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Mosquito control at the 4 instar.
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Mosquito pupa
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Biting insect biology
Insect
development is characterized by either complete (holometabolous)
or incomplete (hemimetabolous) metamorphosis. Dipterans
are two winged insects and include mosquitoes and black
flies. Their development is holometabolous and is characterized
by 4 major stages: egg, larva, pupa and imago (adult).
Immature mosquitoes and black flies (eggs, larvae and
pupae) are present aquatically. After hatching from eggs,
larvae develop through a succession of moults (shedding
of exoskeleton), each instar increasing in size. Mosquito
larval development comprises 4 instars, while that of
black flies has 7-9, depending on the species.
The development
period varies according to each species and several
environmental variables such as water temperature and food
availability. The process can take from a few days to a
few months. At their final stage, mosquitoes transform
into mobile pupae, while black flies remain in a stable
and protective silken cocoon. Both insects' pupae are non-feeding,
and as a result biological treatments must be applied before
pupation. Metamorphosis is usually completed in a few
days, at which time adults emerge as flying insects. Mosquito
Mosquito
season in Canada extends from spring thaw, through
the summer months to the first frost of autumn. They
can be found everywhere and anytime, under favourable
conditions. 75 species of mosquitoes have been recorded
in Canada , emerging at different times and multivoltine
species can produce several generations per year.
Black flies
Black flies are the most dreaded biting
insects in Canada. Populations explode in summer months;
their numbers peak in May and June. They attack with such
ferocity that outdoor activities are practically inhibited
during the day. They are also known to be more active and
feed more often just before sunset. Black flies appear
at the beginning of May in southern Quebec , coinciding
with leaf blossoming (especially maple). They usually occur
throughout summer and some species may persist into autumn.
They are present from May to September in more northern
climates such as in the Boreal Forest. In Canada , black
flies are more diverse than mosquitoes, with 100 described
species. Black fly larvae develop in all running waters,
from tiny brooks to large rivers.
| Life cycle of Culex
pipiens |
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Clockwise from top:
Adult female; floating egg raft; larva
breathing, suspended by the apex of the siphon at
the water surface; pupa floating with respiratory
trumpets above water surface; emerging adult (source:
Agriculture and Agri-Food Canada, GRECO). |
Mosquito
life cycle Source: Centre Agriculture Canada, greco
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| Life cycle of Black flies |
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Clockwise from top:
Adult female; Eggs deposited on vegetation;
Larvae anchored to the bottom, searching for food
with their labial brushes; Pupae attached to submerged
vegetation; Adults emerge enveloped by a gaseous
bubble and float to the surface. (source: Agriculture
and Agri-Food Canada , GRECO) |
Black fly life cycle.
Source: Centre Agriculture Canada, greco |
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