–by Anthony Zukoff–Southwest Research & Extension Center
March Flies (Bibio sp.) have begun emerging in large numbers in some areas of southwest Kansas. The synchronous nature of adult emergence in spring draws attention and concern as thousands of adults can show up almost overnight on structures and in cropland. These congregations of small (~6 mm), large-eyed flies are mating swarms and generally will be short lived as adults survive only a few days to a week. Another name for these flies is “Lovebug” since males and females will attach themselves at the end of their abdomens and remain like that at all times even while flying. After mating, females will excavate a small chamber in the soil, lay eggs and then die in the same chamber. Just as the adults congregate, so do the larvae. Dense pockets of hundreds of larvae can sometimes be unearthed. These larvae generally are detritivores, feeding on dead vegetation and other organic matter in the upper portion of the soil. However, some species are known to feed on living plant roots and are considered pests of various cereal, forage and vegetable crops. In 1891, entomologist Vernon L. Kellogg wrote of a new Bibionid fly emerging in large numbers in many wheat fields of seven western Kansas counties during the last week of April.
The large swarms of flies concerned farmers, but no evidence of damage by the flies was ever detected despite a large number of larvae being found in the soil weeks previous to adult emergence. Kellogg stated that the adults disappeared “suddenly and simultaneously”. Despite a large number of flies being detected in wheat and alfalfa this year, no unusual damage to these crops has been noted and the mating swarms should vanish in the coming week.
