Blow flies are a group of iridescent green or blue flies belonging to the family Calliphoridae. Flies undergo complete metamorphosis, transitioning through egg-larva(maggot)-pupa-adult. Often in this situation, the larvae and adults occur in different environments and feed on different food sources. In fact, blow fly larvae are carrion feeders, meaning they feed on the decaying flesh of dead animals. Because of this, blow flies are important decomposers in nature and can also provide useful information to forensic entomologists. Adult blow flies often seek nectar resources from flowers and, subsequently, can act as pollinators. Therefore, blow flies can positively impact the yield of flowering crops!
The presence of blow fly adults has been linked to increased fruit set and quality for small fruit crops like blueberries and strawberries. They have also been shown to be efficient pollinators for carrots and leeks for seed production purposes. Because flies, in general, are active across a wider range of climatic conditions (e.g., temperature, precipitation, altitude, etc.) compared to bees, they make ideal pollinators for crops grown in protected culture, including greenhouses and high tunnels. They can tolerate the high temperatures that occur in these structures. In fact, our team at Purdue sees many blow flies pollinating in the high tunnels we visit across the state of Indiana!
Blow flies get a bad rap for the unsavory conditions in which the larvae live and feed, but these insects contribute to pollination services in some of the more unfavorable environments for bees, and therefore, we are especially interested in understanding their contributions to pollination in high tunnels. If you happen to see some blow flies visiting your crops this growing season, let them be. They’re working for you!
Figure 1. Blow fly visiting Brassica flowers in a high tunnel on an Indiana farm (Photo by Robert Grosdidier).