71
Mosquitoes collected on Weno Island,No.53（Romonum
Island and Piis Island, Chuuk State, Federated States of Micronesia (Diptera: Culicidae)
南太平洋海域調査研究報告201３年２月）
OCCASIONAL PAPERS No.53（February 2013）

Mosquitoes collected on Weno Island, Romonum Island and Piis Island,Chuuk State, Federated States of Micronesia (Diptera: Culicidae)
NODA Shinichi
Research Center for the Pacific Islands, Kagoshima University
Abstract
Mosquito larval surveys were carried out on Weno Island, Romonum Island andPiis Island in August 2011. Larvae were collected from 133 natural and artificial
habitats. A total of 1,761 larvae belonging to nine species including one unidentifiedspecies were collected. On Weno Island, eight species, Aedes hensilli， Ae. albopictus，Ae. lamelliferus, Aedes sp.， Culex quinquefasciatus， Cx. carolinensis， Cx. annulirostris andLutzia vorax, were collected. On Romonum Island，　 four species, Ae. scutoscriptus， Ae.
hensilli，　 Cx. quinquefasciatus and Cx. carolinensis were collected. On Piis Island, sixspecies, Ae. scutoscriptus， Ae. hensilli， Aedes sp.， Cx. quinquefasciatus， Cx. carolinensis andCx. annilirostris, were collected. Distributions of Ae. hensilli and Ae. albopictus wereconfirmed in this survey. To prevent the outbreak of dengue fever, environmental
management should focus on the destruction, alternation, disposal or recycling ofcontainers that produce the greater number of adult Aedes mosquitoes.
Key words: Aedes hensilli, Aedes albopictus, mosquito fauna, Chuuk State, Federated
States of Micronesia

Introduction
It is a well-known fact that major vectors for dengue fever and dengue
hemorrhagic fever are Aedes aegypti and Ae. albopictus in urban areas of Southeast
Asia and in the Western Pacific Region (WHO, 1995). SAVAGE et al. (1998) reported adengue fever outbreak in Yap State between June and July 1995 caused by denguetype-4 virus. After this outbreak of dengue fever, it was also reported in 2004, 2007
and 2011 in Yap State. Entomological investigations implicated the native mosquito
species, Ae. hensilli, as vector of dengue virus (SAVAGE et al., 1998; NODA et al., 2005).
There is a possibility of outbreak of denguefever in other states of Federated Statesof Micronesia. However, there is a little information for vector mosquito species. To
know the geographical distribution of vector mosquitoes, entomological surveillance
was carried out on Weno Island, Romonum Island and Piis Island, Chuuk State,Federated States of Micronesia. This report describes a survey of mosquito fauna andbreeding sites of mosquitoes.
Materials and Methods
Mosquito larval surveys were carried out on Weno Island, Romonum Island andPiis Island in August 2011, Chuuk State, Federated States of Micronesia (Fig. 1). Weno

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NODA Shinichi

Island is the capital and commercial center of Chuuk. At just over 18km 2, it is thesecond largest island in the lagoon. Tropical forests make up much of the interior,with the highest point, the 370m Mt. Tonoken, nearly in the center. Romonum Islandis also located in the lagoon, and it is less than 1 km2. Piis island is located on the atoll
ring reef, and it is also less than 1 km2.
Larval collections were made at 133 habitats in Weno Island (86 habitats),
Romonum Island (21 habitats) and Piis Island (26 habitats). The habitats are composedof coconut shells, rock pits, tree hole, banana stumps, wells, puddles, taro fields
and artificial containers such as concrete puddles, plastic water barrels as well as
discarded drink cans, glass containers, plastic containers, rubber containers, metalcontainers, buckets, plastic bags, pans, tires, freezer, washing machine and trackloading platform, and the collections were made with a pipet and dipper. Collectedlarvae were preserved in 70% ethanol, and some larvae were reared to the adult stage.
Identification of the larvae and adults was made by using the keys and descriptionsof BOHART (1957) and BOHART and INGRAM (1946). And, the classification of the species
belonging to the genera Lutzia follows that of TANAKA (2003).

Fig. 1 M ap of Chuuk Atoll. Mosquito larval surveys were carried out on Weno Island, Romonum
Island and Piis Island.

Results
On Weno Island, a total of 1,180 larvae belonging to eight species including one
unidentified species were collected at 86 natural and artificial habitats. They wereidentified as Aedes hensilli， Ae. albopictus， Ae. lamelliferus, Aedes sp., Culex quinquefasciatus,Cx. carolinensis, Cx. annulirostris and Lutzia vorax (Table 1). Among them, Cx. carolinensis
was the most predominant species collected (656 larvae, 41 habitats) followed by Ae.
hensilli (318 larvae, 44 habitats). Ae. albopictus was collected from discarded containers
along the main road.
On Romonum Island, a total of 204 larvae belonging to four species were collected
at 21 natural and artificial habitats. They were identified as Ae. scutoscriptus， Ae. hensilli，Cx. quinquefasciatus and Cx. carolinensis (Table 2). Among them, Ae. scutoscriptus was themost predominant species collected (99 larvae, 11 habitats).

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Mosquitoes collected on Weno Island, Romonum Island and Piis Island, Chuuk State, Federated States of Micronesia (Diptera: Culicidae)

Table 1. N umbers of mosquitoes and their habitat types collected in Weno Island, Chuuk State,Federated States of Micronesia.
Nunbercollectted

Number ofhabitat ＊Habitato types (No. of habitat)

Aedes hensilli

318

44

Coconut shells (14), Drink cans (9), Glass containers (4)Plastic bag (1), Plastic containers (9), Metal container (1)Bucket (1), Tires (3), Freezer (1), Plastic water barrel (1)Aedes albopictus

41

10

Coconut shells (2), Drink cans (5), Plastic container (1)Rubber container (1), Tire (1)Aedes lamelliferus

11

1

Coconut shell (1)Aedes sp.

1

1

Coconut shell (1)Culex quinquefasciatus

72

6

Coconut shells (3), Pan (1), Tire (1), Washing machine (1)Culex carolinensis

656

41

Coconut shells (18), Drink cans (7), Plastic containers (6)Rubber container (1), Bucket (1), Tires (8)Culex annulirostris

80

6

Drink can (1), Glass container (1), Bucket (1)Concrete puddle (1), Track loading platform (1),Taro field (1)Lutzia vorax

11

Drink can (1)＊Total number of habitat is 86.

Table 2. N umbers of mosquitoes and their habitat types collected in Romonum Island, Chuuk
State, Federated States of Micronesia.
Nunbercollectted

Number ofhabitat ＊Aedes hensilli

23

4

Coconut shell (1), Drink can (1), Rock pits (2)Aedes scutoscriptus

99

11

Coconut shells (2), Banana stumps (2), Drink can (1)Glass container (1), Rock pits (2), Plastic containers (3)Culex quinquefasciatus

16

3

Coconut shell (1), Glass container (1), Well (1)Culex carolinensis

66

4

Coconut shell (1), Glass container (1) Pan (1)Plastic water barrel (1)＊Total number of habitat is 21.

Habitato types (No. of habitat)

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NODA Shinichi

Table 3. N umbers of mosquitoes and their habitat types collected in Piis Island, Chuuk State,Federated States of Micronesia.
Nunbercollectted

Number ofhabitat ＊Aedes hensilli

82

8

Coconut shells (4), Drink cans (3), Pan (1)Aedes scutoscriptus

65

10Coconut shells (5), Drink can (1), Banana stump (1)Tree hole (1), Plastic containers (2)Aedes sp.

172Well (1), Taro field (1)Culex quinquefasciatus

59

3

Tree hole (1), Concrete puddle (1), Puddle (1)Culex carolinensis

105

7

Coconut shells (4), Drink can (1), Taro fields (2)Culex annulirostris

49

3

Puddle (1), Taro fields (2)＊Habitato types (No. of habitat)

Total number of habitat is 26.

On Piis Island, a total of 377 larvae belonging to six species including one
unidentified species were collected at 26 natural and artificial habitats. They wereidentified as Ae. scutoscriptus, Ae. hensilli， Aedes sp., Cx. quinquefasciatus, Cx. carolinensis
and Cx. annilirostris (Table 3). Among them, Cx. carolinensis was the most predominant
species collected (105 larvae, 7 habitats) followed by Ae. hensilli (82 larvae, 8 habitats).
Discussion
In this survey, a total of 1,761 larvae belonging to nine species including one
unidentified species were collected at 133 natural and artificial habitats. Five Aedes
species were collected and Ae. hesilli was most abundant Aedes species in Weno Island
and Piis Island, and also distributed in Romanom Island. Ae. hesilli is a main vector
of dengue fever in Yap State (SAVAGE et al., 1998; NODA et al., 2005). In Weno Island,Ae. albopictus, which is a one of the major vectors of dengue fever, was also collected.
Therefore, these islands seem to be highly dengue-sensitive areas. The exact houseindex (No. of houses positive for vector species / No. of houses inspected x 100% ) was
not examined in this survey. The house index may be more than 50. Mosquito surveys
were carried out only on three islands of Chuuk lagoon. The mosquito distribution anddensity seem to be the same situation in other islands of Chuuk lagoon.
Aedes species lay eggs in practically all types of man-made containers, and also
in some natural containers. Fig. 2 shows typical habitats for Ae. hensilli. Generally,
the Aedes adults will be found around 50 meters from the breeding sources with amaximum flight distance of around 200 meters. To prevent the outbreak of dengue
fever, environmental management should focus on the destruction, alternation, disposal
or recycling of containers that produce the greater number of adult Aedes mosquitoes.
Weno Island is the main island, and the district center, government offices and75
Mosquitoes collected on Weno Island, Romonum Island and Piis Island, Chuuk State, Federated States of Micronesia (Diptera: Culicidae)

ACE

Ｂ

DFFig. 2 T ypical habitats for Aedes hensilli and Aedes albopictus (A: Coconut shell, B: Drink can, C:
Glass container, D: Plastic container, E. Metal container, F: Tire).

airport are on the northwest side. Many people visit Weno Island from other islands
for work, trade, shopping and other purposes. The northwest side of Weno Island is avery busy place. Fig. 3 shows the lump of the throw-away dust along the main streetof Weno Island. Aedes larvae were often collected from artificial containers of throwaway dust. Unfortunately, the northwest area is highly dengue-sensitive. A patient
infected with the dengue virus will arrive at this site from other states or countries,
and may become the source of outbreak of dengue fever. As there was an outbreakof dengue fever in Palau, Yap and Majuro in 2011, an approach should be employed toreduce the potential for Aedes mosquitoes to breed in this area.

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NODA ShinichiFig. 3 The lump of the thrown-away dust along main street of Weno Island.

Acknowledgments
This work was supported by the Japan Society for the Promotion of Science (ProjectNo. 22510271)
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