Control with Arthropods - Biological and Environmental Control of Disease Vectors - page 18

meals during the evenings and at night, so their
control can be achieved in much the same way
as that of Anopheles adults. Their larvae have
dif erent habitat preferences and are most often
found in organically polluted water sources like
sewers, drains and pit latrines.
Arthropod predators of Anopheles and Culex
larvae mainly come from three orders:
Hemiptera (true bugs), Coleoptera (beetles) and
Odonata (dragonfl ies and damselfl ies). Within
these orders, many families are predacious. Lists
and examples of the families and genera of
mosquito larval predators can be found in
several reviews (Jenkins, 1964; Legner, 1995;
Mogi, 2007; Quiroz-Martinez and Rodriguez-
Castro, 2007; Shaalan and Canyon, 2009).
Aquatic predators usually exist in stable
ecosystems in more permanent aquatic habitats
(Munga et al ., 2007). Even though mosquitoes
have evolved specifi c behaviours to avoid
predation, such as diving (Futami et al ., 2008)
and oviposition in non-predator-containing
water (Blaustein et al ., 2005), arthropod
predators can play important roles in the natural
control of disease vectors. A study looking at the
ability of An . gambiae M and S forms to develop
and survive in dif erent larval habitats in
Burkina Faso found that emergence success of
adult mosquitoes was over three times higher
when the larvae developed in cages without
predators (Diabate et al ., 2008). Likewise, Culex
numbers can be greatly reduced by natural
predators in the fi eld. In the Philippines, the
emergence rate of Culex in the presence of
predators was just 1.8%, whereas excluding
predators increased this rate to 88.8% (Mogi et
al ., 1984). In addition, passive detection of
predator abundance and diversity has shown
that for various Anopheles species (Service,
1977; Urabe et al ., 1986; Carlson et al ., 2009)
and Cx . quinquefasciatus (Garcia Avila et al .,
1996), population numbers decrease with
increasing predator abundance and predator
numbers.
Several studies outline the predation
ei cacy of various dif erent Anopheles and Culex
predators. The predation ei cacy of three wild-
caught African arthropod predators, namely
backswimmers, belostomatids and dragonfl y
nymphs, on An . gambiae larvae were tested in
laboratory and semi-fi eld conditions. Third
instar larvae were most ei ciently preyed on by

all three predator types (Kweka et al ., 2011). Of
the three arthropod types, backswimmers were
the most ei cient arthropod, causing a 74%
reduction in larval survival and a 97% reduction
in pupation rates in semi-fi eld conditions.
Dragonfl y nymphs caused 60% and 80%
reductions in larval survival and pupation,
respectively; belostomatids caused 39% and
43% reductions in larval survival and pupation
rates, respectively (Kweka et al ., 2011). Not only
are backswimmers ei cient An . gambiae
predators, but they are also one of the most
abundant predators in ecosystems (Diabate et
al ., 2008; Carlson et al ., 2009). It has been
suggested that these notonectids would be good
biological control agents for mosquito larvae
(Lacey and Orr, 1994) because they prefer to
feed on mosquito larvae as opposed to other
aquatic fauna (Mogi, 2007). They should be
especially ef ective against Anopheles larvae
because they occupy the same area in the water
column (Quiroz-Martinez and Rodriguez-Castro,
2007). In addition to aquatic predators, the
shore fl y Ochthera chalybescens preys on all
instars of An . gambiae larvae by fi shing them out
with their sickle-shaped front legs, and has even
been found to prey on adults (Minakawa et al .,
2007). Under laboratory conditions, shore fl ies
consumed an average of 9.8-18.8 An . gambiae
larvae and fi ve An . gambiae pupae daily
(Minakawa et al ., 2007). One benefi t of this
predator is that, being an adult fl y, it is not
limited to the aquatic habitat in which it is
found. Therefore, it readily disperses to smaller
water bodies that may not be stable enough to
sustain an ecosystem with aquatic predators,
but that are frequently found to contain malaria
vector larvae (Service, 1977).
As with Anopheles , there have been several
studies looking at the susceptibility of Culex
mosquitoes to arthropod biological control
agents. In the laboratory, the water beetle Acilius
sulcatus consumed an average of 34 Cx .
quinquefasciatus larvae per day (Chandra et al .,
2008), while under similar conditions the water
bug Laccotrephes griseus ate between 21 and 51
Cx . quinquefasciatus larvae per day (Ghosh and
Chandra, 2011). Anisops sp. (backswimmer)
and Diplonychus sp. (water bugs) are also ef ective
Culex predators under laboratory conditions
(Shaalan et al ., 2007). The predatory capacity of
A . sulcatus was tested to control wild Culex