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Upside-down flies, dogs’ cold noses, heavy flavors

Q: How can I prove that houseflies can fly upside down? Matt, Joplin, Missouri

Greenbottle fly [Leon Higley, Entomology Department, University of Nebraska-Lincoln]

A: This may be difficult.

"Houseflies cannot fly upside down..." says the Science Museum of Minnesota.

They can, however, land upside down by doing a quick "pitch up", says Michael Dickinson, bioengineering professor at California Institute of Technology. Flying right side up, feet dangling, a fly nears a ceiling. She sticks her front two feet out and grabs on. Then she swings her back four legs up like a trapeze artist and sticks them on the ceiling. She grips the surface, ready for a 6-legged stroll, upside down, of course.

Flies have two short strong wings and a huge middle section packed with wing muscles. Three groups of tiny gyroscopes and sense organs placed at right angles to one another tell a fly his speed, his rate of turn, and whether he’s being blow off course.

Dickinson tests flies in the lab with a flyswatter-like device. " The flies jump so quickly to evade the swatter that they temporarily lose control and flip head-over-heels." Then they quickly jump back upright as their sophisticated gyros kick in.

Fruit flies can turn 90 degrees in 50-thousands of a second. That’s ten times faster than the human eye blinks.

Many flies can hover like a hummingbird, spin about their axis like a bullet, zip through spaces little wider than their wingspan, land on ceilings, and even fly backwards. But, they don’t fly upside down.

Further Surfing:

North Carolina State University: Insect wings by John Meyer

Caltech: New insight into how flies fly by Michael Dickinson

Hooper Virtual Paleontological Museum: How insects fly

Dogs’ cold noses

Q: Why are dogs’ noses always cold? Jon, Albuquerque, New Mexico

Wet and cold (for now). [Stiv, DogNose Heaven]

A: We’ve sure felt them — cold and wet pressed against us — but dogs’ noses are not always cold, even when they’re well. A dog’s nose changes through the day: wet and cool one moment and warmer and drier the next. The nose wetness (or lack thereof) also changes with the humidity. The nose norm varies from dog to dog.

A dog’s nose, though, tends to be cool and moist just as the inside of a human’s nose.

"A dog has special glands inside his nose that secrete a watery fluid to keep the inside of the nose moist and to help cool the dog through evaporation," says Holly R. Frisby, veterinarian at Drs. Foster & Smith, Inc. This moisture can extend to the outside of the nose, making it shiny, wet, and cold.

Also, they continually lick their noses.

Further Surfing:

PetEducation.com: Dogs

Dognose Heaven: dog nose photos

Heavy flavors

Q: Is there a weight to flavour? Some smells and tastes are stronger than others. Does that mean that they are heavier? Kent, Winnipeg, Manitoba Canada

Lemon flavor, an organic molecule sensed by “sour” receptors in the back of the roof of the mouth and the soft palate. [© 1995-2004 by Michael W. Davidson and The Florida State University. All Rights Reserved. Used with permission.]

A: We taste four basic qualities: salty, sour, bitter, and sweet (and their combinations). You are right — some taste intensities actually depend on the weight of the molecules that we taste. Bitter, for example.

Bitter. The heavier the molecular weight of an inorganic salt, the more bitter it tastes.

Salty. Salt’s another one that depends on molecular weight but in a funny kind of way. Salts of low molecular weight taste salty. Heavier molecular weights, however, taste bitter. In man, ammonium is most salty, then in decreasing order: potassium, calcium, sodium, lithium, and magnesium (least salty). The order, however, is different for many other animals.

Sweet. The sweet taste seems to depend on the spatial arrangement of the molecules. Slight changes within a sweet molecule will make it bitter or tasteless.

Sour. Hydrogen ions make acids taste sour. The higher the concentration, the sourer the acid tastes.

Further Surfing:

Florida State University: The flavor collection by Michael Davidson

(Answered Feb. 13, 2004)