandersoni, T. coniformis, T. ustus, T. variabilis, Haematopota stimulans, H. pallidimarginata, H. distincta, H. decora, H. hirsutitarsis, H. perturbans, and H. albihirta. The traffic passing through the picket consisted mainly of vehicles transporting field staff from the woodland to and from their camp. A "game" fence has been erected on either side of the picket for restricting game animals to the woodland and therefore preventing the spread of "game" -carried tsetse. Vehicles from the woodland were stopped daily at the picket during the study period and were treated with insecticide and all dead and live tabanids from both vehicles and staff were collected and identified; identification was based on an earlier study (Okiwelu 1975b). In order to determine the settling distances from the picket oftabanids escaping during spraying, sticky traps were used. These traps were located on 3 concentric circles approximately 10 m from one another, with the spraying point as center. The innermost circle was designated 1, the middle 2 and the outermost 3 (FIG. 1). Fallen logs, bushes (grassy ground cover), 1- to 1.5-m high treetops, six 2-m high wooden fence posts and two 3-m high wooden gate posts located less than I m from the spraying point were used as traps (FIG. 1). Tanglefoot3, a colorless, odorless, sticky substance was indirectly applied to these 'Product of the Tanglefoot Company, Grand R;'-pids, Michigan, U.S.A.
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
found in the adjacent woodland during the study period were not recorded at the picket. The heterogeneity in numbers of tabanids at various distances from the spraying point was not significant; substantial numbers were found at distances of 30 m from the spraying point. Most tabanids were trapped on treetops and least from fallen logs. The total number of trapped tabanids near the picket was almost equal to the number caught offvehides. Two species (H. dis/inc/a, H. drcora) followedvehicles after they left the picket.
made during 1 Zambian rainy season, November 1975-April 1976, when tabanids are usually abundant (Okiwelu 1975a), to investigate the species composition and behavior of tabanids at a tsetse picket.
J. Med.
202
TOTALLY
CLEARED
"110"180
WOODLAND
Vol. 14, no. 2
Entomol.
LEF'T INSIDE
FENCE
2
1
RIGHT OUTStDE
TOTALLY
CLEARED
1
16 0,
0 26
o o
1.1101.180 WOODLAND
~
)lEF'T
LEFT OUTSIDE
o.
6
)6 0)
-
TotALLY
TO
LABORATORY
TOTALLY
CLEARED
MIOM80
WOODLAND
CLEARED
WOODLAND
m --
SPFM'I"lNG GAME
POINT
FENCE
ROAD
X ~
o +
o X
sites; application procedures have been extensively describer! and the method used for gate and game fence posts was similar to that used for boles in studies on resting sites of Glossina (Okiwelu 1977a). This involved the banding of gate and fence posts and a bole near the laboratory with paper from ground level to heights of 2 m; each fallen log was also banded with the same material for a distance of 2 m. Bushes and treetops were each covered with netting material I m X I m. The outer surfaces of the paper and netting on all sites were lightly treated with Tanglefoot, and in all cases, the color of netting or paper was chosen to blend with the site under observation. Locations of traps around the picket have been designated by the terms inside right, inside left, outside right, outside left, fence right, fence left; designations are based on positions of traps in relation to vehicle movement from woodland and game fence (FIG. 1). The chi-square test was used to compare the number of trapped tabanids at different settling distances from the picket. An attempt was further made to determine whether some of the tabanids escaping during spraying followed vehicles after they left the picket; the bole of a large tree near the field laboratory, located approximately 450 m from the picket, that provided shade for parked vehicles was used as a sticky trap
WOOQE:N
FENCE
POST
CANOPY FALLEN
LOG
BOLE BU5H
wOODEN
GATE
POST
FIG. I. Map indicating location of picket and position of traps.
to collect this group of tabanids (FIG. I). Just before the arrival of vehicles from the wood· land, all trapped insects on the sticky traps near the picket were collected and discarded, since these might contain tabanids that strayed from the woodland; a few minutes after vehicles left the picket for the laboratory all trapped tabanids were collected and identified. Before the arrival of vehicles at the parking spot near the laboratory, all trapped insects on the adjacent bole were collected and discarded and after the arrival of vehicles, all trapped tabanids were collected and identified. RESULTS
Seven (T. coniformis, T. taeniola, H. distincta, H. stimulans, H. perturbans, H. decora, T. sandersoni) of 9 species found in the adjacent woodland during the study period were collected off vehicles and traps at the picket; H. pallidimariginata and H. hirsutitarsis were absent from the picket collections (TABLE I). The heterogeneity in the numbers of tabanids at various distances from the spraying point was not significant Cy2, 3 df= 1.8965); substantial numbers of tabanids were found at distances of 30 m from the spraying point (TABLE 2). Most tabanids were collected from treetops and least from fallen logs; however, based on the number of tabanids per
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
MIOM80
ROAD
6
1977 TABLE
I. Species composition
Okiwelu:
Tabanids
of tabanids
trapped
203
at a tsetse picket in Zambia at different
site types and caught
off vehicles at a tsetse picket.
SITE TYPES (SAMPLENO.) Canopies (12)
SPECIES
2
Tabanus conifonnis T.laeniola Haemalopola distirlcla H. slimulans H. perturbans H. decora Tabanus sandersoni Totals ~o. per trap
6
4 3
0 0
o
5
0
4
o
2
42
8
18
o o
o
13
o
o
65
30
5
3
30 18
~umbers
of tabanids
DISTANCE FROM -.-----SPRAYING Inside POINT (m) right
Inside left
Outside right
trapped
at different
locations
Bole near lab. (1)
No. OFF VEHICLES
o o
4
3
o
2
0
o o
43
6
13
92
2
o
14 2
15 15
14 169
around
13
a tsetse picket.
LOCATION OF SITES
4 20 13
9 3
9
11 4 0
Outside left 12 4 5
trap for each site type, gate posts were most preferred (TABLE 1). The total number (145) of trapped tabanids near the picket escaping the insecticidal treatment was almost equal to the number (169) caught off vehicles. Two species, H. distincta (2) and H. decora (13), were collected on the bole close to the laboratory. DISCUSSION
The collection at the picket of only 7 of the 9 species recorded in the adjacent miombo woodland during- the study period indicates that some species may not be attracted to moving vehicles. Since substantial numbers of tabanids were found at distances of 30 m from the spraying point, it would appear that sizable numbers might have even settled beyond the 60-m diam. area; the absence of any physical barrier would also definitely increase the probability. The preference for treetops was not surprising because this site type had been found to be a popular resting site for tabanids (Okiwelu 1977b), and the selection of gate posts could be attributed to their proximity to the spraying point and conspicuous appearance. The low numbers collected off fallen logs might have been due to their relatively hidden location. The collection of tabanids from the bole near the laboratory indicated that some of those escaping insecticidal treatment later followed the vehicles; however, it should not be assumed that, because only 2 species were found on the bole, this type of behavior is exclusive to these species, since other species following the vehicles might have settled on other available site types near
Fence right 1 0 0
Fence left
Gate post right
Gate post left
23
13
6 3 5
TOTALS 36 43 34 32
the laboratory. The collection of almost equal numbers of tab an ids off vehicles and traps was rather surprising; since traps covered only a small part of the 60-m diam. area, it was very likely that many more tabanids escaped and settled on the remaining part. This preliminary investigation indicates that the suggested measure of catching "carried" tabanids at open tsetse pickets may not be very effective, since a very small proportion of "carried" tabanids would be caught; collections at pickets with enclosures would probably be more effective. Acknowledgments: I wish to thank Mr C. Mangoye for supervising the field collections and Mr L. M. Diddee, Biometrician, National Council for Scientific Research, for assistance with the statistical analysis. I am grateful to the Secretary General, National Council for Scientific Research, for permission to publish. LITERATURE
CITED
Dept. Vet. and Tsetse Countrol Services. 1972. Annual report for 1966, Republic of Zambia. Government Printer, Lusaka, Zambia. 19 p. 1973. Annual report for 1971, Republic of Zambia. Government Printer, Lusaka, Zambia. 26 p. Okiwelu, S. N. 1975a. Seasonal distribution and variations in diurnal activity of Tabanidae in the Republic ofZarnbia. Mosq. News 35: 551-54. 1975b. Tabanidae of a miombo woodland in the Republic of Zambia. Mosq. News 35: 399-401. 1977a. Observations of resting sites of Glossina morsitans Illorsitans (Diptera: Muscidae) during the wet season in the Republic of Zambia, Africa. J. Med. Entomol. 13: 595-99. 1977b. Observations on the resting sites of Tabanidae in a miombo woodland in the Republic of Zambia. J. Med. Enlomol. 14: 195-97.
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
I 10 20 30
Fallen logs (9)
4
15 7
4
2.
TABLE
Gate posts (2)
Bushes (9)
MecL EntolDol.
Vol. 14,
DO.
25 NovelDber 1977
2: 201-203
PRELIMINARY OBSERVATIONS OF TABANIDAE AT A TSETSE PICKET IN THE REPUBLIC OF ZAMBIA By S. N. Okiwelul Abstract: The species composition and settling behavior of tabanids at a tsetse picket located at the edge of a tsetse- and tabanid-infested miombo woodland were studied during 1 rainy season, Nov. I975-April 1976. Sticky traps (on fallen logs, bushes, treetops, wooden gate and fence posts) were used to trap tabanids at various distances from the picket. Tabanus cOlli/omlis, T. tamiola, Haematopo/a dis/inc/a, H. s/imulans, H. per/urbans, H. decora, and T. sandersolli were collected off vehicles and traps at the picket; H. pallidimarginata and H. hirsutitarsis
The tsetse picket is a device directed at the "carried" fly and involves the establishment of barriers manned by guards who apply insecticides to vehicles, bicycles, etc., and who defly motorists, cyclists, and pedestrians from tsetse-infested areas. The commonly used insecticide is Pybuthrin2, a pyrethrum-based contact insecticide; this is applied by a small portable mechanically operated spray pump. In Zambia, these barriers are usually wooden or metal gates, although in a few cases traffic is channelled through concrete or wooden enclosures where insecticide is applied. Although the latter arrangement has been found more effective, it has not been possible to use it more frequently because of prohibitive construction costs. The tsetse picket has not been widely discussed as a control measure in tsetse literature; but it has been in use in the Republic of Zambia since the early 1950s, and its importance is reflected in the increase in the number of pickets from 162 in 1966 to 274 in 1971 (Dept. Vet. and Tsetse Control Services 1972, 1973). The growing concern about the role of tabanids in the mechanical transmission of cattle trypanosomiasis in the country has intensified the search for effective control measures against them; one of the suggested measures was the catching of "carried" tabanids at tsetse pickets. An attempt was therefore IPest Research Unit, National C-;;~cil-f~rSc:ientificResearch, P. O. Box 49, Chilanga, Zambia. Present address: Chemonics, Anll'rican Embassy, Bamako,' Mali, West Africa. 'Product of Cooper, McDougall and Robertson (Zambia) Ltd.
MATERIALS
AND METHODS
The study area is in the Chakwenga Game Reserve, a plateau lying between the Zambezi and Lusemfwa Valleys, 29°15'E and 15°13'S. The dominant vegetation is a miombo woodland of deciduous trees with a lightly closed canopy, 1521 m high. The picket is in a woodland area which was totally cleared in 1970, approximately 1200 m from the edge of a tsetse- and tabanid-infested miombo woodland. The following species are known to occur in the woodland (Okiwelu 1975b): Tabanus taeniola, T. sandersoni, T. coniformis, T. ustus, T. variabilis, Haematopota stimulans, H. pallidimarginata, H. distincta, H. decora, H. hirsutitarsis, H. perturbans, and H. albihirta. The traffic passing through the picket consisted mainly of vehicles transporting field staff from the woodland to and from their camp. A "game" fence has been erected on either side of the picket for restricting game animals to the woodland and therefore preventing the spread of "game" -carried tsetse. Vehicles from the woodland were stopped daily at the picket during the study period and were treated with insecticide and all dead and live tabanids from both vehicles and staff were collected and identified; identification was based on an earlier study (Okiwelu 1975b). In order to determine the settling distances from the picket oftabanids escaping during spraying, sticky traps were used. These traps were located on 3 concentric circles approximately 10 m from one another, with the spraying point as center. The innermost circle was designated 1, the middle 2 and the outermost 3 (FIG. 1). Fallen logs, bushes (grassy ground cover), 1- to 1.5-m high treetops, six 2-m high wooden fence posts and two 3-m high wooden gate posts located less than I m from the spraying point were used as traps (FIG. 1). Tanglefoot3, a colorless, odorless, sticky substance was indirectly applied to these 'Product of the Tanglefoot Company, Grand R;'-pids, Michigan, U.S.A.
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
found in the adjacent woodland during the study period were not recorded at the picket. The heterogeneity in numbers of tabanids at various distances from the spraying point was not significant; substantial numbers were found at distances of 30 m from the spraying point. Most tabanids were trapped on treetops and least from fallen logs. The total number of trapped tabanids near the picket was almost equal to the number caught offvehides. Two species (H. dis/inc/a, H. drcora) followedvehicles after they left the picket.
made during 1 Zambian rainy season, November 1975-April 1976, when tabanids are usually abundant (Okiwelu 1975a), to investigate the species composition and behavior of tabanids at a tsetse picket.
J. Med.
202
TOTALLY
CLEARED
"110"180
WOODLAND
Vol. 14, no. 2
Entomol.
LEF'T INSIDE
FENCE
2
1
RIGHT OUTStDE
TOTALLY
CLEARED
1
16 0,
0 26
o o
1.1101.180 WOODLAND
~
)lEF'T
LEFT OUTSIDE
o.
6
)6 0)
-
TotALLY
TO
LABORATORY
TOTALLY
CLEARED
MIOM80
WOODLAND
CLEARED
WOODLAND
m --
SPFM'I"lNG GAME
POINT
FENCE
ROAD
X ~
o +
o X
sites; application procedures have been extensively describer! and the method used for gate and game fence posts was similar to that used for boles in studies on resting sites of Glossina (Okiwelu 1977a). This involved the banding of gate and fence posts and a bole near the laboratory with paper from ground level to heights of 2 m; each fallen log was also banded with the same material for a distance of 2 m. Bushes and treetops were each covered with netting material I m X I m. The outer surfaces of the paper and netting on all sites were lightly treated with Tanglefoot, and in all cases, the color of netting or paper was chosen to blend with the site under observation. Locations of traps around the picket have been designated by the terms inside right, inside left, outside right, outside left, fence right, fence left; designations are based on positions of traps in relation to vehicle movement from woodland and game fence (FIG. 1). The chi-square test was used to compare the number of trapped tabanids at different settling distances from the picket. An attempt was further made to determine whether some of the tabanids escaping during spraying followed vehicles after they left the picket; the bole of a large tree near the field laboratory, located approximately 450 m from the picket, that provided shade for parked vehicles was used as a sticky trap
WOOQE:N
FENCE
POST
CANOPY FALLEN
LOG
BOLE BU5H
wOODEN
GATE
POST
FIG. I. Map indicating location of picket and position of traps.
to collect this group of tabanids (FIG. I). Just before the arrival of vehicles from the wood· land, all trapped insects on the sticky traps near the picket were collected and discarded, since these might contain tabanids that strayed from the woodland; a few minutes after vehicles left the picket for the laboratory all trapped tabanids were collected and identified. Before the arrival of vehicles at the parking spot near the laboratory, all trapped insects on the adjacent bole were collected and discarded and after the arrival of vehicles, all trapped tabanids were collected and identified. RESULTS
Seven (T. coniformis, T. taeniola, H. distincta, H. stimulans, H. perturbans, H. decora, T. sandersoni) of 9 species found in the adjacent woodland during the study period were collected off vehicles and traps at the picket; H. pallidimariginata and H. hirsutitarsis were absent from the picket collections (TABLE I). The heterogeneity in the numbers of tabanids at various distances from the spraying point was not significant Cy2, 3 df= 1.8965); substantial numbers of tabanids were found at distances of 30 m from the spraying point (TABLE 2). Most tabanids were collected from treetops and least from fallen logs; however, based on the number of tabanids per
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
MIOM80
ROAD
6
1977 TABLE
I. Species composition
Okiwelu:
Tabanids
of tabanids
trapped
203
at a tsetse picket in Zambia at different
site types and caught
off vehicles at a tsetse picket.
SITE TYPES (SAMPLENO.) Canopies (12)
SPECIES
2
Tabanus conifonnis T.laeniola Haemalopola distirlcla H. slimulans H. perturbans H. decora Tabanus sandersoni Totals ~o. per trap
6
4 3
0 0
o
5
0
4
o
2
42
8
18
o o
o
13
o
o
65
30
5
3
30 18
~umbers
of tabanids
DISTANCE FROM -.-----SPRAYING Inside POINT (m) right
Inside left
Outside right
trapped
at different
locations
Bole near lab. (1)
No. OFF VEHICLES
o o
4
3
o
2
0
o o
43
6
13
92
2
o
14 2
15 15
14 169
around
13
a tsetse picket.
LOCATION OF SITES
4 20 13
9 3
9
11 4 0
Outside left 12 4 5
trap for each site type, gate posts were most preferred (TABLE 1). The total number (145) of trapped tabanids near the picket escaping the insecticidal treatment was almost equal to the number (169) caught off vehicles. Two species, H. distincta (2) and H. decora (13), were collected on the bole close to the laboratory. DISCUSSION
The collection at the picket of only 7 of the 9 species recorded in the adjacent miombo woodland during- the study period indicates that some species may not be attracted to moving vehicles. Since substantial numbers of tabanids were found at distances of 30 m from the spraying point, it would appear that sizable numbers might have even settled beyond the 60-m diam. area; the absence of any physical barrier would also definitely increase the probability. The preference for treetops was not surprising because this site type had been found to be a popular resting site for tabanids (Okiwelu 1977b), and the selection of gate posts could be attributed to their proximity to the spraying point and conspicuous appearance. The low numbers collected off fallen logs might have been due to their relatively hidden location. The collection of tabanids from the bole near the laboratory indicated that some of those escaping insecticidal treatment later followed the vehicles; however, it should not be assumed that, because only 2 species were found on the bole, this type of behavior is exclusive to these species, since other species following the vehicles might have settled on other available site types near
Fence right 1 0 0
Fence left
Gate post right
Gate post left
23
13
6 3 5
TOTALS 36 43 34 32
the laboratory. The collection of almost equal numbers of tab an ids off vehicles and traps was rather surprising; since traps covered only a small part of the 60-m diam. area, it was very likely that many more tabanids escaped and settled on the remaining part. This preliminary investigation indicates that the suggested measure of catching "carried" tabanids at open tsetse pickets may not be very effective, since a very small proportion of "carried" tabanids would be caught; collections at pickets with enclosures would probably be more effective. Acknowledgments: I wish to thank Mr C. Mangoye for supervising the field collections and Mr L. M. Diddee, Biometrician, National Council for Scientific Research, for assistance with the statistical analysis. I am grateful to the Secretary General, National Council for Scientific Research, for permission to publish. LITERATURE
CITED
Dept. Vet. and Tsetse Countrol Services. 1972. Annual report for 1966, Republic of Zambia. Government Printer, Lusaka, Zambia. 19 p. 1973. Annual report for 1971, Republic of Zambia. Government Printer, Lusaka, Zambia. 26 p. Okiwelu, S. N. 1975a. Seasonal distribution and variations in diurnal activity of Tabanidae in the Republic ofZarnbia. Mosq. News 35: 551-54. 1975b. Tabanidae of a miombo woodland in the Republic of Zambia. Mosq. News 35: 399-401. 1977a. Observations of resting sites of Glossina morsitans Illorsitans (Diptera: Muscidae) during the wet season in the Republic of Zambia, Africa. J. Med. Entomol. 13: 595-99. 1977b. Observations on the resting sites of Tabanidae in a miombo woodland in the Republic of Zambia. J. Med. Enlomol. 14: 195-97.
Downloaded from http://jme.oxfordjournals.org/ by guest on June 7, 2016
I 10 20 30
Fallen logs (9)
4
15 7
4
2.
TABLE
Gate posts (2)
Bushes (9)
