OCTOBER
2013

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

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Check out these books by Tom Turpin:

Flies in the face of fashion

What's Buggin You Now?

 

 

 

10-24-13

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Mosquito Lookalikes


Editor's note: On Six Legs columnist Tom Turpin has been named a 2013 Special Boilermaker Award winner, for his service to thousands of students, parents, teachers, community members and friends of Purdue.

Cranefly
Crane fly on corn leaf

(photo credit: photos by John Obermeyer/Purdue Entomology)

Many people claim that the mosquito is the most dangerous type of insect - in fact, animal - in the world. Why? Because of the number of people who die as the result of mosquito bites, that's why.

It is not the actual bite of the mosquito that is so dangerous. They are dangerous because some species of mosquitoes are what scientists call disease vectors. These insects transport disease-causing microorganisms from one animal to another.

Several human diseases can develop as a result of mosquito bites, including three that are caused by organisms transmitted only by mosquitoes. These three diseases are malaria, which is caused by a protozoan, and yellow fever and dengue, which are both caused by viruses. Mosquitoes can also transmit nematodes that cause filarial parasitic diseases in humans. Mosquitoes are also the vectors of viruses that cause several encephalitis diseases of humans, including West Nile.

The American Mosquito Control Association states that more than 1 million people die worldwide each year as a result of mosquito-borne diseases. It has been stated that mosquitoes have been responsible for more human deaths throughout history than all the wars ever fought.

Our fight with these two-winged purveyors of human misery and death continues unabated to the present time. Even the Bill and Melinda Gates Foundation has joined the war on mosquitoes, awarding $2 billion in grants to help with the problem.

So how does such a small insect - most are between 3-6 mm in body length - become the most dangerous animal on the earth? Well, one of the primary reasons is that the insect needs to take a blood meal for egg development. That means it can transmit pathogens from person to person as the female feeds. In addition, mosquito populations can reach high numbers over a short period of time; that guarantees a lot of humans get bitten.

The general disdain humans have for mosquitoes means some insects that resemble mosquitoes sometimes get falsely accused as being one of those hated bloodsuckers. Midges are one such group of insects; like mosquitoes, they spend their larval life in water. Midges look so much like mosquitoes that many entomologists even describe them in terms such as "long-legged, mosquito-like insects." These mosquito lookalikes, though, differ from mosquitoes in one very important way - most do not seek a blood meal and, therefore, do not bite humans! However, populations of midges can get high enough to be a nuisance. Midges can be especially annoying because they have the habit of flying around a person's face and even getting into eyes.

Another type of insect that is a mosquito lookalike is a crane fly. Some of the most common of the crane flies belong to the insect family Tipulidae. These crane flies have been described as overgrown mosquitoes. Indeed, some reach an inch or more in length - about four times the size of the average mosquito.

Crane flies have very long legs that are easily broken off. That is not something most of us worry about as we swat what appears to be a giant mosquito. But it is a problem for entomology students or 4-H members trying to collect and pin a crane fly for their collections. An insect without six legs is not something they want to include in their collection if an "A" grade or a blue ribbon is the goal!

Crane fly larvae
Crane fly larvae

Crane fly larvae are aquatic or semiaquatic and are often called leatherjackets. That is because the larvae have a tough, leathery larval skin. Most crane fly larvae feed on decaying plant matter. A few feed on living plant tissue and on rare occasions have been shown to damage cultivated plants.

The food habits of most adult crane flies are poorly understood. It has been reported that some species feed on flowers. What we do know is that crane fly adults do not bite humans. So the next time you spy a "humongous mosquito," a term used by a person describing to me what turned out to be a crane fly, just relax. It is not going to try to extract an ounce or two of blood for its next meal.

 

 

Writer: Tom Turpin
Editor: Olivia Maddox