Reproduced from Wing Beats of the AMCA,
the official publication of the Florida Mosquito Control Association.
Please use the following citation when referring to this article:
Jones, C. and E. Schreiber. 1994. The
carnivores, Toxorhynchites. Wing Beats, Vol. 5(4):4.
The Carnivores, Toxorhynchites
DR. CARL JONES and DR. ERIC SCHREIBER
Importance
Predatory mosquitoes in the genus
Toxorhynchites are the most common arthropods which have been used
for control of "container-breeding" mosquitoes. The combination of
carnivorous larvae and innocuous adults is very attractive in biological
control. Successful biological control has been reported using
Toxorhynchites species from Japan, Southeast Asia, the Caribbean and
the United States.
Geographic Distribution
Most of the 71 species of
Toxorhynchites are found in forested tropical regions throughout the
world. At least one, Toxorhynchites rutilus, has a
subspecies (septentrionalis) that is found as far north as 40
degrees N latitude in Connecticut and southern New York. The other
subspecies of Toxorhynchites rutilus found in mainland United
States, Tr. rutilus, has been reported only from Florida, Georgia
and Louisiana. Although successful introduction of Southeast Asian
species has occurred in Hawaii, continual introduction of exotic species
at sites in the southern U.S. has not resulted in their establishment.
Description
Toxorhynchites are unusually large
mosquitoes; the wingspan may exceed 12 mm; the body length may exceed 7
mm. Adults are frequently covered with iridescent scales and the
proboscis has a pronounced 90 degree downward curve. Larvae are
generally dark brown or reddish in appearance, with very conspicuous
hairs on the abdomen. The head capsule is quite thick and contains
powerful mandibles. Fourth instar larvae may be more than 2 cm in
length.
Adult Behavior
Adults feed on plant nectars, which most
species require for egg development. A few species are precocious and do
not need nectar to initiate oviposition. Protein used in reproduction is
apparently entirely derived from larval feeding, although some nectars
may provide modest amounts of some amino acids. Cumbersome in flight,
they are most frequently seen resting near treeholes or engaging in
their characteristic elliptical oviposition flight patterns at the mouth
of natural and man-made containers. They are not known to oviposit in
small ponds or other open water such as ground pools.
Larval Behavior
Larvae feed on the living
macroinvertebrates inhabiting flooded treeholes, bromeliads and man-made
containers. They are dependent on movement for prey location. Although
they are more successful in feeding on mosquitoes, eating as many as 400
larvae during their larval development periods, they can successfully
complete larval development with artificial protein sources such as
water fleas (Daphnia) or brine shrimp. Cannibalism is not
uncommon, especially in small containers, but containers such as tires
with ample food supplies may support half a dozen or more similarly
sized larvae. Larval behavior is especially intriguing with feeding
dependent on prey size and availability. Wanton killing of prey without
feeding has been reported.
Seasonality
All known species are multivoltine. In
the United States, Toxorhynchites generally overwinter as late
larval instars. Diapause is controlled by day length, rather than
temperature.
IPM
Although the use of Toxorhynchites
alone is unlikely to reduce pest or vector species below operational
thresholds, they can be a valuable tool in areas where containers and
treeholes contribute substantially to the standing crop of mosquitoes.
However, they are highly susceptible to insecticides, and care has to be
exercised in the timing of release of Toxorhynchites and
application of insecticide sprays. Their large size and docile
appearance create the opportunity for them to serve as focal points for
public awareness campaigns aimed at the cleanup of man-made containers
that are used as breeding sites by pest mosquitoes.
Dr. Carl Jones is with the College of
Veterinary Medicine, Department of Veterinary Pathobiology at the
University of Illinois In Urbana-Champaign, Illinois.
Dr. Eric Schreiber is with the John A.
Mulrennan, Sr. Research Laboratory at Florida A&M University in Panama
City, Florida.
This webpage was begun on 7
July 1996 and last updated on 1 June
2010
