AUGUST
1991

 

 

 

By
Tom Turpin
 
Professor of
Entomology
Purdue University

 

 

 

 

 

8-22-91

COLD-BLOODED INSECTS

When you hear the words “cold-blooded,” what comes to your mind?  Someone who gets cold easily?  Or someone who is unfeeling, uncaring or ruthless?  Of course, some of you more hip readers may think of Paula Abdul's song “Cold-Hearted Snake.”  But most of you probably don't think of insects.

Biologically, humans are not cold-blooded creatures.  We maintain our body temperature near 98.6 degrees Fahrenheit winter or summer.  But not so for snakes, salamanders, frogs, earthworms and insects.  These animals are part of natures "cold-blooded” approach to life.  Their body temperatures are near that of their environment.

Such a lifestyle does have its disadvantages, but insects manage to cope.  Everything happens more quickly in insects as the temperature increases.  They move faster, eat faster and even grow faster.  This means that insects complete their life cycles in less time when the temperature is warm than when it is cool.

When temperatures are too low for activity, some insects rely on the sun for help.  They sunbathe, soaking up a few rays to increase their body temperature.  These insect sunbathers are called baskers.  Like human sunbathers, some insect baskers bathe with their backs in the sun.  These are called dorsal baskers.  Others prefer the rays on their sides – the lateral baskers.

Some other insects increase their body temperature by vibrating their wings.  Moths and bees can frequently be seen with their wings quivering in the cool morning air or in autumn.  Such activity is akin to warming up an aircraft engine prior to flight.  But with the insect, as soon as the body temperature is high enough, it's off into the wild blue yonder.

Honeybees have a sustained flight temperature threshold of about 54 degrees Fahrenheit.  When the air temperature drops below 54 degrees, honeybees may not be able to fly.  It is for that reason that some honeybees will be found away from the hive during the cool evening hours of spring or fall.  These bees leave the hive when temperatures are suitable for flight, but are unable to return when temperatures drop below threshold.  Such is the risk that a cold-blooded insect takes when flying near flight threshold temperatures.

Of course in human terms, if the insect is really cold-blooded, it won't matter anyway.

 

Writer: Tom Turpin
Editor: Olivia Maddox