INTRODUCTION
Mosquito populations are limited by predation, but
the intensity of predation and its significance should
vary greatly among habitat types. Larval habitats of
mosquitoes are diverse. At one extreme, small
containers that hold water such as tree holes, bamboo
stumps, plant pitchers, etc. are the typical larval habitats
of some groups. At the other extreme, edges of lakes
and ponds also can be colonized by certain kinds of
mosquitoes. In general, it is considered that predation
regulates mosquitoes in pool-type habitats whereas
container mosquitoes are limited by resource rather
than predation (Mogi 1981, Washburn 1995). Many
kinds of predators have been reported from pool habitats
(Bay 1967, Service 1973, 1977, Collins and Washino
1985) while small containers often lack predators,
although some predators such as Toxorhynchites larvae
have specialized to these habitats (Focks 1985).
The small size of container habitats may be an
important characteristic that determines community
structure of mosquitoes and other aquatic insects
including predators. Washburn (1995) referred to
MacArthur and Wilson’s (1968) island biogeography
theory as an explanation of poorer species richness in
containers than in pools. Even within a narrower range,
metazoan diversity is positively correlated with capacity
of tree holes and bamboo stumps (Sota 1996). It is
expected that the significance of predation in mosquito
populations depends on the habitat size.
Extensive studies have been carried out for
container mosquitoes from phytotelmata such as tree
holes, bamboo stumps, pitcher plants (see Frank and
Lounibos 1983), and artificial containers (Mori and
Wada 1970, Sota et al. 1994). However, most of the
previous studies on container mosquitoes treated
habitats of various sizes over small ranges. Differences
in regulatory factors of mosquitoes between container
type and pool-type habitats suggested the importance
of habitat size in relation to mosquito larvae and
June, 2002
predators (Washburn 1995). However, the effect of
habitat size can not be evaluated from such a
comparison, because containers and pools are different
from each other not only in habitat size but also in other
factors such as surrounding environments and
complexity. This paper focuses on the area of water
bodies in containers as a factor influencing mosquito
communities and aquatic predators by describing
occurrence patterns of mosquitoes and predaceous
insects in various sizes of containers that are scattered
in a rural area of Saga, southwestern Japan. As
occurrence patterns of mosquitoes and predators might
also be influenced by the surrounding environment, we
classified environment type for each container. In
addition, seasonal fluctuation in the availability of pooltype
habitats may influence the habitat use patterns of
aquatic insects in containers. A large part of the study
area is used for cultivating rice from June to September,
therefore our survey was done during both periods when
rice fields were and were not filled with water.