you have been seeing small flies or gnats in your kitchen or supermarket, especially around the fruit and vegetable areas, they're probably
fruit flies. Fruit flies are a problem all the year round, especially now that we have super markets and centrally heated homes both of which allow the fly to breed at full stretch
melons, squash, grapes and other perishable items brought in from the
garden are often the cause of an infestation developing indoors. Fruit
flies are also attracted to rotting bananas, potatoes, onions and other
unrefrigerated produce purchased at the grocery store.
flies are common in homes, restaurants, supermarkets and wherever else
food is allowed to rot and ferment. Adults are about 1/8 inch long and
usually have red eyes. The front portion of the body is tan and the rear
portion is black.
the female has been located by smell, sound or sight, she may turn out
to be coy and despite all the males efforts she will need to be wooed.
This is not because she is fussy, the courtship ritual ensures that the
male belongs to the right species and the right sex. Paradoxically, some
of the most complex rituals seem to have been evolved by the least charismatic
of insects. The fruit fly female will only make up her mind once she and
her prospective mate have gone through a preliminary dance. It begins
with the male approaching her and drumming on her head with his front
feet. This then releases the next stage of the dance where they shuffle
from side to side whilst facing one another. Finally, the male feels confident
enough to spread out his wings and twist their leading edge downwards,
a simple flourish that seems to be full of meaning to her because she
now allows him to mount her.
flies lay their eggs near the surface of fermenting foods or other moist,
organic materials. Upon emerging, the tiny larvae continue to feed near
the surface of the fermenting mass. This surface-feeding characteristic
of the larvae is significant in that damaged or over-ripened portions
of fruits and vegetables can be cut away without having to discard the
remainder for fear of retaining any developing larvae. The reproductive
potential of fruit flies is enormous; given the opportunity, they will
lay about 500 eggs. The entire lifecycle from egg to adult can be completed
in about a week.
Fruit flies are especially attracted to ripened fruits and vegetables
in the kitchen. But they also will breed in drains, garbage disposals,
empty bottles and cans, trash containers, mops and cleaning rags. All
that is needed for development is a moist film of fermenting material.
Infestations can originate from over-ripened fruits or vegetables that
were previously infested and brought into the home. The adults can also
fly in from outside through inadequately screened windows and doors.
Fruit flies are primarily nuisance pests. However, they also have the
potential to contaminate food with bacteria and other disease-producing
best way to avoid problems with fruit flies is to eliminate sources of
attraction. Produce which has ripened should be eaten, discarded or refrigerated.
Damaged portions of fruits and vegetables should be cut away
and discarded in the event that eggs or larvae are present in the wounded
area. A single rotting potato or tomatoe forgotten at the back of a display,
or fruit juice spillage under a refrigerator can breed thousands of fruit
flies. So can a recycling bin stored in the basement which is never emptied
or cleaned. So we can see straight away that the best cure, as always, of treating problems such as this housekeeping on a regular basis. Housekeeping in these sorts of areas needs to be accountable, hence, some sort of checklist should be made available for the person who is assigned the job to fill out and to sign,then there is no excuse.
People who can their own fruits and vegetables, or make wine, cider or
beer should ensure that the containers are well sealed; otherwise, fruit
flies will lay their eggs under the lid and the tiny larvae will enter
the container upon hatching. Windows and doors should be equipped with
tight-fitting (16 mesh) screens to help prevent adult fruit flies from
entering from outdoors.
a structure is infested with fruit flies, all potential breeding areas
must be located and eliminated. Unless the breeding sites are removed
or cleaned, the problem will continue no matter how often insecticides
are applied to control the adults. Finding the source(s) of attraction
and breeding can be very challenging and often will require much thought
and persistence. Potential breeding sites which are inaccessible (e.g.,
rubbish disposals and drains) can be inspected by taping a clear plastic
food storage bag over the opening overnight. If flies are breeding in
these areas, the adults will emerge and be caught in the bag.
the source of attraction and breeding is eliminated, a pyrethrum-based,
aerosol insecticide may be used to kill any remaining adult flies in the
Also these days there are bait stations which are quite inocuous and can actually be placed in say a display of produce even in a supermarket
is it and why bother about it? Drosophila
melanogaster is a fruit fly, a little insect about 3mm long, of the kind
that accumulates around spoiled fruit. It is also one of the most valuable
of organisms in biological research, particularly in genetics and developmental
biology. Drosophila has been used as a model organism for research for
almost a century, and today, several thousand scientists are working on
many different aspects of the fruit fly. Its importance for human health
was recognised by the award of the Nobel prize in medicine/physiology
to Ed Lewis, Christiane Nusslein-Volhard and Eric Wieschaus in 1995.
Why work with Drosophila?
Part of the reason
people work on it is historical - so much is already known about it that
it is easy to handle and well-understood - and part of it is practical:
it's a small animal, with a short life cycle of just two weeks, and is
cheap and easy to keep large numbers. Mutant flies, with defects in any
of several thousand genes are available, and a project is now underway
to sequence the entire Drosophila genome.
cycle of Drosophila: The
drosophila egg is about half a millimeter long. It takes about one day
after fertilisation for the embryo to develop and hatch into a worm-like
larva. The larva eats and grows continuously, moulting one day, two days,
and four days after hatching (first, second and third instars). After
two days as a third instar larva, it moults one more time to form an immobile
pupa. Over the next four days, the body is completely remodelled to give
the adult winged form, which then hatches from the pupal case and is fertile
after another day. (timing is for 25°C; at 18°, development takes twice
on Drosophila: Drosophila
is so popular, it would be almost impossible to list the number of things
that are being done with it. Originally, it was mostly used in genetics,
for instance to discover that genes were related to proteins and to study
the rules of genetic inheritance. More recently, it is used mostly in
developmental biology, looking to see how a complex organism arises from
a relatively simple fertilised egg. Embryonic development is where most
of the attention is concentrated, but there is also a great deal of interest
in how various adult structures develop in the pupa, mostly focused on
the development of the compound eye, but also on the wings, legs and other
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