Science Update

Dye + Sun = Dead Fruit Flies

ARS researchers are expanding tests of SureDye, a commercial blend of red and yellow dye. In preliminary tests, Mediterranean and Mexican fruit flies that ate SureDye were dead soon after they were exposed to light. Scientists want to know if SureDye might be an alternative to malathion. The insecticide is used to eradicate fruit fly outbreaks on the U.S. mainland. It's also used to control fruit fly damage to Hawaiian crops. The two dyes—D&C Red No. 28 and D&C Yellow No. 8—are registered by the Food and Drug Administration for use in cosmetics and medicines. The red dye is thought to convert light energy to a form that destroys an insect's gut tract. The yellow dye is a synergist that increases the red dye's activity. SureDye is a product of PhotoDye International, Inc., Linthicum, Maryland.

Robert Mangan, USDA-ARS Crop Quality and Fruit Insects Research Unit, Weslaco, Texas, phone (956) 447-6316; USDA-ARS Tropical Fruit and Vegetable Research Laboratory, Hilo, Hawaii, phone (808) 959-4300.

Chickens Leaner With Amino Acid in Feed

Chickens turned out 5 to 10 percent leaner when fed an amino acid with their regular diet. Scientists with ARS and the University of Maryland-Eastern Shore seek to patent this use of N-methyl aspartic acid (NMA). A modified form of the amino acid aspartate, NMA tells the body to secrete more growth hormone. The hormone promotes the manufacture of protein, but it strains fat production. With NMA, the birds also used feed more efficiently.

John P. McMurtry, USDA-ARS Animal and Natural Resources Institute, Beltsville, Maryland, phone (301) 504-8803; USDA-ARS Animal Physiology Research Unit, Athens, Georgia, phone (706) 583-0855; Mark J. Estienne, University of Maryland-Eastern Shore, Princess Anne, Maryland, phone (410) 651-2200.

Aging Limits "Bounceback" from Weight Gain or Loss

A 3-month study of 35 healthy men supplied perhaps the first direct evidence that aging impairs one's ability to control food intake after overeating or undereating. This has health implications, since people tend to accumulate too much fat in middle age and lose too much muscle and bone later in life. Half the study volunteers were in their sixties and seventies; half were in their twenties. First, scientists figured out how many calories each man would need to maintain his weight. Then, for 3 weeks, they overfed half of each age group by 1,000 calories a day. They underfed the other half by about 700 calories. After a 7-week followup, the young men had returned to their starting weights. But not the older men: Those who'd been overfed weighed an average 3.5 pounds more than at the outset, and those underfed had not recouped all their weight loss.

Susan B. Roberts, USDA-ARS Jean Mayer Human Nutrition Research Center on Aging at Tufts University, Boston, Massachusetts, phone (617) 556-3238.

A Brazilian fly makes fire ants literally lose their heads. ARS scientists hope to import it for tests in the United States, where fire ants lack natural enemies. They feed on crops and sting people and animals in 11 states. Beheading a live host—a rarity among parasitic flies—is standard procedure for Pseudacteon flies. And they attack only fire ants. The female deposits an egg on or in a fire ant's body. Weeks later, a maggot has moved through the unlucky ant's neck into its head—and eaten the contents. The head falls off after an enzyme—made by ant or maggot (scientists don't know which)—dissolves its connecting tissue.

Sanford Porter, USDA-ARS Medical and Veterinary Entomology Research Laboratory, Gainesville, Florida; phone (904) 374-5914

"Science Update" was published in the February 1995 issue of Agricultural Research magazine.