AUGUST
2002

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

8/08/02

Menacing Mosquitoes are Vamps, Tramps and Scamps

Very few insects are as despised as are mosquitoes.  And for good reason.  They bite!  But there is more to the mosquito problem than the bite.  By transmitting disease organisms, mosquitoes have caused more human suffering than any other group of insects!

So it is easy to see why humankind doesn't love mosquitoes.  And this year with the spread of the West Nile fever most people have become even more aware of the mosquito menace.

How have creatures as small and fragile as mosquitoes wreaked so much havoc on humans?  The fact that they feed on blood is the key.  In addition, as species they're tough.   Mosquitoes have been around for eons and they seem to be everywhere on the earth.

What's with this blood feeding habit anyway?  Blood is necessary for the female mosquito to complete development of her eggs.  So the mosquito that bites is a female.  There are some exceptions to 'only the female bites' rule.  In a few uncommon species the male seeks a blood meal.  Also on rare occasions males of other species, individuals with a sexual identity crisis, also feast on blood. 

These insect vamps practice their skills on many kinds of animals.  If an animal has blood it is fair game for these winged, blood-seeking hypodermic needles.  Birds, mammals, and even snakes and lizards unwillingly donate blood in support of mosquito reproduction.

How does this insect phlebotomist go about her business of blood collection?  She is endowed with the perfect equipment for blood collection.  The mosquito mouths consist of several parts.  There are two tubes, one for sucking up blood the other for delivering a liquid to keep the blood from clotting. Two pairs of sharp knives called stylets surround the tubes.  Stylets are used to cut the skin. 

Once an incision is made, the tips of the mouthparts are inserted.  If a blood vessel has been cut the blood is sucked up.  If not, the mosquito moves the tips of the mouthparts around in the incision trying to hit a vessel.  If a blood vessel is not contacted she will drill another hole.

After the female imbibes enough blood to suit her needs, over two times her own weight, she quietly leaves the blood donor.  She will land on the nearest vertical surface and begin to digest the meal.  The water is removed from the blood and excreted in mosquito urine.  She stores the remaining good stuff in her body.

A bloodthirsty female mosquito discovers her victim based on several clues.  First there is odor.  Mosquito antennae have detectors for carbon dioxide and lactic acid.  We produce both of these chemicals when we breathe.  The many-faceted mosquito eyes are good at detecting movement.  So any motion will help a mosquito find her victim.  Finally with the thoughts of your blood dancing in her head the vamp focuses on the hottest part of your body.  That would likely be a patch of bare skin!

It is the feeding of the mosquito that creates problems for humans.  For many of us the problem is merely some itching that is a direct result of the anticoagulant chemicals injected to prevent blood clotting.

But the biggest concern associated with the bite of a mosquito is not a mere itch.  The real problem is when the mosquito is infected with an organism that can cause disease.  Such things as viruses, bacteria, roundworms and rickettsia can be transported by mosquitoes and injected into humans resulting in a number of diseases.  Mosquitoes carry some well-known diseases including malaria, yellow fever, elephantiasis, and St. Louis encephalitis.

And now the virus that causes West Nile fever has reached our shores.  The virus resides in birds.  It can be transmitted to humans by a mosquito that has taken a blood meal from an infected bird.  While the risk of acquiring West Nile virus is very low, the presence of the virus in an area means that we should reduce mosquito bites as much as possible.  After all that mosquito vamp threatening to sample your blood might have acquired her previous meal from some infected bird down the road!

 

Writer: Tom Turpin
Editor: Olivia Maddox