Wasps that found the most nutritious bait were hottest. "If they encounter a very high-protein source, such as pure chicken meat, their thoracic temperatures are dramatically higher than when they encounter a poor food source," Eckles said. "You can see their wings quivering after they take a chunk of meat. While they cut it into a nice little aerodynamic ball, they're vibrating their flight muscles to generate heat."
When offered a plate of pulverized chicken, the wasps raised the temperature of their thoraxes a mean of 1.7 degrees Celsius (3.1 degrees Fahrenheit) compared to foragers who were kept from the bait by a mesh dome. Chicken mixed with an equal volume of nutritionless cellulose got a cooler response, an elevation of just 1.1 degrees Celsius (2.0 degrees Fahrenheit), and the wasps tarried longer possibly looking for a better source of food. Eckles, Wilson and Nieh, along with associate professor of biology David Holway report online (http://www-biology.ucsd.edu/labs/nieh/papers/Eckles_et_al_2008.pdf).
In a separate experiment Nieh and students Katherine Mapalad and Daniel Leu established colonies of bumble bees (Bombus impatiens) in a cool room at UCSD where they offered the insects pure pollen or pollen that had been cut to 75, 50 or 25 percent by weight with indigestible cellulose.
Using a thermal imager, the researchers measured the temperatures of 94 foraging bees just after they collected pollen and again later, right after the bees returned to the nest.
The more protein, the hotter the
|Contact: Susan Brown|
University of California - San Diego