CHAMPAIGN, Ill. -- With the goal of improving the natural
biological control of flies, scientists have scoured Illinois
feedlots. After three years of study, they say that two
parasitic wasps known as Spalangia endius and Spalangia
nigoraenea are especially important in the Midwest and actually
could emerge as weapons. Such is the finding of a study of
parasites that feed on stable and house flies in Illinois. Both
types of flies are well-known pests. Stable flies feed on the
blood of cattle, annoy other livestock and adversely affect
production, and, like house flies, are a public health problem
among humans. Researchers from the University of Illinois
collected fly pupae from manure, spilled feed, along fence
lines, near water sources and waste piles of straw and hay at
feedlots. The scientists then looked for the presence of either
emerging flies or the parasites that kill them. The predominant
parasites that kill flies are tiny wasps. As in the movie
"Alien," the wasps lay their eggs inside a host, in thi