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Nature Reflections - May 18, 2006
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Black flies by Jean Griffin "Blackfly,
little blackfly, always a blackfly, no matter where I go. They'll find
the blackfly pickin' my bones, in north Ontar-io-io, in north
Ontar-iooo" - not only in Northern, but also Southern, and in fact,
right across Canada! - and beyond.
Does it help to learn that in
Black
Flies are small, from one to five mm in length, rather squat, with
large, rounded wings and a humpbacked shape. Most common in spring and
early summer, it is, like the mosquitoes, the females that bite. Often
landing and taking off repeatedly without biting, the buzzing presence
and crawling is almost as irritating as the biting. As sundown
approaches the numbers seem to increase, but once darkness arrives the
pests disappear, as they do not attack at night. Unlike mosquitoes,
they seldom attack indoors or in an automobile, as their attention
seems to be diverted to finding an escape route, so they crawl up and
down screens or window panes. After
mating the female Black Flies usually lay their eggs on the water where
they gradually sink. Hatching in a matter of days, the larvae will
produce silk pads securely attached to rocks, and then attach
themselves to these home bases with abdominal hooks. One biologist
describes the larvae that you might see (if you care to look) as "small
black twiglike objects about a quarter of an inch long" attached to a
rock and looking more like plants than insects. Here though bent
downstream by the force of any current, they filter the water for food. Try
brushing one of these larvae off its silken base and it starts to rush
downstream, but suddenly stops even in swift water, and then starts to
move back upstream. What has happened? When dislodged, the larva
immediately spins a silken thread, one end of which is attached to the
silk pad. Once out of ‘harm’s way’, it stops, grasps the thread in its
mouth and by eating the strand of silk ‘reels’ itself back to its home
base, where it resumes feeding. Amazing! The
larval stage is replaced underwater by the pupa, safe in a small
cocoon, still with two feathery gills to extract oxygen from the water
while it changes to the adult. Once metamorphosis is complete, the
pupal case splits open and the adult in a tiny bubble of air rises to
the surface where the bubble bursts and the adult is ejected into the
air and flies away. And so "Blackfly, little blackfly, always a
blackfly, no matter where I go"! Observations: White-crowned Sparrows were seen on May 5 by Sandra Moase in
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