queensland museum learning
Student task sheet
Mangrove Challenge
Raising wrigglers
If you live in a coastal area of Queensland, you may
have a problem with mosquitoes every summer. But
by understanding their life cycle, and how it can be
interrupted, you can develop some strategies to control
mosquito numbers.
What you do:
Mosquito eggs will hatch one or two days after they are
laid on the water surface. In a few more days the larvae
or wrigglers can be seen, and easily taken from the
water using a net.
In this activity you can ‘raise’ mosquito eggs and larvae,
then experiment to find out how to stop them developing.
This activity works best in the warmer months.
Fill a bucket(s) with water.
Leave in a shady place.
Background activity:
>> Male and female mosquitoes have different ways
of life and adaptations. Find out about these
differences.
>> Three species of mosquitoes are considered pest
species in Queensland: Aedes vigilax, Culex
annulirostris and Aedes notoscriptus. Find out if
any species are considered pests in your area. Do
they transmit diseases? How serious are these
diseases to human or animal health?
Leave for one week.
Use a net or strainer to harvest.
Growing larvae
Observe with a hand lens
or low power objecttive lens
of a microscope.
Care: You should consider all mosquitoes
dangerous. Avoid being bitten.
What you need (for a class):
>> buckets or containers to hold water
>> pond water, rain water or tap water, shaken and
left to stand overnight to remove chlorine
>> handfuls of dried gum leaves added to tap water
to provide organic matter for wrigglers
>> aquarium net or strainer
You can increase the number of wrigglers or eggs,
if you:
>> use black or dark-coloured buckets
>> put strips of filter or blotting paper on the inside of
the bucket at water level to provide a surface for
egg laying
>> leave the eggs for 8–10 days in a plastic bag, then
flood with water — they hatch overnight.
About wrigglers
The wrigglers of Aedes vigilax are shown here. Their heads
are down as they breathe through a siphon — an extension of
the last abdominal segment — at the water’s surface. They
move or ‘wriggle’ by contracting and relaxing their segmented
bodies. The wrigglers of the Anopheles mosquito, which carries
the fatal disease malaria, lack a siphon; instead they hold their
bodies horizontally along the surface and take air through holes
in their abdomens.
QIMR
queensland museum | po box 3300 | south brisbane bc | queensland 4101 | australia
© Queensland Museum 2007
Raising wrigglers:
Experiments with eggs or wrigglers
In this commercial mosquito breeder, larvae can develop
in pond water. After a short while, they pupate, or form
a pupa or case. Pupae breathe at the surface and do
not feed, in two or three days, adult mosquitoes will
emerge from this case. They can be observed in the
top part of the breeder. DO NOT ALLOW THESE
MOSQUITOES TO ESCAPE. To kill the adults, place
the breeder in the freezer for about half an hour, then
wash with warm water and detergent.
Typically, within two weeks of hatching, wrigglers will
moult four times, and then pupate. If you want to
experiment with wrigglers, you need to harvest them
as soon as they can be seen.
In this activity you will investigate factors that affect
wriggler survival or egg laying, to determine ways to
control breeding. To do this, you will need to plan your
experiment as a Controlled experiment; see Science
Skills.
The following variables may affect mosquito breeding
and development:
>> surface chemicals such as kerosene or detergent
>> temperature
>> water movement
>> vegetation cover
>> depth
>> other treatments such as salt.
Research the effects of these variables on mosquito
breeding. A useful source of information can be found
at: <http://medent.usyd.edu.au/>. One of these variables,
or one of your own, could be manipulated in your
investigation.
Evaluation:
Make your own mosquito breeder:
You can make this mosquito breeder from two one-litre
soft drink bottles. First form the sides of the breeder.
To do this, cut the neck off both bottles using scissors,
then the base off one of the bottles. Next, attach one
of the bottle necks with sticky tape inside the breeder
sides, as shown. Then cut four slits in the side of the
bottom breeder with scissors, and force the parts
together. Finally, cover the top with a circle of muslin
or voile, using a rubber band.
1. A well-designed and implemented investigation
improves the validity of your results. Your
investigation should have a control so that you can
tell if a variable has affected either wriggler
development or egg laying. How can you tell if a
factor has affected the development of the wrigglers?
How do you gauge the success of the treatments?
2. Comment on the effectiveness of factors that appear
to affect wriggler development. Do any of them
cause environmental problems?
3. Visit a local wetland area, and observe potential
mosquito-breeding sites.
4. Contact your local council to find out what mosquito
sprays are being used in your local area. Investigate
the effects on the environment of widely used
insecticides such as the organophosphorus-based
temephos.
Write a report on your findings.
queensland museum | po box 3300 | south brisbane bc | queensland 4101 | australia
© Queensland Museum 2007
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