By Blake Jackson
Researchers at the University of Kentucky Martin-Gatton College of Agriculture, Food and Environment (CAFE) and the U.S. Department of Agriculture have found that mating changes the chemical coating on New World screwworm flies, according to Jordan Strickler, Agriculture Communications Specialist with the University of Kentucky.
The discovery could improve scientists’ understanding of how these parasitic flies identify mates and may contribute to future monitoring and control strategies.
“New World screwworms are not worms but the larvae of a parasitic fly known as Cochliomyia hominivorax,” said Zain Syed, an Associate Professor in the Department of Entomology who led the study published in the Journal of Medical Entomology.
“Female flies lay their eggs in open wounds or natural body openings of cattle, horses, pets, wildlife and other warm-blooded animals. The larvae then burrow into living tissue and feed, causing painful wounds that can lead to serious infections or death if the infestation is not treated,” Syed added.
The United States eradicated New World screwworm in 1966 using the sterile insect technique, which involved releasing large numbers of sterilized flies. When sterile males mated with wild females, their eggs failed to hatch, eventually reducing wild populations.
The program moved the pest southward through Mexico and Central America, while a sterile-fly barrier in Panama helped prevent its return. A smaller outbreak was also contained in the Florida Keys in 2017.
The parasite has recently reappeared in parts of Central America and Mexico. In June 2026, USDA confirmed a case involving a calf in Zavala County, Texas.
Although the CDC says the current risk to people and animals in the United States remains very low, the outbreak has increased attention on detection and control methods.
Researchers analyzed chemicals called cuticular hydrocarbons that cover adult flies. These waxy compounds help prevent water loss and can also provide information about an insect’s species, sex, age and reproductive status.
“We found that males and females carry many of the same hydrocarbons, but in distinctly different proportions,” Syed said. “Mating further reshaped these chemical profiles, particularly in females.”
The study identified 21 major hydrocarbon signals. While males and females shared the same primary compounds, their proportions differed. Males had greater amounts of shorter-chain hydrocarbons, while females showed higher levels of longer-chain compounds.
Mating caused especially noticeable changes in females, including shifts in several branched hydrocarbons associated with reproductive communication in other insects.
The findings may help explain why female screwworms generally mate only once. Researchers say altered chemical profiles could potentially signal reproductive status and reduce further courtship.
The results could also support future improvements to the sterile insect technique by helping scientists examine mate recognition, reproductive condition, and differences between laboratory and wild fly populations.
“The exciting next step is to determine whether screwworm flies detect these chemical changes and whether they influence subsequent courtship and mating,” Syed said. “That knowledge could eventually contribute to better monitoring and control tools.”
Photo Credit: matt-barton
Categories: Kentucky, Education